Presentation of PAM-CRASH v2004. Part 1: Solver News

Transcription

1 Presentation of PAM-CRASH v2004 Part 1: Solver News. 1

2 Overview New Options Elements Materials Others Quality Numerical precision and robustness 2

3 CRASH/SAFE 2G Evolution V2002: Basic reengineering Common source SMP/DMP solver V2003: DMP Performance Full DMP (implement missing SAFE-options) V2004: Quality Numerical robustness 3

4 CRASH/SAFE 2G Evolution V11.0 V11.1 V12.0 Pam Solid core library Sources: pages 2800 files 31.8 Mbyte V94 V95 V96 V97 V98 V2000 V2002 V2003 V2004 Lines (K) 4

5 Overview New Options Elements Materials Others Quality Numerical precision and robustness 5

6 New 4 Node Tetra New real 4-node tetra element in V2004 Implemented for all solid material laws One integration point, hourglass free Faster then degenerated Hexa Hourglass control is skipped Only 4 nodes are treated Degenerated 4-node Hexa not accepted by default Highly recommended for compressible materials: Foam, Honeycomb Good for compressible elastic (i.e. MTYPE 1 elastic) Don t use for incompressible materials (locking occurs) Elastic-plastic Rubber 6

7 New 4 Node Tetra Foam example: Impactor on foam block Hexa (SOLID / ), 10-node tetra (TETRA / ) and 4-node tetra (TETR4 / ) give slightly the same result Degenerated Hexa is too soft 7

8 New 4 Node Tetra Elastic-plastic example Tension test Hexa (SOLID / ), 10-node tetra (TETRA / ) and 4-node tetra (TETR4 / ) give slightly the same result for elastic domain Degenerated Hexa is too soft For Plasticity TETR4 is too stiff (locking) 8

9 Overview New Options Elements Materials Others Quality Numerical precision and robustness 9

10 Materials New materials MATER 121 nonlinear visco-elastic material MATER 128 anisotropic elastic-plastic material with failure criteria (MATFEM) Enhanced materials Stiffness proportional damping for all solid materials Initial equivalent plastic strain for elastic-plastic shell materials MATER 105/106 element elimination control MATER 107 optional FLD per integration point MATER 108 added orthotropic elastic behavior MATER 223 user rupture model 10

11 Shell: MTYPE 121 G Sell model Initially meant for plastics forming Visco-elastic model For CRASH/SAFE: Temperature dependency is inactive Validated by with U. of Valenciennes & Visteon ε=εe+ ε v σ=σe= σ v with σ = σ η= e Eε e =η v ε v w spring NL-damper K h h 2 m 1 ( ) 1+ h ε 2 m 1 p+ h ε p ε p wεp K 1 e

12 Shell: MTYPE 128 MATFEM s CRACH Library (Optional) Model takes into account different rupture mechanisms Accounts process history Validated for HSS & Aluminum sheet metal (BMW) Parameter identification methodology developed by MATFEM Availability: As an option in PAM-CRASH 2004 and special versions of PAM- STAMP PAM-STAMP 2G: planned for version

13 Stiffness Proportional Damping for Solids Stability improvements Damp out artificial numerical noise Very good experiences for shell structures Highly recommended for solids too to be use by default Enhances dynamics behavior of materials Critical example: very large displacements single precision not for typical crash cases Instability without stiffness-proportional damping 13

14 Initial equivalent plastic strain Initial equivalent plastic strain Implemented for all elastic-plastic shell Material models User imposed value on PART card Could be used for: investigation of pre-straining in an early stage (no stamp results are available) parametric studies of pre-strain influence 14

15 Initial equivalent plastic strain Example: 15

16 Elimination MTYPE 105/106 New optional element elimination control for material type 105 and 106: Default: element eliminated if ALL integration points over thickness reached the strain criterion Problem: no elimination in pure bending V2004 new and optional: element eliminated if ONE integration point is beyond the criterion. The default remains as in previous versions New elimination criteria activated by a flag on the material card 16

17 Elimination MTYPE 107 New optional element elimination control for material type 107: Default: FLD criterion is evaluated on the middle integration point Problem: FLD don t see bending V2004 new and optional: Criterion is evaluated at each thickness integration point Fails when the FLD curve is reached in one integration point The default remains as in previous versions New elimination criteria activated by a flag on the material card 17

18 Orthotropic Elastic MTYPE 108 Optional orthotropic elastic behavior is available for Shell element Material type 108 Orthotropic elasticity input by: Either, given orthotropic elastic moduli Or, by extrapolating the coefficients of the orthotropic plasticity law (Hill). Applications: short fibers sheet molding compounds (SMC) orthotropic elasticity represents: Proper elastic loading Proper unloading 18

19 Other Material enhancements User rupture for 223 Dynamic shared object (as user mat) For modeling spot welds or other 1-D entities which needs high customized failure law Access to all 6 DOF s Deformation Velocity MAT 301 for ELINK User defined sharp angle To be imposed on PART card Default 60 (was fixed in previous versions) 19

20 Overview New Options Elements Materials Others Quality Numerical precision and robustness 20

21 LINCO Linear constraint option Linear imposed relation for two nodes Can couple different DOFs Translation X with translation X Rotation Y with rotation Z ATTENTION translational and rotational DOFs could not be coupled! Could be used to do simple mechanism: Steering column Throttle ATTENTION not compatible with other constraint options 21

22 Contact Pressure Crash Contacts are focused on: Maximum contact stiffness to avoid penetration Maximum numerical robustness Drawback: Contact pressure computation is not exact!!! Why? Contact stiffness Nodal area V2004: flag to get precise contact pressure (IPCP flag) Implemented for contact type 33, 34, 36, 44, 54 Useful for applications: Pressure depended friction Precise contact pressure output Don t use it for std. CRASH/SAFE applications 22

23 Contact Pressure Example IPCP: Solid cube loaded to get constant pressure For solid elements For contact Without IPCP With IPCP 23

24 Job Interaction New signal file actions Manage computer resources with running jobs SLEEP echo SLEEP > signal puts computation into sleep mode RESUME echo RESUME > signal reactivates computation Compatible with SMP and DMP 24

25 Input/Output Enhancements Default FILE name changed: no FILE keyword: Name of input deck without path and extension is used for all output files DSY,THP, Plot dump Restart *.msg, *.LIS, Advantage: copied and modified input will not overwrite old results Use optional keyword: FILE to keep backward compatibility 25

26 Input/Output Enhancements Initial mass scaling contour Attention! Static variable (constant over time) Increase DSY file without delivering additional information Use for data check to check mass increase Deactivate for final run Output listing clean-up Name reprint for all options Numbers and IDs are printed I8 Format improvements 26

27 Overview New Options Elements Materials Others Quality Numerical precision and robustness 27

28 Plink Robustness PLINK precision enhancements Significant improvement for single precision Very stiff plinks Many cycles Less numerical noise More stable Bumper Test 28

29 Contact Energy Computation Total energy may not constant for Airbag cases Contact identified as problem Two contributions missing in previous versions Contact damping work Energy absorption for kinematic iterations Improved for V

30 Other Numerical Improvements Rigid body algorithm Rigid body with initial velocity may generate high acceleration peak in cycle 1 Problem happens in single precision only Round off and numerical precision problem Completely solved in V2004 with internal reorganization of the equations to be less round off sensitive 30