A NEW MULTIAXIAL FATIGUE TESTING METHOD FOR VARIABLE-AMPLITUDE LOADING AND STRESS RATIO

摘要

A new vibration-based multiaxial fatigue testing methodology for assessing high cycle turbine engine material fatigue strength at various stress ratios is presented. The idea is to accumulate fatigue energy on a base-excited plate specimen at high frequency resonant modes and to complete a fatigue test in a much more efficient way at very low cost. The methodology consists of: (1) a topological design procedure, incorporating a finite element model, to characterize the shape of the specimens for ensuring the required stress state/pattern, (2) a vibration feedback empirical procedure for achieving the high cycle fatigue experiments with variable-amplitude loading, and finally (3) a yielding procedure for achieving various uniaxial stress ratios. The performance of the methodology is demonstrated by the experimental results from mild steel, 6061-T6 aluminum, and Ti-6Al-4V plate specimens subjected to fully reversed bending for both uniaxial and biaxial stress states. Results are compared with those produced using traditional fatigue test machines.