The rubbers containing various kinds of fillers exhibit fabulous mechanical characteristic and therefore, they are widely used in various production. Owing to the wide range of controllability in mechanical characteristics by adding the coupling agent, silica-filled rubber draws attention for extensive usage. Here, to clarify the mechanism of the marked increase in deformation resistance in silica-filled rubber in detail, we will construct the finite element homogenization models of silica-filled rubber. These models can reflect various experimental observations that include changes in microscopic structural characteristics such as distribution morphology of silica particles, the thickness of the interfacial phase between silica and rubber, and the networklike gel structures developed from the interfacial phase. The obtained results clarified the essential physical enhancement mechanisms of deformation resistance and hysteresis loss, i.e., the Mullins effect, for rubber filled with silica. The volume fraction of the silica coupling agent essentially affects the deformation behavior of silica-filled rubber suggesting the high controllability of the material characteristics of silica-filled rubber compared with carbon-black- filled rubber. Although, the present model underestimates the hysteresis loss as compared with the experimental results, it has a capability to evaluate the effect of adding coupling agents on the fundamental deformation behavior of silica filled rubber.

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The thermo-electro-mechanical fracture problem of an infinite piezoelectric material containing a T-shaped crack is considered in this study. The problem is solved for an infinite piezoelectric material that is under a uniform heat flow, uniform mechanical loads in two directions and a uniform electric load far away from the crack region. The crack faces are supposed to be completely insulated. By using the Fourier transform, the thermal and electromechanical problems are reduced to systems of singular integral equations, respectively. The singular integral equations are solved numerically. Numerical calculations are carried out, and detailed results are presented to illustrate the influence of the thermo-electro-mechanical interaction on the stress and electric displacement intensity factors.

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In this paper, we derive the general solutions for many cylindrical holes or rigid inclusions perfectly bonded to an elastic medium(matrix) of infinite extent, under In-Plane deformation. These many holes or rigid inclusions have different radii and different central points. The matrix is subjected to arbitrary loading like uniform stresses at infinity. The solution is obtained, via iterations of Möbius transformation as a series with an explicit general term involving the complex potential functions of the corresponding homogeneous problem. This procedure has been termed ”heterogenization”. Using these solutions, several numerical examples are shown by the graphical representation.

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In this paper, the crushing behavior of cylindrical conic absorber with corrugated surface subjected to axial compressive loading is studied by using finite element method. The role of corrugation is to control the deformation pattern and to decrease the fluctuation in the load-displacement curve. The effect of taper is to increase the crushing span. The deformation mode for taper corrugated circular tubes can be classified into progressive crush mode, in which compressive force fluctuates with the wrinkles forming one after another, and simultaneous crush mode, in which compressive force increases uniformly. A mode classification chart is produced for various combinations of wavelength, wave-altitude and taper angle. The cone with corrugated surface is superior to the cylinder with corrugated surface for energy absorption rate.

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In welded structures, it is indispensable to evaluate welding residual stresses for assurance of structural integrity. Today, several nondestructive evaluation methods of residual stresses have been proposed, however measured results can not be applied to the FEM (Finite Element Method) analysis. For the FEM applications, all the 6 components of stresses in the whole structure must be estimated and those solutions should satisfy the self-equilibrium condition. From this view point, authors have proposed the bead flush method. In this method, welding residual stresses are calculated nondestructively by a simple elastic FEM analysis from eigen-strains which are estimated by the inverse analysis from released strains during removal of reinforcement of the weld. By now, the effectiveness of this method has been proved for welded plates and pipes with relatively high bead height. As decreasing bead height down to below one mm level, however, it is difficult to satisfy both high accuracy and stability because of higher effect of measurement error. In this study, to obtain multiple residual stress distribution from a single measurement, released raw strain data were pre-treated in consideration of a prior knowledge before conducting the inverse analysis.

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To assure structural integrity for operating welded plants, it is required to evaluate welding residual stresses without crippling the functions of the parts. As a nondestructive method, the bead flush method has been proposed. By applying this method, all the 6 stress components that satisfy the self-equilibrium condition in whole structure can be computed, since solutions are calculated by the FEM analysis from eigen-strains that are estimated from released strains during removal of reinforcement of the weld. In the previous report, a new approach to apply this method to welded pipes with relatively low height of reinforcement was proposed. In there, released raw strain data were pre-treated in consideration of a prior knowledge before conducting the inverse analysis. In this study, to improve statistical estimation accuracy, the L-curve method and the artificial noise method are introduced as well as “the truncated singular value decomposition method”. By using these methods, it is shown stable solutions of multiple residual stress distributions can be obtained from a single measurement of released elastic strains.

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The subloading surface model was extended so as to describe the cyclic loading behavior pertinently and, based on this model, the constitutive equation of metals was formulated in Part 1. The calculated results by the present model are compared with various cyclic test data for stress and strain amplitudes with one-side and both sides of tension and compression and the circular stress path. Then, it is verified that the present model does not require to incorporate the algorithms for the yield judgment and the pull back of the stress to the yield surface and has the high ability to predict the cyclic loading behavior of metals by introducing the tangential-inelastic strain rate and the stagnation concept of isotropic hardening.

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Magnesium (Mg) is easy to be corroded in contact with other metals due to the formation of galvanic cell at the interface because it has the lowest negative standard electrode potential (SEP) in industrial metals. The traditional methods to evaluate corrosion resistance such as saltwater immersion test, salt spray test, and electrochemical corrosion test provide the macroscopic corrosion phenomenon, not microscopic information at the local interface. It is important and necessary to clarify galvanic corrosion mechanism at the interface between α-Mg matrix and metallic dispersoids of Mg alloys. The effect of dispersoids in Mg alloys on corrosion resistance hasn't yet evaluated quantitatively as the SEP of dispersoids wasn't almost investigated. In the present study, the surface potential difference (V_SPD) at the interface between dispersoids and α-Mg of Mg-Fe cast material and AZ91D alloy was measured by using Scanning Kelvin Probe Force Microscope (SKPFM). Surface potential of pure metals measured by SKPFM had good correlation with SEP, and then V_SPD values also corresponded with the theoretical values of the difference in SEP. Salt water immersion test of AZ91D alloy was conducted to clarify the relationship between V_SPD measurements and corrosion resistance. Changes in topographic maps around the intermetallic dispersoids were investigated by using AFM before and after corrosion test, and resulted that corroded phases corresponded to the anodic phases indicated by surface potential.

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Magnesium has poor corrosion resistance because of its less noble standard electrode potential (SEP). Therefore, it is easily corroded in first when contacting with other metals having a higher SEP. For alloy development of Mg matrix composites reinforced with Ti particles, the corrosion behavior between Mg matrix and Ti dispersoids is one of very crucial phenomena. In this study, the surface potential difference (SPD) between Mg-Al alloy (AZ80) and Ti was investigated by using Scanning Kelvin Probe Force Microscope, and the corrosion resistance was evaluated with that SPD. In this experiment, two specimens were prepared. One was a joined material of AZ80 and Ti by using spark plasma sintering (SPS) process in solid state (AZ80(solid)-Ti) and the other by melting AZ80 after SPS (AZ80(liquid) -Ti). The latter specimen included the reacted layer of enriched Al at interface between AZ80 and Ti due to diffusion of Al during melting. AZ80(solid)-Ti had no reacted layer at the interface. The measured SPD between AZ80 and Ti of AZ80(solid)-Ti was about 0.62V and mostly the same to that between Mg and Fe. The pair of Mg and Fe generally shows largely poor corrosion resistance. On the other hand, the SPD between AZ80 and the layer of enriched Al was about 0.29V and smaller than that between AZ80 and Ti. The results indicated the enrichment of Al at interface between AZ80 and Ti improved corrosion resistance of Mg-Al alloy matrix composites reinforced with Ti particles. AZ80(liquid)-Ti showed superior corrosion resistance to AZ80(solid)-Ti in salt immersion test.

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Two carbon black-filled ethylene-propylene-diene-methylene linkage (EPDM) rubbers which have a different particle size were exposed to hydrogen gas; then, the critical pressures at the initiation of internal cracks (p_F) were evaluated. It was obtained that p_F = 4 - 5 MPa for two CB-filled rubbers by optical microscope observation. The p_F values were estimated in terms of fracture mechanics under the assumption that bubbles were formed in the rubber structure after decompression, and these grew with the elapsed time; consequently, cracks initiated from the stress concentration of the bubbles. When an internal pressure of the bubble (Π) was assumed to be equal to the applied hydrogen pressure (p), the p_F values were successfully estimated in terms of the critical internal pressure (Π_F), since Π_F showed good coincidence with p_F for unfilled and silica-filled rubbers. In contrast, p_F of the CB-filled rubbers was overestimated by this method, because Π_F was lager than p_F. Since the CB-filled rubbers contain carbon black as filler, much hydrogen is absorbed in the rubbers compared with the unfilled and silica-filled rubbers. Because the increase of Π originated from the absorbed hydrogen by CB was underestimated, it was inferred that p_F showed smaller than Π_F. Therefore, it was supposed that Π > p for the CB-filled rubbers, i.e., the CB-filled rubbers experienced more pressurization due to additional hydrogen.

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Torsional fatigue tests were conducted for smooth solid bars, smooth hollow cylinders, and circumferentially notched bars of carbon steel (JIS SGV410) and austenitic stainless steel (JIS SUS316L) under completely reversed cyclic torsion. The cyclic stress strain relation was first determined for two steels. The yield stress and the flow stress were higher for SUS316L than for SGV410. The torsional fatigue life of smooth solid bars was longer than that of hollow cylinders when compared at the same nominal stress amplitude. The true strain amplitude on the surface of solid bars under torsion was calculated by the elastic-plastic analysis by the finite element method (FEM). The relation between the strain amplitude on the specimen surface calculated by FEM and the fatigue life was nearly equal to the relation obtained for hollow cylinders. The crack initiation life for notched specimens was determined by the direct electrical potential method. When compared at the same nominal stress amplitude, the crack initiation life got shorter as the notches became sharper. The distribution of the amplitude of equivalent strain near the root of circumferential notches under torsion was calculated by the elastic-plastic analysis of FEM. The crack initiation life got slightly longer for sharper notches when the life was correlated to the strain amplitude at the notch root. The relation between the crack initiation life and the strain amplitude at 0.1 mm distant from the notch root was nearly unique independent of the notch shapes and was equivalent to the relation obtained for smooth specimens.

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For the stabilization of insulation performance in resin-molded insulators, strong adhesion between the resin and ceramic is required. In this paper, a new technique for the control of the interfacial strength in resin-molded structures has been proposed. The adhesive strength of the internal interface in a resin-molded structure was estimated as the interfacial fracture energy by using the molecular dynamics method. The interfacial fracture energy was qualitatively in agreement with the adhesive strength index obtained by a shear experiment. Based on the simulation results, the control of the interfacial strength was performed, and it became clear from the result that the interfacial strength between resin and ceramic can be improved up to the strength level of the glaze adhesion.

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Recently, brain injury has been mainly analyzed by computer simulation. However, simulation model of brain needed to obtain accurate analysis results has been shown variety of values. Simulation model reproduced deformational behavior of brain with velocity has not been built. We obtained relaxation curve from hemisphere indentation test for cerebral surface using our own experiment setup, and calculated shear modulus and viscosity. We built viscoelastic model of cerebral surface and evaluated effect of velocity, sites, and leptomeninx on mechanical properties. Our experiment showed that short term shear modulus with leptomeninx was approximately 1.4 times higher values than it without leptomeninx, and viscosity value in high speed range was lower than slow speed. We evinced that brain tissue depends on velocity on high speed range, and leptomeninx affects a rigidity of cerebral surface. Additionally, we confirmed that our viscoelastic model is numerically able to reproduce deformational behavior of brain on high speed range, and acquired parameter values for functions of viscoelastic model.

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This paper deals with the singular stress field at the adhesive dissimilar joint, and discusses the effect of material combination and adhesive thickness on the intensity of the singular stress when bonded strip is subjected to tension. A useful method to calculate the intensity of singular stress at the adhesive dissimilar joint is presented with focusing on the stresses at the edge calculated by finite element method. The intensities of singular stress are indicated in charts with varying adhesive thickness t under arbitrary material combinations for adhesive and adherents, and it is found that the intensity of singular stress increases with increasing the adhesive thickness t until t=W , when W is the width of adhesive. The intensity of singular stresses are also charted under arbitrary material combinations which are presented by Dundurs' parametersα , β when t/W = 0.001 and t/W = 0.1 , and it is found that for a fixed value β the intensity of singular stress increases with increasing α when α is small while it decreases with increasing α when α is large.

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This paper describes the effects of stress ratio on the ΔK_th improvment by overload. Tensile overload was applied to compact tension specimen, subsequently fatigue tests were carried out at stress ratio S= 0.1 or 0.5. And an analytical investigation of effect of stress ratio was studied. The value of ΔK_th increased with increasing of the tensile overload . And the nominal threshold values were given by the equation: Δ^NK_th^s=C + DK_ov. Where C is ΔK_th^o and D is a proportional constant and 0.26-0.28. Experimental results showed that D showed good agreement with theory. Thus, if Δ^NK_th^s is enough larger than applied K and ΔK values, crack is not able to grow and can be made harmless.

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Low carbon steel without any alloying elements which enhance the quench hardening has not been considered as a material fitting for quenching. In the present study, however, the quench strengthening was found to occur fully in the sheet of the low carbon steel after the sheet was rapidly cooled in rf induction heat quenching. This finding shows the possibility of a combined process of press forming and quenching. In this process, for example, an automobile part which is press formed severely with the steel sheet of good formability is thought to be increased in strength by the induction heat quenching performed in the suitable segments on the part.

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