Study on Torsional Fatigue Strengths of Rectangular and Circular Cross Sections of Steel

Abstract

Comparison was made on the static and fatigue strengths of one kind circular and three kinds of rectangular cross-sectional specimens under torsion. The rectangular specimens were made to have the same T/τ (torsional moment/maximum stress) as that for the circular specimen. The main results obtained are ; (1) the circular specimen has the weakest strengths in static and fatigue tests, (2) the sequence of the fatigue strengths is entirely the same as that of the static strength, and (3) for three rectangular specimens the fatigue cracks initiate at the same number of cycles, but the rate of crack propagation is different depending on the specimens.