Impact Torsional Fatigue Strength of Structural Carbon Steels

Impact torsional fatigue tests on four sorts of structural carbon steels were carried out in low cycle life region under both the pulsating and the completely reversed impact torsion. An analysis based on the extended concept of endurance fatigue limit diagram was performed for the impact torsional fatigue and the fatigue strengths were studied on the relationship with the static tensile properties. Also, the experimental data were statistically analyzed. The relationship between the pulsating and the completely reversed torsional fatigue was well expressed by an equation obtained on the basis of the extended concept of endurance fatigue limit diagram. Impact torsional fatigue strength was found to have a logarithmic normal distribution. Under the impact torsional loading with an arbitrary stress ratio, the impact fatigue strength can be estimated failure probabilistically from the statistics of static tensile properties (σB, φ).