EFFECTS OF CREEP AND STRAIN ON THE THERMAL-STABILITY OF ROD EUTECTICS

The thermal stability of a rod eutectic structure is investigated by i ncluding strain and creep effects. The rod eutectic is modeled as an e lastic rod embedded in an elastic matrix and power law creep material. Previous investigators performed the analysis of an elastic rod in an elastic matrix. Through our analysis, the influence factor of the cre eping matrix, OMEGA1, is found as OMEGA1 = {3K(B)epsilon/square-root 3 (K + 4G/3)delta2}m (sigma0/3K(B)epsilont(m)) {1-(r2(2)/r0(2))m}/square -root 3m, where K(B) is the bulk modulus of the rod, epsilon is the mi sfitting parameter, K and G are the bulk and shear modulus of the elas tic matrix respectively, sigmaBAR = sigma0epsilon(m)BAR is the constit utive equation of the creep material, t is the elapsed time, delta is the ratio of the rod radius to that of the elastic matrix, and r2/r0 i s the ratio of the elastic matrix radius to the half distance of the r od spacing. If OMEGA1 is small, the contribution of creep is neglected , and structural stability is approximated by the solution obtained wi th the elastic rod and matrix. In that case the stability criteria is identical with that obtained by previous investigators. However if mOM GEA1 is increased, the contribution of creep to the stability solution is significant and the creeping material destabilizes the structure. The amplitude of the growth rate A(lambda) approaches that obtained by the elastic rod and matrix model with increasing elapsed time. The ti me to reach the A(lambda) of the elastic rod and matrix model is stron gly dependent on the strain rate hardening exponent (m). There exists a value of m to maximize instability. The stability of the rod obtaine d by the present analysis is compared with that obtained by using the elastic rod and matrix [A. M. Mayes and M. 0. de la Cruz, Acta metall. 37, 615 (1989)].