Effect of Axial Compression on Low-Cycle Fatigue of Metals in Torsion

Thin-walled tubular specimens of aluminum alloy 2024-T351, stainless steel 347, and beryllium copper 25 under static axial compressive stresses were tested in low-cycle fatigue in torsion. The data obtained indicates that compressive stress increases the low-cycle fatigue life of all these materials. This effect is similar to the effect of hydrostatic pressure which improves the fatigue behavior of metals under torsion as reported by previous investigators. Cyclic torsion tests with no axial stress were also conducted on these metals. The results of these cyclic torsion tests without axial stress can be well approximated by the empirical low-cycle fatigue relation proposed by Coffin [1]² and Manson [2].