A New Method of Damage Cumulation for Fatigue in Non Proportional Case Differentiating Stress and Strain Controlled tests

摘要

A conservative linear damage cumulation rule for non-proportional cases is proposed. For that we define a uniaxial steady state cyclically equivalent to a non-proportional steady state through the dependence of the uniaxial cyclic stress strain curve on cyclic overloading. We show that overloading and non-proportionality of loading enhance the fatigue life for stress-controlled tests in contrast with strain-controlled tests. The proposed model yields conservative predictions of fatigue lives for non proportional strain controlled tests. Experimental validation is demonstrated for different steels in stress or strain controlled tests for uniaxial and non proportional loading. Moreover the previous analysis has been extended to variable amplitude loading in uniaxial case.