A fatigue life evaluation method for notched geometries considered the stress gradient concept

Abstract

The stress concentration effect reduces fatigue resistance of notched geometries. The stress gradient strongly related to stress concentration plays a significant role in material strength assessment. This article attempts to propose a new fatigue life estimation method, named volume stress gradient method (VSGM) by introducing the stress gradient into the volume determined by the critical distance theory (TCD). The relative stress gradient for the critical volume is defined as the derivative of normalized average stress to the characteristic length of the volume and is integrated into a weight function to describe its effect on fatigue life. The characteristic length of VSGM is proved to be variable with fatigue life, stress ratio, and geometry of notch. Uniaxial fatigue experimental data at room temperature for the material low-carbon steel EN3B (R\u2009=\u2009− 1, 0.1) and material aluminum alloy 2024-T3 (R\u2009=\u20090.5) is used to verify the proposed model and the results showed VSGM seems to be capable to estimate the fatigue life of the notched specimen after compared with the tests.