Determination of the flow stress-strain curves of aluminum alloy and tantalum using the compressiveload-displacement curves of a hat-type specimen

The load-displacement curves of an aluminum alloy and tantalum were determined using a hat-type specimen in the compression test. Based on the results of finite element analysis, the employed geometry of the hat-type specimen was found to yield a load-displacement curve that is nearly independent of the friction between the specimen and the platen. The flow stress-strain curves of the alloy and tantalum were modeled using the Ludwik and Voce constitutive laws, respectively; furthermore, simulation of the compression event of the hat-type specimen was performed by assuming appropriate constitutive parameters. The constitutive parameters were varied via an optimization function built in MATLAB until the simulated load-displacement curves reasonably fit the experimental curve. The optimized constitutive parameters obtained in this way were then used to construct friction-free flow stress-strain curves of the two materials.