A quasi-static model for NiMnGa magnetic shape memory alloy (MSMA) is formulated in parallel to the Brinson and Tanaka thermal SMA constitutive models. Since the shape memory effect (SME) and pseudoelasticity exist in both NiTi and NiMnGa, constitutive models for SMAs can serve as a basis for MSMA behavioral modeling. The quasi-static model for NiMnGa was characterized by nine material parameters identified by conducting a series of uniaxial compression tests in a constant field environment. These model parameters include free strain, Young’s modulus, fundamental critical stresses, fundamental threshold fields, and stress-influence coefficients. The Young’s moduli of the material in both its field and stress preferred configurations were determined to be 450 MPa and 820 MPa respectively, while the free strain was measured to be 5.8%. These test data were used to assemble a critical stress profile that is useful for determining model parameters and for understanding the dependence of critical stresses on magnetic fields. Once implemented, the analytical model shows good correlation with test data for all modes of NiMnGa quasi-static behavior, capturing both the magnetic shape memory effect and pseudoelasticity. Furthermore, the model is also capable of predicting partial pseudoelasticity, minor hysteretic loops and stress-strain behaviors. To correct for the effects of magnetic saturation, a series of stress influence functions were developed from the critical stress profile. Although requiring further refinement, the model’s results are encouraging, indicating that the model is a useful analytical tool for predicting NiMnGa actuator behavior.

This paper presents the actuation performance of a conducting shape memory polyurethane (CSMPU) actuator. We introduced a concept of shape memory polyurethane activated by electric power in 2004, while conventional shape memory polyurethanes are activated by external heat source. A conducting shape memory polyurethane actuator was manufactured by adding carbon nano-tube to conventional shape memory polyurethane. The main problem of the previous CSMPU was bad dispersion of carbon nano-tubes in polyurethane. In this paper, we have tried to find manufacturing method to solve the dispersion problem. With a lot of elaborative works, we have developed conducting shape memory polyurethane actuator with good electrical performance. The actuation performance of the developed conducting shape memory polyurethane actuator was measured and assessed.

The development of a novel piezoelectric induced-strain actuator possessing an innovative internal amplifying structure is presented in this paper. This actuator basically consists of a metal frame and two lead zirconate titanate (PZT) piezoelectric ceramic patches. The metal frame is bent to form an open trapezoid, where its center part has a specially designed saddle-like unit and its slanting legs are attached with PZT patches. The saddle-like unit has an amplifying-lever mechanism at the corners to increase the displacement output of the whole actuator even its legs are mechanically clamped. When an electric field is applied across the thickness of the PZT patches, the patches induce deformations on the whole actuator through the piezoelectric d₃₁ effect. The saddle-like unit can relax the constraints at the joints between the unit and the legs by stretching itself during bending. Piezoelectric finite element analysis is used to maximize the work output of displacement and blocked force of the actuator under different geometric parameters. The results are in good agreement with those obtained from quasi-static measurements, showing that the actuator has work output comparable to and larger than the existing induced-strain actuators (e.g., THUNDER) under fixed mounting conditions. Therefore, the actuator has great potential for use in various practical smart structures and integrated systems, including active-passive vibration isolation and micro-positioning.

This paper gives a summary on advanced piezocomposite transducers and the perspective of their applications in the field of smart structures, health monitoring and diagnostics. At present, three different low profile piezocomposite actuator types are commercially available. The designs are arising from the R&D work at MIT in the years 1991/92 funded by the US Department of Defence. Smart Material is manufacturing Macro Fiber Composites (MFC), licensed by NASA in a full-scale production. A new MFC- design using the 3-1 coupling has been developed, recently. It allows for the reduction of drive voltage down to 360 V. Fraunhofer IKTS focused its development on custom shape composites making use of PZT tubes and plates. New actuator devices for active interfaces have been introduced for the first time. All piezocomposite design forms show different performance data, which are summarised in the present paper to provide design engineers with necessary informations in view of intended applications.

This paper presents a study in which clamped unimorph piezoelectric diaphragms are tested to determine the importance of the pattern of the electrodes that supply the driving charge to the actuator. In previous work, it has been shown that such a diaphragm, when used as an energy harvesting device, can generate a much increased charge in response to an applied pressure when the electrode has a “regrouped” pattern. Regrouping refers to the process of segmenting the electrodes into regions that are electrically disconnected and then reconnecting those regions such that some have reversed polarity. The circular diaphragm actuator studied in this paper works somewhat the opposite of an energy harvester. That is, applied charge is used to generate diaphragm deflection as opposed to applied pressure generating charge. Four unimorph diaphragm actuators, with different electrode patterns, were tested in this work. According to analytical and experimental results, it is shown that a factor of seven increase in diaphragm deflection can be obtained with regrouping.

This paper promotes the general paradigm that a composite’s internal structure can be micro-tailored to achieve a multifunctional physical response through the use of the Field Aided Micro Tailoring (FAiMTa) technique. The FAiMTa technique relies on curing a polymer composite while in its liquid state in the presence of an electric field. The particles within the composite align themselves in the direction of the electric field and create an orthotropic composite structure. This technology can lead to composite materials having a micro-tailored structure mimicking biological systems. As an initial step towards this goal, uniformly orthotropic composites, which are prepared by the FAiMTa technique, are mechanically characterized. Two epoxy based systems are considered: a composite having micro-sized graphite particles whereas the other has micro-sized aluminum particles. Mechanical tests show the change of material properties according to direction of the particle alignment within the composite. Optical microscopy also confirms the created orthotropic microstructure. The next step in development of FAiMTa technique is the reduction of stress concentration near a geometric discontinuity by properly orienting particulate structures within the composite. Our on-going efforts toward optimization of the composites are briefly outlined.

Functionally Graded Piezoceramics (FGP) increase actuator lifetime and provide complex deformations; however, to reap these benefits sophisticated grading and fabrication techniques beyond the conventional layered bonding techniques are required. This paper introduces the Dual Electro/Piezo Property (DEPP) gradient technique via MicroFabrication through CoeXtrusion (MFCX). The Dual Electro/Piezo Property (DEPP) grading technique pairs a high displacement lead zirconate titanate (PZT) piezoceramic with a high permittivity barium titanate (BT) dielectric. These compatible materials act synergistically to form dramatic gradients in permittivity across the structure, concentrating the electric field in the more piezoelectrically active region leading to electrically-efficient, large-displacement actuators; with the benefit of increased reliability stemming from the continuous gradients and monolithic nature of the ceramic. The DEPP variation was first evaluated independently of the MFCX process through fabrication and experimental characterization of a powder pressed bimorph. While simple one-dimensionally graded FGPs can be realized by this process, MFCX is needed for any complex, multidimensional gradient. The MFCX process was adapted for DEPP grading and demonstrated by creating a more complex linearly-graded FGP. Both the bimorph and linearly graded specimens had good material quality and generated high displacements correlating well with published FGP theory; with the linear gradient reducing internal stress levels, extending actuator lifetime. This paper presents a general FGP methodology that couples grading and fabrication to generate high yield, low cost monolithic actuators with complicated one-dimensional gradients. Extension of this research will pave the way for more complicated gradients yielding such deformation capabilities as warping, twisting, rippling, and dimpling.

This paper presents results of ongoing research on a multifunctional actuation system wherein the strength-giving members of a small, planar, lightweight space structure also enable actuation for purposes such as shape control and steering. The configuration currently being studied includes a circular membrane with a circumferential waveguide/conductor, which also serves as a stiffener. The waveguide is end-excited by a ceramic piezoelectric microactuator. The goal of this research is to investigate the dynamic response characteristics of this system. In this paper, a theoretical model for the overall dynamics is outlined, and a few general results are presented. Experimental results aimed at studying the transient response and steady-state response characteristics of the system (and obtained using an optical profiler with dynamic measurement capability) are also included. Potential configuration changes to improve the transient and steady-state response are discussed.

Pedestrian fatalities from automobile accidents often occur as a result of head injuries suffered from impacts with an automobile front end. Active pedestrian protection systems with proper pedestrian recognition algorithms can protect pedestrians from such head trauma. An investigation was conducted to assess the feasibility of using a network of piezoelectric sensors mounted on the front bumper beam of an automobile to discriminate between impacts with “pedestrian” and “non-pedestrian” objects. This information would be used to activate a safety device (e.g., external airbag or pop-up hood) to provide protection for the vulnerable pedestrian. An analytical foundation for the object-bumper impact problem will be presented, as well as the classical beam impact theory. The mechanical waves that propagate in the structure from an external impact contain a wealth of information about the specifics of a particular impact -- object mass, size, impact speed, etc. -- but most notably the object stiffness, which identifies the impacted object. Using the frequency content of the sensor signals, it can be shown that impacts with a “pedestrian” object of varying size, weight, and speed can be easily differentiated from impacts with other “non-pedestrian” objects. Simulation results will illustrate this phenomenon, and experimental tests will verify the results. A comprehensive series of impact tests were performed for validation, using both a stationary front bumper with a drop-pendulum impactor and a moving car with stationary impact objects. Results from both tests will be presented.

A tactile display is programmable device whose controlled surface is intended to be investigated by human touch. It has a great number of potential applications in the field of virtual reality and elsewhere. In this research, a 5x5 touch sensitive tactile display array including electrorheological (ER) fluid has been developed and investigated. Experimental results show that the sensed surface information could be controlled effectively by adjusting the voltage activation pattern imposed on the tactels. In the meantime, it is possible to sense the touching force normal to the display’s surface by monitoring the change of current passing through the ER fluid. These encouraging results are helpful for constructing a new type of tactile display based on ER fluid which can act as both sensor and actuator at the same time.

There has been a growing need to develop non-contact sensors for use in real time structural health monitoring. Iron-Gallium alloys (Galfenol, Fe_1-xGa_x, 0.13< x <0.21) appear to be a promising magnetostrictive material for such applications. This work discusses the concepts and methods used in developing a prototype Galfenol sensor for detecting bending induced strains and forces. The proof of concept experiment consists of two Galfenol patches attached on the top and bottom surfaces of an aluminum cantilevered beam. A solenoid applies a biasing magnetic field to the Galfenol patches. The change in Galfenol patch magnetic induction produced by compressive and tensile stresses during bending are continuously measured by a field sensor. The strains on the beam surface and Galfenol sensor surface are also measured using strain gages. The effect of biasing field at constant loading and the effect of loading at constant biasing field on the magnetic induction response have been investigated. A linear magneto-mechanical model for estimating the magnetic induction response for a given mechanical loading is presented.

This paper presents a prototype micro-gyro sensor design that employs the new magnetostrictive alloy GalFeNOL for transduction of Coriolis induced forces into an electrical output. The concept takes advantage of the principles employed in vibratory gyro sensors and the ductile attributes of GalFeNOL to target high sensitivity and shock tolerance in a miniature gyro sensor. In this study, preliminary test results are presented as concept verification with a meso-scale tuning fork vibratory gyro sensor.

Galfenol alloys (_Fe100-x Ga_x) have been shown to combine significant magnetostriction (~400 ppm) with strong mechanical properties (tensile strengths ~500 MPa), making them well suited for use in robust actuators and sensors as an active structural material. This project investigates the magnetomechanical bending behavior of Galfenol to facilitate the design concepts for using Galfenol in a variety of novel sensor applications. To this end, a series of experiments are conducted on the magnetic response of cantilevered beams to dynamic bending loads. The samples studied include polycrystalline Fe_81.6Ga_18.4 and Fe_80.5Ga_19.5 (1/8” diameter x 2” long) and single crystal Fe₈₄Ga₁₆ and Fe₇₉Ga₂₁ (1/16” diameter x 1” long). Mechanical excitation was applied to the tip of each rod, with tests performed with sinusoidal and broadband random inputs. Measuring the magnetic response of the samples were a giant magnetoresistive (GMR) sensor located behind the beam and a pickup coil wound directly on each rod. A combination of permanent magnets and solenoid provided dc fields to magnetically bias the samples. Results of initial testing show that sinusoidal bending produces measurable output in which the GMR sensor agrees well with the pickup coil, and that the output increases when subjected to increased magnetic bias. Random input tests confirm that the various system resonances can be detected from the frequency spectra. Other results examine the effects of composition, crystal structure, and z-axis position of the GMR sensor. The system is modeled by incorporating classical continuum mechanics, the constitutive magnetostriction equations, and nonlinear magnetization terms, the results of which are compared with the experiments.

In this paper, a novel method to make MR dampers self-sensing based on the electromagnetic induction and the working principle of an electromagnetic integrated relative displacement sensor (IRDS) integrated into a commercial available MR damper are presented. The IRDS mainly comprises an exciting coil wound on the piston head and an induction coil wound on the nonmagnetic cylinder, which is covered by a cylindrical cover made from the materials with high magnetic permeability. In this way, a novel relative displacement self-sensing MR damper (SSMRD) comprising an IRDS and an MR damper is developed. In order to validate and optimize the performance of the IRDS and the SSMRD, the modeling and analyzing with the finite element mathod based on ANSYS are carried out and the simulation results are presented.

Geosynthetic materials have found useful applications when unbound aggregates have been placed on cohesive soil with very weak subgrade. They have also been successfully used in retarding reflective cracking in both flexible and composite pavements. There are many applications of geosynthetics in pavement engineering yet there is considerable lack of understanding in the behavior of the material. Geosynthetic materials exhibit very peculiar properties in the area of tensile strength and reinforcement. MEMS are miniature sensing or actuating devices that can interact with other environments (provided no adverse reaction occurs) to either obtain information or alter it. With remote query capability, it appears such devices can be embedded in pavement systems as testing and monitoring tools. The aim of this paper is to propose both field and laboratory methods for monitoring geotextile performance using MEMS.

In this paper, we present our recent progress in LIPCA (Lightweight Piezo-Composite Actuator) application for actuation of flapping wing device. The flapping device uses linkage system that can amplify the actuation displacement of LIPCA. The feathering mechanism is also designed and implemented such that the wing can rotate during flapping. The natural flapping-frequency of the device was 9 Hz, where the maximum flapping angle was reached. The flapping test under 4 Hz to 15 Hz flapping frequency was performed to investigate the flapping performance by measuring the produced lift and thrust. Maximum lift and thrust produced when the flapping device was actuated near the natural flapping-frequency.

This paper describes a new method for drag elimination and stall suppression via tangential synthetic jet actuators. This boundary layer control (BLC) method is shown to perform as well as continuous and normal synthetic jet BLC methods but without fouling difficulties, system-level complexity or extreme sensitivity to Reynolds number. Classical laminated plate theory (CLPT) models of the piezoelectric actuators were used to estimate diaphragm deflections and volume per stroke. A 12” (30.5cm) chord, 6” (15.3cm) span NACA 0012 profile wing section was designed with three unimorph 10 mil (254μm) thick, 3.25” (8.23cm) square piezoelectric diaphragm plenums and five 1 mil (25μm) thick stainless steel valves spaced from 15%c to the trailing edge of the airfoil. Static bench testing showed good correlation between CLPT and experiment. Plenum volume per stroke ranged up to 5cc at 500 V/mm field strength. Dynamic testing showed resonance peaks near 270 Hz, leading to flux rates of more than 60 cu in/s (1 l/s) through the dynamic valves. Wind tunnel testing was conducted at speeds up through 13.1 ft/s (4 m/s) showing more than doubling of C_lmax. At low angles of attack and high flux rates, the airfoil produced net thrust for less than 4.1W of electrical power consumption.

The study of acoustic noise generated by helicopter main rotors is the object of many theoretical and experimental investigations because of the complexity of the related physical phenomena and its strong influence on the vehicle performance. One of the main targets of the FriendCopter European Project is to define technical solutions aimed at improving the helicopter acoustic performance. In this work some related activities are described. The extremely complex operating environment of a helicopter rotor contributes to noise generation through several distinct mechanisms: among them, blade vortex interaction noise (BVI) results extremely annoying when it occurs. One method for BVI alleviation is to increase the separation of the tip vortex from the rotor plane using an adaptive blade tip (anhedral configuration) to diffuse the tip vortex or to displace it. In this work, as a first step of the investigation, a feasibility study on blade tip morphing will be addressed, neglecting any aeroacoustic estimation; a specific flight condition will be considered to evaluate the efficiency of a particular smart system based on the coupled action of shape memory alloys (SMAs) and magneto-rheological fluids (MRFs). Such a kind of actuation system has to realise an on-off mechanism through which the tip blade displacement is maximised: the properties of the MR fluid will be exploited to selectively reduce the bending stiffness spanwise so that the SMA actuation is increased. A theoretical model and numerical investigations will be shown to evaluate the reliability and the effectiveness of the integrated system.

Individual blade control (IBC) as well as higher harmonic control (HHC) for helicopter rotors promises to be a method to increase flight performance and to reduce vibration and noise. For those controls, an additional twist actuation of the rotor blade is needed. The developed concept comprises the implementation of distributed piezoelectric actuation into the rotor blade skin. In order to maximize the twist within given constraints, as torsional rigidity and given actuator design, the concept takes advantage of an orthotropic rotor blade skin. That way, a combination of shear actuation with orthotropic coupling generates more twist than each one of these effects alone. Previous approaches with distributed actuation used actuators operating in +/-45° direction with quasi-isotropic composites. A FE-Model of the blade was developed and validated using a simplified demonstrator. The objective of this study was to identify the effects of various geometric and material parameters to optimize the active twist performance of the blades. The whole development was embedded in an iterative process followed by an objective assessment. For this purpose a detailed structural model on the basis of the BO105 model rotor blade was developed, to predict the performance with respect to rotor dynamics, stability, aerodynamics and acoustics. Rotor dynamic simulations provided an initial overview of the active twist rotor performance. In comparison to the BO105 baseline rotor a noise reduction of 3 dB was predicted for an active twist of 0.8° at the blade tip. Additionally, a power reduction of 2.3% at 87m/s based on a 2.5 to BO105 was computed. A demonstrator blade with a rotor radius of 2m has been designed and manufactured. This blade will be tested to prove, that the calculated maximum twist can also be achieved under centrifugal loads.

This paper introduces a morphing aircraft concept whose purpose is to demonstrate a new bio-inspired flight capability: perching. Perching is a maneuver that utilizes primarily aerodynamics -- as opposed to thrust generation -- to achieve a vertical or short landing. The flight vehicle that will accomplish this is described herein with particular emphasis on its addition levels of actuation beyond the traditional aircraft control surfaces. A computer model of the aircraft is developed in order to predict the changes in applied aerodynamic loads as it morphs and transitions through different flight regimes. The analysis of this model is outlined, including a lifting-line-based analytical technique and a trim and stability analysis. These analytical methods -- compared to panel or computational fluid dynamics (CFD) methods -- are considered desirable for the analysis of a large number of vehicle configurations and flight conditions. The longitudinal dynamics of this aircraft are studied, and several interesting results are presented. Of special interest are the changes in vehicle dynamics as the aircraft morphs from a cruise configuration to initiate the perching maneuver. Changes in trim conditions and stability are examined as functions of vehicle geometry. The time response to changes in vehicle configuration is also presented.

This paper addresses a flutter boundary prediction of a smart wing during the process of adaptation in which airplane's safety will easily be endangered. A smart morphing airplane will be more flexible functionally and mechanically than a conventional airplane with a fixed structural configuration. During the process of structural morphing or adaptation, airplane's structure needs to become very flexible, so that the airplane is anticipated to encounter instability in a new manner due to an on-going structural change. Here we will show that the new discrete-time series approach for aeroelastic instability prediction which we proposed for the fixed-wing is useful in predicting the flutter boundary of an adaptive wing, too. A numerical analysis is performed using a two-dimensional wing model in which the structural adaptation changes its natural frequencies and consequently influences its aeroelastic stability although flying at a fixed speed.

A basic eigenvector orientation approach has been used to evaluate the possibility of controlling the onset of panel flutter using a flat panel (wide beam) as an illustrative example. The onset of flutter can be defined as the instance when two modes coalesce. Since eigenvectors for two consecutive modes are usually orthogonal, an indication of the onset of flutter condition can be observed earlier when they start to lose their orthogonality. Using eigenvector orientation method for the prediction of the flutter boundary (indicated by a gradual loss of orthogonality between two eigenvectors) was developed in a previous study and thus can provide a 'lead time' for possible flutter control. In this study, a basic simple beam element is used to model the panel (wide beam). As a first step, piezoelectric layers are assumed to be bonded on the top and bottom surface of the panel to provide counter-bending moments at joints between elements. The standard linear quadratic control theory is used for controller design and full state feedback is considered for simplicity. The controllers are designed to modify the system stiffness matrix in such a way to re-stabilize the system at the onset of flutter; as a result, flutter occurrence is offset to higher flutter speed. Controllers based on different control objectives are considered and the effects of control moment locations are studied as well. Potential applications of this basic method can be straightforwardly applied to plates and shells of laminated composites using finite element method.

In this paper, we present design, manufacturing, and wind tunnel test for a small-scale expandable morphing wing. The wing is separated into inner and outer wings as a typical bird wing. The part from leading edge of the wing chord is made of carbon composite strip and balsa. The remaining part is covered with curved thin carbon fiber composite mimicking wing feathers. The expandable wing is driven by a small DC motor, reduction gear, and fiber reinforced composite linkages. Rotation of the motor is switched to push-pull linear motion by a screw and the linear motion of the screw is transferred to linkages to create wing expansion and folding motions. The wing can change its aspect ratio from 4.7 to 8.5 in about 2 seconds and the speed can be controlled. Two LIPCAs (Lightweight Piezo-Composite Actuators) are attached under the inner wing section and activated on the expanded wing state to modify camber of the wing. In the wind tunnel test, change of lift, drag, and pitching moment during wing expansion have been investigated for various angles of attack. The LIPCA activation has created significant additional lift.

As more alternative, lightweight actuators have become available, the conventional fixed-wing configuration seen on modern aircraft is under investigation for efficiency on a broad scale. If an aircraft could be designed with multiple functional equilibria of drastically varying aerodynamic parameters, one craft capable of 'morphing' its shape could be used to replace two or three designed with particular intentions. One proposed shape for large-scale (geometry change on the same order of magnitude as wingspan) morphing is the Hyper-Elliptical Cambered Span (HECS) wing, designed at NASA Langley to be implemented on an unmanned aerial vehicle (UAV). Proposed mechanisms to accomplish the spanwise curvature (in the y-z plane of the craft) that allow near-continuous bending of the wing are narrowed to a tendon-based DC motor actuated system, and a shape memory alloy-based (SMA) mechanism. At Cornell, simulations and wind tunnel experiments assess the validity of the HECS wing as a potential shape for a blended-wing body craft with the potential to effectively serve the needs of two conventional UAVs, and analyze the energetics of actuation associated with a morphing maneuver accomplished with both a DC motor and SMA wire.

A novel type of morphing structure capable of a large change in shape with a small energy input is discussed in this paper. The considered structures consist of two curved shells that are joined in a specific manner to form a bistable airfoil-like structure. The two stable shapes have a difference in axial twist, and the structure may be transformed between the stable shapes by a simple snap-through action. The benefit of a bistable structure of this type is that, if the stable shapes are operational shapes, power is needed only to transform the structure from one shape to another. The discussed structures could be used in aerodynamic applications such as morphing wings, or as aerodynamic control surfaces. The investigation discussed in this paper considers both experiment and finite-element analysis. Several graphite-epoxy composite and one steel device were created as proof-of-concept models. To demonstrate active control of these structures, piezocomposite actuators were applied to one of the composite structures and used to transform the structure between stable shapes. The analysis was used to compare the predicted shapes with the experimental shapes, and to study how changes to the geometric input values affected the shape and operational characteristics of the structures. The predicted shapes showed excellent agreement with the experimental shapes, and the results of the parametric study suggest that the shapes and the snap-through characteristics can be easily tailored to meet specific needs.

Tensegrity structures have become of engineering interest in recent years, but very few have found practical use. This lack of integration is attributed to the lack of a well formulated design procedure. In this paper, a preliminary procedure is presented for developing morphing tensegrity structures that include actuating elements. To do this, the virtual work method has been modified to allow for individual actuation of struts and cables. A generalized connectivity matrix for a cantilever beam constructed from either a single 4-strut cell or multiple 4-strut cells has been developed. Global deflections resulting from actuation of specific elements have been calculated. Furthermore, the force density method is expanded to include a necessary upper bound condition such that a physically feasible structure can be designed. Finally, the importance of relative force density values on the overall shape of a structure comprising of multiple unit cells is discussed.

There is currently a need for compact actuators capable of producing large deflections, large forces, and broad frequency bandwidth. In all existing active materials, large force and broadband responses are obtained at small displacements and methods for transmitting very short transducer element motion to large deformations need to be developed. This paper addresses the development of a hybrid actuator which provides virtually unlimited deflections and large forces through magnetorheological (MR) flow control and rectification of the resonant mechanical vibrations produced by a magnetostrictive Terfenol-D pump. The device is a compact, self-contained unit which is capable of producing large work output. To achieve large output force, hydraulic advantage is created by implementing a driven piston diameter that is larger than the drive piston. Since the pump operates at high speeds, a fast-acting MR fluid valve is required. The paper presents a four-port MR fluid valve in which the fluid controls its own flow while carrying the full actuator load. A multi-domain model of the device was developed with the primary goal of analyzing and demonstrating the MR fluid valve concept. A research valve was designed, constructed, and tested for purposes of model parameter identification and validation, and analysis of device behavior. Deflections of over 6 in are demonstrated with the device presented here.

In recent years, there have been growing applications of active materials, such as piezoelectrics and magnetostrictives, as actuators in the aerospace and automotive fields. Although these materials have high force and large bandwidth capabilities, their use has been limited due to their small stroke. The use of hydraulic amplification in conjunction with motion rectification is an effective way to overcome this problem and to develop a high force, large stroke actuator. In the hydraulic hybrid actuator concept, a hydraulic pump actuated by an active material is coupled to a conventional hydraulic cylinder, from which output work can be extracted. This actuation concept requires a high bandwidth active material with a moderate stroke. Both piezoelectrics, and magnetostrictives such as Terfenol-D and Galfenol are well suited as driving elements for this application, however, each material has its drawbacks. This paper presents a comparison of the performance of a piezoelectric, Terfenol-D and Galfenol element as the driving material in a hydraulic hybrid actuator. The performance of the actuator with each driving element is measured through systematic testing and the driving elements are compared based on input power required and actuator mass. For a pumping chamber of diameter 1” and a driving element of length 2”, the maximum output power was measured to be 2.5 W for the Terfenol-D hybrid actuator and 1.75 W for the piezoelectric hybrid actuator.

This paper presents an experimental analysis in which a THUNDER (Thin Unimorph DrivER) actuator was used to adjust the flow of air through a specified cross sectional area inside a Plexiglas housing. The THUNDER is a curved, bilayer actuator made up of a piezoelectric layer and a stainless steel layer. In this work the THUNDER is used as the prime mover in an air flow control valve. The valve is made up of a flow channel that allows air to pass over the top of the actuator. When voltage is applied to the actuator, the piezoceramic layer expands or contracts, changing the actuator’s curvature, thus changing the orifice area in the valve resulting in a change in flow. Testing is done with single and dual flow loop arrangements. In the dual flow loop, one flow line contains the control valve while the other is a bypass line. The valve is used to balance flow between the lines. Both lines have adjustable outlet valves so that the valve can be tested under a wide range of flow conditions. Several lids for the control valve were manufactured and tested to reveal the possibility of increase modulation performance using alternative channel geometries. The test results showed that the THUNDER control valve could modulate the air flow by as much as 16% at 4.4 SCFM (125 LPM) in single loop flow and 30% at 2.3 SCFM (65 LPM) in dual loop flow for inlet pressures up to 25 PSI (172 kPa).

Flexibility and speed of response are two key requirements in the design of machinery for high-speed manufacturing operations. These two requirements are often conflicting and their resolution requires considerable ingenuity on the part of the designer. A novel actuator based upon the use of twin electro-rheological (ER) clutches is described together with its modification to control the motion (angular displacement, angular velocity) of a robot manipulator arm. The development of a new experimental facility involving the robot manipulator arm is described. In the basic twin ER clutch facility, the motion of a toothed belt is controlled by manipulating the electric field applied to each ER clutch. The belt, in turn, controls the angular position and velocity of the robot arm. The use of twin clutches allows motion to be imparted in opposite directions without the need for return springs or similar mechanisms. To improve the positional performance an ER brake is added to the robot arm mechanism. The extension to the dynamic model for the ER clutch mechanism to incorporate the robot arm and ER brake is outlined and is validated experimentally. The displacement response of the robot arm is then examined as a trend study using different motor driving speeds. The positional accuracy of the robot arm and its repeatability is then demonstrated.

Rock and soil penetration by coring, drilling or abrading is of great importance for a large number of space and earth applications. An Ultrasonic/Sonic Drill/Corer (USDC) has been developed as an adaptable tool for many of these applications [Bar-Cohen et al, 2001]. The USDC uses a novel drive mechanism to transform the ultrasonic or sonic vibrations of the tip of a horn into a sonic hammering of a drill bit through an intermediate free-flying mass. As the pace of adapting the USDC to various applications has increased, it has become more critical to develop an efficient simulation tool to predict the performance of various designs. A series of computer programs that model the function and performance of the USDC device were previously developed and tested against experimental data [Bao et al, 2003]. The combination of these programs into an integrated modeling package and the analysis of simulated results will be described in this paper.

Periodic cellular configurations with negative Poisson's ratio have attracted the attention of several researchers because of their superior dynamic characteristics. Among the geometries featuring a negative Poisson's ratio, the chiral topology possesses a geometric complexity that guarantees unique deformed configurations when excited at one of its natural frequencies. Specifically, localized deformations have been observed even at relatively low excitation frequencies. This is of particular importance as resonance can be exploited to minimize the power required for the appearance of localized deformations, thus giving practicality to the concept. The particular nature of these deformed configurations and the authority provided by the chiral geometry, suggest the application of the proposed structural configuration for the design of innovative lifting bodies, such as helicopter rotor blades or airplane wings. The dynamic characteristics of chiral structures are here investigated through a numerical model and experimental investigations. The numerical formulation uses dynamic shape functions to accurately describe the behavior of the considered structural assembly over a wide frequency range. The model is used to predict frequency response functions, and to investigate the occurrence of localized deformations. Experimental tests are also performed to demonstrate the accuracy of the model and to illustrate the peculiarities of the behavior of the considered chiral structures.

In this paper, a model-based approach for fault detection and vibration control of flexible structures is proposed and applied to 3D-structures. Faults like cracks or impacts acting on a flexible structure are considered as unknown inputs acting on the structure. The Proportional-Integral-Observer (PI-Observer) is used to estimate the system states as well as unknown inputs acting on a system. Also the effects of structural changes are understood as external effects (related to the unchanged structure) and are considered as fictitious external forces or moments. The paper deals with the design of the PI-Observer for practical applications when measurement noise and model uncertainties are present and shows its performance in experimental results. As examples, impacts acting upon a one side clamped elastic beam and on a thin plate structure are estimated using displacement or strain measurements. To control the vibration of the flexible plate, two piezoelectric patches bonded on the structure are used as actuators. The control algorithm introduced in this contribution contains a state feedback control and additionally a disturbance rejection. The disturbances are estimated using the PI-Observer. Experimental results show the performance and the robustness properties of the control strategy for the vibration control of a very thin plate.

This paper reports multimodal vibration control of a flexible beam structure with piezoceramic actuators and sensors using the loop shaping method. These piezoceramic patch actuators and sensors are surface-bonded on the flexible beam. The non-parametric identification of the flexible beam structure is carried out using the Schroeder wave. The identified open loop model is then used for loop shaping based on the extended sensitivity charts. A loop shaping compensator is designed to achieve multimodal vibration suppression. Numerical results showed a reduction of 8 decibels for first mode, 12-14 decibels for second and third mode, respectively. Experimental results closely match the simulation results. Furthermore, the results of loop shaping method are compared with those of the methods of LQR (Linear Quadratic Regulator) and pole-placement control, which are designed using state space models. Comparisons show that the loop shaping method requires less control effort while maintaining the effectiveness in vibration suppression.

This work presents an experimental study of fuzzy logic control for a quarter-car-model of a high-mobility multi-purpose wheeled vehicle suspension system using a magneto-rheological fluid damper. Sprung mass displacement and velocity based fuzzy control, and acceleration based fuzzy control are proposed and compared to a skyhook control strategy. The displacement and acceleration of the sprung mass under rough road excitation are analyzed using power spectral density and root mean square methods. It is demonstrated that the displacement and acceleration based fuzzy control strategy performs well as compared to the other method considered.

This work presents the feasibility of the piezoelectric shunt damping for vibration suppression of the rotating HDD disk-spindle system. A target vibration mode which significantly restricts the recording density increment of the drive is determined through modal analysis and a piezoelectric bimorph is designed to suppress unwanted vibration. The shunt circuit is constructed by considering two-dimensional electromechanical coupling coefficient of the shunted drive. In addition, optimal design process using sensitivity analysis is undertaken in order to improve the shunt damping of the system. The effectiveness of the proposed methodology is verified through experimental implementation by observing the displacement transmissibility of the system in frequency domain.

Vibration control has been a subject of engineering research for the past few decades. Recently, the use of smart material-related components for vibration control has become an alternative to traditional vibration control techniques. Vibration control using such components has many advantages such as lighter overall weight and lower cost. They are especially suitable where traditional techniques cannot be applied due to weight and size restrictions. Passive vibration shunt control using piezoelectric ceramics (PZT) and an electrical network has been studied by many researchers both analytically and experimentally. In this paper, the modeling of a passive vibration shunt control on a cantilever beam using a finite element analysis software package -- ANSYS is presented. It is a useful alternative to an experimental approach that is costly as the PZT is useable only once in most instances. The simulation shows that the electrical shunt circuit can remove considerable vibration-based energy when properly tuned. The simulation reveals that the material property of the structure has a significant impact on the effectiveness of the vibration shunt circuit. This is postulated to be because of the mechanical impedance match between the structure and PZT transducer. The method provides a useful mechanism for selecting the material properties of a structure so that its vibration can be effectively absorbed by a piezoelectric vibration shunt network. Also shown in this paper is experimental verification of the computational results. This procedure has the potential for greatly increasing the flexibility in the design of such Mechatronic control devices especially when the mechanical and physical properties of synthetic materials such as polymeric composite materials can be varied to suit the application.

Adaptive or intelligent structures which have the capability for sensing and responding to their environment promise a novel approach to satisfying the stringent performance requirements of future space missions. This research focuses on a finite element analysis active vibration suppression of an intelligent composite platform that is designed for thrust vector control of a satellite thruster and has simultaneous precision positioning and vibration suppression capabilities. This smart platform connects the thruster to the structure of the satellite and has three active struts and one active central support with one piezoelectric stack in each. A finite element harmonic analysis was employed to develop a vibration suppression scheme, which was then used to study the vibration control of the satellite structure using the vibration suppression capabilities of the intelligent platform mounted on the satellite. The applicability of the model is first demonstrated on a single strut using a one-dimensional approach. This approach is then extended to the full intelligent composite platform employing a three-dimensional approach. In this approach, the responses of the structure to a unit external force as well as unit internal piezoelectric control voltages are first determined, individually. The responses are then assembled in a system of equation as a coupled system and then solved simultaneously to determine the control voltages and their respective phases for the system actuators for a given external disturbance. This approach is an effective technique for the design of smart structures with complex geometry to study their active vibration suppression capabilities and effectiveness.

The Fraunhofer Gesellschaft is the largest organization for applied research in Europe, having a staff of some 12,700, predominantly qualified scientists and engineers, with an annual research budget of over one billion euros. One of its current internal Market-oriented strategic preliminary research (MaVo) projects is FASPAS (Function Consolidated Adaptive Structures Combining Piezo and Software Technologies for Autonomous Systems) which aims to promote adaptive structure technology for commercial exploitation within the current main research fields of the participating FhIs, namely automotive and machine tools engineering. Under the project management of the Fraunhofer-Institute Structural Durability and System Reliability LBF the six Fraunhofer Institutes LBF, IWU, IKTS, ISC, AiS and IIS bring together their competences ranging from material sciences to system reliability, in order to clarify unanswered questions. The predominant goal is to develop and validate methods and tools to establish a closed, modular development chain for the design and realization of such active structures which shall be useful in its width and depth, i.e. for specific R&D achievements such as the actuator development (depth) as well as the complete system design and realization (width). FASPAS focuses on the development of systems and on the following scientific topics: 1) on design and manufacturing technology for piezo components as integrable actuator/sensor semi-finished modules, 2) on development and transducer module integration of miniaturized electronics for charge generating sensor systems, 3) on the development of methods to analyze system reliability of active structures, 4) on the development of autonomous software structures for flexible, low cost electronics hardware for bulk production and 5) on the construction and validation of the complete, cost-effective development chain of function consolidated structures through application oriented demonstration structures. The research work will be oriented towards active vibration control for existing components on the basis of highly integrated, both, more or less established and highly innovative piezoelectric actuator and sensor systems in compact, cost-effective and robust design combined with advanced controllers. Within the presentation the project work will be shown using the example of one demonstration structure which is a robust interface, here for being integrated within an automotive spring strut system. The interface is designed as a modular, scalable subsystem. Being such, it can be used for similar scenarios in different technology areas e.g. for active mounting of vibration-inducing aggregates. The interface design allows for controlling uniaxial vibrations (z-direction) as well as tilting (normal to the uniaxial effect) and wobbling (rotating around the z-axis).

This paper reviews the investigations of introducing magnetorheological elastomer (MRE)-based technologies to the design of smart electronic devices. Piezoelectric power actuators are required to operate at a resonant state in order to deliver maximum mechanical energy to loads. Owing to the field-dependent dynamic flexural rigidity of MRE-based structures, power actuators utilizing such structures exhibit the capability of compensating the change of the loads and keeping the resonant frequency at a fixed value. Four kinds of bender configurations for such smart actuators will be reviewed. They are: a cantilever suspended by an MRE patch at its free end, a single-layer MRE-based sandwich beam surface-bonded by piezoelectric patches, a multi-layer MRE-based sandwich beam surface-bonded by piezoelectric patches, and an inserts reinforced MRE-based sandwich beams surface-bonded by piezoelectric patches. Their driving capability and field-controllable capability are discussed in a detail. In addition, MRE-based structures are extended to propose linear time-variant systems for time-frequency signal processing. The system function is presented and the Wigner-Ville distribution is used to analyze the time-frequency distribution of the time-delayed response of the system. The system is proved to be a damped-vibration system with field-controllable resonant frequencies. Due to the field-controllable time-frequency pattern of the time-delayed response, the system can be used for data encryption and signal modulation.

Aerodynamic control surfaces efficiency is among the major parameters defining the performance of generic aircraft and is strongly affected by geometric and stiffness characteristics. A target of the '3AS' European Project is to estimate the eventual benefits coming from the adaptive control of the torque rigidity of the vertical tail of the EuRAM wind tunnel model. The specific role of CIRA inside the Project is the design of a device based on the “Smart Structures and Materials” concept, able to produce required stiffness variations. Numerical and experimental investigations pointed out that wide excursions of the tail torque rigidity may assure higher efficiency, for several flight regimes. Stiffness variations may be obtained through both classical mechanic-hydraulic and smart systems. In this case, the attainable weight and reliability level may be the significant parameters to drive the choice. For this reason, CIRA focused its efforts also on the design of devices without heavy mechanical parts. The device described in this work is schematically constituted by linear springs linked in a suitably way to the tail shaft. Required stiffness variations are achieved by selectively locking one or more springs, through a hydraulic system, MRF-based. An optimisation process was performed to find the spring features maximising the achievable stiffness range. Then, the hydraulic MRF design was dealt with. Finally, basing on numerical predictions, a prototype was manufactured and an experimental campaign was performed to estimate the device static and dynamic behaviour.

The objective of this study is to evaluate the effect that mechanical training has on the properties of NiTi based shape memory alloys. The unique mechanical behavior of shape memory alloys, which allows the material to undergo large deformations while returning to their original undeformed shape through either the shape memory effect or superelastic effect, has shown potential for use in seismic design and retrofit applications for civil engineering structures. However, cyclic loading has been shown to degrade the energy dissipation capacity and decrease the recentering capability of the material due to fatigue effects. It has been recommended that mechanical training of superelastic shape memory alloys prior to use in applications can limit these fatigue effects. A factorial experimental design is employed to explore the optimal number of mechanical training cycles, strain level of training, and the effect of the loading rate after training in order to minimize the degradation in the loading plateau stress, residual strain, and equivalent viscous damping properties. The results presented can serve as a guide to optimizing the properties of NiTi shape memory alloys for seismic applications. The ability to obtain stable properties of shape memory alloys under a specified training schedule further supports the eventual implementation of the material into actual building and bridge systems as seismic design and retrofit devices.

Two models for predicting the stress-strain curve of porous NiTi under compressive loading are presented in this paper. Porous NiTi shape memory alloy is investigated as a composite composed of solid NiTi as matrix and pores as inclusions. Eshelby’s equivalent inclusion method and Mori-Tanaka’s mean-field theory are employed in both models. In the first model, the geometry of the pores is assumed as sphere. The composite is with close-cells. While in the second model, two geometries of the pores, sphere and ellipsoid, are investigated. The pores are interconnected to each other forming an open-cell microstructure. The two adjacent pores connected along equator ring are investigated as a unit. Two pores interact with each other as they are connected. The average eigenstrain of each unit is obtained by taking the average of each pore’s eigenstrain. The stress-strain curves of porous shape memory alloy with spherical pores and ellipsoidal pores are compared, it is found that the shape of the pores has a nonignorable influence on the mechanical property of the porous NiTi. Comparison of the stress-strain curves of the two models shows that introducing of the average eigenstrains in the second model makes the predictions more agreeable to the experimental results.

Shape memory alloys (SMAs) are a class of metallic alloys that exhibit unique characteristics such as shape memory effect and superelasticity effect. SMAs are found in two main phases: the high temperature phase, which is known as austenite (superelastic), and the low temperature phase, which is known as martensite. Although there are few civil engineering applications using SMAs, there have been considerably large numbers of research studies focusing on exploiting SMAs in seismic resistant design and retrofit of buildings and bridges. Most of these studies focus on utilizing the superelasticity phenomenon exhibited by SMAs at high temperatures. The effect of ambient temperature variation on the efficacy of superelastic SMA devices that are used in seismic applications is a major concern. This paper presents an analytical investigation on the effect of ambient temperature variation on the performance of superelastic SMA bridge restrainers during earthquakes. A thermomechanical constitutive model is developed to describe the constitutive behavior of the SMA restrainers at various temperatures. The SMA model is implemented in a 2-DOF bridge model and tested using 20 historical ground motion records. The ambient temperature is varied from a temperature below A_f to a relatively high temperature. The results of the study showed that SMAs are more effective when used in its austenitic phase and thus when the temperature decreases below A_f SMA devices lose a major part of their efficiency. On the other hand, the study also showed that at high temperatures the ductility demand of the bridge frames increases.

The interactions between the inflatable structure and shape memory alloy (SMA) strip actuators are investigated using finite element simulation. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is implemented to analyze the unique characteristics of SMA strip. For the numerical results presented in this paper, the ABAQUS finite element program has been utilized with an appropriate user supplied subroutine (UMAT) for the modeling SMA strip. In this model of SMA strip, the shape memory effect is restricted to one-way applications. The geometrically nonlinear, updated Lagrangian equilibrium formulation implemented in ABAQUS is used for the numerical model of inflated membrane structures.

Multi-actuators piezoelectric devices consist of a multi-flexible structure actuated by two or more piezoceramic portions, whose differing output displacements and forces are tailored according to the excitation properties of the piezoceramic materials and the desired working locations and directions of movement. Such devices have a wide range of application in performing biological cell manipulation, for microsurgery, and in nanotechnology equipment, and the like. However, the design of multi-flexible structures is a highly complex task since the devices have many degrees of freedom and, employ a variety of piezoceramics, but must carefully tune the movement coupling among the device parts to prevent motion in undesirable directions. In prior research, topology optimization techniques have been applied to the design of devices having minimum movement coupling among the piezoceramic parts, and in this work a number of these devices were manufactured and experimentally analyzed to validate the results of the topology optimization. X-Y nanopositioners consisting of two piezoceramic portions were addressed and designs considering low and high degrees of coupling between desired and undesirable displacements were investigated to evaluate the performance of the design method. Prototypes were manufactured in aluminum using a wire EDM process, and bonded to piezoceramics (PZT5A) polarized in the thickness direction and working in d31 mode. Finite element simulations were carried out using the commercial ANSYS software application. Experimental analyses were conducted using laser interferometry to measure displacement, while considering a quasi-static excitation. The coupling between the X-Y movements was measured and compared with FEM results, which showed that the coupling requirements were adequately achieved.

Magnetostrictive transducers are used in a broad variety of applications that include linear pump drives mechanisms, active noise and vibration control systems and sonar systems. Optimization of their performance relies on accurate modeling of the static and dynamic behavior of the magnetostrictive material. The nonlinearity of some magnetostrictive material properties along with eddy current power losses occurring in both the magnetostrictive material and in the magnetic circuit of the system makes this task particularly difficult. This paper introduces a static and a dynamic three-dimensional multi-physics boundary value problem that includes magneto-mechanical coupling for modeling magnetostriction and electromagnetic coupling for modeling eddy-current power loss (dynamic case only). It also includes the effect of the magnetic stress tensor, also known as Maxwell stress tensor, introduced by Kannan. The dynamic formulation is inspired by the finite element formulation in the Galerkin form introduced by Perez-Aparicio and Sosa, but focuses on a weak form formulation of the problem suitable for implementation in the finite element commercial software FEMLAB 3.1. Finally, an example is presented and compared to experimental results to validate the static model.

Most structural health monitoring analyses to date have focused on the determination of damage in the form of crack growth in metallic materials or delamination or other types of damage growth in composite materials. However, in many applications, local instability in the form of buckling can be the precursor to more extensive damage and unstable failure of the structure. If buckling could be detected in the very early stages, there is a possibility of taking preventive measures to stabilize and save the structure. Relatively few investigations have addressed this type of damage initiation in structures. Recently, during the structural health monitoring of a wind turbine blade, local buckling was identified as the cause of premature failure. A stress wave propagation technique was used in this test to detect the precursor to the buckling failure in the form of early changes in the local curvature of the blade. These conditions have also been replicated in the laboratory and results are reported in this paper. A composite column was subjected to axial compression to induce various levels of buckling deformation. Two different techniques were used to detect the precursors to buckling in this column. The first identifier is the change in the vibration shapes and natural frequencies of the column. The second is the change in the characteristics of diagnostic Lamb waves during the buckling deformation. Experiments indicate that very small changes in curvature during the initial stages of buckling are detectable using the structural health monitoring techniques. The experimental vibration characteristics of the column with slight initial curvatures compared qualitatively with finite element results. The finite element analysis is used to identify the frequencies that are most sensitive to buckling deformation, and to select suitable locations for the placement of sensors that can detect even small changes in the local curvature.

A benchmark study is a valid way to make comparison of kinds of Structural Health Monitoring technologies, for example modal identification, finite element model updating, damage identification and so on. Several successful benchmark SHM problems were developed by IASC-ASCE SHM Task Group and the encouraging analytical studies results were obtained. But this benchmark study is based on a steel-frame scale-model structure built in the laboratory. Due to the striking difference in structure’s properties, SHM system and so on between the structure in the laboratory and the real structure, many SHM technologies developed in the laboratory is not applicable to the real structure. Thus a new benchmark study based on a real structure is developed in this paper. The first and the second phase of a benchmark problem based on SHM system for Binzhou Yellow River Highway Bridge have been detailed and the criterion of benchmark problem are given simultaneously.

This paper describes work performed in the development of a set of specification for the construction of an integrated electronic system for piezoelectric wafer active sensor (PWAS). The paper starts with a comprehensive review of the PWAS material properties, dimensions, and electrical characteristics. PWAS of various shapes and sizes are considered. Two boundary conditions were examined: free PWAS and PWAS attached to actual structures. For both, the PWAS immittance and the allowable dc and ac voltages were considered. The predicted values were compared with measurements performed over a wide frequency range (10 kHz to 2 MHz). Next, the electronic-equipment specifications were considered. The PWAS can be used in a number of different ways to actively detect damage in structures. Our aim was to develop electronic-equipment specifications that would extract the optimum performance from the PWAS, i.e., maximize the coupling with the structure and obtain large-amplitude Lamb wave transmission and reception. Analytical predictions were compared with measurements made using current laboratory equipment. The comparative analysis revealed that the current electronic equipment does not fully exploit the PWAS capabilities. Hence, the PWAS equipment specifications were divided into two categories: “existing” and “desired”. The former category designates integrated electronic equipment that would offer the same PWAS performance as the existing lab equipment, but be of a lower volume/weight/cost. The latter category refers to advanced electronic equipment that will exploit the full potential of PWAS transducers while being of lower volume/weight/cost than the lab equipment. Both categories are presented and discussed in the paper.

New functionalities, higher comfort and increasing performance requirements are often be solved by adding new technologies to existing (passive) solutions. Monitoring and control approaches uses additional sensors and actuators, new materials, microprocessors and new devices realizing new and improved functionalities. Two effects are becoming more and more interesting: (1) the lifetime of new actuators/materials strongly depends on the usage-history, (2) the functionality of the new composed systems depends on the fully functionality of all elements. In the consequence, the availability of such new systems is decreased by the number of elements and depends strongly on the use. These effects are known and act against new developments improving performance behavior also in mechanical engineering, automotive systems etc. This will be also the case for multifunctional composite or compound systems such as piezomaterials, magnetostrictive alloys or smart memory alloys (SMA) and is actually within the focus of the Structural-Health-Monitoring (SHM)-community. This contribution explains a new and systematically structured methodological approach to avoid and eliminate failures in mechatronical systems in an integrated and intelligent way to achieve a desirable or required amount of utilization in compliance with a defined failure rate. The result is an enhancement of the dependability of such a system.

This paper examines the effects of uncertainty in a structural health monitoring application. Decision uncertainty acknowledges that classification system decisions are probabilistic. The particular task of interest consists of detecting and localizing which one, if any, of fifteen fasteners is loose in a thermal protection system panel. From laboratory data collected during a three month interval, a benchmark classification system is designed to detect and localize loose fasteners and corresponding accuracies are computed. The performance of this system is measured in terms of probabilities of detection, localization, and false alarm. When the benchmark classifier is applied to an independent test set of over 4,900 trials, the probability of detection is 99.6%, the probability of localization is 98.0% and the probability of false alarm is 1.0%. A method is described for reducing the effects of uncertainty and applied to the benchmark classification system. With this processing, the probability of detection becomes 99.0%, the probability of localization becomes 97.6% and the probability of false alarm becomes 0.3%.

The use of glass-reinforced plastics (GFRP) as a structural material is widespread because of their high strength and stiffness, low mass, excellent durability and ability to be formed into complex shapes. However, GFRP composite structures are prone to delaminations which can lead to a significant degradation in structural integrity. A number of non-destructive inspection methods have been devised to inspect such structures. One class of SHM system relies on the examination of the strain distribution of the structure due to its operational loads. This paper considers the strain distribution in a GFRP structure subject to loading. The strain distribution due to delaminations of various sizes and locations along the bondline of the structure has been determined by finite element analysis (FEA). A technique called the Damage Relativity Assessment Technique (DRAT) has been developed and implemented to process the data in order to amplify the damage detection process. An Artificial Neural Network (ANN) has been trained to relate this strain distribution to damage size and location. This ANN has been shown to predict the size and location of damage for a number of simulated cases. The extension of this technique is to detect multiple cracks in a complex structure with multiple loading sets. These studies will also be carried over for structures subjected to impulse loading. A major aspect of this effort will include the pseudo-automated assessment of the criticality of the damage. Results from computational and experimental work, in this regard will be presented and used in conjunction with the DRAT and the ANN techniques described above.

In this paper, a flow variance based structural damage identification method is introduced. It is a practical implementation of phase space warping concept as applied to damage identification. A coupled dynamical system is considered where a slow-time damage process causes drifts in the parameters of fast-time system describing measurable response of a structure. The method is based on the hypothesis that the distribution function of the fast-time trajectory is a function of damage state. In this method, estimated local expectation of trajectory in its phase space is used as a damage tracking feature vector. After the feature vectors are constructed, damage identification is realized by smooth orthogonal decomposition. Data processing time requirements of the flow variance based approach decrease by about 2 orders-of-magnitude compared with the phase space warping based method. A common form of the feature vectors is also discussed.

Structural Health Monitoring (SHM) of aircraft structures, especially composite structures, has assumed increased significance on considerations of safety and costs. With the advent of co-cured structures, wherein bonded joints are replacing bolted joints there is a concern regarding skin-stiffener separation, which might not be detected unless a rigorous non-destructive testing (NDT) is done. It would hence be necessary to be able to detect and assess skin-stiffener separation in composite structures before it reaches the critical size. One of the health monitoring strategies is through strain monitoring using fibre optic strain sensors such as Fibre Bragg Grating (FBG) sensors. The first aspect that needs to be addressed is the characterization of the FBG sensors. Issues of embedment in composites have also to be addressed. Before evolving a damage detection strategy, the sensitivity of the structural strain to skin-stiffener separations must be clearly understood and quantified. This paper presents the analysis and experiments done with a composite test box to study the effect of skin-stiffener separation on the strain behaviour. The box consists of two skins stiffened with spars made of Bi-Directional (BD) glass-epoxy prepreg material. The spars are bolted to the skins and removing suitable number of bolts simulates 'de-bonds'. The strains of the healthy box are compared with the unhealthy box. The strains in the experiments are monitored using both strain gauges and Fibre Bragg Grating (FBG) sensors. The experimental results show that there is significant change in the measured strain near and away from the debond location. The finite element analysis of the box is done using ABAQUS and the analysis is validated with the experimental results. A neural network based methodology is developed here to detect skin-stiffener debonds in structures. A multi-layer perceptron (MLP) neural network with a feed forward back propagation algorithm is used to determine the size/severity of damage. The FE model is used to generate the neural network training data for various sizes of debonds. The results show that the network is able to predict the damage size well. The network is implemented for a specified load. However, it is seen that the damage size predicted is independent of the applied load and the network performance is dependent on the fidelity of the finite element model used to train the network.

In structural health monitoring, the fundamental goal is to address the problem of damage identification, localization and quantification. Using the wave based approach, the presence of damage is visualized in terms of the changes in the signature of the resultant wave that propagates through the structure. Since surface mounted piezoelectric transducers have been used for monitoring, the voltage output of each sensor is used for signature characterization. Due to the time-varying nature of these signals, performance of some existing analyzing tools may not be satisfactory. In the present study, the use of the matching pursuit decomposition has been investigated as a signal processing technique to compare signals from healthy and damaged structures.

Fatigue crack growth during the service of aging aircrafts has become an important issue and the monitoring of such cracks in hot spots is desirable. A structural health monitoring system using an acoustic emission technique under development for monitoring safety of such structures is described in this paper. A “continuous sensor” formed by connecting multiple sensor nodes in series arrangement to form a single channel sensor is proposed to monitor acoustic emission signals. This paper describes the work in progress on developing sensors, instrumentation, and measurement technique applicable to on-board monitoring of fatigue cracks in 7075-T6 aluminum lap joints. The traditional AE sensors as well as bonded nodes of continuous sensors described above were used to monitor acoustic emission signals emanating from crack growth in aluminum 7075 T6 specimens. It was possible to differentiate the signals due to crack growth from noise signals arising from fretting as well as RF pickup. The sensitivity of the bonded sensor under development was comparable to commercial high sensitivity resonant frequency AE sensors. The relationship between acoustic emission parameters and the crack growth rate in the aluminum specimens is examined.

This paper discusses a proof test procedure for estimating and extending the fatigue life of composite coupons. The estimates were based on the acoustic emission data collected during the described proof test procedure. A group of coupon specimens that included both undamaged as well as damaged ones were tested to verify the ability to estimate the fatigue durability. For majority of the specimens tested the fatigue life of the coupons is inversely proportional to the cumulative AE energy collected during the proof test procedure. Based on the trend that was established, a new group of specimens AE based proof test was performed and using the acoustic emission response, the life was estimated. If one could estimate the fatigue life, it would be possible to identify those specimens, which are likely to fail prematurely. For such specimens it may be possible to extend the fatigue life by appropriate reduction in the cyclic load amplitude. This hypothesis was tested on the last group of specimens. The results obtained during the life extension phase actually show that it is possible to identify the specimens, which are likely to have short life and extend the fatigue life by subjecting them to less demanding load history.

In the previous conference, we produced a new metal core-containing piezoelectric ceramics fiber by the hydrothermal method and extrusion method. The insertion of metal core is significant in view of its greater strength than ceramics materials, and electrodes are not required in the fiber's sensor and actuator applications. A new smart board was designed by mounting these piezoelectric fibers onto the surface of a CFRP composite. After that, this board is able to use this board to a sensor, actuator and vibration suppression. In this paper, we measured s mechanical properties of metal core piezoelectric fiber. We examined the tension test of a piezo-electric fiber, and measured the Young's modulus and breaking strength. Moreover, the expansion in the fiber unit was measured, and the displacement of the direction of d31 was measured. In addition, a piezo-electric fiber that used lead free material (BNT-BT-BKT) to correspond to environmental problems in recent years was made.

This paper presents preliminary results from study of a magnetostrictive energy harvesting transducer. The magnetostrictive samples studied in the device were 1/4" diameter and 2" long cylindrical rods of commercially available Terfenol-D and research-grade specimens of a new ductile Iron-Gallium alloy known as Galfenol. The transducer design was motivated by interest in harvesting low frequency vibration energy with a target of optimal performance at 50 Hz. The transducer was designed to facilitate study of the sensitivity of magnetostrictive transduction performance to prestress loads in the range of 1 to 4 ksi and DC magnetic biases of from 0 to 300 Oe. Transducer performance was assessed by measuring the open circuit voltage produced by the harvester when it was excited by a mechanical shaker at force levels of 1-4 pound force and at frequencies of up to 100 Hz using both single frequency and swept sine operational modes. The performance comparisons consist of open circuit induced voltage output as a function of prestress and magnetic bias for both Terfenol-D and research grade Galfenol and open circuit induced voltage as a function of frequency and mechanical excitation at biases optimized for different prestress conditions. Scalability tests show how electrical output varies with mechanical input for the two materials under the different operating conditions. The electrical output for operation with Terfenol-D and Galfenol under the same mechanical force inputs are presented and observations of the differences associated with the performance of these two materials are discussed.

Eccentric angular motion transfer mechanisms are analyzed in the paper. The de-balancing mass has an additional degree of freedom in these mechanisms. It was found that certain types of such mechanisms posses interesting nonlinear dynamical features when a self-resonance motion mode occurs. Such self-resonance motion mode takes place when the main driving element rotates with relatively high angular velocity, but low frequency vibrations are generated in the range of fundamental frequency of the system. Analytical, numerical and experimental investigations of nonlinear vibration excitation systems were performed. Such vibration excitation systems have high practical value as there is no necessity for complex vibration control equipment -- the stability of operation is guaranteed by non-linear dynamical interactions. Laser velocity measurement system was used for experimental investigations of the dynamical properties of the system. The results of the investigations validated the results of the theoretical analysis and provide a background for developing new type of dynamical mechanisms.

A closed-form dynamic model of a 6-UPS (universal-prismatic-spherical) Stewart platform suitable for modeling and analyzing the vibration damping of the 6-UPS Stewart platform based systems is developed through Newton-Euler dynamic approach. In the formulation, the external excitations on the base-platform of the 6-UPS Stewart platform are considered and the developed model is in a closed form, so the model can not only be used to model and analyze the vibration damping of the 6-UPS Stewart platform based systems when the base-platform is exerted external excitations, but also can be used to design the control algorithms of the 6-UPS Stewart platform based systems to realize the feedback control of the vibration damping. The dynamic formulation is implemented for the modeling and analyzing of the vibration damping of a 6-UPS Stewart platform based system and some numerical simulation results are also presented.

This work presents dynamic characteristics of 3-axis active mount featuring the rubber element and the piezoelectric actuator. The rubber element is adopted to isolate external disturbance in the non-resonance frequency range, while the piezoactuator is employed to isolate the vibration in the neighborhood of the resonance. After identifying dynamic properties of the rubber element and the piezoactuator in the frequency domain, the governing equation of the active mount system is derived. Subsequently, generated force and moment of each actuator is evaluated in time domain. In addition, a comparative work between the simulation and measurement is undertaken.

The PiezoHydraulic Pump (PHP) used in this work currently uses proprietary check valves that allow the PHP to be operated at 1 kHz. At a bias pressure of 500 psi and operating voltage of 1 kV, the PHP produces a mechanical power output of 46 W. The PHP was baseline tested using both the proprietary valves (internal) and external commercial passive check valves. Using the external valves at a bias pressure of 80 psi, the PHP was tested at various frequencies. At an operating frequency of 150 Hz, the maximum flow rate was 0.91 cc/s, while at 125 Hz, the maximum mechanical power output was 0.18 W (0.64 W/kg). This significant decrease in characteristics can be attributed to an increase in system compliance by moving the valves external to the pump housing and possible air entrapment within the chamber.

A new, low cost technique for excitation and control of high density, actuator arrays has been developed. Primarily aimed at the tactile display of universal text, Braille and graphics for the Blind community, magnetic forces are utilised to actuate and hold individually addressable pins. Current tactile displays that allow Blind people to interact with the world via electronic media are expensive and due to their inherent complexity can only display the Braille language, which on average only 10% of visually impaired people in Western society are able to read. There is a need for a more flexible communication device. Using multilayer printed circuit board techniques to minimize production and assembly costs, large arrays of magnetic solenoid actuators were fabricated on a single substrate. They were electrically interconnected to allow matrix addressing of any single element in the array to reduce electronic component count. A bistable mechanism was produced using a permanent magnet layer allowing the solenoid actuator to be toggled between an 'up' state and a 'down' state. Besides being necessary for matrix addressing, this bistability gives good energy efficiency as power is only required when the system is updated and not when holding the static display. An error correction technique was developed that automatically corrected a bistable actuator if it had mistakenly moved into an incorrect position through mechanical shock. A 360 actuator demonstration unit was produced that displayed alphanumeric text, Braille or graphics in a tactile form.

The objective of this paper is to derive a new adaptive control law for the control of the rotation angle of a smart projectile fin using a piezoelectric actuator. The smart projectile fin consists of a flexible cantilever beam with a piezoelectric active layer, which is mounted inside a hollow rigid fin and is hinged at the tip of the rigid fin. The rotation angle of the fin can be controlled by deforming the flexible beam. In the closed-loop system, asymptotic trajectory tracking of the fin angle is accomplished. Simulation results are presented which show that trajectory control of the fin angle is accomplished in spite of large uncertainties using adaptive control law and the flexible modes remain bounded during maneuvers.

Smart materials' ability to deliver large block forces in a small package while operating at high frequencies makes them extremely attractive for converting electrical to mechanical power. This has led to the development of hybrid actuators consisting of co-located smart material actuated pumps and hydraulic cylinders that are connected by a set of fast-acting valves. The overall success of the hybrid concept hinges on the effectiveness of the coupling between the smart material and the fluid. This, in turn, is strongly dependent on the resistance to fluid flow in the device. This paper presents results from three-dimensional unsteady simulations of fluid flow in the pumping chamber of a prototype hybrid actuator powered by a piezo-electric stack. The results show that the forces associated with moving the fluid into and out of the pumping chamber already exceed 10% of the piezo stack blocked force at relatively low frequencies ~120 Hz and approach 40% of the blocked force at 800 Hz. This reduces the amplitude of the piston motion in such a way that the volume flow rate remains approximately constant above operating frequencies of 500 Hz while the efficiency of the pump decreases rapidly.

The numerical simulation is performed for the damage induced acoustic emission and the wave propagation event of composite plates by the finite element transient analysis. The acoustic emission and the following wave motions from a predictable damage under a static loading is simulated to investigate the applicability of the explicit finite element method and the equivalent volume force model as a simulation tool of wave propagation and a modeling technique of an acoustic emission. For such a simple case of the damage event under static loading, various parameters affecting the wave motion are investigated for reliable simulations of the impact damage event. The numerical experiment is also conducted for simulating the full procedures from the impact phenomenon to the damage induced acoustic emission wave. The numerically reproduced wave signal is transformed by wavelet transform to analyze the frequency and the resolution characteristics between the acoustic emission signals of various damage mechanisms. The high velocity and the small wave length of the acoustic emission require a refined analysis with dense distribution of the finite element and a small time step. In order to fulfill the requirement for capturing the exact wave propagation and to cover the 3-D simulation, we utilize the parallel FE transient analysis code and the high performance computing (HPC) technology.

In structural health monitoring, energy dissipation of wave propagation is a key factor to determine optimal placement of sensors and quantify damage. This paper focuses on the study of wave scattering and attenuation in fiber-reinforced composite laminates with damage. In order to obtain the overall attenuation coefficient, the propagation of elastic shear wave in fiber-matrix medium is investigated starting from the Helmholtz equation. The wave attenuation due to interfacial damage is considered. The attenuation due to cracks of varying sizes and the effect of frequency on the attenuation value has been examined. It can be shown that a critical frequency exists at a given crack size for which the attenuation in the composite medium is at its highest value. Furthermore, the wave attenuation in composite laminates is investigated by incorporating energy transfer in layerwise medium. The overall attenuation coefficient for the laminate is obtained. Experiments are also conducted to evaluate some of the observations obtained from the model.

With increased usage of shape memory alloys (SMA) for applications in various fields, it is important to understand how the material behavior is affected by factors such as texture, stress state and loading history, especially for complex multiaxial loading states. Using the in-situ neutron diffraction loading facility (SMARTS diffractometer) and ex situ inverse pole figure measurement facility (HIPPO diffractometer) at the Los Alamos Neutron Science Center (LANCE), the macroscopic mechanical behavior and texture evolution of Nickel-Titanium (Nitinol) SMAs under sequential compression in alternating directions were studied. The simplified multivariant model developed at Northwestern University was then used to simulate the macroscopic behavior and the microstructural change of Nitinol under this sequential loading. Pole figures were obtained via post-processing of the multivariant results for volume fraction evolution and compared quantitatively well to the experimental results. The experimental results can also be used to test or verify other SMA constitutive models.