Papers by Author: Yasuhiro Kanto

Abstract: This paper demonstrates sensitive analyses of probabilistic fracture mechanics (PFM) for reactor pressure vessel (RPV) during pressurized thermal shock (PTS) loading, and comparison of our calculation with the results of the international round robin (RR) analyses in Asian countries (Korea, Taiwan and Japan). The international Round Robin activity was performed in PFM sub-committees in the Atomic Energy Research Committee of Japan Welding Engineering Society (JWES) in conjunction with Korea and Taiwan research groups. The purposes of this program are to establish reliable procedures to evaluate fracture probability of reactor pressure vessels during pressurized thermal shock and to maintain the continuous cooperation among Asian institutes in the probabilistic approach to nuclear safety. Some parameters to RPV failure probabilities are chosen to evaluate their significance quantatively. The differences caused by selection of analyzing programs and some input parameters will be discussed.

Abstract: A new triangular element of Hermitian type, i.e., the degrees of freedom includes differentiation of value as well as value itself, is proposed and XFEM formulation is demonstrated. Some numerical examples are also shown.

Abstract: In this paper, a general post processing program for J-integral calculation is developed to apply to arbitrary shaped cracks in a three dimensional body. Usually J-integral calculation programs are options for specific stress analysis programs and they are not applicable to results from different analysis programs. In most cases, there are many limitations in analysis models or shapes of cracks. This situation is not favorable for users. This paper will demonstrate a development of a post-processing program to calculate J-integral for arbitrary shaped cracks in a three dimensional body. This program requires only discrete data of displacements and stresses at nodal or numerical integration points. Users can use their own programs for stress analyses and calculate J-integral after that. In this paper, errors in approximation will be discussed as the first stage of the development.

Abstract: To better understand the behavior of stresses generated inside a kidney stone by direct pulse impingement during extracorporeal shock wave lithotripsy (ESWL), numerical analyses are performed in this work. LS-DYNA, an explicit Finite Element code for non-linear dynamic analysis is employed to investigate the effect of stone geometry to the stress field evolution inside the stone when subjected to short pulse wave. Circular disks with parts removed from the front and the back are used to model the stones that assumed have already had initial fracture. The other variation of spherical geometry such as ellipse is also considered in the numerical calculation.

Abstract: This paper proposes an application of the inverse analysis to estimate the elastic response ahead of the crack-tip of a one-point bend specimen. The difficulty of the problem lies on determination of the impulse response function that relates the elastic response to a unit applied impact force which is numerically ill-posed. Two iterative numerical regularization schemes are proposed, first is a time-domain regularization based on the conjugate-gradient method and second is a frequency-domain regularization based on an optimal filter approach. Both schemes are evaluated by using the data obtained from an impact experiment. The result shows that the estimation error is about 18.0%.