Experimental investigation of fatigue damage development using microhardness and chord modulus variation methods in stainless steel 316L

Damage mechanics is tool in mechanical engineerin, that is known as the complementarity for theory of plasticity and fracture mechanics. In this research, an experimental study of the fatigue damage growth process has been investigated for 316L stainless steel. For this purpose, using ASTM E466 fatigue special standard, testing samples with rectangular cross section, has been drawn and prepared. Uniaxial Low cycle fatige has been performed at similar stress amplitudes, similar frequencys and various loading cycles. After carrying out fatigue tests, in order to derivation damage development process, microhardness and Loading-Unloading tests –deriving relation of microhardness and chord modulus with strain- has been performd too. Experimental tests has been carried out under environmental conditions. Damage development process was achieved, Using results of fatigue, loading-unloading and microhardness tests. A method for estimating damage is purposed in this research. At the end, the results of the methods of the chord modulus, microhardness and purposed are compared with each other. The damage growth process of the purposed method has a good fit with the method of chord modulus. The obtained critical damage was 0.38 by using the chord modulus method and 0.41, by microhardness.