Although finite element method (FEM) is effective in solving partial differential equations in numerical analysis, the creation of the mesh data has and will become a very burdensome process. Therefore, meshless or element free method, which require no element or grid, are believed to be effective and efficient. Since only the nodal data are necessary, it is belived that CAD/CAE seamless system can be created using these methods. Furthermore, because of the developments made in the field of multi-media, the processing of digital image data has become very simple tasks. With these method, it is believed that the implementation of these digital images to the numerical analysis is easily achievable. This paper will discribe a prototype of such system developed by the authors, based on the element-free Galerkin method (EFGM) 2D elasticity problems. Mainly the preprocessores, where the data is constructed from CAD and digital image data, will be the main focus of this paper.

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Free Mesh Method (FMM) is a kind of meshless method modified from the finite element method. In FMM, the elements are created around each node only in a local manner after the set of nodes is provided, thereby the processes from the creation of the local elements to the construction of the local equations being conducted on a node-by-node basis. In this work, we applied FMM to elasto-plastic dynamic analysis using explicit time integration. Some techniques to apply FMM to this problem are described, and the present FMM is compared with the conventional finite element method to show its feature. As an illustrative example, a simple two-dimensional dynamic problem is analyzed.

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In this paper, a new method to produce the functional continuum is proposed. The method is a topological optimization technique based on the function of a continuum and is composed of three steps. First, an initial mechanism model, which conforms to the given function, is determined using only some levers and supports. The mechanism model is changed to a framed structure as Rahmen model in the second step. The cross-section and length of members in the framed structure are optimized to maintain the original design requirement. In the final step, the framed structure is changed to the functional continuum using some well known shape optimization techniques. This method is applied to two problems of functional continuum. The first problem is to produce the continuum as orthogonal displacement transducer. The second problem is to produce the continuum having a bi-axial stress field under a uni-axial loading. From the results on these problem, it is obvious that the proposed method is very useful to produce the functional continuum.

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In this paper, a simple and efficient finite element formulation and the numerical method to solve the contact-impact behavior of a geared rotor system coupled with rotational, lateral and axial vibrations between gears at high rotational speed are given. The equation of the motion is derived and solved iteratively during each time increment until the unbalanced force becomes small enough within a specified tolerance. Based on the present method, a computer program, GRINDER, has been developed to solve the contact-impact behavior of a geared rotor system coupled with the rotational, lateral and axial vibrations. Numerical examples are demonstrated to show the validity and effectiveness of the proposed method.

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An approach for simulating microscopic densification behavior of powder particles in compaction using a finite element method is proposed. In this method, the contacts between powder particles during the compaction are detected, and plastic deformation of the particles is calculated by the finite element method for porous metals. The finite element mesh is generated by connecting the centers of the contact particles. It is assumed that the finite elements are porous metals having an average relative density calculated from the volumes of the powder and pore inside the element. The elements are classified into the triangular and quadrilateral ones used in the conventional finite element methods and a linear one for the simple compression. The accuracy of the stiffness for plastic deformation of the particles is improved by applying the finite element method. The calculated plastic deformation of powder particles in plane-strain compaction is compared with that for a model experiment using aluminum rods.

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This paper deals with a theory of ply-cracking damage on 90° and 0° plies in cross-ply laminate and its application to finite element method. An energy approach is extended to predict the initiation and evolution of ply-cracking damage on 90° and 0° plies and the corresponding nonlinear stressstrain behavior of the cross-ply laminate under multi-axial in-plane loading. In this approach, the stress and strain conditions for the progressive damage are determined by equating the decrease in potential energy to the released energy, where the former and latter are estimated from the stiffness reduction due to ply-cracking damage and from the mixed-mode critical energy release rate for cracking of unidirectional ply, respectively. This approach provides us with the constitutive relation of cross-ply laminates including the progressive ply-cracking damage. This theory is applied to the finite element method in order to analyze the ply-cracking damage and stress/strain distributions of the structures made of cross-ply laminates. As an example, finite element analysis is carried out on the seven kinds of CFRP cross-ply laminates with a circular hole. The numerical results show that the transverse cracking damage in 90° ply is widely spread out on the ligament of the plate, and the splitting damage in 0° ply extends in the longitudinal direction from the edge of the hole. The details of the damage evolution around a circular hole in CFRP cross-ply laminate dapend on the stacking lay-up.

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In the present study, an interlaminer fracture toughness of orthogonal CFRP (carbon fiber reinforced plastic) under mixed mode is evaluated using DCB (double cantilever beam), ENF (end notched flexure) and ELS (end loaded split) specimens. The fracture toughness of the delamination is determined by complex stress intensity factors which are defined on the interface crack between dissimilar orthotropic laminates. The complex stress intensity factors are extrapolated from stress distribution around the crack tip. Two dimensional deformation of the CFRP specimens is calculated numerically by the boundary element method with experimental results. It is shown that the fracture toughness of the orthogonal CFRP laminate depends on mode ratio of the stress intensity factors K₁ and K₂. The criterion of the delamination growth and occurrence of the transverse crack are discussed from a standpoint of the mode dependency of the fracture toughness.

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Hydroxyapatite (HAp) is one of the most effective biomaterials used in an artificial bone and a dental designed implant. Since its mechanical reliability and workability are much lower than those of metal, it is often used as a coating material. However, cracking and delamination at the coating interface are induced by the residual stress which occurs in the coating process. In our previous report, the steep stress gradient in the coating layer and the increase in tensile residual stress on the surface of the substrate were obtained using the polychromatic X-ray diffraction. Therefore, an additional intermediate layer between the coating and the substrate material may decrease the residual stress in the coating layer. In this work, we describe the method to measure nondestructively three dimensional residual stress generated in the coating implant with the intermediate layer, using the polychromatic X-ray diffraction. As a result, the compressive residual stress in the coating layer of the hydroxyapatite coating titanium implant with the titania intermediate layer, made by atmospheric plasma-spray processing, was smaller than that of the implant coated only with hydroxyapatite.

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In order to examine the effect of crystal grain size on the fatigue behavior of glass ceramics, cyclic fatigue tests were carried out by four-point bending load under both environments in air and water. A single crack and three collinear cracks were introduced on the surface of plate specimens by Vickers micro hardness indentation. The crystal grain size of the glass ceramics in this work was about 1μm, and it was increased from about 0.05μm used in previous work. As a result, the time-to-failure to the cyclic fatigue of the glass ceramics with a large crystal grain size obviously did not decrease by the effects of water environment and the multiple surface cracks, comparing with that of the glass ceramics with a small crystal grain size. Therefore, the interaction between multiple surface cracks may not be effective sufficiently for glass ceramics with a large crystal grain size. In addition, the fatigue strength of the glass ceramics increased with increasing crystal grain size. These facts mean that a dominant crack propagates along crystal grain boundaries.

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To investigate the "size effect" of rotating bending fatigue test are carried out on solid bar specimens with various gage lengths, that is, the length of the parallel part, and the same cross section of S35C steel, SFA55 steel and AC8A aluminum alloy. Statistical test of significance about the effect of gage length on fatigue limit was carried out by using the mean and the standard deviation of fatigue limits obtained by an up-and-down method. The result of the statistical tests show that a significant difference exists among fatigue limits of each gage length. Experimental values of the size effect are coincide with the calculated value by means of the assumption that strength of micro defect in material belongs to Weibull distribution. In the experimental results, shape factor : m of Weibull distribution is 30∼80 and depends heavily on the material and metallurgical structure.

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Rotating bending fatigue tests were carried out for an 18%Ni maraging steel to investigate the effect of shot peening on the fatigue strength. The fatigue strength increased markedly by the shot peening. The increase in the fatigue strength due to the shot peening depended on the shot size and the stress level. Fracture mode changed from the surface fracture in the short life region to the interior fracture i. e. fish-eye fracture in the long life region. And in the middle life region, both cracks initiated from the surface and the inside of material in dividually coalesced and lead to the final fracture. These results were discussed from the effect of shot size on the surface roughness and the depth and magnitude of compressive residual stress and work hardening.

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The fatigue strength and the nonpropagating crack of welded joint have been investigated experimentally under the condition of bending load. Simulated specimen was given the characteristic microstructure and grain size of welded joint. Though the surface length of nonpropagating crack was greater than about 100μm, the depth of nonpropagating crack was less than about 40μm and existed in the first grain size. The stress intensity factor at the tip of nonpropagating crack was used for predicting the fatigue strength of welded joint. The predicted values almost agree with the experimental data.

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Behavior of fatigue strength and fatigue crack growth were investigated in thin sheet of titanium alloys, in order to clarify the influence of microstructure, stress ratio, and anisotropy. Fatigue tests were carried out with α+β titanium (Ti-6Al-4V) and β-rich α+β titanium (Ti-4Al-3V-2Fe-2Mo) alloys after the heat treatments of furnace cooled at superplastic forming temperatures 1173 K and 1073 K, and as received. The main results are summarized as follows ; 1) The fatigue strength of heat treated both materials were lower than as received. Main reason of fatigue strength being lower by heat treatment was caused by rearrangement of quantitative proportion of the β phase to α phase. 2) The fatigue crack growth rate of both materials were almost independent of the anisotropy and texture, regardless of the heat treatments condition to be superplastic forming temperature. 3) The fatigue crack growth rate of Ti 6A1-4V alloy was lower than that of Ti-4A1-3V-2Fe-2Mo alloy because the fatigue crack growth went zigzag direction by large grain size α and resistance of crack propagation was increased by the prior β phase mostly transformed from aciculate α.

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Temperature fluctuations in power plants may cause thermal fatigue in structures, In order to maintain integrity of structures, the thermal fatigue life has to be evaluated including high cycle fatigue conditions on which few investigation has been performed so far. In the last study, a facility for high cycle thermal fatigue testing in pure water was developed. To clarify the high cycle thermal fatigue crack initiation behavior of type 304 stainless steel in pure water environment, high cycle thermal fatigue tests were conducted using the developed facility for various water temperature fluctuation frequency and water temperature fluctuation range in this study. The thermal stresses induced on the labyrinth corner of the cylindrical specimen were analyzed by FEM. The heat transfer coefficient experimentally evaluated using the thermal fatigue testing facility was applied to the analysis. Thermal fatigue cracks were initiated at the corner of the labyrinth for the stress amplitude and over 294 MPa. On the other hand, the mechanical fatigue crack initiation lives were derived from the mechanical fatigue of type 304 stainless steel. It was demonstrated that the number of cycles to thermal fatigue crack initiation agreed with that of the mechanical fatigue crack initiation when the fictitious stress amplitudes were identical.

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The effects of molecular weight and orientation on crack propagation property of polyimide (PI) are investigated. The specimens which have four kinds of molecular weight (Mw) from 2.5×10⁴ g/mol to 3.8×10⁴ g/mol are prepared. The crack propagation resistance increased with increasing Mw. The discontinuous crack growth (DCG) bands were observed on the fracture surfaces except for that of the specimen with the highest Mw. The reason that the DCG disappears for high Mw is attributable to the decrease of ductility. The width of DCG bands is almost constant until transition of DCG to continuous crack growth. The critical craze stress for cyclic loading given by Dugdale model decreases with the increase of Mw since the damage of the craze region is accumulated until breaking down. From the results of miniature CT specimens, the crack propagation resistance increased when the direction of crack propagating was perpendicular to the orientation of PI molecular chains.

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In this study, generalized stress intensity factors K_{I, λ1} and K_{II, λ2} are calculated for a V-shaped notched round bar under tension using the singular integral equation of the body force method. The body force method is used to formulate the problems as a system of singular integral equations with Cauchy-type or logarithmic-type singularities, where the unknown functions are the densities of body forces distributed in an infinite body. In order to analyze the problems accurately, the unknown functions are expressed as piecewise smooth functions using two types of fundamental densities and power series, where the fundamental densities are chosen to represent the symmetric stress singularity of 1/r^1-λ₁ and the skew-symmetric stress singularity of 1/r^1-λ₂. Then, generalized stress intensity factors at the notch tip are systematically calculated for various shapes of V-shaped notches.

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In this paper a singular integral equation method is applied to calculate the variation of stress intensity factors along the crack front of a 3 D oblique semi-elliptical surface crack when the whole of the crack surfaces are in contact each other. The body force method is used to formulate the problem as a system of singular integral equations. In the numerical solutions unknown body force densities are approximated using fundamental density functions and polynomials. The calculation shows that the present method yields rapidly converging numerical results and smooth variation of stress intensity factors along crack front even when the inclination angle between the crack and the free surface is small. The mode II and mode III stress intensity factors are shown when an inclined edge crack is subjected to compressive residual stresses or Hertzian contact loads with varying the inclination crack angle and friction coefficient.

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Thermal stress distribution of adhesively bonded pipe flange connections subjected to heat conduction in steady state are analyzed by using the thermoelastic displacement potential and Michell's stress functions based on the axisymmetrical theory of elasticity. In the analysis, pipe flanges, hubs of pipe flange and an adhesive are replaced by finite hollow cylinders, respectively. In the numerical calculations, the effects of the ratios of linear thermal expansion coefficients, Young's moduli between the pipe flange and the adhesive layer and the adhesive thickness on the stress distribution at the interface between the flange and the adhesive layer are examined. As a result, it is seen that the thermal stress (compressive) at the inner and the outer surfaces of the adhesive layer increases with a decrease of Young's moduli ratio, the linear thermal expansion coefficient ratio and the adhesive thickness. In addition, stress analysis by using FEM (Finite Element Method) was also carried out. Fairly good agreement is seen between the numerical and FEM results. The characteristics are compared with those of the connections with gaskets. It is found that the stress at hub of the joint with adhesive is smaller than that of the joint with gasket.

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This paper presents a numerical technique to analyze one-dimensional steady-state and transient temperature distributions in a plate of functionally graded ceramic-metal based materials (FGM) in relation to both the temperature-dependence and continuous/gradual variation of the thermo-mechanical properties of the FGM. The FGM plate is assumed to be in steady state of temperature gradient initially, suffering high temperature on the ceramic surface and low temperature on the metallic surface associated with its in-service environment. The FGM plate is then cooled on the ceramic surface of the plate rapidly by cold air. The transient temperature and related thermal stresses in the FGM plate are analyzed numerically for a model of alumina-nickel based FGM. The analytical technique of temperature distribution proposed here is simple and applicable widely compared with the previous methods proposed by other researchers.

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This paper considers determination of individual stress components from the sum of the principal stresses obtained experimentally by the thermoelastic stress analysis. The stress separation problem is devided into two parts : (1) an inverse problem to estimate the unknown boundary values from the knowledge of the sum of the principal stresses inside the analysis region, and (2) a forward problem to compute the stress components inside the analysis region based on the estimated boundary values. These two problems can be formulated and solved by the BEM. As the inverse problem is often ill-posed, two techniques are adopted so as to attain an accurate result. One is preprocessing of experimental data, that is filtering based on the compatibility equation. The other is regularization of the inverse problem by Tikhonov's method with Hansen's L-curve method. The effectiveness of developed method is verified by applying it to an experimental data. The effect of configuration of the analysis region on the accuracy of stress separation is also discussed.

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Magnetostriction curves were measured for plastically deformed steel specimens at various levels of applied stress. It is known that the plastic deformation changes the elastic and magnetic properties, which induces the significant error in the nondestructive stress evaluation by ultrasonics and magnetics. We have already proved that the maximum value in the magnetostriction curve can be used in the nondestructive residual stress measurement in elastically deformed steel. In this study, to reveal the applicability of the maximum magnetostriction method to plastically deformed samples, we measured the stress dependence of the maximum magnetostriction for plastically elongated specimens. It was predicted that the residual compressive stress was introduced in the deformation direction at the surface of the specimen. The evaluated stresses were compared with those by some other methods, showing that the magnetic anisotropy supports the results by the maximum magnetostriction method.

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At some value of the elongation a loss of uniquencess of the uniaxial state can be expected signaling the onset of necking. A problem of some interest in the theory of plastic instability arises from considering a tensile test conducted on a metal specimen whose lateral surface is simultaneously subjected to uniform fluid pressure. The question is this : What effect does the fluid-pressure have on the amount of uniform elongation that is possible before the onset of necking? The effect of hydrostatic pressure on the necking of plastic solids has long been a point of controversy. However, Hill first proved that lateral pressure does not affect the tensile necking. Hill⁽⁴⁾ used his sufficient criterion for unique solution in his proof, and in the discussion of specimen subjected to lateral pressure p the stress σ_ij appearing in his criterion was replaced by σ_ij+pδ_ij. This replacement cannot be complied with because the stress σ_ij is introduced from the definition of nominal stress rate. Therefore, his argument is unsatisfactory. We proposed recently criterion for multiplicity, and in applying the criterion it must be emphasized to consider the condition of load instability which can lead the state of specimen to active eigenstate. In this paper we apply criteria of multiplicity and load instability to the discussion of tensile instability, and make a detailed study of their relationship in evaluating the onset of necking. The result shows the strain at which necking occurs dependent on hydrostatic pressure.

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In order to understand nucleation mechanism of diamond film fabricated by chemical vapor deposition method on silicon substrate, molecular dynamics simulation of a process forming silicon carbide layer on amorphous region of silicon substrate surface is conducted. The fact that silicon crystal surface scratched by various grit such as diamond contains many dislocations and amorphous region has been known, and silicon carbide layer as the interface between diamond film and silicon substrate is confirmed by high-resolution transmission electron microscopy. In this paper, molecular dynamics simulation using the Tersoff potential and temperature control method with introducing cut-off temperature for simulation has been carried out for 200 ps, where 4200 silicon atoms and less than 1000 carbon atoms in the cell are considered. The action of carbon atoms and silicon substrate in the simulation are shown, so one of processes forming silicon carbide layer on amorphous region of silicon substrate surface is found.

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New method used plasma jet treatment for improving the interface shear bonding strength between SUS 304 stainless steel and epoxy resin have been investigated comparing with traditional chemical etching surface treatment. Argon gas was found to create a desirable rough surface and nitrogen gas to cause hard surface by the chemical reaction. Plasma jet treated SUS 304 specimens embeded in the epoxy resin all showed higher interface shear bonding strength due to the anchoring effect. Based on these facts, a two step plasma jet treatment has been tried and a significant improvement in the interface shear bonding strength obtained.

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In order to study dynamic mechanical properties of the aluminum alloys A1 6061-T4 and A1 7075-T6, plate impact experiments with PVDF (Poly Vinylidene DiFluoride) stress gauges and the VISAR (Velocity Interferometer System for Any Reflector) were conducted using a shock gun system. From the experiments, we obtained the Hugoniot curves, the Hugoniot elastic limits and the spalling strengths of the alloys.

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In the case of fixing the tower crane on the base at the building site, the fastening method where the frame is held down by a beam called "Kanzashi" and bolts are inserted in it is widely used. This "Kanzashi" often deflects because of insufficient rigidity when bolts are fastened. This paper describes the results of an experiment employed a crane frame model, derivation of a practical formula based on strength of materials and comparisons of the theoretical and experimental values. The results obtained are that the force radio became smaller and the bending force ratio became larger with decreasing the thickness or increasing the bolted distance. The theoretical values agreed well with the experimental values.

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Novel biodegradable coronary stents were implanted into left anterior descending arteries of 25 dogs and 7 pigs by using 8 Fr Guiding catheters. These stents 3 mm in diameter and 15 mm in length are knitted pattern made of poly (glycolic acid) monofilament of 0.120 mm in diameter. Follow-up coronary angiography was performed and the standard optical microscope observations of the cross sections of the stented segments were carried out 2 and 4 weeks after implantation. All of the stents were successfully implanted. Patency of stented arteries were wide enough and no acute closure was observed immediately after implantation. Percentage stenosis drastically increased to nearly 80% and then leveled off after 2 weeks in the case of pigs, while it increased rather gradually to 25% and then leveled off after 4 weeks in the case of dogs. It is considered that the foreign body reaction is more significant in pigs resulted in the remarkable neo-initimal hyperplasia. PGA stent has already lost its mechanical properties to hold the arteries from the inside due to the rapid degradation by this time and crushed into the lumen of the arteries. This crushed stent brings high percentage stenosis. These results suggest that it is necessary to chose polymer for the stent with a suitable degradation rate in order to achieve a low percentage stenosis.

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