In this study, multi scale analyses, by using the crystallographic homogenization based semi-implicit finite element code, have been carried out to indicate a plastic strain induced texture evolution and macro-continuum yield loci evolution. This crystallographic homogenization finite element code has employed the double scale hierarchical structure, which consists of a polycrystal microstructure and a macro-continuum. We focus to discuss “How to define a proper microstructure for the double scale finite element analysis, by employing the real polycrystal aggregation, which has been measured by SEM-EBSD apparatus”. For scaling up from the polycrystal microstructure to the macro-continuum, we looked at the periodicity of crystal orientation distribution, which is one of morphological factors to feature the polycrystal structure itself, which is named as “texture”. Through a statistical stydy of these measured polycrystal morphologies, finally we obtaine a realistic polycrystal unit cell of the microstructure, which can be adopted for multi scale finite element analyses. The availability of this code to predict the plastic deformation induced anisotropy and kinematical hardening is confirmed.

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Most current MEMS are using LIGA nickel films as their structural material. In order to design and produce MEMS devices accurately, it is very important to know the mechanical properties of LIGA films. However, the mechanical property evaluation for LIGA films is difficult, because LIGA films have anisotropic mechanical properties due to their microstructures and the specimens to be used in the mechanical property evaluation testing are too small to handle easily. Consequently, the evaluation methods for LIGA films have not been standardized. In this study, the Young's modulus and yield stress of LIGA nickel films are evaluated by a series of spherical indentation testing and elastoplastic analysis. Then, the effect of non-equilibrium microstructures of LIGA films on anisotropic mechanical properties is discussed.

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Slip deformation in compatible type bi-crystal models with tilt angle grain boundary subjected to tensile load is investigated by a finite element crystal plasticity analysis code. Accumulation of geometrically necessary dislocations (GNDs) and statistically stored dislocations (SSDs) are studied in detail. Uniform deformation was expected to take place because mutual constraint of crystal grains through the grain boundary plane does not occur in compatible-type bicrystals, but some results of the analysis show asymmetric deformation with accumulation of GNDs near the grain boundary caused by difference of strain hardening of slip systems, kink bands perpendicular to the primary slip direction and secondary slip bands parallel to the primary slip plane with accumulation of GNDs on the primary slip system in the form of band. Mechanism of dislocation pattern formation in the bicrystals with tilt angle grain boundary is discussed from the viewpoint of imaginary disclination type deformation field with pair body interaction.

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In this study, the influence of the discretizing method, such as a constant element or a linear element, on the accuracy of the identified results is investigated in the boundary value inverse analysis by the Boundary Element Method. For the regularization of the inverse analysis, the combination method is used ; the one that the fundamental solution in B.E.M. is selected adequately and the one that the rank of the coefficient matrix is reduced. The optimum condition for solving the inverse problem is found by two performance indexes which are the condition number of the coefficient matrix and the residual norm caused by the rank reduction of the matrix. In a numerical example, the inverse problem governed by two-dimensional Laplace equation is treated. As a result, the identified result obtained using the linear element has almost the same accuracy as the one using the constant element while the accuracy using the constant element is often better, and the selection method of an adequate fundamental solution is very effective for the inverse analysis. Thus, the inverse analysis may be carried out using the constant element and the adequate fundamental solution selected.

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In this paper, large scale molecular dynamics simulations of tensile deformation of amorphous metals with a nanocrystalline particle were performed in order to clarify the effect of particle size and crystal volume fraction on the deformation property and the strength. It became clear that the size effects of particle are very small, and the influence of the crystal volume fraction is large. The elastic modulus and the flow stress become large as the crystal volume fraction increases. After yielding of the amorphous phase, the stress of the crystal phase still increases. Thus, the flow stress of the composite increases after yielding. It prevents plastic localization and improves the ductility. When the crystal volume fraction is small, the stress distribution is homogeneous in the particle including near the amorphous-crystal interface. Therefore, chances of the originating deformation are small, the inside-particle plastic deformation hardly occurs. When the crystal volume fraction is high, the particles undergo plastic deformation even with small global deformations. After yielding of the crystal particle, the flow stress decreases, because defects are introduced into the crystal. It is expected that the ideal crystal volume fraction which improve the ductility may exist. Lennard-Jones potential which is modified to enforce the continuity at the cut off distance was used. The potential parametes were defined based on Inoue's three basic principles.

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A finite element contact analysis algorithm has to pass the so-called patch test. In the convectional algorithm, the virtual work due to contact force has been evaluated by concentrated contact force and corresponding virtual displacement. This means that the contact force at the contact surface between deformable bodies is not transmitted appropriately in the virtual work sense. In this work, a new algorithm based on one-pass approach is proposed. In this algorithm, the virtual work due to contact force is evaluated by integrating it on the contact surface. Furthermore, the nodal contact pressure in the master contact surface is transmitted from that in the slave contact surface by projecting the master node onto the slave element. In this way, the proposed algorithm is enabled to evaluate correctly the equivalent nodal force due to contact yielding the sucess in the patch test. The effectiveness of the new algorithm is verified by a couple of numerical examples.

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A method for predicting the change in the drain current of deep-sub-micron MOSFETs due to strain was developed. The change in MOSFET drain current can be explained as a linear function of normal strains. The strain sensitivities of the drain current of MOSFETs were clarified experimentally. The drain current of an N-MOSFET increases with increases in in-plane tensile strains and normal compressive strain. On the other hand, the drain current of a P-MOSFET increases with in-plane compressive strain parallel to the channel, and in-plane tensile strain perpendicular to the channel. It also increases with normal tensile strain. The predicted values agreed well with the measured ones. This method for predicting change in the drain current due to stress will help us to improve electronic performance of MOSFETs.

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Porous ceramics have nonlinear stress-strain behavior and are expected to have damage tolerance capability. To assess the nonlinear behavior, we have proposed distributed-micro-crack model.In this paper, some assessment results with the distributed-micro-crack model for porous ceramics are presented. The effects of R-curve behavior and stress concentration are included in the assessment. Constitutive equation of distributed-micro-crack model has been expanded from uniaxial stress model to multiaxial stress model to consider the stress concentration. It was found that our proposed model can simulate the nonlinear stress-strain relationship of porous ceramics for various loading condition such as 3-point bending, 4-point bending with smooth specimen and 4-point bending with notched specimen etc. These simulations also show that 3-point bending test is suitable for assessing nonlinear stress-strain behavior than 4-point bending because 3-point bending can localize the nonlinear stress-strain behavior region which is easily measured by strain gage.

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This paper deals with experiments for detecting two-dimensional small deformations by laser speckle pattern interferometry system. The optical setup uses a laser diode for the source together with a lens to expand the laser beam, and an inspection area can be chosen with the optical setup between 5 × 7.5 mm² (microscopic range) up to 200 × 300 mm² (macroscopic range). The measurements by the macroscopic and microscopic ranges are performed without marking to get overall and detailed deformations of porous ceramic materials respectively. In the macroscopic measurement, it was shown that pore of the ceramics is recognized as a kind of the marker in generating interference fringe. On the other hand, displacement behavior related to the microscopic structure of material can be observed when spatial decomposition of measuring distance is smaller than the pore size is achieved by limiting the inspection area to micro region. In this condition, displacement data with continuous distribution has not been obtained, because displacement measured at pore inside and that at material surface are detected in the one under way without distinguishing at all in the measurement for this microscopic region. However, through the measurement of displacement behavior in crack tip vicinity, it was confirmed that measured displacement distribution agrees with the analytic solution if the data is detected in the position where pore and surface concavity are avoided along the crack edge. By arranging measured data based on above-mentioned processing, valuable information such as strain distributions between adjacent pore was obtained from the measurement for microscopic region.

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In the several engineering fields, biological, sports, aeronautical and aerospace engineering for example, identification of pressure distribution applied on the structure in a very important issue, therefore some expirimental techniques have been suggested to measure the distributed load by piezo-electric sensors or films. However, such a direct measurement often meet with difficulty, because the geometry or rigidity of the contact surface may be altered by attaching the sensors on the surface. In order to overcome the difficulty, this paper deals with estimation of pressure distribution applied on the structure employing the technique of inverse analysis. In the present study, the transmission matrix is introduced which gives linear relation between distributed load and internal strain. Tikhonov's method and truncation of singular value decomposition (TSVD) are used to stabilize the solutions of the inverse analysis. A numerical demonstration for the estimation of foot pressure applied on a rectangular plate is conducted to illustrate the effectiveness of the present numerical formulation to identify the pressure distribution.

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Wedge-shaped defects are frequently observed on the cervical region of the human tooth. Previously, most studies explained that improper toothbrushing causes such defects. However, recent clinical obsarvation suggested that the repeated stress due to occlusal force may induce the formation of these wedge-shaped defects. In this study, therefore, two-dimensional human tooth models are considered with and without a wedge-shaped defect by applying a finite element method. To obtain the intensity of the singular stress accurately, a method of analysis is discussed for calculating generalized stress intensity factors, which control the singular stress around the tip of the defect. Then, the relationship between the stress intensity and occulusion are discussed.

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Tests for evaluating delayed fracture of an E-glass fiber were conducted under water environment. Loaded E-glass fibers were immersed in purified water, and time-to-fracture was measured. Since the delayed fracture was confirmed under the water, the moisture was the only environmental factor for the delayed fracture. The relationship between the chemical reaction and the fiber strength was evaluated for estimating moisture-absorption effect on the delayed fracture. The E-glass fiber surface was observed by XPS and AFM. These observations showed that roughness on the glass surface increased due to the moisture-absorption. Furthemore the fiber-bundle strength decreased with increasing immersion time. The results of these observations indicated that microscopic cracks accelerated the delayed fracture under the water. It is concluded that the delayed fracture of the E-glass fiber occurred by microscopic crack growth caused by moisture-absorption on the glass surface.

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4 point bending tests were conducted on the bioabsorbable Poly (L-lactic-acid) (PLLA) specimens to clarify the effect of annealing condition on the fracture behavior. Injection-molded PLLA were annealed under 10 conditions and DSC measurements were conducted to obtain the crystallinity. Crystallinity increases with increasing temperature and time. Strength of the specimen annealed at 70°C for 24 h has the highest strength, whereas modulus of the PLLA increases with increasing crystallinity, continuously. Fracture surface was observed by scanning electron microscopy (SEM). SEM results indicated that fracture mode varies from ductile to brittle with increasing crystallinity.

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A mathematical model of muscular fatigue and recovery has been developed to be used in motion analyses for evaluating human tasks. To take account of the effects of fatigue and recovery, a model of rate type was developed based on the idea of changes of state of motor unit. Four types of state of motor unit were introduced to simulate fatigue and recovery under dynamic conditions of stimulus input. The response of the model was compared with that of the previous model and the experimental data in literatures. The results showed reasonable agreement. The model is capable of simulating fatigue and recovery under dynamic conditions of stimulus input, such as general human motions.

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The effect of hydrogen on fatigue strength of stainless steels was investigated. There were no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (2.46.4 ppm) and uncharged specimen (2.2ppm) of SUS 304. High content of hydrogen (10100 ppm) was detected in a very thin surface layer, approximately at 100200 μm from specimen surface of SUS 304 specimens hydrogen-charged for 336672 hours. There were also no definite differences in fatigue life of unnotched specimens between hydrogen-charged specimen (1.85.8 ppm) and uncharged specimen (0.1ppm) of SUS 405. The uncharged specimens of 0.7 C13 Cr steel (0.2 ppm) failed from subsurface non-metallic inclusions in surface layer. ODAs (Optically Dark Area) were not observed due to the tensile residual stress in the surface layer although the specimens failed in the high cycle regime of 10⁷ cycles. Increasing hydrogen content from 0.2 ppm to 2.42.7 ppm, the fatigue strength and fatigue life were markedly decreased in 0.7 C13 Cr steel.

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The rotating bending fatigue tests were carried out at room temperature, 200°C, 400°C, 600°C and 800°C with a frequency of 1200 cycles/min. using SUS 304 solution treatment material and SUS 304-1/2 H 10% cold working material, and were carried out at room temperature, 300°C and 600°C using SUS 430 and SUS 403. The cold working material showed higher strength at finite life and fatigue limit in every temperature than the other materials did, although the difference of fatigue limit above 400°C between the cold working material and the other materials were a little. The relationships between the fatigue limit σ_W and the tensile strength σ_B were obtained as σ_W =0.44σ_B for SUS 304 at every temperature and SUS 304-1/2 H over 200°C, and σ_W=0.58σ_B for SUS 430, SUS 403 at every temperature and SUS 304-1/2 H below 200°C. Besides, the relationship between the stress ratio σ_a/σ_ωR.T. and the parameter P= (10-log N_f) /T was proposed to estimate the fatigue strength at finite life, where σa is the bending stress amplitude, σ_ωR.T. is the fatigue limit at room temperature, N_f is the cycles to failure and T is the absolute temperature.

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Axial fatigue tests have been performed using welded specimens of a ferritic stainless steel, SUS 444, in 3%NaCl aqueous solution, and the effect of corrosive environment on fatigue behaviour was studied. The fatigue strength of the welded specimens in 3%NaCl aqueous solution decreased considerably compared with that in laboratory air. Fracture occurred at the toe of weld due to stress concentration, but fracture surface near crack initiation site was brittle, indicating enhanced small crack growth by 3%NaCl aqueous solution, thus in turn leading to decreased fatigue strength. In order to further understand the corrosion fatigue behaviour of welded joints, additional fatigue tests have been conducted using welded specimens whose reinforcement of weld was removed. The fatigue strength of the welded specimens without reinforcement of weld in 3%NaCl aqueous solution decreased significantly compared with in laboratory air. Fatigue cracks initiated from corrosion pits generated in HAZ near the boundary between the weld metal and HAZ at much earlier stage of fatigue cycling and then grew faster than in laboratory air. It was concluded, therefore, that the decreased fatigue strength in 3% NaC1 aqueous solution was attributed to corrosive enviromment-assisted crack initiation and growth.

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We propose a simplified method to evaluate the upper limit stress intensity factor (SIF) range of an inner-surface circumferential crack in a thin-to thick-walled cylinder under steady state thermal striping in this paper. The key idea of the method is to combine our analytical temperature solution for the problem and our semi-analytical numerical SIF evaluation method for the crack, so that we can derive an approximate value of the desired upper limit steady state SIF range. Numerical results showed that our method is valid for cylinders in a range of γ_m/W=10 to 1.

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The mode II initiation fracture toughness of wood was measured by the three-point bend end-notched flexure (3ENF) test for various crack lengths, and the dependence of toughness on the crack length was analyzed by the four conventional methods of data reduction : elementary beam theory, Williams end correction method, and two compliance calibration methods. In addition to these methods, the compliance combination method was used in which the fracture toughness is determined using the load-longitudinal strain compliance measured at the midspan as well as the loading-line compliance. In the four conventional data reduction methods, the dependence of aracture toughness on the crack length was significant. In contrast, the fracture toughness was appropriately determined by the compliance combination method, and it was independent of the crack length. Therefore, the compliance combination method is advantageous in that the fracture toughness is determined accurately by the 3ENF test alone without requiring separate tests over a wide range of crack length.

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In this paper, initial stress measurement theory of micropolar elastic medium by stress release method is described. This measurement method uses the circular solid inclusion cell (SI-cell) as the strain sensor. And because of the SI-cell is regard as inclusion embedded in the micropolar elastic medium, measurement theory is derived by use of the solution of the elastic material with a inclusion problem through the correspondence principle between elasticity and couple stress elasticity. The characteristics of this measurement theory is that the radius of an over coring is finite. Several examples are shown by graphical representation and numerical results.

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Metal injection molding for tiny parts is called micro metal injection molding, “μ-MIM” which is considered to be one of promising process to manufacture the micro parts for various applications. In μ-MIM, the feedstock properties, particularly particle size and shape of metal powder are significantly important for the quality of micro parts. The purpose of this study is to investigate the effect of metal powder characteristics on the compactibility and sinterability. The three types of powders (3μm and 9μm water-atomized powders and 3μm gas atomized powder) were used for the comparison. The melt viscosity of the feedstock was utilized as an index for evaluation of compactibility by injection molding. Then the spring shape of green compact specimen was produced by the micro injection molding machine. The green density was also evaluated for compactibility of the feedstock. The density and grain size of sintered specimens were investigated by changing sintering temperature and time.

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