Solution Methods for Thermo-elastic-Plastic FEM and Its Application to Centrifugal Casting Mold

Abstract

Three solution methods for thermo-elastic plastic finite element analysis were studied with special emphases paid to the treatment of elastic-plastic transition. These are the iterative convergent method using “effective stiffness matrix” and two modified r_min methods I and II. The computational results obtained were compared with each other in terms of the “followability” of the equivalent stress and the flow stress of the material.
A simple and efficient algorithm to automatically determine time increment was also presented. It was shown that when this algorithm is combined with the modified r_min method II highly accurate solution can be obtained with less thermal load increments.
Computations were performed on the basis of the modified r_min method II on centrifugal casting molds to analyze the influences of casting parameters on the stress-strain state of the molds.
The results revealed the importance of the adiabatic effect of refractory coating to enhance the thermal fatigue resistance of the bore surface of mold. The influences of the pouring temperature, the mold wall-thickness and the preheating temperature of mold were also clarified.
Mold warping or bowing was also discussed in conjunction with the “plastic work over a mold”, which was found to be decreased considerably by increasing the thermal resistance of coating, by lowering the pouring temperature and by thickening the mold wall.