"VALIDATION OF FRICTION STIR WELDING PROCESS MODELS" By Terry Dickerson & Hugh Shercliff CT slice at the weld root of the exit hole of a 2024-T3 weld. Page 1 NOTE This set of slides was made in response to a request by the conference organiser to fill in a vacated position in the conference schedule. The request was made at short-notice which meant there was inadequate time to produce a proper paper. These presentation slides have been included in lieu of a full paper. Please feel free to contact the author (tld23@eng.cam.ac.uk) about the FSW Benchmark, particularly if you want to contribute to it. Page 2
RATIONALE The physics of FSW is complex. To be meaningful, process models of FSW require validation. Validation can be carried out at a number of levels. However, the most significant will be comparison data from real welds. Answer - produce welds and welding data. Page 3 OBJECTIVES Produce experimental data for validation of FSW modelling: Some things to think To make the data wide ranging to enable validation on several levels. Make sure the welding setup was well defined and compatible with modelling. about when designing FSW experiments: boundary conditions, tool forces & torque, temperatures, flow visualisation, residual stress measurement, weld sizes etc. Page 4
EXPERIMENTAL: Machine (1) CNC Controller Converted Milling Machine Data Acquisition Computers Positions Forces Torque Temperature DLR, Cologne, Germany Page 5 EXPERIMENTAL: Machine (2) Machine head Dynamometer for tool: Forces and Torque Welding Tool Backing bar or anvil Page 6
EXPERIMENTAL: Anvil Welding Tool Fixtures Anvil bolted to machine table Weld panel Air gap under anvil Page 7 EXPERIMENTAL: Thermocouples Thermocouple wires Plugs Weld panel Typical thermocouple locations on section Anvil Weld panel * * * * * * Thermocouple buried in anvil Machine Bed Page 8
EXPERIMENTAL: Markers Annealed copper sheet 0.1mm thick was placed in the weld and then welded through @: Longitudinal Transverse centre Transverse end 105mm 60mm Retreating side Welding Direction 15mm Advancing side 150mm 60mm 60mm Page 9 EXPERIMENTAL: Stop Action At the end of welding the traverse was stopped and the tool unscrewed to freeze-in the material flow patterns. Shown are: Optical Photograph. X-ray image showing the marker. Page 10
EXPERIMENTAL: Summary Validation experiments have been designed to give: Known boundary conditions. Tool position, including plunge depth. Tool forces and torque gives heat input Temperatures at various locations on/in weld panels and in the anvil. Marker materials in the joint Page 11 RESULTS: Welding Data Page 12
RESULTS: Welding Data 22 DMC-E1 2000 Tool Forces / [kn] 20 18 16 14 12 10 8 6 4 2 DMC-E1 Fx DMC-E1 Fy DMC-E1 Fz DMC-E1 Weld Power Input DMC-E1 Weld Heat Input 1800 1600 1400 1200 1000 800 600 400 Weld Power Input / [W] Weld Heat Input / [J/mm] 200 0 0 10 20 30 40 50 60 70 80 90 100 110-2 0 Tool Position from Weld Start / [mm] Page 13 RESULTS: Welding Data Temperature / [ºC] 500 450 400 350 300 250 200 150 100 DMC-E3 DMC-E3 Ch2 DMC-E3 Ch3 DMC-E3 Ch4 DMC-E3 Ch5 DMC-E3 Ch6 DMC-E3 Ch7 Tool Position 120 100 80 60 40 20 Tool Position from Weld Start / [mm] 50 0 0-10 0 10 20 30 40 50 60 70 80 90 100 110 120 Time / [s] Page 14
RESULTS: Metallography 2mm Metallographic Sections of a weld with marker. Page 15 RESULTS: Metallography Metallographic Sections of a weld: top, without marker and bottom, with marker. Page 16
RESULTS: 2D X-ray Imaging X-ray images of a 6mm thick transverse sections of two welds with marker inserts: top, tool on joint-line and bottom, with an off-set. Page 17 RESULTS: X-ray Tomography Computer tomography (CT) models of the welds with marker materials were builtup, an example is shown opposite with the tool position indicated. θ=0 Page 18
RESULTS: X-ray Tomography Plan view of a tomographic model of a weld with marker material in the joint-line. θ=0 θ=270 θ= θ=90 Page 19 RESULTS: CT Slicing Root, z=2.75mm CT slices Middle, z=1.5mm through the tomographic model on various planes. Top, z=0.25mm Page 20
RESULTS: Summary (1) Extensive validation data is available on a number of levels: Global but transient welding inputs tool forces tool torque weld heat inputs tool deflection dynamic plunge depth Transient local data: temperatures at various locations (inc. anvil) Page 21 RESULTS: Summary (2) Validation data is available (continued): Material deformation information metallography 2D and 3D X-ray techniques. Welds are suitable and available for Other metallurgical analyses residual stress measurement So what!!! Page 22
RESULTS: FSW Benchmarks (1) Data like that shown requires specialist equipment, is time consuming and therefore expensive: Some data is to be made available on a copyright but royalty free basis. Published as a website to allow Wide access quick and easy up-dating of information http://www-materials.eng.cam.ac.uk/fsw_benchmark/ Partial access to June 2003 Full access after June 2003 Page 23 RESULTS: FSW Benchmarks (1) Currently one set of data on the site welds in 2024- T3, 6mm thick. the data is extensive Should other welds be added? Page 24
CONCLUSIONS Welding experiments have been designed to support and validate modelling of friction stir welding. The experiments have produced a wide range of high quality data that enables validation at a number of different levels. Some of this data will be openly available to the FSW community. Page 25 ACKNOLEDGEMENTS The work was supported by the European Community under Competitive and Sustainable Growth (1998-2002). Project: Joining Dissimilar Materials and Composites by Friction Stir Welding. Contract: G5RD-CT-1999-00090. The authors thank Mr. Frank Palm at EADS (Ottobrunn, Germany) and the technical staff at DLR (Cologne, Germany) for their help with the experiments. The FSW Benchmark has additionally be supported by TWI Limited (Cambridge, UK) Page 26
SOME ASSOCIATED WORKS [1] Dickerson T.L., Shi Q-Y. and Shercliff H.R., Heat flow into friction stir welding tools, Proc. 4th Int. Symp. on Friction Stir Welding, Salt Lake City, Utah, USA, May 2003. [2] Dickerson T.L., The Friction Stir Welding Benchmarks http://www-materials.eng.cam.ac.uk/fsw_benchmark/, Version 0.1 (draft), January 2003 (restricted access until June 2003). [3] Shercliff H.R. and Colegrove P.A., Modelling of friction stir welding, in Mathematical Modelling of Weld Phenomena 6 (eds. H. Cerjak and H.K.H.D. Bhadeshia), Maney Publishing, London, 2002, 927-974. Page 27 SOME ASSOCIATED WORKS [4] Dickerson T.L., Shercliff H.R. AND Schmidt H A weld marker technique for flow visualization in friction stir welding, Proc. 4th Int. Symp. on Friction Stir Welding, Salt Lake City, Utah, USA, May 2003. [5] Shi Q.Y., Dickerson T.L. and Shercliff H.R., Thermomechanical analysis on welding process of aluminium 2024 with TIG and FSW, Proc. 6th Int. Conf. on Trends in Welding Research, Pine Mountain, Georgia, USA, April 2002. [6] Dickerson T.L., Shi Q-Y. and Shercliff H.R., Thermomechanical FE modelling of friction stir welding of al-2024 including tool loads, Proc. 4th Int. Symp. on Friction Stir Welding, Salt Lake City, Utah, USA, May 2003. Page 28