This PDF file contains the front matter associated with SPIE Proceedings Volume 10601 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Smart glass or switchable transparency panels are being commercialized for applications ranging from privacy panels to controlling solar load for buildings and vehicles. However, the technologies that have been developed such as electrochromic, polymer dispersed liquid crystal, and suspended particle devices are complex and expensive, and additionally switch from partial transparency to a tinted or scattering state, not having a highly reflective state, which limits applications. Our group has developed an optofluidic smart glass which should have 10x lower cost than current technologies. It is based upon a reflective structure that switches to transmissive by introducing an index-matching fluid. Previously, we have shown such a panel that consists of a solid plastic corner-cube array with a thin cavity behind it. With air in the cavity the panel is highly reflective based upon total internal reflection. We have shown inexpensive index matching fluids that when pumped into the cavity result in near-perfect transparency. However, our corner-cube array panels suffer from transmission at angles larger than 20 degrees in the reflective state. This transmission is refractive passing oblique rays at a different angle than line-of-sight, but nonetheless compromises performance. Here, we show a two-layer structure consisting of two one-dimensional solid corner reflector arrays with the layers having rotated axes. Rays beyond the TIR angle for one layer are refracted below the TIR angle for the second layer. Each layer has a cavity layer for introducing index matching fluid, and we show high transmission switching up to 60 degrees.

Two-dimensional thin plates are widely used in many aerospace, automotive and marine applications. Vibration attenuation can be achieved in these structures by attaching piezoelectric elements on to the structure integrated with shunt damping circuits. This enables a compact vibration damping method without adding significant mass and volumetric occupancy, unlike the bulky mechanical dampers. Practical implementation of shunt damping technique requires accurate modeling of the host structure, the piezoelectric elements and the dynamics of the shunt circuit. Unlike other studies in the literature of piezoelectric shunt damping, this work utilizes a multi-modal equivalent circuit model (ECM) of a thin plate with multiple piezo-patches, to demonstrate the performance of shunt circuits. The equivalent system parameters are obtained from the modal analysis solution based on the Rayleigh-Ritz method. The ECM is coupled to the shunt circuits in SPICE software, where the shunt configuration consists of three branches of electrical resonators, each tuned to one vibration mode of the structure. Using the harmonic analysis in SPICE for a range of excitation frequencies, current output of each ECM branch is calculated for open-circuit and optimum shunt circuit conditions. The current of ECM branches are then converted to the displacement outputs in physical coordinates and validated by the finite-element simulations in ANSYS. It is shown that the vibration attenuation of a vibration mode can be successfully achieved when there is a reduction in the corresponding current amplitude of the ECM branch. This correlation can be utilized in the design of efficient linear/nonlinear shunt circuits.

Triboelectric Nanogenerator (TENG) is a novel technology to convert mechanical energy into electricity for energy harvesting and sensing applications. Therefore, developing high performance TENG systems for practical applications is a very important and attractive topic. This study presents an efficient and extra light-weight TENG device using polyimide aerogel as the main electricity generation component. The small size porosity of the selected material will significantly change the effective dielectric thickness as well as the contact area resulting in the improvement of the TENG electrical output. The performance of proposed porous system in comparison with a system with compressed polyimide layer is evaluated to show the advantage of used aerogel. In addition, the electrical outputs of the enhanced device under different mechanical and electrical conditions are studied. Through the material fabrication and implementation, the proposed TENG can be successfully employed to boost the performance of various TENG-based energy harvesters and self-powered sensors.

Engine technology advancements is continuing to be on the rise, manufacturers involved in the development and the making of these engines are continuously striving to improve engines operational capabilities, fuel efficiency and durability. Altitude and Mach number delineate the operational set points for the engine. The core aim of these efforts is to enable production of adequate thrust to allow safe and stable maneuver of operation. The performance requirements of the engine are dependent on the mission profile and its characteristics. Increasing the efficiency and minimizing operative cost by reducing fuel consumption is an important factor for a successful turbofan engine. This leads to the fact that any decrease in the percent of fuel consumption will render a significant saving of running costs over the life of the engine. Further, with equally slight increase in the efficiency, the operational life of the engine will improve tremendously. The work being presented in this paper is focused on acquiring data such as thrust, speed; altitude etc… generated from a turbofan engine simulator “DGEN 380” which resembled an actual engine in operation. Conditions such as specified components unexpected failures under a quantified flight path are being investigated to assess the performance of the engine in such operational circumstances. Results pertaining to failure diagnosis based on the engine response obtained from the virtual test bench are presented and discussed.

Risers are crucial components in offshore production systems, and failure of a riser can potentially cause catastrophic damage to the environment and significant loss of production. The early identification of damage in a riser is essential to prevent failure from occurring, and vibration-based structural health monitoring (SHM) methods may be a viable means of achieving this. This study seeks to determine if there is merit to the application of vibration-based SHM methods to identify damage in top-tensioned risers under wave loading. To that end, two SHM methods are proposed and applied to experimental data obtained from a riser model placed in a wave flume with damage simulated as pre-tension loss. The proposed methods utilize the shift of the first natural frequency of the riser for damage identification. In the first method, the natural frequency is obtained from a frequency response function relating the water surface elevation and acceleration response of the riser model. In the second method, an ambient response analysis method is applied. Both methods are able to identify the natural frequency shifts and there is potential for detection and severity assessment of damage.

The final properties of cementitious materials (strength and durability) strongly depend on the mix proportions and the fresh state of the latter. It is therefore imperative to investigate the early stages, assess the quality of the mixes as well as monitor their time evolution. In this direction, ultrasonic measurements, since many decades, have been proposed as the most efficient tool for quality control and condition characterization due to their ability to inspect, detect, locate and continuously monitor the material’s performance throughout the entire lifetime. However, wave propagation can be quite complicated, especially if the material heterogeneity and wave-microstructure interactions are taken into account. For this reason, in the current study, the ultrasonic experiments are complemented by numerical analyses of wave propagation offering the advantage of easier, faster, repeatable and parametric implementation. The strong dispersion and attenuation trends observed in both the experiments and the numerical tests make, herein, the additional implementation of scattering theories necessary as the third pillar. The results show good match between the experimental and the numerical methods as well as between the numerical simulations and scattering theories, thus providing a more holistic insight of wave propagation in microstructured cementitious materials. In the framework of this study, cement pastes and mortars (containing sand or glass beads as aggregates) are investigated, while the results are demonstrated in terms of pulse velocity and attenuation as a function of frequency revealing interesting information on the influence of the aggregate content on the quality of the mixes.

Nuclear dry cask storage systems are being used for extended periods of time. Structural health monitoring of these casks has grown out of concern that the radioactive waste could jeopardize the casks’ structural health as time progresses. Ultrasonic guided waves offer a potential solution for monitoring the nuclear casks structural health without opening the containers. This paper explores sensing techniques on small-scale mockup and full scale dry cask storage systems. Methods include acoustic emission (AE) as well as active sensing. Results showed accuracies in localizations, differences in sensing techniques, structural responses, and the capabilities of ultrasonic guided waves in dry cask storage systems.

In this paper, eddy current pulsed thermography in transmission mode was used to detect the damages caused by low-velocity impacts in carbon fiber-reinforced polymer and basalt-carbon hybrid fiber-reinforced polymer laminates. In particular, different hybrid structures including intercalated stacking and sandwich-like structures were used. The impact energy of 12.5 was used for the evaluation of the impact damage level. Ultrasonic phased-array C-scan was performed for comparative purposes. In addition, the advantages and disadvantages of the two structures were identified and discussed.

The thermoelectric generating device can convert the heat flow due to temperature difference into electric energy by the Seebeck effect. In general, electric power can be obtained by alternately arranging N type thermoelectric elements and P type thermoelectric elements and connecting upper and lower staggered electrodes (π type structure). However, the generation capacity due to Seebeck effect is low, and even bismuth-telluride thermoelectric elements widely used at the present time are at most about 200 μV / K. Therefore, it is necessary to arrange hundreds of π structures, but the π structure is complicated, poor mass productivity, and there is a problem of increasing the internal resistance due to being connected in series. The nickel material and aluminum material can be directly bonded by applying temperature and pressure . Using this feature, two nickel plates with a thickness of 0.2 mm, a length of 30 mm and a width of 15 mm and three aluminum plates were alternately laminated and directly bonded. An anodized film of 1 μm is formed on the surface of the aluminum plate, and the oxide film is peeled off by 5 mm from the end portion by polishing. Direct bonding was performed by holding for 40 minutes under the conditions of a pressure of 7.6 MPa, a temperature of 600 ° C. and a degree of vacuum of 0.4 Kpa. By selectively forming an anodic oxide film on the surface of aluminum and using it as a mask, it is possible to selectively and directly bond them. Since only the aluminum portion from which the anodized film has been removed is bonded, if it is slightly pulled, it peels off, and five layers accordion type structure can be produced. It was found that by adding a temperature difference of 73 ° C to this device, electric power of maximum 20 μW can be obtained.

This research work focuses on vibration energy harvesting in order to design an alternative to batteries for standalone, left-behind wireless devices. This study brings a new vision on bistable generators featuring nonlinear stiffness, presenting a wide operating frequency bandwidth compared to linear generators for a better adaptation to complex excitations. In this study, original behaviors of bistable oscillators are considered and analyzed for vibration energy harvesting, consisting in subharmonic motions for which the mass oscillates at a frequency N times lower than the excitation. First, experimental analysis is conducted with a generator integrating buckled beams for the bistability feature. It is shown that, in addition to the well-known first harmonic behavior, the third subharmonic orbit widens the bistable microgenerator useful operating frequency band by 180% compared to the sole exploitation of the first harmonic motion. A second part of this study analytically investigates those subharmonic orbits for the optimized design of future generator. The different orbits are obtained with the harmonic balance method and their stability is calculated for small disturbances. Stable orbits being more or less easy to reach and maintain, a new criterion is introduced, namely the stability robustness, indicating the stable orbit sensitivity to disturbances of different levels. For low stability robustness, the orbit will be considered as non-suitable for energy harvesting leading to a new definition of bistable generators frequency bandwidth. Analytical results following this method show good agreement with previous experimental results validating the relevance of stability robustness criterion.

Piezoelectric materials can be utilized to harness unused energy to power electronic devices. This article outlines the construction of a piezoelectric energy harvesting floor and evaluates the floor’s energy collection capabilities. This project utilizes the piezoelectric material lead zirconate titanate (PZT) to collect energy. Tests were conducted to determine the strength of the PZT material and the pressure plate, and COMSOL modeling was used to simulate the power output of the energy harvesting floor before the prototype was fabricated. Various adhesives were analyzed to ensure the selected adhesive had the maximum electrical conductivity. The piezoelectric elements were wired in parallel to increase the low-level AC current; the output of the energy harvester was connected to a circuit that converted the AC power to DC. The energy was stored until the capacitor was filled and then was released at a constant voltage and current allowing a device to be charged. Longevity and durability took precedence over the magnitude of energy harvested from each impulse. Protecting the piezoelectric elements was the focal point of the design. Finding the correct balance between the life span of the project and the generation of energy was paramount.

A robust individual pitch control strategy is presented to deal with periodic load disturbances on wind turbines under operating point variation. The asymmetric loads are mainly caused by the tower shadow and wind shear effects. Multi-blade coordinate (MBC) transformation is utilized to model the turbine dynamics under various operating points. The coupling dynamics of the multi-input multi-output (MIMO) system are considered to reveal high harmonic frequency peak reduction. The stability and robustness performance of the system under uncertainties are guaranteed by robust control design. The performance of the synthesized controller is compared with a collective controller and a PI individual controller. The results show significant load mitigation in periodic frequencies.

In recent years, the damage assessment by means of Laser Doppler Vibrometry (LDV) has become very attractive as it provides non-contact, non-destructive, accurate and improved evaluation of advanced materials. This study deals with the development of advanced software based on LabVIEW in order accurate and automated measurements of acoustic activity to be achieved. Furthermore, this automated method was applied for damage detection in aluminum 1050 Η16 undergone cyclic mechanical loading. LDV was used to measure the amplitude of a Rayleigh surface wave propagating in aluminium specimens. Rayleigh waves are experimentally generated with a piezoelectric transducer and detected by LDV. The proposed measurement technique is used to assess the damage and its evolution, in terms of the increasing amplitude of Rayleigh wave, in 1050 H16 specimens under cyclic mechanical loading. In addition, the reduction in the Rayleigh wave velocity it depends on ultimate fatigue strength of material. The development of this process allows the automated, improved and detailed damage assessment of composite materials.

In this work a wind turbine blade has been instrumented with two different types of optical fiber sensors. The first one is a traditional chain of Fiber Bragg Grating sensors, able to measure a large number of strain values along the fiber; the second one is a sensor based on Optical Backscatter reflectometry (OBR), able to provide a continuous measurement along the fiber. The two fibers are placed in parallel on the structure and different experimental tests have been carried out to compare the two technologies on a reduced-scale model of a offshore wind turbine blade.

This work deals with the development of a prototype infrared sensor and infrared thermography (IRT) approach for nondestructive testing of aerospace materials and components. Thermography offers noncontact, wide area detection of subsurface defects, and can be used as an alternative or complement to conventional inspection technologies. The novel approach is based on the combination of Pulsed Phase Thermography (PPT) and Lock-in Thermography (LT). The technique provides with initial fast qualitative information of defects by the PPT technique such as location, approximate dimensions and depth of the defect, as well as an indication of the frequency range over which the LT technique would subsequently be applied for obtaining accurate quantitative characterization of the damage. The new IR approach enables fast inspection as well as qualitative and quantitative results such as the size, type and depth of defects.

This work aims to develop a nondestructive technique based on Near Infrared (NIR) imaging for the evaluation of transparent and semi-transparent composite materials, such as Glass Fiber Reinforced Polymers (GFRP) and laminated glass aircraft components. The NIR technique offers enhanced optical imaging of damage which cannot be detected with conventional optical inspection. The NIR imaging can be performed in reflection or transition mode (i.e. radiation reflected from or transmitted through an object under inspection). While the NIR transmission mode is better for detecting deeper defects, it has a serious limitation for field application in real aircraft parts, since it requires simultaneous access (e.g. illumination source, cabling, etc.) of both sides of the structure. For these reasons, an innovative NIR approach, the NIR Double-Transmission Mode (NIR-DTM), has been developed. The new approach is based on the advantages of both aforementioned techniques while eliminating their deficiencies. In order to optimize the use of NIR imaging for field applications, different parameters that affect the operation of the technique were considered. These parameters include the surface geometry, the distance from the material under investigation, the inspection angle, as well as the type and intensity of excitation source. Finally, image processing and analysis tools were used to improve the inspection sensitivity and further decrease the inspection time.

One of the important characteristics of metallic structures affecting structural integrity is their behavior in corrosive environment. In this respect, aircraft components made from aluminum alloys can catastrophically fail due to pitting corrosion and fatigue damage. Pitting, because of stress concentration, is responsible for fatigue crack nucleation in the material. In the current study, tensile-shape samples of aluminum alloy are immersed in NaCl solution, which simulates the natural exposure in a marine environment. This has an objective to induce accelerated electrochemical damage of the material under testing by the controlled pitting corrosion in a specific area of the surface using different electrochemical techniques, while the rest of the specimen remains completely sealed. In order to investigate the effect of pitting corrosion on the degradation of the material’s mechanical performance, the specimens were subjected to cyclic loading. The corrosion fatigue testing results were compared to data obtained from the uncorroded materials. Using a scanning white-light interferometer the pits' morphology was characterized and the effect of corrosion on the fatigue life was assessed. The results were validated using two complimentary nondestructive techniques, namely infrared thermography and acoustic emission.

Higher inner stress than the strength of the shell is one of the main problems for the safety of batteries. In order to improve the safety management of batteries, a non-destructive method has been adopted to real-time monitor the stress level of the NCM batteries during charging/discharging process. Besides, the relationship between strain and stress for the coin cell has been analysed. During cycling process, the stress level has the same trend with the potential value, and residual stress has been found at the end of every cycle. In order to investigate the relationship between the stress accumulation and the electrochemical performance of the cells, the residual stresses and the normalized capacities of NCM cells under different current densities have been monitored.

This work focuses on the development of novel nano-reinforced composite protective coatings for a wide range of applications, such as aerospace, automotive, energy and cutting tools industries. In the present work, silicon carbide (SiC) nanoparticles of 100nm and purity of 99% were used to form nickel-high phosphorus matrix composite (Ni–P– SiC) coatings on steel plates, which were prepared by direct current electrodeposition with duty cycle values of 50% and 80%, while the frequency of the imposed pulses was varied between 0.1Hz and 100Hz. Nickel sulphate served as the primary Ni source, while nickel chloride was added to improve anode corrosion, solution conductivity, and uniformity of the coating thickness distribution. Phosphorous acid acted as the P source in the solution and H3BO3 was added as buffering agent. Sodium dodecyl sulphate has been used as a wetting agent, and saccharin as a stress reducing additive. XRD characterization showed that the structure of NiP composite coatings as deposited were amorphous, irrespective of the presence of SiC. After heat treatment at 400°C for one hour, the amorphous phase was crystallized at steady phases of Ni and Ni₃P. The morphology and structure as well as the elastic property of the coatings with and without the SiC nanoparticles were assessed using infrared thermography and scanning acoustic microscopy.

Today’s electronics industry, due its continues growth and increasing demand for devices such as cell phones, satellite navigation systems, health devices, etc., faces important challenges related to the vast quantity of raw materials needed for sustainability and the quantity of waste generated from electronics equipment. To sustain its growth, the electronics industry needs innovations, such as the miniaturization of printed circuit boards (PCB) for increasing components density. Consequent development of miniaturized electronics design plays, therefore, a key role for the reduction of energy consumption and raw materials sustainable use. A factor, however, that currently limits this endeavor is the availability of hyperfine pitch solder powder pastes. The present work focuses on the development of novel, low cost, type 8 and 9 solder pastes with hyperfine solder particles (with size distribution of 1-10 μm) aiming at printing PCBs with increased component density. The solder joint quality was characterized using nondestructive techniques after manufacturing at different reflow parameters. Infrared thermography and white light interference microscopy provided information on internal defects such as presence of micro-voids, as well as on the topography of geometrical variations of solderbals, solder errors, and warpage of components, which are related to the thermal history of the component during reflow.