Multidomain technics applied to Digimat / Radioss simulations

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Multidomain technics applied to Digimat / Radioss simulations

  1. 1. Multidomain technics applied to Digimat / Radioss simulations: How to use advanced material modelling features with acceptable calculation time ? Frank Braymand Engineered Sealing and Structural Solutions For the Worldwide Automotive IndustryConfidential 14 November 2011
  2. 2. Agenda  Product overview  What is digimat ?  Integrative simulation with Digimat  Why are we using digimat ?  What is multi-domain ?  A real application  Radioss/Digimat application  Pamcrash/Digimat application  Conclusions 2
  3. 3. HOW CBS® WORKS ? “Buckling” High strength expandable bonding Carrier - Thermoplastic CBS® keeps the stability of - BMC - aluminum the cross section - steel 3
  4. 4. HOW CBS® WORKS ?• HEAT ACTIVATED SEALING AND STRUCTURAL FOAMS 4
  5. 5. DESIGN IN MULTIPURPOSE APPLICATION – CITROEN C4 PICASSO CBS® solution was preferred from the very beginning of the body design for full weight and performance benefit. New generation concept to fulfill several purposes : - crash (front, rear, side) - roof crush - NVH (dynamic stiffness) - acoustic EuroCarBody Award 2006 Weight saving : 12 kg / vehicle Total 7,000 vehicles / week 5
  6. 6. Agenda  Product overview  What is digimat ?  Integrative simulation with Digimat  Why are we using digimat ?  What is multi-domain ?  A real application  Radioss/Digimat application  Pamcrash/Digimat application  Conclusions 6
  7. 7. Some material specificities of short fiber reinforced polyamideThe material properties are influenced by fiber orientation  ISO 0 deg 45 deg 90 deg and influenced by strain rate dependency  7
  8. 8. Fiber orientation distribution : anisotropic material properties Through the thickness Flow direction Low tensile stiffnessAlong the part High bending Thickness High tensile Low bending stiffnessGating Anisotropic material properties
  9. 9. What is Digimat ?• Material models library, based on homogenization methods (Mori-Tanaka) – For multi-phase (composite) materials – Coupled simulations rheology/mechanics – Commercial product, opened and documented (no black box)• Already linked with major CAE software – Abaqus, – LS Dyna, – Pamcrash, – Radioss crash (cf. L&L Products paper HTC 2009) – Radioss Bulk (cf. L&L Products paper HTC 2010) Robust design (material/process handling) Optimal design (weight, cost vs performance) 9
  10. 10. Material identification processThe material model is defined by :• Matrix material data – Density – Property type (elasto-plastic, viscoplastic, …) – Failure criterion• Fiber material data (similar as above)• The fiber phase is defined also by : – Fiber content – Fiber orientation tensor (from Moldflow or others) – Fiber length distribution – Fiber aspect ratio (length/diameter) 10
  11. 11. Results – Tensile test ISO 527 1BWith a unique material dataset, Digimat can capture the orientation effect 11
  12. 12. Why are we using Digimat ?• To get reliable results through a better and realistic material description• Main drawback : – calculation time is drastically increased• Solutions – Use more processors – Improve the algorithms (E-Xstream) 12
  13. 13. Why are we using Digimat ?• To get reliable results through a better and realistic material description• Main drawback : – calculation time is drastically increased• Solutions – Use more processors – Improve the algorithms (E-Xstream)• Direct benefits will be found when developping a single component out of a structure• What happend when the component is implemented in a structure in a real project ? 13
  14. 14. Side crash 150 000 elements, # 25 % digimat elements Body in white Reinforcement • 60 000 nodes, • 33 000 nodes • 56 000 elements • 34 000 elements Barrier • 44 000 nodes, Hardware/Software • 35 000 elements • 16 procs Intel Xeon 3 GHz (2007), Linux. • Radioss 10.0.4 • Digimat 4.1.2Public domain snapshots. 14
  15. 15. Digimat / explicit time step best practices• Decrease the time step (5 to 10 times lower) to reduce load increments, and have convergence,• Decreasing again the time step is also better than having long digimat loopsFor each time step• Reducing the time step of a full model for a reduced set of elements is a waste of time and ressource.• A solution is to use multi-domain technics. 15
  16. 16. Agenda  Product overview  What is digimat ?  Integrative simulation with Digimat  Why are we using digimat ?  What is multi-domain ?  A real application  Radioss/Digimat application  Pamcrash/Digimat application  Conclusions 16
  17. 17. What is multi-domain ?• Main idea : split the model in two (or more) models.• These models will run in parallel – With differents time steps – With their own processors Model A Master Model B (na procs) process (nb procs) 17
  18. 18. How to use it ? Model A Time step ta Na procs• Split the models in two slave input decks, Model B and create a master deck Time step tb Nb procs• Define connections between each model Model A Model B Model A Model B• Set how many processors are needed for each model so that each single process run in parallel.• That’s it ! Specifics keywords are needed for each step, so you will use your prefered text editor … 18
  19. 19. Side crash 150 000 elements, # 25 % digimat elements • Isotropic simulation time step : 0.5 µs • Digimat simulation time step : 0.05 µs (mono & multi domains) / 1,7 ?Public domain snapshots. • Multi-domain technics are really relevant to reduce the simulation time. • This result is not optimal ( more processors, HW11, MPI, Digimat 421, …) 19
  20. 20. Mono / Multi domains results consistency• Similar results 20
  21. 21. Mono / Multi domains results consistency• Similar results 21
  22. 22. Mono / Multi domains results consistancy• Similar failure location 22
  23. 23. Another example : 1500000 elements, 12000 digimat elementsFront crash (Pamcrash / Digimat). x 1/5 Public domain snapshots.• Digimat + monodomain option could be a No GO !• Multi-domain technics are again relevant to reduce the simulation time with digimat.• Speed up = f(standard elements, digimat elements, number of processors) 23
  24. 24. Conclusions• Full crash model simulations using Digimat lead to unacceptable simulation time (several weeks).• Multi-domain technics are really relevant to use Digimat’s benefits in car developpment (days): – Lightweight, – Cost efficiency, – Predictive, robust design• Thanks to Altair and E-Xstream for their HIGH involvement in this work. 24
  25. 25. Update on wish list 2010 Digimat / Radioss BlockAltair + E-Xstream Product Managers• Currently limited to 10 layers, constant thickness (20 variables layers still on going) • Digimat user material available with Hypercrash • Specifics outputs (SDV) readable in Hyperview. • Radioss Block implicit in development • Multi-Model-Coupling preprocessing not completly supported by Hypermesh-Hypercrash. Some operations are needed : files manipulations through text editor. • Multi-Model-Coupling computation time improvement must be improved (target : over day, over night)  25
  26. 26. Update on wish list 2010 Digimat / Radioss BulkAltair + E-Xstream Product Managers• Interface without user material (MAT8 anisotropic material, extra pre-processing 1 h) • Huge data files  26
  27. 27. THANK YOU FOR YOUR ATTENTION ANY QUESTION ? Multidomain technics applied to Digimat / Radioss & Digimat /Pamcrash :How to use advanced material modelling features with acceptable calculation time ? Frank BRAYMAND L&L Products - Advanced Engineering - Structure & Material Expert frank.braymand@llproducts.eu +33 (0) 388 478 578

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