Crack propagation behavior and mechanism of coarse-grained copper in cyclic torsion with axial static tension

In order to essentially study the influence of axial static tension on torsional fatigue crack propagation, cyclic torsion with and without axial static tension are carried out for coarse-grained copper. Results show that static tension affects the crack propagation behavior of coarse-grained copper in two ways: it can not only affect the growth direction of Stage I crack growth, but can also lead to the transition of surface crack from Stage I to Stage II. The micro-mechanisms produced by mean stress on crack propagation, particularly the transition mechanism from Stage I to Stage II crack growth, are analyzed.