Abstract
Applicability and fundamental aspects of the irreversible thermodynamics theory of elastic-plastic-damaging materials are discussed by performing a series of multiaxial damage tests. The changes of Young's modulus, Poisson's ratio and shear modulus under tension and torsion are first observed for thin tubular specimens of spheroidized graphite cast iron. The Acoustic Emission (AE) count rate is also measured in order to detect the onset and the development of material damage. The changes in the elastic properties are related to the AE count rate. Then, by performing damage tests under proportional and nonproportional loading, the initial and subsequent damage surfaces are identified by use of AE count rate. The conditions of loading, unloading and neutral loading for the damage surface are established by the experiments. The influence of the hydrostatic stress on the initial damage surface is found larger than that of subsequent surfaces.
