THERMOMECHANICAL FATIGUE BEHAVIOR OF BURNISHED 7075–T6 ALUMINUM ALLOY | ||||
| The International Conference on Applied Mechanics and Mechanical Engineering | ||||
| Article 46, Volume 15, 15th International Conference on Applied Mechanics and Mechanical Engineering., May 2012, Page 1-11 PDF (4.36 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/amme.2012.36958 | ||||
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| Author | ||||
| A. A. Abo El-Nasr | ||||
| Associate Professor, Dpt. of Mech. Engineering, College of Engineering, Qassim, University, Buraidah 51452, Saudi Arabia, On leave from Dpt. of Production Engineering and Mechanical Design, Faculty of Engineering, Menoufiya University, EGYPT. | ||||
| Abstract | ||||
| ABSTRACT This paper presents the results of series of isothermal and thermomechanical fatigue (TMF) tests of unburnished and burnished 7075-T6 Al specimens. A designed roller burnishing tool was employed to improve the strength of the surface layer of the fatigue specimens. The fatigue stresses were developed in the specimens by combining constant amplitude rotating bending stresses along with constant temperature variation. Isothermal (ITF) and TMF tests were conducted on a rotary bending fatigue testing machine. In ITF tests, two different constant temperatures were used namely: 523 and 623 K. For TMF tests, a constant temperature variation between 523 and 623 K was applied. All these tests were conducted at a constant operating speed of 1200 rpm. The present results revealed that roller burnishing processes have played a significant role in increasing the fatigue lifetimes for both ITF and TMF specimens. The enhanced fatigue strength of the burnished specimens was attributed to the overall increase in the surface layer strength which may delay fatigue crack growth from the surface. Two distinct fatigue fracture regions were observed: region I and region II. In region I, the fracture surface is associated with the formation of fatigue striations. In region II, the fracture surface is covered with surface dimples. This indicates that local strain softening mechanism has dominated the final stage of fatigue failure. Extensive effort has been paid at investigating the fracture surface of ITF and TMF specimens. | ||||
| Keywords | ||||
| Thermomechanical fatigue; 7075-T6 Al; Fatigue lifetime; Burnishing; fracture | ||||
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