Simulations of necking during plane strain tensile tests

Abstract

A hydrodynamic code is used to simulate plane strain tension experiments: extension of sheets and expansion of cylinders. The material is characterized by an elastic-plastic constitutive law. The stress state in the structure is first approximately uniform, but numerical fluctuations proper to the hydrodynamic code grow and give birth to a non homogeneous deformation state. The last step shows the concentration of plastic deformation in necks, prior to rupture. Simulations show very clearly that the wavelength of instabilities and the instant of their appearance depends on some physical values: traction speed, aspect ratio, parameters of the constitutive law. Simulations of plane strain expansion of rings are compared to experimental results of expansion of cylinders. Several fragments are created and their size is similar, which validates partly the simulations.