Rotating bending and torsional fatigue tests were carried out on the specimens of spheroidal graphite cast iron under constant amplitude loading or two-step loading. The initiation and propagation behaviors of microcracks were investigated through the successive observations by the plastic replica method and the observations of the fracture surface by a SEM. The obtained results show that the fatigue lives of the specimens under both types of loading are determined mainly by the propagation lives of small cracks. The ratio of fatigue limit τ_w/σ_w, is 0.79. The crack which is related to final fracture appears at a microshrinkage cavity. Miner's rule based on the fatigue life holds in rotating bending fatigue but does not necessarily hold in torsional fatigue.

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Rotating bending and torsional fatigue tests were carried out on plain specimens and specimens with a hole of rolled carbon steel which were diffusion annealed. The present specimens are regarded as isotropic materials although the original materials have a banded structure. The fatigue limit ratio between rotating bending and torsional fatigue (τ_w/σ_w) of the specimens is different from that of a fully annealed rolled carbon steel, and is approximately the same as that of isotropic cast carbon steel. We should use isotropic materials in discussing the effects of combined stresses on fatigue. In the torsional fatigue tests, crack propagation on plain specimens was of the shear type in the initial stage and of the tension type in the later stage. Cracks of the shear type were generated in both the circumferential and axial directions, and their length was shorter than that of fully annealed rolled carbon steel. There was no great difference between the nonpropagating crack length in torsion and that in rotating bending. The crack growth law in rotating bendig and that in torsion are expressed by dl/dN∝ σⁿ_al or dl/dN∝ τⁿ_al, respectively.

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A fatigue failure criterion based on the concept of linear notch mechanics for predicting the fatigue life of notched FRP plates is subjected to further experimental scrutiny. An experimental program is presented which examines the effect of notch depth on the fatigue failure of notched FRP plates. This is accomplished by obtaining experimental data on the notched specimens of a glass fabric/epoxy laminate for a wide range of notch geometries in pulsating tension. The process of initiation and growth of fatigue damage near the notch root was measured by means of the luminance-measuring system with a CCD camera. The experiment shows that the number of cycles required to initiate fatigue damage was governed predominantly by both the notch-root radius and the maximum elastic stress at the notch root, while it was independent of notch depth. On the basis of the fatigue failure criterion mentioned above, the experimental results can be clearly elucidated.

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Fatigue tests have been conducted to investigate the crack growth characteristics of pure titanium in NaOH solution. At ΔK≤10 MPa √(m), the crack growth rates in NaOH solution were enhanced compared to those exposed to air, while at ΔK > l0 MPa √(m), the crack growth rates in both environments were identical. Since the crack growth rates in NaOH solution were still higher after allowing for crack closure, this acceleration at lower ΔK levels was due purely to an environmental effect. The fracture surfaces at a higher ΔK regime, where crack growth rates were similar in both environments, revealed a preferentially transgranular mode. On the other hand, in the regime where the crack growth rates were accelerated in NaOH solution, cleavage-like facets were observed which increased with decreasing ΔK. Based on the results of da/dN-ΔK relationships and fracture surface observations, it was concluded that the higher crack growth rates in NaOH solution were not attributed to stress corrosion cracking (SCC), but to hydrogen embrittlement as a result of an electrochemical reaction at the crack tip.

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Two-step loading LCF tests were conducted on a cyclic hardening SUS 304 stainless steel to examine the effect of prefatigue damage on the subsequent crack growth rate after switching the strain level. The effect of prefatigue damage yielded overshooting and undershooting of stress amplitude in comparison with single strain cycling and subsequently caused acceleration and retardation of the microcrack growth rate. Those trends were reversed depending on the combination of the level of the first and the second strain amplitude. Martensitic transformation measured by the X-ray diffraction method revealed that increasing strain amplitude promotes the transformation and results in acceleration of microcrack growth.

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The purpose of the fatigue test is to evaluate the nonpropagating depth limit of fretting fatigue cracks that can be initiated at the inner end of the wheelseat of a Shinkansen vehicle axle by linear elastic fracture mechanics. Considering the artificial flaw as an ideal crack, the result of fatigue tests such as the difference in crack growth behavior according to the depth of artificial flaws can be explained by the stress intensity factor range ΔK_r. 'The difference in crack growth behavior of flaws created on the gear-side wheelseat and the counter-gear-side wheelseat can also be explained by ΔK_r. ΔK_r is calculated using the weight function method from the residual stress distribution at the wheelseat and FEM analysis on the initiated stress distribution, considering a relative slip generated between axle and wheel at the inner end of the wheelseat during the fatigue test.

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In order to investigate crack growth characteristics by thermal striping in sodium used for FBR, thermal striping tests in sodium have been conducted using Type 304 stainless steel and its plasma carburized materials. The results showed that the threshold stress intensity factor range, derived from a thermal stress analysis on the condition of plane stress, could predict the final lengths of the nonpropagating cracks. The stress intensity factor range of carburized material increased with the change of properties, especially the modulus of elasticity. Therefore, as the carbon concentration increased, the cracks were produced earlier and the final crack lengths were longer.

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In this paper, the numerical solution of singular integral equations is discussed in the analysis of interface cracks and angular corners. The problems are formulated in terms of a system of singular integral equations on the basis of the body force method. In the case of an interface crack, the unknown functions of the body force doublet densities which satisfy the boundary conditions are approximated by the products of the fundamental density functions and power series. In the case of angular. corners, the unknown functions of the body force densities are expressed as a linear combination of two types of fundamental density functions and power series, where the fundamental density functions are chosen to express the symmetric stress singularity of 1/r^1-λ1 and the skew-symmetric stress singularity of 1/r^1-λ2. The accuracy of the present analysis is verified by comparing the present results with the results obtained by other researchers and examining the compliance with the boundary conditions. The calculation shows that the present method gives rapidly converging numerical results for these problems as well as for ordinary crack problems in homogeneous materials.

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In this paper, a combination of the boundary element method and the finite element method was applied to the stress intensity factor analyses of an interface crack in adhesive joints. The virtual crack extension method was utilized for finite elements allocated around a crack tip to obtain the energy release rate of a crack. The superposition technique proposed by Matos was utilized for the mode separation of the stress intensity factor of the interface crack. We applied the present method not only to a bimaterial plate with a center interface crack, but also to adhesive joints with a center interface crack or a slant interface crack to show the effectiveness of the present method for analyses of an interface crack in a very thin adhesive layer. Furthermore, the fracture toughness of an adhesive joint with an edge crack for various adhesive thicknesses was experimentally determined using the present analytical method. As a result, we obtained a constant fracture toughness regardless of the thickness of the adhesive layer.

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In this paper, the singularities for a crack terminating at a bimaterial interface are studied as a plane problem. The bimaterial body is composed of two elastic bodies : one is isotropic and the other is orthotropic. The crack is assumed to be in the isotropic body. The eigenequation, by which the order of stress singularity is determined, is given in an explicit closed form. The eigenvalues are calculated for various geometries and material combinations. It is shown that the stress singularities depend only on four effective elastic constants, besides the inclination angle of the crack.

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A molecular dynamics parameter (MDP), which J-integral is expanded to, is proposed for a molecular dynamics (MD) fracture simulation and is applied to a two-dimensional α-iron problem under simple tension. For this model a pair potential described by a polynomial expression is chosen as an interatomic potential. Closely packed lattice structures are assumed in the present calculation. The edge crack arranged in the middle of the analysis body is perpendicular to the tensile loading direction. The brittle fracture is analyzed under the fixed displacement boundary condition in the tensile deformation process. MDP₁ is calculated on several paths similarly to J-integral. MDP₁ increases slowly before fracture and decreases steeply after that in any path. In order to investigate the validity of MDP₁ the critical stress intensity factor K^MDP_IC is calculated. K^MDP_IC corresponds well with the decelis and Mullins K_IC. MDP value can be applied to an estimation of the initial stage of macroscopic fracture phenomenon with high reliability.

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In order to investigate the effects of nozzle diameter and screw design on the fracture mechanism when FRPC is molded with an injection molding machine, the acoustic emission monitoring technique is used during tensile testing of the molded specimens. The optimal nozzle diameter and screw design can be derived by the maximum load P_max and the loads at the change in damage mechanism R_b and P_c which are determined by the AE energy gradient method. The damage at the loads P_b and P_c is discussed by the peak frequencies in using the AE frequency analysis.

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In order to investigate the effect of plastic deformation near a crack tip on the accuracy of the measurement of static and dynamic fracture toughnesses by the caustic method, a two-dimensional finite-element simulation of fracture toughness tests is performed. A crack subject to a static or dynamic uniform pressure on its surfaces is considered, and caustics in reflection are generated by assuming the plane stress condition. Crack propagation is simulated by the node release technique. The numerical errors due to the node release technique are eliminated by truncating high-frequency components in the solution of displacements. It is found that the plastic deformation near a crack tip under static loadig has a greater effect on the "measured" stress intensity factor than that under impact loading. For impact loading, the smallness of the stress-intensity-factor-controlled field is found to be more important than the effect of plastic deformation.

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The characteristics of mixed-mode fracture toughness in silicon carbide were investigated using flexural tests with controlled surface flaw and the diametral compression tests with cracked Brazilian disk. Experimental results show that the slits introduced by the YAG laser in the Brazilian disk can be treated as cracks. The relationships between K_I and K_II under the mixed-mode fracture conditions are consistent with a prediction based on the coplanar energy release rate theory. While the crack size does not affect the mixed mode fracture conditions, the residual stress at cracktips influences the fracture toughness. Scanning electron microscope observations reveal that the effect of friction is very small in the mixed-mode crack extension.

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In this paper, an infinite hollow cylinder with a V-shaped notch under torsion is considered. The local behavior of the stress around the notch tip is defined in terms of one parameter K_{III, λ2}, which represents the intensity of the singular stress field. The parameter K_{III, λ2} is analyzed by the body force method. In the numerical analysis, a new technique is introduced to improve the accuracy of the solution.

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Asymmetric three-point bending of a layered beam with an interface crack is analyzed on the basis of classical beam theory. Axial forces induced by bending in the parts of the beam above and below the delamination are determined by regarding the cracked part as two lapped beams hinged at both ends. The compliance and the energy release rate are then derived. Numerical analyses based on the finite-element method are carried out, which show that delamination growth occurs in a mixed mode ; i. e., both the normal separation (mode I ) and mutual sliding (mode II ) of the crack surfaces contribute to the fracturing process. Finally the decomposition of the energy release rate into mode I and mode II components is made by combining the recent analysis for the energy release rates by Toya and two-dimensional linear beam solutions by Suo and Hutchinson.

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In this study, the theoretical analysis of a three-dimensional transient thermal stress problem is developed for a nonhomogeneous hollow sphere with respect to rotating heat source from the outer surface. We assume that the hollow sphere has nonhomogeneous thermal and mechanical material propeties is the radial direction. The heat conduction problem and the associated thermoelastic behavior for such nonhomogeneous media are developed by introducing the theory of laminated composites as one theoretical approximation. The transient heat conduction problem is evaluated with the aid of the method of Laplace transformation. The associated thermoelastic field is analyzed by making use of the thermoelastic displacement potential and the complementary harmonic function. Some numerical results for the temperature change and the stress distributions are shown in figures.

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Tensile tests of S45C/Si₃N₄/S45C bar-type specimens which were bonded in 1987 and 1988 by a metalizing method, were conducted at room temperature in laboratory air. Using broken specimens, the effect of bonding-induced residual stress on the tensile fracture stress was investigated in this study. The main results obtained were as follows. (1)When the length of Si₃N₄ was nearly equal to the diameter of the specimen, the analytical results based on a finite-element method showed the validity of measuring the residual stress near the interface of the unbroken side. (2)The residual stress near the interface which was measured by an X-ray diffraction method was tensile and increased monotonously toward the interface. (3)The residual stress distributions were influenced by the diameter of the specimen, the length of Si₃N₄ and the year of bonding. (4) The tensile fracture stress decreased with the increase of the interface residual stress which was extrapolated from the residual stress distribution, and a linear relationship was found between them.

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An equation for investigating the intensity of singularity in the stress field near the apex in a three-phase bonded structure formed from isotropic homogeneous rectangular wedges was derived using the theory of elasticity, in a previous paper. In this paper, the distributions of the intensity K for free surfaces subjected to normal loadings in a singular stress field represented by the types Kr^P-1 and K log r near the apex in the three-phase bonded structure with arbitrary wedge angles, are investigated. Theoretical values of K and numerical ones of K analyzed by the finite element method (FEM) are shown and discussed for different combinations of materials and wedge angles.

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The singularity in the stress field near the apex in three-phase bonded material with arbitrary wedge angles depends on the combinations of material properties and the bonded wedge geometry. The stress singularity is represented by the orders O(γ^p-1), O(log r) and O(1) for real rootsρ, and O(γ^ε-1 cos[η logγ]) and O(γ^ε-1 sin[η logγ]) for complex roots ρ=ε+ιη, and every stress component (σ_γγ, σ_γθ, σ_θθ) is denoted as the same order. However, the order in the displacement field has not yet been clarified. In this paper, the displacement distribution near the apex in a three-phase bonded structure under surface traction is discussed for different combinations of materials and wedge angles within the theory of elasticity, and is analyzed by the finite element method (FEM). Comparing theoretical results of displacement distribution with numerical ones, it is shown that the order of displacement field in theγ-direction and that of displacement field in theθ-direction differ from each other.

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The acoustoelasticity with ultrasonic transverse waves was applied to analyze an elastic-plastic state of a shrink-fit specimen of SS41 steel. The specimen was made by inserting a cooled circular disk into a circular hole in a heated square plate. Before and after shrinkage fitting, two transverse velocities and polarization directions were measured by the sing-around method and spectrum method. The Stress distributions were obtained using these data applied to the acoustoelastic law, and it was confirmed that the elastic-plastic boundary could be determined from the distribution profile of the difference between the two transverse velocities, and also that, on diagonal lines of the specimen, the principal stress difference could be determined nondestructively. Comparison of the ultrasonic results with strain gauge results showed that velocity change due to plastic deformation was significant in the plastic region of the outer plate. Although confined to the velocity difference, such changes were experimentally verified.

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First, general solutions for an elastic medium with an elliptic elastic inclusion are given under the uniform in-plane and out-of-plane loads applied at infinity. Next, the stress and displacement fields for the same problems for a viscoelastic medium with an elliptic elastic inclusion are obtained by use of the correspondence principle between elasticity and linear viscoelasticity. The time-dependent behavior of the material of the matrix is assumed to be represented by typical rheology models such as Standard-, and Burgers-models. Several numerical examples are shown by graphical representation with varition of the aspect ratio b/a or a/b of an elliptic elastic inclusion.

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We present a numerical analysis method and results using the traction method for optimization problems of domains in which linear elastic problems are defined. In this paper we consider the application of the traction method which was proposed as a solution to domain optimization problems in elliptic boundary value problems. The minimization problems of the mean compliance were treated. Using the Lagrange multiplier method, we obtain the shape gradient functions for these domain optimization problems from the optimality criteria. In this drawing process we consider the variation of the surface force acting on the boundary and the variation of the stiffness function and the body force distributed in the domain. We show successful solutions of the problem of an infinite plate with a hole and of the problems of a rectangular plate clamped at both ends.

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The plane elasticity problem of an infinite anisotropic plate containing a circular isotropic inclusion is considered, and Green's functions are derived for a point force and/or a dislocation acting at a point in the exterior of the inclusion. The complex potential approaches by Muskhelishvili and Lekhnitskii are used to express the elastic fields in the isotropic material and the anisotropic material, respectively. The general solutions are obtained in a closed form. A special case of two joined isotropic-anisotropic half-planes is deduced from the general solution.

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Link chains used in chain hoists are usually subjected to combined loads of tensile loads and bending moments when they pass through sheaves. Until now, no investigations have been done on the stress distribution of chains subjected to combined loads. In this paper, the stress distribution of chains subjected to combined loads is analyzed using the elastoplastic finite element method. Using the stress distribution in the chains, the strength of the chains is evaluated by von Mises' criterion. The effects of the contact angle of each link chain are shown using von Mises' stress. For verification, photoelastic experiments and measurement of strain were performed. It is found that the strength of link chains subjected to combined loads is about 17% less than that of link chains subjected to tensile loads. In addition, it is clarified that the strength of link chains can be improved by optimizing the link pitch and the link width.

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Constitutive model to describe rate-dependent nonlinear inelastic behavior of unidirctionally fiber-reinforced composites is developed from phenomenological and continuum mechanics points of view. The fibrous composite is treated as a homogeneous medium which hardens with inelastic deformation. The inherent anisotropy due to the fibers is assumed to be transversely isotropic. We first derive a kinematic hardening model in invariant form. The constitutive modeling is based on the well-established thermodynamic formalism for internal state variable theories, where the thermodynamic potentials are defined by using a transversely isotropic tensor of fourth rank. In this model the evolution of the internal state variable is prescribed by the nonlinear kinematic hardening format of Armstrong-Frederick type. This enables us to describe the rate-dependence of the nonlinear anisotropic inelastic behavior of fibrous composites. Then, an isotropic hardening model is derived from this model by using an empirical method which assumes a particular representation of the kinematic hardening variable. Finally, some generalized expressions which are implied by these formulations are presented.

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Oxidation kinetics of as-received and pre-heat-treated (PHT) C/C composites fabricated by the preformed yarn method were investigated. The weight loss due to gasification was measured as a function of oxidation time under various isothermal temperatures from 600 to 1100°C in air. In situ observation of microscopic morphological changes due to oxidation was conducted by a laser microscope during heating to 950°C in flowing air. Then, degraded inner and outer morphologies of C/C composites oxidized at various temperatures were examined through observation by a SEM and measurement of pore distribution by a mercury porosimeter. As a result, degraded morphologies due to oxidation were extremely different depending on the oxidation temperature. Inner structural changes became obvious, as the oxidation temperature decreased. Therefore, the rate-determining process of oxidation reaction was changed from the surface chemical reaction to reactive gas diffusion across the boundary layer of gaseous oxidation product as the oxidation temperature increased. Oxidation reactivity of as-received C/C was higher compared to that of PHT C/C due to metallic impurities such as Fe. Furthermore, it was considered that initial oxidation occurred preferentially in the matrix due to residual stress which was generated at the fiber and matrix interface by thermal expansion mismatch of each component at fabrication.

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It is still essential for high strength engineering ceramics to improve fracture toughness for a wide use in primary structural applications. The purposes of this paper are to apply the ductile metallic phase toughening mechanism proposed previously to ceramics/metals functionally gradient materials (FGMs) and to confirm the possibility of improvement of fracture toughness without the reduction of strength. Fracture characteristics were investigated for symmetrically step by step graded FGMs (Cr₃C₂/Ni, TiC/Ni) on the basis of fracture mechanics and fractography. It was found that the ductile metallic phase toughening mechanism has a good potential for ceramics/metals FGMs.

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The effects of silicon content and austempering conditions on impact strength in austempered spheroidal graphite cast steel (AGS) which had nearly the same Young's modulus as conventioral carbon steels were examined. Impact strength increases with silicon content, attains a peak value at 3. 0%, and then begins to decrease regardless of austempering conditions. Also, there are the optimum austempering conditions against impact strength, those are austempering time of about 1800 seconds and austempering temperature between 620 K and 650 K. Impact strength in AGS is closely related to the amount of retained austenite, all the optimum conditions that yeild maximum impact strength, converge to the direction where the amount of retained austenite increases.

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Bending fracture tests of sintered silicon nitride disks with shoulder fillet were performed at room temperature and at l000°C. The comparison of the experimental results with statistical reliability analysis showed that strength evaluation method based on the 2-parameter Weibull theory can be applied to estimate the strength of multiaxial stress stated ceramic components. It was observed that the choice of fracture criteria had little effect to the reliability analysis. The correlation of the strength of ceramic components under multiaxial stress state with uniaxial Strength data was made possible using the concept of equivalent stess and effective volume.

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The strain distribution of grains on the free surface of polycrystalline iron during compressive plastic deformation is studied. Logarithmic strains are calculated by measuring maximum distances of grain boundaries of respective grains at every five degree interval from the loading direction. The strain distribution in all directions for a grain is approximated with an ellipse using the method of least squares and the principal strains are obtained as the long and the short axes of the ellipse. It is found that there are some deviations in the strains of grains, but the mean value of the strains in the loading direction of all grains is almost the same with the applied strain. The three-dimensional shape of surface roughening is measured and the peaks and the bottoms of the surface roughness curves are obtained on the map of grain boundaries. The surface roughness of each grain is also measured and the relation between the deformation of grains and the surface roughness is discussed.

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Molecular dynamics simulation based on Morse potential is used to investigate tensile deformation of bicrystalline and nanocrystalline aluminum. The computational cells contain [001] (310) Σ = 5 tilt grain boundaries. The simulations show that both bicrystalline and nanocrystalline aluminum are more ductile at higher temperatures, and that nanocrystalline aluminum is more ductile than bicrystalline aluminum. When nanocrystalline aluminum is subjected to tensile deformation at a high temperature, its atomic configuration tends to become similar to that of single-crystal aluminum. This may be the cause of higher ductility in nanocrystalline aluminum. When the temperature is low, or when the strain rate is high, this tendency is weakened because of insufficient thermal activation or insufficient time for changes in atomic configuration, respectively.

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Fundamental solutions are derived for the two-dimensional elastic field in a plane of two joined semi-infinite plaes, one of which is isotropic and the other anisotropic. A concentrated force or a dislocation is applied at a point in the isotropic semi-infinite plate. A closed-form solution is obtained using the complex variable method. A special case of isotropic-orthotropic two-phase medium is deduced from the general solution, as well as the case when the principal direction of elasticity of the orthotropic medium is not parallel to the interface of plates.

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It is said that cancerous bone of animal is optimum in the mechanical viewpoint and its configuration has some suggestion for orthopedic operation. It is necessary to know the loading conditions from the configuration. Cancerous bone resembles a truss continuum. Hence, this paper considers the relation between loads and optimum configuration of a truss continuum. First, applying the inverse variational principle based on the principle of mimimum potential energy, an optimization problem for the distribution of members of a truss continuum is formulated with respect to the density and direction. Second, the change of optimal structure with loading condition is considered. Third, the possibility of identifying unknown applied loads from the optimal shape is discussed. Lastly, the optimization and identification are investigated analytically for a truss continuum with a single element.

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A systematic method of spall damage analysis was developed on the basis of damage mechanics. By use of a scalar damage variable, the damage evolution equation of Lemaitre et al. and the viscoplastic constitutive equation of Perzyna modified for the damaged materials were incorporated into the commercial finite-difference program MANJUSRI-3 D for nonlinear dynamic analysis. The process of spall damage and histories of stress wave propagation and temperature were analyzed for plate impact of OFHC copper disc targets. The results of analysis of the stress history and the particle velocity at the rear surface of the target plate were compared with those of the corresponding experiments.

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Transient behaviour from static to kinetic friction and the dynamic response of a contact surface were experimentally investigated on two bodies with a large contact area. Slip and tangential force at several locations over the contact surface were measured. Slip is initiated locally in a small region associated with a sudden decrease of local tangential force and propagates over the surface generating a stress concentration to break junctions in adjacent regions, finally followed by a large-scale slide between the two bodies. Propagation of slip depending on the intrinsic strength of junctions and their distribution on the contact surface can be increased to as high as the elastic stress wave velocity. It is also found that the unloading stress wave which is emitted from the slip region is reflected at specimen boundaries to the contact surface and plays an important role in its dynamic response.

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This paper deals with numerical solutions of singular integral equations of the body force method in interaction problems of elliptical inclusions under general loading conditions. The problems are formulated as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the densities of body forces distributed in the x- and y-directions of infinite plates having the same elastic constants of the matrix and the inclusions are unknown functions. In order to satisfy the boundary conditions along the inclusions, eight kinds of fundamental density functions proposed in our previous paper are used. Then the body force densities are approximated by a linear combination of the fundamental density functions and polynomials. The accuracy of the present analysis is verified by comparing with the results from previous research. The present method is found to give rapidly converging numerical results for stress distribution along the boundaries of both the matrix and the inclusions.

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This paper describes the numerical method for domain optimization problems based on the traction method. The traction method was recently proposed as a solution to domain optimization problems. With the traction method, the domain variation is analyzed under a condition where the objective functional decreases. We propose a convenient numerical method using a general purpose FEM to apply the traction method to practical problems. The domain optimization problem treated here is a mean compliance minimization problem of linear elastic structures. The computed results of a multiply connected plate and a solid torsion bar are compared with those obtained by other authors. The practical application of the method is also demonstrated with a plane sample and a solid one. The results show sufficient validity of the proposed numerical method for practical domain optimization problems.

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The effect of shapes and configurations on the vertical bending rigidity of a car body was investigated by strength testing of scale models and actual car bodies, and by FEM analysis, which was performed to evaluate the vertical bending rigidity of car bodies with bent side frames and corrugated outside plates. The following results were obtained. (1)The validity of the FEM analytical model was verified. (2)Using the above analytical model, the effect of the bent angle of a side frame and the rigidity of a door frame and a corrugated outside plate on the vertical bending rigidity of a car body is evaluated.

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In this paper, the construction of an impact testing machine and a system for measurement are attempted to estimate the energy absorption abilities of thin-walled members by impact loading. The cross-head, of which mass is 18 kg, can be accelerated up to 16 m/s by both gravity and air pressure, and crushes various types of members. This testing system provides precise measurements of loads applied to the members and the crushing distances. By using this system, circular cylinder specimens of aluminium and carbon-fibre-reinforced plastic are tested in order to study the influences of the shape of specimen, deformation mode and material on the energy absorption abilities. Some of the results are also compared with those from static crushing tests.

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In order to improve the automation of defect inspection by careful examination by the naked eye, we consider that defects should be understood as special featured regions, and we present a new approach for detecting such defects. The approach uses "a defect model" for recognizing defects. The defect model is carefully constructed based on visual features of defects, including their sizes, shapes, and intensity or shade, and also the inspector's knowledge and experience. This approach is applied to detect internal weld defects which appear in X-ray radiographic films. On the basis of visual features and size distribution of observed defects in 107 films and the global feature of the weld zone, an efficient defect model is constructed geometrically and arithmetically. The results show success in detecting very small and fuzzy defects.

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An ultrasound detection system with optical heterodynes shows nonlinear behavior in the large-ultrasonic-amplitude region ( >λ/8, λ : wavelength of detecting light), and possesses some problems in the measurement of laser ultrasound (ultrasound generated by laser deposition), especially of thin specimens. We studied the mechanism of the nonlinear response and found a method to improve it. Through experiments, we obtained an improved demodulation method using signal processing techniques to extract actual ultrasonic waveforms in the large-amplitude region, and confirmed its effectiveness. We also carried out numerical experiments on the characteristics of our improved demodulation, method and the standard demodulation method. The results show that compared with the standard demodulation method, our method is more robust against noise of beat signals, and more useful for measuring laser ultrasound even in the small-amplitude region.

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At the present time, there is no adequate method for experimental measurement of wall stresses in the intact ventricle. Thus, many mechanical models to predict such stresses have been proposed, in which the residual stress was ignored so that the circumferential stress at the endocardium of the left ventricle was extremely large compared with that at the epicardium. The work expressed, such as oxygen consumption, is supposed to be almost uniform through the wall thickness, or to be somewhat larger at the endocardium than at the epicardium. The models may be improved by taking account of residual stress. To take residual stress into account in mechanical models, one must measure residual strains in the no-load state of the left ventricle. The residual strains were calculated by using sliced canine left ventricles obtained during isovolumic contraction. The residual strains determined from the experiment were applied to the model proposed in the present paper and the distributions of the wall stresses were obtained. As a result, the stress concentration at the endocardium of the left ventricle was found to be largely reduced.

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Seven human knee cadaveric specimens were dissected down to joint capsule and fixed to a material testing machine at 30°of flexion. Three components of the force output from a universal force-moment sensor were recorded during an anterior translation of Lachman test before and after each soft tissue around the knee was cut off. By assuming the principle of superposition, the in situ force in each tissue was calculated. Results revealed that the in situ force in the anterior cruciate ligament (ACL) is approximately identical to the applied force to the knee, however ; in situ forces in other tissues were almost zero. It was also found that the in situ force in the posterior quarter of the anteromedial portion of the ACL (PQ) is larger than those in anterior quarter of the anteromedial portion of the ACL (AQ) and posterolateral portion of the ACL (PL).

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In this paper, the phenomenological potential theory, obtained by the modificaton of Mitsui's self-induced translation model, is applied to the simulation of the contraction of a sarcomere in skeletal muscle. The equation of motion of each myosin head is solved under the viscosity dominant assumption. The isotonic and isometric contractions of a half sarcomere was simulated. The numerical result of the load-velocity relationship at the isotonic contraction shows a good agreement with Hill's experimental equation. The numerical result of the length-tension relationship contents with Gordon's experimental result qualitatively. The result of quick release in the isometric contraction demonstrated the visco-elastic feature of skeletal muscle. Therefore, it can be concluded that this macromolecular dynamics simulation will contribute the investigation of the mechanism of skeletal muscle contraction.

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The in vitro experiment of excitation-contraction coupling of semitendinousus muscle of Rana Castesbeiana has been done. We measured the time history of tension force in case of isotonic contraction. The characteristics of the force history changed according to the condition of electric pulse stimulation, e. g., from twitch to tetanus for single and sequential stimulation, respectively. Two numerical models to analyze the complete E-C coupling dynamics are proposed. One is the modified self-induced translation model, the other is the biochemical reaction model, which is newly proposed. The latter modelled the relationship between Ca²⁺ density and ATPase activity. The process is modelled as follows : first, electric stimulation (excitation), followed by the release of Ca²⁺ from the sarcoplasmic reticulum, (also taken in by Ca²⁺ pump), the binding of Ca²⁺ at binding sites of troponin, and finally, activation of ATPase between the myosin head and actin filament. The comparison between the experiment and numerical simulation shows difference in the magnitude of force and the characteristics of the time history of force. The former is caused by the difference of size, i. e., whole muscle in the experiment and the half-sarcomere in the numerical simulation. The latter is due to the incomplete model's of the biochemical reaction process, e. g., Ca²⁺ density-ATPase relationship.

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A numerical simulation system using the 3-dimensional finite element method (FEM) is established to reproduce the performance of the left ventricle during one cardiac cycle, which may ultimately provide useful information for medical diagnoses. This simulation system consists of a 3D-FEM mechanical model of the left ventricle based on mechanical properties of myocardial muscle and a circulatory system model which provides the preload and the after-load to the model of the left ventricle. In this paper, pressure-volume relationships estimated using the present system for various peripheral vascular resistances, aortic compliances and characteristic impedances are compared with those obtained from the corresponding canine experiments. It is shown that the two results coincide with each other to a reasonable accuracy.

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