In the present study, we clarify the deformation behavior of semi-crystalline polymer in microto mesoscopic region by using large deformation finite element homogenization method. The crystalline plasticity theory using a penalty method for the inextensibility constraint in the chain direction and the nonaffine molecular chain network theory were used to the representation of the deformation behavior of the crystalline and amorphous phases, respectively, in the composite microstructure of the semi-crystalline polymer. The deformation behaviors of High Density Polyethylene (HDPE) in micro- to mesoscopic region under mesoscopically uniform plane strain tension, compression and shearing were investigated. The results revealed that the microstructure of semicrystalline polymer exhibits highly anisotropic deformation behavior including strain softening or substantial hardening. Furthermore, mesoscopically localized deformation zone intersepting several grains appears in the direction of maximum shear stress due to the interactions with surroundings.

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We propose a new method of estimating the fatigue life of wire ropes of elevator. It is based on the assumption that the life of wire rope is determined by the fretting fatigue life of wires. Estimates done on a sample wire rope with the method were in good agreement with the experimental results. The method of estimation involves four steps. First, we did a finite element analysis and estimated the pressure between the wires. To take into account the behavior of the whole wire rope and each wire in the stress analysis, we did a zooming analysis. Second, we conducted a fretting fatigue test on the wires to construct a fretting fatigue database for them. Third, we estimated the life of each wire derived from the pressures between the wires and the fretting fatigue database. Last, we estimated the life of the wire ropes derived from the life of individual wires. The rope life estimated with our new method revealed some important findings. We found that : (1) the inner wires broke earlier than the outer wires and : (2) the residual strength of the wire ropes decreased rapidly after their strength became lower than 80% of their initial strength.

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A technique for generating a medial surface-which is used to transform a thin structure into a shell model-was developed. This technique has the advantage of reducing the workload in generating an analytic shell mesh for a thin-structure model. And it can automatically transform complex assembly models containing contact parts into analysis data. The technique consists of three steps : first, medial surfaces are generated in each part of an assembly model, second, jointing parts are searched, and third, tyings or shared nodes are connected with the target jointed part. Tests on magnetic-disk cover parts showed that the new technique can accurately generate the medial surface for such parts.

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In this paper, elastoplastic nonlinear behaviors of circular tubes with grooved surface subjected to axial compression are studied by using finite element method. The role of grooves is to control the deformation pattern and to decrease the fluctuation in the load displacement curve for circular tubes. It is found from our results that the deformation pattern depends on the ratio of grooved distanceλ₁ to the half wavelength of folding wrinkleλ_c for non-grooved circular tubes, as well as the grooved depth d. Moreover, the fluctuation can be decreased by introducing grooves. However, the load efficiency is not necessarily improved by the grooves, depending on the material hardening coefficient E_n.

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In this paper, elastoplastic post-buckling behavior of cylindrical tubes under axial compression is studied by using finite element method. In particular, the effects of tube geometries and strain hardening characteristics on the high strain concentration in circumferential direction ε_θ which arises at the vertex of outward wrinkles are investigated. It is found that the maximum value of ε_θ is dependent on the thickness-to-radius ratio t/R, and independent of the length-to-radius ratio L/R and the nondimensional hardening coefficient E_h/E. Moreover, based on our results we propose an approximation to evaluate the maximum strain ε_θmax by using the deformed shape of tubes. This approximation can be used to estimate the experimental results of ε_θmax with a good accuracy.

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A numerical simulation based on FEM is used to study the influence of impact velocity on the crushing behavior of cylindrical shells subjected to an axial impact. It is found that the first peak stress in an impact becomes higher with increase of impact velocity due to the inertia effects of radial direction. An empirical equation is proposed to evaluate the first peak stress. Also, it is found that the effect of impact velocity on the first peak stress depends on the strain hardening ratio E_h/E and the ratio of t/R.

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This paper examines the applicability of passive electric potential CT (computed tomography) method to the quantitative identification of three-dimensional crack in structures. In this method, piezoelectric film is glued on the surface of structures. Electric potential values on the piezoelectric film change due to the strain distribution on the surface of structures, when the structure is subjected to external load. The strain distribution induces an electric potential distribution on the piezoelectric film. Then, this method does not require electric current application, and passively observed electric potential values on piezoelectric film can be used for the crack identification. The electric potential distribution on piezoelectric film was investigated numerically and experimentally. It was found that the electric potential distribution shows the characteristic change corresponding to the shape of the surface crack. An inverse method based on the least residual method was applied to the crack identification from the electric potential distribution. In this inverse method, square sum of residuals is evaluated between the measured electric potential distributions and those computed from electric potential distribution of the piezoelectric film. Three-dimensional surface crack were identified from measured electric potential distribution. It was found that location and size of the crack can be quantitatively estimated by using two-dimensional distribution of electric potential.

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A new technique to locate a defect, combining acoustic emission and neural network, is proposed to assess the condition of the storage tank floor. Artificial acoustic emission source by means of a pencil lead break and acoustic emission source cause of corrosion in steel plate is located using neural network trained by time lag of artificial acoustic emission, P-wave, S-wave and Rayleigh wave. It turned out that artificial acoustic emission arrived at sensor is P-wave and acoustic emission course of corrosion is S-wave or Rayleigh wave. Same experiment is made on a specimen of bottom plate of real tank. As a result, corrosion source location using neural network is possible steel plate extended corrosion.

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Effect of shot-peening on fatigue properties for Alloy 718 nickel-based superalloy was investigated. Fatigue tests were conducted under rotating bending at a stress ratio of R=-1 and under uniaxial loading at R=-1 and 0.01. In addition, σ_max=σ_y tests where R ranges from 0.1 to 0.75 were carried out under uniaxial loading. Fatigue strength was higher for shot-peened (SP) specimens than for non shot-peened (NP) specimens. The increase in fatigue strength at 10⁷ cycles was 70% and 15-35% for rotating bending and uniaxial loading, respectively. In parallel with the increase in fatigue strength, the fracture type changed from the surfacetype for NP specimens to the internal type for SP specimens. A facet-like appearance was observed at the crack initiation sites for both the surface and internal type fractures.

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It is known that earthquake caused many damages particularly by the fatigue crack propagation at the welded joints of steel structures. The structures which has not been seriously damaged are still be used after the earthquake. The fatigue strength of these structures, however, might have been decreased due to the cyclic load during earthquake. In order to clarify the effect of large cyclic load on the fatigue strength of the welded joint of steel structure, high cycle fatigue tests after large cyclic straining on welded joints were performed. The results were analyzed by the fracture mechanics to evaluate the effect of fatigue crack due to the large cyclic straining on the high cycle fatigue strength of a welded joint. As a result of the experiment, it was made clear that a static large mean strain decreased the fatigue life but had little effect on the fatigue limit. The application of a large cyclic before high cycle fatigue, however, decreased the fatigue limit of welded joint depending on the size of cracks formed by the large cyclic strain.

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Off axis fatigue behavior of a symmetric cross-ply carbon/epoxy laminate is examined, and a fatigue life prediction method on a ply-by-ply basis is developed. First, tension-tension fatigue tests are performed on off axis specimens of the cross-ply laminate under constant amplitude cycling at room temperatures. The normalized off axis S-N relationship for the cross-ply laminate using the fatigue strength ratio agrees with that for the unidirectional laminate made of the same prepreg tape.This indicates that the off-axis fatigue behavior of the cross-ply laminate is substantially governed by that of the constituent plies in the laminate. Second, on the assumption that the fatigue failure of the constituent plies in the laminate is similar to that of the unidirectional laminates, a simple fatigue failure model for the cross-ply laminate is developed by means of the classical lamination theory and the ply fatigue model considering the in-situ static strengths. Finally, validity of the proposed fatigue model for multidirectional laminates is evaluated by comparing with experimental results. It is demonstrated that the off-axis fatigue lives of the symmetric cross-ply laminate is successfully described using the proposed fatigue model with a consideration of the in-situ strength of ply.

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In this paper, two-dimensional electro elastic analysis is performed for anisotropic piezoelectric materials containing conformal multilayered elliptical inclusion under the in-plane mechanical and electrical loads at infinity. General formed solutions are provided in terms of complex functions by using the conformal mapping technique. Formulations of mechanical and electrical quantities are expressed analogical formulations of mechanical quantities of 3-Dimensional anisotropic problem. Using the solutions, several numerical examples are shown by graphical representation to examine the effects of the piezoelectricity and anisotropy. And the legitimacy of the solutions are discussed

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The influence of water temperature on cavitation erosion has been studied using a vibratory apparatus, but no researches has been conducted at a constant cavitation number in flow condition.This study deals with the influence of water temperature on cavitation erosion using a cavitating liquid jet apparatus. The optimum stand-off distance at 25°C was 11, 15, 21 and 25 mm at cavitation number of σ=0.03, 0.025, 0.02 and 0.015, respectively, and was almost the same as that of a guideline in ASTM G 134 standard. The optimum stand-off distance at 75°C is similar to that at 25°C. The erosion rate increases with liquid temperatures and reaches a peak, followed by a decrease. The peak appears at the approximate average of freezing and boiling temperatures. The relative temperature was defined as 0°C for breezing temperature and 100°C for boiling temperature under the pressurized water. The erosion rate increases at 1%/°C between 5 and 45°C of relative temperatures, and decreases at 2%/°C between 45 and 80°C.

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This paper describes prototype of microcapsule including a bubble for Shock Wave Drug Delivery Systems and evaluation of their mechanical properties. Microcapsules are generated by dropping mixed solution of Sodium Alginate and Polyvinyl Alcohol (PVA) into Calcium Chloride solution (CaCl₂) Young's modulus are estimated by an aspiration experiment and its numerical analysis. Liquid and gas are injected into the microcapsules on micromanipulation system by hand. The result showed that microcapsules generated by low concentration of Sodium Alginate. PVA, and CaCl₂ are able to be injected by micropipette and to make the microcapsule including a bubble. Furthermore, we found the existence of threshold value of apparent Young's modulus between able or disable of injection on the assumption of visco elasticity of microcapsule shell.

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