Abstract
Crack propagation was quantitatively evaluated to investigate the effect of electropulsing treatment (EPT) on fatigue crack growth of copper specimens. Varying fatigue cycles were obtained under six different load levels. The crack lengths were measured under two load levels to examine the effect of cyclic stress. The microhardness was measured around the vicinity of the crack tip. Furthermore, the fracture surface was observed by scanning electron microscopy. Results show that EPT with electric current density of 150 A/mm2 enhances the high-cycle fatigue life, and the effect tends to increase with the decrease in cyclic stress. Vickers microhardness (HV) near the crack tip decreases to normal levels after treatment, and the approaching cracks on two sides can be observed. Local annealing and recrystallization occur around the fatigue crack tip. Accordingly, crack propagation can be delayed, and fatigue life can be prolonged by EPT.
Highlights
Fatigue is a principal mode of damage which results in metallic equipment failure
Nf is defined asNthe cyclic number when awas complete of the gauge f of the cases, Nf isand defined as theindicates cyclic number whenlevel, a complete separation of the gauge lengthamplitude occurred, occurred, σN, which the loading represents the nominal cyclic stress andthe σN,bottom which indicates the loading represents the nominal cyclic theaverage bottom at of the notch
It can be seen that fatigue life decreases that fatigue life decreases with the increase in loading stress amplitude, and the σN–Nf curves of the with the increase in loading stress the σN –Nf curves of the notched copper specimens notched copper specimens show amplitude, a uniform and Manson–Coffin relationship from lowto high-cycle show a uniform Manson–Coffin relationship from low- to high-cycle regions
Summary
Fatigue is a principal mode of damage which results in metallic equipment failure. Fine electrical conductivity provides the base of electron wind force by electric treatment in a current-carrying metallic material. Pulsed electric current is effective in improving the mechanical properties of carbon steel and aluminum alloys [1,2]. Zhou et al [3] indicated that the mechanical properties of cold-worked brass could be improved because of recrystallization caused by electropulsing treatment (EPT). The electropulsing time is very short and smaller grains can be obtained; the mechanical properties of material can be improved. Conrad and Cao et al [4,5] demonstrated that the fatigue life of copper increased by the treatment of electric current pulse during the rotating bending test
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