A Novel Multiaxial Strain-Based Criterion Considering Additional Cyclic Hardening

Area of Science:

• Materials Science
• Mechanical Engineering
• Solid Mechanics

Background:

• Non-proportional loading significantly influences material fatigue.
• Dislocation interactions under non-proportional loading cause cyclic hardening.
• Existing fatigue criteria may not fully capture these effects.

Purpose of the Study:

• To theoretically evaluate the impact of non-proportionality on fatigue.
• To propose a novel multiaxial strain-based criterion, the refined equivalent deformation (RED) criterion.
• To incorporate strain amplitude and additional cyclic hardening into fatigue life estimation.

Main Methods:

• Theoretical evaluation of non-proportional loading effects.
• Development of the refined equivalent deformation (RED) criterion.
• Experimental validation using multiaxial low cycle fatigue (LCF) tests.

Main Results:

• The RED criterion effectively considers strain amplitude and additional cyclic hardening.
• Experimental tests on Ti-6Al-4V specimens validate the criterion's accuracy.
• The study quantifies the influence of non-proportionality on fatigue.

Conclusions:

• The refined equivalent deformation (RED) criterion offers improved fatigue life prediction under multiaxial non-proportional loading.
• The criterion accurately captures the additional cyclic hardening caused by non-proportionality.
• This work provides a valuable tool for engineering applications involving complex loading conditions.