[in Japanese]

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[in Japanese]

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A comparative review of two failure models using Charpy impact test simulations is presented. The failure models are based on total formulation and incremental formulation. The former model is a conventional one. The latter one is a generalized damage model considering deformation history. A Charpy impact test simulation using the incremental formulation successfully predicts experimental results where no rupture behaviors were observed for a polycarbonate. The same simulation using the total formulation predicts rupture behavior around the area which is subjected to compression state, then tension state. It is found that considering deformation history is important in predicting rupture behavior of products which are subjected to complex changes of state of stress.

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The Riera approach is re-evaluated using full-scale experimental results of aircraft engine model impact on RC wall. Impact force-time history obtained from the Riera approach is used to analyze RC wall, and numerical and experimental results are compared. Sensitivity of parameters used in the estimation of impact force on the impact response is discussed. The study is useful as it provides better understanding and rational basis for the estimation of parameters used in the Riera approach for analysis of aircraft impact on RC structures.

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[in Japanese]

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[in Japanese]

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In JAEA, the three-dimensional two-fluid model analysis code considering the supercritical pressure water based on ACE-3D (Advanced Code for Evaluation of 3-Dimensional two-phase flow) has been developed to establish the thermal-hydraulics design for the Super Critical Water Reactor (SCWR). In this paper, in order to evaluate the prediction accuracy of ACE-3D on the heat transfer-characteristics such as the heat transfer deterioration near the pseudo critical point, a numerical analysis of the supercritical pressure water based on ACE-3D has been conducted for the IAEA benchmark test problem. Experimental data is obtained for supercritical pressure water in a heated pipe for both upward and downward flow. Also, the distribution in length of the heated tube section of the wall temperature was compared with the predicted results and the experimental data.

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Thermal hydraulic analyses of upward and downward flow of supercritical pressure water in a simulated fuel assembly were performed by using ACE-3D/BFC to investigate the influence of coolant flow direction upon heat transfer in fuel assemblies of the supercritical pressure water reactor. As a result, it was clarified that the rod surface temperature of the downward flow case was higher than the upward flow case. Supercritical pressure water flow from the inner region of the simulated fuel assembly to the outer region increased when the fluid temperature approaches the pseudo critical temperature. In the downward flow case, this supercritical pressure water flow was greater than that of the upward flow case. The effects of this flow led difference of rod surface temperature.

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In the thermal-hydraulic design of supercritical water-cooled reactors, it is required to establish a thermal-hydraulic analysis method which can simulate the heat transfer and fluid flow characteristics of supercritical fluids precisely. Because, there are not easy to conduct thermal-hydraulic experiments using the simulated fuel bundles since the supercritical fluids become high pressure. Then, using the currently numerical analysis method, thermal-hydraulics in four fuel bundles were analyzed numerically and their characteristics were clarified quantitatively.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Generally, it is useful to determine the inelastic stress-strain relations of engineering materials. But, it takes many specimens, big testing systems, much time and so on to get the material data. In this report, much simple determination method is established using the micro-indentation data (Load-Depth curve) and inelastic FEM analysis by LS-DYNA with the Karman Filter computational program. One of the important points of this method is the type with only 4 parameters of the expression for inelastic stress-strain curves. As the example material, Polypropylene and A1N powder reinforced Biodegradable-Polymers are tested and the inverse analysis based on the obtained load-depth curves are performed to determine the 4 parameters of each expression. It is confirmed that this method is effective and useful by comparing the analytical curves and the experimental stress-strain curves obtained by usual compression tests.

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[in Japanese]

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The mal-uniformity phenomenon of plate heat exchanger has not disclosed clearly. This work enhances the 3D modeling of corrugate channels of brazed plate heat exchanger completely, covering geometry in inlet and outlet distributor zone. The full acrylic corrugated channel is as test section used as validator, tested in two-phase flow mode in order to track the flow distribution clearly. It is revealed that the mal-uniformity is generated by geometry of inlet and outlet distributor zone for single phase flow and it tend to be promoted by flow pattern, buoyancy effect as well as geometry of inlet and outlet distributor zone for two-phase flow.

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The thermal performance of a horizontal slinky-loop ground heat exchanger was investigated. A numerical simulation for this configuration was developed using FLUENT. A continuous operation of 12-hour a day was applied in the simulation.

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In the present study, the conservative integral formulation is developed in order to obtain the intensity of singularity at a vertex of the interface in three-dimensional dissimilar material joints. Models with various element sizes and various integral areas are used to investigate the influence of the integration area on the accuracy of the results. The results are compared with those obtained from the boundary element method (BEM) using a curve-fitting technique in order to calculate the intensity of singularity.

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The objective of the present investigation is to determine the Stress Intensity Factors (SIF) along crack front of a 3D planar crack in an infinite solid under remote tension. In order to calculate the SIF, the Body Force Method (BFM) is used. In this study, multiple interacting cracks in an infinite solid are analyzed to determine the stress field as well as stress intensity factors for crack tips. In the present method the surface of the crack is expressed by the aggregation of planar triangular elements. In order to improve the numerical accuracy polar transformation scheme was introduced.

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In this study, the theoretical analysis of a transient piezothermoelastic problem is developed for a two parallel cracks in arbitrary positions of a piezoelectric material strip under thermo-electric loadings. The crack faces are supposed to be insulated thermally and electrically. By using both the Laplace transform and Fourier transform, the thermal and electromechanical problems are reduced to two systems of singular integral equations, respectively, which are solved numerically. A numerical method is employed to obtain the time dependent solutions by way of a Laplace inversion technique. The intensity factors versus time for various geometric parameters are calculated.

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