Determination of Mode of Damage During Creep-Fatigue Interaction

A technique has been developed using the reversing dc electrical potential method to determine the mode of damage taking place during creep-fatigue interaction. It is observed that the hysteresis loop created by plotting the stress verses electrical potential gives a clear indication whether the damage in process is creep dominated or fatigue-dominated. During the fatigue-dominated damage process the hysteresis loop of stress verses electrical potential changes the shape whereas during the creep-dominated damage process the hysteresis loop of stress verses electrical potential does not change the shape but moves in the direction of higher electrical potential values. These changes are observed well before any indication seen on the conventional hysteresis loop of stress verses strain. This identification of the damage mode is observed well before failure occurs. The conclusion has been confirmed through fractographs. Hence it can be said that this technique eliminates the need for fractographs when determining the mode of damage during creep-fatigue interaction.