Though glassfibers in BMC (bulk molding compound) seem to be distributed in all directions, BMC products have anisotropic characteristics in elasticity which are seemingly caused by the nonuniformity of BMC flow in production. This paper represents an analysis and a calculation method of the actual elastic modulus of a FRP (fiber reinforce plastic) shell molded in BMC. The FRP shell is simulated as a laminated flate with thin fiber-reinforced plates which are unidirectional in different directions. The laminate principle and the experience equation of Uemura and Yamawaki are helpful to analyze the elastic modulus of the laminated plate. The probability density of the glassfibers in the microphotograph is counted in every 10 degree direction. Counting a curved glassfiber for two directions and a round glassfiber for all directions, the elastic modulus can be calculated with great accuracy. Using the elastic modulus, natural frequencies and modes of the FRP shell have been calculated by the FEM (finite element method). Good approximations between calculations and experiments have been obtained from the first to the fifth natural frequencies and modes.

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A new concept is proposed, which can reasonably estimate several material characteristic features of newly developed materials at elevated temperatures. The present approach only requires some relatively short-term basic material test data such as on tensile, low cycle fatigue and short-range creep rupture. This concept is essentially based on an analogy to usual materials. Several material behaviors of Mod.9Cr-1Mo (NT) at elevated temperatures can be adequately estimated by applying the present method to the equations of the characteristic features of 2(1/4)Cr-1Mo (NT), which macroscopically shows similar material behavior to those of Mod.9Cr-1Mo (NT). Furthermore, creep-fatigue lives of Mod.9Cr-1Mo (NT) are predicted based on the linear damage fraction rule with in a factor of 3 by using these estimated basic material characteristic equations.

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Abstract-Large quantities of nonmetallic composites such as G10-CR and G11-CR are currently under study as possible materials for magneteic fusion energy structures at low temperatures. Here we study the thermal mechanical response of cracked G10-CR glass/epoxy laminates. The composite material in generalized plane strain is assumed. Fourier transforms are used to reduce the problem to the solution of a pair of dual integral equations. The solution of the dual integral equations is expressed in terms of a Fredholm integral equation of the second kind. Numerical results on the thermal stress intensity factor and the influence of the crack on the mechanical properties at different temperatures are obtained and presented in graph form.

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Phase stresses in alumina and zirconia phases of composite ceramics were measured by using the X-ray diffractions from Al₂O₃ (1. 0. 10) and ZrO₂ (133) by Cr-Ka radiation. Under tension, the phase stress in each phase increased linearly with the applied strain. The stress in Al₂O₃ was larger than that in ZrO₂. The macrostress calculated from phase stresses by the rule of mixture was equal to the applied stress. The residual macrostress was compression on the ground surface. The compressive residual macrostress was larger with increasing the diamond grain size of a cutting wheel. For a given grinding condition, it was larger in the direction perpendicular to the grinding direction than in the parallel direction. The microstress in Al₂O₃ was compression, while that in ZrO₂ was tension. The compressive macrostress zone extended about 10 to 15 μm in depth from the surface for the cases of grinding by #600 and #200 diamond wheels. The broadening of the X-ray diffraction profile was also detected within this zone.

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Bending and fracture toughness tests of superconducting YBaCuO ceramics were carried out at room temperature as well as at low temperature of 80K where superconductivity appeared. The materials of various densities were prepared to investigate the effects of density on strength and fracture toughness. From the test results, it was found that hardness, Young's modulus, Poisson's ratio, bending strength and fracture toughness increased with an increase in density. Bending strength and fracture toughness of the material with a final annealing temperature of 673K were higher than those of the material with a final annealing temperature of 773K. Bending strength and fracture toughness at 80K were higher than those at room temperature. No change in the resistivity of the bend specimen as well as that of the Cheveron-notched fracture toughness specimen was found during deformation at 80K: The superconductivity was not influenced by the deformation and it stood up to fracture.

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Tensile and fracture toughness tests of glass-wisker reinforced polyamide 6.6 with various contents of glass-wisker were carried out to investigate the effect of wisker content on tensile strength and fracture toughness. Tensile strength increased with an increase in wisker content. This behavior can be explained on the basis of the Tsai-Hill hypothesis by considering the length and the orientation of the wiskers. However, at a high content of wisker, the experimental values become lower than the theoretically predicted values due to the stress concentration between wiskers. Although fracture toughness J_IC was reduced once with an increase in wisker content, when the volume fraction of wiskers became higher than 9% the J_IC-value increased with an increase in wisker content. This behavior seems to result from the change of micromechanisms of fracture at a relatively high wisker content, which is due to the interaction of wiskers.

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Composite spring with box cores are proposed by using fiber reinforced plastics. The materials are glass-cloth laminated plastics and carbon-cloth laminated plastics. The structure of the springs consists of core boxes and surface plates which adhere to the upper and lower sides of the core boxes. The dimensions of core boxes are changed in equal ratio according to the distribution of bamboo joints. The stress and strain distributions of the spring under a three-point bending condition are analyzed by using the finite-element method. The analyzed strain distributions are compared with the experimental results. The spring constant is defined by dividing the value of the applied load by spring deflection. The initial failure load of the spring is estimated by applying the strength law of the fiber-reinforced plastics to the stress distribution in the spring. The spring constant per unit mass of composite spring is smaller than that of metal springs with the same configuration. The initial failure load of composite springs increases in comparison with that of the metal springs.

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Cavitation erosion generated in the venturi facility was studied by comparing the erosion loss with the distributions of cavitation bubble collapse pressures (impact loads). The erosion process in the venturi facility is similar to that in a vibratory device although its progress is very slow. That is, the surface first deforms and fractures due to the fatigue by repeated bubble collapse pressures below the critical pressure which impulsively forms a pit. Comparing the distributions of impact load measured using our method with the hypothetical S-N curves of fatigue, Miner's law is realized for the incubation period and the volume loss rate during stable period regardless of the venturi, vibratory and cavitation conditions and materials. Therefore, We found that the estimation of cavitation damage in a flow system is possible uniformly with those in the vibratory method from Miner's law although the distributions of cavitation bubble collapse pressures are markedly different.

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This paper is concerned with a criterion of the low-temperature strength for the metal-FRP bonded joints. The authors have developed a system of thermal stress analysis of the bonded joints. The results of the analysis for AL-CFRP bonded joints show the remarkable stress concentration caused by the different coefficients of thermal expansion. Experiments on the low-temperature strength have been well explained by the criterion "σ_max = σ_f" where σ_max is the maximum von Mises equivalent stress due to external load and thermal stress while σ_f is the fracture stress for the specific temperature. The above criterion also gives the characteristic low-temperature strength for AL-CFRP and AL-GFRP bonded joints between 23°C and -160°C.

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Unskillful design of joints often causes reduction of the bearing capacity of composite structure. Therefore, special attention must be given to the design of the fasteners. A method is presented here which predicts the failure strength and failure mode of mechanically fastened joints in FRP. The stress distribution considering of the effect of the pin is calculated by the use of FEM. The failure load and failure mode are predicted by means of a proposed failure hypothesis together with the point stress criterion. The value of the characteristic length is determined from the tensile test with a hole and the "bearing failure test". The results of this method are found to agree well with the experimental results.

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Supersaturated solid-solution alloys of the Al-Ti system were prepared at a pressure of 5.4 GPa and a temperature of 800°C for 10 hours. The solid solubility was determined to be about 1.5 at%Ti by the X-ray diffraction technique. Changes of material properties (lattice parameter, elastic constants, density) for obtained solid solutions as a function of Ti concentration were estimated. The solid solubility of Ti in Al was increased to 1.5 at%Ti by the effect of the high pressure of 5.4 GPa. The lattice strain ε₀ was measured to be -0.088. The shear modulus of the solid solutions was increased with increasing Ti concentration. The rate of 125 GPa/(e/a) was obtained. This feature was different from those of solid solutions consisting of simple metal alloys.

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The tensile test results show that the joint brazed by the Ni-Cr-B alloy has the highest strength among the other alloys tested. The effect of the brazing clearance, the surface roughness and the base metal are described. Failure of the brazed joint occurred at the midplane of its brazing layer in all cases tested. The EPMA has characterized the composition in the brazing layer. A massive distribution of the element Ni found in the central portion of the brazing layer relates to the failure mode.

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A new analytical method has been proposed to evaluate static fatigue and cyclic fatigue strength after proof testing. Based on this method, the effectiveness of a proof test with loading pattern different from that in a service condition can be evaluated for multiaxially stressed ceramic components. A method for determining the slow crack growth parameters by fatigue data after proof testing has been also proposed. These methods have been verified by comparing estimated results with cyclic fatigue test results after proof testing.

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Voids formed around the tip of a stably growing crack in SM50A steel were observed in every 10 μm thickness of the specimen through an optical microscope. The results showed that the shape of voids was disklike, the thickness of which was in the direction of the specimen thickness. The void dimensions increased with the J-integral level, maintaining a similar configuration. The density of void distribution ahead of the stable crack became higher as the J-integral level increased, but it was so low that coalescence of the voids and the crack resulted in a zigzag crack front.

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Subcritical-crack growth rates for carbon steels in high-temperature pure water are obtained from fatigue and constant load tests. The test specimens, made of STS 42 and 49 carbon steel pipes are CT type and surface-cracked flat plate-type. The experimental environment is saturated pure water at 288°C and 7.8 MPa pressure. The subcritical-crack growth rates are influenced by several factors; the fatigue crack growth rate, da/dN in water is accelerated by low frequency and high stress ratio. The da/dN in water from a trapezoial load wave and for welded metal is less than from a triangular wave and for base metal. In addition, the da/dN in water at 150°C and in a steam environment is lower than in water at 288°C. The growth rate, da/dN, in the thickness and the width directions is almost equivalent to the results of the surface-cracked flat plate specimens. The curve of the crack growth rate, da/dt, is obtained from the constant load test. The threshold value of the stress intensity factor for stress corrosion cracking for STS base and welded metal of carbon steels is relatively large when compared with the sensitized Type 304 stainless steel and other carbon steels.

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The fatigue crack propagation characteristics at stage 2 in spheroidal graphite cast iron with various dual phase matrix microstructures have been investigated. Fatigue tests were carried out at stress ratio R = 0.1 and 0.8, using the CT specimen. The main results obtained were as follows; (1) In the low-ΔK region at R = 0.1, the fatigue crack propagation resistance in as-cast material with dual phase matrix microstructure consisting of ferrite and pearlite was superior to those of heattreated materials whose matrix microstructures were changed into single phases of ferrite or pearlite. (2) In the whole ΔK region at R = 0.1 and the high-ΔK region at R = 0.8, it was possible to improve the fatigue crack propagation resistance by changing only the pearlitic phase in the matrix microstructure of as-cast materials into sorbitic or bainitic phases, utilizing the intercritical treatment.

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Vickers hardness, four-point bending tests and fracture toughness evaluation by means of two kinds of indentation methods (ISB and IF methods) were conducted on normal-sintered silicon carbide (SiC). To investigate the microstructure on the hardness, H_V, the bending strength, σ_f, and the fracture toughness, K_IC, three kinds of SiC materials (materials A, B and C) with different sintering temperatures were prepared. Material A, of lowest sintering temperature, had the smallest grain, lower density and higher porosity. On the other hand, material C, of highest sintering temperature, had abnormal grown grains, higher density and a lower porosity which were equal to material B. The H_V decreased with increasing indentation load, P, for all three materials. The indentation shapes were comparatively clear, and on the fracture surface of materials A and B, four cracks initiated from the four vertices of the indentation as clear radial and median cracks. For material C, a part of the surface peeled off due to the effect of lateral cracks on the surface layer, and the fracture surface was not flat. The σ_f decreased with increasing P for all three materials. The σ_f of material C was smaller than those of the other materials for the smooth specimens, and the variation of the σ_f of material C was larger than the other materials for the smooth and precracked specimens in all cases. The K_IC determined by the ISB method was smaller than that by the IF method in the same P condition, and the K_IC by the IF method decreased with increasing P and was saturated in the range of P ≥ 10 N.

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In order to investigate variations of spatial distributions of cracks observed on the unnotched specimen surface during the fatigue process, plane bending fatigue tests were performed on carbon steel JIS, SS 41 in laboratory air and a sodium chloride aqueous solution. Two methods, developed by Morishita and Ono in the field of mathematical ecology, were used in analyzing the spatial distributions of Cracks. The following results were obtained. The spatial distributions of cracks are influenced by both stress amplitude and stress cycling. In the high stress amplitude region, the distributions are nearly random, while in the low stress amplitude region, the distributions have clumps indicating nonrandom distribution. This result was common to both fatigue in air and corrosion fatigue. With increasing stress cycling, the spatial distributions of cracks approach random distributions in the high stress amplitude region, while in the low stress amplitude region, the distributions show a strong tendency to have two kinds of clumps whose sizes are 1/4 mm² and 8 mm².

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Tensile tests and rotating bending-fatigue tests were carried out on plain specimens of ferrite-martensite dual-phase steel and ferrite-martensite-spheroidal graphite triphase steel in order to investigate the influence of graphite on the tensile and fatigue strengths of the triphase steel. Both steels have nearly equal microstructure parameters, except for the graphite content. The graphite in the triphase steel barely influences the tensile strength, but lowers the fracture ductility. On the other hand, both fatigue crack initiation and propagation lives decrease with the existence of graphite.

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Fatigue strengths of ceramic-coated steel at room and elevated (773K) temperatures were almost identical. Although, at room temperature, fatigue strength of substrate steel was higher than that of ceramic-coated steel, at elevated temperature, fatigue strength of ceramic-coated steel was higher than that of substrate steel. Fatigue-fracture processes of ceramic-coated steel were as follows. At a significantly early stage of fatigue, a fatigue crack is initiated at the surface of the ceramic layer and propagates quickly to the metal layer. The propagating fatigue crack continues to grow into the substrate; there is no initiation of another fatigue crack at the interface between ceramic and metal layers. Fatigue strength of the specimen with a thick ceramic-coating layer was higher than that with a thin ceramic layer. This result will be understood, considering that the thickness of the ceramic layer corresponds to an initial defect size.

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Soda-lime glass specimens with an indented induced flaw at the center, were fractured under a constant load applied by the four-point bending of the plates, concentric-ring loading of disks, and diametral compression of disks. Then, after indentation, the specimens were quenched in oil to remove the residual tensile stress near the crack tip. The time taken until failure increased with decreasing applied stress, and the degree of the increase was significantly higher in the diametral compression than in other stressing modes. This result was completely contrary to our previous report where a vacuum annealing treatment had been employed to remove residual stress. Further, the scatter in the fatigue data for equibiaxial tension was obviously less than that in the previous report. The subcritical crack-growth parameters, n, determined from a straight line on a logarithmic plot of the fatigue life time as a function of the applied stress were 15.2 for diametral compression, 9.7 for equibiaxial tension, and 9.1 for uniaxial tension. The higher value of n in diametral compression can be attributed to the fact that the crack growth was restricted by the higher hydrostatic compressive stress.

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The influential factors on the fatigue behavior of the solid electrolyte β"-alumina are measured. The static fatigue life depends markedly on the environment. It appears in air at room temperature, where the water vapor in the air apparently affects β"-alumina, but does not appear at elevated temperatures or in a vacuum. Furthermore, the cyclic fatigue lifetime does not depend on the number of cycles but only on the loading time. Fractographic observations suggest that the lifetime is mainly dominated by the crack growth behavior in the large platelike crystals.

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A laser interferometric strain/displacement gage (ISDG) was developed and used to investigate the fatigue crack growth at elevated temperatures. The technique was modified so as to enable continuous measurement of crack closure during the fatigue crack growth tests. Only the numbers of interference fringes were used instead of the movement of those fringes as an input information in the present system developed in this study in order to calculate the crack opening displacement. The fatigue crack growth tests were performed in SUS304 stainless steel compact tension specimens at several temperatures up to 500°C. Crack closure monitoring was successful for all the tests in this study. A discussion was included on the influence of compressive stressing on the fatigue crack growth rate and closure.

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A series of fatigue and creep-fatigue tests were conducted with 304 stainless steel at 550°C under a variety of biaxial strain conditions. Fatigue life under nonproportional loading conditions showed a significant life reduction compared with that of proportional loading, and this life reduction was reasonably estimated by taking into account the strain paths along which the strain history is imposed. Furthermore, a marked life reduction was shown to occur under nonproportional loading by imposing a strain hold period at a peak tensile strain. This life reduction was evaluated by the linear damage rule. It was shown to be possible to estimate the fatigue damage and the creep damage under nonproportional loading by a linear damage rule by estimating a stress relaxation behavior by Mises-type equivalent stress or Huddleston-type equivalent stress.

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The influence of residual stress on the fatigue crack growth behavior of HT 80 steel weldments under two-step block loadings was evaluated by utilizing linear elastic fracture mechanics. The crack growth rates of the welds were dominated by residual stress rather than the block size or the load sequence. The crack opening stress intensity factor, K_op, in the welds subjected to two-step loading was found to be almost the same in each block and was governed by the maximum stress intensity factor in the block. The crack growth rates of the welds with residual stress under two-step block loading were correlated with the effective stress intensity factor range, ΔK_Rem, estimated based on linear accumulation of the stress intensity factor range which is defined as K_irmax - K_op, where K_irmax is the maximum stress intensity factor which takes into account the residual stress at each step in a block.

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Rotating bending fatigue tests were conducted on smooth specimens of pure titanium in order to investigate the growth behaviour of small cracks and their statistical properties. Small cracks grow much faster than large cracks when subjected to the same nominal stress intensity. The former also grow below the threshold values of ΔK_th and ΔK_{eff, th} for large cracks. The early growth of small cracks is markedly affected by the microstructure in the region of crack length below 450 μm, and the growth rates often decrease at grain boundaries and due to crack deflection (a microstructurally small crack). Almost all of Stage I facet depths observed are of grain size, thus Stage I cracks do not correspond to microstructurally small cracks. This is clearly different from the results obtained in steels and aluminum alloys. The growth rates of small cracks follow a log-normal distribution, independent of maximum stress intensity or crack size. The coefficient of variation decreases with increasing the maximum stress intensity and then reaches a constant value. The largest scatter of the growth rates is obtained when the crack depth is comparable to grain size, thus it is attributed to grain boundary and grain orientation.

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To clarify the through fatigue crack propagation behaviour in and around the heavily changed cross-sectioned area, crack propagation rate and the crack closure were measured for the CT specimens possessing blined holes or side grooves. The results were investigated using a stress intensity factor (SIF) calculated by the three-dimensional finite element method (3D-FEM). The main conclusions are as follows: (1) under the same SIF calculated by the 3D-FEM, the crack situated in the blind hole propagates slower than that in the plane specimen; on the other hand, the crack situated before the blind hole propagates faster: (2) the reduction of the crack propagation rate in the blind hole is based on the crack closure induced by the sudden change of the cross section.

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Large deformation finite element analyses based on Gurson's yield function are carried out for single-edge cracked specimens subjected to bending moment and shearing force, and the stress/strain field around a crack tip under the conditions of large scale yielding and mixed mode loading is examined. The crack tip under mixed mode loading is surrounded by a stress/strain field with HRR singularity, which is uniquely represented by J-integral J, J_I and J_II (J_I: mode I component, J_II: mode II component), throughout small scale yielding and large scale yielding. The fracture process zone of the crack tip is discussed based on the distributions of equivalent plastic strain ε_p and void volume fraction f. The size of the fracture process zone due to ε_p becomes larger, if the mode II component is more predominant. On the other hand, the size of the fracture process zone due to f becomes larger, if the mode I component is more predominant. The implications of this study on the behavior of ductile crack initiation from a mixed mode crack are also discussed.

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Microstructural randomness of materials causes the fluctuation of initiation lives and growth rates of small cracks during high-temperature creep and creep-fatigue. The crack initiation life is especially strongly dependent on the grain-boundary inclination to the stress axis. Taking into account the effect of random grain-boundary inclination, the basic probabilities of initiation are analyzed by a convolution integral method on the basis of the three-dimensional stochastic model. Any probability of crack inclination and initiation life can be calculated from the basic probabilities. Excellent coincidence is obtained from the comparison between the analyses and experimental data of Type 304 stainless seeel under the creep-fatigue condition.

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In order to clarify the effect of the compressive strain rate on initiation and growth of small cracks under creep-fatigue condition, the following tests were conducted using smooth specimens of Type 304 stainless steel at 650°C in air, (i) slow-tension and fast-compression (c-p type fatigue), (ii) slow-tension and slow-compression (c-c type fatigue), and (iii) slow-tension and very-slow-compression (c-s type fatigue). The results obtained are summarized as follows. (1) Multiple small cracks initiated and grew at random along grain boundaries being nearly perpendicular to the stress axis at each specimen surface. (2) The compression-going strain rate affected the crack initiation life and the crack density. The c-p type fatigue brought about the shortest initiation life and the highest crack density, and the c-s type fatigue did the longest and the lowest. (3) The crack growth rate was not influenced by the compression-going strain rate but was primarily governed by the tension-going strain rate. (4) The difference of life between c-p type and c-s type fatigue was caused by the difference of crack initiation life and crack coalescence. The highest crack density in the c-p type fatigue made the crack coalesce easily to bring about a long crack.

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The tensile fracture behavior of the center notched plates has been studied for composite materials. Tension tests of the center notched plates for glass fiber reinforced polycarbonate have been carried out for a wide range of notch radii and two kinds of width. The fracture process at the notch tip was carefully observed during the tensile testing. Experimental results were discussed in terms of the linear notch mechanics, which considers the combination of the elastic maximum stress at the notch tip and the notch tip radius. The results obtained can be summarized as follows; (1) In the case of notched GFRP, the failure occurred in a brittle manner which was controlled by the constant elastic maximum stress which was governed by the notch tip radius only. (2) The strength characteristics and the fracture were clearly estimated using the parameter, σ_maxc/E, regardless of the content of glass fiber. (3) For polycarbonate, the failure was in a ductile manner, which was controlled by the nominal stress in the net section of each type of specimen.

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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 technique 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 experimental ones.

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This paper presents a new scheme for the estimation of unstable ductile fracture of a reactor pressure vessel under thermal shock conditions. First, it is shown that the bending moment applied to the cracked section can be evaluated by considering the plastic deformation of the cracked section and the thermal deformation of the shell. As the contribution of the local thermal stress to the J-value is negligible, the J-value under thermal shock can be easily evaluated by using fully plastic solutions for the cracked part. Next, the phenomena of ductile fracture under thermal shock are expressed on the load-versus-displacement diagram which enables us to grasp the transient phenomena visually. In addition, several parametrical surveys are performed on the above diagram concerning the variation of (1) thermal shock conditions, (2) initial crack length, and (3) J-resistance curve (i.e. embrittlement by neutron irradiation).

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In this study, surface damages of type 304 stainless steel, one of the candidates for the first wall structural material in a fusion reactor, at plasma disruption loading are simulated by a high heat flux NBI. Influences of the surface damage on the fracture strength and the residual life are studied. The results obtained are summarized as follows: (1) The present surface damages give a qualitatively good simulation at plasma disruption loading. (2) The fracture strength of the damaged material is improved by the existence of a melting layer which has a higher hardness. There is no effect of microcracks in the melting layer on the fracture strength and the plastic collapse criterion can stand. (3) The fatigue strength of the damaged material is reduced considerably due to the existence of the microcracks in the melting layer. (4) Numerical simulations of fatigue crack growth are successfully attempted. It is shown that the residual life can be predicted quantitatively by the present method.

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Piping systems for power plants are designed to withstand hypothetical events such as leakage from a crack and jet impingement. The assumed event, in this paper, is that high-pressure water leaks from circumferential through-wall cracks in a carbon steel pipe. Sizes of the cracks detected by leak monitors under normal operations are calculated from the analyses of fracture mechanics and fluid mechanics. Crack-opening areas for jet force assessment are obtained for various diameter pipes under abnormal conditions. The areas are compared with the 0.1F (10% of pipe cross section) criterion. Large diameter pipes are shown to have large safety margins against fracture from the viewpoint of leak monitors and jet force assessment.

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In a previous paper, we presented a new adhesive-strength evaluation method, which uses two stress-singularity parameters. In this paper, this new adhesive-strength evaluation method is applied to single-lap joints which are generally used as adhesive-strength test specimens. By this strength evaluation method the relationships between adhesive-strength and lap length, thickness of adhesive layer, thickness of adherend, and adhesive edge angle are analyzed. These analytical results coincide well with the results based on maximum stresses in adhesive layers.

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A frictionless, axisymmetric contact problem is considered, where an elastic half-space is pressed onto a rigid foundation with a sphefical-ended protrusion and the contact area between the 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 equations 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 relavant numerical results available.

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One-dimensional, generalized thermoelasticity is presented based on Lord and Shulman's theory and Green and Lindsay's theory. The former theory involves one relaxation time of the thermoelastic process and the latter involves two relaxation times. These theories have been developed in an attempt to eliminate the paradox of an infinite velocity of thermoelastic propagation inherent in the classical dynamically coupled theory. A formulation of generalized thermoelasticity which combines both generalized theories is derived. The generalized thermoelastic problems in an infinite solid cylinder are analyzed by means of the Laplace transform technique. The numerical calculations for displacement, temperature and stress under the generalized formulation are carried out and compared with the results under the classical one.

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An elastic-plastic finite strain/finite-element analysis was performed on a crack on a bimaterial interface to provide insight as to initiation of ductile fracture. The materials lying above and below the interface are taken to be different from each other in yield stress or in strain hardening exponent. Gurson's constitutive equation was employed in order to take account of the effect of void nucleation and growth on the near crack tip fields. The results are as follows: (1) There exists a singular field akin to the HRR field, and the j-integral can be an effective fracture mechanics parameter for an interfacial crack. (2) The microvoids give a larger effects on the stress and strain fields in the immediate vicinity of the crack tip than for a homogeneous material. (3) The plastic strain and microvoid volume fraction localize in a narrow band which grows into the softer material from the intersection of the interface and the periphery of the blunted crack tip at an inclination of about 15-45 degrees.

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The fringe order gives important information on the nonlinear mechanical properties of a transparent polymer. However, the effect of viscosity on the fringe order has not been investigated sufficiently. In this paper, the time-dependent photomechanical properties of cellulose acetate was examined by means of the creep recovery test after removal of stress. As a result, both creep strain and creep fringe order of cellulose acetate can be divided into time-dependent recoverable viscoelastic and time-dependent nonrecoverable viscous. Viscoelastic strain and viscoelastic fringe order are described by the power law of duration of recovery, and constants of these equations are determined only by the ratio of stress to the yield stress at the temperature. The relation between viscoelastic strain and viscoelastic fringe order, as well as between viscous strain and viscous fringe order is equivalent to that between plastic strain and plastic fringe order, which do not depend on stress and creep time.

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This paper deals with the stress concentration analyses of fillets in an infinitely long strip with symmetric rectangular notches or protuberances under tensile load or in-plane bending moment. The stress field induced by a point force in a semi-infinite plate is used as a fundamental solution to solve those problems. The stress concentration factors are systematically calculated under various geometrical conditions. Through the comparison of the present results with the previous research works, it is found that the Peterson's stress concentration charts based on photoelastic tests gives underestimated stress concentration factors by about 10 %. The stress concentration factors of a stepped flat bar with fillets are found to be almost determined by the results of shoulder fillets in a semi-infinite plate.

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This paper describes new methods to obtain development isochromatics of the stress distribution in a thin-walled cylinder. The commom photoelastic method cannot be applied to a cylinder, because the light does not pass at a right angle through the wall. So two methods were performed. One was to take isochromatics of the wall by turning the cylinder with a slit. The other was to obtain the isochromatics by putting the line light source at the axis of the cylinder and wrapping a photograph sheet around the cylinder. Using these methods, we determined the stress distributions in the thin-walled cylinder with a side hole, under torsion.

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To develop a nonisothermal constitutive model of plasticity, we postulate a similarity equation which specifies the positional change of a kinematic hardening variable relative to the bounding surface under temperature variation. It results in a temperature-change induced term in the evolution equation of the kinematic hardening variable. On the assumption that the kinematic hardening variable consists of components, the proposed model is transformed to an equivalent form based on nesting multisurfaces. Discussing the condition for the temperature-history independence of plastic stress response, which is observed rather often in experiments, we derive analytical expressions of stress vs. strain relations under monotonic and cyclic thermomechanical loading. Relations between the present and previous models are also discussed.

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This paper is concerned with a compression experiment in the case of eccentric at upper and axial at lower ends on carbon steel thin-walled square pipes with various a/c ratios in the short column range, supported with spherical seats. An empirical formula for calculating eccentric compressive buckling stress "σ_ce*" of the carbon steel thin-walled square pipes is presented as follows: σ_ce*/σ_cr=1/(e/c) where σ_cr=axial compressive buckling stress, e=upper eccentricity, c=mean distans between wall, a=length. The measurement reveals that the results calculated by this equation are in good agreement with those obtained experimentally for the short column lange.

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This papel considers the possibility of identifying unknown applied loads when a structure has an optimal shape for the loads. First, a shape optimization problem is solved for given forces by the inverse-variational-shape-determination method. The optimality in the method is the uniformity of the strain energy densities calculated on the surface for assumed loads. The true loads are determined by minimizing the variance of the strain energy densities from several points on the surface with respect to unknown load parameters.

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