The fretting fatigue of rail steel with fish plate were examined using the clamping contact double bridge pads system. In order to investigate the effects of contact pressure and relative silp amplitude on fretting fatigue strength, the fretting fatigue tests were carried out at three contact pressures and with three pad lengths. The fretting fatigue strength decreased with increasing contact pressure for all stresses and with increasing pad length at higher stresses. Interrupted fretting fatigue tests were carried out in order to investigate the fretting damage. The ratio of the crack initiation life due to the effect of fretting damage to the whole fatigue life was less than 60%, and the effect was influenced by the relative slip amplitude.

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Austempered ductile cast iron (ADI) is attracting much attention as one of new materials. Its mechanisms of crack initiation and propagation vary with the relation between the properties of graphite and matrix structures. In this study, we focused on the following two topics : First, we considered what effect the thermal environment has on high-cycle fatigue of ADI. As an example of thermal environment, when vehicle gears come into contact with each other for a long time, due to a material change in the contacting face as well as the thermal environment, fatigue strength will decrease. There is no literature discussing fatigue strength at the Ms transformation temperature below it. Therefore, high-cycle fatigue strength under as near the Ms transformation temperature environment was compared with that under room temperature environment and discussed. Plots of fish-eye fractures on the S-N curve show a wide scatter of life. Therefore, attention, was paid to fish-eye fractures and defects considered to be the starting point of crack development. It was clear that they show stress dependence from observations of their SEM micrographs. Thus, a modified S-N curve in the fish-eye fracture region could be obtained from an arrangement using the defects and fish-eye areas.

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The estimation of fatigue reliability and fatigue mode above glass transition temperature (T_g) for earbon fiber reinforced PEEK was conducted. Self-heating and meso crack forming concerned with thermal and mechanical fatigue was focused on. The main results are as follows, (1) It was recognized that the fatigue characteristics of test pieces above T_g differed from those under T_g. Thus, the influence of environmental temperature on fatigue characteristics was arranged by 'S-N globe'. (2) The fatigue mode at elevated temperatures was divided into two mechanisms. One was thermal fatigue for short fatigue life, the other was mechanical fatigue for long fatigue life. (3) In the case of thermal fatigue, fracture surface was ductilc and self-heating was large : in the case of mechanical fatigue, the former was brittle and the latter was small. (4) The roles of carbon fiber were to constrain the deformation of matrix on thermal fatigue, and to control meso crack forming on mechanical fatigue.

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This paper deals with the surface fatigue crack growth behavior in cemented carbides and ceramics under repeated rolling contact with frictional heating. In this analysis, a surface crack is modeled as an inclined planar surface crack in a three-dimensional half-space. Rolling contact is simulated as a long and narrow distributed load with both normal and shear components moving with constant veloccity. First, the three modes of stress intensity factors along the crack contour are analyzed. Next numerical calculations of the stress intensity factors are carried out for cemented carbides and ceramics. On the basis of these data, numerical results for crack growth contours are given based on a modified Paris power law. The threshold values are obtained by rotary and plane bending fatigue tests for WC-Co cemented carbides and Si₃N₄ ceramics. Morever, the thermal effects on the crack propagation life are considered for each material.

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Effects of aging temperature and the casting method, squeeze casting and Pore-Free (PF) method on fracture mechanic characteristics were investigated for aluminum alloy die castings ADC12. The results are as follows. (1) For both methods, the mechanical properties improve and fracture toughness increases due to heat treatment. The tensile strength and the 0.2% proof stress are greatest at the smallest aging temperature of 473K, while the strain to failure and fracture toughness are the lowest. (2) For as-cast die castings, the mechanical properties in the case of squeeze casting are worse than these in the case of using the PF method. On the other hand, fracture toughness of squeeze casting is the same as that of the PF method. (3) For both methods, fatigue crack growth resistance in the low-ΔK region decreases due to the transition from eutectic Si to spheres. (4) In the Paris regime and high-ΔK region, fatigue crack growth resistance increases due to heat treatment and is almost the same for both casting methods.

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Fatigue tests have been performed on a dual-phase stainless steel, SUS 329 J 4L, and an austenitic stainless steel, SUS 304, in order to clarify the crack initiation and early crack growth behavior in 3% NaCl. Crack initiation in room air occurred due to ductile transgranular slip in both stainless steels. In contrast, cracks were generated at the austenite-ferrite phase boundary of SUS 329 J 4L and at the corrosion pit of SUS 304 in 3% NaCl. Early crack growth in the microstructurally small crack region seemed to be enhanced in 3% NaCl for both stainless steels. In larger regions, the crack growth behavior for SUS 329 J 4L was coincident with the da/dN-ΔK_eff relationships for long cracks, while a breakdown in ΔK similitude was found for SUS 304. Environmental effects were less evident for long cracks, except for a slight increase in da/dN at high ΔK region in both stainless steels.

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The lifetime prediction of ceramics has been discussed on the basis of the relationship between the stress intensity facter (K₁) and crack velocity (V). In the present work, the effect of environment on this relationship was studied for two kinds of glass ceramics with different grain sizes. The load relaxation method and controlled load method, which are double torsion (DT) techniques, were used for the determination of the K₁-V characteristics under different environments of air and ionexchanged water. The controlled load method, which is simple and reliable, has been proposed by the authors. We also examined the possibility of failure prediction using acoustic emission (AE). As a result, it was found that at high K₁, V is enhanced by diffusion of corrosive species to crack tips and is also dependent on the amount of water. Crack growth resistance significantly increases with increasing grain size. Also, the AE event rate is quantitatively related to V.

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Effects of screw design and number of screw rotations on fracture mechanisms of fiber-reinforced polypropylene (FRPP) are studied by means of acoustic emission (AE) technique. The fiber length, the fiber orientation angle and the AE characteristics are explained in terms of the apparent shearing stresses on the various number of rotations for B and C screws with shallow groove and deep one. It is clear from specimen molded by a screw with shallow groove that the maximum load is high, the maximum cumulative AE event count and the maximum total AE energy are low on the smaller fiber orientation angle, but the load is low and the AE characteristics are high on the larger orientation angle. It is found from the AE frequency analysis that the fiber breakings dominate the damage modes of specimens molded by B screw, but the fiber debonding and the breaking appear on the specimens molded by C screw.

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As the main causes of strength reduction in welded joints subjected to cyclic thermal transients, attention was given to (1) metallurgical discontinuity in which different deformation responses of base metal and weld metal can result in nonuniform stress and strain across the weldment, (2) structural discontinuity at penetration beads of unfinished welded joints, and (3) degradation of weld metal due to precipitation of dissolved metal. In order to evaluate the first two factors, an elastic follow-up model was applied. Thermal transient strength test results verified that the elastic follow-up model ensures adequate life in elevated-temperature component weldments. The proposed method was proven to be adequate in Type 304 SS, and to have safety margin in FBR grade Type 316 SS.

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In this paper, the problem of an infinite plate containing a circular or elliptical hole under a steady-state point heat source is considered. The analysis is based on the complex variable method using a conformal mapping technique. Stress and displacement fields are obtained as a closed-form solution under the condition of a point heat source applied at an arbitrary point. Several numerical examples are shown in graphical representations.

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In this paper, we present a new scheme for the second-order shape design sensitivity analysis of a two-dimensional elastic problem by the element-free Trefftz method. In the Trefftz formulation, the physical quantities are approximated by the linear combination of the regular T-complete functions. Therefore, direct differentiation of the approximate expressions with respect to shape parameters leads to the regular expressions for the sensitivities. The present schemes are applied to simple examples in order to confirm the validity of this approach.

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The present paper shows the closed-form solutions of a two-dimensional elastic medium containing elastic multi-layered elliptical rings under uniform out-of-plane shear stresses at infinity. This analysis is based on the complex variable method using a conformal mapping technique and analytical continuations, and allows some sliding boundary condition among the elastic rings, inner inclusion and the matrix. Using this solution, we demonstrate the effects of number, elastic properties and sliding parameters of multilayered elastic rings on the distribution of stresses and displacements.

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We describe the applicability of the imaging plate method for determining stress by x-rays of coarse-grained materials. Three kinds of approach were examined. The first one was the standard type which adopted neither the software oscillation method, which is one of the image processing methods used to improve the accuracy of peak determination in the case of spotty diffraction rings due to coarse-grains, nor the mechanical oscillation method, in which the specimen is moved in a plane parallel to the surface of the specimen. The second one used the software oscillation method without the mechanical oscillation method. The third one used both the software and the mechanical oscillation methods. The material used for the experiment was steel of about 0.55% carbon content (JIS S55C). Specimens with grain size of about 5 μm, 50 μm, 100 μm or 200 μm were prepared by heat treatment such as quenching and annealing at different temperatures. From the experiment that used a collimator of 1 mm diameter, it was found that the standard method was useful for materials with grain size less than about 50 μm. Both measurement accuracy and applicable grain size were imporved by applying the second method. Although the limit of the applicable grain size was about 100 μm in the case of the second method, the third method was found to be able to increase the limit, and specimen with grain size of about 200μm was analyzed accurately by the third method. It is possible to measure stresses on materials with arbitrary grain size in principle using both the mechanical oscillation method and IP.

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Bio-active ceramics which have the capability for bonding to bone have been developed as among the most effective implant materials. Because these materials consist of brittle hydroxyapatite their mechanical reliability and workability are much lower than those of metal. Therefore, hydroxyapatite ceramics are used as coating materials. During or after the coating process, cracking and tearing often occur in the coating layer of the implant. These defects are caused by the residual stress in the vicinity of the coating interface. It is important to evaluate the residual stress in this region. The purpose of work was to present a method for measuring simultaneously and nondes tructively three-dimensional distribution of residual stress in both the hydroxyapatite coating layer and the titanfum substrate, using polychromatic X-rays. The steep stress gradient in the coating layer and the increase in tensile residual stress on the surface of the substrate were confirmed.

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A direct method of measuring bridging stresses using a double notched plate (DNP) specimen is developed. Bridging stresses are measured form the stable fracture of the DNP specimen using a bridging stabilizer developed in this study. The opening displacement of fracture surfaces can be evaluated from the deformation of the bridging stabilizer without the need for microscopic measurement. As an example application, the bridging stresses of polycrystalline alumina are measured under monotonic load. The bridging characteristics measured using the present method are compared with those obtained by other methods. An approximate expression of the bridging characteristics is shown.

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The constitutive equation based on the multiple strata plasticity model proposed in the previous paper contains a term involving the tensor Q describing the activation state of the slip systems in polycrystalline metal. In this work we aim to clarify the characteristic of Q under the proportional and nonproportional loadings. To describe visually the complicated stress state a two-dimensional stress plane is newly introduced by applying each magnitude of normal and shearing deviatoric stress tensors. The stress trajectory can be expressed in terms of two angle parameters, ■ and θ, on the stress plane. All of the quantity of Q can be given by the simulation calculations under various loadings with a virtual specimen of polycrystalline metal. Each component of Q can be systematically related to the deviatoric stress using a specific function of ■ and θ. In addition, it is suggested that the hardening characteristic of the slip system may be presumed analytically by comparing the experimental results with the constitutive equation.

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A boll heater is widely used for tightening large structural members that use bolts with large nominal diameters, where a high axial force is required. The actual tightening operation with the bolt heater is usually done by skilled workers, since it is fairly difficult to control the axial force with high accuracy. In this study, the fundamental characteristics of the method are clarified by experiment and analysis, and a numerical procedure for evaluating the tightening process is proposed using FEM as an elastic contact problem in the transient temperature field. The relationships between the heating operation and the axial force are obtained for various design factors. In addition, the effects of grip length of fastened plate and nut rundown torque on axial force are also discussed. The validity of the numerical method proposed here is ascertained by comparing with experimental results.

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Deformation around a concavity created by indentation of a conical indenter in an ultramicrohardness tester is analyzed using FEM computer simulation. Effects of indenter tip radius, work hardening in material and indenter shape on concavity shape and hardness from concavity depth both under loading and load-free conditions are examined. The results obtained are as follows. (1) Concavity in high work hardening material is of the sinking in type including concavity rim. On the other hand concavity in low work hardening material is of the piling-up type in which the rim rises above the material surface. Existence of indenter tip radius makes the inclination marked. (2) The lower the work hardening of material is, the broader the plastic zone around the concavity created by a conical indenter spreads parallel to the surface and the higher the peak value of the plastlc strain near the tip of the indenter. Existence of indenter tip radius makes the plastic zone large and the peak value of the plastic strain around the bottom of concavity small. (3) Indenter shape influences concavity shape. However there is almost no difference in the depth of plastic zone. (4) Correction of errors at the indenter tip, which is effective to Vickers and triangular pyramid indenters, can be applied to a conical indenter.

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A numerical method is given for solving rolling contact problems with traction force and differential slip. The theoretical basis of differential slip is described in a manner such that the physical meanings of the problems can be understood directly. Based on the slipping velocity, the amount of wear was calculated. The following results were obtained. (1) The component of frictional pressure perpendicular to the rolling direction never vanishes, so the contacting bodies are microscopically slipping on the area neighboring the trailing edge, including the pure rolling line. Proceeding along the trailing edge, the sliding direction changes gradually from -90°to +90°. (2) The shape of the contact area of the upper body is slightly different from the one of the lower body because of the small difference in elastic deformation at the leading edge.

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We consider how to predict defect sizes, depth and width, from wave forms of the leakage flux obtained by the magnetic leakage flux method. Measurements of leakege flux were carried out using plane specimens with various values of depth and width of the defect and the lift off which is the distance between the specimen surface and the probe, and a quasi-weld reinforcement specimen. The absolute value of maximum leakage flux was affected by the plate thickness or the shape of reinfo cement not but by the defect shape. Therefore the absolute value method used by many researchers is not suitable for estimating the sizes of defect in a joint in which the average flux is not known. However, the wave form of leakage flux is almost unaffected by factors other than the defect sizes. The depth and width of the defect are estimated by the proposed method that the two feature points of the wave form, for example the maximum leakage flux and one-tenth of the maximum value, of experimental value are combined to the above feature points of the wave form calculated from the dipole modeling.

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In this paper, an effective boundary element method with high accuracy for an axisymmetrical electromagnetlc field of a layered tube is developed. Quasi-static axisymmetrical Maxwell equations are represented by a vector potential satisfying Coulomb gauge and discretized with a standard BEM. The analytieal relationship between a magnetic field and a vector potential of an axisymmetrical eiectromagnetic field of a layered tube is derived using modified Bessel functions I₁ (z) and K₁ (z) and represented by products of transfer matrices. The discrete Fourier transform theory is applied to the analytical relationship, and the result is combined with the standard BEM. The distinct advantage of this method is that the discretization is not necessary in a layered tube. It is found that the length of the element which combines the standard BEM with the analytical relationship has upper and lower bounds in this method, because the discrete Fourier transform theory is based on the Shannon sampling theoren and a low-pass filter relates a magnetic field and a vector potential on the inner surface of a layered tube. The accuracy of this method is demonstrated by solving some example problems.

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In the previous papers, a method is proposed to obtain microscopic definitions for internal forces of continua such as stress, higher-order stresses and heat flux. In the present paper, the relationship between higher-order stress power and heat flux is discussed, expressing the 1st law of thermodynamics with microscopic quantities in mesodomain. Then an energy equation is obtained by dividing the kinematical quantity of an atom into macroscopic and thermal motion. It is clarified that heat flux in the energy equation is equivalent to higher-order stress power since heat flux is regarded as the amount of each order power due to higher-order stresses. When higher-order stress power is separated from heat flux in the energy equation considering this equivalence, the value of heat flux decreases. These expressions of heat flux and higher-order stress are useful to obtain macroscopic quantities from numerical solutions calculated by the molecular dynamics.

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In the present study, the influence of temperature on impact damage in carbon fiber reinforced plastic (CFRP) laminates was investigated experimentally. Carbon fiber/epoxy, carbon fiber/toughened epoxy and carbon fiber/PEEK having a stacking sequence [0⁰_n/90⁰_n]_SYM were used as specimens. Damage was generated by the collision of a steel ball under temperature conditions ranging from -30°C to 180°C. Delamination areas in the specimens were measured using an ultrasonic microscope and the surfaces of the delamination were observed by SEM. The results revealed the total delamination areas to be proportional to the impact energies for all specimens except for the specimens suffering impact damage at low temperature, and the delamination areas decreased with increasing temperature. The development of the delamination area can be explained in terms of the thermo-viscoelastic behavior of CFRP. Shear deformation between the layers increases with increasing temperature prior to the generation of damage, since the length of hackles on the delamination increases with temperature.

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We describe a numerical shape optimization method of continua that minimizes maximum local measure such as stress and displacement. A solution to this min-max problem subject to volume constraint is proposed. To avoid impossibility of differentiation, local functionals are transposed to global integral functionals using the Kreisselmeier-Steinhauser function. With this function, a multiple leading problem is also transposed to a single loading problem. The shape gradient functions which are applied to the traction method are theoretically derived using the Lagrange multipliers and the material derivative method. Using the traction method, the optimum domain variation to decrease the objective functional is numerically and iteratively determined that maintaining the smoothness of the boundaries. The calculated results of 2D and 3D examples show the effectiveness and practical utility of the proposed method for min-max problems in shape designs.

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The end-bells of a turbo alternator consist of an end-bell and a supporting ring. Their purpose is to hold together the coil ends emerging from the rotor body and to prevent them from shifting. During operation, an end-bell tends to spread outward due to centrifugal forces, and then slip or play develops at the seating. Furthermore, as the speed decreases, sticking occurs there. We discuss the contact mechanics of end-bell hysteresis behavior. First, it is shown experimentally that micro-slip can occur on shrink-fit surfaces during load cycles. Next, this contact behavior and micro slip are investigated using a 3-dimensional FEM. The numerical predictions of hysteresis-behavior agree well with experimental results. The stick-slip thresholds are functions of design parameters such as interference fit and friction coefficient. This technique can be used to improve the balance design of the rotors.

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Investigation of the behavior of an automobile seat subjected to an impact load is important to improve safety. The following three subjects on the design of the seat frame are described. First, in order to understand the fundamental impact behavior of a seat frame, the characteristics of impact behavior were studied through experiments carried out under various impact conditions. Second, using an explicit finite element method, a structural analysis method for the simulation of impact behavior was investigated. This analysis method was shown to be useful by comparing its results with the experimental results. Finally, the influence of design parameters of the seat frame on impact behavior was investigated. There has been a growing demand that the structure of the seat should be designed rationally by evaluating correctly the influence of design parameters upon such characteristics as strengh and flexibility. The authors proposed a statistical optimization method that consists of two steps : effectivity analysis and mathematical programming. In this paper, the effectivity analysis was applied to the seat frame, and the applicability of the effectivity analysis was confirmed by comparing with the experimental results.

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In this paper, the discrete element method (DEM) is applied to analyze the impact fracture of laminated glass, which is considered to be a continuous body with interlayered polyvinyl butyral (P. V. B.). A laminated glass beam, with both ends fixed under a lateral impact load is considered, and the proposed method is applied to simulate the impact fracture behavior, until penetration. From the numerical analysis it is obvious that the optimum adhesive strength between the PVB and the glass, is the lowest adhesive strength, such that there is no fracture in the adhesive layer when the beam is peaetrated. By changing Young's modulus of PVB (hence changing the tensile strength) we can show that considering both the penetration energy and the volume of the broben glass, the optimum Young's modulus of PVB is a maximum in the region where the penetration energy is sensitive to the Young's modulus of PVB.

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A computer program was developed for continuous simulation of the dislocation density in a bulk single crystal during the Czochralski (CZ) growth process. In this computer program, the shape of the crystal melt interface and the temperature in a crystal at an arbitrary time were determined by linear interpolation of the discrete results that were obtained by heat conduction analysis of a CZ single crystal growth system. A dislocation kinetics model called the Hassen-Sumino model was used as the constitutive equation. In this model, the creep strain rate is related to the dislocation density, and this model extended to the multiaxial stress state was incorporated into a finite element elastic creep analysis program for axisymmetric bodies. Dislocation density analyses were performed using this computer program for Si, InP an GaAs bulk single crystals of about 8 inches diameter. The present analyses indicate a W-type dislocation density distribution across the diameter in InP and GaAs single crystals that can be observed in actual CZ growth of InP and GaAs.

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Printed circuits are very important for the integration of electronic device fabrication. Each year, finer and more multilayer printed circuits are used. It is necessary to form a finer photoresist pattern before patterning the finer circuits, and several copper subtrate surface treatments are generally used to improve photoresist adhesion strength. However there is no suitable method for estimating adhesion properties of such surfaces. An attempt is made to apply the "surface roughness factor"(SRF, specific surface area of a solid) as a parameter to estimate surface conditions for adhesion. In this study, sultable equipment is made to measure the adhesion strength of the photoresist and the SRF of the copper substrate. It is also, confirmed that the SRF is a good parameter for estimating adhesion properties of surfaces, and there is a quantitative relationship between the adhesion strength of photoresist and SRF of the substrate.

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Vertebrae are typical regions where metastasis of bone cancer is apt to occur. Total en bloc spondylectomy has been performed to remove a lumbar vertebra with a tumor. In this operation, the vertebra is replaced by an artificial vertebra fixed to higher and lower vertebrae by instruments from the back. Mechanical stress and deformation of five lumbar vertebrae are analyzed for case of a preoperation and a postoperation by using special FEM for a multilayer structure in this study. We consider two loading conditions corresponded to upright pose and stooping pose to the lumbar vertebrae models. An equivalent distributed load on the top surface of the first lumbar vertebra is giver for the upright pose. A front inclined load is given for the stooping pose. The main results obtained as follows. (i) Mechanical stability is improved in the postoperation case. (ii) A Higher stress part suggested from the FEM result agrees with a part possessing a possibility of fracturing clinically. (iii) One cause of loosening of the top screw is the stress variation with change of the pose between an upright and a stooping. (iv) The top and the bottom screws may break due to fatigue.

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