Fretting fatigue strengths are improved by making grooves at the contact edges of specimens and knurlings on the contact surfaces of pads. These improvements are estimated by stress analysis and fracture mechanics analysis, and are confirmed by fretting fatigue tests. Stress intensity factors at the tips of cracks growing from the contact edges are calculated by the Boundary Element Method stress analysis. Finally the optimization of groove shapes such as radius and depth are discussed.

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In this paper, we have attempted to formulate precisely a generalized acoustoelastic theory by extending the theory proposed by Kobayashi [1987], which was derived to evaluate the acoustoelastic effects of ultrasonic waves induced by slight orthotropy in elasticity and plastic anisotropy growth in the plastically deformed solids. Mereover, in order to examine the accuracy of the proposed theory, the numerical calculations of the transverse wave velocity changes in elastoplastic range were carried out and compared with the experimental data on a commercially available pure aluminum specimen subjected to uniaxial tension. The good agreement between theoretical and experimental results indicates that the plastic anisotropy is closely related to the acoustoelastic effects through the elastoplastic coupling strain-rate induced by the vertex-like yield effects at the corner of the yield surface.

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The strength of the stepped-lap bonded joints with similar adherends is investigated both analytically and experimentally. The effect of an aspect ratio that is varied by an increase in the overlap length under constant adherend thickness on the joint strength is discussed to establish the practical method of the strength design of adhesive bonding structures. The joints used in this study have adherends of carbon steel, brass and aluminum alloy and adhesive of epoxy resin. The strain and stress distributions under a tensile shear load are analyzed by applying finite element method in the above mentioned joints. This analytical strain distribution shows good agreement with experimental ones. The strength of the joints is predicted by applying the strength laws to the adherend, adhesive and their interfaces. Only in the case of adherends of carbon steel, final fracture strengths of the joints increased with the overlap length. The predicted results are nearly equal to the experimental initial fracture load.

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A pulsed holographic technique is described which records and reconstructs caustic light beams of fast propagating cracks in polymethylmethacrylate (PMMA). A caustic light beam of a fast propagating crack is recorded as a hologram at an instant during its propagation with a pulsed holographic recording system. Illuminated with reconstruction light, the hologram reconstructs the caustic light beam, and diameters of caustics at various distances from the specimen are measured from the reconstructed caustic light beam. Values of dynamic stress intensity factor K₁ and initial curve radii are calculated from the caustic diameters. The initial curve radius at which calculated K₁ values deviate from the real K₁ value gives the scale of the three-dimensional stress field which appears around the fast propagating crack tip. In the case of cracks propagating through specimens 3mm in thickness, the 3-D stress field spreads as far as the distance of half of the specimen's thickness from the tip.

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This paper deals with the thermal shock problem of a flat plate with an edge crack, initially at uniform temperature, being suddenly cooled on the plate surfaces. It is assumed that the thermal disturbance near the crack surface may be neglected in the analysis of the temperature field of the elastic solid with a crack because thermal shock occurs rapidly. We analyed the transient thermal stress problem of a flat plate with a crack and determined the stress intensity factor at the crack tip. The nondimensional maximum transient stress intensity factor is expressed as a function of Biot's number and the nondimensional crack length. We then proposed a simplified formulation of the nondimensional maximum transient stress intensity factor as a function of Biot's number and the nondimensional crack length.

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This study investigates the problem of applying fracture mechanics to evaluation of the strength of adhesive joints. Various types of adhesive joint specimens with a crack in an adhesive layer are prepared for the fatigue tests and static tests. The adherend is acryl plate and the adhesive is cemedine 1500. The energy release rates G_I and G_II for various adhesive joints are analyzed by FEM and modified virtual crack extension method. Comprehensive mixed mode conditions from pure mode I to nearly pure mode II are realized in this study. In all adhesive joint specimens, the debonding fatigue crack grows along the adhesive interface. It is found that the fatigue crack growth rate in various adhesive joints can be well characterized by the total energy release rate range ΔG_T, which can be evaluated by the measurement of compliance. However, the fracture toughness results obtained using the same specimens show a mixed mode fracture criterion for adhesive joints, which can be characterized by G_I and G_II. Therefore, different approaches are necessary for the fatigue crack growth and fracture toughness of adhesive joints.

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Cylindrical shell structures are used for many storage tanks and containment vessels. In these designs, seismic strength should be taken into account. In this paper, the interactive relations of static buckling between lateral and axial loads, and dynamic buckling under harmonic excitation are studied for fluid-filled and empty tanks, which are opened or closed at the upper ends. Static and dynamic buckling tests are carried out, using small polyester tanks. The static buckling stress criterion for a long cylinder subjected to pure bending is applied to the test results of the fluid-filled tanks under harmonic excitation. the static buckling stress criterion, considering the ovalization of the cross section, is also applied to the test results for empty tanks under harmonic excitation. The static buckling criteria prove to be fairly applicable to both fluid-filled and empty tanks in the restricted region under the natural frequency of the fundamental mode.

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One-dimensional generalized thermoelasticity is presented based on the Green and Lindsay's theory, which involves two relaxation times of the thermoelastic process. Similar to Lord and Shulman's theory, this theory was also developed in an attempt to eliminate the paradox of an infinite velocity of thermoelastic propagation inherent in the classical theory. The analytical object of this paper is an infinite body with a circular cylindrical hole. The boundary condition is that a constant heat flux is flowing into the infinite body from a circular cylindrical hole but the displacement at the hole is constrained. An approximate analysis for short times is carried out. the numerical results of the effects of relaxation times on displacement, temperature and stress distributions are shown and compared with the results based on Lord and Shulman's theory.

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This paper is concerned with the theoretical treatment of thermal stress problems involving a multilayered anisotropic laminated slab in a transient state. As an analytical model, we consider an infinitely long laminated slab consisting of an oblique pile of layers having orthotropic material properties, i.e. an angle-ply laminate. We solve the thermoelastic problem of the slab for a case where there is a uniformly distributed heat supply from its surfaces. Introducing a method of Laplace transform for the temperature field, we obtain the temperature solution with the aid of the residue theorem, and evaluate the thermal stresses in a transient state using the elementary plate theory. As an example, we carry out numerical calculations for a 5-layered angle-ply laminate, and evaluate thermal stress distributions for in-plane deformation under the condition of symmetric heat supply, and examine the influence of ply-angle affected the thermal stress distributions.

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The boundary element method (BEM) has been developed in various fields of engineering. One of the greatest advantages claimed for the boundary element formulation of an isothermal elastic problem without body forces is that the problem is described in a boundary integral equation without integration over the whole region. However, in BEM formulation of the thermoelastic problem, the term of the thermal strain is formulated just as body force in the isothermal elastic problem. so, integration over the whole region is needed, and the region is divided into many elements called cells. This procedure will cancel out the above-mentioned advantage. In this paper, we deal with the BEM formulation of the axisymmetric thermoelastic problem. The problem is formulated without integration over the whole region, introducing the concept of the thermoelastic displacement potential function.

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Fundamental experiments are carried out to examine the parameter that dominates slip band initiation in copper electroplating under the condition where the mean stress as well as the stress amplitude varies. It is found that, in the case of constant amplitudes stressing, the relation between the proper stress σ_p for slip band initiation and the number of cycles N is well represented by σ^α_p·N=C. This mean that slip bands appear when the total hysterisis energy applied to the copper plating attains a critical value. when the mean stress varies stepwise or sinusoidally, the range pair of the stress mainly dominates the occurrence of slip bands, and Miner's rule holds for the accumulation of fatigue damage. Accordingly, the parameter (√σ^α_i)^1/α, where σ_i is the range pair and α is the exponent of the σ_p-N relation, is equivalent to the proper stress under constant amplitude stressing. Based on these results, the applicability of the copper plating to the fatigue gage that accumulates and indicates a load experience is discussed.

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A contact pressure distribution in jointed plates has been investigated by using an ultrasonic technique, especially by varying the flatness of joint surfaces. At first, the relations between contact pressure and sound pressure of reflected waves 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 surfaces, the sound pressure of reflected waves is measured by the normal probe or the angle probes. From these relations, the contact pressure distribution in these jointed plates is quantitatively assesed. The experimental results are presented graphically and compared with an analytical one. It is clarified that the contact pressure distribution is influenced significantly by the very small flatness deviation, thus the proposed ultrasonic method is practically useful for the measurement of contact pressure.

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In order to study the high-speed deformation of materials, a high-speed digital video camera is 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 300000frames/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 strain rate distribution, a new grid method using a Fourier transform is developed. Through use of this method, displacement, strain, velocity and strain rate distributions in a rubber tube in which an unloading stress wave is propagated are analyzed.

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This paper discusses the optimal shape for the wire cross section of a helical spring. In general, stress at the inner side of the coil is higher than that at the outer side in a helical spring with a round cross section. Therefore, weight may be saved through stress equalization effected by improving the shape of the wire cross section. Shape optimization is performed by modification of the cross-sectional shape so as to minimize the weight of the helical spring under the constraints of design stress, spring rate, coil diameter and applied load. Stress caused by torsional moment and shear force is calculated by means of FEM, taking the effect of coil curvature into account. The shape of the wire cross section is successively modified by changing γ_i, which represents the radius from the sectional center to each node on the periphery of the section. The optimized shapes are almost oval and are obtained independent of supposed initial shapes.

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An anisotropic yield function accounting for both the Bauschinger effect and the cross effect is developed in this report. Based on the representation theorem for isotropic tensors, a new yield function, as an extension of the Baltov-Sawczuk theory, is presented. After a short discussion on the anisotropic parameters in the model, the experimental verification is carried out for SUS304 stainless steel at room and elevated temperature levels in a biaxial stress state of tension and torsion. The calculated results show good agreement with the experimental data, especially when prediction the distortion and the translation of the yield surface during the inelastic deformation processes.

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Cavitation erosion behaviors of sintered aluminum oxide and silicon carbide were investigated by a vibratory test. The erosion of aluminum oxide originated at the defects of specimen surface, where intercrystalline fracture occurred. Particles were removed granularly. Better erosion resistance is obtained for an aluminum oxide with smaller grains. The erosion of silicon carbide originated, again, at the surface defects. Cracklike grooves propagating through pores, however, were observed on the eroded surface and massive particles were removed. The erosion resistance of silicon carbide depends on the density of the pores. An evaluation was also made and compared with metallic materials.

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In this paper, mechanical behavior of stem part of a knee replacement prosthesis in a human femur is analyzed by using experimental and theoretical techniques. In the experiment, the strain distributions on the surface of human femoral model with the knee replacement prosthesis are measured by the strain gauge method. The two-dimensional finite element method is also used to analyze the stress distributions in the human femur. From these results, it is obvious that the stress or strain decreases at the bone part inserted by the stem of knee replacement prosthesis, but concentrates at the outer part of stem. These stress decreases and concentrations depend entirely on the stem size and the material properties of the prosthesis.

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