In the present study, each member of a framed structure is subdivided with two linear Timoshenko beam elements at both ends and a cubic beam element based on Bernoulli-Euler hypothesis at the center. The adaptively shifted integration (ASI) technique is used only in the linear Timoshenko beam elements, The proposed model is applied to the explicit finite element analysis of crushing behavlors of impulsively loaded framed structures considering the effect of large deformation by the updated Largranglan formulation. Several numerical studies have been carried out in order to show the validity of the proposed numerical technique.

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Although the necessity of sensitivity analysis for frictional contact problems arises from many engineering fields, the research works have been rarely reported due to the complexity of the problems. In this paper, a sensitivity analysis approach for frictional contact problems with large deformation is presented. The continuum mechanics based formulation is carried out first and then a diseretized form is derived. The stick state is modeled by introducing a penalty type constraint. The unbalance force due to the variation of design parameters is evaluated numerically in the present sensitivity analysis method, thus the related routine of an existing FEM code can be utilized without paying an attention to the employed friction law. A couple of numerical examples including a realistic leaf spring problem are given to demonstrate the effectiveness of the proposed approach.

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In a previous paper, considering the reflection energy of SH waves from a gradient inhomogeneous layer, we offered a new rationalized layer element for a two-dimensional elastic analysis. We confirmed that the reflectance is exactly estimated using this new elements without any complexities. In this paper, we expanded this analysis to the case of a layer with an arbitrary distribution of the acoustic impedance. As an example, when the acoustic impedance and the phase velocity vary sinusoidally with the thickness, and the mass density is constant through the layer, the ressiting reflectance is in very close agreement with the exact value, and shows rapid convergence properties. Furthermore, it is shown that the existence of the maximum value of the acoustic impedance in the layer gives rise to the total rellection, even if the acoustic impedance values of the refected and transmitted side of the layer are equal.

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The "Statistical Design Support System"produces a new practical optimal design method. It can be used even on nonlinear behavior. The optimization can be done with this system using a small number of calculation results. Therefore, the effect is especially significant when it is applied to a problem that needs large-scale calculation. The authors applied it to the optimization of design paraneters of the occupant restraint system, and have tried to reduce the injury criteria of occupants based on the crash simulation. According to the improvement of interest and technology on vehicle safety. many countries has declared new safety assessments that are more severe than used one. In order to meet them all, it will be needed to consider some different crash situations simultaneously when vehicle safety equipment is designed. The authors made optimal design with consideration of different conditions of collision. This paper draws attention to the effectivity analysis and optimization.

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The concept of vehicle specific gravity has been employed as an indicator for measuring the progress achieved in reducing the weight of transportation equipment. In this paper, to estimate the vehicle specific gravity for 1997 Japanese midsize and compact passenger car, the weight percents of the 22 materials making up the 1997 car are estimated by not only approximate function analysis based on the method of least squares and weight percents of the 22 materials making up from the 1973 to the 1992 cars, but also the trend analysis peculiar to the domestic passenger car. The results show that the weighted average of coefficient of relative correlation depending on 22 approximate functions is 0.96 and the error between an estimated and actual vehicle specific gravity is about 1.3 percent.

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In case of the substantial weight reduction of a passenger car, it is inevitable to reduce the weight of its body structure to a great extent. As the body structure has been rationalized by using computer alded engineering to a considerable extent, it will be necessary to switch the body material from steel to lightweight material. Aluminum, a typical one of the lightweight materials, having been said most suitable alternative, it hasn't been recognized to be one because of its economics. In this paper ; we show numerically that partial aluminumization of the steel body to 2% extent of the proposed vehicle weight is superior to steel one in customer satisfactory efficiency through the extensive use of Data Envelopment Analysis.

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A thermal spraying process is useful to coat on substrates without any thermal damages. Therefore, it is possible to coat the high melting-point material, such as steels on the low melting point material, such as aluminum. However. it is generally difficult to improve the adherent strength between dissimilar materials. Because the stress concentration due to the material heterogeneity arises at the edge of coating interface. In this study, stress singularities at the intersection of free surfaces and the interface between steels and aluminum were investigated. It made clear that the no free-edge stress singularities existed below an apex angle of θ=20∼30°and between angles of about θ=90°and 150°. In the four-point bending test for the thermal sprayed aluminum with carbon steel and 13% chromium stainless steel, it was confirmed that the good adherent strength could be observed in order of θ=90°< 120°< 150°in case of no free-edge stress singulalities. This tendency of adherent strength was good agreement with the stress states around the edge of coating interface that were obtained by finite element analysis.

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This paper describes strength evaluation of Al₂O₃/SUS 304 joints subjected to interlaminer shear at elevated temperatures. The jig developed enables us to evaluate shear strengths of ceramics/metal joints at elevated temperatures. The shear strengths of them decrease with increasing temperature. The crack generally initiates at the upper and lower sides of the interface, a brazing filler. It grows into Al₂O₃ after stable growth and becomes unstable till 873 K (I C type fracture). The crack propagates along the interface till unstable fracture from 1 173 K (II type fracture). The crack behavior shows a mixed mode of I C and II types at 973 K and 1 073 K (IC+II type fracture). Larson Miller Parameter is valid for creep rapture tests under shear loading. The fracture modes are the I C type under the condition of low temperature and short time and the II type under the long-term condition.

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Because of their high specific strength and stiffness, fiber-reinforced plastics have been used as structural members in various fields, and hence analysis of thin laminated structures is important. In this paper, the problem of dynamic stability of cross-ply laminated cylindrical shells under impact external pressure is described. First of all. the motion of cylindrical shells under impact external pressure is defined as axially symmetric motion. Following this definition, certain perturbations are superimposed on this motion and their effect on the behavior of the shell is investigated. The symmetric state of motion of the shell is called stable if the perturbations remind bounded. The solutions for the prebuckling motion and the perturbed motion are obtained using the Galerkin's method. Stable regions are examined by utilizing the Mathieu's equation. The inevitability of dynamically unstable behaviors is proved analytically and the effects of various factors, such as external pressure ratio, number of layers, lamination constitution, dynamic unstable mode and dimensions of the cylinder, are clarified.

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Dynamic fracture behavior of PMMA was studied using the method of caustics in combination with a Cranz-Schardin high-speed camera. Single-edge-cracked tensile specimens were fractured under pin-loading conditions so that cracks could undergo acceleration and deceleration stages in one fracture event. To study the effect of the loading positions, dynamic stress intensity factor K_ID, crack velocity a and load P applied to the specimens were determined in the course of crack propagation. Unloading rate P, time derivative of P, was also evaluated to correlate with the time histories of K_ID and a.

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The previous monotonic compressive loading tests for high-density polymers including polyethylene, revealed that the inelastic deformation behavior of these engineering plastics is remarkably rate dependent at room temperature. The viscoplastic constitutive theory based on overstress had reproduced such deformation of the polymers successfully. In this study the overstress model is applied to analyze the creep behavior of polyethylene beams at 25°C subjected to a linearly increasing moment which is subsequently held constant. The numerical experiments show the significant loading rate effects, illustrating that the stress distribution at the moment increase depends on the moment rate. Such rate effects disappear with time when stresses are redistributed and reach equilibrium stress curve. In order to verify the numerical results, four-point bending tests are performed for polyethylene beams and the time-histories of curvatures obtained experimentally from surface-strain measurements show a fairly good correspondence with the numerical results.

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The time dependent-fatigue property of recycled fiber-reinforced PEEK was investigated. In particular, the influences of loading rate and recycling on this fatigue property of PEEK material were experimentally examined from a mesoscopic point of view. It was found that the fatigue propertiss of PEEK materials were dependent on loading rate and recycling. and the fracture mechanism showed creep behavior in the case of lower loading rate and recycled material. The fatigue fracture mechanisms of PEEK materials were divided into the following four types. Type I : Creep Thermal Fatigue Damage ; Type II : Creep-Mechanical Fatigue Damage ; Type III : Thermal Fatigue Damage ; Type IV : Mechanical Fatigue Damage.

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The influences of recycling process on fatigue crack propagation property have been studied for PEEK (poly-ether-ether-keton) resin materials and PA 66 (poly-amid 66) resin materials, and also the fracture mechanisms have been analyzed for their reliability. Main results were as follows : (1) The resistance against the crack propagation of recycled PEEK materials were equal to that of virgin material. On the other hand, the resistance of recycled PA 66 materials were lower than that of virgin material. (2) Examination of the fracture surface by scanning electron microscopy (SEM) revealed that the pattern of fracture surface of recycled PEEK materials were equal to that of virgin material, but that of recycled PA 66 materials were not equal to it. It revealed the existence of parabola pattern on the fracture surface. This parabola pattern was increased in its number and became small with increasing of the recycling number. (3) Examination by SEM revealed the existence of a void that diameter was about 3∼5μm in a parabola pattern. The starting point of these cracks were these voids and cracks initiated from these voids. (4) Recycled PA 66 materials were became brittle by recycling process. This is because that molecular weight of PA 66 material was decreased with increasing of recycling process number, besides, the moisture absorption rate of PA 66 material was increased during recycling process.

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Contour Induction Hardening Method has been in the limelight as a new possible case hardening method that causes considerably small distortion and high compressive residual stress. Recently, automobile and other companies are actively engaging in the research of gear surface improvement, such as higher compressive residual stress and hardness by refurbishing the Shot Peening Method. Under these circumstances, our researchers applied the compound surface refining method to gears using both the Contour Induction Hardening Method and the Double Shot Peening Method and conducted a research of modified surface characteristics and fatigue strength. The results showed that the fatigue strength of gears processed by the compound surface refining method achieved 36% better than that of the gears processed only by the Contour Induction Hardening Method.

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A study was conducted to evaluate the crack propagation behavior in a surface cracked pipe at elevated temperatures. The fatigue and creep-fatigue crack propagation tests were carried out for 316FR steel pipe (base metal pipe and weldment pipe) under four point bending at 650°C. Fracture mechanics parameters. fatigue J-integral range (ΔJ_j) and creep J-integral range (ΔJ_c), were estimated by the simplified analysis method based on the reference stress approach. The estimated crack propagation behavior was compared with the experimental results. It was confirmed that the proposed method in this paper gave a good estimate.

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Rotating bending fatigue tests were performed for Inconel 718 at room temperature and elevated temperatures of 300°C, 500°C and 600°C to investigate the influence of temperature on the fatigue crack initlation and its propagation. Although the propagation of a micro-crack smaller than about 20 μm is suppressed at elevated temperatures, that of the larger-crack is accelerated inversely. These results were discussed from the viewpoints of the softening of matrix and the oxidation of surface caused by the high temperature.

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A crack in a structural member can change the eigenfrequencies of the undamaged structure. The magnitude of change in the eigenfrequencies is a function of the depth and the location of the crack. By relating the eigenfrequencies to the crack location and depth, we proposed a crack identification method for plane frame structures in present paper. In the FEM vibration analysis for the structures, the crack is simulated by an equivalent rotational spring, connecting the two segments of the beam. The matrix elements containing a crack are derived explicitly by combining both the transfer matrix method and the compatibility equation of each segment. The eigenfrequencies computed by FEM are then applied to studying the inverse problem-identification of crack location from frequency measurements. And the crack identification method is performed by using both the finlte element method and the genetic algorithm. In order to confirm the validity of the proposed method, several frame structures with a crack are analyzed.

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A pair of integral equations are derived for a non-uniformly pressurized vertical planar crack of arbitrary shape in a fluid-saturated, poroelastic, infinite space of transversely isotropic permeabillty by using the fundamental solutions obtained in a previous paper and the concept of a dislocation segment. The transverse isotropy with its axis being vertical is a more realistic model for oil/gas reservoirs. The equations obtained relate normal tractions and fluid pressure on the crack faces to crack opening gradients and fluid injection rate per unit fracture area and include the known solutions for the isotropic case and for the case of zero permeability in one direction as limiting cases. These integral equations are intended to be implanted in a 3D hydraulic fracturing simulator.

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This paper presents a method of measuring a strain tensor on a plain surface and identifying the principal axes related to the plastic anisotropy. We have proposed an optical measuring system using a laser speckle which is an interfering image of the reflected light arised from applying a narrow laser beam to a specimen surface. The strain is estimated by the movement of the speckle image. To estimate the movement, we have proposed some ideas including the cross correlation function method. The measurement of three independent strains gives us to determine a plastic 2-dimensional strain tensor contained a shear strain. Finally, a plastic anisotropy of sheet metals is investigated.

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It was evaluated creep damage by Electromagnetic Acoustic Resonance (EMAR), Noise Energy Method and Supersonic Spectroscopy (First Moment) Method on SUS 304 fabricated by Hot Isostatic Press (HIF) at 1050°C. Attenuation coefficient of electromagnetically excited acoustic wave in HIP has been investigated with frequency between 1.1 MHz and 5.4 MHz. Attenuation coefficient of the shear wave of as low as 2.5×10^-4/μs at 1.1 MHz has been detected by reducing diffraction loss and the loss due to transmission of the ultrasonic wave to the electromagnetic acoustic transducer through the mechanical contact. The attenuation coefficient increases in proportion with frequency up to 5.4 MHz on the samples (specimen) fabricated with the pressure of 170 MPa. On the other hand, on the samples (specimen) fabricated with pressure lower than 80 MPa, the attenuation coefficient increases rapidly above 4 MHz. The void area fraction has been found to increase as the pressure decreases, which may be responsible for the rapid increment of the ultrasonic attenuation of the samples (specimen) fabricated with pressure lower than 80 MPa. As a result, it was clear that EMAR is more sensitive one to detect creep voids than the other methods. So We hope it is possible to use the actual facilitles in future.

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The method of caustics has been applied to evaluate normal and tangential forces under diskto disk contact such as in rolling contact fatigue. In this paper, reflection-type caustic images are newly used to generalize the method of caustics. Two caustic images-a cusp-like image formed from the front face and a semi-circle image formed from the back face-were utilized to the evaluation, because they are formed simultaneously. A computer simulation program for the caustic images was coded through theoretical considerations. The simulated caustic images corresponded with experimental caustic images formed from a PMMA disk contacting a steel disk. The experimental formula that expressed using the specific sizes of caustic images has been proposed for obtaining normal and tangential forces. This formula is applicable to Hertzian contact problems, gear face contacts, roller bearings. etc.

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The hillock growth mechanism at the surface of Pt/TiN electrode is investigated. Transmission electron microscopy shows that the hillock forms from delamination at the interface of Pt/TiN and plastic deformation of Pt film. Stress measurement in a Pt film shows that the hillock growth starts when the internal stress in a Pt film exceeds about -1 GPa during high-temperature annealing. Since the stress in Pt film varies with deposition temperature from 500 MPa to -500 MPa, starting temperature of the hillock growth depends on the deposition temperature. Therefore, the stress control of Pt film is very important in order to eliminate hillock growth at the electrode surface.

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This paper is concerned with an biaxial bending compressive experiment for the case of different eccerentricities at the upper and lower ends of carbon steel square pipes in a short column range, supported by a spherical seats. It was found that collapse of the pipes occurred as the local buckling of the flat walls by the side of eccentric and the stress decreased as the eccentric ratio increased. Consideration has been given to the formula for the buckling stress which is the combination of the analysis based on the energy method with the experimental result. The measurement results show that the calculated value by this formula is in good agreement with those obtained experimentally for the short column range.

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Cold upsetting of a circular cylinder is often used to evaluate the cold forgeability of forming materials. The index of the forgeability is the critical strain where a crack occurs on the expanding free surface of the upsetting cylinder. Occurrence of cracking is associated with the multiplicity of solution from a view point of the mechanics of plasiticity. In general, it would be believed that the multiplicity corresponds to plastic instability. But plastic instability does not necessarily cover all over the multiplicity, but load instability must be taken into consideration. To the evaluation of cracking the criterion of load instability is applied which appears after plastic instability in upsetting. The mode of cracking must be consistent with deformation required on elasto-plastic boundary. Hence, only two kinds of mode are permitted. The strain rate at load instability can determine which mode of the two is realized on cracking, by comparing the energy consumption from load instability to the contraction of plastic region into a plane region. Loading path in nominal stress rate space is used which makes it easy to specify plastic and load instabilities. Strain data developing on the expanding surface is determined with reasonable accuracy using commercial software MARC. It is shown that the criterion of load instability is useful for the prediction of the surface cracking.

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