A novel method for development of constitutive models under simultaneous extreme strains and strain rates

Abstract

This work presents a new experimental configuration for studying material behavior under extreme thermomechanical conditions. Deformation strains up to 10, strain rates up to 10$^6$ 1/s, and temperatures close to melting are achievable. The new configuration makes a rigid and hard tool strike a specimen that protrudes from the surface of a substrate. The fin-like specimen is deformed in simple shear by the fast-moving tool. The particular geometry of the specimen creates a shear band that travels nearly one-dimensionally across the fin, from the point of impact. The one-dimensional shear band is characterized by uniform stress, strain, strain rate, and temperature. The configuration is an attractive platform for the accurate development of constitutive models, under simultaneous extreme strain and strain rate. The deformation force can be measured with simple devices. This paper presents a proof of concept for the platform. The deformation is modeled using high-resolution finite element analysis. Deformation force, stress, strain, strain rate, and temperature are obtained from this numerical experiment. Simple analytical models are fitted to the data to infer the constitutive model of the material. The inferred constitutive model is compared to the one given as input to the finite element experiment. The comparisons show minimal deviations, which indicate that real experiments should produce highly accurate flow stress measurements, if the shear band propagates one-dimensionally. The numerical experiments were performed using the Johnson-Cook model for AISI 4340. It is important to note that the numerical experiments resulted in adiabatic shear bands without material damage criteria.