A Novel Multiaxial Strain-Based Criterion Considering Additional Cyclic Hardening

Abstract

The present paper is dedicated to the theoretical evaluation of a loading feature, that may have a significant influence on fatigue phenomenon: non-proportionality. As a matter of fact, considerable interactions between dislocations, leading to the formation of dislocation cells, cause additional cyclic hardening of material. Such a phenomenon is experimentally observed for materials sensitive to non-proportionality. In such a context, the present paper is aimed to propose a novel multiaxial strain-based criterion, the refined equivalent deformation (RED) criterion, which allows to take into account, in fatigue life estimation, both strain amplitude and additional cyclic hardening. The accuracy of the novel criterion is evaluated by considering experimental tests, performed on Ti-6Al-4V specimens, subjected to multiaxial LCF loading.

The RED criterion for fatigue life assessment of metals under non-proportional loading

“…The displacement  of point P may be decomposed in a component also summarised in Ref. [22]. Moreover, it is worth noticing that Eq.…”

Fatigue life prediction of notched components under size effect based on strain energy density gradient

“…Zhong et al 22 summarized some important non‐proportional effect, gave a new non‐proportional description, and finally proposed a new damage parameter of multiaxial fatigue life. Vantadori 23 put forward a refined equivalent deformation criterion, which took into account additional cyclic hardening and strain amplitude. Furthermore, Ti‐6Al‐4V specimens were used for test, which verified the accuracy of the criterion.…”