Connection Elements for Joint Representation

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For reliable full vehicle modelling taking numerous material properties and characteristics into account several boundary conditions need to be full filled. One particular material aspect is the consideration of failure events especially the failure of joint connections. On full vehicle level joint connections can be grouped by three types of connections: 0-D e.g. spot weld, 1-D e.g. weld line and 2-D e.g. bonded face. These types of connections attach in state of the art full vehicle models shell parts that represent the body structure of a vehicle model.

Connection elements must form a suitable link between shell parts of a body structure and one possibility is to model them by using volume elements. Default continuum mechanics solid elements suffer on very small model time steps or on a significant mass increase caused by the Courant criteria. One solution is a special cohesive like connection element which considers only normal and tangential stress in connection direction and is independent from time step restrictions. The presentation will show an overview of the joint requirements on full vehicle level and the cohesive element calibration, validation and application on selected spot welded and bonded physical samples.

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Connection Elements for Joint Representation

  1. 1. © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) N. Pasligh (Presenter), R. Schilling Crash CAE: Connection elements for joint representation exemplarily spot welds Crash CAE: Connection elements for joint representation exemplarily spot welds
  2. 2. 6/11/20142 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Motivation
  3. 3. 6/11/20143 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Generic b-pillar high overloading crash example Force displacement chart a) Perfect world scenario without failure b) Joint pattern #1 and failure consideration c) Joint pattern #2 and failure consideration d) No connection between b-pillar and side structure e) Sheet metal + joint failure with joint pattern #1 Joint failure need to be considered Reliability required Displacement Force[%ofnofailure] Generic example: Extreme overloading Simple CAE model (no trim) Coarse mesh Simplified sheet metal and spot weld data a e c d b Side structure and b-pillar
  4. 4. 6/11/20144 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Content Joint requirements Full vehicle CAE models History Joint environment Physical connections CAE connections Radioss solution and model approach Examples
  5. 5. 6/11/20145 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Joint requirements
  6. 6. 6/11/20146 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) General joint requirements Automatic joint creation based on push button principle for different detail levels Full integration into HyperMesh, HyperCrash required Correlation between physical and numerical characteristics Good theoretical approach for RADIOSS solver Tension, compression, shear, bending, torsional and mixed behavior treatment (load level, energy consumption, …) 3 to 4 sheet connection treatment Automatic post-processing in HyperView required e. g. percentage to failure - tension, shear, mixed, angle of mixed loading, current loading condition, … Pre-processing Processing Post-processing
  7. 7. 6/11/20147 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Full vehicle CAE models
  8. 8. 6/11/20148 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Full vehicle model history Past Future Past model: Mesh size > 50 mm 30,000 elements No/ basic joint modelling … Today’s model: Mesh size ~ 5 mm 2 - 5 million elements Joint modeling Implemented joint failure criteria … Future model: Mesh size > 1 mm Multi million elements More detailed joint modeling Complex, interactive failure criteria … M o d e l c o m p l e x i t y
  9. 9. 6/11/20149 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Examples of physical joining methods Others • Thermal (Laser welding, brazing, …) • Mechanical (Riveting, screwing, …) Example: Spot welding Bonding
  10. 10. 6/11/201410 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Full vehicle joint environment Detailed FEM-model Time step too small Millions of elements for joints not applicable to full car CAE model Extracted mid surfaces Time step as full car model Few additional elements Applicable for full car CAE Transfer to full vehicle
  11. 11. 6/11/201411 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Type of joints Common nodes Contacts Elements 1-D 2-D 3-D Surface to surface
  12. 12. 6/11/201412 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) RADIOSS solution and model approach
  13. 13. 6/11/201413 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) x y z σσσσxx σσσσyy ττττyx ττττyz ττττxy ττττxz Node 1 Node 2 Node 3 Node 5 Node 7Node 8 5.0 mm Single 3-D joint element shell shell Solid H • Considered element strength calculated at integration points of mid surface • Reference plane: mid surface with 4 integration points • Element height “H” can be zero • Artificial definition possible Connection methodology to connect shell mid surface layer Most important internal forces are considered at four integration points (allows splitting forces into momentums) Element formulation is time step independent σσσσzz ττττzx ττττzy σσσσzz ττττzx ττττzy Node 6 Continuum solid Cohesive solidvs. 3-D joint element example Details of 3-D element treatment
  14. 14. 6/11/201414 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Modeling approach by cohesive /MAT/LAW59/ formulation in Radioss /MAT/LAW59/59 Connection element - D U M M Y - # Init. dens. 7.65E-6 # E G 10.0 123.4 # Nfunc Fsmooth Fcut Y_flag 1 1 0 0 # Y_Func_N Y_Func_T Strain Rate ref. Yield stress Scale 1 2 0.00001 1 /FAIL/CONNECT/59 # EPS_N_MAX EXP_N ALPHA_N SR_N IFAIL ISOLID ISYM 1.0 2 1 0 1 1 1 # EPS_T_MAX EXP_T ALPHA_T SR_T 10.0 2 1 0 # EI_MAX 0 /PROP/CONNECT/59 Adhesive #---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----| /FUNCT/1 Tensile curve # X Y 0 1.0000 1.0 1.0000 /FUNCT/2 Shear curve # X Y 0 1.000 10.0 2.000 Shape parameter Tensile strength vs. displacement Shear strength vs. displacement Failure displ. Modulus data Tension (mode I) Shear (mode II) Joint material card
  15. 15. 6/11/201415 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) *1.rad file setting for MAT/LAW59 /ANIM/BRICK/USR - variable settings for displacement based failure criteria /ANIM/BRICK/USR3/1 /ANIM/BRICK/USR3/1 /ANIM/BRICK/USR5/1 Source: Altair Engineering GmbH, 2013 Joint post-processing Tension (mode I) Shear (mode II)
  16. 16. 6/11/201416 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Joint material card modification Characterization of spot welds for full vehicle models Shear load Width = 0.5 “h” Height“h” Ftension = 2 * Fshear Width = “h” Ftension = Fshear Width = 1.5 “h” Ftension = 0.67 * Fshear Shear load Shear load True thickness flag compensation of mesh dependent momentums Resultingtensionload
  17. 17. 6/11/201417 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Improvement of mixed mode treatment Joint material card update MAT/LAW83 30 ° 60 ° α=1 α=0.1 α=-2 α=-10 Influence of alpha parameter Influence of beta parameter Source: V. Dampuré: Altair Engineering GmbH, 2014
  18. 18. 6/11/201418 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Meshing of joints Meshing proposals CAE 5.0 mm Source: Altair Engineering GmbH, 2011
  19. 19. 6/11/201419 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Examples
  20. 20. 6/11/201420 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) CAE design development support Physical joining Full vehicle test Validation: ComponentCalibration: Coupon Validation: Sub-system 5.0 mm CAE concept Product development
  21. 21. 6/11/201421 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Load case Validation component CAE model Results Force-displacement chart of a component test example Adhesive Spot weld
  22. 22. 6/11/201422 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Validation sub-system CAE modelLoad case Results Adhesive Spot weld Force-displacement chart of a sub-system test example
  23. 23. 6/11/201423 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Product development: Pre-processing Generation of joints Pre-processing E. g. Fiesta single parts Source: A. Hänschke Source: U. Fox Screw Spot weld Automatic model assembly
  24. 24. 6/11/201424 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Full vehicle load case: examples Processing Product development: CAE crash analysis Post-processing
  25. 25. 6/11/201425 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Summary Efficient pre-processing tools needed More efficient integration and fully automatic pre-processing Solve 3T and 4T dependency for multi layer joints Stable connection solving algorithm Stabilize element deletion and energy release rate handling Mixed load handling, joint interaction and mid surface gap treatment Fully supported and automatic visual/ tabulated/ … inspection of joints by post- processing tools Connection elements are for developing a reliable crash CAE design Thanks to Altair team for support! Special thanks to M. Bulla and V. Dampuré.
  26. 26. 6/11/201426 © 2014 Ford Motor Company, All Rights Reserved 7th European Altair Technology Conference , June 24th - 26th 2014, Munich Dr. Niels Pasligh (R&A Europe AMCAE), Dr. Robert Schilling (FoE) Thank you very much for your attention!

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