An efficient strategy for 3D numerical simulation of friction stir welding process of pure copper plates

M A Constantin,Y Demmouche,C Bădulescu,M D Iordache,E L Nitu,M Diakhaté,M Dhondt

doi:10.1088/1757-899x/916/1/012021

Abstract

Copper and its alloys have a wide spectrum of engineering applications such as heat exchangers, hot water tanks or nuclear pressure vessels. Most of these structures are obtained by welding. Unfortunately, the use of conventional arc welding process is affected by several factors such as the thermal conductivity of the alloy being welded, the shielding gas, the joint design, the welding position, and the surface condition and its cleanliness. Friction stir welding process could be an interesting alternative as it can be performed without melting the material, it involves a non-consumable tool, and provides good mechanical properties. To understand in depth both the physical and the thermal mechanisms involved in this process, numerical modelling is essential. The aim of this paper is to propose an efficient simulation strategy based on the coupled Eulerian Lagrangian finite element method. The mass scaling procedure, which is used to decrease the computation time will be presented, as well as its effect on the temperature field distribution and on the down force. This model will then be used for a parametric study in order to improve the friction welding process’s parameters.

Highlights

Conventional fusion welding processes cause a series of defects in the materials to be joined, due to the excessive rise in temperature
Friction stir welding (FSW) is a welding technique proposed by The Welding Institute in 1991 [1], which makes it possible to assemble alloys difficult to weld using conventional welding techniques
The finite element method was widely used by scientists and engineers to deal with a large number of problems associated with friction stir welding [6]

Summary

Introduction

Conventional fusion welding processes cause a series of defects in the materials to be joined, due to the excessive rise in temperature. The rotation of the tool and the contact of its shoulder with the surface of the welding parts leads to the frictional generation of an important amount of heat and, to increase the temperature in the joint area. The finite element method was widely used by scientists and engineers to deal with a large number of problems associated with friction stir welding [6] This method offers two possible approaches: (i) the Eulerian approach: mainly adapted to the simulation of flows but they manage with difficulty the conservation of mass at interfaces and extremely long computation times and (ii) the Lagrangian approach which do not suffer from this problem of mass conservation but they must be intensively remeshed in order to adapt it to the flows, which generates numerical errors and is difficult to overcome in order to complete the simulations of the FSW process. Integration scheme The direct integration scheme adopted for the resolution is explicit because the problem treated here is dominated by numerous nonlinearities such as nonlinear material behaviour, dynamic phenomena, introduction of the thermal effects or contact

Strategies for minimizing the computation time

Findings

Conclusions