Phase-shifting methods are advantageous to analyze phases of fringe patterns obtained by interferometry. Conventional phase-shifting methods usually uses three or four images obtained by phase-shifting. If only one camera is used for the three or four images, the fringe images are recorded with stopping phase-shifting so that the brightness does not change during the exposure time of the camera. The stopping procedure obstructs speeding up of the measurement system. We proposed a new method to take four images for phase analysis without stopping phase-shifting. The method is called the integrated phase-shifting method (IPSM). This method is suitable for real-time phase analysis. In this method, four images are recorded continuously with full-exposure time during phase-shifting. In this paper, a development of a real-time phase analysis circuit using this theory and an application to nanometer-order displacement distribution measurement for a micro-accelerometer manufactured by micro-machine techniques are shown.

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The closed loop type push-pull fatigue test system available at ultra-high temperatures was developed, where special attention was given to the extensometer. Then the tensile stress-strain response, tensile creep behavior and cyclic stress-strain response were investigated for sintered silicon nitride ceramics at elevated temperatures. The great amount of inelastic strain, which is greatly dependent on stress rate, was produced under tensile and cyclic push-pull loadings in this material at 1 300°C. Moreover, the gradual increase in resistance to cyclic deformation was revealed during cyclic loading at 1 300°C. It was found that inelastic strain is easier to generate under tensile loading than under compressive one in cyclic loading test ; the stress-inelastic strain hysteresis loop was characterized by the fatter shape on the tensile stress side than on the compressive stress side. Furthermore, existence of transient creep stage was clearly exhibited in the creep curves obtained from tensile creep test in Si₃N₄ ceramics at 1 300°C.

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In the several engineering fields, the collision between structures and foreign objects involve some difficulties in the numerical treatment because intensity, contact area and the time history of the impact load are not known. Some experimental techniques have been suggested to measure the distributed load by a piezo-electric sensor. However, such a direct measurement often meet with difficulty, because the geometry or rigidity of the contact surface may be altered by attaching the sensors on the surface. In order to overcome the difficulty, this paper deals with estimation of pressure distribution applied to the elastic thin plate using inverse analysis. In the present study, the transmission matrix is introduced which gives linear relation between distributed load and internal strain. The boundary element method is employed to obtain the transmission matrix, and Tikhonov's method is used to stabilize the solutions, which are determined by inverse analysis. A numerical simulation on the circular plate subjected to transverse distributed loading is conducted to demonstrate the effectiveness of the present method.

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Effect of bend deflection on measurement of axial load in bolts by ultrasonic method are studied experimentally. External loading test with changing the tensile-bend ratio were conducted using long steel bolts. A ray tracing analysis were also conducted to simulate the effect of bend deflection. It is cleared that the change of reflection angle of the ultrasonic wave on the bottom surface of the bolts is the controlling factor for the effect of bend deflection on the measurement of axial load in bolts. A new method to evaluate the axial load accurately under the deflection is proposed and its validity is conformed experimentally.

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Accurate values of X-ray elastic constants are required for a reliable stress measurement of thermal barrier coating films (TBC films). In this paper, atmosphere and pressureless plasma sprayed TBC films were removed from substrates, then X-ray elastic constants of both TBC films were determained by using newly developed tensile jig. For the atmosphere plasma sprayed film, the value of the mechanical elastic constant was much smaller than the X-ray elastic constant owing to cracks or pores existing in the films. The X-ray elastic constant of the atmosphere plasma sprayed TBC film was nearly equal to that of the pressureless plasma sprayed film. This means that the X-ray elastic constants are little influenced by cracks or pores. Residual stress distributions in both films coated on the substrates were obtained. In the surface region with the depth up 60 μm, residual stresses of both films showed a drastic variation. This variation of the residual stresses was build up during rapid quenching and solidifying of the molten droplet. In deeper regions, residual stresses were nearly constant. These constant values of residual stresses are caused by the thermal strain mismatch between the TBC film and the substrate.

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In our previous studies, first, for linear elastic deformation, an intelligent hybrid method that automatically detects and eliminates the errors and noises in a full-field experimental measurement field was developed. Next, for nonlinear elastic-plastic deformation, the authors derived an incremental variational principle minimizing the experimental measurement errors. Concepts of incremental self-restoration forces and energies were also presented. Furthermore, the authors developed an intelligent hybrid method based on this incremental variational principle. In this study, the progressing nonlinear elastic-plastic deformation field near a crack tip in A533B CT specimen is evaluated by using the intelligent hybrid method. The intelligent hybrid method demonstrates automatic detection and elimination of the measurement errors and smooth visualization of stress and strain distributions. Furthermore, the intelligent hybrid method automatically achieves the path independence of the T integral, restoring the path-dependence caused by the measurement errors. This paper provides the foundation of an intelligent measurement and visualization of displacement and stress fields in actual structural components.

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High-speed holographic microscopy is applied to take successive microscopic photographs of a fast propagating crack at bifurcation. The crack speed is about 650 m/s. From the photographs, crack opening displacements (CODs) of the mother crack and two bifurcated branches are measured along the crack. A specimen with a notch is also made, where the notch has the bifurcated notch tip same as the bifurcated fast propagating crack. Opening displacement of the notch is measured by Moire interferometry under static loading condition. The measurement results show that the opening displacements of both the mother crack of the bifurcated fast propagating crack and the mother notch of the bifurcated notch are proportional to square root of the distance r from the crack or the notch tip. The opening displacements of the two bifurcated branches of the notch are also proportional to √(r). But the CODs of the bifurcated branches of the fast propagating crack are not always proportional to √(r).

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The point-by-point measurement of in-plane displacement was conducted by the point-wise filtering approach of speckle photography. The experiment was conducted on the compact normal and shear specimen made of homogeneous and dissimilar materials subjected to various kinds of mixed-mode loading. Then, stress-intensity factors of asymptotic solution derived by Sun and Jih were estimated using the displacement data obtained from speckle photography by the least squares method. The contour diagrams of stress and strain obtained by using the raw displacement data of experiment remarkably differed from those obtained by FEM analysis. However, the stress and strain obtained by the present analyzing system were very similar to those obtained by FEM analysis.

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Fatigue life of mechanical structures have been estimated according to Safety Life Design. In this study an ultrasonic technique for quantitative nondestructive evaluation of small surface fatigue crack is developed. The use of an oblique longitudinal wave with large angle (over the critical angle) of incidence upon specimen surface is emphasized. Ultrasonic testing was performed with small surface fatigue cracks and artificial defects. To evaluate cracks, maximum amplitude of reflection echo due to these defects were used here. From such measurements, we show that by using this parameter, above 115 μm surface length of fatigue surface crack can be detected. Depth and deflection of these cracks also can be detected. From these results we deduced an experimental equation to calculate length and depth of crack. Finally, a model based on three dimensional elastodynamics was proposed to simulate this ultrasonic technique, and numerical analysis were done for surface crack reflection problem.

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We studied the ultrasonic attenuation change during creep tests on austenitic stainless steel (JIS-SUS 304). We applied to tensile stresses to the materials at 973K and measured ultrasonic attenuation using electromagnetic acoustic resonance (EMAR) . EMAR is a contactless resonant method with an EMAT and is free from extra energy losses in the attenuation measurement, resulting in the measurement of intrinsic attenuation in solids. We launched polarized shear wave in the thickness direction of the plate specimen to obtain the ultrasonic velocity from the resonant frequency and the attenuation coefficient from the ringdown curve at the resonance. Attenuation exhibits much larger sensitivity to the damage accumulation than the velocity. Approaching to the rapture, it becomes ten times as large as the initial value, which is attributed to the microstructural changes, especially, dislocation mobility. This is supported by the 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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Cast duplex stainless steel is frequently used in main coolant pipes and reactor coolant pump casings of nuclear power plants due to its excellent material strength, toughness and superior corrosion resistance. However, it is known that material deterioration referred to as thermal aging occurs when this material is exposed to high temperature over 300°C for a long time. As a result, the material toughness decreases. Therefore in managing the components made of the cast duplex stainless steel, it is necessary to evaluate non-destructively the change in the mechanical property caused by thermal aging. In this study, to develop a non-destructive technique for evaluating the deterioration of toughness in cast duplex stainless steel caused by thermal aging, we compared 5 kinds of evaluation techniques, ultrasonic sound velocity measurement, thermoelectric power measurement, resistivity measurement, SQUlD (Superconducting Quantum Interference Device) measurement and positron annihilation line-shape analysis for detecting ability of thermal aging. As a result, the thermoelectric power measurement is the most effective technique for evaluating thermal aging of duplex stainless steel because of the closest correlation between non-destructive parameter and toughness and because of low deviation of measured values.

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Cavitation erosion was compared between cavitating jet and vibratory methods. It was found that the erosion by cavitating jets occurs 8 to 10 times as fast as that by the vibratory, thus the cavitating jet method is effective for the acceleration test. The erosion mechanisms produced in both apparatuses are the same, judging from the time interval of bubble collapse impact loads and the shape of pits. It was concluded that erosion is evaluated by the accumulated summation of squares of impact loads, not by the accumulated volume of pits for which it is obtained from the pit on the material surface exposed to cavitation for 1-5 seconds.

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Since the surface morphology of materials can be observed with atomic-scale resolution, scanning atomic force microscopy (AFM) in a powerful technique to study mechanisms of fatigue and fracture of solid materials. In the present study, slip-band formation and fatigue crack-initiation processes in 70-30 brass were observed by means of AFM. The slip-band angle relative to the stress-axis at the specimen surface varied from 15 to 90°, and it appeared most frequently around 60°. The depth of the intrusion drastically increased with its outgrowth to a crack, and with coalescence of cracks, the width of cracks increased rapidly. The critical value of the intrusion depth for crack initiation was given as a function of the slip-band angle through a geometrical model for the slip-direction and the slip-step, and the critical value was independent of stress amplitude. From presice observations of slip-band tips, slip-bands had steep slope when they were blocked by grain boundaries, and the slip-bands descended by gradual slopes to plain surfaces when they terminated within grains.

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Fatigue life estimation of solder bumps is one of the most critical technologies for the development of ball grid array packages. Since the recent trend in the package development is toward smaller solder bumps, the estimation of the crack initiation and initial crack propagation rate is essential in the reliability design. In this study, mechanical fatigue tests were carried out using Sn63-Pb37 solder bump specimens. The initial crack propagation rate of the solder bumps was estimated based on the load drop, because the crack observation with destructive test is not suitable for the uniform evaluation of many results. A simple estimation of the crack propagation based on the linear damage law was applied. The trend of the simple estimation results corresponded well with the experimental results of crack propagation. The estimation method of crack propagation based on the fracture mechanics was also examined so as to reduce error in reliability design. Creep J-integral range was calculated using the elastic-creep FEM analysis. The relationship between the crack propagation rate and creep J-integral range was obtained. It was confirmed that the initial crack propagation of micro solder joints could be accurately evaluated using the creep J-integral range.

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The observation of tensile fracture process of unidirectional Si-Ti-C-O fiber-bonded ceramic composite at room temperature revealed the fracture behavior as follows : First breakage of matrix initiated at the strain level of about 0.2%. Then, the number of matrix cracking increased with increase in strain. In spite of the cracking of matrix, the interfacial debonding was suppressed by the compressive residual stress of the matrix. The slope of the stress-strain curve scarcely decreased from the initial one because of high fiber volume fraction (0.9) and redistribution of stress caused by suppression of debonding. Breakage of fibers occurred just before fracture. Once it occurred, large scale debonding was caused owing to the tensile residual stress of fiber. Finally, overall fracture of the composite occurred, accompanied by a large number of fiber breakage. A simulation of the fracture process was performed using the modified shear lag analysis combined with the Monte Carlo method. The characteristics of the fracture process observed in experiments could be reproduced fairly well by this method.

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This paper describes an automated generation method of a hexahedral mesh named Intelligent Local Approach (ILA). Here elements are generated sequentially, by taking account of both local information on geometrical constraints and user's demand on quality of elements. Topological connectivity is first determined based on a heuristic category-based method. Then a fuzzy knowledge processing technique is utilized to determine optimum positions of nodes, considering various complicated geometrical constraints for high quality hexahedral elements. The determination of hexahedral connectivity and nodes positions is important technique to overcome difficulty in generating a hexahedral mesh of an arbitrary shape. Fundamental performances of the ILA are demonstrated in detail through generating several hexahedral meshes.

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The elasto-plastic damage behaviors of functionally graded materials (FGM) subjected to thermal loading are analyzed by the finite element method using continuum damage mechanics. The Lemaitre's damage model is employed to analyze the damage behavior of a FGM disk subjected to thermal shock and a FGM coating subjected to thermal cycle. The effect of FGM on the thermal damage is discussed through some numerical examples for industrial materials. Numerical results show the validity of the present method for the evaluation and the development of new FGM.

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The constitutive equation based on continuum damage mechanics is applied to the computational material testing of steel specimens. The material constants for the elasto-viscoplastic deformation and the damage evolution are determined by the test results for unaxial stress-strain behaviors and SN curves in fatigue. The identified constitutive equation is used in the computational material testing for the dynamic tensile behavior of pre-fatigued and pre-strained steel specimens. The effects of pre-fatigue and pre-strains on the tensile strength, breaking strains and absorbed energy are quantitatively well evaluated by the computational testing.

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Main properties of the solid materials are strain-rate dependence of stress and strain dependence of wave propagation speed. These phenomena are expressed by use of a simple tensile elastic-plastic-viscoplastic constitutive equation in which the understress and overstress are introduced. The equation describing the speed of elastic-plastic-viscoplastic stress waves predicts strain rate dependence of wave propagation speed. Based on an uni-axial elastic-plastic-viscoplastic constitutive equation, a generalized constitutive equation is proposed for the non pre-strained and non pre-stressed solid materials. For generalizing, not only the understress and the overstress are generalized but also the third invariant of the deviatoric stress tensor is considered. Moreover, It is shown that the proposed equation includes a generalized elastic-plastic, elastic-viscoplastic and elastic constitutive equation for the special cases.

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Unit cell models have been used to investigate mechanical properties of composite materials assuming periodically arrangement of inclusions. It is desirable to clarify the geometrical parameters controlling the mechanical properties of composites because they usually contain randomly distributed particulate. In this paper, therefore, the effective elastic modulus in tension is considered using unit cell models with varying the shape and arrangement of inclusions. In the first, the projected area fraction and volume fraction of inclusions are found to be two major parameters controlling the effective Young's modulus of 3 D array of inclusions. Next, through the comparison between the results of 3 D and 2 D array of inclusions it is found that the elastic moduli of 2 D and 3 D arrangements of inclusions are almost equivalent when both arrangements have the same projected area and volume fractions of inclusions.

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The Markov process is applied to the chain-of-bundles model with fibers packed in a hexagonal array, in order to obtain the analytical solution for the fracture probability of a unidirectional fiber composite. It was assumed in the process that a group consisting of fiber breakage points, the so-called cluster, evolves intermittently with an increase in stress. Then, the load sharing structure of unbroken fibers around the clusters was decided from geometric and mechanical local load sharing rules. The composite fractures if the cluster achieves a critical size. It was found that the number of possible fiber breakage paths to form a cluster is extremely increased, as the cluster size is increased. That is, a 6-break cluster exhibits eighty-two types of cluster configurations to form a 7-break critical cluster, while l- and 2-break clusters have only one type of configuration. By using the 2-parameter Weibull distribution function as a strength distribution of the fiber, the fracture probabilities of 2-break to 7-break critical clusters were analytically obtained. The results showed that the larger clusters more greatly reduce the width of the distribution, following m_c= i ×m_f (i : the number of broken fibers in a cluster, m_c and m_f : Weibull shape parameters for the fracture probabilities of a critical cluster and fiber strength, respectively). It was proved that, in addition, the analytical solutions can be approximated with a high accuracy by the one-state birth process.

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The purpose of this paper is to present analytical methods of determining the transient temperature and in-plane thermal stress in a thin finite circular plate heated by the surrounding medium at the outer lateral surface and allowing arbitrary variations of heat-transfer coefficient along the radial position on the upper and lower surfaces of the plate. The transient temperature field is analyzed by modified Vodicka's method for one-dimensional boundary value problems in composite regions, and the associated in-plane thermal stresses are determined taking the temperature dependency of Young's modulus and the coefficient of linear thermal expansion into consideration.

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This paper investigates striation configuration (H/s) under 2-step loading condition. Here, H is striation height and s is striation width. Under condition that vary from low maximum load to high maximum load, no acceleration of crack growth was visible, further H/s remained similar to values found under constant max. load. When load varied from high to low, retardation appeared immediately after varying the load. Striation configuration immediately after varying the load either flat or the H/s value dropped remained to a level much smaller than that under constant max. load. Once crack growth reached about 500 μm, striation configuration recovered from the previeus flat condition and the H/s value returned to the value found under constant max. load.

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A pure copper used as an electronic material was reinforced by using low-carbon steels as a clad plate with relatively small thickness of t = 1, 2, 3 mm, so as to improve the fatigue properties of the advanced electronic parts. Using stress intensity factor range ΔK and Young's modulus E, the fatigue crack propagation rate, da/dN, for the clad plates was expressed by a power low of ΔK/E as well as for the copper and low-carbon steel base materials. There was large scatter in the da/dN values for the thicker clad plate. On the other hand, there was very small scatter in the da/dN-ΔK_est/E relation for all clad plates, where ΔK_est/E was evaluated from the measured crack opening displacement. Under the same ΔK_est/E value, the da/dN for the thicker clad plate with the concave-convex and zigzag crack front in the inner copper was lower than that for the thinner clad plate which has almost the same da/dN-ΔK_est/E relation as the base low-carbon steel.

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The plane elasticity solution is presented in this paper for the crack problem of a layered medium. A functionally graded interfacial region is assumed to exist as a distinct nonhomogeneous transitionaly layer with the exponentially varying elastic property between the dissimilar homogeneous surface layer and the substrate. The surface layer contains a crack perpendicular to the boundaries. Fourier transforms are used to formulate the problem in terms of a singular integral equation. The main results presented are the variations of stress intensity factors as functions of geometric and material parameters of the layered medium.

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A simple experimental procedure involving measurement of strain through strip gages with five strain sensors per strip gage, has been developed to determine magnetic moment intensity factors in different specimen geometries. Static experiments are conducted in the bore of a superconducting magnet at room temperature. Ferritic stainless steel is here used as the fixed-end through-cracked plate specimen for bending test. The experiments show the increase in the moment intensity factor with increasing magnetic field. The effect of the magnetic field on the moment intensity factor is more pronounced with increasing the crack length to specimen thickness ratio. The qualitative experimental trends are in good agreement with the theoretical model developed previously.

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The influences of stress waveform and water absorption on the tension-tention fatigue fracture behavior were investigated in a carbon fiber reinforced poly-ether-ether-ketone matrix composite (AS-4/PEEK), having an angle-ply stacking sequence of [±45°] _3s. The fatigue tests were performed under sinusoidal, negative pulse and positive pulse waveforms on specimens preconditioned in dry air (dry specimens) and the ones which were immersed in deionized water at 80°C for two months (wet specimens). For dry specimens, the fatigue strength under positive pulse waveform was the highest, and decreased in the order of negative pulse waveform, sinusoidal waveform. For wet specimens, the fatigue strength under positive pulse waveform showed the lowest. Internal damage was observed with a scanning acoustic microscope (SAM) and the fracture surface was closely examined using a scanning electron microscope (SEM).

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Press-fomed sheet metal parts are usually adhesively bonded together at the final stage of assembly. Instead of such a conventional process, a new technology of press-forming of adhesively bonded sheet metals was investigated. In this process, first flat sheets are adhesively bonded, and then press-formed into final shapes. From V-bending experiments on adhesively bonded aluminium alloy sheets, it was found that large shear deformation occurred in the adhesive layer during the bending, which in some cases lead to the delamination. Both from the experimental observations and numerical simulation, it is concluded that the large shear deformation of the adhesive layers can be suppressed when performing air-bending of enough long span, rather than die-contact V-bending.

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Total sacrectomy is the most efficient surgical treatment to prevent recurrence of malignant sacral tumors. It is required a reconstructed structure replaced for the sacrum which can support large weight of upper body in this treatment. On the other hand, large components are not allowed to reconstruct the structure because of an infection risk. Therefore, the reconstructed structured of the sacrum have to be designed under the severe requirement that is necessary to hold large weight by using minimum structure components. Although several designs of the reconstructed structure in which lumber vertebrae connected with the pelvis by using metal rods, bars and screws have been proposed, size and layout of the instruments have mainly depended on only constraint due to operative procedure but not mechanical considerations. Reliability of the reconstructed structures has been ensured empirically, but quantitative evaluations of rigidity and mechanical stress have not been sufficient. In this study, finite-element analyses of two types of the reconstruction which were available in clinical use were carried out to obtain stress distribution and total deformation. Advantages and disadvantages of the reconstructing structures were discussed comparing the results. Furthermore, an improved reconstructing structure was proposed and its mechanical effectiveness was examined by finite-element analysis and model experiment.

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