FINITE-ELEMENT EVALUATION OF ELASTIC ACCOMMODATION ENERGIES DURING ROOM-TEMPERATURE ALPHA-BETA-HYDROGEN TRANSFORMATIONS IN THE NIOBIUM HYDROGEN SYSTEM - PLANE-STRESS FORMULATION

A plane stress finite element model, based on the initial strain appro ach, has been proposed to evaluate elastic accommodation energies duri ng solid state hydrogen transformations. Elastic accommodation energie s as a function of transformation progress have been obtained for the forward and reverse hydrogen alpha-beta transformations in the Nb-H sy stem at 313K. The evaluated elastic accommodation energies are compara ble to those obtained by continuum mathematical models and to the publ ished experimental values. The finite element model can successfully a ccount for relaxation of stresses due to the presence of free surfaces .