Hidenori Yoshimura

Simplified three-dimensional simulation of rotary piercing of seamless pipe by rigid–plastic finite-element method

Abstract A method for simulating three-dimensional deformation in rotary piercing of pipes from round bars with skewed rolls in a realistic computing time is proposed on the basis of the rigid–plastic finite-element method using generalised plane-strain modelling. In this method, the rotary piercing is approximated as a roll forging process, and the elongation of the workpiece in the rolling direction is kept uniform in the cross-section. The effect of the twisting shear deformation is included in the generalised plane-strain modelling to improve the accuracy of the calculated results. The calculated shapes of the deformed workpiece are in good agreement with the experimental ones for plasticine workpieces. In addition, the occurrence of a central crack in the rotary piercing is predicted from the calculated history of the hydrostatic stress and equivalent strain by means of the criterion of ductile fracture.

Evaluation of Scale Dependent of Fast Fracture Strength of Micro Component

In order to design the MEMS having good reliability, it is necessary to know the mechanical properties such as strength, fracture toughness and fatigue strength of micro components. In this paper, the fatigue testing machine was made. The examination of the fast fracture strength against the several kinds of specimens which dimensions were different each other was carried out. And volume dependency of the strength was discussed.

Parallel Processing of 3‐D Rigid‐Plastic Finite Element Method Using Diagonal Matrix

To realize large‐scale 3‐D simulation of metal forming processes, the 3‐D rigid‐plastic finite element method using a diagonal matrix is extended to parallel processing. In the present method, uncoupled equilibrium equations expressed by a matrix with three rows and three columns at each nodal point are repeatedly calculated in turn without solving the large global simultaneous equations. The method using a diagonal matrix is suitable for the parallel processing because of the iterative calculation at each nodal point. The convergence of the solution is examined in the simulation of upsetting of rectangular block with an inclined tool. The computing time is improved by the parallel processing.

Simplified Three-Dimensional Simulation of Rotary Piercing of Bar by Rigid-Plastic Finite Element Method.

A method for simulating three-dimensional deformation in rotary piercing of a seamless pipe from a round bar with skewed rolls is proposed on the basis of the rigid-plastic finite element method using generalized plane-strain modeling. In this method, the rotary piercing is approximated to be a roll forging process, and the elongation of the workpiece in the rolling direction is kept uniform in the cross-section. The effect of the shear deformation in the rolling direction is included in the generalized plane-strain modeling. In addition to the short computing time, the treatment of the contact boundary conditions for the rolls and plug becomes simple. The effects of working conditions on deformation behavior and the occurrence of a central crack in the rotary piercing are examined.