Effect of Machining on Fatigue life of Aerospace Grade Aluminum Alloy (Al 6082-T6)

Abstract

Aluminum alloys have widespread usage in aircraft and automotive industries because of its low density. Aluminum as well as other materials such as copper and magnesium do not show fatigue limit; i.e. these materials will fail after a certain number of loading cycles. Apart from the inherent nature of the material, the fatigue life of aluminum is also affected by the cutting conditions such as depth of cut, cutting speed and feed rate etc. Hence, it is useful to understand the effect of cutting conditions on the fatigue life of aluminum alloys. In this research work, the effect of machining on the fatigue life of aerospace grade aluminum alloy (Al 6082-T6) was considered. Machining parameters considered for this investigation were cutting speed, feed rate and depth of cut. The response variable under consideration was the fatigue life. The specimens of the Al 6082-T6 were prepared according to the standards of fatigue testing and fatigue testing machine. A four point rotating bending fatigue testing machine was used for the fatigue life estimation of Aluminum 6082-T6. The fatigue testing was carried out according to BS ISO 1143:2010. The range of the cutting conditions values were quoted from the manufacturer’s catalogue (Sandvik Coromant Catalogue 2011 and Corokey of the Sandvik Coromant Catalogue 2011). The cutting parameters were selected according to ISO 3685. The software Design expert 7.0 was used for the design of experiments and subsequent analysis of the response variable and their dependencies. A total of 81 experiments were performed with suitable repetition of three for each parameter settings. These specimens were used to estimate fatigue life of the alloy. For optimum machining parameters (cutting speed of 2000m/min, feed rate of 0.2mm/rev and depth of cut 1.5mm) recommended by the tool manufacturer, fatigue life at maximum value with one of the parameters at non-optimum value. List of solutions was also developed containing machining conditions to improve fatigue life. List was arranged according to the desirability of maximum fatigue life.