Current joining research at KTH Production Engineering XPRES Arne Melander
Contents: Overview of research activities Example 1: Friction stir welding of hybrid joints Example 2: Distortion in laser welding
Overview current research at KTH, IIP Hybrid joining Al/thermoplastics Al/thermoplastic composites Al/steel Laser welding distortion prediction with FEM Spot welding Process planning with FEM
Joining of aluminium alloys to thermoplastics with the Friction Stir Welding method Wallop Ratanthavorn and Arne Melander Production engineering XPRES KTH
Aim Purpose of work: To join thermoplastic sheet with aluminium in overlap joints. Joining process FSW is used to generate the joints. FSW tool applied from the aluminium sheet side. Adhesive and mechanical locking are generated.
Joined materials AA6111 Mostly used in automobile structures as aluminium alloy sheet parts in hood and door The main alloying elements of AA6111 aluminium alloy are 0.63 %Si, 0.75 %Cu, 0.76 %Mg with a balance of Al. Polyphenylene sulfide (PPS) High performance thermoplastic that exhibits good thermal stability and chemical resistance High degradation temp. = 500 C Melting temp. = 285 C
Joining technique Lap joints between AA6111 (top sheet) and PPS (bottom sheet) were joined by FSW
How the joint looks like? Mixture of Al fragments and thermoplastic Smooth surface on the bottom side
Results Joint strength Three trends from tensile testing results; Small translation speed leads to the formation of void and gap at interface Large translation speed leads to large metallic chips Smooth interface at large translation speed negative to strength
Results Fracture surfaces
Results Fracture surfaces (continued)
Conclusions Friction stir welding can successfully be used to form joints between aluminium alloys and thermoplastics The joint formation process is very different from FSW applied to aluminium alloys
Karl Fahlström Swerea/Högskolan Väst karl.fahlstrom@swerea.se Oscar Andersson VCC / KTH oanderss@kth.se
Distortion control in laser welding of UHSS Manufacturing Increased use of UHSS Increased use of laser beam welding Simulation Lighter and stronger Fixturing & process Occurring distortions during welding needs to be controlled and understood!
Geometries and material grades Type cases chosen simulating A- and B-pillar Grades used (t = 1.0 mm): MBW-1500P Docol 1700M DP800 Docol 200
Weld clamping and sequence Clamping designed for research 10 clamps in total 5 clamps on each flange Individually controlled by pneumatics Weld sequence Welding along flanges Cooling after welding Unclamping in sequence
Three types of simulations 1) Simplified simulations using commercially available software, ESI Weld Planner 2) Developed simplified simulations in LaserLight using Abaqus. 3) Detailed simulations using ESI Sysweld.
2) Simplified simulations Step 1: Local thermal model Moving cylidnrical heat source Temperature dependent material data Computation time: 30 45 min Output: peak temperatures in sheet Step 2: Global mechanical model Static model, shell elements Load: peak temperatures near weld Output: geometrical distortions
Dominating distortions for single hat
Simulation results Simplfied model Simulation results [mm] 12,00 10,00 8,00 6,00 4,00 2,00 MBW-1500, 1.5 m/min MBW-1500, 3.5 m/min MBW-1500, 7.5 m/min DP800, 1.5 m/min DP800, 3.5 m/min DP800, 7.5 m/min Mild Steel, 1.5 m/min Mild Steel, 3.5 m/min 0,00 0,00 2,00 4,00 6,00 8,00 10,00 12,00 Experimental measurement [mm] Mild Steel, 7.5 m/min
Detailed simulations with Sysweld Thermal laser heat source Thermal data: Density Specific heat Heat conductivity Temperature field Distortions Mechanicl data: Elastisk data Thermal strains
Simulation results Detailed simulations 5,00 4,50 4,00 Simulation [mm] 3,50 3,00 2,50 2,00 1,50 MBW-1500 3.5 m/min MBW-1500 7.5 m/min MS 3.5 m/min MS 7.5 m/min 1,00 0,50 0,00 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 Experiment [mm]
Conclusions: Distortion in laser welding of thin sheet structures can be made with FE methods of different complexity. Methods can be designed for quick process planning and for detailed process analysis.
Thank You!