A bending fatigue test in the region of the generation of the stress-induced martensite (β'₁ phase)has been carried out using the two types of single crystal specimens of a Cu-Al-Ni alloy which have the surface and longitudinal orientations of (001) [100] and (011) [100], respectively. In the early stage of the fatigue test, stripes which are associated with the microscopic surface unevenness caused by the multiplication of interfacial dislocations were found along the habit planes in the β₁-β'₁ stress-induced martensitic transformation. Fatigue cracks were initiated at the intersections of the stripes and grew along the {110} plane of the β₁ parent phase. By lattice correspondences this {110} plane of the β₁ parent phase was consistent with the {001} plane of the β'₁ martensitic phase. Consequently, fatigue crack initiation and growth occurred along the {001} cleavage plane within the stress-induced martensitic phase, these cracks grew and coalesced, finally resulting in failure.

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In order to clarify the tribological behaviour of SUS304 steel in seawater, the electrochemical approach was taken in this work. Wear tests were carried out at different potentials from -800 mV to 600 mV ( vs SCE ) under the following conditions : a normal load of 10N, a slip amplitude of 1.5mm, a frequency of 8.3 Hz and total sliding distance of 300 m (10⁵ cycles). Wear volume increased by three orders of magnitude with an increase in potential from -800 mV to 600 mV. The relationship between wear volume and corrosion volume was discussed. Corrosion volume was calculated from the anodic current in the polorisation curve for a fresh surface, which was obtained by the potential pulse method. In conclusion the electrochemical factor, dissolution of metal, governed the wear in seawater, while the mechanical factor was only to produce the fresh surface on the wear surface during sliding.

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The effect of grain size on the mechanical properties of the grain-refined Cu-Zn-Al shape-memory alloys was investigated by DSC, tensile testing and shape-memory heat engine drive testing. It was found that the β-grain size of the alloys at a constant heat-treatment time of 5 minutes varies from 37μm to 800μm depending on the alloying elements: Ni, Fe, V and Co. In addition, the β-grain size of each alloy depends on the solution treatment time itself. The transformation heat obtained by DSC measurements increased with an increase in grain size. The influence of the grain size on the mechanical properties was investigated by tensile testing. It was found that the 0.2 % proof stress of both the β-phase and M-phase state alloys changes in accordance with the Hall-Petch relation. The ultimate tensile stress and fracture strain of the specimens solution-treated up to 20 minutes change slightly. While those of the specimens solution-treated for 40 minutes decrease considerably. In order to test the effect of grain sizes on the heat engine, an off-set-crank-type heat engine is equipped with shape-memory-alloy springs for durable cycle testing. Using a similar lot sample but different solution treatment times, the durable cycles of the heat engine increase with smaller grain size. Using a similar solution treatment time but different grain sizes, the durable cycles of the heat engine increase with smaller grain size.

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Rotating bending fatigue tests were carried out on annealed 0.42 % C steel specimens with a circumferential notch in air and in oil. Although the increase in fatigue strength due to the existence of oil becomes more pronounced with decreasing stress level, it becomes smaller near the fatigue limit. The main reason for the increase in fatigue strength is the wedging action of the oil. The lowering of the difference in fatigue limits under both environments is caused by the following two effects: lowering of the wedging action of the oil with decreasing crack opening displacement in the crack arresting process, and decrease in the oxide-induced crack closure due to the isolation of atmosphere.

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An optical system of pulsed holography is developed and applied to take instantaneous photographs of both the opening and the front edge of a crack which is propagating through a PMMA plate specimen at a speed of several hundred meters per second. Crack opening displacement (COD) on a specimen surface is measured along the crack in the vicinity of the tip where the 3-D (three-dimensional) stress field is developed. The COD is proportional to the square root of the distance r from the crack tip. It means that the stress field on a specimen surface has the singularity of 1/√(r), even in the 3-D stress field. The singularity is unchangeable even though the crack speed changes. Crack front edge angles, which are angles between a crack front edge and specimen surfaces, are also measured, and they are obtuse. In the case of a lower crack speed, the measured angles agree with the numerical result of a slowly propagating crack given by Bazant and Estenssoro. As the crack speed increases, the angles decrease and seem to approach 90 degrees. Some mechanisms which make the crack front edge angle decrease are discussed.

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Crack propagation rate of a model surface crack in a plate, the crack tip opening stresses or displacements under various biaxial stress ratios by the simultaneous action of plane bending and cyclic torsion are examined. The aspect ratio of a crack is not affected by the biaxial stress ratio but the relationship between the propagation rate da/dN and the stress intensity factor range ΔK or the effective stress intensity factor range Δ K_eff depends on it. This is mainly due to the differences of both CTOD and the scale of the slipped region at the crack tip caused by the difference of biaxial stress ratio.

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In this paper, the hypersingular integral equation method (HIEM) is applied to calculate the stress intensity factors of the mixed mode crack problems. The stress fields induced by "two kinds of displacement discontinuity" are used as fundamental solutions. Then, the problem is formulated as a system of integral equations with the singularity of the form of (ζ-χ)^-2. In the numerical calculation, two kinds of unknown-functions are approximated by the products of the weight functions and Chebychev polynomials. As examples, the stress intensity factors of the oblique edge crack in the semi-infinite plate are treated. The calculation shows that the HIEM gives rapidly converging numerical results even for extremely oblique edge crack.

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In this paper, a testing method for the mixed-mode fracture of cracked sheet specimens was proposed to investigate the ductile fracture behavior with stable crack growth under the mode I-II mixed-mode loading condition. In contrast to the conventional method using a slant-cracked specimen, it is possible in the proposed method to keep the ligament width constant irrespective of the angle between the tensile loading direction and the crack plane, and thus, to separate the influence of the loading direction and that of the ligament width on the ductile fracture behavior. The validity of the proposed testing method was examined by rosett analyses, finite-element analyses, and the fracture toughness tests using the plate of PMMA. Mixed-mode fracture tests were carried out on center-cracked sheet specimens with various ligament widths of 2024-T3 and S50C(thickness=1.6 mm) using the proposed testing method. From the test results, it was found that the direction of ductile crack extension and the fracture appearance varied according to the loading direction. The Mises equivalent stress obtained at the maximum load using the net cross-sectional area was almost constant independent of the ligament width and the loading direction.

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On two-phase materials, there exists a microscopic stress/strain field resulting from their microstructure as well as a macroscopic stress/strain field in the region near a crack tip. The fracture behavior of such materials seems to depend strongly on the microscopic stress/strain field. In this paper, the analysis of the microscopic stress/strain field around a crack tip in WC-Co composites, whose Co-volume fractions are 10 %, 30 % and 50 %, has been carried out by the finite element method based on a mechanical model of two-phase sintered materials proposed in a previous paper. In the region ahead of a crack tip, the microscopic stress on WC-grain and the microscopic strain on the Co-phase are larger than the macroscopic stress or strain, respectively. The microscopic stress on WC-grain increases with an increase in Co-volume fraction. From the comparison of the numerical results with the experimental results of fracture toughness in reference, it is suggested that microcracking occurs on the WC-grain ahead of a crack tip before final fracture, and that the process from the microcracking to the final fracture is the toughening mechanism due to ductile fracture of the Co-phase.

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The effect of adherend stiffness on the joint strength is examined by varying the adherend thickness. The joints used in this study have adherends of carbon steel and adhesive of epoxy resin. The variation of strain in the joints with mean stress is measured under static tensile shear load. The main conclusions are as follows: With the decrease of the adherend thickness, the final fracture strength of the joint increases. An FEM model that is used for prediction of the final fracture strength is proposed on the basis of the experimental results. The predicted initial cracking loads and final fracture strength show good agreement with the experimental ones.

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The impact damage that occurred in silicon carbide plates was investigated by projectile impact tests. Target plates of silicon carbide with two different thicknesses were impacted by three kinds of projectiles with various speeds ranging from 30 m/s to 500 m/s. Projectiles were 5 mmφ and 3 mmφ steel spheres and 5mmφ silicon carbide spheres. Various modes of damage, such as indentation concave, ring and cone cracks, radial and median cracks, lateral cracks, spalling and formation of a percussion cone were observed. The relationship between the mode of damage and the speed or the kinetic energy of the projectile was investigated. The damage caused by the impact load of the present study was very similar to that caused by quasi-static point indentation load. It was also observed that the outermost diameter of ring cracks formulated in the impacted SiC plate was well calculated by the elastic Hertz's impact theory or a modification of it including the effect of the plastic deformation of projectiles.

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There are two approaches in the incremental finite element analysis of elastic-plastic problems; one takes an explicit scheme using forward Euler integration formula with adaptive load incrementation, the so-called r_min method, and another implicit scheme with iterative procedures such as the Newton method. This paper discusses an algorithm of determining incremental step size in the former approach. A new additional restriction is proposed for the determination of the loading factor r_min when unloading takes place. A concept of admissible error is introduced where errors in stress increments are defined as the difference between one computed by assuming the elastic-plastic constitutive relation and the other computed by assuming the elastic relation. The error norm should be restricted within specified value. Numerical examples are demonstrated to show that the algorithm is reasonable.

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Ultrasonic inspection with pulsed echoes is simulated by numerical analysis using the finite difference method. The wave form of the reflected pulse from the lower surface and the dependence of the peak amplitude on the crack length are studied. The relation of the location of the crack with the reflected wave is studied. A qualitative agreement with the experimental result is obtained. The result is that the thickness and the width of the crack can be predicted by the information on the reflected ultrasonic wave.

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This paper is concerned with an analytical formulation and a numerical solution of the elasto/visco-plastic dynamic response of multilayered moderately thick shells of revolution subjected to impulsive loads with application to a cylindrical shell. The equations of motion and the relationships between the strains and displacements are derived by extending the Reissner-Naghdi theory in elastic shells with consideration given to the effect of shear deformation. As the constitutive relation, Hooke's law is used in the linear elastic range, and the elasto/visco-plastic equations by Perzyna are employed in the plastic range. The numerical method related for this problem is a method using finite difference in both space and time. As a numerical example, the elasto/visco-plastic dynamic response of a fixed supported two-layered cylindrical shell composed of a titanium and a mild steel layer subjected to impulsive load is analyzed. Numerical computations are carried out for three cases of the ratio of the thickness of the titanium layer to the shell thickness. It is found from the computations that the stress distributions and the deformation vary significantly depending on the thickness ratio.

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In this paper, the time-independent constitutive model of cyclic plasticity proposed previously is extended to the model of cyclic viscoplasticity, considering the motion of the center of the loading surface and plastic deformation-induced anisotropy. To construct the model, the effect of the variation in strain rate upon the stress-strain relationships is investigated by performing the tension -compression test with SUS304 stainless steel. The Ramberg-Osgood law is applied to each cycle with respect to the current center of the loading surface and the material constants in this model are determined from the test as a function of strain rate and strain amplitude. As a result, this model could accurately describe the cyclic viscoplastic behavior of the material.

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Spherically symmetric deformation of a solid sphere under applied uniform radial stretch is considered within the theory of finite elasticity. The sphere is composed of a homogeneous, isotropic, compressible, hyperelastic material called Blatz-Ko material. As a result, there exists, in addition to a trivial homogeneous solution, a solution which contains a spherical cavity when applied stretch exceeds a certain critical value. Since the solution for the microvoid problem converges to the bifurcated solution, this bifurcation phenomenon can be regarded as an idealized model describing the void nucleation and growth in the material.

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The residual stress of epoxy resin for IC plastic packages generated in the curing process as well as the cooling processe is studied both analytically and experimentally. The property of thermal expansion in the temperature history and the viscoelastic properties at each temperature condition are measured by the strain gage method and creep test, respectively. The adhesive strength of the resin is determined by the axial-torsional loading test on tubular adhesive-bonded butt joints. With these mechanical properties, the mechanism of residual stress development is investigated using a 4-parameter viscoelastic model and a thermal shrinkage element. The residual stress is analyzed by the finite-element rnethed (F. E. M.) of a model of resin block which contains a metal plate, and the strength of the model is evaluated for the residual stress. The results of analysis show a tendency similar to experimental results and the critical position by the residual stress is found at the corner of the buried metal plate.

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In this paper, we deal with the boundary element formulation of the transient axisymmetric thermoelastic problem. For the formulation of the problem, we introduce the thermoelastic displacement potential function. Using this function, we indirectly obtain Green's functions of the thermal displacement and thermal stress components and their boundary integral representations. Performing the time integration analytically, the resultant function is separated into two parts: the steady and the transient parts. We observe singularity at the boundary integration only in the steady part.

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We apply the conventional consideration of analytical method in linear thermoelastic problems to nonlinear thermoelastic problems in the second order theory. The basic equations of nonlinear thermoelastic problems are formulated by using Adkins perturbation method. We also introduce thermoelastic potentials applying Helmholts theorem for analyzing nonlinear thermoelasticity problems. Further, by applying these thermoelastic potentials, we propose a formulation of the analytical method to solve boundary-value problems of axisymmetrical uncoupled quasi-static thermoelasticity in finite deformations. Finally, we show some potentials for axisymmetrical thermoelastic problems of finite deformations.

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Thermal stress and thermal displacement of rubber like elastic solids which has nonlinearity geometrically and physically must be analyzed by means of nonlinear thermoelasticity. Previous to this report we showed a formulation of the analytical method for axisymmetrical uncoupled quasistatic problems of thermoelasticity in finite deformations. In order to examine the effectiveness of this formulation, by way of simple example, we calculate the stress components and the displacement components when a steady distribution of temperature is applied to a lateral surface of infinite cylinder of compressible materials and incompressible materials respectively.

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Adaptive boundary mesh generation based on an error analysis scheme called "sample point error analysis" developed previously for the potential problem is extended and applied to the two-dimensional stasic elastic analysis. The errors of each element are determined as the modification to hold the boundary integral equation on points other than the initial nodes, which are referred to as sample points. Boundary element refinement, h-version in this study, is performed with the aid of the extended error indicator defined by the above-mentioned errors multiplied by the corresponding fundamental solutions. Two-dimensional simple problems are analyzed to validate the utility of the proposed method.

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A new iterative soltion of the nonlinear Berger equation for plate bending problems is proposed. The solution is derived by utilizing both the idea of the Kantrovich method and the boundary integral equation method. The present method, named the boundary strip metheod, could reduce the degrees of freedom of the problem to be solved and input data, although the plate configuration and the boundary conditions of the problems are limited to some extent. In order to show the validity of the proposed method, several examples under various boundary conditions are computed. The numerical results are in good agreement with the results obtained by other authors.

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A set of generalized equations which govern the propagation of one-dimensional plane, cylindrical, and spherical waves in elastic media subjected to a time-dependent temperature field is presented. The numerical procedure employs the characteristic relationships on boundaries and on interfaces between media with different material properties while using an explicit finite difference scheme at all other points. Fundamental problems for plane waves are solved for examples, and the results show clearly the propagation of discontinuities in stress and velocity or their slopes due to a step or a ramp heating on the boundary. Comparison of the results with those available from other investigators yields excellent agreement. Results are also given for stress wave propagations in a composite slab consisting of two layers with different material properties.

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The purpose of this study is to confirm the validity of analytical results of CFRP laminated plates under low-velocity impact. The impulsive responses of CFRP laminated plates are analyzed by using the higher-order shear deformation theory and homogeneous anisotropic plate theory. The plate is simply supported on all four sides and is hit by a spherical steel impactor at its center. The impact load is caculated numerically by using the nonlinear integral equation drived from Hertzian contact law. The strain histories on the plate are evaluated from the higher-order theory and the numerical impact load histories obtained above. The theoretical strain histories are in good agreement with the experimental results obtained by strain gauges. Thus, it was shown that the results obtained from this study could explain not only qualitatively, but also quantitively, the impact characteristics which depend on the stacking sequence of unidirectional prepreg.

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A unified description of the tensile flow curve of metals has been presented by assigning a new role to the internal structure variable which is a fundamental variable in the random barrier theory. This description comprising intergranular hardening has provided satisfactory agreement with each experimental curve for stainless steel, nickel-chrome steel, brass and aluminum alloy with a wide range of strain. The various strain hardening behaviors can be systematically expressed with this formula by introducing the variations of the internal structure variable depending on the deformations.

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The macroscopic elastic constants of alumina are calculated by the finite element method based on a plane model of polycrystalline ceramics. The microscopic stress and strain in the uniaxial elastic deformation are also analyzed considering the pore in ceramics and the elastic anisotropy of the crystal grain. As the porosity increases, the macroscopic value of Young's modulus decreases and the calculated relation between them agrees with the well-known experimental equation. The microscopic stress and strain concentrations around a pore are affected by Young's modulus of the grain and are dependent on the position of the pore on the grain boundary. The maximum values of stress and strain change with the porosity, and the influence of the position of the pore is large when porosity becomes large. In the case when a pore exists on the grain boundary nearly perpendicular to the stress axis, the maximum values are at the region around the grain having a large value of Young's modulus.

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The recent study of the constitutive model for cyclic plasticity aims at the adequate description of additional hardening due to nonproportional cyclic loading, especially circular loading or, generally, sinusoidal loading. There is no constitutive equation which can describe additional hardening of nonproportional cyclic loading accurately. The authors have previously proposed the constitutive model for nonproportional cyclic loading, which could be called the hybrid constitutive model because the construction of the model is completed using the experimental results and the numerical simulation complementarily. In this study, additional hardening due to sinusoidal loading was carefully examined using SUS304 stainless steel, and the proposed model was applied to it. As a result, computer simulation based on this hybrid constitutive model can accurately describe the sinusoidal loading.

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The previous papers published by the authors discussed the strain-fringe behaviors of polycar-bonate in one-and two-dimensional stress states, and also clarified the dependence of the stress-strain curves on temperature and tensile speed at high temperature. The results indicated the possibility of photoplastic strain freezing. But in some cases of plastic manufacture, the deformation of components is approximately under a plane strain state, giving the rolling and pulling of a wide sheet for example. On account of this, to analyze the strain distribution under a plane strain state by means of photoplastic strain freezing, it is necessary to know the strain-optical behavior at a plane strain state. In this paper, the experiments were carried out based on the plane compress of polycarbonate disk to investigate the strain-optical behavior.

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Friction and wear of the contact surfaces during rolling and sliding should be predicted precisely and then controlled well to develop high-technology in the industry. It is worth noting that recently, materials are coated with ceramics to decrease the damage sustained in rolling-sliding contact. However, the effect of coating with ceramics on wear has not been examined thoroughly. In this paper, an attempt is made to analyze the behavior of the inelastic deformation of S 20 C and SKD 11 coated with SiC during rolling and sliding under a contact pressure sufficient to cause yielding using a finite element method. The effect of ceramic coating on the deformation and the distribution of stresses and strains in rolling-sliaing contact is demonstrated from the viewpoint of the thickness of the ceramic coating layer and the strain hardening of the substrate material.

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Optimization of the layout of plane frames as well as cross sections of the members under constraints of stress and global elastic buckling is presented based on the finite-element method and sequential linear programming. The critical load of in-plane global buckling is determined based on linear buckling analysis. Unlike the conventional shape optimization of cross sections, the nodal coordinates of the members as well as cross-sectional dimensions are constituents of design variables. When stress in a certain member is extremely low, or the length of a member or a cross-sectional dimension is extremely small, the member is removed according to given rules and thus the layout of the frame is automatically altered. Some examples of the minimum weight design of plane frames are presented. They show the availability of the proposed method.

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Short cylindrical shells subjected to lateral loads buckle in shear buckling modes. Effects of geometrical imperfections are investigated by developing a special-purpose FEM program using the 8-node isoparametric shell element. Four types of imperfections, local dents, Fourier harmonic modes, axisymmetric imperfections and their superpositions, are taken into account. It is shown that geometrical imperfections do not have much effect in shear buckling in comparison with the axial buckling, and guantitative relationships between impeffection amplitudes and buckling loads are obtained.

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This paper deals with the two-dimensional rolling-sliding contact problem with frictional heat generation on an elastic half space containing a surface breaking crack. Rolling-sliding contact is simulated as an arbitraly distributed contact load with normal and shear components, moving with constant velocity over the surface of the half space. The frictional heat generation on the contact region is estimated by using of sliding velocity, frictional coefficient and contact pressure. Numerical results are given for the cases of Hertzian and parabolic distributed loading respectively. The effects of slide/roll ratio and frictional coefficient on the stress intensity factors are considered.

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In ferromagnetic materials, ultrasonic velocity varies with both stress and external magnetic field. This phenomenon occurs due to the magnetoelastic interactions, and it is called magnetically induced velocity change (MIVC). The behavior of MIVC depends on the stress, magnetic field, ultrasonic mode (longitudinal or shear), and their relative orientation including the polarization direction of the shear wave. Its magnitude is of the order of 10^-5, being comparable with the acoustoelastic effects. In the present study, the MIVC for longitudinal and polarized shear waves were first measured with mild steel specimens for the changing magnetic fields applied parallel or perpendicular to uniaxial stresses. The MIVC curves thus obtained showed salient dependence on the stress. They were then used to nondestructively evaluate the thermomechanical residual stress introduced by gas cutting. The results agreed with the strain gage measurements and the conventional acoustoelastic methods, both destructive, showing the usefulness of the MIVC method to measure residual stresses nondestructively. The MIVC was found to be insensitive to the micros-tructures.

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The caustics method is simulated by three-dimensional finite element analysis. CT specimens with different thicknesses and different crack front shapes are analyzed and the crack tip fields are compared with HRR solutions. Caustics are also drawn using the displacement field obtained by the FEM analysis. It is shown that the caustics method can estimate the J-Integral value with good accuracy when the initial curve is located in the limited region where the stress fields agree with the HRR solutions. The diameter of the caustics is measured experimentally by using the same CT sepcimens, and it is shown that the experimental results agree with those of the numerical simulation well. It is concluded that numerical analysis is necessary to estimate the location of initial curves to accurately measure the elastic-plastic fracture parameter J.

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An optical technique for rapidly measuring surface roughness using a laser is proposed. The reflected intensity distribution of a laser beam irradiated on a surface of an aluminum specimen was measured with a plasma-coupled device (PCD). The reflected intensity curve can be approximated by a Gaussian function. The broadness of the intensity curve was evaluated with the standard deviation, called a Gaussian curve parameter (GCP), of a Gaussian function approximating the intensity distribution curve. The GCP can be determined in 2s. The smoothing of the reflected intensity data is not necessary in calculating GCP because GCP's with and without data smoothing almost agreed. The center line averaged roughness R_a increases with increasing GCP.

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This paper describes the development of a novel automatic FEM mesh generation system based on the fuzzy knowledge processing technique. Here, a number of local-optimum nodal patterns for stress concentration fields are stored in a nodal pattern database. The "closeness" of each nodal location to the stress concentration field is expressed in terms of a membership function. In mesh generation process, several nodal patterns are first placed in an analysis domain, and extra-nodes are removed by the fuzzy knowledge processing technique. Then, either triangular or tetrahedron elements are generated in the two-or three-dimensional domain, respectively. The major advantages of the present method are summarized as follows: the ambiguity appeared in mesh generation processes is naturally taken into account, and by controlling a fewer input data, a user can generate a quasi global-optimum mesh for a whole analysis domain including several stress concentration fields. The system is developed with Smalltalk-80 on Macintosh II for the purpose of easy management as well as future extension. The performance of the present method is demonstrated through the mesh generation of several two-and three-dimensional domains.

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The compartment tank has attracted much attention in recent years because various kinds of oil can be stored simultaneously in one tank. The coaxial cylindrical tank, which is one type of compartment tank, has been studied energetically because of its simple shape. In the seismic design of oil storage tanks, the analysis of vibration coupled with fluid motions is required by the Fire Service Law. This paper describes the development of a seismic design system for coaxial cylindrical tanks using a 16-bit personal computer. The purpose of the development is to design the tank efficiently, and to reduce the number of man-hours required for the design.

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