Investigation on the yield behaviour and macroscopic phenomenological constitutive law of PA66

Abstract The compression, tension, shear and combined shear-compression tests with different loading rates were conducted to investigate the mechanical behaviour of PA66 specimens. The initial yield and post-yield behaviour were analysed to determine the parameters in theoretical models. Results showed that the yield criterion based on three stress invariants gives the best description of the initial yield behaviour of PA66. The post-compression/tensile behaviour of PA66 was described by a hyperbolic function. The subsequent yield function was proposed based on the combination of initial yield surface and mixed work hardening model. The ratio of compression and tensile strength was utilized to appropriately characterize the kinematic hardening. Additionally, the effects of loading rate on PA66 yield stress and post-yield behaviour can be described by Eyring theory. On the basis of the general observations and classical elastoplastic theory, a macroscopic phenomenological constitutive was constructed to describe the mechanical behaviour of PA66.