X-ray stress measurement was applied to epoxy resin containing several volume fractions of alumina particles ranging from 4.5 % to 37.2 %. The diffraction from the (2.1.10) plane of alumina particles by Fe-Ka radiation was used for stress measurement. The diffraction intensity increased with the increasing alumina volume fraction. The stress in the alumina was proportional to the applied stress. The proportional constant was between 2.5 and 2.9, increasing with decreasing volume fraction. The self-consistent model estimated the phase stress of alumina to be about 70 to 80% of the experimental value. The macroscopic stress of alumina filled epoxy can be obtained from the X-ray measurement of alumina strain by using X-ray elastic constants.

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A finite deformation/finite-element analysis is performed on the necking behaviour of laminated plates consisting of two materials with different work-hardening coefficients. The plates are subject to a prescribed uniform axial displacement at both ends. The plane strain condition is assumed and the J₂-flow theory is adopted. The results obtained are as follows. (1)For the plate with shear free ends, the load-displacement curve before the necking point can be obtained by averaging the two stress-strain relations of both materials. The necking point can be predicted from the compound load-displacement curve. (2)For the plate with clamped ends, the necking behaviour is affected by the order of lamina location. The necking of the plate with the softer lamina located on the outside occurs more easily than that for the opposite location of laminas. The development of the unloaded region is also influenced by the lamina location. (3)A slight delamination has little effect on the load-displacement curve before the necking, although it has a considerable effect on the deformation behaviour after the necking occurs.

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Axisymmetric deformation of an anisotropic porous material is analyzed. A model of the material is proposed ; the material consists of ellipsoidal cells each of which has an ellipsoidal pore in the center of the matrix. The velocity field in the matrix is assumed and the upper bound approach is attempted. The yield criterion of the porous materials with various volume fractions of pore V_f is represented as ellipses on the σ_m-σ₃ (the hydrostatic and principal stresses) plane. Their axes become smaller with increasing V_f and rotate clockwisely or counter clockwisely at an angle δ from the σ_m axis. The angle δ increases with increasing anisotropy. The direction of the rotation is dependent upon the aspect ratio of pore.

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A numerical method which has been presented by the authors is extended to the computation of the transient waves in a composite laminated plate excited by a point impact load. The laminated plate is divided into N plate elements, and the principle of virtual work is applied to reduce the three-dimensional equation of motion to a two-dimensional one. The method of Fourier transforms in conjunction with modal analysis is used to determine the response of displacements. Two numerical examples are computed and discussed; one is for an isotropic plate and the other is for a hybrid composite laminated plate.

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Instrumented Charpy tests were carried out for sintered W-Ni-Fe alloys in order to clarify the effects of notch radius on impact strength. Sintered 93.0W-4.9Ni-2.1Fe and 97.2W-2.0Ni-0.8Fe (in wt%)heavy alloy specimens were prepared. Notch radii of the specimens used were 1.0, 0.2 and 0.08 mm. The maximum load and the absorbed energy decreased with reducing notch radius. SEM fractography of impact specimens revealed a large amount of cleavage failure of tungsten grains. However, the absorbed energy corresponded well with the fraction of ductile fracture surface formed by the failure of matrix. Plastic strains near the fracture surface were measured by a grid method. The results indicated that the plastic zone size induced by an impact test was reduced as the notch radius decreased. On the basis of the observed plastic zone and the Rice-Rosengren-Hutchinson model, the estimated plastic works for the impact test specimens were close to the experimental absorbed energies.

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The fatigue crack growth properties for a low-alloy steel, Cr-Mo-V, and two stainless steels, types 403 and 304, were investigated at 550°C in air under two sawtooth loading waveforms of slow-fast and fast-slow, and three trapezoidal waveforms of tension hold, compression hold and tension-compression hold. The effect of the waveform was obvious for Cr-Mo-V and 304 steels in the crack growth, while the crack growth rate was almost independent of waveform for 403 steel. A mixed mode transgranular and intergranular fracture was observed for 304 steel, while the transgranular fracture was predominant for 403 steel. The oxide layer formed on the polished surface in a furnace was thicker on Cr-Mo-V steel than on 403 and 304 steels. From these results, it was found that the controlling factor for the waveform effects on the elevated temperature fatigue crack growth properties could be attributed to the oxidation for Cr-Mo-V steel and the creep damage for 304 steel ;these two damaging phenomena, however, had little effect on 403 steel in this experiment.

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The influence of amplitude of a tensile stress pulse on the dynamic fracture behavior of a cracked plate is investigated. The specimen is a cracked plate made of epoxy resin. A tensile stress pulse, whose amplitude and duration are controlled, is generated by an impact apparatus and travels through a cracked plate. The crock propagation phenomenon and the behavior of the stress -intensity factor at the crack tip are analyzed by the photoelastic technique using a high-speed camera. The crack propagation angles for several amplitudes of stress pulse are measured. From these experimental results, the influence of amplitude of a tensile stress pulse on dynamic fracture behavior of a cracked plate is considered.

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Brittle fracture surfaces of chromium were observed with scanning tunneling microscopy (STM). STM images obtained were analyzed by fractal geometry. Brittle fracture surfaces of chromium had self-similarity (i.e., fractal character) even at very high magnification such as ×10⁶. The relevant fractal dimension was about 1.05.

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The method that the present authors have recently proposed on using the finite element method has been incorporated into a boundary element method to analyse twodimensional elastostatic stress intensity factors. Namely, the present method is based on the expectation that the ratio of the resultant force around the crack tip in the theoretical value and the numerical one is constant. Numerical-emprical formulas for stress intensity factors of the mode I and II deformations are established from the results of stress analysis for the strips with central crack and the rectangular plates with contral inclined crack, respectively. The linear strain element has been used to the calculations of stress for the cracked plates. The usefulness of the method has been tested with a number of plates with crack, and the results have turned out to be fairly satisfactory.

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Residual stresses caused by various thermal histories in a structural member occasionally affect the strength of the structure. Therefore, accurate estimation of the residual stresses is practically very important. In the present paper, inverse analysis based on the boundary element method (BEM) was formulated and applied to identifying residual stresses in an axisymmetric elastic body. Cylindrical pipes with various dimensions were taken for example, and location of the residual stress source, which was approximately replaced by appropriate body forces, was numerically searched. It was found that the evaluation parameter R₁, the sum of axial directional body forces, is one of most useful indices for the location search of acting body force in the inverse analysis.

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In spite of a number of attempts to develop an automatic system of photoelastic stress analysis with a microcomputer, there still exist several difficulties in accurate treatment of digital image data. In this paper, the authors describe a new theory and its application regarding the automatic calculation of stress components on an appropriates Cartesian coordinate from several photoelastic images, using a microcomputer. Two new concepts, namely, 1) the local polynomial expression of Airy's stress function, and 2) the relativity of boundary values, are proposed here, in addition to the well-known equations of the light intensity in photoelasticity and the coordinate transformation of stress components. Based on the above concepts, the expression of each stress component using spline functions on a Cartesian coordinate is easily calculated by the least squares method. An application of this method shows much better accuracy of analysis which is unaffected by generation and propagation of errors, in comparison with the former methods published to date.

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It is well known that the most difficult and laborious problems in photoelastic stress analysis are determination of principal stress direction and assignment of fringe order over the whole area of a specimen. In a series of studies reported previously, however, the authors successfully proposed a new method for the whole-area analysis in two-dimensional photoelasticity based upon a concept of structure-driven-type image processing. This paper describes a newly developed method for auto-matic drawing of isostatics, i. e., stress trajectories, and separation of principal stress with a differential geometry method using isoclinic and isochromatic data obtained by the whole-area analysis mentioned above. Applicability of the method is investigated by comparison of the results obtained for both theoretical and experimental data.

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Although body force method (BFM) is very suitable for numerical analysis, the versatile program for general purpose has not been given until now. In this paper, the basic theory useful for analyzing the general two-dimensional elastic problems is presented based on BFM, in order to get such a type of program. The fundamental point of the present method is not to use numerical integral at all, in spite of using BFM which is a boundary type method of numerical analysis. Because of this, it has become possible to obtain the solution with high accuracy easily for various kinds of two-dimensional elastic problems, by using a standard personal computer.

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When a transversely isotropic hollow sphere is suddenly subjected to a uniform temperature rise over its cross section, stress waves occur at the internal and external surfaces the moment thermal impact is applied. The stress wave at the internal surface proceeds radially outward, while the one at the external surface proceeds radially inward. During instantaneous heating, the interference effects of these waves can cause a very high dynamic stress for both tension and compression in the spherical shell. This paper analyzes the effects of these waves precisely using the ray theory. The numerical results indicate the variations in the dynamic stresses in a transversely isotropic spherical shell with time and show the effect of anisotropic properties explicitly.

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Abstract-This paper considers the thermal singular stresses of G10-CR glass/epoxy laminates with a T-shaped crack at low temperatures. The T-shaped crack consists of an interface crack and a crack perpendicular to the interface. The composite material in generalized plane strain is assumed. The problem is formulated in terms of a coupled system of four integral equations. The integral equations are solved by using a Gauss-Chebyshev integration formula. Numerical results on the thermal stress intensity factor at different temperatures are obtained and presented in a graph form.

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A transient plane-stress thermoelastic problem in a nonhomogeneous hollow circular plate of variable thickness is formulated in terms of a stress function by deriving new Michell integral conditions necessary for the assurance of single-valuedness of rotation and displacement. An analytical solution is presented for thermal stresses in a nonhomogeneous hollow circular plate subjected to unaxisymmetic heating on the boundary surfaces, which has the plate thickness, Young's modulus and thermal conductivity in forms of different power laws of the radial coordinate; the coefficient of linear thermal expansion is given as an arbitrary function of the radial coordinate. Numerical calculations are carried out over a wide range of the nonhomogeneous thermal conductivity, Young's modulus, coefficient of linear thermal expansion and plate thickness. The effects of nonhomogeneous thermal and mechanical properties on the relaxation of thermal stress and its application to the design of functionally gradient materials (FGM) are discussed.

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Strain-rate and temperature dependence on the flow stress of OFHC copper is discussed. Tensile tests were made ranging in strain-rate from 2.5 × 10^-4 s^-1 to 1 s^-1 and temperature from 25°C to 600°C with a cam-plastometer type testing machine built as a trial. Experimental results were compared with a theory proposed previously by the first author for constitutive relationships of elastic/visco-plastic materials. On the temperature and strain-rate range discussed in this paper, it was recognized that three fields of deformation mechanism exist. The proposed equation represented well constitutive relation in individual field and correlation of neighboring fields. Significant variations of final reduction in area and total elongation also were discussed in connection with transition of deformation mechanism.

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Strain-rate and temperature dependence on the flow stress of mild steel is discussed. To investigate the influence of grain size and carbon content, low carbon steel S 15 C and S 35 C annealed at different temperatures were prepared. Tensile tests were made ranging in strain-rate from 2.78 × 10^Z<-4>s^-1 to 1.39 × 10^-1 s^-1 and temperature from -33°C to 700°C with an Instron-type testing machine. Experimental results were compared with a theory proposed previously by the first author for constitutive relationship of elastic/viscoplastic materials. The proposed equation represented well experimental results of constitutive relations except the blue brittleness region. Elongation, reduction in area and superplasticity of materials were discussed in connection with deformation mechanism regions.

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The growth-strain method was previously proposed as a shape optimization method which is the deforming of shapes by generating bulk strain. Hitherto, we have shown that the uniform-strength shapes can be analyzed by the method where the bulk strain is generated according to the magnitude of a strength parameter. The objective of the present paper is to devise the formulation of the method in order to apply it to maximum-stiffness shape analysis. First, by reforming the inverse variational principle of the principle of minimum potential energy, we obtain a uniform condition of the potential energy density as a necessary condition to obtain maximum stiffness. Based on the theory, the proposed formulation is to set the potential energy density on the generation measure of the bulk strain. The effectiveness of this formulation is examined on beam and column problems. The notable advantage is confirmed with the latter problem.

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In this paper, a system of external force in the human femur is evaluated by using the methods proposed previously by Chanley, and others. The results are applied to analyze the strain distributions in the human femur. In the analysis the beam theory and the three-dimensional finite element method are used. The obtained axial value reaches the maximum value at the diaphysis of the human femur. On the other hand, the strain values obtained by the beam theory agree approximately with the values by the finite-element method expect for the values of the parts of the caput femoris and the fossa intercondylaris. From these results, the applicability of the beam theory to the strain analysis of the human femur is dicussed.

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A new simplified element model for the limit analysis of thin shells combining the rigid bodies-spring model for the bending deformation and the constant-strain finite element for the in-plane behavior is proposed. This discrete model is so simple that the stiffness matrices can be derived explicitly both for elastic and plastic deformations, and each node has only three degrees of freedom which are three-dimensional translational displacements. Therefore it is expected that the computing cost can be considerably reduced, although the computational accuracy is a little distorted. The first report of the present study contains the formulation by the total Lagrangian approach and its applications to the ultimate strength analysis of flat and curved plates. The validity of the present method is confirmed by comparing the calculated solutions with the results of conventional finite element shell analysis.

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The new discrete element model for the limit analysis of thin shells proposed in the preceding report is extended to the crush analysis accompanied by extremely large rotations and deformations. The formulation is conducted according to the incremental theory by the updated Lagrangian formulation with the redefinition of element coordinate systems at each loading step. The present discrete model is so simple in its mathematical nature that considerable reduction of the computing cost can be expected in highly nonlinear analyses such as crush analysis. Numerical studies are conducted forthe crushing behavior of circular cylinders and square tubes under axial compression as well as the nonaxisymmetric elastoplastic snap-through of an axisymmetric shell container. The calculated results are compared with the existing finite element solutions and the experimental results in order to confirm the validity of the present method.

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In boundary element analysis using the zooming method. the error of the stress at the selected point is expected to be smaller than the sum of two errors. One is the error caused by the mesh diameter of the original boundary. The other is the error of displacement on a zooming boundary. Using the self-adaptive mesh refinement technique, the former becomes smaller than the allowable error. The latter can be estimated by the relation between the mesh diameter and the error in the recursive analyses. A computer program using this error estimation method was developed and applied to several problems of various shapes. The usefulness of this accuracy estimation method was illustrated by these application results.

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Although it is possible and effective to obtain numerical solutions to differential equations which dominate observed phenomena in experiments, indiscriminate use of the conventional formulas in numerical differentiation leads to poor accuracy in analysis. The authors propose new theories and algorithms not only for analysis of the differentiable structure of a representative function for experimental data but also for treatment of errors due to noise. The numerical differentiation formulas are derived from the concept of differentiation of smoothing polynomials. Namely, the least squares approximation in terms of the central difference is adopted using local quadratic functions with a single variable. Taking two dimensional photoelastic data, that is, isochromatics and iso-clinics, as examples, several differential equations are examined. The results show that the new approach is applicable for quantitative evaluation of stress with good accuracy.

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The expert system, that diagnoses the sensitivity of stress corrosion cracking of austenitic stainless steels in a low-and high-concentrated chloride solution and/or high-temperature water, has been developed using the OPS 83 programming language: the knowledge base was constructed with production rules, which had certainty factors to represent the contribution of each rule to stress corrosion cracking. Goal directed inference method was adopted for reasoning. The knowledge base consisting of 110 rules covered the rules of environments, materials, loading and their interactions as well as fracture surface morphologies. Applying this expert system to the case histories of stress corrosion cracking, the diagnoses of stress corrosion cracking were accurately made.

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