Effect of Plastic Prestrain on High Cycle Fatigue of Ti–6Al–4V

Abstract The effect of initial plastic strain on the high cycle fatigue (HCF) lives of smooth cylindrical Ti–6Al–4V specimens is investigated. Specimens were monotonically, quasi-statically loaded under strain control in tension to produce plastic strains from 1% to 5% and under load control in compression to produce 9.5% plastic strain. A step-loading technique was then employed to establish the 106 or 107 cycle fatigue limit stress under load control conditions for stress ratios of R=0.1, 0.5 and 0.8 at frequencies of either f=50 or 400 Hz. Results are compared with baseline fatigue limit stresses for Ti–6Al–4V without prior plastic strain. Initial plastic prestrain in both tension and compression resulted in a small reduction in the fatigue limit at R=0.1, while a lesser reduction was exhibited at higher stress ratios in terms of maximum stress.

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