CONTAINER INFLUENCE ON SHRINKAGE UNDER HOT ISOSTATIC PRESSING - II - SHAPE DISTORTION OF CYLINDRICAL SPECIMENS

Finite element modeling of the cylindrical specimen's shape distortion due to the container influence under HIPing is carried out. It is ass umed that the mechanical behavior of the powder and the container obey s power law creep equations, and an extremum principle of minimum ener gy dissipation is taken as the basis of the finite element approach. T he specific features of the proposed numerical methods are the utiliza tion of special axisymmetrical shell elements for the container and th e iterative approach of the viscous approximations for the solution of the nonlinear flow equations. It is noted, that the container influen ce on the shape change of the specimen depends on the magnitude of the power law creep exponent and distortions are more intensive in the ca se of low temperature creep. The method for the estimation of the cont ainer ribs' influence on the shape deviation is proposed. In many case s, it is possible to produce a precise final shape of the part by the determination of the initial shape of the porous specimen. The iterati ve method for the prediction of the necessary initial shape is put for ward. The method is based on the use of reverse calculations from the final to the initial shape. (C) 1998 Elsevier Science Ltd. All rights reserved.