Carbon-black (CB) filled rubber used as materials of tire exhibits the characteristic deformation behavior. Especially, the strength and hysteresis loss of CB filled rubber increase as against unfilled rubber. A viscoelastic constitutive equation of unfilled rubber is developed based on the reptation theory to represent these typical deformation behavior. The finite element homogenization method and developed constitutive equation provide a computational model of CB filled rubber. The computational simulation reveals the mechanism of hysteresis, the strain-rate-dependent nature and the stress relaxation of unfilled/CB filled rubber. Subsequently, it has been revealed that the significant orientation hardening and the delay of viscoelastic response due to the highly localized deformation in the rubber cause the increase of resistance to the macroscopic deformation with the CB filling and the increase strain rate. These responses of molecular chain during the deformation result the increase of the hysteresis loss under cyclic straining. Furthermore, the influence of the volume fraction of CB on deformation behavior, and the stress relaxation of CB filled rubber are discussed.

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The magnetostatic analysis is important on the corrosion detection problems and the nondestructive inspection of the structures. Boundary element method is often used to the magnetostatic analysis conventionally because boundary element method does not require the discretization of the magnetostatic field domain and has an advantage for open domain problems. However, in case of the current density should be considered as the source of the magnetostatic field, the conventional method requires not only numerical calculation of current density distribution, but requires numerical region integration of this current distribution which has been calculated at discrete sample points. These two steps of discrete numerical calculation of 3D space increases computational time and loses the accuracy. In this paper, a new boundary integral method for analyzing magnetostatic field without the calculation and the integration of current density distribution in the electrostatic field domain which obeys Laplace equation is developed. The region integration of current density distribution is reduced to the infinite region integration of the fundamental solution using the derivative of the boundary integral equation for electrical potential field. Since the analytical calculation of the infinite region integration could be achieved, the accuracy and computational time are improved. In order to demonstrate the accuracy and efficiency of the present method, some example problems are solved, and compared with the conventional method. Present method is also applied to the practical electro-plating problem.

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This paper deals with the analysis of the stress field on the periphery of a rigid inclusion or a circular void in an elastic half space subjected to rolling contact with frictional heat. The analysis is two-dimensional, the roller and the inclusion (void) are assumed to be parallel cylinders. Rolling contact is simulated as a line load with both normal and shear components, moving with constant velocity over the surface of the half space. A frictional heat input in the contact region is included to incorporate the thermal loading. The complex variable formulation of Muskhelishivili is used to reduce the problem for the inclusion or void to a Fredholm integral equation of the second kind. This integral equation is solved numerically thus enabling the numerical calculation of stress field on the periphery of an inclusion or a void in a half space. The effects of changing the frictional coefficient, slide/roll ratio and the depth of inclusion or void on the results are considered.

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In order to examine the feasibility of using wood as a plastic substitute, we studied the possibility of producing cups from wood by extrusion. It is common to use powdered wood in the same kind of studies. Whereas in this study, we didn't powdered raw materials and used wood in bulk state. The formability depended strongly on the moisture content of raw materials. We failed to obtain enough fluidity to fill a die cavity with air-dried wood specimens (moisture content : 11%). Whereas it was possible to fill the die cavity both with high moisture content wood specimens (moisture content : 25%) and water saturated wood specimens (moisture content : 90%). However, the states of molded products were quite different between the two. The cups produced from high moisture content wood specimens had cracks. On the other hand, the cups produced from water saturated wood specimens were well formed. The original fiber orientation had much influence on the deformation process and the resulting fiber orientation.

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Poly (lactic acid) /Poly (butylene succinate) (PLA/PBSU) polymer blends were fabricated to improve the fracture and biodegradable properties. Heat treatments were conducted on the specimens to improve the reduction in stiffness due to blending. The effects of heat treatment on the mechanical and fracture properties were discussed with the results of dynamic mechanical tests and fracture toughness tests, respectively. Storage modulus increased with increasing PLA contents. Heat treatments also improved the modulus because of the crystallization. The critical energy release rate, J_cr and the fracture energy, J_f, however, decreased with heat treatment. Excessive contents of PLA or PBSU significantly decreased J_cr and J_f.

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For honeycomb subjected to in-plane loading, there exist deformations in the height direction for cell walls due to effect of Poisson's ratio. Because these deformations are different for adjacent walls, the elastic modulus of honeycomb should be analyzed as a 3-dimensional problem. In this paper, the method of analysis for the equivalent elastic modulus E₁ proposed by authors in the 1st report, in which the effect of height h of the honeycomb core on the elastic modulus is taken into account, is applied to theoretical formula for calculating Young's modulus E₁ and shear modulus G₁₂. Then, the validity of the proposed theoretical formula for elastic moduli E₁ and G₁₂ is verified comparing with the numerical results by FEM.

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A new model of axial crushing of cylindrical tubes with corrugated surface is developed in which crushing force is analyzed by considering the balance of work done by the crushing force and the energy required for the tube deformation. The energy absorbed by the crushing cylindrical tube consists of the bending energy term and the membrane energy term, which results from compression or extension of a shell element in the hoop direction. It is found from analysis results of the model that two different modes, called P-mode and S-mode respectively, may exist in the collapse of cylindrical tubes with corrugated surface. In the P-mode compressive force vibrates with the wrinkles forming one after another, and in the S-mode compressive force increases uniformly. Mode classification charts, as well as the average crushing force, predicted by the developed model are found to be in good agreement with the results of numerical calculation by FEM. Also, it is found that the increase in the compressive force load for S-mode is mainly due to the increase in bending energy with deformation of tube.

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In this study, stress distributions on the interface of bonded dissimilar materials with an elastic-plastic interlayer were calculated by using the finite element method and the effect of the elastic-plastic interlayer on the free-edge stress singularity was investigated. It was found that the free-edge stress singularity varied with applied load in the elastic-plastic case. Stress distribution near the intersection of the free-surface and the interface was controlled by the free-edge stress singularity of the bonded dissimilar materials without interlayer as in the case of elastic analyses. Stress distribution near the intersection of the free-surface and the interface normalized considering the free-edge stress singularity can be expressed by a function of the distance from the edge of interface normalized by the thickness of interlayer. The normalized stress distribution can be used to estimate stress distributions for other values of interlayer thickness.

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The failure criterion examined using fracture state says that Mohr-Coulomb criterion is more appropriate to soil than Mises criterion. The important aspect which must be confirmed in the examination of the criterion is that the stress state at fracture are situated on a critical straight line in primary yield relation showing the dependency between equivalent deviatoric stress and hydrostatic pressure. Moreover, the equivalent deviatoric stress must be representative of the magnitude and shape of the yield curve on a deviatoric plane. Therefore, the critical straight line is also affected by failure criterion itself. Such mutual dependency makes it complicated to find out the relevant yield criterion. For the discussion of the yield criterion, we used the data obtained in the compression tests performed by Reades & Green and by Lade & Duncan. First, on the assumption that fracture stress points are situated on the critical line in the primary yield relation, the shape of yield curve on the deviatoric plane is examined. Then, the curve shape is represented with the relation between J₂ and J₃ where J₂ and J₃ are the second and the third invariant of deviatoric stress respectively. Second, the equivalent stress is defined using the curve shape relation. Third, it is confirmed that fracture points in primary yield relation are located on the straight line when based on the equivalent stress defined

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This paper contains an exact solution for the state of stress in an elastic circular cylinder with an oblate spheroidal cavity or an internal penny-shaped crack, the surface of which is subjected to a prescribed temperature distribution. The solution is deduced. with the aid of thermoelastic displacement potentials and Dougall's displacement potentials. Two sets of harmonic functions and two sets of biharmonic functions are given by simple expressions referring to cylindrical and oblate spheroidal coordinates. The boundary conditions on the surfaces of the cylinder and the cavity are satisfied by using the relations between the cylindrical and oblate spheroidal harmonics and biharmonics. The solution for an internal penny-shaped crack is also given by regarding as a limited case of an oblate spheroidal cavity. Numerical results for stress distributions, stress concentration factors and stress intensity factors are shown graphically.

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The loading frequency dependence of fatigue crack growth in the near-threshold region in SUS304 stainless steel was investigated using constant K_max and ΔK decreasing test method at 350°C, 550°C and 650°C in a vacuum below 2.7×10^-4Pa. Loading frequency was changed from 30 Hz to 3Hz and vice versa, and crack growth rates at f=30 Hz and 3 Hz were compared. It was found that crack growth behavior in the region below the conventional threshold value was dependent on the loading frequency. Furthermore crack growth rates per unit hour at f=30 Hz and 3 Hz were compared in order to examine the effect of oxides on the crack surfaces on crack growth behavior. It was suggested that the amount of crack growth was rather time-dependent than cycle-dependent in the region below the conventional threshold in a vacuum.

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In Molecular Dynamics (MD) simulations, interatomic potentials have significant effects on the results and calculation time, i.e. analysis sizes. In this paper, first, the crack growth behaviors in α-Fe calculated by three representative interatomic potentials, the Embedded Atom Method (EAM) potential fitted by Simonelli, G. et al., Finnis-Sinclair (FS) potential and Second Nearest-neighbor Modified EAM (MEAM) potential, are compared, and the reliability of the results obtained by the MEAM potential is confirmed based on the reproducibility of the important physical properties. Although the MEAM potential is reliable, we show that the computational time required by the MEAM potential is more than 50 times of the FS potential. Here, we propose “Hybrid Potential Method” which selectively uses different interatomic potentials according to the local atomic structure, and connects those potentials by the use of handshake method. We use FS potential, which is efficient in calculation, for bcc structure and the MEAM potential, which is accurate but time consuming, for non-bcc structures. The availability of the Hybrid Potential Method is demonstrated, and then the method is applied to crack growth simulations using large calculation models. We report the phase transformations and grain nucleation near the crack tip during crack growth.

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The damage of electronic devices is often due to the generation of heat within the components. When the current is supplied to electronic components, their temperature rises because of the fact of Joule-heating. To evaluate the reliability of components subjected to Joule-heating, it is essential to analyze the associated current density and temperature distributions in the components. In this study, two-dimensional electro-thermal problems concerned with steady current flow near the corner of a hole were treated, where the shape of the hole was assumed to be a right-angled diamond. Distribution of current density near the corner was analyzed theoretically based on the Schwarz-Christoffel transformation. Electrical potential, which was calculated from the current density analyzed, was compared with FE analysis. Temperature near the corner was analyzed based on the electrical potential calculated. For the case when the heat flux related to the gradient of the temperature field associated with the problem without Joule-heating equals to zero, the temperature near the corner was verified to remain constant although current density decreased gradually far from the corner.

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A two-stage general optimization approach is presented for generating link mechanisms from a highly connected ground structure. The structure is modeled as a pin-jointed truss, and is to be optimized so that a large displacement is generated in the specified direction at the output node. The design variables are the cross-sectional areas of the members and the nodal locations. The equilibrium path of an unstable mechanism is traced by the displacement control method. In the first step, the unnecessary members are removed by solving the optimization problem for minimizing the total structural volume under constraints on the maximum load, the displacement at the specified node, and the stiffnesses at the initial and final states. In the second step, the deviation of the displacement of the output node from the specified direction is minimized. It is shown in the numerical examples that several mechanisms can be naturally found as a result of the two-stage optimization starting from randomly selected initial solutions.

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A low-power micro semiconductor strain sensor that utilizes piezo-resistance effect was developed for measuring the strain of mechanical structures. The strain sensitive device in the sensor chip is a p-type diffused resistor formed on a single-crystalline-silicon. In order to decrease the effect of temperature fluctuation on the output of the sensor, a micro Wheatstone bridge circuit, which consists of active resistors along the [110] direction and dummy resistors along the [110] direction, is formed by using the semiconductor fabrication process. Due to this invention, the temperature dependence decreases to 0.002με/°C and thus becomes negligible for practicality. Then, a tensile test for a stainless steel plate to which the sensor is attached was carried out. The experimental result showed that the bridge circuit works correctly and the sensitivity factor (gage ratio) is approximately 52. This measured value is almost equal to the calculated sensor output value using references. Not only this high sensitivity, but also low-noise output was achieved in spite of a small circuit current. The low-noise output is the result of the micro Wheatstone bridge circuit. Thus, it is evident that the merits of the sensor are suitable for mechanical sensor-net systems.

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