野口 博司

種々の配向をもつ一方向強化積層板の切欠き特性 : 第1報, 異方性板の応力集中問題の汎用解析法と弾性場の評価

The uni-directional FRP have very complex stress fields because of their anisotropy. Many researchers have reported the methods to calculate stress intensity factors or stress concentration factors. But only these parameters are not sufficient to evaluate the strength of materials in structures. The mechanical parameter for the equivalence of elastic fields also is required. In this paper, the characterization of the elastic fields near a notch root in an anisotropic plate is discussed. To consider the problem, the versatile analysis based on Body Force Method is developed. And the evaluation method of the elastic field near a notch root is developed with Stress Intensity Factor under the normal strain criterion.

(分子動力学+マイクロメカニクス)接合モデルによるき裂進展過程のシミュレーション : 第2報, MD領域移動モデルの提案

Molecular dynamics is applicable for only a small region of simulation. To simulate a large region, it is necessary to combine molecular dynamics with continuum mechanics. In the first report, we proposed a new model in which molecular dynamics was combined with micromechanics. Namely, we applied a molecular dynamics model to the crack tip region and a micromechanics model to the surrounding region, respectively. In this model, however, crack propagation simulation must be stopped when the crack tip reaches to the boundary of the two regions after the crack propagation. Therefore, in this paper, we improve the previous model by allowing the movement of the molecular dynamics region. Theoretically, the process of the crack propagation can be simulated endlessly with this advanced model. In order to examine the validity of the advanced model, we use α-iron in simulation. It is found that the result based on this advanced model is equal to the result with the previous model. Moreover, the result is almost equal to the Rices solution.

(分子動力学+マイクロメカニクス)接合モデルによるき裂進展過程のシミュレーション : 第1報, モデルの提案とその検討

Molecular dynamics is applicable for only a small region of simulation. To simulate a large region. it is necessary to combine molecular dynamics with continuum mechanics. Therefore, we propose a new model in which molecular dynamics is combined with micromechanics. We apply a molecular dynanics model to the crack tip region and apply a micromechanics model to the surrounding region. Problems exist at the boundary. In this study, we solve the boundary problems and devolop a method for combining molecular dynamics with micromechanics. We make possible the simulation of the process of crack propagation and dislocation increase. In order to examine the vaildity of this model, we use α-iron in simulation. If the proposed model is valid, stress and displacement must vary continuously across the boundary between the molecular dynamics region and the micromechanics region. Our results show that the two parameters vary continuously across the boundary.

短炭素繊維強化ポリアミド6.6のねじり疲労過程 : 回転曲げ疲労との比較

In this paper, torsional fatigue tests and additional rotating-bending fatigue tests were carried out on the injection moulded short carbon-fiber reinforced polyamid 6.6 composites. The fatigue mechanism in the composites was clarified through successive surface observations using the replica method. Moreover, the mechanism of the torsional fatigue was compared with that of the rotating-bending fatigue. The fatigue cracks in both fatigue tests are initiated along fibers aligned in the direction of the principal stress. In the case of the rotating-bending fatigue test the fatigue crack propagates finally at right angles to the direction of the principal stress. However, the cracks initiated along the fibers in the torsional fatigue test can not propagate under high-cycle fatigue. On the other hand, the fatigue cracks initiated from fibers aligned in the direction of the principal shear stress can propagate, and reach to final fracture. From the comparison between bending and torsional fatigue tests the fatigue process of this material under the condition of an arbitrary combined stress can be estimated.