Phase shifting approaches represents important tools in whole field photoelastic analysis. There are many ways to change the phase of a photoelastic pattern. In this work one uses a four images method that requires only a plane polariscope and frame-grabber devices. Phase unwrapping algorithm, together with image processing routines, such as filtering blurring and region of interest processing are used to process photoelastic data. An application to a disc under compression were made.

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In recent years, shearogrpahy has significantly improved capabilities in the areas of unbond and separation detection in tires. Although shearography has many advantages for qualitative evaluation, the technique remains the problem of quantitative analysis of inside defects, because shearography needs several effective factors including the amount of shearing, shearing direction and induced load, which exist as barrier for the quantitative analysis of the inside defects. Since the factors are highly dependent on inspector's skill and also affect the in-situ workability. The factors were optimized and the size of cracks inside of pipeline and tire has been quantitatively determined.

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In the present study model photoelastic technique has been employed to determine dynamic stress distribution in a simply supported beam with over-hangs. The ratio of weight of the beam between supports and the weight of the striker was kept constant (2.675). A Fastax framing camera operating 12,000 frames per second has been employed to record the dynamic fringe photographs. Typical collision velocity of the striker was 1.6 m/s. Keeping the overall length of the urethane rubber beam (253 mm x 24.3 mm x 12.5 mm thick) as constant, the locations of the supports have been changed (for 90 mm, 120 mm and 150 mm spans) to generate different over-hang ratios. A freely rolling mass was employed to induce a low velocity impact at central and quarter spanlocations of the beam. The mass of the striker was varied between 10.5 to 17.5 gms. The contract force history generated by the impact was measured by using a suitable force transducer. Unfavourable boundary stress distribution for a beam span has been identified.

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By measuring stresses in cylinders with no stress gradient in axial direction, the cross-section of the cylinder may be considered as consisting of concentric rings in each of which the stresses are constant. Axial stress distribution in the cylinder is determined stepwise starting with the outermost ring (the so-called onion-peeling method). This paper generalizes the onion-peeling method for the case of axisymmetric stress distributions when stress gradient in the axial direction is present. Measurement of the integrated isoclinic and optical retardation is carried out in two parallel sections which are perpendicular to the specimen axis, Δz apart from each other. The distributions of the axial stress and shear stress are determined directly from the measurement data, using linear approximation of integrated photoelasticity. Other stress components are determined using the equilibrium equation and the compatibility equation (if stresses are due to external loads) or using the generalized sum rule (if residual stresses in glass are measured). The method is less sensitive to measurement errors than the Abel inversion. In comparison with the polynomial approximation of the stress distributions, the onion-peeling method gives more adequate results if stress distribution is not smooth. The paper is illustrated with several applications.

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Most of the methods of contemporary experimental mechanics permit measurement of the stresses and strains only on the surface of the test object. Photoelasticity gives the possibility to investigate non-destructively also 3D stress fields. However, in the general case photoelastic tomography is very complicated due to complicated optical phenomena which occur when polarized light passes a 3D inhomogeneous and birefringent medium. In linear approximation, from the equations of integrated photoelasticity two integral equations can be derived which relate photoelastic measurement data with integrals of certain components of the stress tensor. Using these equations, Radon transform of a component of the stress tensor can be expressed through the tomographic photoelastic measurement data. That opens the possibility to determine normal stress distribution in an arbitrary section of a 3D test object using Radon inversion. Linear approximation is valid when either birefringence is weak or rotation of the principal stress axes is small. The method is realized with a computer-controlled photoelastic polariscope supplied with a rotating device. Application of the method is illustrated by several examples of residual stress measurement in glass articles.

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Inclusion causes an accidents. Structures have inclusions, which cause stress in Abstract material. Crack occur in the material due to high stress concentration. Cracks is developing gradually, which can cause the structure to be destroyed. It have study by calculation found about inclusions. But, study by experiment can't be found. This study explained problem in the tensile load. Test specimen models prescribed by a japanese industry standard was used in photoelastic method. Elliptic inclusion is in center of test specimen models. This study used test specimen models made by a numerically controled machine tool. Test specimen models is high precision. Test specimen models has annealing given after cutting by electric furnace. This study used photoelastic method, method of caustics and finite element method.

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Shadow optical method of Caustics has been applied in order to measure thermal stress distribution around a cylindrical heater inserted in a thin disk of acrylic. Caustics pattern has a circular shape centered to the heater. Caustics pattern appears at a certain stress value then increases in diameter (Caustics Size). As soon as heating process goes to its steady state, Caustics pattern movement goes slowly then stops. A strong relation between Caustics pattern size and position of the highest value of the radial thermal stress has been founded. Also theoretical Caustics pattern size equation has successfully obtained. The comparing between the behavior of Caustics pattern movement and thermal stress distribution as well its behavior during heating process engages us to conclude that Caustics experiment method could be used to measure thermal stress gradient.

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In this study, stress intensity factors were investigated and determined by the caustics and the photoelastic methods to clarify behaviors of crack tips under various biaxiality ratios. The polycarbonate plates with isotropy property and ones with anisotropy property were used as the specimens. As a result, it was confirmed that only "K_I" was generated regardless of biaxiality ratio, and material's property in case of the crack angle θ=0°. It was also confirmed that only K_I was generated in the isotropic polycarbonate plate with crack angle θ=45° under the biaxial load (1:1). In the case that the biaxiality ratio is more than 1:1 with crack angle θ=45°, both K_I and K_<II> are simultaneously generated in the isotropic specimens. Furthermore, the stress intensity factor, K_I, K_<II> values are influenced most by the extrusion direction in the case of the anisotropic specimens with the biaxiality load ratios exceeds 3.0.

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Shearography provides whole-field derivatives of displacement. In many plate-bending problems, stresses are proportional to curvatures. A novel digital scheme is proposed to digitally shear the shearographic fringes to obtain second derivatives or curvature contours over the whole field. Since differentiation is noise-prone, a novel filtering approach is proposed to obtain good results. Examples of the method for different shear amounts are shown to reveal the advantages and capabilities of this approach.

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Thermal deformations of a newly developed electronic package, Stacked-MCP (Multi Chip Package), were measured by phase-shifting moire interferometry. This method was developed using a wedge-glass-plate as a phase shifter to obtain the displacement fields with the sensitivity of 30 nm/line. This technique also made it possible to determine the strain distributions quantitatively. Thermal loading was applied from room temperature 25℃ to two states of elevated temperatures 75℃ and 100℃, and the thermal strains were then examined. The results showed that the normal strain ε_<xx> concentrated at the ends of two silicon chips, and the transverse strain ε_<yy> enlarged between the two chips. The shear strain γ_<xy> grew at the end of the lower chip to 0.30 % from 0.17 % when the temperature increased by 25℃.

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A simple, fast and accurate technique for direct detection of 3-D shape of rotated objects based on light line projection is presented. This technique is proved by simulation and experimentally verified. To obtain the surface shape, the object is rotated at an angle with an electromechanical device. In each rotation, the object is scanned by a light line. To determine the surface data, disturbs of the light line are measured on a reference point and on the object surface. This line displacement is measured by Gaussian approximation, which corresponds to the intensity model of a light line. In this technique, the rotation angle and origin are calculated by recognition of a light line pattern. Recognition method uses Hu Invariant Moments to detect light line pattern. A set of images is processed to obtain the complete 3-D shape. Also, the necessary time for processing a light line by using this method is presented. This echnique is tested with real objects and its experimental results are presented.

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A high-precise measurement method using a digital image correlation method combined with a fine adjustment stage is proposed for the purpose of the thermal deformation measurement of small parts like the electronic devices. An object mounted on the fine adjustment stage is made to move parallel to the in-plane of the object surface at the displacement magnitude of the sub-micron and the images of the object surface are taken by a CCD camera. Calibration curves of the horizontal or vertical displacement vs. transfer pixel of the every pixel point of image are made by using the obtained images. In the case of disregarding out-of-plane deformation, it is possible to carry out the high-precise in-plane displacement distribution measurement using the calibration curves. As an application, the deformation of a driving electronic package is measured using this system.

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Moire topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by moire topography has been required since the method was frequently applied to the engineering and medical fields. The 3-D measurement using projection moire topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using the two-wavelength methods of projection moire topography was tested to a measuring object with 2pi-ambiguity problems. Also, rapid measurement can be accomplished by the synchronization between CCD camera and projector. The experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the 2pi-ambiguity problems can be effectively overcome so as to treat large step iscontinuities in measured objects.

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This study deals with the measurement of the two-dimensional deformation of wood joints under compressive loads using an electronic speckle pattern interferometry (ESPI) technique. A mortise and tenon joint and a dovetail joint of western hemlock are used as specimens. Results reveal that a large two-dimensional deformation of the wood joints can be measured using the ESPI technique, the deformation values significantly vary with parts, and the accuracy of the fabricated wood joints has a significant effect on the two-dimensional deformation of the wood joints.

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The measurement of the deformation of sheets of recycled paper subjected to tensile loads is measured using an electronic speckle pattern interferometry (ESPI) technique. Specimens with fibers, which constitute a sheet of paper, parallel and perpendicular to the direction of paper making are used to investigate the effect of the arrangement of fibers on the tensile property. The deformation of recycled paper is compared with that of virgin pulp paper. Results reveal that the directions of fibers, which constitute a sheet of paper, have a significant effect on the two-dimensional deformation of recycled paper, that the paper exhibits nonuniformity at a low tensile load, and that this nonuniformity is maintained until failure.

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High-speed holographic microscopy is applied to take three successive photographs of fast propagating cracks at the moment of bifurcation. The cracks are propagated in PMMA plate specimens at a speed about 660m/s. From the photographs, crack opening displacement (COD) is measured along the cracks as a function of distance r from the crack tips. The measurement results show that the CODs are proportional to √<r> before bifurcation. After bifurcation, the CODs of mother cracks are proportional to √<r>, however, those of branch cracks are not always proportional to √<r>. The energy release rate and energy flux toward crack tips are obtained from the COD data, and are found to be continuous across the bifurcation point.

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The main limitation of the electromechanical device such as accelerometer used to measure vibrations is that it may alter the vibration behaviour of the component due to change in stiffness of the vibrating object. Apart from other limitations, it is practically impossible to get the instantaneous mode shape of vibration over the surface of a structural element by the electromechanical devices. The Laser based optical techniques are non-contact type, have high sensitivity, wide dynamic range and allow measurements in a hostile environment. A typical laser based vibrometer can measure vibration frequency almost from DC to 20 MHz and amplitude from a nanometer to a higher values of the order of 10 mm. In this paper a review of laser interferometry, digital speckle interferometry / TV holography, and Talbot interferometry based opto-electronic techniques for measurement/monitoring of vibrations are discussed. Some experimental results obtained from these techniques are presented.

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A series of photoelastic experiments were performed in this paper to demonstrate the feasibility of modifying the classical Hertz contact theory to meet the practical needs. It was found that the match between the experimental and theoretical results was indeed improved by adjusting the contact half-length. Correction factor for accounting the boundary effects was also nvestigated. Furthermore, the replaced superposition method was successfully implemented to determine the contact stresses around a near-edge circular hole in a semi-infinite plate.

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A novel approach, called min-max scan, is proposed to measure the full-field principal stress directions digitally. By using a light-field plan-polariscope and a PC-based image processing system, the intensities of the model images under varying loads are scanned and compared in real-time to form images representing the minimum (isoclinics) and maximum intensities at each point on the model. The influence of isochromatics on the isoclinics is eliminated. Using two sets of images obtained at the angle of 0 and π/8, respectively, the full-field principal stress directions can be determined in the range [0, π/2]. Relevant theory for the proposed approach is introduced and the experiment results are shown.

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A fast propagating crack in a brittle material often bifurcates into two cracks when the propagation speed is high enough, about 650m/s for example. In the present study, two optical system of pulsed holographic microscopy are applied to take the photographs of rapidly bifurcating cracks in PMMA plate specimens. The photographs are simultaneously taken on both surfaces of specimen. The photographs show that some rapidly bifurcating cracks have apparently different shapes on the both specimen surfaces. Even in the case that the crack shapes are almost the same on the both specimen surfaces, the crack shapes are different near the bifurcation point. Crack opening displacements of branch cracks are measured from the photographs. The measurement result show that branch cracks have not always the same CODs on both specimen surfaces, even though they are thought to be through cracks. These facts indicate that the bifurcation of fast propagating cracks is not two-dimensional phenomenon but three-dimensional one.

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A new technique of moire interferometry for simultaneous measurement of two-dimensional displacement components is proposed. The Fourier transform phase-shifting method is used for the analysis of the phase distributions of superposed fringes obtained from four-beam interference. In order to analyze a frequency component, the sampling number should be bigger than twice of the frequency. In this paper, we propose a new method for analyzing with less data sampling. A phenomenon called 'aliasing' in which the original frequency appears at a different frequency is used. Furthermore, the influence of the random noise upon the phase distributions with and without aliasing is inspected by a computer simulation. As an example for experiment, the thermal deformation of an electronic device is analyzed using the proposed method and the effectiveness of the proposed method is shown.

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Structural components subjected to notched geometry often show localized yielding upon heavily imposed external loading. Accurate inelastic notch tip strains, required for reliable fatigue design and to prevent catastrophic failure, are frequently calculated by Neuber and Glinka approximations. It is well known that they are extremely efficient, in terms of reduced computational demands, but give poor accuracy because the approaches rely on simple implicit deformation plasticity. In this study, whole field optical measurement techniques, such as reflective moire interferometry and electronic speckle pattern interferometry (ESPI), are applied and compared with the notch-tip strain predictions proposed by Neuber and Glinka. Included are also results obtained by FEM analysis.

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The specimen materials used in this research are isotropic material, orthotropic material and bimaterials. The static photoelastic experiment was applied to them. And then the specimens used in photoelastic experiment were fractured under static load. The static photoelastic experimental hybrid method was introduced and it's validity have been assured. The static photoelastic experimental hybrid method was applied to the minimum strain energy density criterion (MSEDC) and the maximum tangential stress criterion (MTSC). And then, crack propagation criterion by the static photoelastic hybrid method was introduced. The theoretical initial angles of crack propagation were calculated using the crack propagation criterion introduced in this research. The experimental initial angles of crack propagation were measured from the fractured specimen. Comparing the experimental initial angles with the theoretical initial angles of crack propagation, the validity of the crack propagation criterion by the static photoelastic experimental hybrid method was assured.

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Failure in structure and machine component subjected to vibration generally takes place at natural frequencies at which amplitude of vibration becomes quite high. For failure analysis it is therefore important to understand the behaviour of component at natural frequencies. In this paper study of out-of-plane vibrations in square plate and tweeder by digital speckle pattern interferometry (DSPI) is studied and presented. For analysis of the DSPI fringes, speckle noise has to be removed. Removal of speckle noise in the speckle interferograms depends mainly upon texture and number of speckles present in the speckle interferograms. Our recent investigations show that a filtering scheme based on combination of average and Symlet wavelet filter and combination of Wiener and Symlet wavelet filter is effective in removing the speckle noise present in the speckle interferograms of vibrating square plate made of aluminum and tweeder surface made of diffused foil respectively. Experimental results are presented.

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In the case of phase-shifted grating projection method, there is a problem that the measurement error becomes larger when the object is moving more speedily. In order to solve this problem, we developed a DMD reflection-type CCD camera that we call a DMD camera. In this paper, we develop an algorithm to apply the phase-shifting method using correlation to the shape measurement using the DMD camera and high-speed phase-shifting method using the DMD camera. The four step phase-shift can be performed within 1/7,500 seconds because the pattern on the DMD can be changed theoretically 30,000 times in a second. The principle and the experimental result are shown.

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This paper views digital holography and digital shearography and their variations as a single optical technique having the same basic mathematical formulation and instrumentation. A key optical component used in both techniques is a doubly-refractive prism that combines two angularly separated laser rays to interfere at near collinearity, thereby producing interference patterns of very low spatial frequency that is resolvable by CCD cameras.

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Current trends in miniaturization of micro-electro-mechanical systems (MEMS) require the use of smaller and smaller components. Development of those micro-components requires test and measurement methodologies to inspect the deformations of the micro-components for further understanding of their mechanical behaviour. In this paper we have developed optical techniques for measuring deformation of micro-components. As a result of light interference on the component surface various fringe patterns are observed. The fringe patterns which contains information on the component's surface deformation or characteristics are captured with CCD camera incorporated with a microscopy system. The experimental work carried out on various micro-components including micro-beam, microphone, micro-radio-frequency (RF) switch and micro-mirrors. The proposed methods are potentially applicable to in situ inspection of micro-components in MEMS.

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A phase shift technique is proposed to analyze closed-fringe patterns. This technique requires two fringe patterns to calculate wrapped phase data, where there is a π/2 phase shift between the two patterns. Fourier transform is applied to transform each of the fringe patterns into frequency domain. Then a filter is designed to remove low frequency and high frequency components that correspond to unwanted background and noise of the fringe patterns. After filtering, two frequency spectra are inverse transformed to spatial domain and a wrapped phase map is calculated from two real parts of the inverse Fourier transform. Finally, a continuous phase profile is retrieved from the wrapped phase map. This paper represents the principle of the proposed method, discusses different filters' effects on the recovered phase data and tests the validity of the proposed method on real interferograms obtained by Electronic Speckle Pattern Interferometry as well as computer-simulated fringes.

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In order to obtain some insight into the three-dimensional effects on the crack growth behavior, a series of experiments on centrally perforated cylinders under internal pressure were conducted using the frozen stress methods. The inner surface of the cylinder has a star shape, which consists of six fins. Part-through cracks were cut at different locations near the fin tip region. The effect of crack location on the crack growth behavior and the role of shear modes during crack turning were investigated and the results are discussed.

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Lamb waves are normally utilized for inspecting thin metal sheets. Wheel-type probes using piezoelectric oscillators have generally been used as the sensors for Lamb waves. Recently, an electromagnetic acoustic transducer (EMAT) has been developed and is beginning to be used as a Lamb wave detector. The EMAT offers the advantage of inspection without using a couplant. The EMAT generates Lamb waves with fixed wavelengths determined by the interval between the meander lines in the sensor coil that constitutes the EMAT. We have studied an EMAT consisting of a meander line coil with intervals from 1mm to 4mm and having a paired structure symmetrically embraced with a thin steel sheet on opposite sides. The EMATs generate S_0, A_0, S_1, A_1-mode Lamb waves with different wavelengths corresponding to the resonance frequency range from approximately 0.5MH to 2MHz. We confirmed how to properly generate a symmetrical or anti-symmetrical Lamb wave.

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Repeated plate impact tests on medium carbon steel were carried out on the identical target plate being impacted by the flyer plate of the different thickness in each impact tests. Evolution of spall damage under repeated impacts was evaluated nondestructively with the B- and C-scan images by low frequency scanning acoustic microscope as well as the ultrasonic variables (ultrasonic velocity, amplitude ratio of B2 to B1 echo and backscattering intensity). The spall damage density and sizes after the second impact have increased in the impact surface side, when the second impact stress is lower than the first. On the other hand, when the second impact stress is higher than the first, the spall damage have increased in the back surface side. The change in B- and C-scan images of the spall damages under repeated impact are well correlated with the change in ultrasonic variables. These methods give us an advanced means to evaluate nondestructively spall damage and to make clear the mechanisms of the spall damage growth under repeated impacts.

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Aluminium alloy (A2024-T3) plates with curved sides were subjected to the low-cycle fatigue testing under conditions of a stress ratio of 0.05 and a frequency of 0.001 Hz. At an early stage of the fatigue process, the ultrasonic wave was measured. A new real-time measurement method of local immersion was developed by using a water bag to measure the ultrasonic wave. Measured wave was analyzed through fast Fourier transformation (FFT) to obtain the ultrasonic parameters, such as the peak intensity and the average gradient of the transfer function. Relations between the measured ultrasonic parameters and the measured local strain were examined during one cycle in the early stage of low-cycle fatigue testing. In one cyclic loading, the propagation time of the ultrasonic wave from the surface to the bottom of the specimen sinusoidally changed with time corresponding to the strain change of the specimen. The peak intensity and the average gradient of the transfer function of the bottom echo tended to sinusoidal change with time during arbitrary one cycle. The influences were discussed of the acoustoelastic velocity change and the change in the focal position of the transducer following deformation of the specimen on the propagation time of the ultrasonic wave.

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The influence of the contact pressure on the ultrasonic wave propagation along the contact interface between two solids has been studied experimentally. In this study, the contact interface wave is generated and received for mated polymethyl methacrylate (PMMA) blocks, aluminum blocks and copper blocks under different contact pressures. The measurement has shown that the propagation velocity of the contact interface wave increases from the Rayleigh wave velocity to the bulk shear wave velocity as the contact pressure is increased. Spectral analysis has been performed to obtain the phase velocity of the contact interface wave as a function of the frequency and the contact pressure. The tangential stiffness of the interface has been also identified, which is shown to increase as the contact pressure is increased. The contact interface wave velocity and the interface stiffness are found to be very sensitive to the contact pressure, and expected to offer a promising possibility to evaluate the contact conditions nondestructively.

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The oxidation damage is one of the crucial factors to degrade mechanical properties of graphite components in the HTGRs. It is important to estimate the inner porous conditions of the graphite which strongly affect the mechanical properties. A new non-destructive evaluation method was developed to estimate the conditions by an ultrasonic wave propagation analysis. An evaluation model was proposed in order to determine the value of the Young modulus for an ideal graphite polycrystals without pore which is an important factor in the analysis to evaluate the apparent Young modulus for porous graphite. It was shown that the apparent moduli for isotropic porous graphites are evaluated appropriately by using the analyzed values of the ideal polycrystals. The evaluation model is available to evaluate the modulus for anisotropic graphite by considering anisotropy and pore shape precisely. It suggests that it is possible to estimate the porous conditions of the graphite components by the developed method, provided that their apparent Young moduli are experimentally measured. This new method is promising to evaluate the oxidation damage of the graphite components and it has a potential to estimate other material properties which highly depend on the porous conditions, by non-destructive way.

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The theoretical basis of a relatively simple method for nondestructive evaluation (NDE) of inhomogeneous prestress in materials is proposed. The method is based on utilization of nonlinear effects of simultaneous propagation, reflection and interaction of two ultrasonic waves in the material. The phenomenon of amplification of nonlinear effects by wave interaction is utilized. An algorithms for qualitative and quantitative nondestructive characterization of two-parametric inhomogeneous prestress field in the material with two parallel boundaries is presented.

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Electromagnetic acoustic resonance (EMAR) is a contactless resonant method with an electromagnetic acoustic transducer (EMAT). This method is free from extra energy losses, resulting in the measurement of intrinsic ultrasonic attenuation in solids. In this study, the EMAR was applied to detect the creep damage of a Ni base superalloy (WASPALOY). The material was exposed to the temperature of 1073K at various stresses. We measured ultrasonic attenuation for 1-6 MHz frequency range as the creep advanced. The attenuation coefficient exhibits much larger sensitivity to the damage accumulation than the velocity. It shows a maximum around 40% of the whole life, which is interpreted as resulting from microstructural changes, especially, dislocation mobility. This is supported by TEM observations for dislocation structure. This technique has a potential to assess the damage advance and to predict the creep life of metals.

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A method to measure moisture in encapsulant resin of IC packages by microwaves was demonstrated, which can determine moisture directly without drying and weighing the packages. An coaxial line sensor acts both as a source and receiver of microwave signal that is transmitted into and reflected from the package. A frequency of 100 GHz was used to increase the measurement sensitivity. The relationship between the measured amplitude of the reflection coefficient and the moisture content in the packages was found to be linear. The amplitude difference, which is corresponding to the attenuation of microwave, in the cases of packages with and without moisture content increases linearly with the increase of the thickness of the resin above the chip pad. For any kinds of packages, if the thickness of the packages is the same, the moisture content can be determined by the microwave amplitude measurement after testing two reference packages; if the thickness of the packages is known, the proposed method can be used directly after measuring a dry package.

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In this paper, we show an effective transmission technique of higher frequency ultrasound into a wafer level package. The high quality acoustic image of an interface in the package can be acquired by the technique, and the package is not wetted by water during the acoustic imaging. The technique transmits the ultrasound through the polyvinyl chloride layer inserted between water and the package, and the pressure of about 0.1 MPa is applied to the interface between the layer and the package. Furthermore, by selecting the layer thickness as the layer can work as the acoustic matching layer between water and the silicon chip, the signal amplification for improving the signal-to-noise ratio and the signal modulation toward the higher frequency components for improving the spatial resolution are realized. In practice, we carry out the solder joint inspection of a wafer level package, and the detectability of the defective joint is improved remarkably by the present dry-contact technique as compared with the usual water immersion technique.

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By a grazing SH-wave acoustoelasticity method, we tried to separate the stress anisotropy and the material anisotropy of structural material and to measure the residual stress of it. It was however difficult to measure with high accuracy in acoustoelasticity measurements by the grazing SH-wave because the measurements are strongly affected by coupling medium and the roughness of the surface of the material. In this study, we have developed a new-type grazing SH-wave transducer in order to suppress those influences. The transducer consisted of two transmitters and four receivers. The performance of the new transducer was compared with an earlier grazing SH-wave transducer by measuring the wave velocity of a rolled mild steel plate using a sing-around unit. Wave velocity measured by the new transducer was not influenced by change in couplant thickness with the passage of time, and was almost constant. We have measured the change in stress of the steel plate in the accuracy of ±5 MPa by using the new transducer. It has been demonstrated that the new transducer would be useful for measurement of the residual stress in the surface region of materials.

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This paper first reviews recent development and application of laser ultrasonic techniques to the property and integrity evaluation of materials by the research committee organized in Japanese Society of Non-destructive Inspection (JSNDI) from 1998. These involve advances of both hard and soft wares in laser ultrasonic and application to advanced materials and industrial structures. Last portion of this paper introduces research results of acoustic emission (AE) and laser ultrasonic in my laboratory. These involves 1) simulation of artificial impact and fracture sources using pulse laser. 2) estimation of elastic stiffness coefficients of FRPs and unique source location method ofAEs. 3) estimation of elastic properties of sprayed thermal barrier coatings at elevated temperatures and 4) non-destructive estimation of interfacial quality of modified thin surface layers.

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The development of an ultrasonic on-line sensor for molten metals monitoring at temperature up to 1073 K is presented. This sensor consists of a piezoelectric transducer, a focused waveguide and a cooling system, and provides high spatial resolution measurements in molten metals in a pulse-echo mode at 5 or 10 MHz. A taper-shaped clad buffer rod is used as the waveguide. The length is up to 500 mm. Using the developed sensor, pulse echo measurements have been successfully performed in molten magnesium (Mg) at 973 K and aluminum (Al) at 1073 K. For molten Mg measurements, the sustainability for long time operation has been evaluated. The martensitic stainless steel is chosen as the sensor material, and no crucial corrosion has been observed in the sensor surface through 32 hours immersion test. An attempt has been made to detect alumina particles of 160 micron suspended in molten Al. Backscattered echoes from the particles are clearly observed at the focal region of the acoustic lens with a 4.4 mm radius. A numerical simulation has been used to examine the behavior of the ultrasonic echoes from the particles.

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A laser ultrasonic method has been developed for inspection of hot-clad aluminum/steel interface. Because of high temperature, the conventional contact or immersion ultrasonic testing is not applicable for this purpose, therefore, non-contact nondestructive testing is required. Among non-contact ultrasonic methods, the laser ultrasonic method has relatively high S/N ratio and spatial resolution. Line-focused YAG pulse laser excites many ultrasonic waves on the plate surface. Beyond a certain distance from the irradiated area, only the Lamb waves of various modes prevail than other modes of waves. A broadband laser interferometer detects the out-of-plane displacement of many kinds of the Lamb waves. The received time-domain signals are superposition of the waveform of the individual Lamb wave, therefore, identification of interface delamination of aluminum/steel clad pate is difficult. We propose a new laser ultrasonic method for detecting interface delamination of hot-clad aluminum/steel plates with the group velocity dispersion of the Lamb waves. By apply the wavelet transformation on the received time-domain signals, we calculate the group velocity dispersion curves of several Lamb wave's modes. The dispersion curves agree well with theoretical dispersion curve of the defect-free clad plate. If some delamination appears within Lamb wave propagation distance, a noticeable distortion of the dispersion curve appears. By taking the differential of the dispersion maps of the intact and delaminated plate, we identify the delamination of the hot-clad plates.

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In combination with a universal eddy-current equipment G_<iant>M_<agneto>R_<esistance> sensors were used for the on-line monitoring of fatigue processes. The paper contains selected examples for the successful application of the GMR technique to different austenitic stainless steels as well as plain carbon railway wheel and tire steels under HighCycleFatigue-conditions at ambient temperature in servo-hydraulic testing systems. For the characterization of the cyclic deformation behavior furthermore the recording of mechanical hysteresis loops as well as temperature-measurements and voltage-measurements were used.

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Ultrasonic guided wave has a great potential in rapid long-range nondestructive evaluation for pipeworks. However, the wave motion in a pipe is very complex due to the multi-mode existence and dispersivity. Especially in a curved region of a pipe called elbow, there is no theoretical solution like the normal mode expansion in a straight pipe. A semi-analytical finite element technique is one of the most efficient techniques for calculations of guided wave propagation in a pipe because it does not require discretization in the longitudinal direction. In this study, the semi-analytical finite element method gives dispersion curves and wave structures for each guided wave mode. Then, wave propagations in a straight pipe and in a pipe with an elbow are shown. Moreover, experimental results show the potential of longrange pipe diagnostics with the low frequency and non-dispersive region of L(0,2).

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In this paper we shall describe some of our work in developing industrially viable non-contact ultrasonic measurements. For most materials, non-contact ultrasonic techniques are typically not as efficient at generating or detecting ultrasound as conventional contact methods. However non-contact methods can offer some distinct advantages over contacting methods including their suitability to a range of online measurements. This is because the measurements do not require an acoustic couplant and can be applied to hot or moving samples in hostile environments. These benefits also make the techniques suitable for automation and potentially give increased reliability. The methods described in the paper can and have been used in industrial environments or on industrial samples. The paper will concentrate on two of our research areas, the first being ElecroMagnetic Acoustic Transducers (EMATs) and the second being laser generation / detection of ultrasound. Operation principles of these two techniques will be discussed and illustrated by describing some applications of this technology to various testing problems.

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A new laser system to generate the focused Lamb wave using the arc array slit is proposed. In this system, spatially expanded Nd:YAG pulse laser is illuminated through the arc array slit on the surface of a sample plate to generate the Lamb wave of the same pattern as the slit. Then the generated Lamb wave is focused at the focal point of which distance from the slit position is dependent on the curvature of slit arc . The basic performance of the proposed method was predicted by simulations and verified by experiments. Especially in simulations, the effects of number of array and the slit width to the intensity at the focal point were investigated. The results of defect-detection experiments showed that the proposed method had better spatial resolution than the conventional line array slit in the detection of linear and circular defects on an aluminum plate.

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Real-time monitoring of a structural component gives information on the time and condition at which damage occurs, thereby facilitating the identification of the cause of the damage. Moreover, it enables timely repair, hazard mitigation and study of the damage evolution. This paper reviews the use of electrical resistance measurement to monitor damage in cement-based materials. This method is sensitive to even minor, microscopic and reversible effects. This paper addresses damage due to static/dynamic stress, freezethaw cycling, creep and drying shrinkage, in addition to the effect of strain rate on the damage evolution.

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In the coupling of oilfield tubes bonded by the amorphous bonding method, quality assurance techniques have been studied in process after process. During the bonding, an ultrasonic wave was propagated toward the bonding interface and the changes in the amplitude of reflection were monitored. As a result, the bonding processes including a phase transformation of the mother materials and the dissolution of filler material were identified. Using the information, measurement errors of a radiation thermometer can be corrected in real time and the bonding states of the local area of the bond can also be observed by the convergence nature of the ultrasonic beam. After the bonding, height of the steps at the interface, grain size and hardness of the heat-affected zone were evaluated by an ultrasonic method in addition to the conventional pulse echo inspection. As a result, 100% of defective joints, in which breakage had occurred by the expansion test, were distinguished.

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A main effort in the maintenance of high-rise buildings is to inspect external walls for tile separation. This paper reports a novel optical method known as sonic-shearography for detecting and assessing bonding integrity between the tiles and the external wall of buildings. The inspection process is non-contact and full-field, and it allows the size, shape and location of debonds to be determined. Being quantitative in nature, this technique enhances the efficacy of maintenance strategies for early prevention against falling tiles.

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The distribution of the sum of the principal stresses was obtained by the infrared stress analyzing system. The unknown boundary-values were estimated from the internal point information of an infrared stress image by a boundary-value inverse problem analysis, and the stress separation was carried out by a direct problem analysis using estimated boundary values. The truncated singular value decomposition (TSVD) method and the Tikhonov regularization were used as the optimization technique of boundary-value inverse problem analysis. As an optimization parameter determining method, the norm minimizing method was employed. Then, the stress separation was performed by the boundary-value inverse problem analyses based on error evaluation, the least squares method, and the 2-dimensional hybrid method proposed by Nishioka et al. Comparing the results obtained by three different methods to those of the 3-dimensional finite element analysis, each error became about 4%, 5%, and 5% by TSVD, the Tikhonov regularization, and the 2-dimensional hybrid method, respectively. The result of TSVD was the most accurate. However, it is considered that the 2-dimensional hybrid method is effective as the stress separation method from the viewpoint of the accuracy and calculation time.

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