Dynamic ESPI to analyze dynamic process of deformation is reviewed. Different from conventional phase analysis such like a phase shifting method, a new algorithm based on Hilbert transformation of interference signals in time domain is introduced. A compact prototype of a DESPI system was presented to analyze two-dimensional in-plane deformation field.

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This article describes a method to evaluate fatigue damages and to estimate fatigue lives using laser without contact. In the fatigue of a low carbon steel, slipbands appear on the material surface in the early stage before crack initiation and the slipband density increases and thus the specimen surface changes with progress of fatigue damage. The present method intends to detect the surface change caused by fatigue by observing the pattern change of diffused light when a laser light illuminates the specimen surface. We observed the change of the surface and investigated correlation with diffused light pattern during fatigue loading. Empirical formulae were derived to express the relation between the change of diffusion pattern and loading cycles, stress amplitude and fatigue life. We proposed a method to estimate fatigue life of a steel material using these relationships based on observation of the laser diffusion pattern. The estimated result showed that we can predict the fatigue life at the stage before half of fatigue life with sufficient accuracy.

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This review describes recent advances in nondestructive material evaluation of surface layers by leaky Rayleigh wave technique. The phase velocity dispersion as well as attenuation of the leaky Rayleigh wave is sensitive to microstructures of surface layers at suitable frequency of the wave. With this technique, the mass density and Young's moduli of surface layers are estimated. The micro structural changes in surface layers, i. e., precipitation, micro cracks, result in appreciable change in the phase velocity dispersion and attenuation.

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Acoustoelasticity, the method of experimental stress analysis with ultrasonic waves, is surveyed with emphases on fundamental relations (acoustoelastic laws) and nondestructive measurements of residual stress. First, the acoustoelastic effect due to uniaxial stress is described, and requirements on acoustoelastic laws are indicated. Next, the birefringence method applicable to plane stress measurements, used most frequently in acoustoelasticity, is illustrated together with examples. Then, the illustration of nondestructive methods with SH waves is given, and finally, acoustoelasticity with surface waves is summarized.

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Microwave is an electromagnetic wave having a wavelength of 1mm to 1m. Microwave has an advantage that it can propagate well in air. Therefore, a coupling medium is not necessary when nondestructive inspection is carried out. Another advantage of microwave is that the inspection result is independent of density but dependent on the intrinsic properties of the materials. That is why microwave inspection has often a higher sensitivity than the other techniques, especially for inspection of dielectric materials. In this review, microwave imaging of the delamination happened in IC packages is demonstrated. Microwave image is created using the phase and amplitude of the reflection coefficient, measured by a network analyzer. To obtain a high spatial resolution, an open-ended coaxial line sensor is used. The delamination is known to happening often at the interface between the encapsulant resin and the chip pad, as the results of the stress and the pressure induced by the thermal expansion mismatch between dissimilar materials and the evaporation of the moisture absorbed in the package, during the solder reflow process. On the other hand, solder bump and delamination under the silicon chip of the chip size package are also inspected.

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The objective of present study is to develop a prediction method of residual fatigue life of cyclically loaded metallic materials in early stage of its life. A change in intensity of ultrasonic back reflection wave from the material surface under cyclic loading was measured. The relation of the change to a fatigue damage of the material was examined through the microscopic surface observations using optical microscope and atomic-force microscope. An increase of the ultrasonic back reflection intensity occurs due to the fatigue crack initiation at the slip band. This technique enable one to detect the initiation of fatigue damage at a number of cycles before the 85% of the fatigue crack initiation life until the crack length being 0.1mm.

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The magnetic diagnosis of iron-based materials was performed by using many magnetic tools such as a small Hall element for leakage flux observations after polarizations, a locally sensitive fluxgate sensor available down to 100pT and by a pick-up coil for magnetic noise observation. The first derivatives of the normal components of the leakage flux with respect to positions along the applied tensile stresses were found reflecting the location of the heavily strained positions for ferromagnetic materials and inversely reflecting for the location of induced martensitic transformations for paramagnetic materials as SUS304. A numerical indicator of internal strains was derived by the magnetic noise measurements and the parameter well coincided with the degrees of strains and the directions of the strains observed by X-ray diffraction. These behaviors of magnetic inhomogeneity were visualized by the 2D display of the leakage flux by using the scanning of the magnetic sensor over the sample surface.

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The Influence of the radius of curvature of the crack tip on a mixed mode stress intensity factor was discussed by three dimensional finite element analyses. As the radius of curvature of a notch becomes large, the inaccuracy of the stress intensity factor becomes large. Therefore, it was elucidated that a notched specimen cannot estimate the stress intensity factor of a mixed-mode accurately. If the mesh of a hybrid analyses domain is made fine, the equivalent nodalforce on an external boundary can be obtained in higher accuracy. The infrared stress images were taken by infrared thermography using the compact normal and shear specimens subjected to seven kinds of mixed-mode loadings, and the data of the sum of the principal stresses were obtained. After estimating nodal forces from the sum of the principal stresses by an inverse problem analysis, the error included in the experimental field was modified by the 2-D intelligent hybrid method. The stress intensity factor was evaluated by the virtual crack extension method and the displacement extrapolation, and the validity of the infrared hybrid method was discussed in comparison with the 3-D finite element analyses.

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There are two major techniques for determining the viscoelastic properties in general. One is the dynamic retardation measurement for sinusoidal input and the other is the static measurement under constant strain-rate. In the pervious paper, the authors developed a Prony series approximation technique for the determination of viscoelastic functions from dynamic response of materials utilizing the random searching method. The authors develop a new approximation algorithm for the determination of viscoelastic material functions by a Prony series using data obtained under constant strain-rate test. The technique proposed enables, 1) to eliminate complicated procedures, 2) to determine the coefficients in the Prony series in high accuracy avoiding the ambiguity in sign change. In order to evaluate the effectiveness of the technique, the authors determined not only the relaxation modulus but the creep compliance of an epoxy resin successfully in high accuracy standing on the concept of pseudo-elasticity.

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