On the selection of constitutive laws used in modeling friction stir welding

•Both path dependent and independent constitutive laws used in modeling friction stir welding were investigated.•None of the path-independent laws evaluated in this paper have been demonstrated valid over the entire range of strain, strain rate, and temperature in friction stir welding.•The Sellars and Tegart/Sheppard and Wright and saturated Hart laws are strain insensitive.•Strains in the nugget and possibly a portion of the TMAZ are higher than those over which the Johnson–Cook constants used by Schmidt and Hattel [41] were determined.•While holding all other parameters constant, changing the constitutive law in a FSW model can result in up to a 21% difference in peak temperature.

Discrepancies in friction stir welding model predictions for temperature, strain, and strain rate may be due to material, process parameters, boundary conditions, heat transfer properties, or constitutive laws. The focus of this work is to investigate the effect of the constitutive law on friction stir welding model predictions. This paper provides a description of constitutive laws with their uses and limitations to facilitate the selection of an appropriate constitutive law for a given modeling objective.None of the path-independent constitutive laws evaluated in this paper has been validated over the full range of strain, strain rate, and temperature in friction stir welding. Holding all parameters other than constitutive law constant in a friction stir weld model for AA 5083 resulted in temperature differences of up to 21%. Varying locations for maximum temperature difference indicate that the constitutive laws resulted in different temperature profiles. Peak strains and strain rates predicted vary by up to 130% and 166%, respectively. Predicted flow stress profiles are also affected by the choice of constitutive law.