Selecting Materials to Resist Low Cycle Fatigue

Abstract

The selection of materials in the design of components to resist low cycle fatigue is considered in terms of reliable methods of material comparison which can be used in lieu of extensive testing programs. Specifically, a procedure is proposed for ranking candidate materials on the basis of resistance to strength loss, repeated straining, repeated stressing, and notch fatigue in the low cycle fatigue region. Easily performed tests requiring only two specimens of each material are utilized. Monotonic and cyclic stress-strain curves are determined from a standard tensile test and an incremental step test, respectively. A material’s cyclic stability is immediately apparent from comparison of the two curves. Values from these curves are then used in conjunction with empirical relations to predict fatigue resistance in terms of plastic strain amplitude, stress amplitude and a fatigue notch parameter. Examples, using practical engineering materials, are presented to illustrate the reliability of the procedure.