A new stochastic boundary element method for analyzing the corrosion of underground structure was developed. In case of analyzing the corrosion of underground structure buried in soil which electric conductivity and polarization characteristics are changing along time, it Is necessary to consider about the stochastic character of these unstable condition (conductivity and polarization characteristics) . The non-linear relationship between unknown variables and these unstable condition was linearized by Taylor series and, the mean and covariance of unknown variables are estimated. In order to demonstrate the effectiveness of the method, the simulation was performed and the result was compared with conventional Monte Carlo method and the field experimental result. A computer simulation of the identification is performed at first with a measured potential by using the Kalman filter which stochastic model was considered with the proposed method.

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A bolted joint is subjected to high stress concentration at the thread root because of Its complicated geometry involved. Plastic regions are produced around the bottom of thread root, even under relatively low axial bolt force. It is predicted that the plastic deformation thus produced might affect such important mechanical behaviors of bolted joint as load distributions along threads, the relationships between axial bolt force and bolt elongation, etc. In many practical applications, bolts are tightened with considerably high clamping force, especially when tightening critical structures. Thus, it is considered that numerical studies taking the effects of plastic deformation Into account are extremely important. However, many previous studies have only dealt with a bolted joint under pure tension. When tightening bolted joints with torque control method, shear stresses are generated in addition to the tensile stress. In this study, mechanical behaviors of bolted joint during the tightening process with torque control method are analyzed by FEM as an elasto-plastic contact problem, where three-dimensional analysis in conducted employing two dimensional model with each node having three degrees of freedom.

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Meshless method is a new numerical analysis scheme and researches for many analysis models have been conducted in recent years. We have applied the element free Galerkin method (EFGM), the meshless method presented by T. Belytschko et al. in 1994, to analyze membrane structure with cable reinforcement. To model the sliding cable on membrane, the arbitrary Lagrangian-Eulerian (ALE) method is adopted. By using ALE formulation, deformation of membrane and sliding between cable and membrane can be represented as different displacement components. In this paper, an ALE-EFGM formulation using the convected coordinate system for geometrically non-linear analysis is presented. Finally, the proposed method is applied to a simple analysis of membrane structure with sliding cable and its validity is demonstrated.

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A design support CAE system was developed to reduce weight and design time of box structures. This system assists users in optimizing box structures by using a genetic algorithm (GA) . GA is known to be excellent in searching for globally optimal solution, but it requires a large number of generations. This paper proposes an effective method that makes possible to produce new structures by exchanging the parts in a box structure for differently shaped parts in a part database, and by moving parts of the structure to other positions. We used this system to optimize the stiffeners in a box structure and evaluated its convergence.

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This paper presents a new efficient genetic algorithm for truss structure optimization. In many optimum design problems, values of design valiables are real numbers. We have proposed the "Center Neighborhood Crossover (CNX)" for real coded genetic algorithms. CNX is a powerful tool for function optimizations. Since it is uncertain that these operators are able to work for practical design problems efficiently, it is necessary to examine some crossover operators for practical use. In the present study, we verified and compared the performance of several crossover operators using benchmark functions. Furthermore, we tried to optimize a truss structure problem using these operators. By considering the results mentioned above, we developed the "two-stage method" for truss structure optimization. This method bring us the efficient search and the high-accurate optimum solution.

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In performing structural design or demonstrating the reliability of electronic devices, it is necessary to take various scatters into consideration which are induced in the load assessment, material characteristics, stress analyses and manufacturing. Therefore, a new method for probabilistic reliability design for electronics packages is proposed in this paper. In this method, firstly the probability distributions of the characteristic values such as stress values are calculated by combining stress analysis, response surface methodology and the Monte Carlo method. Consequently, the fracture probability can be derived by comparison of the probability distributions with the design criteria. Secondly, the probability on many assumptions can be updated using a new method based on Bayes theory for the purpose of estimating the reliability of the packages more accurately in combination with actual data or reliability tests. The new method was applied for the structural design of flip-chip BGA packages. The results of the application fro flip-chip BGA package design indicate that the new method is useful for the structural reliability design.

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This paper proposes a novel approach to the determination of structural shapes that satisfy the requirement for high stiffness, lightweight and strength. In this method, a basic shape is derived in the first phase by the FEM-based topology optimization, and then, in the second phase the final shape is determined by the BEM-based fully stressed design. In the second phase, the shape is iteratively changed in such a way that the von Mises stress of all the material elements, σ_i, (x_i), lies within an allowable stress region defined as σ_lower <__= (x_i) <__= σ_upper. By making an appropriate choice of σ_lower and σ_upper, this algorithm allows us to derive a lightweight structural shape with high stiffness and enough strength. As an example, this method was employed for the determination of the shape of a hook.

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This paper presents a unified analysis of plate bending problems due to classical plate theory containing an ellitpic hole or elliptic inclusion under singular point moments and point discrepancies of deflection and slope as well as applied moments and torque at infinity. The analogies existing between the mathematical formulations of transverse bending of elastic plates and two-dimensional stress problems are used for analytical treatments. Some numerical examples are shown in graphic representation.

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The behavior of the interface between a parent phase and a martensitic phase and the lateral to longitudinal strain ratio due to the stress-induced martensitic transformation (SIMT) were investigated in the both regions of superelasticity (SE) and shape memory effect (SME) in TiNi shape-memory alloy wires through the tensile test. The Interface which appears due to SIMT during the loading process and its reverse transformation during unloading starts at both ends of a wire in the gripping parts and thereafter propagates towards the central part. When the two interfaces meet, SIMT completes. The behavior of SIMT under cyclic SE deformation does not change during cycling. The behavior of SIMT in the region of SE is similar to that in the region of SME. The lateral to longitudinal strain ratio due to SIMT and its reverse transformation is 0.43∼0.46. Poisson's ratio in a parent phase, a rhombohedral phase and a martensitic phase is 0.33∼0.34.

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Two kinds of thermal barrier coating films with 8 wt% yittria-zirconia were made by atmosphere plasma spraying (APS film) and by low-pressure plasma spraying (LPS film). These films were removed from substrates. The mechanical and X-ray elastic constants of the APS and LPS films were measured by tensile and bending deformation. For the APS film, a lamella structure was formed with solidification of molten zirconia and lamellae were interlaced with each other. Sliding between lamellae is restrained so that the mechanical elastic constants by bending deformation are about the same as that by tensile deformation. For the LPS film, lamellae were piled up regularly and the thickness of the lamellae was thinner than that of the APS film. The mechanical elastic constant of the LPS film measured by bending deformation was lower than that by tensile deformation, because of sliding between lamellae. On the other hand, the X-ray elastic constants of the APS and LPS films were nearly identical, because the X-ray elastic constant was obtained from the strain of the crystalline phase in response to the applied stress.

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Thermal shock strength of laminated carbon-carbon (C/C) composite must be evaluated for an application to the components surrounded by a high temperature field. However, few studies have been done. This paper presents it by laser irradiation technique for laminated C/C composite. A laser irradiation method newly proposed was applied effectively to lamination of C/C composite for the evaluation of thermal shock strength. Introducing the critical power density at which the material fracture occurs, thermal shock strength was obtained. It was concluded that the critical power density could be a new measure to evaluate thermal shock strength for laminated C/C composite.

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Fracture strength of cylindrical specimens made of Si₃N₄ and SiC were evaluated by a thermal shock test. Each specimen was preheated uniformly at 1573 K in an electric furnace, then cooled locally by high-velocity helium gas passed through a narrow slit. The transient temperature distribution and the thermal stress were calculated by FE analysis. The failure probability was also estimated by assuming that the fracture strength due to thermal shock was determined by the fracture toughness of the material and the two-parameter Weibull distribution was able to apply the distribution of initial flaw size. Predicted failure probability of SiC was good agreement with test results. As for Si₃N₄, large difference was observed between the estimated and the tested failure probability. The descrepancy was however decreased in consideration of subcritical crack growth during thermal-shock tests.

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Recently, coating materials have been noticed, and are widely used in the several fields. However, it is being taken up as a serious problem that the large-scale destruction of the structure will be occurred at the time when the damage of the coating film generates. On the other hand, the new concept on the active damage control, which the structure member parts adapt itself to the environmental conditions, has been exposed to the attention in the material science. In this concept, they have the function such as a living organism, and do the work in proportion to the environment in the circumference. They are called smart material or smart structure. In short, it denotes that they have the sense organ for detecting the damage in itself, the processor organ for deducing a suitable signal for the damage and the actuator organ for restraining the damage. Therefore, it is a possible by applying the concept of the smart materials and structures to actively restrain or restore the damage. In this study, the basic study on the damage restraint of coating film is proposed. In short, by adopting this concept, the efficiency of actively restoring the damage of the film is reported.

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The influence of graphite volume on fracture toughness and fatigue crack propagation had been studied in 7 mass% chromium Ni-hard cast iron with 0.57∼4.52% graphite for the purpose of improving the wear and crack resistance as steel rolling mill roll materials. The main experimental results are shewn as follows ; (1) Fracture toughness (K_IC) increases with an increase in graphite volume and shows the maximum K_{IC&Gt; value of 25.7 MPa·m^0.5 at 1.90% graphite, and then it decreases as the graphite volume rises over 1.90%. (2) Threshold stress intensity factor range for fatigue crack propagation (ΔK<th}) varies in the same manner as fracture toughness and it shows the maximum ΔK_th value of 8.5 MPa·m^0.5 at 1.90% graphite. (3) Paris-Erdogan equation da/dN= C (ΔK₁)^m holds good between crack propagation rate and stress intensity factor range, and there is a constant relation of C=3.89×10^-4/15.8^m. (4) Existence of adequate graphite volume restrains crack propagation and improves K_IC and ΔK_th. (5) Heat-treatment of hardening-tempering deteriorates ΔK_th and hastens crack propagation.

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When stress corrosion cracking or corrosion fatigue occurs, multiple cracks are frequently initiated in the same area. According to section XI of the ASME Boiler and Pressure Vessel Code, multiple cracks are consider as a single combined crack in crack growth analysis, if the specified conditions are satisfied. In crack growth processes, however, no prescription for the interference between multiple cracks is given in this code. Even if the cracks are initially located far away from each other, as cracks become closer due to crack growth, the interference becomes larger. Therefore, the interference effect on the crack growth process should be considered. The JSME Post-Construction Code, issued in May 2000, prescribes the conditions of crack coalescence in the crack growth process. This study aims to extend this prescription to more general cases. In this study, a simulation model was applied, to simulate the crack growth process, taking into account the interference between two cracks. This model made it possible to analyze multiple crack growth behaviors for many cases (e. g. different relative position and length) that could not be studied by experiment only. Based on these analyses, a new crack growth analysis method was suggested for taking into account the interference between multiple cracks.

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The propagation behavior of fatigue cracks emanating from pre-cracks was numerically simulated to evaluate the development of crack closure with crack growth. Plasticity-induced crack closure was analyzed for two dimensional through cracks and penny-shaped cracks in plane stress, plane strain and Tresca's yield condition. The plastic constraint factor of penny-shaped cracks in Tresca's yield condition decreases with increasing applied stress. When compared at the same amount of crack extension, the development of crack opening stress with crack extension for through cracks and penny-shaped cracks in plane strain condition was nearly close. The crack opening stress intensity factor at the threshold can be simply approximated as a function of the applied stress and the amount of crack extension. The cyclic resistance-curve method was used to predict the fatigue thresholds of pre-cracked components. When compared at the same initial crack length, the fatigue limit for fracture of penny-shaped cracks in plane strain condition is larger than that of through cracks. On the other hand, the relation between the initial crack length and the fatigue limits for fracture is nearly independent of the defect type.

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The fatigue test of surface crack propagation was conducted on the plate specimen with a small hole at a notch root. The cyclic strain at a notch root was measured by a strain gage and the cyclic strain behavior has been shown as the relationship between the strain and the number of cycle. The propagation rate of the surface fatigue crack at a notch root was found from crack length curves. It is found that the propagation rate of surface fatigue crack is expressed as the mth power of the range of strain intensity factor. The strain intensity factor is defined as the parameter multiplied the cyclic strain range at a notch root by root of the half length of a surface crack length. The value of m is 2 in the middle and is more than 2 in the edge of the plate thickness.

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The indentation fracture (IF) method, the single-edge precracked beam (SEPB) method, and the single-edge V-notched beam (SEVNB) method were applied to evaluate the fracture toughness of four kind of porous ceramics of SiC, Al₂O₃ and Mg₂Al₄Si₅O₁₈ with porosity ranging from 37 to 43%. The microstructures of these materials were composed of ceramics grains, glassy grain boundaries and pores. Each grain was joined together with the glassy grain boundary phase. The IF and SEPB methods were not applicable because both precracks and indenter traces were not visible. On the other hand, the SEVNB method was applicable because the V-notch could be easily machined by grinding. In the case of the SEVNB method, the applied load versus back-face strain plots under four point bending showed nonlinearity prior to the maximum load. The R-curve behavior was estimated from the compliance change of specimens. The fracture toughness of porous ceramics was smaller than that of dense ceramics, and increased with increasing crack extension. Since the stable crack predominantly propagated along glassy grain boundaries, the R-curve behavior depended on the loading rate and matrix grain size. The increment of R-curve by grain briding got bigger for coarser-grain sized ceramics.

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This paper studies the creep and creep rupture properties of Sn-95 Pb solder. Creep and creep rupture tests were carried out using Sn-95 Pb solder specimens at 313 K, 353 K and 398 K to develop a creep constitutive equation and rupture time equation. There were clear short primary, long tertiary and steady creep stages in Sn-95 Pb solder at the three temperatures. A creep constitutive equation was proposed as a function of stress and temperature. The proposed equation predicted the experimental creep strain within a factor of 1.25. A new equation for predicting creep rupture time was also proposed. The equation predicted the experimental rupture time within a factor of two. These results were compared with those of Sn-37 Pb solder to discuss differences resulted from melting temperature.

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Using our proposed and modified micromodel which judges whether ductile fracture occurs or not and our proposed evolution equation which represents the change of void volume fraction, analysis of inner fracture defect in drawing is performed. The obtained results are summarized as follows. Firstly, the two types of void shape and those of void configuration in our previous papers are unified and one type of void shape and that of void configuration are defined. Secondly, the inner diameter of the die at which the material fractures, the material density distribution in the radial direction after drawing through the die which precedes the die at which the material fractures, and the shape of inner fracture defect after drawing through the die at which the material fractures, calculated from analysis agree with those obtained by experiment. Thirdly, the inner diameter of the die at which the material fractures calculated from analysis agrees with that calculated using the Oyane's equation of fracture criterion. The number of unknown constant in our proposed evolution equation is equal to that in the Oyane's equation. Hence, the validity of our proposed micromodel and evolution equation is confirmed.

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Although stress and strain states are same in simple and pure shear states, longitudinal wave velocity changes propagating in the plastically deformed medium under simple and pure shear states are apparently different each other according to authors' theoretical and experimental research works. The objective of this paper is to discuss the effect on ultrasonic wave velocity changes due to texture and cross slip under simple and pure shear states via finite element polycrystal analysis. In small plastic deformation range, in spite of quite different longitudinal wave velocity changes under simple and pure shear states, the texture developments and transverse wave velocity changes under both states are similar each other. That suggests dependence of transverse wave velocity on texture. Next, the multiplicative amounts of intersected slides between primary and secondary slip systems, which relates closely to the amount of cross slip, under simple and pure shear states are examined. The result, i.e., this multiplicative amount under pure shear state is larger than that under simple shear state, means the point defects induced by cross slip are much easier to introduce under pure shear state than under simple shear state and suggests that the point defects induced by cross slip may cause quite different longitudinal wave velocity changes.

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