Poisson's Ratios and Volume Changes for Plastically Orthotropic Material

Measurements of Poisson's ratios have been made in three orthogonal directions on aluminum alloy blocks in compression and on stainless-steel sheet in both tension and compression. These measurements, as well as those obtained by density determinations, show that there is no permanent plastic change in volume within the accuracy of observation. A method is suggested whereby a correlation may be effected between the measured individual values of the Poisson's ratios and the stress-strain curves for the material. Allowance must be made for the difference in the stress-strain in tension and compression; this difference, wherever it appears, is accompanied by significant changes in the Poisson's ratios.