THE DEGRADATION OF THE ELASTIC PROPERTIES OF METALLIC MATERIALS EVALUATED BASED ON AN EXTENDED GTN MODEL

Although an indentation does not induce apparent cracking in ductile materials, the degradation of the elastic stiffness of ductile metals does occur in micro-/macro-indentation tests. After comparing the degradation predicted based on extended damaged-plasticity models with that measured by experimental testing, it is found that the softening due to the distortion of the existing voids is not enough to cause a notable degradation of elasticity. It is suggested that an independent damage-nucleation mechanism due to the shear deformation may be in operation. Although attractive in practical applications for its nondestructive nature, the damage-based indentation technique for estimating the fracture properties of ductile materials needs further investigations.