Damage Evolution and Damage Surface of Elastic-Plastic-Damage Materials under Multiaxial Loading

Damage evolution and fundamental aspects of damage surface of a spheroidized graphite cast iron are observed. This paper is intended to discuss the applicability of the irreversible thermodynamics theory to the modeling of elastic-plastic-damage materials. By performing damage tests on the tubular specimens of the material under proportional and nonproportional loading, onset and development of material damage are first detected by measuring Acoustic Emission (AE) counts. The change in Young's modulus, Poisson's ratio and shear modulus is also observed in the tests to correlate them with the damage development in the material. The existence and the development of the damage surface, together with the condition of loading, unloading and neutral loading, are elucidated to facilitate the identification of the fundamental aspects of thermodynamics theory of the elastic-plastic-damage materials. The effects of the hydrostatic stress on the deformation and damage equations are also discussed.