A Rapid Experimental Method for the Fatigue Crack Growth Threshold
At present, the load shedding method is widely used for the determination of the fatigue crack growth threshold. However, when this method is utilized to measure the fatigue thresholds for a given material, two restrictions must be imposed on each shedding load step in order to eliminate overloading effects: (1) the reduction of maximum stress intensity factor Kmaxmust be lower than 10% previous Kmax, (2) the minimum increment of the crack growth must be several times greater than the plastic zone size due to previous Kmax. Since the crack grows at a very low rate when the stress intensity factor range ΔK approaches the threshold ΔKth, much testing time will be consumed to satisfy the requirements of the above mentioned two restrictive conditions. Consequently, the measurement of the thresholds remains a difficult work which requires long testing time, especially for materials which are sensitive to overloading effects. In this paper, a new rapid experimental method, i.e., a regression method with three parameters, is presented.
KeywordsStress Intensity Factor Regression Method Crack Growth Rate Fatigue Crack Growth Testing Time
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