Two sensors have been evaluated as components of a sensor suite to be used to characterize polymer composite cure; the evanescent wave visible light sensor (EWVLS) and the curing resin emission sensor (CuRE). These two sensors have been sued to characterize the cure of HEXCEL F650 BMI graphite fabric composite in a laminate process. Our results indicate that the EWVLS signature may be useful for process control and that the CuRE sensor provides important diagnostic information.

Following the processing and manufacture of resin and composite parts and during their lifetime, the distribution of internal residual strain and any variations in moduli are generally unknown. Real-time information on these parameters would be valuable for improving material performance and reliability. It is believed that measurements related to material residual stresses or strain and moduli can be obtained by measuring the longitudinal wave velocities within acoustic waveguides (AWG) embedded within a material. The concept is that the wave velocities within embedded AWG are related to the material bulk modulus, density and Poisson's Ratio which are all in some degree related to the material state of cure, and finally the internal residual stresses. Based on this concept it is shown that the AWG of different diameters embedded within the same resin part of uniform internal stress distribution, the AWG wave velocities should vary in relation to the square root of the AWG diameter. Experimental results using AWG of 5, 10, 16, 20, 40 and 62 mil diameter Nichrome embedded within Shell 815 clear resin with optically measured uniform strain, demonstrate a direct relationship between AWG velocities and the square root of the AWG diameter. Consequently, it is reasoned that for a part with several embedded AWG, each of the same diameter, then differences in the AWG velocities would yield information on differences in the residual strain and moduli within the part.

The curing of thermoset resins is a critical step in the manufacturing of thermoset polymer matrix composites, determining the ultimate mechanical properties of the material, and accounting for a significant fraction of the cost of manufacturing. The use of in-situ cure monitors will permit adaptive control of the cure process, thereby lowering energy costs, reducing scrap rate, and optimizing mechanical properties. We describe here the design and demonstration of an embeddable fiber optic sensor to measure the degree of cure of thermoset resins through characterization of the changing viscoelasticity of a curing resin. By coupling a miniature actuator to a fiber optic strain sensor, the assembly can be made to vibrate while immersed in a curing resin. Comparison of the phase of the electrical actuation to the phase of the resulting strain in the sensor permits a measure of the loss tangent of the resin, where the loss tangent is the ratio of the loss modulus to the storage modulus. As the crosslinking of the resin proceeds, the loss tangent also changes, reflecting the changing rheology of the resin. The loss tangent is found to attain a maximum at the gel point of the resin, when a polymer network is formed. Further crosslinking may be tracked as the loss tangent decreases following gelation. After complete cure of the epoxy, the fiber optic sensor functions as a conventional optical strain sensor, permitting in-service strains in the composite part to be measured. Preliminary experimental results are presented here, which demonstrate that by combining a magnetostrictive actuator with a fiber optic strain sensor, the rheology of a curing thermoset resin may be monitored by measuring the changing loss tangent of the resin.

In an effort to reduce cost and maximize the utility of each test specimen, our laboratory has incorporated several types of non-intrusive techniques for surface analysis and sample characterization. The newest and one of the most promising techniques is computer enhanced photon tunneling microscopy. This paper describes our current photon tunneling microscopy system and its use in the characterization of polymer matrix composite materials surfaces. The technique of photon tunneling microscopy was first made available commercially through a licensee of the Polaroid Corporation in 1992. Our system was purchased in 1994 and has been used primarily to study the effects of accelerated aging on composite materials.

In this work, we demonstrate the multifunctional use of fibers as reinforcement and process sensors. We show that monitoring the ultrasonic signal response through the reinforcing fiber in glass matrix composites yields on-line information which is related to the densification of the composite. A single monofilament SiC fiber is used as an ultrasonic waveguide to transmit 0.5MHz ultrasound through the sample during firing. The leakage of the ultrasound to the matrix was found to be a strong function of the instantaneous relative density of the matrix in the vicinity of the fiber. Two different SiC fibers were used to investigate the effects of the interface bonding upon leakage. It was shown that the 'sensor' data can be used to aid in the process design and optimize the firing schedule by minimizing the time at temperature necessary to achieve full density.

Laser ultrasonic techniques for in-process materials characterization show significant potential for applications where rapid, remote sensing is a requirement. While the potential is great, relatively few on-line industrial systems currently exist owing to difficulty associated with designing and implementing robust laser ultrasonic systems. Although laser-based ultrasound is becoming widely used as a laboratory tool for materials characterization, transitioning this technology into a robust industrial process control system poses several problems. Chief among these are suitable lasers for ultrasound generation, ultrasound detection, interferometer design, required signal processing, and overall system performance. This manuscript addresses each of these issues in turn, and gibes examples of industrial process control implementations where appropriate. Finally, recent advances in increasing laser based ultrasonic sensitivity are discussed.

The quality of a final product is assured by a combination of process control measurements during manufacturing and acceptable final inspections. These activities are often performed independently and the information from various measurement method and production steps is rarely shared. For advanced structures, that require a high level of assurance, a data fusion approach using both process data and NDE measurements is proposed to improve interpretation by utilizing all available information in a systematic manner. NDE and process data fusion can occur in may forms, some relatively simple and some very complex. As the complexity and performance requirements of a product increase the need for data fusion can justify the additional cost of implementation. Typically, a data fusion workstation is used. The data fusion workstation accepts information in a variety of forms, providing a platform to interpret the data in combination or simplified presentation modes. The interpretation of data is improved by knowledge obtained from both in-process monitoring and multiple inspection measurements, leading to reduced risk of failure.

The objective of this work was to demonstrate the use of ultrasonics to determine the end-of-curve for autoclave cured, graphite/epoxy composite laminates. The fundamental benefit of this work will be understanding when to complete the temperature hold and cool down the autoclave and, therefore, consistently produce composite laminates with the desired material properties. An additional benefit is the ability to follow the changing viscosity of the resin during the initial part of the cure. The general approach to this program involved using pulse-echo ultrasonics to measure the transit time for longitudinal ultrasonic waves to pass through a graphite/epoxy composite laminate during cure. Sixteen, 32 and 64 ply (0/90)s graphite/Fiberite 934 epoxy panels were fabricated and cured to various end-of-cure conditions. Additionally, panels with various starting conditions were run. Sound speed was calculated using the panel thickness divided by the measured transit time.

The goal of this work was to design and implement a noncontact, nondestructive method for evaluating interlaminar bonding during in-situ consolidation of composites. A sensor which detects poorly bonding areas in the topmost ply was developed. This sensor consists of two piezoelectric transducers mounted in a 'pitch-catch' arrangement. Plate waves and Rayleigh surface waves were generated by orienting the pitch transducer at an angle. Received signals were analyzed for frequency shift, frequency filtering, attenuation and wave speed to develop a criteria for determining poorly bonded areas. Poorly bonded specimens were manufactured and evaluated by the proposed non destructive test method. After undergoing nondestructive evaluation, the specimens were mechanically loaded to failure and the bond strength recorded. Nondestructive test predictions of bond strength will be compared with mechanical tests of bonding. Data will be presented which demonstrate the poor bond identification criteria.

Optical fiber gratings have recently emerged as attractive sensors for non-destructive evaluation of materials and structures. We present photoinduced Bragg and long-period gratings (LPGs) for monitoring corrosion in aging infrastructure. These two sensors are described based upon fabrication techniques, sensing mechanisms, sensitivities, and cross sensitivities. It will be demonstrated that while Bragg gratings need to be prestrained to detect corrosion of metals, the modulation of the evanescent field of the cladding modes in-long-period grating can be employed for corrosion monitoring. It will also be shown that sensitivities of LPG-based corrosion sensors to ambient temperature fluctuations can be reduced significantly.

In this paper, an ongoing investigation of plate wave dispersion measurement as a technique for indirect determination of the elastic properties and thickness of electroactive thin film polymers is described. Three polymer films were tested: a 1 mm thick s-PMMA film, and 80 micrometers and 230 micrometers thick polyethylene terephthalate films. The dispersion curves are measured, and a numerical algorithm is applied to recover the thickness and elastic constants of these films. Preliminary results show that the technique can be a viable gauging tool for electroactive thin film polymers.

The need for better control of the vertical Bridgman growth of large diameter Cd_1-xZn_xTe alloy crystals has stimulated an interest in non-invasive sensor techniques. Since the electrical conductivity of Cd_1-xZn_xTe alloys decreases by a factor of five upon solidification, in situ eddy current sensing has been explored to detect the onset of solid nucleation and monitor the early stages of crystal growth. An electro-magnetic finite element study was used to predict the sensor's response to the creation and movement of a liquid-solid interface and develop an analysis protocol to track the position of the interface with time. A non-invasive, high temperature eddy current sensor was then constructed and installed in a 17-zone production scale vertical Bridgman furnace. Several growth runs were monitored and the resulting eddy current sensor data was used to characterize the initial metal state, detect the onset of nucleation and determine the interface;'s growth velocity. The data provide the first direct evidence of extensive melt undercooling and spontaneous nucleation from fully melted charges. These results can be used to redesign the growth process and enable sensor-based manufacturing approaches for semiconductor crystal growth.

New non-invasive solid-liquid interface sensing technologies are a key element in the development of improved Bridman growth techniques for synthesizing single crystal semiconductor materials. Laser generated and optically detect ultrasonic techniques have the potential to satisfy this need. Using an anisotropic 3D ray tracing methodology combined with elastic constant data measured near the melting point, ultrasonic propagation in cylindrical single crystal bodies containing either a convex, flat, or concave solid-liquid interface has been simulated. Ray paths, wavefronts and the time-of-flight (TOF) of rays that travel from a source to an arbitrarily positioned receiver have all been calculated. Experimentally measured TOF data have been collected using laser generated, optically detected ultrasound on model systems with independently known interface shapes. Both numerically simulated and experimental data have shown that the solidification region can be easily identified from transmission TOF measurements because the velocity of the liquid is much smaller than that of the solid. Since convex and concave solid-liquid interfaces result in distinctively different TOF data profiles, the interface shape can also be readily determined from the TOF data. When TOF data collected in the diametral plane is used in conjunction with a nonlinear least squares algorithm, the interface geometry has been successfully reconstructed and ultrasonic velocities of both the solid and liquid obtained with reconstruction errors less than 5 percent.

We describe a novel technique to measure in situ, simultaneously, temperature and thin film thickness during semiconductor processing. The measurement is based on the principle that the velocity of an ultrasonic Lamb wave propagating in a silicon wafer is a function of both the wafer temperature and the thin film coating on the wafer surface. Because sensitivities of Lamb wave velocity to temperature and film thickness change differently with frequency, with a simple linear inversion method, we are able to obtain both the processing temperature an film thickness simultaneously with two sets of sensors operating at two distinct frequencies, 0.5MHz and 1.5MHz. This technique is demonstrated in an aluminum sputtering system. We have achieved a temperature measurement accuracy of +/- 0.15 degree C and an aluminum film thickness resolution of +/- 170 angstrom. The measurement does not depend on the optical or the electrical properties of either the wafer or the film materials, and is insensitive to the processing environment. With its high measurement accuracy and setup simplicity, this sensor system carries great potential in semiconductor process monitoring and control.

A simple and very accurate method for measuring the viscosity of liquids is presented. A vibrating lead zicronate titanate (PZT) ceramic polycrystalline resonator is totally immersed in a liquid and the oscillation behavior is studied both analytically and experimentally. The vibrating ceramic generates a shear wave traveling in the surrounding fluid normal to the surface of the resonator with heavy damping. The PZT is modeled as a vibrating thin plate. The resulting 1D governing equation of motion, which includes the effect of damping, is solved with the appropriate damped boundary conditions using impedance methods. The resonance frequency of a PZT immersed in a fluid is shown to be a function of the PZT parameters and the product of the fluid density and viscosity. Fluid loading is shown to lower the resonance frequency of the ceramic and both diminish and broaden the impedance plot near resonance. Unlike previous methods utilizing crystal shear-mode resonators, this method is valid for both low and high viscosity values. The proposed method provides viscosity values within 10 percent accuracy compared to tabulated values. The current study also provides an equivalent circuit model for the PZT in fluid loading. Immersing the PZT in a liquid increases both the inductance and the resistance of the unperturbed ceramic. The calculated elements of the equivalent circuit compare well with the values obtained using a best-fit statistical model.

In this age of globalization, market competition has made many steel companies become more customer focused which has led to a re-evaluation of their production capabilities. This push for more competitive, flexible and higher quality products has forced steel companies to invest in new process technology and to improve existing process control capabilities. This has led to new sensor initiatives and opportunities and as a results there is a need and a trend to move as much of the off-line testing on product characteristics, to the on-line environment. This has been almost impossible in the past, however due to the advances in opto-electronic technology, especially the laser, new sensors have been developed and applied to these technology, especially the laser, new sensors have been developed and applied to these difficult measurement problems. This paper will outline some of the opportunities and process sensor initiatives which are underway in the North American Steel Industry.

A transmission x-ray diffraction (XRD) technique has been developed which may be used, in real time, to locate the molten metal-solidifying metal interface in single-crystal castings. We proved feasibility of the sensor on samples of aluminum and copper in a gradient furnace, and found that the liquid-solid boundary could easily be identified even though the samples were surrounded by a mold wall and encased in a furnace. Subsequently, we have successfully attached the XRD sensor to a small industrial turbine blade casting furnace. The liquid-solid interface can be identified and followed, in real-time during the single- crystal casting process. The high energy x-rays permit in- furnace transmission XRD to be performed on a 6 mm thick nickel alloy specimen. The diffraction pattern was clearly seen, even though the entrance x-ray and diffraction paths through the furnace included 20 mm of Pyrex, 3.2 mm of molybdenum, 9 mm of aluminum oxide, and 12.8 mm of mold material. The x-ray source to imager distance was 1180 mm. An analytical model for transmission XRD has been developed. It is useful for assessing the feasibility of particular sensing applications.

A sensor has been developed and tested that is capable of emitting and receiving ultrasonic energy at temperatures exceeding 900 degrees C and pressures above 150 MPa. The sensor is based on a unique form of aluminum nitride that retains tits piezoelectric properties at high temperatures. The sensor works with standard ultrasonic pulse-receivers and has demonstrated the capability of measuring workpiece deformation during hot isostatic pressing (HIP). Details of the sensor design, performance, and coupling of the ultrasound to the workpiece are described. Ultrasonic data acquired by the sensor, in situ, during HIP runs and at elevated temperatures in air are presented.

On-line ultrasonic monitoring of polymer injection molding and aluminum die casting are presented. The flow front of molten polymer and aluminum inside the mold has been proved by a multiple-channel acquisition system with a time resolution up to 1 ms. This information may be used to control the plunger movement. The gap development, due to the shrinkage of the part in the mold, and the part solidification are also monitored for the understanding of the cooling process. As expected, it is observed that thicker sections take longer times to solidify. For injection molding, the relation between the gap formation time and packing pressure has been investigated. Since the temperature of molten aluminum is around 700 degrees C, ultrasonic waveguides are inserted into the die for the monitoring.

In order to monitor the temperature at the exit end of a hot rolling mill, the Aluminum Association and NIST entered into a Cooperative Research and Development Agreement to use the sheet itself as the basic element of a resistance thermometer. The non-contacting requirement can be satisfied by using eddy current techniques, and the temperature can be deduced from the basic relationship between electrical resistivity and temperature. To convert the measured resistivity to temperature, the temperature dependence of the resistivity of pure aluminum is obtained from laboratory calibration measurements and a temperature independent contribution characteristics of the alloy being produced. The latter is determined from the nominal alloy composition or by making a direct measurement of the resistivity and the temperature at an upstream location when the particular alloy being processed is temporarily held stationary for a contact thermocouple measurement of its temperature. The results of on-line measurements with the eddy current noncontacting thermometer in an operating rolling mill are discussed. These measurements consist of data taken from an entry eddy probe, a contact thermometer, a precise resistivity meter, an exit eddy probe, and a thickness gauge. The entry eddy probe was designed, built, and calibrated by the NIST.

Nondestructive inspection (NDI) technology is more valuable in automotive applications when used to establish and maintain process control and optimization by providing rapid feedback of inspection data after each critical process step than when it is used to 'control quality' by screening out defective product. Whether characterizing materials by nondestructive evaluation, detecting flaws by nondestructive testing, or inspecting assemblies or surfaces for dimensional conformity, the wide range of operationally simple, rapid, cost-effective NDI technologies available should be applied early in the mass production manufacturing sequence where added value is minimal and where rapid feedback supports achieving and maintaining process quality. Automotive needs for inspection technologies and examples of NDI technologies that meet the requirements and constraints of the automotive industry will be discussed.

NIST, in joint venture with a manufacturer of automotive air-bags, investigated and developed a system using EMATs to test all production parts and to reject weak welds in them without slowing the production line. After qualification tests were completed, the transducers and associated instrumentation were packaged for operation under mass production conditions in a factory environment by a commercial supplier of EMAT systems. This system was designed to inspect parts immediately after the weld stage while they may still be hot from the welding process.

High precision manufacturing is dependent on the accurate positioning of the part prior to each processing step. The part is typically held in a transfer fixture which may be used either simply as a part holder or as an alignment reference. A typical application is explored in this work, grinding of slots in a thick ceramic wafer mounted on a part fixture. A 1 micron slot is located with a position tolerance of 10 microns in the nickel-zinc-ferrite wafer. Part location is determined by means of a 50.8 by 1 micron target deposited onto the ceramic during an earlier process. In the current process, the target is magnified by a 250X vision system and the machine operator manually aligns the part using a set of cross hairs overlaid on the image. A high precision x-y stage is used to adjust the part location. However, the use of a fixed focal distance camera combined with part mounting variation results in an unfocused image for the operator. Manual alignment of the unfocused image leads to target location error during centering of the target in the cross hairs. The misalignment, in turn, results in process variation. The location of the slots varies based on alignment and reduces the process capability. To reduce process variation, an automated target location algorithm has been applied. The algorithm uses template matching to detect the target. This simple algorithm has been shown to locate the target within the required tolerance in spite of image blur. Using low cost processing, the system is able to determine the target location in real-time. For real-time control, the algorithm must determine the x-y coordinate of the target in 10 seconds or less. This effort shows the potential for a simple location algorithm to be implemented in a manner which can significantly decrease process variation in a precision fabrication process.

Digital Radiography (DR) and Computed Tomography (CT) imaging has historically has been used to evaluate parts for indication of density variation The images were displayed on a workstation and were evaluated for flaws and non-conforming indications. The next step was to perform elementary measurements, statistic, graphical, etc. by operating on the digital data using the computer. Finally, the complete 3D model was constructed from contiguous CT images to defines the part in 3D. Since this is the 3D definition of the part, the next logical step is to extract geometry definition similar to a CAD model. GE has developed algorithms and methods to obtain geometry definition of parts using both Digital Radiography and Computed Tomography x-ray inspection techniques (referred to as X-ray Metrology). CT imaging yields a complete 3D model of the part with a sacrifice of time, whereas multiple DR (2.5D) imaging is acquired must more rapidly with a sacrifice of volumetric information. Where the characteristics can be defined with 2.5D, this method can be used in more nearly real time applications. Originally, GE used X-ray Metrology information to reverse engineer the part where only partial CAD data exits To completely reverse engineer a part, extensive manual labor is required if the geometry is complex as for the turbine blade. As more parts are being designed using 3D solid modeling, there will be less need for reverse engineering. But, X-ray Metrology can have a very important role in part development and process control. GE is successfully using X-ray Metrology to extract part geometry and perform sampling process monitoring. X-ray Metrology provides geometry definition of the part both inside and outside with out destroying the inspected part. The increased computer system performance has enable the rapid generation of large x-ray data set from image processing. In some cases, commercially available software has enabled manipulation of the x-ray data to assist in filtering the data into process control formats.

Computed tomography (CT) has been shown to be an excellent nondestructive evaluation tool for measuring internal and external dimensions of manufactured components. Recent advances in CT-based metrology allow for CT data to be processed efficiently to produce full 3D models of scanned parts. This paper will talk about a number of applications for this technology including linking CT with rapid prototyping methods, using CT and rapid prototyping to produce rapid tooling, using CT as a metrology tool in a production environment, and linking CT data with engineering analysis. The paper will provide an overview of the current state of the art in applying CT-based metrology to manufacturing applications, will discuss actual application case studies, and highlight areas for future work in this area.

The next century will witness at least two great revolutions in the way goods are produced. First, workers will use the medium of virtual reality in all aspects of marketing, research, development, prototyping, manufacturing, sales and service. Second, market forces will drive manufacturing towards small-lot production and just-in-time delivery. Already, we can discern the merging of these megatrends into what some are calling agile manufacturing. Under this new paradigm, parts and processes will be designed and engineered within the mind of a computer, tooled and manufactured by the offspring of today's rapid prototyping equipment, and evaluated for performance and reliability by advanced nondestructive evaluation (NDE) techniques and sophisticated computational models. Computed tomography (CT) is the premier example of an NDE method suitable for future agile manufacturing activities. It is the only modality that provides convenient access to the full suite of engineering data that users will need to avail themselves of computer- aided design, computer-aided manufacturing, and computer- aided engineering capabilities, as well as newly emerging reverse engineering, rapid prototyping and solid freeform fabrication technologies. As such, CT is assured a central, utilitarian role in future industrial operations. An overview of this exciting future for industrial CT is presented.

In the current climate of reduced Military spending and lower commercial demand for aerospace products, it is of critical importance to allocate scarce technology development resources to meet projected needs. During the past decade, dramatic advances in x-ray nondestructive evaluation (NDE) technology have results in commercially viable digital radiography (DR) and computed tomography (CT) systems. X-ray CT has become an important NDE technique that not only provides data about material integrity, but also valuable volumetric data which is finding applications in reverse engineering, rapid prototyping, process control and 3D metrology. Industrial DR and CT systems have been available for almost 10 years, but are very costly, generally designed for specific applications and have well known limitations for both process development and final inspection. They have inadequate energy/flux to penetrate many large components and structures. In order to support the US Aerospace Industry in its drive towards global competitiveness, it is imperative that key enabling tools such as DR and CT be improved, made affordable, and implemented to meet the anticipated needs of the next decade of aerospace applications. This paper describes a strategy for a consortium of suppliers and users of x-ray NDE systems, academia and national laboratories to work together to attain this goal.

Weld breaks of steel coil during cold rolling and continuous pickling operations are a significant source of lost productivity and product yield. Babcock and Wilcox Innerspec Technologies has developed a weld process control system which monitors the key variables of the welding process and determines the quality of the welds generated by flash butt welding equipment. This system is known as the Temate 2000 Automated Flash Butt Weld Inspection and Weld Machine Diagnostic System. The Temate 2000 system utilizes electro- magnetic acoustic transducer (EMAT) technology as the basis for performing on-line, real-time, nondestructive weld quality evaluation. This technique accurately detects voids, laps, misalignment and over/under trim conditions in the weld. Results of the EMAT weld inspection are immediately presented to the weld machine operator for disposition. Welding process variables such as voltage, current, platen movements and upset pressures are monitored and collected with the high speed data acquisition system. This data is processed and presented in real-time display to indicate useful welding process information such as platen crabbing, upset force, peak upset current, and many others. Alarming for each variable is provided and allows detailed maintenance reports and summary information to be generated. All weld quality and process parameter data are stored, traceable to each unique weld, and available for post process evaluation. Installation of the Temate 2000 system in a major flat rolled steel mill has contributed to near elimination of weld breakage and increased productivity at this facility.

Ever-increasing diversity of civilian aircraft inventory and continued technological advancements in aircraft materials, aircraft flight control equipment, testing equipment, and software methodologies are impacting aircraft inspection and maintenance practices. Current procedures deal mainly with issues related to structural and electrical or electronic integrity to assure continued airworthiness of operational aircraft. Techniques and methodologies for these are widely available, and training needs are well defined. Advances in technology, however, are yielding new and different aircraft, which require more sophisticated electronic instruments for navigation and control.A major issue is the continued reliability and airworthiness of avionics and development of adequate safeguards for these aircraft. Built-in test equipment, maintenance across terminals, and data bases defining inspection needs that are based on operational data, and software integrity, are also rapidly becoming important considerations in aircraft maintenance. In this era of declining funds and personnel resources, a cost-effective approach requires a fresh look at all phases of the current inspection and maintenance practices, including oversight and management. This paper provides a perspective on issues and challenges facing a civilian regulatory agency, specifically, the aircraft maintenance division in the FAA.

The highly anisotropic elastic properties of the plies in a composite laminate manufactured from unidirectional prepregs interact strongly with the polarization direction of shear ultrasonic waves propagating through its thickness. The received signals in a 'crossed polarizer' transmission configuration are particularly sensitive to ply orientation and layup sequence in a laminate. Such measurements can therefore serve as an NDE tool for detecting layup errors. For example, it was shown experimentally recently that the sensitivity for detecting the presence of misoriented plies is better than one ply out of a 48-ply laminate of graphite epoxy. A physical model based on the decomposition and recombination of the shear polarization vector has been constructed and used in the interpretation and prediction of test results. Since errors should be detected early in the manufacturing process, this work also addresses the inspection of 'green' composite laminates using electromagnetic acoustic transducers (EMAT). Preliminary results for ply error detection obtained with EMAT probes are described.

In this paper the bonding area of silver soldered tungsten cemented carbide bits was evaluated nondestructively by using electric potential and ultrasonic methods and was compared with the bonding strength measured by shearing off test. In the electric potential method, voltage was measured by changing a distance of electric terminals which were connected across the bonding plane. In the ultrasonic method, a transducer was attached to a lubricated tip surface and the amplitude of back surface echo signals was measured. It was concluded that the electric potential method is considered to be applicable as a primary nondestructive inspection of the bits by improving the configuration of tip of the terminals and applying constant contact pressure. The ultrasonic method can be used to certify the caught bits in a net of the primary inspection.