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1 Powered by CPDF ( his is an electronic reprint of the original article. his reprint may differ from the original in pagination and typographic detail. Santos Vilaca da Silva, Pedro Fundaments of the Modelling of Friction Stir Welding. Simulation Day of Workshop on Friction-Stir-Welding in Steel. HZG, Geesthacht, Germany. 21th November Published: 01/01/2014 Document Version Publisher's PDF, also known as Version of record Please cite the original version: Santos Vilaca da Silva, P. (2014). Fundaments of the Modelling of Friction Stir Welding. Simulation Day of Workshop on Friction-Stir-Welding in Steel. HZG, Geesthacht, Germany. 21th November Paper presented at Simulation Day of Workshop on Friction-Stir-Welding in Steel, Geesthacht, Germany. his material is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user.

2 Department of Engineering Design Materials Engineering Materials Joining and ND Fundaments of the Modelling of FSW Pedro Vilaça November, 2014 HGZ, Hamburg, Germany

3 Modelling of Friction Stir Welding Why Modelling? o Know the Physics of FSW o Control the FSW Process o Predict ool life Defects Performance Properties (E.g., Mechanical, Creep, Corrosion) Residual Stress and Deformation o Develop o Assess ool Material ool Geometrical Features Clamping System Process Parameters emperature + Hydrostatic 3D viscoplastic material flow (near field) emperature + Stress /Strain elasto-plastic domain (far field) Metallurgical history

4 Friction Stir Welding Process Fundaments 3D Material Flow Perspective of visco-plastic material flow in longitudinal (x-z) plan aken from the Retreating/Flow side FSW is ALIVE inside!

5 Modelling of Friction Stir Welding Complex Multiphysics Coupled Phenomena

6 Friction Stir Welding Process Fundaments Hot versus Cold Material Flow Pattern Vickers Hardness Field Vickers Hardness Field Courtesy of HZG

7 Fundaments of Modelling Modelling Structure FlowOut Flow In -Energy Energy Balance Internal Energy t A z y x k z y x k z v y v x v c z y x p

8 Fundaments of Modelling Formulation Methods

9 Fundaments of Modelling Discretization Methods Discretization Mathematical Model Discrete Model Finite Element Method Finite Difference Method Finite Volume Method Meshless Method (SPH)

10 Fundaments of Modelling Integration Methods

11 Example of Numerical Modelling Approach Integration CSM / CFD Elastic - Plastic Analysis of the plates remote from tool HAZ and Base Material Viscous - Plastic Analysis near the tool Nugget and MAZ Structural Mechanics Approach (E.g. Abaqus) FE Mesh - Pressure - emperature Integration Updated at interface : - emperature - Pressure Fluid Dynamics Approach (E.g. Fluent) Results Residual Stress Field Residual Deformation hermal History of the HAZ Results Material Flow for different tool geometries hermal History at the vicinity of the tool

12 Example of Numerical Modelling Approach Description of the Integration CSM / CFD his integration imposes a thermal field in the CSM domain equal to the CFD thermal field in the vicinity of the tool: D > Shoulder D X 0 Steps Weld length he integration generates an history that moves the thermal field across the CSM domain to simulate the welding process

13 Example of Numerical Modelling Approach Features of the Integration CSM / CFD

14 Visco-plastic Material Modelling for CFD Zener-Hollomon Model

15 Material Modelling for CFD Zener-Hollomon Model

16 Change in length per unit length (dl/l) Material Modelling for CSM Elastic-Plastic Material with hermal Expansion Solid Mechanics hermo-mechanical Analysis: thermal a expansion E thermal E=73 GPa ; n=0.33 Mechanical Properties at Elevated emperatures emp. [K} ime at emp. [h] YS [MPa] US [MPa] Elong % emp. ºC a expansion [m/m.k] hermal Properties Depending on emperature K () [W/m.K] Cp () [J/Kg.K] Cooling (Austenite) Phase ransformation Cooling to Ambient (Martensite/Bainite) Fusion emperature [K]? Solidus emperature [K]? Liquidus emperature [K]? Co-efficient of expansivity x 10-6 (/ o C) Co-efficient of expansivity x 10-6 (/ o C) Co-efficient of expansivity x 10-6 (/ o C) emperature ( o C)

17 Modelling of Friction Stir Welding Final Remarks Highly non-linear character (geometric, material, formulation) Physical properties vary throughout the FSW process Demands: Reliable Material Model Data (depending on: emperature + Strain Rate) Heat generated at sliding interfaces between the tool and the workpieces material depends on a frictional complex phenomena Visco-plastic flow dissipates significant heat to workpieces thus the correct simulation of material flow in the MAZ is fundamental hermal flow into the tool, anvil and clamping system does affect significantly the thermal field in the workpieces FSW model needs to allow hybrid formulation (solid and fluid mechanics) Not possible to apply symmetry simplifications Complex tool profile implicates a complex discretization

18 Department of Engineering Design Materials Engineering Materials Joining and ND hank You Pedro Vilaça November, 2014 HGZ, Hamburg, Germany