Study of Experimental Hysteresis Loops Under Non-Proportional Loading

Fatigue life prediction is a challenge for engineers when it comes under nonproportional loading. In many applications, engineering components are subjected to complicated states of stress and strain. Studying of hysteresis behavior under non proportional loading is important for reliable engineering designing for studying the cyclic deformation that is essential to find the plastic strain ranges which is used for fatigue life prediction. This paper discusses the behavior of the hysteresis loops created experimentally under various non-proportional loadings. EN8 carbon steel notched specimen was used for the experimental analysis. The tests were carried out using a multi axial test machine However, the results have shown significant difference in hysteresis behavior changing the path of non-proportional loading. Comparing the experimental results of direct and shear strains of non-proportional loading paths, some loading cycles are more damaging in terms of fatigue life.