Poisson’s Ratio of Selected Metallic Materials in the Elastic–Plastic Region

Poisson’s ratio is one of the fundamental characteristics in the material models that are used. In engineering practice, its values are assumed to be constant in the elastic and in the plastic region. In this paper, the conventionally used values of this number for steel materials and aluminum alloys are confronted with experimental results. By using non-contact strain measurements with the DIC (digital image correlation) method, the evolution of the Poisson ratio value in the regions of transition from the elastic to the plastic region as well as in the regions of large plastic deformations was documented. The obtained experimental results are graphically compared using the proposed strain scaling. The gradient of the Poisson ratio changes in the vicinity of the yield stress is significant, indicating the need for a refinement of the material models in this region. Deviations from the conventionally used value of this number were found in the large plastic deformation region. In conclusion, a possible approach for improving the accuracy of simulations in FEM softwares was formulated.