Hot parts of gas turbine are subjected to a high-temperature gas environment. Thus, thermal barrier coatings (TBC) are coated on the surface of those components in order to protect the superalloy-based substrate from such aggressive environment. TBC is deposited by thermal spray technique, which is based on the deposition process of the continuous molten-particle impact onto the target. Thus, the mechanical properties of the deposits are affected by particle velocity, particle temperature and pre-heated substrate temperature as the spray condition. Previous study has examined about the influence of the spray condition on thermal and mechanical properties of the freestanding ceramic coating detached electrochemically from the TBC coated plate-shaped substrate. The results indicated that the particle velocity strongly affects the micro-hardness, elastic modulus and bending strength. In this study, the influence of high-temperature exposure condition on thermal and mechanical properties of the freestanding ceramic coating was examined as sequential report. As the results obtained by this measurement, it was found that the elastic modulus of the high-temperature exposed ceramic coating is lower than one of the as-sprayed coating. It was considered that this trend is caused by the increase in compliance of the overall ceramic coating by nucleation of microcrack along the splat boundary. It was also found as well as the results indicated in the previous report that Vickers hardness can characterize elastic modulus and bending strength of the freestanding ceramic coating with a correlation.

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In order to study a strength of adhesive joint, a joint strength of specimen, which consists of steel pin and color bonded by structural adhesive used in the previous study, is experimentally evaluated in a wide range of deformation rate by using an INSTRON-type material testing machine and a split Hopkinson pressure bar apparatus. A finite element simulation with the previously-proposed three dimensional constitutive model is performed under an impact loading condition. It is shown that the FE simulation used here is valid for a prediction of the impact deformation behavior of the adhesively bonded joint by comparing with the experimental result. A stress distribution of the adhesive layer in the pin-color specimen under an impact shear load is numerically studied. Finally, effects of the mechanical propoerties of the adhesive and the adhesive thickness on the stress distribution is clarified.

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The effect of the thickness of interlayer on stress singularity fields is evaluated using a boundary element method and eigen value analysis based on a finite element method. A model for analysis is a three-dimensional three-layered joint consisting of silicon, resin and FR4.5. All stress components are expressed as spherical coordinate systems in which origins are located at the vertex of each interface. They are derived from the transformation of coordinate system; from x^-, y^- and z^-coordinates to γ^-, θ- and φ-coordinates. Here, θ is the angle from z-axis, φ is the angle from side surface and γ is the distance from the stress singularity point. The intensity and the stress distribution of stress singular field at the vertex are investigated for various values of interlayer thickness. Comparing the order of stress singularity in two interfaces of silicon-resin and FR4.5-resin, the value of the order of singularity in the silicon-resin interface is larger than that in the FR4.5-resin interface. Furthermore, the intensity of singularity in the γ-direction at θ=90° and φ=45° is large as the thickness of interlayer increases. However, the thickness of interlayer influences scarcely on the intensity of singularity for stress singularity line. Therefore, the three-dimensional intensity of stress singularity newly defined at the vertex of each interface increases with increasing the thickness of interlayer.

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Flexural rigidity of a porous resin/Al laminate is estimated experimentally by means of the 3-points bending test. It can be seen from the results that the change in the magnitude of flexural rigidity of the laminate is convex with respect to its forming magnification. Therefore there exists the optimal value of the forming magnification of porous resin for the frexial rigidity. The neutral band in which the bending stress is free around the neutral plane of the porous resin/Al laminate beam is devised and the neutral band model is used for the calculation of the frexural rigidity of the laminate beam. The results obtained are good agreement with the experimental ones of the convex change in flexural rigidity with the forming magnification.

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The purpose of this study is to clarify the validity of the sphere indentation test method to evaluate the fracture toughness K_c of ceramic films deposited on the hard substrate, and to clarify the effect of bias voltages V_B on the fracture toughness K_c of ceramic films. TiN films were deposited onto three kinds of WC-Co substrates with different hardness using dc magnetron sputtering under various bias voltages V_B. Sphere indentation tests were carried out to determine the load for ring crack initiation P_f and the ring crack radius γ_f on TiN films using sphere indenters of varying diameter 2R. The fracture toughness K_c was calculated as the mode I stress intensity factor for a surface crack on TiN film using P_f and γ_f. The crack length c_i was assumed as the grain size of TiN films. The main conclusions are the following. (1) The residual stress δ_R of TiN thin films and the hardness H_u of thin films increase with increasing bias voltage V_B regardless of the substrate hardness. (2) Fracture toughness K_c decreased as increase in the diameter 2R in cases with a small 2R and gradually approached a constant value in cases with a large 2R. The K_c-2R relationships and the constant value of K_c are independent of substrate hardness. (3) Fracture toughness K_c increase as V_B is increased. That tendency is mainly due to the residual stress on TiN film.

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In a conventional process such as a ceramics thin film coating on steel after heat treatment in a furnace, the steel might be so softened by over heating. Therefore, we proposed a new method: heat treatment after a TiN thin film coating process. However, thermal deformation could be occurred in this process using a furnace. Therefore, the present study focuses on the application of laser quenching. The method causes thermal strain less than that in the furnace quenching. As experimental results, it is revealed that YAG laser quenching of the TiN film coated steel without film damages is very difficult because the film oxides and heat absorption increases immediately during laser irradiation. Therefore, we propose some solutions: First, a N_2 gas-assisting laser irradiation is performed to prevent from the oxidation of the TiN film. Second, an absorbent is applied on the film in order to increase the thermal absorption. As a result, it is clarified that the proposed method is effective to achieve laser quenching of TiN film coated steels without the film damage. Moreover, it is shown that the film hardness and adhesive strength maintains enough in this method.

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In this study fracture probability at thermal stress distribution is calculated with the dangerous volume quantification method that was proposed in the former report. Fracture stress calculation by thermal stress is based on finite element method with fracture temperature and aluminum creep properties. The fracture strengths predicted with the proposed method are appropriate to experimental results obtained by heat tests. The calculated dangerous volume intended for 90% of product in alumina's spray coating on aluminum layer is part of 96% or more of maximum stress. Therefore the dangerous volume calculation in thermal stress distribution is enough to think experienced dangerous volume caluculation method that dangerous volume is volume of 90% or more of maximum stress. And it is shown that fracture origin is located in the dangerous volume calculated with this study method and fracture strengths predicted with fracture origin size is almost equal to the fracture strengths predicted with this study.

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The fracture behavior of a light cure composite resin under impact tensile loading was studied using single-edge-cracked specimens. The impact load and displacement were measured with a Piezo sensor and a high-speed extensometer, respectively. The load and displacement diagram, i.e. the external work applied to the specimen was partitioned into three parts: the elastic energy left in the fractured specimen, the nonelastic energy due to viscoplastic deformation and the fracture energy for creating new surfaces. These energies were then determined and correlated with the fracture load. Energy release rates were also evaluated, and the results were discussed.

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Unstable crack growth under quasi-static loading condition is studied both experimentally and numerically in this work. Image analysis is applied to the experimental study. Stress field around the propagating crack tip is visualized by means of photo-elastic technique, and images of the unstable crack growth and the visualized stress field around the propagating crack-tip are captured by the ultra-high-speed camera with the frame rate of 1000000fps. Images are successfully captured at every 0.3mm crack growth. Next, the numerical simulation technique to simulate the unstable crack growth without the rearrangment of nodes and elements is proposed. In the proposed technique, X-FEM is extended to include the dynamic phenomena. The result of the simulation is directly compared with the experimental observation. As a result of comparison, numerically simulated fringe patterns have a good agreenment with the experimentally observed ones, and hence, it is shown that the proposed algorithm has a sufficient accuracy.

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A closed-form expression of the stress intensity factor is derived for a problem of straight crack in an infinite plate under thermal stresses induced by a temperature rise at an infinitesimal area. The present solution is applicable to wide range of uncoupled thermoelastic problems and is especially useful to understand the mechanical behavior of cracks in thermal stress cleaving (TSC). For instance, the present solution is useful for the prediction of an optimal temperature distribution in TSC, which is a function of various conditions such as shape of the plate, crack path, cleaving velocity and so on. Some basic problems of TSC formerly analyzed by the use of thermoelastic fields induced by a heat source were examined to confirm the applicability of the present solution.

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Wedge-shaped defects are frequently observed on the cervical region of the human tooth. Previously, most studies explained that such defects are caused by improper toothbrushing. However, recent clinical observation suggested that the repeated stress originated from occlusal force may induce the formation of wedge-shaped defects. In this study, therefore, two-dimensional human tooth model after the wedge-shaped defect is restored with composite resin is analyzed by using the finite element method. To obtain the intensity of the singular stress accurately, a method of analysis is discussed for calculating generalized stress intensity factors, which control the singular stress around the tip of the defect. Finally, the relationships between the stress intensity and occlusion are discussed. It is found that large occlusal forces perpendicular to the tooth axis are harmful to the resin that is bonded to dentin.

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In this study, the effect of the ultrasound wave stimulation for the hydroxyapatite crystalline formation on bioactive pure titanium surface was evaluated in vitro on purpose to accelerate the bone-binding to bioactive material. Pure titanium was used as a specimen, processed in the chemical treatment and the heat treatment, and soaked in simulated body fluid (SBF) under ultrasound waving for planned time-periods. The surfaces of specimens were observed by using Scanning Electron Microscope (SEM), X-ray Diffraction etc. to assess the state of apatite deposition. In result, the SEM etc. showed that more rich and fine layer with rich calcium and phosphate compounds covered on the surface in ultrasound waving group as compared with the non-ultrasound pulse group. The measurements of mass of specimens also indicated the efficiency of ultrasound waving for apatite formation. These findings suggested that the nucleation and crystallization of apatite might be promoted by micro moving and cavitation of ultrasound waving and the ultrasound waving had clinical potential to improve the osteointegration for medical implant.

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Repeated plate impact tests on medium carbon steel were carried out on the identical target plate being impacted by flyer plate of the different thickness in each impact test. Evolution of spall damage under repeated impacts was evaluated nondestructively with the B- and C-scan images by low frequency scanning acoustic microscope as well as the ultrasonic variables (ultrasonic velocity, amplitude ratio of second to first backwall echo and backscattering intensity). The spall damage density and sizes after the second impact have increased in the impact surface side, when the second impact stress is lower than the first. On the other hand, when the second impact stress is higher than the first, the spall damage has increased in the back surface side. The change in B- and C-scan images of the spall damages under repeated impacts is well correlated with the change in ultrasonic variables. These methods give us an advanced means to evaluate nondestructively spall damage and to make clear the mechanisms of the spall damage growth under repeated impacts.

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The equivalent stiffness of clamped plates should be prescribed not only to evaluate the strength of bolted joints but also to evaluate deformation and vibration characteristics of practical structures with many bolted joints. The axial stiffness and bending stiffness of clamped plates were evaluated by using Finite Element (FE) analyses while taking the contact condition on bearing surfaces and between the plates into account. We constructed the FE models for bolted joints tightened with M8, 10, 12 and 16 bolts and plate thicknesses of 3.2, 4.5, 6.0 and 9.0mm, and the axial and bending compliances were precisely evaluated. These compliances of clamped plates were compared with those from VDI 2230 codes (German Engineering Society), in which the equivalent cylindrical and conical compressive stress fields in the plate had been assumed. The compliances of the clamped plates for the preload states were estimated between the predictions as the cylindrical and the conical fields. Meanwhile, the axial and bending compliances of FE analysis can basically be expressed by the VDI 2230 (2003) with the conical field. However, the VDI 2230 (2003) gives the slightly large axial stiffness, and thus the internal force borne to the bolt is predicted in a little bit dangerous failure. Also, it cannot follow the case of clamped plates with different thickness due to assumption of its model.

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Copper electroplating is widely used to fabricate Large-Scale Integration (LSI) whose components are from nanoscale wires to microscale bumps because of its excellent via/trench filling ability, good adhesion and lower process temperature and low cost. Monitoring and controlling current densities on a plated surface are necessary to electroplate the object optimally. This paper focuses on monitoring the current densities on a plated surface and a novel technique to estimate them from the electric potentials in the plating cell has been developed. An electric potential at a point can be measured by using a capillary inserted in the cell. Evaluation of a physical quantity on a boundary from known values in the domain is an inverse problem. In the present method, Tikhonov regularization on the mathematical model of the electric field derived by boundary element method is applied to solve the inverse problem. In addition, the method plots polarization curves which describe the relationships between electric potentials and current destinies on the boundaries with the inverse solutions and revises the solutions. Measurement experiments under several electroplating conditions were performed to demonstrate the validity of the proposed technique. The estimation results by the proposed method are in good agreement with the numerical results by the conventional method using sample polarization curves. These results show that this method can be applied to practical electroplating processes in LSI fabrications.

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Atomistic simulation of tension of a thin film containing a notch on its surface is performed and its mechanical stability is analyzed by solving the eigenvalue problem of the Hessian matrix taking into account all the degrees of freedom of the atoms in the system. The value of an eigenvalue designates the curvature of the potential energy landscape in the direction of the corresponding eigenvector, which indicates the deformation mode; meaning that the system is unstable when any eigenvalue is zero or negative. At a strain where all the eigenvalues are positive, atomic fluctuation due to finite temperature may cause instability such as a dislocation nucleation. We have revealed that the path of the activated instability, dislocation emission from the notch, can be written by a linear combination of the eigenvectors having small eigenvalues. The energy landscape has a much lower hill along the mixed-mode path than along any single-mode paths.

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