Mechanical Hysteresis and the Initial Stages of Fatigue

Abstract

Experiments are described which show that positive or negative closure failure in the mechanical hysteresis loop can be achieved when the prestress is fully reversed. Small amounts of prestrain tend to produce positive closure failure, that is, a Bauschinger strain larger than the prestrain, while larger prestrains produce negative closure failures. The conditions created during prestrain which may lead to variations in the potential for reverse flow are examined, and the implications of the closure-failure variations for the initiation of fatigue damage are discussed.