A frictionless, axisymmetric contact problem is considered. In this problem, an elastic half-space is pressed onto a rigid foundation with a spherical-ended protrusion and the contact area between the rigid foundation and the half-space varies with the magnitude of the applied pressure. The problem is reduced to an infinite system of simultaneous equations with Papkovich-Neuber stress functions in oblate spheroidal coordinates. Special attention is given to the variations of the size of the contact area with the applied pressure. Numerical results are given for the distributions of the surface displacement and the contact stress. Comparison is made with other relevant numerical results available.

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The elastodynamic response of symmetric edge cracks in an orthotropic strip under normal impact is considered in this study. Two edge cracks perpendicular to the edges of the strip are placed symmetrically. Laplace and Fourier transforms are used to reduce the transient problem to the solution of a pair of dual integral equations in the Laplace transform plane. The solution to the dual integral equations is then expressed in terms of a Fredholm integral equation of the second kind. A numerical Laplace inversion routine is used to recover the time dependence of the solution. The dynamic stress intensity factor is determined and numerical results for some practical materials are shown graphically to display the influence of the material orthotropy.

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This paper is concerned with an analytical formulation and a numerical solution of the elasto/visco-plastic problems of multi-layered moderately thick shells of revolution under asymmetrical loads with application to a cylindrical shell. The analytical formulation is developed by extending the Reissner-Naghdi theory on elastic shells. It is assumed that the total strain rates are composed of an elastic part and a part due to visco-plasticity. The elastic strains are proportional to the stresses by Hooke's law. The visco-plastic strain rates are related to the stresses according to Perzyna's equation. As a numerical example, the elasto/visco-plastic deformation of a two-layered cylindrical shell composed of a titanium and a mild steel layer subjected to locally distributed loads 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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A structure optimized for a given determinate load is not optimum for other loads. This paper proposes a shape determination method by BEM for structures which are subjected to uncertain loads. In the case that the loads are represented by some random variables which obey certain probabilistic laws, response quantities such as displacement and strain energy can be expressed as random variables by the use of a method of "decomposition into fundamental loads". Then only several runs of analysis can give optimum shapes where the expected values of strain energy densities are uniform on every boundary element.

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This paper deals with a FEM analysis of temperature distribution on a workpiece whose shape changes during machining. A calculation method involving the node movement accompanied by heat source movement during machining is proposed. The accuracy of the solution is influenced by the calculation parameters : number of moving surfaces, aspect ratio of finite element, moving distance and time step of calculation. The method proposed reduces the total number of nodes, and hence the CPU time is shortened in the calculation. The method is adopted for several cases of different heat transfer coefficients and workpiece materials.

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In order to study high-speed deformation of materials, a high-speed digital video camera has been developed by using a new MOS-type solid-state image sensor. The frame speed is controlled by a personal computer, and the maximum frame speed is 300 000 frames/s. The digital image taken by the high-speed video camera is analyzed by an image-processing system using a personal computer. In order to analyze the strain rate distribution, a new grid method using Fourier transform is developed. Through the use of this method, displacement, strain, velocity and strain rate distributions in a rubber tube in which an unloading wave is propagated are analyzed.

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High molecular materials are generally used for many inportant structural members of machines, in spite of the present circumstances where the ductile fracture characteristics are not sufficiently known. The present study has been directed to determine the plastic strain concentration factor at the edge of a round-hole under the uniaxial stress field. Plastic strain concentration factors at the edge of a round-hole notch were measured by photoelastic stress analysis technique under defferent tension rates. Concentration factors were calculated from results obtained, and the experimental result was compared with the theoretical values. Fairly good agreement was found between them.

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A contact pressure distribution in jointed plates is investigated by means of an ultrasonic technique, especially by varying the flatness of the joint surface. At first, the relations between the contact pressure and sound pressure of a reflected wave measured by using a normal probe and angle probes are obtained by compressing calibration blocks under various surface roughnesses. Next, when two rectangular plates and two disks with a circular hole are compressed under various convex flatnesses of the joint surface, the sound pressure of the reflected wave is measured by using the normal probe and the angle probes. From the relations between the calibrated and measured curves, the contact pressure distribution in these jointed plates is quantitatively obtained. The experimental results are graphically presented and are compared with the analytical ones. It is clarified that the contact pressure distribution is significantly influenced by the small flatness deviation. Thus, the proposed ultrasonic method is practically useful for the measurement of contact pressure.

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Fundamental investigations are made regarding the phenomena of slip band initiation and grown grain initiation in an electroplated copper foil under variable amplitude stress which consists of overstress and understress. The applicability of the copper foil to the fatigue gauge which detects fatigue damage is discussed. It is found that the modified Miner's rule does not hold for the slip band and grown grain initiation under two-level single block loading and two-level multiple loading composed of overstress and understress. The cumulative cycle ratio in these cases is dependent on load history. It is also found that fatigue damage during understress applied after overstress is greater in the early period of the cycles. The deviation from the modified Miner's rule, however, can be said to be small. Furthermore, it is found that the fraction of grown grains initiated under variable stress is dependent on the equivalent stress. This enables the evaluation of the equivalent stress based on the fraction of grown grains.

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Cyclic thermal transient fatigue tests of dissimilar weld joints of SUS304 and 2.25 Cr-1Mo steels with Inconel 82 buttering were performed in order to study the general behavior of crack initiation and growth, including crack locations, directions and densities under the respective loading conditions. The crack initiation sequence at different parts of the test models corresponded well with the result of analytical prediction using the finite element method. The results suggest that counter bore machining near the buttering boundary with 2.25 Cr-1Mo steel must be kept sufficiently apart from the joint area. The allowable number of thermal transient cycles according to the ASME CODE CASE N-47 and the elevated-temperature structural design guide developed by the PNC (Power Reactor and Nuclear Fuel Development Corporation)was shown to have a considerable Safety margin compared with the crack initiation data of 1 mm in depth at all parts of the pipe models.

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A new method is proposed to evaluate the strength of a sharply notched structure with a large notch angle. A new parameter, K_e which is to be called the equivalent stress intensity factor and which prescribes the singularity of stress distribution near the notch tip, is defined to evaluate the effect of a sharp notch on the fatigue and static strength. This method makes it possible to predict the strength of a notched structure by using the well-known parameters ΔK_th and K_Ic. Fatigue tests of HT60 (600 MPa-class high-strength steel) and SS41 (400 MPa-class mild steel) and a brittle fracture test of an acrylic plate were conducted, and the applicability of the parameter was verified.

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Uniaxial tensile tests on Ti-Ni alloy wire under cyclic loading and unloading were carried out. The influences of maximum strain, test temperature, and shape memory processing temperature upon the cyclic characteristics of pseudoelasticity were examined. The results obtained are summarized as follows. (1) Starting stress of stress-induced martensitic transformation decreases with the number of cycles. The rate of decrease takes an almost constant value without depending on the test temperature and maximum strain. (2) In the region of stress-induced martensitic transformation, residual strain in each cycle increases with test temperature. (3) The change of strain energy per unit volume for the number of cycles becomes larger in the order, dissipated strain energy, total strain energy, and recoverable strain energy. (4) Yield stresses of stress-induced martensitic transformation and reverse transformation decrease with the shape memory processing temperature. (5) The transformation strain range at each 1OOth cycle takes a maximum value at a certain shape memory processing temperature. (6) Every characteristic value of pseudoelasticity varies significantly in the early cycles, but becomes stable after these cycles.

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In the design of a shape memory alloy helical spring, a basic method of designing the spring based on the stress-strain-temperature relation of the material is an important problem to be solved. In the current study, the deformation behavior of the shape memory alloy helical spring was analyzed based on stress-strain-temperature relation of the material. The relationship between load and deflection of the spring as well as the behavior of transformed region is discussed. The main results are summarized as follows. (1) The relation between the load and deflection of the spring is represented by using a simple model of the stress-strain-temperature relation. (2) For a certain maximum deflection, recoverable force and recoverable strain energy increase with temperature. Dissipated strain energy takes a maximum value at a certain temperature. (3) The transformed region in the cross section of the wire expands into the center from the surface under the loading process, but contracts toward the surface under the unloading process. For a certain maximum deflection, the transformed region is small but the load increases as the temperature increases.

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The microscopic process of ductile fracture in the process zone is studied in this paper. First, the FRASTA (fracture surface topographic analysis) technique is used, and the ductile fracture processes of two kinds of aluminum alloys, 7075-T6 and 2017-T4, are observed. The nucleation, growth and coalescence of voids are observed in detail. The finite element analyses based on Gurson's model are then carried out. The element vanishing method is used with the finite deformation theory. Using the void volume percent as the fracture criterion, the nucleation and growth of voids and coalescence with the crack are simulated. It is shown that these phenomena occur in the process zone, and the numerical results agree qualitatively with the experimentalones.

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An extended model is proposed for lung respiration. This model is made to cope with gas diffusion by convection in the airway network, gas exchange at the alveolus, gas transport by blood flow, and gas flow in the airway network induced by diaphragm motion. The submodel for each phenomenon is combined into a total respiratory system, and it is formulated in the context of discretization based on the adjoint variational principle. First, the normal respiration and then the high-frequency ventilation (HFV) are studied by means of this model. The effects of HFV are evaluated through several case studies and it is quantitatively shown that the influence of the convective diffusion is dominant in the gas transport of HFV. The proposed model is expected to be used to determine proper parameters of HFV.

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