Response surface methodology has been used in the optimum design and reliability design. However, the response surface approximation may have uncertainty in the case when the reasonable interactive terms are not taken into account. In this paper, a new updating method for the response surface approximation is proposed. This method is based on Kalman filter and multiplex hypothetical official approval. The response surface approximation with uncertainty can be updated using a new method. From the application to examples, it is indicated that in the case that some response surface approximations for design space were stored and many sampling data from these approximations can be generated easily, the information of the design variables such as interaction among variables can be extracted and the reasonable response surface models can be identified by applying various response surface models with many interactive terms actively.

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This paper presents a new efficient real-coded genetic algorithms for constrained optimization. In general, it is efficient to use the gradient methods for the constrained optimization. However, because actual design problems often include extremely nonlinear or discontinuous characters, the gradient methods do not necessarily work well. Therefore, the present authors developed the "Center Neighborhood Crossover (CNX)" for real-coded genetic algorithms and applied to truss structure optimization. But, GAs have some fatal problems in handling the constraints. In the constrained optimization using GAs, designers have to translate the constrained problem to a basic unconstrained problem by using some methods such as the penalty function methods. It is, however, difficult to decide appropriate penalty parameters. In the present study, we developed "Real-coded Genetic Algorithms with Active Constraints (RGAAC)" In RGAAC, the points outside feasible area is pulled back to active constraints by the gradient method. The present method enables an efficient search.

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A large-scale molecular dynamics simulation on an atomistic model and an elasto-viscoplastic finite element analysis on a continuum model are carried out to study deformation field near a crack tip in amorphous metal. The atomistic model, in which Finnis-Sinclair type potential for iron is assumed as interatomic potential, is generated using heating-quenching simulation. The parameters in strain-dependent elasto-viscoplastic constitutive law for the continuum model are determined using a uni-axial tensile test for the atomistic model of amorphous metal. The results for the crack problem using the atomistic model and the continuum model are compared each other. The shape of crack front, strain distribution and stress distribution around the crack tip, increase of crack tip opening displacement and crack growth are examined, and FE results for the continuum model agree with MD results for the atomistic model. However, the continuum model can depict only averaged description of the atomistic model. In the atomistic model, it is observed that the highly deformed region consists of atomistically localized deformation. The atomistic simulation is indispensable to reveal the microscopic structures and deformation mechanisms.

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This paper describes a new miniature creep tester and the size effect of creep and creep rupture times for solders. The new miniature creep tester was developed and creep rupture tests were carried out using five types of Sn-37 Pb specimens with different gage diameters. Creep rupture times of miniature specimens did not differ from those of bulk specimens at a higher stress but they were scattered around the bulk data at lower stresses. Creep rates of miniature specimens were slower than those of bulk specimens and creep ductility of miniature specimens was smaller than that of bulk specimens.

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The stress measurement method using an electrodeposited copper foil with microcircular holes has been developed to measure the cyclic biaxial stress. However, as shearing stress amplitude controls the phenomenon of grown grain occurrence, which is the principle of this method, the static mean stress acting on the elements cannot be measured only using this phenomenon. So the propagation of fatigue cracks from the periphery of microcircular holes are examined to measure mean stress. In this report, temperature and frequency, which affect the crack propagation mainly, are kept constant. And the effect of mean stress on fatigue crack propagation is investigated. Namely, using copper foil and nickel foil, fatigue crack lengths are measured under various combinations of stress amplitude and mean stress, and the basic equations connecting the crack propagation rate, stress amplitude, and mean stress are presented.

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A fatigue-test machine for alternating bending under strain-controlled conditions was developed. Bending-fatigue tests for various strain ratios were then performed. The results obtained can be summarized as follows. (1) The fatigue life curves under alternating bending and pulsating bending, as expressed by the relationship between maximum strain and the number of cycles to failure, systematically follow the order of strain ratio. (2) The larger the strain ratio, the longer the fatigue life. (3) The fatigue life under rotating bending is shorter than that under alternating bending. (4) The increase in temperature during cyclic bending becomes larger in the order: rotating bending, alternating bending, pulsating bending. The fatigue life decreases in proportion to the increase in temperature. (5) The fatigue limit of strain for alternating bending, pulsating bending and rotating bending is in the region of R-phase transformation.

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The two-dimensional mesoscale simulation method using the natural element method previously proposed by the authors for brittle microcracking solids is extended to include the effects of microinclusions or microvoids. The mechanical effect of microinclusions or microvoids is considered by controlling the material constants in the neighborhood of these defects. The relationship between overall elastic moduli and area fraction of microinclusions or microvoids is studied. Considering regularly perforated sheets with holes as a 2-d solid containing microvoids, the relationship between macroscopic yield stress and distribution of microvoids is investigated to verify the validity of the proposed method.

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The two-dimensional meso-scale simulation method using the natural element method previously proposed by the authors for brittle microcracking solids has been applied to the analysis of the elastic deformation and fracture behavior of aluminum sheets containing random array of equi-sized holes under uniaxial and biaxial loading to study the ligament flow localization and void linking during ductile fracture. The calculated results for the load-displacement curve and the void linking have agreed well with the experimental results given by Geltmacher et al. The validity of the present method has been demonstrated through these numerical studies.

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The 3-D finite element analysis program considering the coupling of heat conduction, damage evolution and liquid metal embrittlement has been developed in order to solve thermal damage and liquid metal embrittlement problems. The developed program has been applied to the evaluation of damage grenerated by the effect such as zinc-embrittlement in hot-dip galvanization. The heat conductivity considering the influence of damage is applied to heat conduction analysis and the damage analysis is conducted by the finite element program using the constitutive equation based on Lemaitre's theory. Numerical studies for the damage evolution in thick cylinders under high temperature have been done to show the validity of the coupling of heat conduction, damage evolution and the effect of liquid metal embrittlement.

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In the previous study, the analysis method is developed to solve problems considering thermo-damage-embrittlement coupling, as it is difficult to understand mechanical behaviors by experiments in the complicated problem such as hot-dip galvanization cracking. In the present study, the material parameters for the embrittlement and damage are determined using the data of tensile tests in hot-dip galvanization. Furthermore the thermo-damage-embrittlement coupling and the initiation of cracks in actually used steel structural members have been studied.

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Sintered molybdenum plate was rolled in one pass at 873 K to specimens with four degrees of 0, 10, 25 and 50% in thickness reduction. Tensile tests for the smooth and notched specimens were carried out to examine the effects of the level of plastic deformation and the edge notch on the change of ductile-brittle transition temperature (DBTT). The specimens were pulled at various temperatures between 163 K and 473 K and at a strain rate of 5.5×10^-3s^-1. Consequently, molybdenum could be deformed without any detectable defect up to 50% reduction in thickness by the rolling. For both of the smooth and notched specimens, the ductile-brittle transition temperatures were monotonously lowered with increasing the thickness reduction. The presence of an edge notch caused an increase of transition temperature by about 120 K to 160 K in a thickness reduction range of 0% to 50%.

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Influences of stress ratio on the off-axis fatigue strength of a unidirectional fiber-reinforced composite T800H/2500 have been studied. Tension-tension and tension-compression fatigue tests on plain coupon specimens with fiber orientation angles θ = 0, 10, 15, 30, 45 and 90° were performed for stress ratios R = 0.5, 0.1, -0.3 (θ= 0°) and R = 0.5, 0.1, -1.0 (0°< θ &lne; 90°), respectively. Also, a fatigue damage mechanics model that considers the effect of stress ratio was formulated. Fatigue strength of the unidirectional T800H/2500 decreased as the stress ratio decreased, irrespective of off-axis angle. The S-N relationships were almost linear in the range of fatigue loading up to 10⁶ cycles, regardless of off-axis angle and stress ratio. The non-dimensional effective stress based on the classical static failure theory succeeded in a unified description of the directional characteristic of the off-axis fatigue strength for all stress ratios. The proposed fatigue damage mechanics model can predict the stress-ratio dependent off-axis fatigue behavior of the unidirectional system employed.

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The so-called 'complete projection length' and 'incomplete projection length' of the fibers under the composite surface were theoretically derived, assuming that fibers could be observed from the surface. The whole of the fiber cannot be always observed because some other fibers frequently overlap the fiber. The position and the width of the overlapping part were derived based on the probabilistic theory. Variations of the complete projection length and the incomplete projection length with the fiber length were calculated, and it was examined about the possibility of the fiber length distribution estimation by this theory. Furthermore, it was examined about the influence of the several factors on the complete projection length and the incomplete projection length.

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It is possible to carry out stress measurement by single X-ray incidence using whole part of Debye-Scherrer ring. Yoshioka et al, reported that it is useful for this method to use image plate (IP) for its practical use. There is a possibility to analyze Debye-Scherrer rings of plural phases in composite materials simultaneously exposed on one image plate, as the diffraction rings have the different radius due to the different diffraction angle each other. It will be possible, in these cases, to measure phase stresses, macro- and microstresses by single X-ray exposure. Therefore, we can carry out quicker X-ray stress measurement. In case of the use of chromium K_α radiation to dual phase stainless steel, αFe211 diffraction occurs at 2θ=153.5 deg and γFe311 diffraction at 2θ=146.6 deg is also available if chromium K_β, radiation is used. Through these diffraction experiments, the stress measurement mentioned above will be possible.

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A method for measuring residual sintering stress in glass-ceramic substrates with multilayer copper circuits has been investigated. This method uses the length of a crack produced from a Micro-Vickers impression on the substrate. First, the relation between the stress and the crack length is obtained by applying the method to mechanically stressed glass-ceramic plates without copper. Next, we determine the conditions under which we can apply this method to substrates with multilayer copper circuits. If the measurement is conducted very near to a copper layer, the crack produced bends toward the copper. From finite-element stress analyses, we found that this bending is caused by the indentation-produced bending deformation of the substrate. This deformation only occurs where the substrate has been softened by the presence of copper. Therefore, to prevent such crack bending, the regions to which our method is applicable are restricted to those at distances of more than 50 μm from the copper.

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This study describes the change of the characteristics of wear amount and angle dependency by properties of impact particles. First, as to dimension, in cases of particle diameter 370 mm and 660 mm. the angle dependency of mild steel is a twin-peek type, while the angle dependency shows the soaring tendency in case of diameter 990 mm. As to hardness, while mild steel of standard grit shows the twin-peek characteristic, quench hardening grit tends to grow steadily. Then, the unified consideration that the factors of particle-diameter and hardness affect cutting and deformation types of erosive wear differently will enable us to comprehend this change of erosive wear characteristics. Moreover, our test result with polygonal steel grits has proved that the above mentioned two wear-mechanisms can be accountable quite satisfactorily.

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