Effect of Friction and Back Pressure on the Formability of Superplastically Formed Aluminium Alloy Sheet


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This paper examines the effect of friction and back pressure on the formability of superplastically formed aluminium alloy AA7475 sheet at the temperature of 517 °C. Several experiments with lubrication and back pressure are performed using a simple box shape tool cavity. The coefficient of Coulomb friction between the formed sheet and tool has been determined indirectly using a finite element model to simulate superplastic forming of the box shape. Typical values determined for all lubricant conditions tested are in the range 0.1 < μ < 0.2. The void growth with strain was determined directly from measurements as a function of back pressure. The results show the application of back pressure at 1 MPa reduces the growth of voids from 7% to 0.3% void volume fraction at a logarithmic thickness strain of 0.65. This paper reports back pressure has a significantly greater role than friction in enhancing the formability of the alloy.



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Edited by:

J.R. Duflou, R. Clarke, M. Merklein, F. Micari, B. Shirvani and K. Kellens






P. Wood et al., "Effect of Friction and Back Pressure on the Formability of Superplastically Formed Aluminium Alloy Sheet", Key Engineering Materials, Vol. 473, pp. 532-539, 2011

Online since:

March 2011




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