Theoretical and Experimental Analysis of the Energy Dissipation at Fatigue Crack Tip Under Cyclic Loading with Constant Stress Intensity Factor

Abstract

The investigation of the fatigue crack propagation was carried out on flat samples with stress concentrator made from stainless steel AISE 304. The earlier developed contact heat flux sensor based on the Seebeck effect was used to monitor the heat flux from the crack. It gives us an opportunity to correlate the heat dissipation and crack propagation rate under constant stress amplitude. The experiments with the constant stress intensity factor have shown a decrease of the energy dissipation under constant crack rate. To explain this result the presented theoretical analysis of the stress field at the fatigue crack tip was carried out. It allows us to describe the energy flux from the crack tip as sum of two functions describing the energy dissipation in monotonic and reversible plastic zones separately. It has been shown that dissipation in reversible plastic zone is a function of the applied stress amplitude only. This fact leads to the decrease of the heat dissipation under constant stress intensity factor due to the decrease of the applied stress amplitude.