Circumferentially grooved specimens were low cycle fatigued, and the local stress-strain relation was calculated at the notch root by FEM. The fatigue lives for crack initiation and final failure were satisfactorily evaluated by both the axial and equivalent plastic strain ranges produced at the notch root, and the Coffin-Manson law held for the notched specimen as well as for the smoothed specimen. The growth behavior of short surface crack at the notch root was examined in association with growth rates of the short surface crack in the smoothed specimen and of the long through-crack. The fatigue crack growth rates, da/dN, were successfully plotted against the cyclic J-integral range, ΔJ, and the strain intensity factor range ΔK_ε. The log da/dN vs. log ΔJ plots in the notched specimens were situated between those for the small surface crack in the smoothed specimen and for the long through-crack in the lower crack growth rate region, where the differences between each two were quite small to be allowable in a pratical sense, while these three da/dN vs. ΔJ relatives were nearly in accord with one another in the higher crack growth rate region.

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The growth behaviour of microstructurally small fatigue cracks has been investigated with smooth specimens of a ferritic-pearlitic steel, S45C, under rotating bending. The effects of microstructure, particularly the roles of pearlite structure, on crack growth were evaluated based on detailed microscopic observations. In regions smaller than a certain crack length, cracks tended on grow preferentially in ferrite structure, and crack growth rates decreased markedly at ferritepearlite boundaries when cracks grew into pearlite structure from ferrite structure. The above region of crack length, i.e. the length of a microstructurally small crack, depended on stress level and increased with decreasing stress level. The growth mechanism is also discussed in terms of the results of fractography.

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The present authors proposed two schemes for predicting the fatigue lives of cracks propagating in residual stress fields using initial residual stress distribution. To make applications of the schemes possible for cases where residual stresses redistributed due to crack initiation and propagation are given, this paper presents a method for determining initial residual stress fields form redistributed residual stresses measured at several points. Determination of the initial residual stress distribution was effectively achieved by introducing fundamental residual stress distribution functions which satisfied physical requirements for the residual stress. The least residual criterion was used in the determination. A sensitivity matrix was proposed to evaluate the effect of errors involved in the measurements and to select the best combination of measuring points. Numerical simulations of the determination on initial residual stress fields and the prediction of fatigue crack propagation lives showed the usefulness of the proposed method.

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Center-cracked specimens of JIS S35C and SUS 304 steels were low-cycle fatigued under test conditions accompanies by ratchet deformation, and crack opening displacement, crack closure and crack growth were examined. Then, crack growth rates were analyzed in terms of elastic-plastic fracture mechanics parameters. The effect of ratchet deformation on crack growth rate appeared in the log da/dN vs. log ΔJ plot in the way of accelerating crack growth rate, where da/dN is crack growth rate and ΔJ is cyclic J-integral range. Such an acceleration of crack growth rate occurred under test conditions satisfying both of σ^max_net>σ_y and U = 1.0, where σ^max_net, σ_y and U are maximum net cross-section stress, static yield stress and crack opening load range ratio, respectively. The parameter of ΔJ(1-Φ^min_t/Φ^max_t)⁰.3 was proposed for evaluating the crack growth rate on a ΔJ basis, where the minimum and maximum values of crack tip opening displacement were denoted by Φ^min_t and Φ^max_t. The da/dN plotted against this parameter forms a straight line independent of ratchet deformation on double logarithmic controlling the croak growth rate under test condition including ratchet deformation.

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Transverse fatigue crack tests were conducted on unidirectionally continuous fiber reinforced metal SiC_CVD/6061 Al over a wide range of fatigue crack growth rates covering the threshold stress intensity factor range Δk_th below which cracks remain dormant or grow at experimentally undetectable rates. The fatigue crack growth mechanism was proposed on the basis of fractographic examinations. It is shown that the transverse fatigue crack growth characteristics were successfully evaluated from the matrix metal.

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The fatigue crack propagation in physiological salt water was investigated in polycarbonte and glass fiber reinforced polycarbonte. The effects of physiological salt water, glass fiber content and stress ratio on fatigue crack growth rate were determined. These effects in physiological salt water could be considered by dividing the crack growth rate curve into two regions ; I and II. The crack growth rate in region I was accelerated by the physiological salt water and stress ratio. In region II, the crack growth rate increased rapidly with increasing ΔK. This transition behavior may result from the physiological salt water penetrating the fatigue crack, which demeans itself like a viscous fluid against a viscous elastic crack, and divides the crack growth rate curve into two regions. The physiological salt water markedly influenced the fracture morphology at a low ΔK level. The fatigue crack propagation behavior in the physiological salt water resulted from a variation of fracture morphology with increasing ΔK.

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In order to examine the effect of microstructure on the static tensile properties of a spheroidal graphite (SG) cast iron, eight kinds of materials with the same chemical composition and with a systematically varied microstructure were prepared. After tensile test, Young's modulus E, and the ultimate tensile strength σ_B and elongation φ of each material wee characterized using several microstructural parameters such as the area fraction of pearlite f_P, density ρ and SG state related parameters (area fraction, particle number, sheroidized ratio). The results obtained are summarized as follows : (1) The relationship between E and an applied stress σ showed a trend which supports the presence of load transmissibility of SG. (2) The base microstructure and SG induced changes of E, σ_B and φ which were well characterized by the parameter f_P or ρ. For materials with a higher f_P, the tensile properties were primarily dominated by pearlite, and SG had less effect. (3) In the ferrite-base material, SG affected the values of σ_B and φ. Those effects were evaluated by parameters relevant to the SG state.

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Ferrite-base and pearlite-base spheroidal graphite cast irons were prepared to examine corrosion fatigue resistance in 3% hydrochloric acid and synthetic seawater. Rotating bending corrosion fatigue tests were conducted at two rates 3400 rpm and 260 rpm. From the tests in air and two corrosive environments, the following results were obtained : (1) The pearlite-base material (F) showed a fatigue strength stronger than that of the ferrite-base material (A) in the intermediate-cycle fatigue range, irrespective of environment or rotating speed. In the high-cycle fatigue range, the fatigue strengths of both materials asymptotically approached to coincide. (2) Anodic dissolution of graphite and local cathodic dissolution of cementite in pearlite played a primary role in the high-cycle corrosion fatigue process. (3) Those dissolutions described above induced a fatigue process different from that in air and resulted in diminished scatter of the S-n curves.

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The effects of specimen size and preload history on the fatigue crack growth behavior of welded joints were examined in connection with residual stresses. As a crack propagates from a tensile residual stress field, the crack growth rate is insensitive to specimen size, because the crack tip always opens due to residual stress. As a crack propagates from a compressive residual stress field, however, the crack growth rate decreases with increasing spcimen size. Preload history is found to have a reduction effect on residual stresses. The crack growth rate of the welded specimens which were preloaded above 70% of their yield stress shows a tendency to approach the crack growth rate of the base metal. The crack growth rate in the welded joints is correlated with ΔK_effR which takes into account the residual stresses and stress ratio effect of the bese metal.

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In a nominal or engineering stress-controlled low-cycle fatigue test, cyclic strain-induced creep (C.C) often advances when a mean stress is imposed. To examine rigorously the effect of this C.C behaviour on fatigue strength, true stress-controlled low-cycle fatigue tests were conducted on a medium carbon steel under imposed either tensile or compressive mean stress. The effects of a cyclic stress-strain relationship and C.C behaviour-produced axial plastic strain (ε_m) on fatigue strength were examined. The following results were also examined from the viewpoint of microcrack initiation and propagation. The following results were obtained : (1) the cyclic plastic strain versus stress amplitude relation at the steady cyclic stress-strain state showed a power type relationship, irrespective of tensile or compressive mean stress. (2) An increase of ε_m per cycle at half of the fatigue life was expressed by a power law of maximum tensile or compressive stress. (3) A modified Manson-Coffin relation, inclusive of a parameter of mean stress, was proposed. (4) The effect of the C.C behaviour on the fatigue strength was estimated on the basis of a microcrack growth law-aided approach previously developed.

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Cracking behavior under multiaxial fatigue has been observed to be affected by not only stress multiaxiality but also metallurgical microstructure. In copper which was used in this study, cracks were observed to be nucleated and to grow along grain boundaries. It was also found that the crack growth was assisted by coalescence among initiated cracks. These observations suggest that the direction of the main crack might be determined by the distribution of grain-boundary cracks. A modeling of grain-boundary cracking is required to establish the way to predict the direction of the main crack, depending on stress multiaxiality. In this analysis, two components of shear deformations on the grain-boundary plane were taken into account to describe incompatibility along the grain boundary. New parameters based on two shear deformations were proposed to represent the orientational distribution of grain-boundary crack. Calculated results were composed with experimental crack distribution during biaxial fatigue tests with constant and variable strain-biaxialities.

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Through fatigue crack propagation behavior near blind holes in the CT specimens of carbon steel were investigated using stress intensity factors calculated by the three-dimensional FEM. The results are as follows. The crack propagation rates for blind-holed specimens differ from those of non-blind-holed ones because of thee following reasons. (1) The contours of the crack situated just in front of the blind hole differ from those of anon-holed specimen. (2) The effective stress intensity factor for the through crack which was located in the blind hole differs from that for the non-holed specimen even if the stress intensity factors for both cases are the same. Therefore, the through fatigue crack propagation behavior around the blind hole could not be estimated based on that of a on-blind-holed specimen.

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The effective Poisson's ratio of laminated fibrous composites shows a peculiar behavior as it becomes larger than unity or less than zero. This behavior can be utilized in the design of composite structures with special functions. The lamination theory, non-linear programming technique and a heuristic approach are used to find the lay-ups of the laminates with the maximum, zero and the minimum values of Poisson's ratio of general symmetric laminates. It is found that balanced angle-ply symmetric laminates yield the maximum value and unbalanced bi-directional symmetric laminates yield the minimum value. Experimental results shows a good agreement with the analytical results.

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Semi-infinite bodies with a drill-hole shaped pit under uni-axial tension were analyzed by the body force method. In the analysis, special fundamental solutions wee used in order to obtain the high accuracy by numerical results even in the case of small number or divisions.

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A solution is given for the frictionless indentation of a transversely isotropic layer by an annular rigid punch, where the elastic layer is resting on a rigid foundation. The problem is reduced to an infinite system of simultaneous equations using the method of expressing the normal stress under the punch as appropriate series. The effect of transverse isotropy and indentational load on the stress field are studied. Results are compared with numerical solutions for the corresponding isotropic problem.

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The generalization of the classical rate-independent elastoplasic constitutive law to account for large deformation and geometry change is attemped. In the present paper, attention is focused on a new decomposition of the stretching tensor D and the spin tentor W into the elastic and plastic parts using polar decomposition of the deformation gradient tensor F given by Lee. Proposed decomposition of the stretching tensor D satisfies both conditions of summability and objectivity. The general framework of constitutive modeling of elastoplasticity is derived from the simple material of rational framework of constitutive modeling of elastoplasticity is derived from the simple material of rational mechanics. The datailed formulations of stress-strain relation for Prager's kinematic hardening law are described, and several tensors related to deformations are also presented in terms of displacements to be applicable for computational mechanics.

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In the previous paper, the theoretical results of the acousto-elastic effects caused by plastic anisotropy growth were presented. The objective of the work reported in this paper is to present a numerical example of the correlation between the acousto-elastic effects and plastic anisotropy growth. Numerical calculations have been made for a uniaxial tension test of an aluminum by using the third-order elastic constants measured by Crecraft and the anisotropy parameter and a Bauschinger modulus of cold rolled aluminum reported by Svensson. By comparison of both simulation models based on the flow theory and the corner theory with previously reported experimental observations, it is suggested that plastic anisotropy is closely related to the acousto-elastic effects through the vertex-like yield effects of the corner theory.

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The elastodynamic response of a single-edge crack in a semi-infinite orthotropic medium is considered in this study. The crack is oriented in a direction normal to the edge of the half-plane. 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 in then expressed in terms of a Fredholm integral equation of the second kind. Numerical values on the dynamic stress intensity factor for some fiber-reinforced composite materials are obtained and the results are graphed to display the influence of the material orthotropy.

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An analytical solution is presented for a plane thermal stress problem in a nonhomogeneous hollow circular plate subjected to an asymmetric heating as an example of nonhomogeneous multiply-connected regions. The nonhomogeneous plate has the Yong's modulus and thermal conductivity expressed in forms of different power laws of radial co-ordinate, the coefficient of linear thermal expansion given as an arbitrary function of radial co-ordinate and the constant Poisson's ratio. The governing equation of the thermoelastic problem in the nonhomogeneous plate formulated in terms of stress function becomes Euler's differential equation. The problem considered in this paper is restricted to symmetric thermal stress problem with respect to χ and y axes. The single-valuedness of rotation is assumed based on the Michell's condition derived for arbitrary nonhomogeneous body in the previous report by present author. Numerical calculations are carried out for the case of a nonhomogeneous hollow circular plate subjected to an asymmetric heating on the inner boundary surface.

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Two-dimensional impulsive stresses are analyzed by the boundary element method with the Laplace transformation and the numerical inverse transformation using the fast Fourier transformation. The condition of the stability between the length of the element and the time step is given by the analysis. The validity of the condition is confirmed by the numerical results. Under the consideration of this condition, the dynamic stress concentration factors of the circular hole, the elliptic hole and the elliptic notch in a strip are obtained from the surface forces and the tangential derivatives of surface displacements. It is shown that the dynamic stress concentrations are approximately ten percent larger than the static ones.

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A method for determining the planar elastic anisotropy of rolled sheets, which is based on the resonance method using multiple vibrational modes, is proposed in this paper. This method was demonstrated with pure-titanium rolled sheets, and elastic anisotropy in the rolling plane was measured. The results agree well with elastic constants determined by the single longitudinal resonance method for each direction and are supported qualitatively by X-ray pole figures. In addition, this method was also applied to study deep-drawn titanium sheets and it was shown that elastic anisotropy changed after the deformation.

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To characterize the work hardening and softening in plastic deformation, we proposed the scalar parameter which is the integrated value of inner products of incremental plastic strain vectors along the strain path. This parameter was elaborated by the experimental data of the tensile stress-strain curve and the uni-axial cyclic curves of SUS 304 stainless steel. Bi-axial stress-strain relations and bi-axial cyclic plastic deformation were calculated with the constitutive equation including this parameter. The work hardening and softening phenomena were simulated for the bi-axial monotonic and cyclic plastic behavior.

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The quasi-static loading on a curved strip compressed by a flat, rigid plate is considered with particular reference to large deformations, the ensuing buckling behavior and the effect of the supported end condition on the snap-through. The deformation characteristics have been analyzed using an incremental finite element technique. Particular attention has been paid to modelling the situation when a node contacts the plate, and to the condition for separation of the strip from the plate. It was found that he normalized force of the clamped ends of the shell was larger than that of the pinned ends at snapping point and that the amount of plate displacement and the distance of the clamped edges of the shell between the contact point and the central point were smaller than those of the pinned edges at snapping point.

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This paper is concerned with an integral equation approach to inverse problems in elastodynamics. The inverse problem under consideration is defined such that the shape of an internal flaw in a structural component is not known a priori, although the eigen frequencies can be measured. The well known integral equations for elastodynamic problems are expanded into a Taylor series. Then, the boundary integral equations are derived for modification of the assumed flaw shape. The boundary element method is applied to the numerical implementation of the resulting boundary integral equations. A new computer program is developed for two-dimensional problems. The usefulness of the proposed method is demonstrated through numerical computation for a few sample problems.

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The method of caustics (shadow spot method) has proven to be a powerful optical method to measure stress intensity factors in static and dynamic fracture mechanics problems. In this paper, a theory of caustics was developed for elastodynamically propagating cracks under inplane mixed-mode conditions. Complex potentials for the general solutions of a near-tip field which have been previously derived by the authors were used in this theoretical development. The effects of crack velocity and the mixed-mode condition on the caustic pattern and intial curve were investigated. A new procedure was also proposed for the evaluation of the dynamic stress intensity factors K_I and K_II using appropriate dimensions of the caustic pattern. The method of caustics developed here enables one to study quantitatively various mixed-mode dynamic fracture phenomena such as crack branching, crack curving, and crack kinking.

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The elastic/plastic finite element analysis was performed to provide insight as to the minimum specimen size limitations for J-characterization in large scale yielding under mixed mode condition. Power-law hardening constitutive equation was employed and plane strain condition was assumed. The criterion used to judge the degree of dominance was the extent of agreement of the stress field near the deformed crack tip with the results for a small scale yielding. It was found that the ratio of the minimum ligament to J/σ₀ for the specimen under mixed mode condition necessary to ensure a J-based characterization was required to satisfy the next condition, L≥80·J/σ₀ for Mode I tensile specimen, L≥(8050)·J/σ₀ for Mode I tensile + Mode II specimen and L≥50·J/σ₀ for Mode II specimen.

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The ductile-brittle transition behavior of a cracked steel specimen under mode II loading has been studied experimentally. Mode II tests were carried out in the low temperature region on center-cracked thin sheet specimens of two kinds of steels (HT50 and S20C). Mode I tests were also carried out. The specimen tested under mode II loading had the same geometry as that tested under mode I loading. This makes it easy to compare the mode II test data with the mode I test data. The results obtained are summarized as follows. (1) The transition temperature under mode II loading was lower than that under mode I loading. (2) The fracture appearance changed with decreasing temperature as follows : (1) fracture with ductile crack alone, (2) fracture initiated by ductile crack and followed by cleavage crack growth, (3) fracture by cleavage crack alone. (3) The direction of cleavage crack extension was inclined to the pre-crack at about 64° in the regions of both (2) and (3) above, whereas the direction of ductile crack extension almost coincided with the shear loading direction.

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Fracture toughness tests conducted for hot-pressed silicon nitride, Si₃N₄, using chevron-notched compact specimens, with special attention paid to the fracture resistance curve (R-curve). Using the results at room temperature, optimum shape design was attemped for the simple fracture toughness test. Then, the validity of the specimens determined was confirmed at elevated temperatures (≤1160°C). The results obtained are summarized as follows. (1) The deeply chevron-notched specimen is judged to be the optimum shape from the view point of accuracy as well as of the simplicity of the test. (2) The resistance to stable crack growth is described as K_R=K_IC. (3) Within the temperature range tested, the fracture toughness, K_IC, and the fracture resistance, K_R, remain unchanged.

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Sintering, hot-pressed and reaction bounded silicone nitrides with common chemical composition were prepared to investigate the characteristics of fracture strength and fracture toughness at elevated temperature, and also the effect of density of them. Mean fracture strength at 1000°C depended on density, while Weibull shape parameter m for fracture strength was influenced by the sintering method. Fracture toughness as room temperature depended on the sintering temperature. The Weibull shape parameter for fracture toughness was higher than and was almost twice that for fracture strength. The size of the defect which controlled the fracture strength in pressurized sintering specimens was smaller than that in non-pressurized specimens. The pressurized sintering which reduces the defect size, and the high temperature sintering which activates to form the column shaped β-Si₃N₄ are desirable to improve the fracture strength and the fracture toughness of silicone nitride.

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The leak before break (LBB) behavior of pipings and pressure vessels is quite important in a nuclear or chemical plant. If a component cannot be broken under the most critical conditions but a leakage occurs at a limited part of the system, then no more protection systems to prevent pipe-whip accidents after a break are necessary and sufficient repair can be done before a catastrophic accident breaks out. In this study, discussion was made to clarify the leak or break conditions of a structual steel (HT 80). Relatively large specimens with various surface flaws were tested by a 200 ton hydraulic tensile machine, operating at about 0.07 Hz, applying axial stresses to the specimens in air at room temperature. The results showed that LBB conditions were slightly dependent on initial crack size and that a crack extention was remarkably slow during the period between leak and failure.

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The time variation of the dynamic stress intensity factor is analyzed for a dynamic one-point bending test in which an edge-cracked specimen is impacted at the midspan with a free end supports condition. A simple formula is derived for calculating Euler-Bernoulli beam. Numerical examples are presented to demonstrate the practical applicability of the formula. It is shown that a reasonable accuracy is obtained by the present formula as compared with a finite element computation, and the CPU time is about 1% of the finite element method. Numerical analyses are also performed for a steel specimen impacted by a falling cylinder. The contact force between the specimen and the impactor is eatimaed by applying Huts'S theory to the local deformation near the contact point. It is found that the one-point bending test specimen is fractured during the first jumping, stage.

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Two dimensional finite element code was developed. It can analyze the deformation of fiber reinforced metal matrix composites under lateral impulsive loading. Two types of rectangular isoparametric element were used. Using this code, elastic-plastic large displacement problems with anisotropy can be treated. The varidity of the code was demonstrated by calculating four different types of problems and carefully examining their results. Problems delt were elastic large displacement dynamic analysis of cantilever beam, anisotropic analysis of rigid punch indentation, elastic-plastic large displacement dynamic analysis of clamped beam and elastic analysis of plate with finite strain. Dynamic tensile tests of boron/aluminum composites were analyzed by this code. Fair agreement was obtained between the experimental and numerical results, though it is difficult to compare these results exactly because of some scatter in the experimental data.

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To formulate the constitutive equations for cyclic plasticity, the subsequent yield surface should be examined carefully. In this paper, using a 50 μm/m offset strain criterion for yielding, the subsequent yield surface has been measured from the experiment for the initially isotropic material of SUS 304. Then the experiment shows the translation, distorsion, expansion and rotation of the subsequent yield surfaces due to the deformation-induced-anisotropy resulting from rotation of the proportional or nonproportional cyclic loading in tension-torsion space. These yield surfaces could be represented by the quadratic form of stress with fourth rank anisotropic coefficient tensor components. These anisotropic coefficient tensor components are found to be related to the strain amplitude of cyclic loading. As a result, the loading function obtained shows its ability to derived the constitutive equations of cyclic plasticity.

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A constitutive equation with one to one relation between the stress rate and the visco-plastic strain rate is derived. It includes strain rate sensitive and insensitive J₂ flow to a deformation type constitutive equation. The finite element method in conjunction with the proposed constitutive equation and tangent modulus method is applied to the analysis of the deformation of a strain rate sensitive block subjected to tension under plane strain conditions. The influence of the type of constitutive equation, the strain rate sensitivity and the deformation rate upon the global and local deformation behaviour is investigated. The results show that the type of the constitutive equation has remarkable effect on the deformation behaviour of a block with weak strain rate sensitivity.

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The title problem was discussed by performing a series of total-strain controlled cyclic tests under uniaxial tension-compressoin and circular strain paths. Constant strain rate of 0.2% /min was specified throughout the tests. The effects of strain amplitude history were examined by changing the strain amplitude between 0.2% and 0.4% (step-up and step-down test) at room temperature, 400°C and 600°C. For temperature history dependence tests, the temperature was changed between 200°C and 600°C, 400°C and 600°C, 500°C and 600°C, respectively by specifying a constant strain amplitude of 0.3%. It was observed that though the history of the preceding cycles with smaller strain amplitude or preceding cycles at lower temperatures was erased by the subsequent cycles with larger strain amplitude or at higher temperatures, the preceding cycles with larger strain amplitudes or those at higher temperatures had considerable effects on the subsequent cycles.

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The constitutive model based on the cyclic nonhardening region is applied first to describing the cyclic plastic behaviour of 304 stainless steel under in-phase and out-of-phase cyclic changes of temperature and athermal strain ; temperature is cycled between 200°C and 550°C. Fairly good agreement between the predictions and the experiments is obtained, if we assume that the internal change proper to the higher temperature (i.e., 500 or 550°C) is induced predominantly under such nonisothermal cyclic loading. On the basis of this finding, then, the evolution equation of isotropic hardening is extended so that it can be valid even for irregular variations of temperature. The validity of the extended model is ascertained by comparing its predictions with the experiments on 304 stainless steel performed recently by Niitsu and Ikegami.

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The stress-strain relation of stainless steel SUS 304 depends strongly on the stress or strain rate even at room temperature. The stress controlled uniaxial creep-ratchetting tests of SUS 304 were conducted at room temperature to investigate the visco-plastic behavior in cyclic loading. The effects of the prestrain and the cyclic stress condition i.e., stress ratio, stress rate, maximum stress and its hold time, on strain accumulation are discussed. The asymptotic stress-strain curve in the tension subsequent to creep-ratchetting reaches the monotonic stress-strain curve. A creep strain rate is given as a function of the magnitude of total strain at the present time even if the material has been subjected to cyclic stressing prior to the creep. Consequently, the strain hardening of the material can be quantified by use of the accumulated strain by creep-ratchetting.

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This study deals with the measuring method about flow stress-strain characteristics of plastics using the indenting hardness test by a spherical indenter. Firstly, hardness Pm(mean contact pressure)-total mean strain of an indentation ε_ic characteristics are obtained with the indenting experiments by a spherical indenter, and flow stress Y-total strain ε(=ε_ic) characteristics are measured using the uniaxial compression tests for plastic materials ; PMMA, ABS, PC and PE. Secondly, Hardness/Flow stress ratio C is formulated, C=9.8 Pm/Y:Y in MPa, as the function of the ratio (ε_ic / ε_r), ε_r is an elastic recovery strain (=Y/E_s, E_s : Young's modulus). Finally, it is shown that flow stress-strain characteristics from the elastic strain range to about the 10-15% strain range of plastics can be obtained using a one time indenting hardness test by a spherical indenter, by means of the calculation with the formulated equations in this paper and the former reports, and this method can be applied to the present hardness testing machines.

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An optimum design technique of the stiffner layout which gives minimum compliance is developed. A thin plate with stiffners is treated as an anisotropic plate of pseude-continuous structure, and is discretized into the finite elements. The minimum compliance design subjected to the constant volume, it which the distributions, of angles of the stiffner arrangement and the stiffner densities are varied, is determined by the recursive quadratic programming technique. By applying this design technique, the optimum layout of the stiffner of the rectangular plate under some typical loading and supporting conditions are obtained.

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In this paper, a technique for applying two-dimensional finite element model to biomedical analysis is studied. The analytical models for total hip replacement (THR) and total knee replacement (TKR) are proposed as the in-plane strain and stress models, respectively. In these models, many convenient approximations are applied for the load conditions, structural shapes and material properties. The stress distributions and deformations calculated for the models of THR and TKR are compared with the results obtained by the corresponding experimental models. From these results, the availability of the two-dimensional finite element model for biomedical analysis is discussed.

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