Investigation the Creep-Fatigue Behavior and A.C. Electrical Conductivity of AA 6061 Under Ultrasonic Peening
Ultrasonic peening is an innovative surface improvement process used to increase the resistance of aircraft metals and enhance high cycle fatigue life. The process creates residual compressive stresses deep into part surfaces. These compressive surface stresses inhibit the initiation and propagation of fatigue cracks. Aluminum alloys are relatively new materials used in aerospace, marine, automobile, and bridges due to low weight, which has significant advantages compared to the other materials. A major concern in the design of Aluminum alloys subjected to variable loads is fatigue strength and life. In this paper mechanical properties, fatigue strength, fatigue life and A.C.. electrical conductivity were studied for AA6061-T6 to assess the effects of ultrasonic peening (UP) on mechanical properties, fatigue at room temperature (RT), creep-fatigue (CF) at 250 ͦC and A.C.. electrical conductivity. Test results showed that after UP, the mechanical properties; ultimate tensile strength (UTS) and yield stress (Ys)
were noticeably improved. The improvements in UTS and Ys were enhanced by
5.7% and 1.5% respectively while the ductility was reduced from 16.5% to 15.7%.
Fatigue strength was enhanced by 8.37% compared to strength at RT. The results
of UT before creep-fatigue CF showed increasing in fatigue strength 147 MPa at
CF 250 ̊C and improved to153 MPa after applying UP, indicating 4%
improvement in strength. The fatigue life was improved after UP for both RT and
CF. It was found that the A.C. electrical conductivity increase as the frequency
increase for all the cases above.
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