The long-term reliability of electroplated copper thin-film interconnections varied drastically depending on their crystallinity. The crystallinity was mainly dominated by the seed layer material for electroplating because of the lattice mismatch between the seed layer material and copper. Even though tantalum is indispensable for a barrier of copper diffusion into silicon or oxide, the quality of thin copper films is rather low because there is a large mismatch in the lattice constant between tantalum and copper. Ruthenium is one of the most effective materials for improving the crystallinity of the electroplated copper thin films and the stability of the copper thin films electroplated on the ruthenium seed layer was very high during annealing up to 200℃.

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Metastable austenitic stainless steels are known to transform to BCC martensite. The transformation behavior depends on the phase stability. Although influences of the phase stability on the transformation behavior and its associated mechanical properties in austenitic stainless steels have been investigated by many researchers, there is still frontier in terms of carbon effects on work hardening stemming from martensitic transformation. In this study, we investigated the effect of carbon on work hardening in three types of Fe-Cr-Ni austenitic stainless steel: Fe18Cr8Ni, Fe18Cr8Ni0.05C and Fe18Cr8Ni0.15C steels. According to the present experiments, we concluded as follows: (1) Addition of 0.15% carbon changed the transformation regime from stress-assisted to strain-induced transformation. (2) High carbon concentration causes dynamic strain aging which is related to strain-induced martensitic transformation. (3) The coexistence of martensitic transformation and dynamic strain aging provided exceptional work hardening and elongation.

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The measurements of photovoltaic performances of a single crystalline silicon solar cell module subjected to thermal loading are performed. The current vs voltage (I-V) relations under dark environment, dark I-V characteristics, of the modules are measured before and after loading. The specimens are observed using an optical microscope and an ultrasonic scanning microscope to investigate the initiation and growth of cracks in silicon cells, de-bonding at the cell/glass interface and cracks in the substrate.

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Throwing type fire extinguishing equipment needs to be designed to fracture at the time of collision without fracturing at the time of throwing. In this study, we predict the fracture of fire extinguishing equipment by analyzing the notch root stress using FEM at the time of a collision and the time of throwing. The objective of the present study is to design an optimum notch shape which gives breakable equipment structure at the time of collision, not to be fractured at the time of throwing.

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In this study, tensile tests of plate-fin structures with a digital image correlation (DIC) measurement system are conducted to investigate validity of the homogenization analysis method developed by our research group. For this, tensile tests using plate-fin test specimens made of an epoxy are performed, and their microscopic deformations are measured by a DIC measurement system. Then, corresponding elastic-viscoplastic analysis of plate- fin structures is carried out using the homogenization theory for nonlinear time-dependent materials. The analysis results obtained are compared with the experimental results to validate the present method.

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The explosion characteristics of a composition pressure vessel comprised of three kinds of different CFRP layer of the winding angle are examined. A location of the fracture origin is identified using fractographic technique from the length of the piece of the CFRP in the burst vessel. Also the fracture initiation location of the container is estimated using the time lag at the time of the arrival of the elastic wave by the high-speed strain measurement of CFRP at the burst.

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The tensile deformation behavior of polyvinylidenedifluoride (PVDF) hollow fiber membranes used for water purification was studied. The present PVDF membrane has sub-micron pores with open cell structure. The surface and cross section of the membranes were observed by FESEM to investigate the microstructure (cell size and geometry of the cell ligament). During uni-axial tensile test, the membranes underwent elastic deformation and plastic deformation. In order to establish the mechanical model for such a tensile deformation, finite element model (FEM) was carried out. In this model, Kelvin polyhedron (truncated octahedron) was employed to create 3D open cell structure. Such one-unit cell approach can predict elastoplastic deformation and then it is concluded that we establish a fundamental FEM model to describe the deformation behavior of porous structure. The present model enables the prediction of the macroscopic deformation behavior of the membrane, by taking into account of pore structure. The insight may be useful for porous membrane fabrication and for reliable operation of water purification.

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Scatter of small fatigue crack growth rate is larger than the scatter of large fatigue crack growth rate. In fact, the transition length of small and large fatigue cracks depends on material and stress. In order to measure the transition length in specific condition, a new method using a single specimen is proposed in this study. The specimens used in this study contain eight FIB notches. Introducing eight FIB notches means that each specimen can produce eight data of fatigue crack growth rates. By using these data, the scatter of fatigue crack growth rate was evaluated, enabling the determination of the transition length. In addition, evaluation with three specimens was also conducted for validation. Finally, data of three specimens were compared to the data obtained by a specimen to verify the validity.

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To evaluate the effect of non-uniform deformation on the elastic and viscous strain during unloading of the polymeric material, strain distribution after loading, unloading were measured by digital image correlation method. Local viscous strain was obtained by removing the elastic strain from total strain cased during unloading. Obtained results clarified that the strain recover in necked region was very small while those caused in necked surrounding region was large.

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The out-of-plane strain constraint around a notch/crack tip of a round bar with a deep circumferential notch/crack is as high as that of a plane-strain compact tension specimen (CT). Especially a round bar with a circumferential crack also shows equivalent Mode 1 stress distribution with a CT because of narrow ligament area equi-axis voids followed by cleavage fracture, caused by tri axis stresses, are generated limited at 0.5 < r/(J/σ_0) < 1.5. On the other hard, that with a circumferential notch (tip radius=0.05mm) shows smaller Mode I stress distribution, and shear elongated voids, caused by low in-plane strain constraint a generated. The voids are widely located at 0.5 < r/(J/σ_0) < 3. Although the obtained critical J by a specimen with a deep circumferential notch may not be so overestimated one, the fracture mechanism is different from that with a deep circumferential crack.

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Water hammer is familiar phenomena in our life while this phenomena causes noises and failures of water plumbing. Previous studies of water hammer revealed that wave speeds were well predicted by a simple theory and pressure surges could be estimated with the speeds by experiments, numerical analysis, and analytic methods. However, the frontal wave shape of water hammer was neglected and its propagation mechanism was not discussed in the simplified theories. This study focus on the frontal mechanism to understand the structure and decrease the damage of the water hammer. In the present study, we visualize the frontal structures in experiments and numerical analysis as well as revealing strain signals of coupled tubes with pressure waves.

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The radiated sound should have not only the impact force but also the defect information of the impacted body. In this study, we perform the impact test of the aluminum circular plate with a circular pit. The distributions of the radiated sound pressure under the plate are measured by using the moving microphone system. Moreover, the FEM analysis is curried out The influence of the pit to the radiated sound prime is studied.

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In the finite element analysis, structural elements, in which plane stress is assumed in the transverse direction, can predict the bending behaviors accurately only if the sheet is thin. However, for a sheet forming, structural elements are not sufficient to simulate the complex behaviors, such as, the deformation of the sheet and the contact forces at the sheet-die interface. In this study, we improve a structural element by introducing a displacement variation along the transverse direction.

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6000 series aluminum alloy sheets have been widely used for automobile body. However, since the aluminum alloy sheets generally exhibit lower formability than steel sheets, wrinkling and buckling are often occurred during plastic forming process. Therefore, it is essential to predict plastic deformation behavior and formability of the aluminum alloy sheets by finite element simulation. In this study, the crystal plasticity finite element simulation was used for investigating plastic deformation behavior of 6000 series aluminum alloy sheet during hole expansion test. In order to perform quantitative simulations, the crystal orientation data used for the simulation was obtained by EBSD measurement. The material parameters of the crystal plasticity constitutive equations were identified on the basis of the experimentally obtained uniaxial stress-strain curves. The simulation results demonstrated that the crystal plasticity finite element simulation was useful for analyzing plastic deformation of the sheets and the crystal rotation during the hole expansion process.

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Numerical biaxial tensile tests of interstitial-free (IF) steel sheet were performed using crystal plasticity finite element method based on the mathematical homogenization method. In order to obtain quantitative simulation result, a representative volume element (RVE) describing crystallographic texture in the IF steel was constructed using crystal orientation data obtained by EBSD measurement. The material parameters of the crystal plasticity constitutive equations were identified from the experimentally obtained uniaxial true stress-true strain curves. Using the RVE and the parameters, the biaxial tensile deformation behaviors of the sheet under nine stress paths were investigated. The simulation results were validated by the experimental biaxial tensile tests with a cruciform specimen. We demonstrated that the simulated stress-strain curves showed a good agreement with the experimental results.

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A cutting process of a semiconductor chip has a problem occurrence of heat and material loss. To solve these problems, the processing method which is used crack propagation has been proposed. The crack propagation simulator is needed for design the process condition. However, the he crack propagation prediction method which considered anisotropy of the fracture toughness value has not been established. In this paper, firstly, the crack propagation simulator for anisotropic material was developed and the validity of the calculation was compared with the experimental results.

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Proton Exchange Membranes (PEM) in Membrane electrode assemblies (MEA) in polymer electrolyte fuel cells is major concern for fuel cell vehicles. Hygro-thermal cyclic conditions induce the mechanical stress in MEA and cracks are formed under operating conditions. Chemical degradation of PEM is caused by radical attack. The purpose of this paper is to understand the mechanical characteristic of chemically damaged PEM. We carried out tensile tests for PEM degraded by Fenton reaction. For tensile tests, PEM was immersed in hydrogen peroxide solution containing the iron ions. The tensile tests revealed that by Fenton reaction, the yield stress and the modulus of longitudinal elasticity of PEM was increased and the breaking strain was decreased. This result indicates that PEM property is changed by suffering chemical damage. It is concluded that chemically damaged PEM is stiffer and more brittle than undamaged one.

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Recently, high-strength steels are widely used in automobile industry for the weight reduction of car body. The high-strength steels have low ductility, it sometimes causes the cracking during press process. In the present study, we investigated the simple specimen shape for the calibration of Extended Mohr Coulomb fracture model. Three types of specimen based on JIS-5 specimens were modeled and the relationship between stress triaxiality and equivalent plastic strain were calculated by Finite Element Analyses. It is conclued that the specimen with hole have bi-axial stress state and it can be used for the calibration of bi-axial stress condition. However, the specimen with notch did not have shear stress condition.

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Skin wounds are the physical damages of body surfaces and caused by burn injury, rupture, and surgical dissection. The wounds are usually healed by skin fibroblasts in dermis layer infiltrating into wound region and synthesized collagen matrixes. However, it has risks to result in skin diseases such as keloid if the healing process is disordered to cause excessive cell infiltration and collagen secretion in the wound area. Mechanical stimuli are supposed as one of the factors of keloid because the skins are subjected to mechanical stretching during the wound healing process. However, the pathogenesis of these diseases is still unclear. Therefore, the purpose of this study is to evaluate the effect of cyclic stretching stimuli on the morphology of Normal skin and keloid fibroblasts. In this study, to simulate a skin tissue in vitro, the fibroblasts-populated collagen gels were developed. The cell-populated gels were cyclically stretched during 4-days culture. Under conditions of cyclic stretch, the normal fibroblasts showed higher proliferation and migration compared to those under static condition, whereas the keloid-derived fibroblasts showed rounded shape in the gel and less proliferation and migration.

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The optimization tool is used in the design and develop process in the manufacturing industry company recently. Especially in the magnetic circuit design process, these tools has been used generically. We express The functions that these tools should have and introduce two optimization motor design case studies.

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