Strengthening effect of unshearable particles of finite size: A computer experimental study

Equilibrium configurations of a dislocation interacting with randomly distr ibuted unshearable obstacles of finite size under an applied stress are ana lyzed. Ashby's critical dipole spacing Q' argument for the self-stress effe ct of dislocations is utilized but analysis suggests that the spacing Q' va ries with the local obstacle distribution as well as with the obstacle shap e. Computer simulations of a dislocation slip process through circular or l inear obstacles, that are extensions of earlier work by Forman ct al., were conducted. The dependence of the strengthening stress on the obstacle size was found to be less than that predicted by equations currently in use, pa rticularly for linear obstacles. New, modified Orowan equations are suggest ed for the strengthening effects due to spherical, rod-like, and plate-like obstacles. The effect of the orientation distribution of the linear obstac les demonstrated in the simulation is in agreement with recent experimental observations. (C) 1999Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.