This paper presents a methodology (Computer Aided Principle CAP) of quantifying the interaction of each design factor for helping the design engineers to understand the complicated design principle. In this method, correlative parameters are extracted by using a cluster analysis with parametric study. The results can supply a guidance to the engineer for understanding the fundamental mechanism of the structural phenomena. The CAP is applied to two design problems. An numerical example of an offset frontal, crash against deformable barrier (ODB) is demonstrated to express the effectiveness of the presented method. And thermal fatigue reliability of BGA solder joints was assessed with the consideration of the interaction between design factors, and it is made clear that fatigue mechanism can be understood easily by the warpage of BGA and PCB.

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Intelligent tires, also known as smart tires, are equipped with sensors to monitor the strain of the interior surface and the rolling radius of tire, and are expected to improve the reliability of tires and tire control systems such as anti-lock braking systems (ABS). However, the high stiffness of an attached sensor like a strain gauge causes debonding of sensors from tire rubber. In the present study, a novel optical method is used for the concurrent monitoring of in-plane strain and out-of-plane displacement (rolling radius) utilizing the non-planar surface of the monitoring object. The optical method enables noncontact measurement of strain distribution. The in-plane strain and out-of-plane displacement are calculated by using image processing with an image of the interior surface of tire that is taken with a single CCD camera fixed on a wheel rim. This new monitoring system is applied to an aluminum beam and a commercially available radial tire. As a result, the monitoring system provides concurrent measurement, of in-plane strain, out-of-plane displacement and tire pressure, and is shown to be effective as the monitoring system for the intelligent tires.

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In automobiles, the CFRP has a possibility of weight reduction in automotive structures which can contribute to improve mileage and then to reduce Carbon dioxide. On the other hand, the safety of collision should be also made clear in the case of employing the CFRP to automotive structures. In this paper, the CFRP guarder belt equipped in the automotive door is developed and examined by an experiment and a numerical analysis for replacing the conventional steel door guarder beam. In the numerical analysis, a commercial FEM solver (ANSYS) was employed and the laminated shell element were used in the CFRP guarder belts. The impact response behavior and the absorbed energy of the CFRP guarder belt were obtained by the tower drop weight impact test. The experimental relation of impact load to displacement for CFRP guarder belt agreed well with that of numerical result. From the comparison of both results, the numerical method developed here is quite useful for estimating impact behaviors of CFRP guarder belt.

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Impact tensile properties of unidirectional fiber-reinforced composites are evaluated using a tension-type split Hopkinson bar technique. In this study, thermoplastic epoxy resin and three kinds of reinforced fiber such as carbon, E-glass, and T-glass are employed as a matrix and reinforcement, respectively. The experimental results indicate that strain rate has no effect on tensile properties in case that the carbon fiber is employed as reinforcement. On the other hand, the tensile strength and strain of E-glass and T-glass fiber composites are obviously affected by the strain rate. Although both fibreglasses and thermoplastic epoxy resin are shown to be sensitive to the strain rate, the fibreglasses contributes more significantly to the strain rate effects of the maximum stress and strain.

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A new type of plug, namely, load-control attachment was proposed to control energy absorption capability of carbon fiber reinforced plastic (CFRP) laminate. The attachment consists of inner and outer curvature constrainers, which guides both surfaces of the CFRP laminate under crushing. Quasi-static compression tests of unidirectional CFRP laminated tubes were performed by applying the attachment. It was revealed that the CFRP could show more than twice of specific energy absorption than that ever reported when attachment of R_o, R_i=0.2mm was used. On the other hand, minimum specific energy absorption of 8kJ/kg was shown when attachment of R_o, R_i=5.8mm was used. The CFRP tube showed wide range capability of energy absorption from 8 to 178kJ/kg by changing the attachment without changing constituent or stacking sequence of the CFRP. The extent of the fiber fracture due to bending could be controlled by the curvatures of the attachment. The energy absorption due to delamination and splitting was small as compared with fiber fracture. Load-control attachment for plate-type CFRP laminate was also developed and fracture process of the CFRP was observed from its side. The fracture process of CFRP in the load-control attachment was revealed correspond with load-displacement curve.

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The effect of hydrogen exposure on high strength steel SCM435 with a sharp notched specimen was investigated. Tensile tests were carried out in hydrogen gas and in helium gas environments. In hydrogen gas environment, the specimen which was not exposed to hydrogen gas and the specimen which was exposed to hydrogen gas for 48h were used. As the result of tensile tests with various notched depth specimens, the tensile strengths of hydrogen gas exposed specimens were higher than that of hydrogen gas non-exposed specimens. The tensile strength increases with hydrogen gas exposed time until hydrogen diffuses homogeneously on tensile tests with the notched t=1.0mm specimens. The fracture surfaces of hydrogen gas specimens showed an intergranular fracture near the notch root where the helium gas specimens showed a fracture mode of microvoid coalescence. The crack initiation stress of the hydrogen gas non-exposed specimen was lower than that of the 48h-exposed specimen.

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In order to investigate the hydrogen gas effect on the fatigue limits of austenitic stainless steel SUS304 and SUS316L with small twin blind holes, metal fatigue tests are carried out in a low pressure hydrogen gas, in air and inert gases; argon or nitrogen. The fatigue limit of SUS304 is defined as the crack propagation limit not only in air but also in hydrogen and in nitrogen. And the fatigue limit of SUS304 in hydrogen gas is slightly higher than in air. The extremely low Fatigue Crack Growth Rates (FCGR) of not only SUS304 and but also SUS316L in hydrogen gas is lower than that in argon gas in the region of FCGR lower than 10^<-9>m/cycle. This seems to be due to plasticity-induced crack closure and supports higher fatigue limit in hydrogen.

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The existence of porosity in aluminum alloy die castings is unavoidable. If any porosity was left in the final products, there are harmful influences on the air leakage resistance and structural strength. The PRPC (Porosity Reducing Post Compression) process, by which the product is compressed under the remaining heat of the die casting, has been investigated to enhance the product reliability. In this study, the validity of PRPC was examined, mainly focused on the pore closure and bonding of the contact inner surfaces. The porosity inside die casting was observed non-destructively by using X-ray CT. The experimental procedures were as follows; (1) X-ray CT observation of aluminum alloy die castings specimens was carried out in initial state. (2) Compression load simulating the PRPC process was applied to the specimen at room temperature or high temperature. (3) X-ray CT observation was performed again. (4) Tension load was applied to examine the closing and bonding effect of PRPC process on the inner surface of porosity. (5) Re-open of the closed porosity was observed by X-ray CT after tension break. In the PRPC process under room temperature, the closure of porosity was possible, but the re-open of the porosity occurred by tension loading. However, In the PRPC process under high temperature, we could confirm that the bonding of porosity was possible without re-open after tension loading.

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In order to evaluate a casting material which has scatter tensile strength, a strength evaluation method was proposed. Tensile tests were carried out by specimen with a particular artificial defect as a fracture origin. The size of the fracture origin could be controlled using the proposed evaluation method. Therefore the tensile test results which have a little scatter were obtained. However shape of the artificial defect is different from one of casting defect and the effects of each defect on the tensile strength might be different. Then both of the stress intensity factors at the beginning of unstable fracture were compared, it was clarified that the artifical defect and the casting defect have the same effect on the tensile strength. By this method, a Si-added noncombustible Mg alloy which has large casting defects could be evaluated. It was clarified that there is no difference of tensile strength between 1% and 2% Si-added noncombustible Mg alloy, and it is obtained that the relationship between tensile strength and temperature.

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Porous aluminum has good lightweight property, high specific strength and high energy absorption ability. By applying porous aluminum as a multifunctional material of automobile, both collision safety and improvement of fuel efficiency can be realized. As the new fabrication method of porous aluminum of having high productivity and low-cost productivity, authors proposed the method by utilizing friction stir processing, i.e. Friction stir processing method (FSP method). In this study, changing the amount of alumina addition, holding temperature and holding time, porous aluminum is fabricated by FSP method. Based on the experimental results, the effects of these fabricating conditions on the porosity and the morphology of pores are investigated. It is shown that porous aluminum with the porosity up to 80% can be realized by optimizing the alumina addition, holding temperature and holding time.

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This paper presents a fundamental method to evaluate thermal fatigue life of power module. Coupled electrical-thermal analysis was performed to obtain the distribution of temperature due to electric current. Thermo-mechanical analysis was also carried out to calculate inelastic strain range generated in a solder joint. Crack path simulation technique was used to inverstigate fracture behavior on power module. Not only crack propagation, but also thrmal conductivity on the crack was considered. Fatigue crack initiates under Al bonding wire for the IGBT module. Crack propagation induces the change in thermal properties of power devices. Effect of bonding type on power cycling fatigue life was discussed. The fracture prosess depends on bonding type.

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In order to improve a fatigue life prediction technology of a spot welded structure, the method to evaluate the fatigue life by a nominal structural stress (NSS) was proposed. The authors have proposed the method to obtain the NSS accurately for spot welded structure composed of flat sheets. The proposed method uses the general loads of the nugget and the displacements on the circumference of the diameter D with the center of the nugget, which are obtained from finite element analysis. In this study, the proposed method was applied to a spot welded cylindrical shell structure. As the result, it was found that the proposed method was able to accurately obtain the NSS by using the displacements on the circumference of the small diameter D.

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It is recognized that the content and placement of inclusion in composite materials have a great influence on the mechanical properties such as strength. However there is no effective technique to estimate optimum properties of all models. In this research, a technique to obtain an optimum composite material composition under a constant content rate is proposed by using Cellular Automata (CA), Genetic Algorithm (GA) and Finite Element Method (FEM). The technique is one of the Evolutionary Cellular Automata (ECA) method and applied to the maximum and minimum rigidity and thermal conductivity problems of composite material. From the numerical results, it is obvious that the proposed technique is very useful.

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In the present study, the effect of strain rate on the mechanical properties of plain woven CFRP laminates with intermediate strain rates was investigated. Two types of CFRP with different matrix (Epikote 828 and YX8034) were used. Electro-hydraulic high speed testing machine were used for the experiments with intermediate strain rates. Elastic modulus and strength increased with the strain rate of 10^1/s. Tensile moduli increased with increasing strain rate. The increases in moduli of the plain woven composites were due to the increases in the properties of unidirectional CFRP. In order to evaluate the effect of strain rate on the mechanical properties of plain woven CFRP, analyses based on Ishikawa-Chou model were conducted. Analytical results were in good agreement with the experiments, which suggests that the microstructure of the fiber undulation and the mechanical properties of unidirectional composites are the important parameters for the textile composites design.

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In recent years, the laminated materials are designed and used widely in aerospace applications, for example. Therefore, it is important to evaluate the fracture characteristic of the laminated materials. In this research, the basic study on fracture control design for the laminated materials subjected to impact load is systematized. The dynamic fracture behavior is analyzed by using the high-speed video camera and the digital image correlation method. The dynamic stress intensity factor is experimentally calculated based on interfacial mechanics. In addition, the mixed-mode ratio, dynamic fracture toughness and kinking angle are evaluated from the dynamic stress intensity factor for the control and forecast of fracture. And, the characteristic of mixed-mode fracture criterion showing the condition and the behavior of fracture is examined. It is shown to be able to properly act as fracture control design by the materials evaluation method.

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Up to now, it is impossible to simulate dynamic crack propagation with distortion and heaving. In this paper the three-dimensional moving finite element method based on automatic tetrahedronization (MFEM BOAT) is developed. This method made it possible to simulate complicated dynamic fracture. The moving fine elements subdivision is used to evaluate exact, solution for singular field. The equivalent domain method is applied into the solution to calculate dynamic fracture parameters along dynamically propagating crack front.

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Failure in heat affected zone (HAZ) in welding has been a serious problem for the integrity of nuclear power plant. Trediction of crack behavior affected by the residual stress field in HAZ is important. In this paper, S-Version FEM (S-FEM) is applied to simulate the crack growth under thermal and residual stress fields. S-FEM is applied because the mothod enables us to generate cracked models flexibly. For evaluation of stress intensity factor, virtual crack closure integral method (VCCM) is employed. In order to confirm the validity of this analysis, numerical results are compared with previously-reported analytical and experimental results. Then, crack growth analysis in piping structure with welding joint was conducted. The residual stress data was provided by JAEA, Japan Atomic Energy Agency, based on their numerical simulation. Using S-FEM, two- and three-dimensional analyses are conducted, and crack growth behavior under thermal stress field is studied and discussed.

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Rotating bending fatigue tests were carried out using specimens with a small blind hole for Alloy 718 with different grain sizes, about 18, 32, 88 and 276μm, at room temperature and 500℃ in order to invistigate the effects of grain size and temperature on the growth resistance of a fatigue crack. Crack growth rates were determined by the term σ^n_aa (σ_a: stress amplitude, a: surface crack length, n: constant), uniquely in all of the materials and at both temperatures. Resistance to crack growth considering the difference in static strength increased with increasing in grain size. This was mainly caused by the roughness induced crack closure effect. Both of the static strength and the resistance to crack growth were decreased by softening at 500℃. The decrease in the resistance to crack growth was larger than that in the static strength. This was mainly explained from the difference in Young's modulus at the both temperatures. Flat areas, facets, reflecting the grain size were observed in addition to striations on the fracture surface in all of materials and at both temperatures, and the ratio of facet on the fracture surface increased with increase in grain size.

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Deformation behavior and strain rate sensitivity of an epoxy resin structural adhesive are experimentally investigated by using an INSTRON-type material testing machine and a split Hopkinson pressure bar apparatus. The experimental results show some fundamental features of a typical compressive stress-strain behavior of glassy polymers with linear elastic and nonlinear inelastic deformation stages. In the inelastic deformation, a peak stress and a strain-softening stage after the peak can be observed in the entire range of strain rate from 10^<-4> to 10^3s^<-1>. In addition, it can be found that the relationship between the peak stress and strain-rate for a semi-logarithm curve is linear in the range of low strain rate, however, the slope of the curve changes at high strain rate and the nonlinear behavior of the peak stress can be obtained against the strain rate. Based on the experimental fact, a plastic shear strain rate is formulated to describe such the nonlinear relationship of peak stress-strain rate for the adhesive. Finally, the validity of the formulated model is shown by comparing with the experimental result.

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A three dimensional constitutive model is formulated to describe the deformation behavior of an epoxy resin structural adhesive in a wide range of strain rate. This formulation is based on a four elements model with an elastic series element by considering that the adhesive is a glassy polymer. The plastic streching tensor is expressed by the effective stress, which is the difference between the total stress and back stress, and the plastic shear strain rate proposed previously by the authors. The stress tensor at each relaxation process can be obtained by a solution of non-linear simultaneous equation under an assumption which both plastic stretching tensors at each relaxation process are equivalent. The formulated constitutive model is implemented into the commercial FE code ABAQUS/Explicit and then a computational simulation is performed. As the result, a validity of the proposed model is shown by comparing the previously-obtained experimental result. In order to check the capability of this model, the deformation behavior and the strain sensitivity of CTBN modified adhesive are experimentally investigated by using an INSTRON-type material testing machine and a split Hopkinson pressure bar apparatus. Finally, it is shown that the proposed model can be also applied for a prediction of the deformation behavior of the different adhesives by comparing with the newly-obtained experimental result.

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A honeycomb core sandwich panel (hereafter, HSP for brevity) is superior in an impact absorption, because of the buffer effect of core. In order to develop the property, it is proposed to laminate the other layer of core. For example, a double layer HSP is superior to that of a single layer HSP with a same height in compression strength and an energy absorption. In consideration of an effect of these advantages on the impact property, a series of drop weight test was carried out by using double layer HSPs and a single layer HSP. For these HSP, total core heights of all HSP were same and some combinations of two core heights were made for double layer HSPs. From the obtained result, a resistance force and the energy absorption for the impact pact were evaluated. Furthermore, the mechanism to absorb the impact energy on double layer HSP was studied and compared with that of the single layer HSP.

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The fatigue property of a honeycomb core sandwich panel (hereafter, HSP for brevity) has been studied in consideration of usage as a floor panel. In previous papers, fundamental properties were reported; 1) A fatigue life as the floor panel was defined from the growth curve of dent depth. 2) It was possible to design by calculating the stress of crack initiation site on dent. 3) A fatigue damage level was predicted from the dent depth. In this study, it was attempted to study the local compression fatigue property of peripherally clamped double layer honeycomb core sandwich panel for the sake of wide application. Obtained results were summarized as the follows; 1) The higher a rigidity of HSP was, the shorter a fatigue life was. 2) The taller a core height near an indenter was, the deeper a depth of dent was when HSP had been fractured except a single layer HSP. 3) There were two steady regions in double layer HSPs. In consideration of the fatigue life and rigidity except self-weights, the double layer HSP that the core height near indenter is small is superior to the single layer HSP.

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In this paper, we propose a diamond structure including stacking faults as a candidate atomicscale model for nanocrystalline diamond (NCD) with a small amount of non-sp^3 bonded region. The previous work reveals that NCD thin films show unusual elastic behavior, where the diagonal elastic constants decrease and the off-diagonal elastic constants increase as the grain size decreases. Using ab-initio calculations, the stable stacking-fault structures are obtained, whose partial density of states (PDOS) of the 2p_z orbital of the carbon atoms facing stacking faults behave as those of non-sp^3 bonded atoms. Elastic constants of these structures are calculated from changes in the total energy by applying strains, which consistently explain the unusual elastic behavior of NCD films. This result shows that a combination of measurement and theoretical calculation is effective to analyze the relationship between microscopic structures and macroscopic property.

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The laser welding methods are widely used for manufacturing the products of which the high-quality welding conditions are required. Therefore, the establishment of the technique that evaluates the conditions of the melting region during the welding is desired. In this stydy, the various irradiation energy was irradiated to the SUS304 stainless steel by YAG (Yttrium Aluminum Garnet) laser equipment, in order to evaluate the melting conditions at the irradiation region. During the irradiation, the AE (Acoustic Emission) signals that occurred by the melting of the steel were detected. After that, the detected signals were analyzed with AE method, FFT (Fast Fourier Transform), wevelet transform and chaos analysis. And the melting conditions were observed with the optical microscope. In this paper, the relationships between the features of the signals and the conditions are reported.

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A blister is one of surface defects for extrusion material of aluminum alloy. In this paper authors investigate about a collapse of billet under extrusion and flow of material in tests using a scale model. From the results, the processing under extrusion can be visualized by using a plasticine and an acrylonitrile pipe. A residual air would be small if a billet length is shorter and a clearance is smaller. Furthermore, it is clarified that the residual air inside the billet causes the blister from rolling into the extrusion material at beginning of extrusion upset. It is considered that the surface defects of the extrusion material can be reduced by solving the above factors.

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Fully reversed bending fatigue tests were performed on low carbon steel JIS S10C in hydrogen gas and in. nitrogen gas at a low pressure. In nitrogen a crack showed almost the same non-propagating behavior as known in air, while in hydrogen a crack continued to propagate even near 10^7 cycles at the same testing strain range. In hydrogen gas, a crack showed intermittent growth by coalescing with a new micro-crack generated by slip behavior. This implies that hydrogen could reduce the ability of any factor affecting non-propagation.

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In order to develop the relationship between the notch strength ratio, defined as the notch tensile to tensile strength ratio, and the strain hardening exponent, the rate of increase in stress with elongation was investigated on the notched specimens associated with strain hardening ability of the materials. The plastic constraint resulting from strain localization due to low rate of strain hardening raised the stress-elongation curves distinctly. Hence, the stress increase rate increased with decreasing strain hardening exponent for the notched specimens with widely different notch acuity. The useful correlations were thus established to estimate the tensile load required to break the blunt notch specimens as well as the sharp notch specimens from strain hardening exponent.

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