Constitutive equations for the room temperature deformation of commercial purity aluminum

A series of compression tests were conducted using a servo-hydraulic, computer driven testing machine to deduce the constitutive equations that describe the behavior of commercial purity aluminum deformed at room temperature over a wide range of strain rates. The experimental samples were tested with and without the use of either mineral oil or polytetrafluoroethylene (PTFE) tape. All the tests were performed at constant strain rates up to an equivalent strain close to 1. The load–displacement curves were converted into stress–strain curves using different coefficients of friction. The constitutive equations deduced assuming that a steady state is achieved at large strains are considered to be good enough for using them to predict the strength of the material on a wide range of strains and strain rates. The friction coefficient found to yield the best results was 0.05 for PTFE tape, 0.10 for mineral oil and 0.20 when no lubricant was used.