Statistical fatigue properties in the large strain region of a stainless steel sheet for use as an abrasion strip on helicopter rotor blades

The objective of this study was to evaluate the statistical fatigue properties of a thin sheet of a stainless steel for use as an abrasion strip on helicopter rotor blades made of glass fiber/epoxy composite materials. The sheet was an AISI 301 1/4-hard stainless steel. Tensile fatigue tests were conducted up to 107 cycles on unnotched specimens under constant amplitude loading in the large-strain regions for stress ratios (=minimum stress/maximum stress) R=0 and 0.3. The test results provided S–N relationships for R=0 and 0.3, the standard deviation of fatigue life and fatigue strength in the inclined part and the mean and standard deviation of fatigue strength in the horizontal part of the S–N curve for R=0. Strain measurements during fatigue tests clarified the change of true stress in specimens and estimated the fatigue crack propagation period. SEM revealed the details of the fatigue-fracture surfaces formed by the repetition of large strains. The applicability of this material as an abrasion strip is discussed on the basis of the test results.