Material Behavior around the FSW/FSP Tool Described by Molecular Dynamics

Abstract

Friction stir welding and processing (FSW/FSP) involves severe plastic deformation of metals or polymers at high temperature around a rotating tool. The material’s flow is usually modelled by FEM using a complex combination of thermomechanical and friction models. However, the description of the behavior of the first atomic layers in contact with the tool cannot be undertaken by continuum mechanics modelling such as FEM. Among the available simulation techniques, molecular dynamics (MD) where friction and heat are generated by material layers’ relative movement, allows the simulation of the behavior of the first atomic layers of the work piece in contact with the tool. In this work, in aluminum, the effect of temperature and advancing and rotating speeds on FSW/FSP material’s flow and crystallography in the vicinity of the tool are discussed. The data analyzed demonstrate that a normalization of the weld-pitch parameter by the pin radius allows obtaining reliable heat input, momentum, and temperatures typical of this critical region in the FSW/FSP processes by MD. The results show that MD provide reliable data as an input for the FEM in a multiscale FSW/FSP modelling.