Ratcheting life improves with increasing mean stress. Mean stress dependent hardening, i.e. decreasing hysteresis loop area and plastic strain amplitude with increasing mean stress, thought to be responsible for the improvement in ratcheting life.
Pre-ratcheting significantly reduce subsequent LCF life. Permanent ratcheting strain accumulation can be the root cause of LCF life reduction.
Pre-ratcheting alter the hardening/softening behavior in succeeding LCF tests
Tensile properties, i.e. yield stress, ultimate tensile stress and uniform elongation alter in a systematic manner with LCF and ratcheting damage.
Average dimple size increases and dimple number in unit area decreases with LCF damage whereas, average dimple size decreases and dimple number in unit area increases with ratcheting damage. |