The Evaluation of Coefficient of Friction for Representative and Predictive Finite Element Modelling of the Inertia Friction Welding

Abstract

Inertia friction welding is the process in which stored kinetic energy in a flywheel is converted to heat by relative sliding movement between surfaces of axi-symmetric components to achieve a weld in the solid-state. The work in this paper relates to the production of dual-alloy shafts for aeroengines. Frictional characteristics determine the conditions at the weld interface and these are controlled by rotational velocity and applied axial pressure. So-called representative and predictive methods have been developed to evaluate friction conditions during the process and these are discussed in this paper. Weld data for the dissimilar weld between a high strength steel and a nickel-based super-alloy were provided by Rolls-Royce and MTU Aero Engines. The finite element software package DEFORM-2D is used to develop coupled thermo-mechanical axi-symmetric models. In previous work, methods employed to evaluate the efficiency of mechanical energy utilised during a weld, a parameter of great importance for numerical analysis, are not clear. Previous predictive approaches have employed test/weld data in one way or another to obtain the interface friction coefficient. This paper proposes a formula that incorporates the value of the mechanical energy efficiency of the welding machine into the calculation of coefficient of friction for representative modelling. It also introduces a predictive approach based on sub-layer flow theory to predict frictional behaviour during the welding process that is independent of test/weld data.

Optimization of heat transfer in the finite element process modelling of inertia friction welding of SCMV and AerMet 100

“…The axial force is maintained after the flywheel comes to rest, allowing the metals to form a metallurgical bond [1]. Heat generation during the IFW process is dominated to a large extend by plastic deformation and frictional work which has been discussed previously by Mohammed et al [2]. On the other hand, heat transfer (HT) from workpieces involves conduction, convection, radiation and HT across the workpiece-die contact interface.…”

“…On the other hand, heat transfer (HT) from workpieces involves conduction, convection, radiation and HT across the workpiece-die contact interface. HT by conduction within workpieces was considered in all previous finite element (FE) models developed for modelling the IFW process [2][3][4][5][6][7][8][9] where it is treated as 2D conduction problem in a radial system (eqn (1)). However the few that considered the remaining HT modes expressed contradicting opinions regarding their importance while there was no mention of values and methods implemented to account for it.…”

Finite Element Modelling and Optimization of Rotary Friction Welding Parameters of High-Density Polyethylene Pipes (HDPE). (c2022)

“…The authors concluded that peak temperature and strain rate are proportional to the applied pressure whereas the width of the heat affected zone (HAZ) is inversely proportional to the applied pressure. Mohammed et al (2009) built a coupled thermo-mechanical axisymmetric model of IFW of a dissimilar high strength steel and a nickel-based superalloy on DEFORM software package. The paper aims at evaluating the friction conditions which control the weld formation and are determined by weld parameters, mainly rotational speed and axial pressure.…”

“…Where 𝜀̅ is the effective strain rate, 𝜀v is the volumetric strain rate, 𝐹 is surface traction, u is the velocity, and 𝐾 ̅ is a penalty constant that avoids volume alteration by forcing a material incompressibility factor on the velocity field (Mohammed et al, 2009).…”

“…According to Maalekian et al (2008), describing the friction coefficient analytically is the most difficult task. This is due to the fast shift in interface conditions and material properties during the welding process (Mohammed et al, 2009).…”