Flow stress and barreling behavior of aluminum alloy during upset forging at elevated temperature

Abstract

Upset forging test at elevated temperature of aluminum alloy were experimentally carried out at specified temperatures ranging from 30⁰C (room temperature) to 300⁰C and at different true strain levels under a constant strain rate of 1 X 10-3/s using powdered graphite mixed with machine oil as lubricant throughout the tests. Calculations were made to radius of curvature of barrel with the assumption that the curvature of the barrel followed the form of a circular arc. The radius of curvature of the barreled aluminum cylinders measured physically was found to confirm closely to the values calculated using the experimental data even at higher temperature. Generalized characteristic equations for each temperature have been developed by regression analysis. It was found that both the strength coefficient and strain hardening exponent decreases with increase in temperature. A common characteristic equation considering both strain and temperature was also found out. Further, different stresses like hoop stress, hydrostatic stress and effective stress have been found out for different temperature using the dimensions of the deformed specimens.