In the fracture problems in the functionally graded materials (FGMs), singular deformation field near the crack tip is appeared in the gradient field of material properties. In the finite element analyses for the fracture of FGMs, this complex fracture behavior has to be solved by using fine mesh subdivision. In this study, the moving finite element method is devoloped to simulate fracture behavior of four points bending specimen consists of the FGM. In the moving finite element method based on the Delauney automatic triangulation, effective mesh subdivision is updated with crack propagating. The T^* integral is used as criterion to evaluate crack tip condition, because the material properties distribution in FGMs has to be considered to derive exact crack tip parameter. Far-field path independence of the T^* integral is mathematically proved for the fracture in the FGM. The path independence of the T^* integral is also confirmed from the numerical results of the moving finite element analyses. This numerical prediction is demonstrated for four point bending fracture in FGMs. Based on the T^* integral and stress intensity factor, crack propagation path is predicted by the localy symmetry condition. The numerically predicted crack propagation path is compared with experimental result.

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Crack propagation path prediction is very important to prevent critical industrial accidents. However it is considered that the crack propagation path prediction is very difficult in occasion of High Eccentric Impact Loading. In this study, dynamic fracture path prediction under eccentric load that assumed the heavier mixed mode dynamic fracture was simulated by Moving Finite Element Method Based on Delaunay Automatic Triangulation. The generation phase and mixed phase path prediction mode simulations were carried out in these fracture simulations. The Penalty method was incorporated in order to consider the crack surface contact effects. The predicted fracture path using the Penalty method is agreed with experimental fracture path.

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The Free Mesh Method (FMM) was developed to solve the issue of mesh generation that is one of the great bottlenecks in parallel computing. The FMM is, however, difficult to combine with quadratic elements that should be used for higher accurate analysis. The Enriched Free Mesh Method (EFMM) was presented to improve the accuracy of the FMM. The conventional EFMM is, however, inaccurate as compared with the FEM using quadratic elements. The present paper therefore is intended to propose a higher accurate EFMM, where the drilling degrees of freedoms is newly added for the improvement of the accuracy. The consistency of the proposed method is proved by the three-dimensional patch test. In some problems, we find that the accuracy of the proposed method exceeds the conventional EFMM and it is equivalent to that of the FEM using quadratic elements. The analysis result of a plate with a cavity has shown that the accuracy of stress by this method is very high. It is concluded that this method is extremely effective to analyses of large-scale structures under complicated loading conditions.

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Capacitive micromachined ultrasonic transducers (cMUTs) are a new type of transducer with applications in medical ultrasound equipment. This paper presents a topology optimization method for the structural design of cMUTs, in which the outlines of target structures are implicitly represented using the level set method, and uniform cross-section surface constraints are taken into account. First, the optimization problem that addresses the design requirements of the cMUT is formulated. Second, basic details of the level set-based topology optimization method are briefly discussed. Based on the concept of the Tikhonov regularization method, the topology optimization method considering a uniform cross-section surface constraint is formulated. Next, based on this formulation and the level set method, a topology optimization algorithm is constructed where the Finite Element Method is used when solving the equilibrium equations and the level-set equation. Finally, two- and three-dimensional examples are provided to confirm the validity and utility of the proposed topology optimization method.

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This paper deals with an inverse problem for estimating the residual stress distribution in a butt-welded plate from stress data measured at some points. The welding residual stresses in the butt-welded plate are caused by inherent strains. Thus, the welding residual stresses in the butt-welded plate are calculated if the inherent strains are estimated from measurement data. In previous works, a method was proposed to estimate the inherent strains of constant distribution in the butt-welded plate using thermo-elastic boundary element inverse analysis. This paper examines the applicability of the boundary element inverse analysis method when the inherent strain distributions are trapezoidal or triangular. Tikhonov's regularization is used to improve the accuracy of the estimated values of the inherent strains in the butt-welded plate. The discrepancy principle is applied for estimating a proper value of the regularization parameter α. Numerical simulations are conducted for an analysis model which is the same with that used in the previous paper. Noisy stresses measured at some points are used for the simulations. The results of the calculations showed that the inherent strains in the butt-welded plate were evaluated in high accuracy from a few measured data by using Tikhonov's regularization even if the inherent strain distributions were trapezoidal or triangular. It was found that the discrepancy principle worked well for selecting a proper value of the regularization parameter α in Tikhonov's method.

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Equivalent stiffness of plates clamped by bolted joints for designing should be evaluated according to not only the strength of bolted joints but also the deformation and vibration characteristics of the structures. When the applied external axial load or the bending moment is sufficiently small, the contact surfaces of the bolted joint are stick together, and thus both the bolt and the clamped plates deform linearly. Although the sophisticated VDI 2230 code gives the appropriate stiffness of clamped plates for the infinitesimal deformation, the stiffness may vary nonlinearly with increasing the loading because of changing the contact state. Therefore, the present paper focuses on the nonlinear behaviour of the bending stiffness of clamped plates by using Finite Element (FE) analyses, taking the contact condition on bearing surfaces and between the plates into account. The FE models of the plates with thicknesses of 3.2, 4.5, 6.0 and 9.0mm tightened with M8, 10, 12 and 16 bolts were constructed. The relation between bending moment and bending compliance of clamped plates is found to be categorized into three regions, namely, (i) constant compliance with fully stuck contact surfaces, (ii) transition showing the nonlinear compliance, and (iii) constant compliance with one-side contact surfaces. The mechanical models for these three regions are proposed and compared with FEM solutions. The prediction on the bounds of three regions is in a fairly good agreement except the case with smaller bolts and thicker plates.

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Compression test of roll core sandwich panel was carried out by varying the cell wall tickness and the cell size. From obtained results, it was found that compression strength and energy absorption were proportional to the square of core density and inversely proportional to the cell size. By comparing with the compression property of honeycomb core sandwich panel, it was observed that the roll core sandwich panel was superior to the honeycomb core sandwich panel. It was because the roll core sandwich panel had the larger reinforced area by constraint of cell deformation than the honeycomb core sandwich panel.

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In this study, influence of grip length and engaging thread length for a bolted joint on fatigue characteristics under transverse vibration has been investigated. The relationship between the apparent fatigue limit and the real fatigue limit has been experimentally revealed. In the experiments, the apparent fatigue limit and the real fatigue limit were investigated for three separate tightening conditions of a bolted joint combined with various grip lengths and engaged thread lengths. And fatigue characteristics of a bolt/nut assembly also were investigated. The results showed that the relationship between the apparent fatigue limit and the real fatigue limit depends on the bending moment at the root of the first thread.

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Thin-film mechanical resonators are promising for high frequency bandpass filters. Amorphous oxide thin films are expected to be important candidates because they are free from grain scattering loss. However, it has been difficult to characterize their acoustic properties, especially attenuation, which is a key parameter for designing a high-Q resonator. Here, we present a novel methodology for evaluating ultrasonic attenuation in amorphous oxide thin films deposited on silicon substrate very high frequencies between 200 and 300GHz. This method uses the high sensitivity of the refractive index of light in silicon to the wavelength near 400nm. Detecting Brillouin oscillations from silicon substrate, which is caused by the transmitted acoustic wave, we can evaluate the frequency dependence of the attenuation coefficient in the thin film through an inverse calculation.

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Weld Overlays (WOL) have been widely used in many countries as effective methods to repair pipes with stress corrosion cracks in nuclear power plants. Authors have developed the theoretical equations to estimate plastic collapse bending moments for weld overlaid pipes with circumferential part-through cracks, based on net-section stress approach. The objective of this paper is to compare the calculated stresses with experimental data of full-scale WOL pipe specimens. The procedures of JSME fitness-for-service code were employed for the calculations of Z factor and flow stress. From the comparison of experimental data, it is demonstrated that the methods are applicable to the flaw assessment for the JSME fitness-for-service code.

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Effect of hydrogen on tensile properties of ferritic-pearlitic carbon steels was investigated. Tensile tests were conducted in air at room temperature using virgin and 10%-30% pre-strained specimens of the following carbon steels: IF (0.002mass%C), S15C (0.17mass%C) and S45C (0.43mass%C). Volume fraction of pearlite of these steels varied from 0% to 54.7% with increasing carbon content. The specimens were charged with hydrogen by immersing in a 20mass% NH_4SCN aqueous solution at 313K for 48h. The results of the current study were combined with results for SGP (0.078mass%C) and STPG 370 (0.19mass%C) from previous studies. Hydrogen content increased with pre-strain and volume fraction of pearlite. The tensile strength was not changed by increasing hydrogen. In contrast, the reduction of area decreased with increasing hydrogen content. At the same hydrogen content, the relative reduction of area, φ_H/φ (where φ is reduction of area of uncharged specimen and φ_H is that of hydrogen-precharged specimen), was higher for low carbon steels (IF and SGP) than for others (S15C, STPG370, and S45C). The difference in the φ_H/φ value between these steels was caused by a difference in fracture morphology. That is, voids were formed in IF and SGP steels, whereas pearlite cracks were formed in S15C, STPG370, and S45C steels. From these results, guidelines for the application of carbon steels in hydrogen environments were proposed.

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Thermal barrier coatings (TBCs) are usually deposited onto the surface of the high-temperature component such as gas turbine, in order to protect it from a high-temperature environment. Coating stress generated by such a high-temperature brings serious damages in TBCs in service. For predicting numerically it, it is necessary to develop the constitutive equation suite to plasma-sprayed TBCs. Previous study has made clear that the freestanding ceramic coat peeled from TBC coated substrate deforms nonlinearly with a mechanical loading, however the results there have been restricted to the test done using as-sprayed sample. In this study, effect of deposition parameter and high-temperature exposure condition on stress-strain curve of the freestanding ceramic coating sample was examined. The associated deformation process was discussed with the microstructure changes observed after performing a bending test for the exposed sample.

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Viscoelastic stresses and creep deformations in the laminated hollow hemisphere composed of a viscoelastic body and a nonhomogeneous elastic body are analyzed using integral forms of stress-strain constitutive relations and based on the correspondence principle between the Laplace transformed viscoelastic solution and the analytic solution for the corresponding elastic problem. The analytic solution for elastic problem is formulated in terms of Papkovich-Neuber displacement function, and the Laplace transformed stresses and deformations of viscoelastic hollow hemisphere are obtained through the replacement of the elastic moduli by the Laplace transformed viscoelastic relaxation functions. The inverse Laplace transform of the solution is performed by Hosono's method of numerical inverse Laplace transformation.

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This paper deals with the analysis of the stress intensity factors of a subsurface crack on the periphery of a rigid inclusion on a circular void in an elastic half space subjected to rolling contact with frictional heat. 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 crack and the inclusion or void to the simulutaneous singular integral equations. This integral equation is solved numerically thus enabling the numerical calculation of stress intensity factors on the periphery of an inclusion or a void in a half space. The influences of changing the frictional coefficient, slide/roll ratio and the crack length on the interference effects between a subsurface crack and an inclusion or a void are considered.

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Fatigue life evaluations in low dissolved oxygen conditions have been considered as conservative in predicting fatigue strengths of biomaterials. However, dissolved oxygen is considered to increase crack propagation rates. It is necessary to observe whether the strength in low dissolved oxygen conditions becomes higher. In this paper, authors observed effects of dissolved gas on corrosion fatigue characteristics of austenitic stainless steels. Fatigue strength becomes higher in low dissolved O_2 NaCl aq. at stress ratio R=0.1. However, fatigue strength did not change in low dissolved O_2 NaCl aq. at stress ratio R=0.5 because of the effect of work hardening. Cycles to crack initiations became longer and crack growth rates became lower in low dissolved O_2 NaCl aq.. In conclusion, dissolved oxygen has effects of accelerating crack propagation processes.

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The purpose of this research is the development of a high strength α-β brass (Cu-40 Zn) with additions of elements of small solid solubility in brass. Cu-40 Zn with 0.6mass% Tin (Sn) and various contents of Chromium (Cr) and Iron (Fe) were prepared by casting (Cu-40 Zn-CrFeSn). The yield strength (YS) and ultimate tensile strength (UTS) of cast Cu-40 Zn-CrFeSn has 190MPa and 400MPa. Furthermore, the YS and UTS of extruded Cu-40 Zn-CrFeSn was 300MPa and 600MPa, 23% and 36% higher than that of extruded binary Cu-40 Zn alloy. Vickers micro hardness of 158Hv was higher than that of extruded Cu-40 Zn alloy (131Hv). In addition, the elongation of extruded Cu-40 Zn-CrFeSn was 35%. The strengthening mechanisms of these alloys were considered as follows; one was a solid solution strengthening of Cr, Fe and Sn additives which were identified by TEM-EDS and SEM-EDS. The other was increasing of the area ratio of β-phase in Cu-40 Zn-CrFeSn, compared to that of Cu-40 Zn.

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Recently, recycling of the waste plastics has strongly been desired. Particularly, recycling of the waste glass fiber reinforced plastics (GFRP) is technically difficult and they cause heavy damage on our environment. The establishment of the recycling technology for the waste GFRP is urgently necessary. In this study, by mixing the clay and the waste GFRP and sintering the mixture, the development of the high strength porous tile was attempted. First, by changing the mixing ratio of the waste GFRP, several kinds of tile specimens were produced, and the microstructure of each specimen was observed using the SEM and the microscope. Next, the bending strength and water absorption of the specimens were examined in detail. From those results, it was confirmed that our proposed glass fiber reinforced porous tile had the high strength and that the glass fibers could be recycled effectively as the reinforced material.

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In the present study, degradation properties of the polymer blends films of Poly (lactic acid) (PLA) and Poly (butylene succinate) (PBSU) with different mixed fractions were investigated. Immersion tests in phosphate buffered solution were conducted on the polymer blend films. After 0, 8, 16 and 24 weeks immersion, tensile tests and viscosity averaged molecular weight measurements were performed to evaluate the relation between mechanical properties and degradation. Tensile strength of PLA/PBSU 100/0, 80/20 50/50 decreased after 24 weeks immersion. Molecular weight of pure PLA and PBSU decreased with immersion. Degradation rate of PBSU was larger than that of PLA. Autocatalytic reaction model was used to simulate molecular weight of pure PLA and PBSU. This model was also used to predict molecular weight to PLA/PBSU blends. It is clarified that the model can predict the tendency of molecular weight change in PLA/PBSU polymer blends.

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In the rules on fitness-for-service for nuclear power plants of the Japan Society of Mechanical Engineers, only a equation is given in its appendix for assessing the limit load for ductile materials, although the finite element analysis (FEA) is available in the code for design. This study aimed to show the validity of applying FEA for limit load assessment of flawed components. The target of analysis was a pipe containing circumferential crack. Limit loads obtained by FEA tended to be larger than those given by the equation. It was revealed that this tendency was brought about by the notch effect. The stress triaxiality increased at crack tip, and this enhanced the load carry capacity of cracked pipe. It was concluded that FEA can be applied for limit load assessment for a cracked pipe.

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Basket material of transport and storage cask is required to have not only a structural strength during transport and storage conditions, neutron absorbing function but also heat removal function. The basket material is also preferable to be light in order to reduce the weight of cask because it is very important to improve the efficiency of transport and storage by increasing the number of fuel assemblies loaded in cask. Aluminum alloy is suitable base material for basket due to its low density and high thermal conductivity. Enriched borated aluminum alloys have been developed, suitable for application to baskets in transport and storage casks for spent fuels. This borated aluminum alloy is 1% borated in A6061-T6/T651 alloy. In order to use this material for cask basket, it is necessary to be registered to the "Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)" by the Japanese Society of Mechanical Engineers. Therefore, various mechanical properties such as tensile strength at elevated temperature with or without long term aging, creep properties and fracture toughness, etc.. And the allowable stresses of 1%B-A6061-T6/T651 have been evaluated according to the "Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)".

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