This paper presents a dual reciprocity boundary element method (DRBEM) applied to the transient heat conduction problem in temperature-dependent materials. The integral equation formulation employs the fundamental solution of the Laplace equation for homogeneous materials, and hence a domain integral arises in the boundary integral equation. This domain integral is transformed into boundary integrals by using a new set of radial basis functions. Furthermore, time derivative is approximated by the time-stepping method, and the domain integral also appears from this approximation. The domain integral corresponding to the so-called “pseudo” initial condition at each time step is also transformed into boundary integrals via the same dual reciprocity method. The details of the proposed DRBEM are presented, and a computer code is developed for three-dimensional problems. Through comparison of the results obtained by the computer code with the results by a finite difference scheme, the usefulness of the present DRBEM is demonstrated.

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As one of the analytical technique of mechanical behavior for the textile composites, inclusion element method by the subcell division was proposed, and the verification on the effectiveness was carried out. In the inclusion element method, it is possible to analyze using very simple grid finite element, obtaining the element siffiness by the inclusion method by cooperation with the fabric structure simulator. As a result of comparing with the real model analysis, it was shown that peculiar condition of the woven composites in the deformation behavior is confirmed and the internal stress is also estimable. The analytical result by the inclusion element model is greatly dependent on approach to division of the subcell, but if it is same or lower level number of elements as the real model, it was shown that the sufficient result was obtained.

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Bolted joints are widely used in mechanical structures since the disassembly for maintenance is easy without much cost. However, vibration induced loosing due to dynamic loading has been unsolved subject over past six decades. In this paper, we have investigated the mechanisms of bolted-joint tightening process and loosening process due to shear loading in the framework of the three-dimensional finite element method (FEM). Results are compared with the previous theory based on the material mechanics and experimental results. We found some new aspects for bolted-joint theory. Previous theory overestimates the tightening torque in the relation between axial forces and tightening torque. Since the previous theory ignores the extrusion of bolt from nut and the stiffness of jointed material, the load distribution of 1st pitch decreases and that of 4th pitch turns to be minimum. Good qualitative agreement is observed between FEM and experiments with respect to behavior of loosening process subjected to shear loading, such as hysteresis loop of transverse displacement and transverse load and critical slipping distance for gross slip at the head contact surface. It is found that loosening has started when complete thread contact slip has occurred prior to the gross slip at the head contact, which has been considered as an initiation point of loosening. Therefore, the modification of the design of bolted joint is needed.

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The purpose of the present study is to elucidate the “ideal strength” of the Ni and Ni₃AI single crystals, the main compositions of Ni-based superalloy, from the viewpoint of the lattice stability. The unit lattices of Ni and Ni₃Al, fcc and L I₂ ordered alloy, are subjected to the [001] uniaxial tension/compression and hydrostatic tension/compression by using the Vienna Ab-initio Simulation Package (VASP) with the generalized gradient approximation (GGA) and ultrasoft pseudopotential. The elastic stiffness matrix is numerically evaluated at each point in the applied deformation pass, then the lattice stability is discussed based on the positiveness of the matrix. Both Ni and Ni₃Al reaches the Born's stability criteria against the bifurcation to the anisotropic Poisson's contraction in the [001] uniaxial tension, while they do the spinodal criteria against the structural transformation in the [001] uniaxial compression and hydrostatic tension. The hydrostatic compression increases the stability and shows no limit, however, it is also suggested that the spinodal instability appears when the ideal isotropy was broken. The “ideal strength” is evaluated with these stability limits and indicated as “yield curve” on the normal strain-lateral strain or normal stress-lateral stress planes.

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In a dynamic analysis of biological sample using finite element method, generally biological mesh models are made of X ray CT or MN1 image data. These images resolution are about 1 mm, but some biological tissues' sizes are less than 1 mm. In this study, we proposed digitizing with 3-dimention internal structure microscope (3D-ISM). This device slices a fixed sample, and obtains a cross-sectional image that is μm order. In addition, we propose the method of generating the mesh model of high accuracy from the observation data of 3D-ISM as it is semiautomatic. Shape and quality were compared by voxel mesh and mapped mesh. As for shape mapped mesh can represent detail of each eye tissue. As for quality voxel mesh is constancy. In mapped mesh, we compared three type of shape before project, in order to examine whether it is applicable to general tissue. A coarse model is least distortion of an inner side and an outside, and considered that each individual difference of tissue is absorbable.

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The two-dimensional finite element formulation for the basic field equations governing electrochemical responses of ionic conducting polymer-metal composite (IPMC) actuators is proposed in the present study. Biaxial bending deformation of a platinum plated Nafion actuator having 4 electrodes is dominated by internal water redistribution, which is associated with electroosmosis of hydrated ions and self-diffusion of free water molecules. Two processes can be considered separately in the way that fast electroosmosis is followed by much slower self-diffusion. Some numerical studies for IPMC actuators with several types of electric field are carried out in order to show the validity of the proposed formulation.

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Induction hardening is one of the methods of heat treatment for steel members. It is difficult to determine the optimum heating conditions for steel members of complicated shape so that the computational tool is necessary for the simulation of the behaviors of those members in induction hardening. The present study is concerned with the development of the 3-dimensional finite element method considering induction heating, thermal elasto-viscoplasticity with damage and phase transformation. Numerical studies for the process of induction hardening of steel bars have been done to demonstrate the validity of the present method

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Macroscopic ferroelectric properties of piezoelectric polycrystals are strongly affected by microscopic non-homogeneous crystal structure. In our previous study, a multi-scale finite element procedure based on crystallographic homogenization method has been developed to predict macroscopic properties by considering microscopic crystal morphology. In this study, a crystal orientation distribution of polycrystalline barium titanate has been measured by SEM·EBSD technique, and it has been introduced to the microscopic finite element model, which satisfies the periodicity. As the prediction of macroscopic properties depends on the sampling conditions of the measured crystal orientations, the effects of number of sampling points and sampling area have been investigated.Additionally, the influence of dispersion of crystal morphology on macroscopic ferroelectric properties has been discussed.

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On the topological optimization problem of structure, it is desirable to set up the large design domain at the point that can search for the solution widely. However, to set up the large design domain is to increase the design variables. It will become difficult to search the optimum solution. In this study, a technique to prevent the increase of the design variable under the large design domain is proposed by performing space management of a design domain using the quad-trees data structure.By using the technique, a structural layout problem optimizing the plate thickness is analyzed. In the optimization the GA is used and the optimum topological solutions are obtained effectively.

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This paper deals with identifying multiple cracks from eddy current testing (ECT) signals obtained in a steam generator tube with a support plate and deposits. Assume two-dimensionally scanned ECT signals to be a picture image, then the signal processing by a multi-frequency technique eliminates noise caused by the support plate and deposits. A template matching with help of genetic algorithms detects number and positions of cracks from the image after the signal processing.Inverse analysis estimates the crack profile based on the predicted position of cracks. The number and positions of the cracks are sufficiently well predicted. Crack shape reconstructions are achieved with a satisfactory degree of accuracy.

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For evaluating fatigue strength of ductile cast irons, influences of many complicated factors such as surface roughness, transition of microstructures from surface to interior, defects and residual stresses must be considered separately. In order to clarify the effects of surface roughness and microstructure transition layers on fatigue strength, plane bending fatigue tests have been carried out on the specimens with as-cast surface, composed of ferritic and pearlitic structures. The residual stress introduced by shot blast to surface layers of a specimen was relieved by annealing in order to evaluate the independent influence of various factors separately. The fatigue strength has been evaluated by using the √area parameter model. Surface roughness was regarded to be mechanically equivalent to a defect. The size of the defect has been defined by the projected square root of area, √areaR.The equivalent hardness HV was also defined by considering microstructure transition layers. The evaluation method of the maximum detect size by statistics of extreme and the lower bound of the scatter of the fatigue strength have been proposed for practical design.

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The authors deduced strain analysis formulas of strain gauge models and attempted to fabricate strain gauges experimentally using a piezoelectric polymer film in this study. Constant cyclic load tests were carried out using semicircular-holed notched test specimens and center-circular-holed plate. Strains S_x, and S_y are analyzed using the deduced strain formulas. As a result, the following conclusions are drawn. (1) As a result of analyzing the strain using piezoelectric polymer thin film strain gauges, it was shown that the strain analysis method used in this study is effective and the trial strain gauges can he used as an effective tool in an experiment. (2) The piezoelectric polymer film exhibits load frequency dependence. This dependence is a problem in strain measurements. Thus, the authors devised a method of improving this dependence.

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In this paper, the practical method to estimate the stress concentration factor (SCF) of two dimensional surface complex roughness is proposed. In the present method, the surface roughness is approximated with an infinite row of colinear notches which consists on “the local configuration” and “the average configuration”. The SCF values of the notches are calculated independently, and the SCF of the surface roughness is obtained by the superposition of each SCF values. The application limit of the present method is examined with the exact or Finite Element Method (FEM) solution. Moreover, the problem of colinear row of arbitrary notches which are satisfied with the application limit is solved by the present method and FEM. Comparing the present solution with FEM solution, the validity of the present method is examined.

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A new method to evaluate the mode I stress intensity factor for a semi-circular micro surface crack subjected to a three-dimensional complicated stress distribution under ball-on-plate contact loading was proposed. Fabrikant & Hanson's equation, which was originally derived to evaluate the stress intensity factor of a penny-shaped subsurface crack, was applied for this problem, and the obtained value was compared with the result of the three-dimensional finite element analysis. For the crack which radius was less than 10 1.tm, the ratio of them was almost constant irrespective ofthe applied load, the crack radius and the distance from the contact point to the crack. Multiplying the ratio as the correction factor in the value obtained from the method using Fabrikant & Hanson' equation, the stress intensity factor for a semi-circular micro surface crack under ball-on-plate contact loading could be evaluated conveniently.

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Monotonic compressive loading and relaxation tests were conducted under constant and time-varying strain rate conditions of 1.1 x 10^-2-10^-5 and 10-40°C for polyphenylen-ether (PPE), an amorphous polymer. The observed stress-strain responses were similar to those of other engineering plastics showing notable effects of the strain rates and temperature, but the strain-rate change tests revealed predominant overshoot phenomena in the stress transfer processes. The experimental results indicated that the concept of time-temperature equivalence is also applicable to PPE and the comparative investigation on the effect of crystallinity and the material constants which control the time-temperature scale shift was carried out for five polymeric materials. The viscoplastic constitutive model based on overstress successfully reproduced the observed stress-strain responses including the overshoot phenomena using a newly proposed additional function which control the viscosity in the model.

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Symmetrical bending of a circular laminated plate containing a disc-shaped delamination subject to thermal gradients is analyzed on the basis of the theory of small deflection of plates. General equations for the axisymmetrical bending of a bilayer plate are derived. A disc-shaped crack model assuming the contact of the two crack faces is then considered. Radial in-plane forces induced by bending in the parts of the plate above and below the delamination are determined by modeling the cracked part as two lapped discs hinged at both rims. If there is no temperature gap between the two faces of the crack, then the plate is bent to a spherical cap whose curvature is independent of the radius of the crack, so that the energy release rate is identically zero. The condition for the contact of crack faces is also discussed. It is concluded that the model assuming that the deflections of the plates upper and lower to the crack are different have to be considered to get more precise insight for the crack growth behavior.

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Symmetrical bending of a circular laminated plate containing a disc-shaped delamination subject to thermal gradient is analyzed on the basis of the theory of small deflection of plates. A disc-shaped crack model where the crack faces are open is considered. Radial in-plane forces are induced in the parts of the constituent plates above and below the disc-shaped crack. A nonlinear equation for determining the in-plane forces is derived by modeling the cracked part as two lapped discs hinged along both rims, and by imposing the compatibility condition of the deformations of the two plates. Numerical solutions are obtained for some model plates. It is shown that relative displacement at the center of the crack increases gradually with the increase in temperature gradient. However, at a critical temperature gradient, the relative displacement begins to increase very rapidly, i.e., local delamination buckling occurs. Energy release rate is small for temperature gradient below the critical value, but it takes a large value when the temperature gradient is increased above the critical value. Energy release rate also increases with the increase in the radius of the crack and hence the buckling driven delamination grows unstably.

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Bending creep tests were conducted on alumina-alumina butt joints at temperatures of 788-888 K. The lifetimes in three-point bending tests under constant loads were measured and the specimens tested were investigated using scanning electron microscope. From the elastic stress-distribution at the joining layer calculated using the finite element method, it was confirmed that the thin metal film in the joining layer is under the conditions of tri-axial tension and the hydrostatic tensile stress. The results of SEM observation of creep fractured surfaces showed numerous small and large cavities in the tension side of the joining layer. Under the assumption that the mechanism of creep deformation and fracture for the thin metal film in the joining layer were the nucleation, growth and aggregation of cavity with the aid of the hydrostatic tensile stress component, the lifetimes in creep bending test were predicted. Time-dependent change of stress distribution related to initial outer fiber stress in bending has been calculated with formulas based on linear-elastic beam theory. Predicted lifetimes are in good agreement with the experimentally obtained lifetimes. The neutral-axis position measured from the photographs of the fracture surfaces can be explained by the predicted stress distribution in creep bending tests.

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Reliability of automobiles is increasingly demanded. To prevent burst of tires, smart tires are currently under development. Most of the smart tires have integrated or attached sensors to measure deformation or internal pressure of tires during a long period of service. The embedded sensor enables highly precise measurement of road surface friction, and the precise friction measurements make more efficient anti-lock braking system (ABS). In a previous study, the authors proposed a new wireless strain monitoring method that adopts the tire itself as a sensor, with an oscillator circuit. This method is very simple and useful, but it requires a battery to activate the oscillator circuit. In the present study, the previous method for wireless tire monitoring is improved to produce a passive wireless sensor. A specimen made from a commercially available tire is connected to a tuning circuit comprising an inductance and a capacitance as a condenser. The proposed method enables us to measure an applied strain of a specimen wirelessly, without any power supply from outside. This new passive wireless method is applied to a specimen and an applied strain is measured. As a result, the method is experimentally proved to be effective for the passive wireless strain monitoring of tires.

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In this paper, a spark plasma sintering (SPS) method was employed to solidify single-walled carbon nanotubes (SWCNTs) only, and the effect of sintering conditions on the mechenical properties of the SWCNT solids were examined using a small punch (SP) testing method. The sintering temperature used in the range of 600-1 400°C, and the sintering pressure used 40 MPa and 120 MPa. It was demonstrated that the SPS method allowed SWCNTs to be solidified, without any additives. The experimental results showed that the purification of raw soot was critically importance. The SWCNT solid prepared from purified raw soot showed significant non-linear deformation response, producing quasi-ductile fracture behavior. In contrast, unpurified raw soot produced brittle SWCNT solids. The Young's modulus, fracture strength and work of fracture increased with increasing sintering temperature and pressure. The Raman scattering and SEM observations showed that the amount of the graphite-like materials were observed to increase with the increasing temperature and pressure, which indicate that the structure of the SWCNTs was changed partially into the graphite-like materials. The formation of graphite-like materials increased tendency of brittle fracture in the SWCNT solids. TEM observations revealed that the fracture surfaces of SWCNT solids were characterized by pull out of SWCNT bundles. This observation suggests that it may be possible to improve the mechanical properties of SWCNT solids by increasing the cohesion between SWCNTs.

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It is very important to accurately evaluate the mechanical properties of industrial materials accurately. Knowing those properties, one can produce mechanical and structural designs that are both safe and economical. This paper describes a newly developed control method for an intelligent universal test machine that can measure stress, strain, and time and give those measurement results. This report describes the main results obtained from this study. This study obtained the transtition point between elasticity and plasticity of an unknown yield point material. Visualization of the material deformation behavior demonstrated the possibility material of properties measurement.

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The elastic moduli of spring steels were measured by the ultrasonic pulse method and influencing factors on elastic moduli were discussed quantitatively. Results obtained are as follows : (1) Elastic moduli of spring steels depend on heat-to-heat variation, material specification and conditions of heat treatment. (2) A new parameter described by temperature and time of the tempering condition was proposed to explain the effect of tempering conditions on elastic moduli. (3) Diffusion process of carbon was pointed out as the reason of variation of elastic moduli due to the tempering treatment. (4) Linear models where independent variables are contents of C, Si, Ni, Cr and Cu in mass%, reciprocal of tempering temperature in K, and natural logarithm of tempering time in h, can be used to explain the moduli with an accuracy of 0.5%. (5) These models can't be applied for spring steels containing Vanadium.

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Compressive tests were carried out to measure the mechanical properties such as Young's modulus and strength of a pig's liver. There is no evidence showing macroscopic anisotropy in the liver although blood vessels were distributed in a quasi transversely isotropic array. Compression tests of the liver specimens which are not mechanically constrained gave more accurate stress-strain behavior rather than those of the constrained specimens. The Young's modulus and yield stress of a fresh live within 12 h after the slaughter are almost constant regardless of the presence of physiology brine solution. The intestine membrane has higher Young's modulus and maximum strength (or yield stress) than internal tissue of the liver. However, strain for crack initiation of the membrane is almost equal to yield strain of the internal tissue. Yield strain is used as a valid parameter which evaluates mechanical damage of the liver. The tangent modulus of the liver which shows viscoelastic phenomena can he approximated by a binomial function. This function can he applied to not only an soft tissue under compressive loading but also a stiffer membrane loaded in tension.

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In order to improve friction and wear properties of amorphous SiC film deposited on titanium substrate specimen, Ti or Al was added in SiC film by simultaneous sputtering of SiC and Ti or Al targets using a dual-cathode RF magnetron sputtering apparatus. Wear tests were carried out on the specimens using a ball-on-disk type testing apparatus with SiC ball. The result shows that the addition of a certain amount of Ti or Al decreases wear rate of SiC film and increases the number of rotation cycles to delamination. When the Ti concentration is 2.6 at.%, the friction coefficient decreases to a minimum value of 0.04, which is about a half of SiC film without Ti and diamond-like carbon (DLC) film. This lower friction coefficient of SiC-2.6%Ti film than DLC film is obtained also for other ceramics and metal balls. The SiC-1.5%Al film reveals higher wear resistance than the SiC or SiC-Ti films with low friction coefficient of 0.1. Observation of wear scar in the film and SiC ball during the wear test implies that wear debris plays an important role in reducing the friction coefficient. Nano-indentation tests shows that the stiffness and elastic modulus of SiC-1.5%Ti and SiC-3.6%Ti is the largest among other SiC films with different Ti or Al content.

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In this paper, the applicability of a technology with using infrared sensing was elucidated for mine exploration in dry and desert zones where it is comparatively easy to specify the surface emissivity. It is very important to avoid the danger pertaining to mine exploration as much as possible by using an appropriate nondestructive testing method. From the viewpoint of numerical simulation with an appropriate mathematical model, the exploration mechanism, the exploration limit, various factors which accompany the mine exploration were examined systematically. As a result, the following facts are found : (1) the infrared mine exploration with the aid of natural environment conditions, depending on surface emissivity and sunshine duration band, etc., has an optimum exploring condition, (2) the mine exploration becomes difficult with increasing the buried depth, (3) the exploration is difficult for the case where various contaminations or any vegetation exist on and in soil around mines.

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