本研究は、安価で誰もが使用できるセンサシートを用いて表面形状を測定可能な接触センサシステムの開発することを目的としている。開発にあたり、センサシートに荷重をかけた際の測定対象物体の表面形状の変位を算出するを用いた計算式が正しいかどうか検証するためにを用いた計算式により算出した応力とセンサシートに荷重をかけ測定した応力を比較した。その検証実験の結果を本論文は記載する。

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From the point of view that fly ash has very fine particles which included silica and alumina component of ceramic material, composite materials using fly ash and aluminum powders were fabricated by spark plasma sintering technique. The bending strength showed the constant value of 530 MPa at the fly ash content lower than 9.1 %, however the strength decreased monotonically at the fly ash content higher than 9.1 %. In addition, the bending fracture strain decreased with increasing the fly ash content. From the fracture surface observation, the crack propagation was recognized as bypassing along interface of fly ash particle. This phenomenon indicated that the fly ash particles played a role for suppressing the crack propagation. By assuming fly ash particle as spherical shape, the Mises stress distributions were analyzed by finite element method. The high stress concentrated near interfaces of fly ash particles, because deformation degree of aluminum alloy matrix and fly ash were different. This result suggested that the cracks occurred around fly ash particle combined each other, because the agglomerated fly ash particles becomes large size when increasing the fly ash content. And the simulation results showed the agreement with experimental results of fracture strain on the bending test.

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  Owing to its low specific gravity together with high strength and high ductility, aluminum alloy die castings are being increasingly applied to the body structural parts to reduce the weight of automobiles. Generally, the tensile test is used for evaluating the properties of die castings, but this method tends to overestimate the effects of porosity defects. Focusing on the main property required of body structural parts, i.e., the ductility which guarantees that the parts will not break even if bent in case of collision, we examined the possibility to evaluate this ductility by the three-point bending test.

  In the tensile test, porosities reduce the actual cross-sectional area of the test piece, thus their macro effects on mechanical properties can be assessed. However, it is difficult to evaluate their effects on surrounding local ductility. On the other hand, it was found that with the 3-point bending test, the influence of porosities on ductility can be assessed according to their positions with respect to the pushing point, i.e., the collision site. Artificial defects were therefore formed and their effects on ductility evaluated. The results showed that porosities more than 8 mm away from the pushing position or more than 0.5 mm inside the surface of castings do not have significant impact on bending ductility.

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Restoration of an edentulous space with a removable partial denture presents various problems of the design of a retainer set on a distal molar, when the molar shifts in angle or position. The two-dimensional finite element technique was used to analyze the design factors of the retainer's arm influencing the periodontium of an abutment tooth, for a direct retainer being set on a tilted molar.
The results obtained are as follows:
1. When only a retentive arm is used, the von Mises stress of the periodontium increases as the shifted position or angle of a retentive tooth increases.
2. When both retentive and reciprocal arms are properly located, von Mises stress is less than what with the retentive arm only. It is suggested that the reciprocation is effective for the stress -relaxation of the periodontium of a abutment tooth.
3. When both retentive and reciprocal arms are properly located and a retentive force is equal to a reciprocal one, the value of von Mises stress is within 0.10 kg/mm².
4. Effective design factors of a retainer's arm for the stress relaxation of the periodontium are suggested.

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プリント基板内のビア構造は構成する材料の膨張係数の差により、熱疲労により信頼性に大きな影響を受ける。本研究ではビア構造の故障のその場で監視・測定することにより、設計時や信頼性試験時、また実装後使用時に於けるビア構造の寿命を容易に予測できるシステムを構築することを目的とする。本報告では多層積層プリント基板内の様々なビア構造(スルーホールビア、マイクロビア、埋め込みビア、積層ビア等)に関して、熱疲労に対する信頼性の違いを有限要素法によるシミュレーションによって比較し、寿命予測を容易に行えるパラメータの比較・検討を行う。

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  In precision casting where production is of comparatively small scale, the use of photo-solidified polymer models in place of conventional lost-wax models can be recommended. In precision casting using photo-solidified polymer models by the same process as that using wax models, the mold may fracture due to thermal stress arising in the baking process where the model is melted and evaporated, because polymer has higher rigidity than wax. The polymer baking process was simulated numerically to predict the occurrence of mold fracture and experiments were conducted to verify the prediction. The results confirmed that there exists consistency between the fracture prediction and crack phenomenon. Improved productivity and reliability are therefore greatly expected with the application of this technique using photo-solidified polymer models to mold manufacturing for precision casting.

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The phenomena of emerging stresses on a moving plate were calculated using the general-purpose mechanical analysis software Adams, MSC. The simulation results were verified by an experiment in which strain gauges were attached to the plate which slides along with a rail. The simulated stresses emerged at the plate were close to values measured by the strain gauges in the experiment. Also, geometry optimization was conducted using the general-purpose optimization software OPTISHAPE-TS,Quint. The geometry optimization not only improved stiffness of the plate, but also decreased the mass of the plate in simulation and experiment.

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Due to the need of increasing fuel efficiency, the weight of springs and many other components in automobiles need to decrease their weight. The weight reduction can be achieved by increasing the strength of material, however, it may cause the problems of reduced workability, toughness and durability. Even increasing the material strength, enhancing their fatigue properties will expand the service life of them, i.e., delaying the initiation of cracks. A crack initiation is caused by the accumulation of dislocations, which is resulted by yielding on the surface due to repeated loading. Finite element analysis was recently available to apply the stress distribution analysis of a complicated shape, e.g., a helical coil spring subjected to compression loading. In this research an attempt was made to presume the point of the fatigue fracture initiation in coil springs according to the distribution of Mises stress, that is the crucial index of yielding phenomenon. The point inside and surface of a coil spring wire at which the Mises stress has its maximum value is the same place as a crack nucleation during fatigue progress according to referring experimental papers.

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This paper deals with a three-dimensional stress analysis for link chains subjected to tensile loads. The analysis was done using the finite-element method to examine the strength of the link chains. The effects of the dimensions of link chains on Misess's stress at the border between the curved part and the straight part in the link, and at the outer part, of which the inner part contacted with the inner part of the other link, were shown through numerical calculations. For verification, photoelastic experiments and measurement of strain were performed. The analytical results were in fairly good agreement with the experimental results. It was clarified that the strength of link chains can be improved by optimizing the link pitch, the link width, shape of the link section and compressed depth. Discussion is also presented on the estimation of the strength of the link chain subjected to tensile loads.

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In this report, adhesive strength criteria are investigated experimentally and analytically The cylindrical butt joint specimen subjected to various combined tensile and torsional loadings and the round bar butt joint specimen with various thickness(30〜1000μm) of adhesive layer are used for the experiments Principal stress, principal strain and von Mises stress distributions at the adhesive interface of these specimens under the critical load are obtained by the elasto-plastic finite element analysis using MARC As a result, the mean value of von Mises stress distribution at the singularity area which is 1 % of adhesive thickness, is found to be the most dominant factor in determining the adhesive strength criterion Also, it is found that the strength of adhesive joints decreases linearly with increasing adhesive thickness in log-scale The critical stress can be obtained directly as the maximum shear stress at fracture in torsion test of a round bar butt joint specimen without any numerical analysis

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The tribological properties of silicon with and without water boundary lubrication with silicon, silicon carbide and a diamond tip were studied and the following results were obtained. (1) The friction coefficient between silicon and silicon or silicon carbide tips is as high as μ=0.2∼1.0, with and without lubrication. Surface damage occurred due to the adhesion between similar materials. (2) When a diamond is used as the opposite tip, the friction coefficient is as low as μ=0.09∼0.16 without lubrication. With water boundary lubrication, the friction coefficient is as low as μ=0.07. Damage is not observed on surfaces either with or without water boundary lubrication. (3) To determine the reason why sliding with the diamond tip did not result in damage, stress analysis was carried out using the boundary element method for each combination of materials. The maximum Mises stress was observed inside the silicon and diamond bulk when silicon and diamond were tested. However, the maximum Mises stress for the silicon with silicon and silicon carbide with silicon combination was observed.

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The failure mode so called local failure could occur at structure discontinuities. Local failure is caused from Von Misses stress and hydrostatic stress. So the triaxiality factor considering hydrostatic stress has been introduced to evaluate local failure based on Misses type criteria. However the mechanism of local failure has not been clarified. For this reason it is not easy to say that triaxiality factor is properly applied to evaluate local failure. Thus the purpose of this study is to clarify the relation of local failure and triaxiality factor with tensile tests of notched bars and FEM simulation. As a result, it is clarified that triaxiality factor doesn't always indicate difficulty occurs of plastic deformation. Furthermore it is clarified the relation of local failure and triaxiality factor by introducing the Von Misses stress - hydrostatic stress plane and fracture curve.

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Atomic force microscope (AFM) nanofabrication properties based on mechano-chemical processing due to diamond tip sliding on silicon in ambient atmosphere are studied. The processed height and depth dependencies on load and diamond tip radius were evaluated. Diamond tip of about 200nm radius sliding produces protuberances on the silicon surface. In contrast, about 50nm radius tip sliding produces grooves on the silicon surface. Using about 100nm radius tip, both protuberance and groove are produced. To clarity the mechanism of silicon protuberance and groove processing by diamond tip sliding in an atmosphere, the contact stress analysis were perfomed by boundary element method. Oxidation of silicon is speculated to be caused at the rear edge of sliding contact area that the elongation stress is the highest. This reaction forms silicon oxide in both protuberance and groove processing. To clarify the possibility of these processed parts on silicon surface for the application to wet etching mask, etching properties with KOH solution were evaluated at room temperature. The sliding of diamond tips produces the silicon oxide layer that works as KOH etching protective mask. AFM mechanochemical processing layers are expected to act as etching mask for selective wet etching.

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In this paper, we present a parameter-free free-form optimization method for the strength design problem of a shell structure. The maximum von Mises stress is minimized under a given volume constraint condition. The optimum design problem is formulated under the assumptions that a shell is varied in the out-of-plane direction to the surface and the thickness is constant. The issue of non-differentiability inherent in this min-max problem is avoided by transforming the singular local measure to a smooth differentiable integral functional by using the Kreisselmeier-Steinhauser function. The shape gradient function and optimality conditions theoretically derived are applied to the free-form optimization method for shells. With this method, the smooth optimal free-form of a shell structure is determined without any shape design parameterization, while minimizing the objective functional. Design examples are presented to demonstrate the validity of this free-form optimization method for minimizing the maximum stress of a shell structure.

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Although bladed disks of turbomachinery are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all blades on a disk are slightly different due to the manufacturing tolerance, the deviation of the material property, the wear during operation, and so on. These small variations break the cyclic symmetry, and split the eigenvalue pairs. The actual bladed disks with the small variations are referred to a mistuned system. Many researchers have studied mistuning, and main conclusions are while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on the blade flutter (the self-excited vibration). Although such mistuning phenomena of bladed disks have been studied since 1980s, almost all studies focused on the amplification factor of the displacement response, and few studies researched the amplification factor of the vibratory stress response. Therefore, in the previous paper, authors studied the amplification factor expressed by the vibratory stress for the lower modes of the bladed disk, using the simple assumption. In this study, the mistuning effect expressed by the vibratory stress for the lower and higher modes are examined, using the reduced order model without any assumptions. First, formulation for evaluating the mistuning effect expressed by the vibratory stress is derived, using the reduced order model SNM (Subset of Nominal Modes). Second, the frequency response analysis of the mistuned simple bladed disk consisting of flat plates is carried out systematically. Finally, comparing the amplification factor of the displacement response with that of the vibratory stress response including the synthesized stress (Mises stress and the principal stress), mistuning phenomena expressed by the vibratory stress are clarified.

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In order to examine the sealing mechanism of a connection with a metal gasket, the sealing test according to JIS B2490 and FEM analysis were carried out. The dimensions of platen used in the test are according to JIS B 2490 and the metal gasket types are chosen as metal flat and ring joint gasket. The material of the gaskets was aluminum. The ring joint gasket types are chosen as octagonal and oval. The effect of internal pressure on the sealing performance of connection with the metal flat gaskets was measured. The relationship between the gasket compression stress and amount of leakage through inter faces on the metal flat gasket was obtained. And also, the relationship between compression load and amount of leakage through inter faces on the ring joint gaskets was obtained. The von Mises stress distributions on the interface on the metal gaskets were calculated using FEM. Using the results of sealing test and FEM, it was suggested that the sealing performance was improved, when the von Mises stress more than the gaskets material of the yield stress adequately. Furthermore, it was suggested experimentally that the ratio of the maximum of von Mises stress in the gaskets material of yield stress was 1.015.

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