Empirical determination of lemaitre's ductile damage parameters for thin sheet metals by variations of the elasticity modulus

Abstract

Damage of materials is the progressive physical process by which they break. The mechanics of damage is the study, through mechanical variables, of the mechanisms involved in this deterioration when the materials are subjected to loading. Common methods to measure damage parameter in ductile materials are variations of the elasticity modulus and the micro-hardness. In this paper, first, the possibility of variation of the elasticity modulus to determine the damage parameter for thin sheets is studied. To achieve this goal, Lemaitre's damage parameter for St 14 steel sheet is identified by using the variations of the elasticity modulus. Then, the calculated parameter from experimental results is applied in a fully coupled elastic-plastic-damage subroutine which has been developed into an Explicit code, to predict the damage behaviour of St14 thin sheet. The numerical results are compared with the empirical observations, to validate the identified damage parameter. Comparison of the numerical and experimental results shows proper and satisfactory adaptation. Hence, it is concluded that the measuring method of variations of elasticity modulus is reliable as a method to measure damage parameter as well as micro-hardness method for thin sheet metals. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.