Experimental study on uniaxial time-dependent ratchetting-fatigue interaction of T6-6061AL alloy

The time-dependent ratchetting-fatigue interaction of T6-6061Al alloy was observed in the uniaxial stress-controlled cyclic tests with non-zero mean stress and at room temperature. The effects of stress level, stress rate, and peak/valley stress hold on the ratchetting and low-cycle fatigue life of the alloy were discussed. It is shown that the ratchetting is apparently time-dependent and its evolution is quicker when the applied stress amplitude is higher, stress rate is lower, and hold time is longer, even if the final ratchetting strain is slightly different from each other in the prescribed cases; and then results shorter low-cycle fatigue life. The creep strain produced during the peak/valley stress hold and at lower stress rate accelerates the evolution of ratchetting and shortens the low-cycle fatigue life of the alloy. Some preliminary observations about the effect of creep on the ratchetting-fatigue interaction of the alloy are obtained, which are very significant for the future more detailed research.