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.