Type 316 FR stainless steel has been developed as a candidate material for fast breeder reactor of next century. For the structural integrity design of high temperature components including reactor vessel, long-term data and analysis method are investigated for the new 316 FR steel especially to evaluate its time-dependent low-cycle fatigue behavior. The present paper reports dependencies of fatigue life on the strain rate from 10^-2 to 10^-5S^-1, and on the temperature dependencies from 500°C to 600°C. Data are analized by a parametric method formerly proposed by the authors. It is shown that the method has a good predictability of the fatigue life up to very low strain rate of 10^-6S^-1.

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Stress-strain analyses for Sn-Pb cutectic solder joints in a thin single outline package (STOP), a ball grid array (BGA) assembly, and a leadless ceramic chip carrier (LCCC) were carried out for investigation of plastic-creep behavior, and of stress relaxation behavior due to accelerated thermal cycling tests or the operating conditions. the temperature dependence of plastic behavior (yield stress) and creep behavior (creep properties) were taken into account in all numerical analyses. The results of finite element analysis (FEA) show that in an accelerated terperature cycling test, long high-temperature and low-temperature dweel times do not contribute to an increase in the cyclic inelastic equivalent strain range in solder joints, although the creep behavior occurring during the dwell times under operating conditions is very important in estimation of the fatigue life of solder joints. Based upon the results of the strain analyses, an efficient temperature cycling test process for microelectronic solder joints was proposed, and cycling tests were carried out. The experimental results show that the thermal fatigue life of microelectronic Sn-Pb eutectic solder joints can be predicted by an associated fracture parameter of total equivalent inelastic strain range, and the fatigue life of solder joints follows Coffin-Manson's law.

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An isothermal mechanical fatigue test method and fatigue testing equipment were developed to investigate the low cycle fatigue strength of Sn-Pb eutectic solder joints. Based upon the results of finite element analysis, it is found that the rate of inelastic strain components (plastic strain and creep strain) in the solder joints can be accurately controlled by the displacement rate of the linearactuator of the test equipment. The isothermal mechanical fatigue tests were carried out by controlling the displacement at a very high displacement rate, and a very low displacement rate, respectively ; only plastic strain was generated in the solder joints at the high displacement rate, and only creep strain at the low rate. It is found that the low cycle fatigue life of Sn-Pb eutectic solder joints is not grealty affected by the ratio of inelastic components. Therefore, it can be said that the low cycle fatigue life can be estimated from the equivalent inelastic strain range, and the relationship of the cycles to failure and the strain range follows Coffin-Manson's law. In comparison of the mechanical fatigue strength results with the results of the cyclic thermal tests, it was found that the mechanical fatigue test method can be used as a good accelerated test method for the thermal fatigue strength of Sn-Pb eutectic solder joints.

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Fatigue crack growth tests using center-cracked [M (T)] specimens and single-edge-cracked (SEC) specimens of SUS304 steel were conducted to examine the behavior of fatigue crack growth in the near-threshold regime at 623 K. Crack closure was eliminated by keeping K_max constant in ΔK decreasing test in order to obtain easily the threshold value expressed in terms of effective stress intensity factor range, ΔK_ett. By increasing the value of K_max and/or ΔK for a crack in a threshold condition, the fatigue crack growth behavior was investigated even in the region below the threshold value obtained by using the conventional ΔK-decreasing test. When the value of K_max was increased in the conventional threshold condition, crack growth was observed in the lower ΔK region. Crack growth was further observed repeatedly after successive increase in K_max in the newly established lower region below the conventional threshold value. In the region below a certain value of ΔK, however, crack no longer grew even after the change of K_max. Discussion was made on the characteristics of threshold.

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At a tee junction point of piping system, hot water and cold water is mixed with each other in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on a inside surface of the pipe just after the connection point. The temperature fluctuation yields a cyclic thermal stress near the pipe surface and results in the crack initiation. In this study the thermal stress distribution was analyzed for a semi-infinite plate model and the fatigue crack growth behavior was examined. As a results, the thermal fatigue crack is arrested and the arrested crack depth is found to be in proportion to the reciprocal root of the frequency of temperature fluctuation.

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The method of caustics in combination with a Cranz Schardin high-speed camera was utilized to study dynamic crack propagation in epoxy specimens. Single-edge-cracked tensile specimens were fractured under pin-loading conditions so that cracks could undergo acceleration and deceleration stages in one fracture process. Dynamic stress intensity factor K_m and crack velocity a were evaluated in the course of crack propagation. Caustic patterns at the loading points were also recorded to estimate the dynamic load P applied to the specimen. Unloading rate P, i.e. the time derivative of P, was determined as a function of time t, and its correlations with K_m and a were examined.

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The delamination crack growth behavior under iso-thermal and thermo-mechanical fatigue were investigated with unidirectional CF/epoxy laminates. Tests were conducted either in air or in water with double cantilever beam specimens. The crack growth tests were conducted under constant ΔK conditions at the load ratio of 0.5 with a loading frequency of 1/180 Hz. The test temperature was between 20°C and 70°C. In air, the effect of test temperature on the crack growth behavior was not observed in the iso-thermal fatigue tests, and the crack growth rates for the thermomechanical fatigue tests were almost identical to those for the iso-thermal fatigue tests. In water, however, the crack growth rates for the iso-thermal fatigue tests were higher for lower temperature, and the rates for the thermomechanical fatigue test were almost the same value as those for the isothermal fatigue test whose test temperature was equal to that at the maximum load for the thermomechanical fatigue test. The effect of environment was not observed for the iso-thermal fatigue test at 20°C. For the iso-thermal fatigue test at 70°C and in-phase thermo-mechanical fatigue test, however, the crack growth rates in water were lower than those in air.

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This study was done to clarify the influence of complex deterioration on fatigue reliability of thermal plastic in order to construct environmentally sound design system for energy machines. Especially, the influence of recycling process and high environmental temperature on fatigue crack propagation property of fiber-reinforced PA46 were experimentally examined. Main results were as follows ; (1) FCP property was declined remarkably by complex deterioration between elevated temrerature above T_g and recycling process. (2) From fractography using SEM, it could be understood that fibers were easy to pulled out because the matrix resin became ductile due to declining the dynamic elasticity at elevated temperature above T_g. (3) The interfacial bonding between matrix and fibers in specimens were become worse by recycling process and environmental temperature above T_g. Therefor it could be interpreted that the decline of FCP property was caused by the interfacial separation between matrix and fibers.

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Mesocracks controlling fatigue fracture at 1073 K in dual phase TiAl alloy were observed by SEM-servo. In this study, the quantitative analysis of the mesocracks and the remaining life assessment was carried out by applying fractal concept. The main results obtained were follows : (1) The feature of mesocracks growth behavior has fractal characteristics. (2) Fractal dimension is raised with increasing the number of cyclic loadings. Thus, this characteristic of fractal dimension makes possible remaninig life assessment. (3) We design comlex system algolrithm which consists of damage process analysis, fractal modeling and simulating. Furthermore, this algorithm connects material design, structual design and prevenance maintemance.

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Fatigue crack growth properties of diffusion bonded interfaces between A286 and Cu-Cr were investigated, in order to make the damage tolerant design possible. In this study, fatigue crack growth properties of the interfaces, which were obtained from the fatigue tests with three-layer joints, were adjusted based on not only linear fracture mechanics but also elastic-plastic fracture mechanics from the viewpoint of large plastic deformation of Cu-Cr. As a result, it was clarified that fatigue crack growth properties with linear fracture mechanics give conservative characteristics compared with that with elastic plastic fracture mechanics. Also, fatigue life margin of the interfaces was found to be increased with the increase of fatigue crack growth rates.

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The behavior of a crack in a weld line between two different steels and its fracture criterion were studied by employing the CED in an arbitrary direction that can be successfully applied to the behavior of a mixed-mode crack in a homogeneous material from elastic fracture through fracture with large scale yielding. The fracture experiments of the specimens with a crack in a weld line between high tension steel (HT 60) and mild steel (SPC) were carried out, first, under tensile type loading, and it was made clear by observing fracture surface that the mode II type fracture occurs even under tensile type loading in this material combination. Moreover, the CED in an arbitary direction was evaluated through the finite element analyses corresonding to the experiments. It was confirmed through the analyses that the crack here becomes a mixed-mode one with the extension of yielding region because of the difference of yield stress and, by applying the numerical results to the experimental ones, it was shown that the observed crack behavior can be explained by the mode II fracture criterion based on the CED in an arbitrary direction.

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Carbon-steel (S 45 C) plates were lap-bonded using a thermosetting-type epoxy, and shear tests were carried out under tensile loading. The stress levels at which interfacial debonding, initiated during testing, occurred were successively detected using the AE (Acoustic Emission) method. Stress singularity fields exist at the two ends of the bonded overlap. Interfacial debonding was initiated in both these ends when the nominal stress reached 60∼70% of the fracture stress. Both the initiation and fracture stresses decreased with an increase in lap length. This was due to the increase in the bending moment at both ends of the bonded overlap. The stress of the interfacial-debonding initiation can be evaluated using stress-singularity K₁ and energy release rate G₁.

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The stress and strain distributions in adhesive lap joints composed of two dissimilar hollow shafts and subjected to an axial load are analyzed using an axisymmetric theory of elasticity, replacing each hollow shaft and the adhesive with finite hollow cylinders. In the numerical calculations, the effects of the ratio of Young's modulus of the adhesive to that of the hollow shaft, a thickness of the adhesive on the stress distributions at the interfaces between the shaft and the adhesive are clarified. In addition, the joint strength is evaluated by using the stress distribution at the interfaces. The main results are summarized as follows. (1) The stresses in the radial and circumferential directions become singular at the edge of the interface. (2) The stress near the edge of the inner interface becomes larger than that at the outer interface in case of similar hollow shafts. (3) With decrease of Young's modulus of the shaft and with increase of a thickness of the adhesive, the stress increases near the edge of the interface. For verification of the stress analysis, the axial strain distribution at the outer surface of an adhesive lap joint was measured by strain gages when it was subjected to an axial tensile load and the experimental result was fairly consistent with the numerical result. Moreover, the joint strength was tested in both adhesive lap joints of similar and dissimilar hollow shafts and was evaluated by the stress analysis.

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Some analyses of cylindrically anisotropic elastic body with circular opening or circular ring reinforcement have been published for the cases of in-plane loading at infinity and of internal or external pressure around the ring boundaries. This paper gives most general solutions of the problems and presents the closed-form solutions of stress and displacement for concentric multilayered circular hollow or solid inclusions in cylindrically anisotropic elastic medium with debonding and/or shear sliding boudaries of the interface under out-of-plane shear and in-plane loadings at infinity. Several numerical results are shown by graphical representation.

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The analysis of isotropic medium stiffened by an elliptical ring has been performed by authors recently. In order to consider the influence of an anisotropy of the medium, this paper presents the analytical solutions for both in-plane problem and out-of-plane shear problem by means of combination of Leknitskii's anisotropic theory and Muskhelishvili's isotropic theory. Lastly, the multilayered rings are to be considered only in out-of-plane problem.

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Piezoelectric materials are widely used in industrial areas from the excellent results of the mechanical and electrical couplings such as the expectation to reduce stress concentrations by electrical controls. Contrary to this expectation, piezoelectric materials may have some tendencies to develop critical crack growth because of stress concentrations induced by both mechanical and electrical loads. Therefore, it is necessary to study the behavior of stresses and displacements at the vicinity of the stress concentrated region like a cavity or crack as well as elliptical inclusion. In this paper, a two-dimensional electroelastic analysis is performed on a isotropic piezoelectric material containing elliptical defect under the cases of out of plane shear loadings at infinity. General solutions are provided in terms of complex functions, with emphasis being placed on stress concentrations. Several numerical examples are given for both mechanical and electrical loads.

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The stress transfer between an elastic solid cylinder under axially symmetric torsion and an elastic half-space in which the cylinder is partially embedded is investigated. A method of solving the problem is obtained by using Green's functions for axisymmetric torsional body force problems of an elastic half-space and the fundamental solution for torsion problems of an elastic solid. The Green's functions and the fundamental solution are defined as solutions to a half-space and a full space subjected to a torsional body force acting along a circle, respectively. Effects of the shear moduli of elasticity on the stress distributions at the interface are shown. A method of solution is investigated to obtain stress singularity factors at the interface.

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This paper deals with the stress concentration problem of an elastic circular thick walled cylinder with a semicircular notch under torsion. A method of solution is presented for the problem by applying Green's functions for axisymmetric torsional body force problems of an elastic circular hollow cylinder. The Green's functions are defined as solutions to the elastic problem of a circular hollow cylinder subjected to torsional body forces acting along two circles. The Green's functions are shown in this paper. The stress concentration problem is formulated by an integral equation in terms of the Green's functions. Investigations are made on the influences of the inner radius of the cylinder and the radius of the notch on stress concentrations.

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Since finite element method gives us only approximate solutions, there are error exist on its solutions. In order to reduce the error of finite element method, mesh refinement becomes important. In this paper, adaptive remeshing for 2-dimensional elastic problems, especially having stress singularity, is considered. For adaptive remeshing, rational element size distribution on entire computation domain should be estimated. Based on a posteriori error estimation, the rational element size can be obtained in the problem where stress sigularity exists. A parameter for expressing the degree of stress singularity is introduced resulting in an accurate adaptive finite element analysis.

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Appropriate positions of plastic hinges can be evaluated by using the adaptively shifted integration (ASI) technique in the elastic-plastic analyses of framed structures. In this paper the ASI technique is applied to the degenerated Timoshenko beam element developed by Dvorkin et al., which is considering the effect of large displacements/rotations. By slightly modifying the shape functions of Dvorkin's element, the effect of large rotations can be precisely taken into account with the use of the ASI technique. Therefore, precise rigid body rotation about a plastic hinge can be represented by the presented element. Stresses at the hinge are also evaluated appropriately.

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A silicon carbide sphere indentation was subjected to the surface of silicon carbide plate specimen to examine indentation damage patterns and residual strength of the specimen. After the residual strength of the damaged specimen was measured by the four-point flexural test, damage patterns were observed with the scanning electron microscope. In the case that the cone crack (equivalent to elastic damage) was the fracture origin, the residual strength was evaluated. A method of approximate analysis of cone crack taking account of mechanism of stable crack growth was proposed. The estimated values were almost in agreement with the measured values.

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Since plastic deformations occur in contact between silicon nitride sphere and plate, the elastic/plastic stress analysis is required to evaluate the residual strength of ceramics, surface of which is damaged due to the sphere indentation. For the purpose of evaluating elastic/plastic sphere indentation damages and residual strength of ceramics, an approximate analysis of elastic/plastic contact deformation in ceramics was carried out. The elastic/plastic internal stresses of the ceramic plate were also analysed by using the finite element method. Reasonable correlation between the maximum residual stress caused at surface in the tangential direction due to sphere indentation and the residual strength was obtained.

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The method for measuring static pressure distribution between two bodies in contact is investigated by applying the electrodeposited copper foil with pyramidal micro projections. Namely, inserting the foil into contact surfaces of the elements, the depencency of the deformation of micro projectins on the magnitude of static pressure is examined by a laser microscpe. On the basis of the results obtained, the relationship between the real contact area of the foil A_r to the elements and the magnitude of static pressure is formulated. The pressure distribution occurred between the circular cylinder made of carbon steel and the brass with flat surface and that between steel and steel compressed each other was determined by A_r measured and this formula and the accuracy of this method was examined.

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We have developed the scanning type laser photoelastic apparatus that possesses high detection sensitivity for measuring the small optical retardation induced by stress. Optical birefringence is measured by a high-frequency modulation method using a photoelastic modulator and polarized laser. A modified synthesized method was developed and applied for the measurement of stress distributions of a glass plate. The distributions of the differences of principal stresses and their directions were obtained directly by a modified synthesized method. The stress distributions of pulled rectangular glass plates with a hole or semicircular notches were measured. The distributions of stress components τ_xy, σ_xx and σ_yy were calculated by the shear difference method. In order to verify the accuracy of results, we analyzed the same problems by finite element method. The stress distributions of τ_xy, σ_xx and σ_yy by the shear difference method agreed well with the analytical results of finite element method. The stress at many points could be obtained quickly by the synthesized method and scanning stress distribution measurement was realized.

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In this study, first, tensile and creep tests were carried out on two solders, 63 Sn-37 Pb and 95 Pb-5 Sn, to determine their mechanical properties. Using the measured properties, constitutive equations for the solders based on elasticity and creep were formulated. Next, an elastic-creep finite element analysis was performed on solder joint structures under thermal cycle. The solder joint structure consisted of a Si chip and a Cu plate with either 63 Sn-37 Pb or 95 Pb-5 Sn solder. The validity of the analysis was verified by the experiment using a diffused type strain gauge formed on the Si chip. The analytical results of the thermal stress on the Si chip were in good agreement with the experimental results. The analytical results showed that most of the creep strain in the solder joints occurred during the temperature change, the temperature change time hardly affected the creep strain range in solder joints, and the creep strain range for 95 Pb-5 Sn solder was higher than that for 63 Sn-37 Pb solder.

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Optimum process design of the wire ball bonding in high density LSI packaging requires information concerning with the outer profile change of the wire ball and interface condition between the wire ball and the electrode terminal pad. In the present investigation, some physial simulations of the wire ball bonding processes using the capillary tools of four different types were carried out to determine optimum tip configuration of the capillary tool. Enlarged plane strain deformation models of the wire ball and terminal pad made of aluminum and the enlarged capillary tool models made of SKD61 were employed in the physical simulations. Then, non steady-state deformation of the wire ball in the bonding process could be analyzed quantitatively in terms of the outer profile, metal flow and flow velocity, effective strain rate and effective strain. The surface conditions of the wire ball compressed on the terminal pad were also inspected quantitatively in conjunction with the slip bands formation for solid phase bonding. Referring. to the above simulation results, optimum bonding tool configuraion having some advantages for the wire ball bonding in narrow terminal pad space could be obtained successfully.

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Strength of welded T-joint of rectangular hollow section member of unequal width were studied under in plane and out of plane bending conditions. Rigid plastic model were used to get flange collapse moment. The solutions were checked by FEM, in various branch size, shape and thickness of chord tube web, and they were modified. The modified solutions were compared with the experiment of welded T-joint of 6063-T5 aluminum extrusions and good agreement were obtained.

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Changes in surface roughness and three-dimensional microscopic shapes of contact surface of polycrystalline copper during plane strain compressive plastic deformation are studied. The roughening of contact surface is measured with a stylus instrument. The microscopic change in surface shape is also observed with a scanning electron microscope. The roughness of contact surface measured in the free direction is larger than that measured in the constrained direction for the specimen having transverse contact surface. Meanwhile, the roughness of contact surface measured in the loading direction of the specimen having longitudinal contact surface is a little larger than that measured in the free direction. From the observation by a scanning electron microscope, it is seen that the mountains and the valleys which appear on the free surface are sharp, while those on the contact surface are relatively rounded.

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A method of numerical simulation for hot caliber rolling is proposed, in which deformation of a material is analyzed in an ordinary manner by three-dimensional rigid-plastic FEM, while temperature distribution in the material is calculated using a new combined method of three-dimensional FEM, two-dimensional FEM and one-dimensional FDM. Moreover, residual stress of the material is analyzed by conventional two-dimensional elastic-plastic FEM. First, the calculated residual stress distributions due to the thermal stress distributions are found to agree well with experimental ones. Next, the method is applied to a simulation of the deformation and temperature in an actual H-shape rolling process, in which a H-shape is produced from a beam blank after 20 passes and strain and temperature distributions in cross sections are obtained. The calculated shape and temperature of the material are found to agree well with measured ones.

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This paper deals with the identification of material parameters in constitutive models of cyclic plasticity for sheet metals using the bending moment vs. curvature diagrams obtained by cyclic bending tests. After a brief discussion on the identification for some simple plasticity models, a new identification method based on the iterative multipoint approximation concept is presented for complicated elastic-plastic consititutive models incorporating many numbers of material parameters. As an example, eight material parameters in Chaboche-Rosselier's model were identified by this method. This approach has been verified by comparing the simulated stress-strain curve using the constitutive model incorporating the identified material parameters with the experimental curve determined by uniaxial tension.

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This paper presents a new scheme for the evaluation of the hypersingular and regularized boundary integral equations for the boundary potential gradients. In the process of taking the limit of the exterior collocation point to an arbitrary point on the boundary, no interpolation function is employed and continuity of the potential gradients at the collocation point is taken into account strictly. The regularized boundary integral equation for the boundary potential gradients is also derived and applicability of the conventional C⁰ elements to the discretization of the hypersingular and regularized boundary integral equations is discussed. A new interpolation scheme that satisfies the C¹ continuity of the potential at any point on the boundary is presented for the potential and the flux, and is effectiveness is demonstrated through a numerical example.

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The boundary element method requires only discretization on the boundary but memory capacity equivalent to the square of total degrees of freedom and computation time in proportion to the cube of total degrees of freedom. For a large scale problem, because much time is consumed by communication between the main computer and the external memory device, the elapsed time is much greater than the CPU time. With the aim of reducing the time, the authors propose herein a new method called "diagonal escalation method" which allows solving simultaneous linear equations with about 1/4 of memory capacity that is normally required. The authors also explored the possibility of using the present method to optimize the solution of contact problems and eigenvalue problems, and cited examples of computations that demonstrate the present method's efficacy.

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Neck propagation of polymeric materials under tension is a characteristic feature which can be physically explained by the deformation induced evolution of molecular chain structure. In this study, atomic force microscope is applied to glassy polymer with tensile deformation to observe the hierarchical structures at successive molecular to macrolevels, and to clarify the quantitative relation between micro- and macroscopic deformation behaviors. First, hierarchical structure of fibrillar morphology on drawn amorphous polycarbonate film were observed : microfibril structure with a diameter between 5 and 7μm ; that with a diameter between 1 and 2.5 μm ; nanofibrils with a diameter of around 100 nm ; and regular chain pattern corresponding to the crystalline packing. Second, microscopic lattice pattern marked on surface of the specimen was employed to investigate the relation between micro- and macroscopic deformation behaviors. Macroscopic deformation and orientation of microfibril structure were quantitatively measured around the neck, which revealed that the rotation of the aligned microfibril structures were behind to that of the principal direction of plastic stretch due to shear strain by necking.

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The elastic nonlinear behavior of imperfect circular cylindrical shells under axially compression has been investigated using nonlinear Ritz analysis. It has been shown that one half-wave mode dominates in the incremental deflection mode at the critical equilibrium state associated with the lowest buckling loads due to relatively large imperfections. As deformation increases, the originally positive contribution from membrane energy is rapidly reduced eventually becoming negative energy. The present lower bound from nonlinear buckling analysis has been in good agreement with the estimation of the reduced stiffness method which provides a simple but safe extension to classical bifurcation analysis for the design of even axially compressed cylinders.

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In order to clarify the effect of grain orientation on cavitation erosion, vibratory tests were carried out on cast and forged austenitic-ferritic duplex stainless steel. The duplex stainless steel was eroded locally at a faster rate than the ordinary austenitic, ferritic and martensitic stainless steels. The localized erosion is due to the grain orientation which affects the erosion resistance for individual grain. The shortest incubation period and the highest erosion rate in steady state period are obtained in grains of {100} orientation, and the lowest erosion rate is in those of {110} orientation. Microcracks grow parallel to the original surface for the former and grow vertically or at an angle for the latter. From the mechanical viewpoint, the material removal occurs more easily for the former. It was concluded the effect of grain orientation on cavitation erosion can be explained in terms of the slip plane and the related crack growth.

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A study is made for interfacial delaminations between dissimilar materials in LSI plastic packages caused by temperature cyclic loading. Combining a thermoelastic finite element method for nonlinear contact problems and linear fracture mechanics approach, stress intensity factors at the tips of growing delaminations are obtained for the packages with Cu alloy or 42 alloy (Fe-42%Ni) leadframe. The tendency of delamination growth are compared for the two configurations of delamination ; one along the interfaces between the top surface of the die pad and die-bonding layer and the other along those between the bottom surface of the die-pad and encapsulant resin. It is concluded that the former case is more likely to occur for the package with Cu alloy leadframe while for packages with 42 alloy leadframe, the latter case is more likely to occur.

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The static and dynamic molecular structure analyses of the collagen microfibril were carried out by using the molecular mechanics (MM) and molecular dynamics (MD) simulation code, AMBER, which has been developed by Kollman et al. In this study, the characterization of collagen microfibril was performed by studying the difference between the formation process collagen (bonding model) and resolution process collagen (off-bonding model). The collagen microfibril was modeled by assembling collagen monomers, named Smith-Collagen. The formation and resolution mechanism is studied by MM and MD analyses in cases of peptide bonding and off-bonding between GLY 226-PRO 227 (Atom 1622 Atom 1623) of collagen molecule. The molecular mechanics analysis demonstrates that bonding model might be more stable as a whole and more active locally than off-bonding model. Further, the isothermal compressibility of off-bonding model is lower than bonding one. It means that the resolution of collagen molecule, which corresponds to the off-bonding, cause the higher rigidity and lose the activation ability. The molecular dynamics analysis reveals that the bonding model has the higher possibility of large scale structure change, especially at the biding part- the terminates between collagen units-. The microscale evaluations of static and dynamic micromechanical properties shows the stable and high dynamical function of the native bone structure.

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A combination of penning discharge micro sputtering techniques and non destructive replication method have been applied for etching an austenitic stainless steel SUS 316 H after creep and rupture testing. The micro-sputtering produced clear and reproducible microstructures so that grain boundaries, creep voids, carbides and σ phase precipitates were readily characterized. The replica taken from the specimen surface after micro-sputtering were observed by optical and scanning electron microscopes. Several factors during replica sampling such as an adherence between replica film and specimen surface, expansion and contraction of the film and so on, which can affect a quality of resulting microstructures, were examined and the sampling procedures were improved. Optimizing the conditions of replica sampling, clear microstructures as good as those by conventional chemical etching were obtained and the A parameter and area fraction of creep voids were quantitatively evaluated for analysis of microstructural degradation during creep.

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In general, inverse problems related to scientific measurements are ill-posed due to lack of sufficient amount of measured data or due to measurement errors, and an inverse solution is commonly obtained by the minimization procedure for a pertinent functional with various regularization techniques. In this study, a new regularization method based on the sub-band decomposition by orthogonal discrete wavelet transform is proposed for inverse scattering problem. The data representing the distribution of the unknown parameters are decomposed by orthogonal wavelets into components of different spatial scale, and regularization parameters are chosen separately for different components. When some a priori information regarding size and location of the scatterer are available, erroneous components with smaller scale can be damped with higher penalty number while retaining essential information of the scatterers. To demonstrate the validity of the proposed method, the results of the present inverse analysis with wavelet decomposition are compared to those obtained with ordinary inverse analysis for an inverse scattering problem associated with the two-dimensional scalar Helmholtz wave equation linearized by Born approximation.

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This paper describes an application of the neural networks to defect identification with laser ultrasonics. The present method consists of three subprocesses. First, sample data of identification parameters vs. dynamic responses of displacements at several monitoring points on surface are calculated using the dynamic finite element method. Second, the back-propagation neural network is trained using the sample data. Finally, the well trained network is utilized for defect identification. This method is applied to the identification of a surface defect hidden in solid with laser ultrasonics. Its performance in accuracy and robustness is quantitatively verified in detail through both numerical simulations and experiments.

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FRP tubes exhibit high energy absorption performances under axial compressive loads. In practical usage as energy absorption components in the automotive industry, application of the composite tube to bumper beams of automobiles is considered. Thus, it is important to determine what happens when a collision occurs in the off-axial direction of the tube. In this study, impacts tests were carried out to estimate the energy absorption capabilities in the off-axial directions of the composite tube, static and impact tests were carried out. As the inclination of the tube increase, specific energy absorption value decreases. By observating aspects of cross sections of the crushed tube, it was clear that a few kinds of fracture modes were generated in the circumference of the tube. Moreover, an attempt to quantitatively evaluate energy absorption mechanism on the basis of each fracture mode was made.

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For horizontal magnetization to the surface of a specimen, two large magnetic domains occur in the area of a crack due to the detection of the vertical component of the leakage magnetic field using a MO film. This leads to a lower density of the domain walls in the crack area in comparison with the no crack area. Considering that the intensity of the incident or the reflected light is affected when it passes through a domain wall, the optical permeability changes in the area of the crack. The use of a laser as a light source allows to perform a remote sensing by detecting of a brighter area corresponding to a crack and a darker area corresponding to its surroundings which is based on the behavior of the optical permeability. This paper introduces a novel NDI method using a MO film and a laser, which allows to detect cracks far away from the specimen. The method utilizes AC and DC magnetization and variation of the domain wall density and optical permeability inside the MO film.

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Completely reversed push-pull, tensile and compressive fatigue tests were performed on bovine bone under various stress frequencies to investigate an effect of stress ratio, R on a relationship between fatigue lives N_f and stress frequencies, f. Fatigue lives N_f under a constant stress amplitude in the reversed push-pull fatigue tests showed an independence of stress frequencies employed. On the other hand, fatigue lives in the tensile and compressive fatigue tests increased with an increase of stress frequency. So, it was clarified that the N_f vs. f relation of bovine bone was strongly affected by stress ratio. A viscoelastic feature of wet bone and a cyclic deformation behavior of bone specimen during a fatigue process are major factors which are concened with the above effect of stress ratio in the N_f-f relation.

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