Measurement of effective stress intensity factor range of mode II fatigue crack growth using hysteresis loop

A method was proposed for measuring the effective stress intensity factor ranges of Mode II fatigue crack growth by using the hysteresis loop for a specimen's surface strain. Many cases of rolling contact fatigue failure, such as those that occur in railway rails, bearings and gears are due to repeated high shear loads. In order to prevent such fatigue failures, the resistance of a material to repeated high shear loads must be determined. The fatigue crack growth characteristics are dependent on the Mode II stress intensity factor range. However, conventionally measured Mode II fatigue crack growth characteristics vary according to the measurement methods. Therefore, the authors improved the experimental measurement method proposed by Murakami, and proposed a way to measure the Mode II effective stress intensity factor range. Improvements to the jigs and specimen were made based on the ideal mechanical model of the experimental method. Furthermore, to measure the Mode II fatigue crack growth behavior, strain gauges were applied to the specimen and the hysteresis loop of the strain was measured with high accuracy by using a newly developed subtraction circuit.