Airbag Folding with Radioss Pre- Simulation

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1 Altair Product Design Airbag Folding with Radioss Pre- Simulation Dmitri Fokin 3 November 2009 European HTC Ludwigsburg, Germany fokin@altair.de

2 Content FE Airbag model Geometrical folder Folding pre-simulation with Radioss Conclusions 2

3 FE Airbag model 3

FE Airbag model: general Fold 7 straps border of the airbag (gas leakage) Fold 8 300 mm 102

Meshed airbag surface with account of folding - Fabric material and FE property - Internal

4 FE Airbag model: general Fold 7 straps border of the airbag (gas leakage) Fold mm 102 mm Fold 6 Fold 5 99 mm 99 mm Fold 1 Fold 2 Fold 4 Fold 3 - Airbag geometry (closed volume) - Meshed airbag surface with account of folding - Fabric material and FE property - Internal airbag contacts - Method for airbag simulation (uniform pressure, ALE, finite volume method) 4

5 FE Airbag model: fabric materials and properties Definition of airbag model is Material definition for the airbag fabric (orthotropic, elasto- plastic materials, no resistance by compression) /MAT/FABR_A/1 MAT_FABRIC # Init. dens. Ref. dens E

6 FE Airbag model: fabric materials and properties Definition of airbag model is Material definition for the airbag fabric (orthotropic, elasto- plastic materials, no resistance by compression) /MAT/FABR_A/1 MAT_FABRIC # Init. dens. Ref. dens E Property definition for the airbag fabric (membrane, no bending stiffness) /PROP/SH_FABR/1 airbag_thickness # Ishell Ismstr

7 FE Airbag model: internal contact Internal contact for airbag fabric components (prescribed contact gap and contact stiffness) /INTER/TYPE7/2 Internal Contact /INTER/TYPE11/1 Internal Contact EE

8 FE Airbag model: solver and inflator Inflator model: position of injectors, jet directions, gas consistence, massflow rates, gas temperature, time to fire, airbag solver (uniform pressure, finite volume) /MONVOL/AIRBAG/1 Airbag # Isur 7 # Scal_T Scal_P Scal_S Scal_A Scal_D # Mu Pext Tphi E # Gammai cpai cpbi cpci # Njet 1 # Gamma cpa cpb cpc # Imass Iflow Smass Itemp Stemp Isensor # Ijet N1 N2 N # Nvent 0 8

9 FE Airbag model: airbag folding Unfolded FE airbag (reference geometry) 9

10 FE Airbag model: airbag folding Unfolded FE airbag (reference geometry) Black box= Airbag Folder Transformation of airbag geometry 10

11 FE Airbag model: airbag folding Black box= Airbag Folder Unfolded FE airbag (reference geometry) Folded FE airbag Transformation of airbag geometry 11

12 FE Airbag model: airbag folding Black box= Airbag Folder Unfolded FE airbag (reference geometry) Folded FE airbag Transformation of airbag geometry Geometrical folder - Translate - Rotate -Scale - Non-linear transformation 12

13 FE Airbag model: airbag folding Black box= Airbag Folder Unfolded FE airbag (reference geometry) Folded FE airbag Transformation of airbag geometry Geometrical folder - Translate - Rotate -Scale - Non-linear transformation Pre- simulation of the folding process using an explicit solver (Radioss) -Exact simulation of the folding process -Simulation of a simplified folding process 13

FE Airbag model: airbag folding Black box= Airbag Folder Unfolded FE airbag (reference geometry) Folded FE airbag Transformation of airbag geometry Combined folder Geometrical folder - Translate -

14 FE Airbag model: airbag folding Black box= Airbag Folder Unfolded FE airbag (reference geometry) Folded FE airbag Transformation of airbag geometry Combined folder Geometrical folder - Translate - Rotate -Scale - Non-linear transformation Pre- simulation of the folding process using an explicit solver (Radioss) -Exact simulation of the folding process -Simulation of a simplified folding process 14

15 FE Airbag model: folding requirements Element sizes, fold thickness and fold layout must be adjusted such that certain requirements are met: i.e. Package space requirements (final size of folded airbag) Requirements for numerical stability (element quality, time step, intersection and penetration free) Requirements for model validity (reliable folding deformation) 15

16 Geometrical folder 16

17 Geometrical folder: simple fold Simple fold consist of: Non-knick elements (regions BCD and B C D ) Knick elements (regions AB, A B, DE, D E ) Following rules are important by airbag meshing for further simple folding 1. Only one element should lie in the knick regions AB, A B, DE, D E 2. Elements in the knick and non-knick region should have approximately same size f O E E D D O A B Before folding A B C D E A B C D E C After folding C d A B 17

Geometrical folder: simple fold Calculation of fold parameters ( 3 variants) Initial data: Distance between layers, d Fold height, f Element size to knick

18 Geometrical folder: simple fold Calculation of fold parameters ( 3 variants) Initial data: Distance between layers, d Fold height, f Element size to knick Elliptic elongation Thickness increase coefficient Output data: Average distance between layers on the knick Node displacements for corresponding folding step 18

19 Geometrical folder: four step algorithm Step 1 Direction of displacement A B C D E A B C D E d 19

20 Geometrical folder: four step algorithm Step 2 C Move nodes CC vertically by the value of node displacement for step 2 A B C D E A B D E Direction of displacement 20

21 Geometrical folder: four step algorithm Step 3 C Rotate all these nodes over node C by 180 grad A B A B C D D E E Center of rotation is the node on the lower surface of the airbag Result of rotation: E D E D A B A B C C 21

22 Geometrical folder: four step algorithm Step 4 E D E D A B A B C C Rotate node C about node C by 90 grad Result of rotation E D E D A B C C A B 22

23 Geometrical folder: four step algorithm Elements deform during folding Inside elements (B C, C D ) will be shorter Outside elements (BC, CD) will be longer O E D Before folding A B C D E A B C D E After folding d f E D O A DB C C Volume of the folded airbag has changed A B 23

24 Geometrical folder: reference geometry Unfolded FE airbag (reference geometry) Folded FE airbag /REFSTA # reference geometry AIRBAG02.ref Initial strains in the folded airbag fabric 24

Fold 2 Fold 4 Fold 3 Geometrical folder requires exact planning of the

25 Geometrical folder: fold planning Fold 7 straps border of the airbag (gas leakage) Fold mm 102 mm Fold 6 Fold 5 99 mm 99 mm Fold 1 Fold 2 Fold 4 Fold 3 Geometrical folder requires exact planning of the airbag geometry: fold lines should be present in the geometry before meshing 25

26 Geometrical folder: fold planing Fold plan for Branch programm Provides a detailed airbag fold plan for further manual airbag folding. Allows to control important characteristics of the airbag: minimal element size, thickness of the folded airbag etc. (Branch programm L.Fredriksson) 26

fold - Open fold -Tuck folds - Rolling Important

27 Geometrical folder: Hypercrash folder Airbag folder is a part of the Hyperworks Types of fold: - Simple fold - Open fold -Tuck folds - Rolling Important feature: Airbag geometry is folded and then meshed! 27

28 Folding pre-simulation with Radioss 28

29 Folding pre-simulation with Radioss Radioss runnable inputdeck with unfolded airbag, materials, contacts etc. but w/o airbag card 29

30 Folding pre-simulation with Radioss Radioss runnable inputdeck with unfolded airbag, materials, contacts etc. but w/o airbag card Fold plan FOLD FOLD 3 (sym to 2)

31 Folding pre-simulation with Radioss Radioss runnable inputdeck with unfolded airbag, materials, contacts etc. but w/o airbag card Fold script generates Radioss inputdeck for folding Fold plan FOLD FOLD 3 (sym to 2)

but w/o airbag card Fold script generates Radioss inputdeck for folding Fold plan FOLD 2 0.0 10.

32 Folding pre-simulation with Radioss Radioss runnable inputdeck with unfolded airbag, materials, contacts etc. but w/o airbag card Fold script generates Radioss inputdeck for folding Fold plan FOLD FOLD 3 (sym to 2) Radioss simulation 32

33 Folding pre-simulation: principal scheme Rotated nodes Rotation center Fixed nodes O o Fold (deformable nodes) 33

34 Folding pre-simulation: principal scheme Rotated nodes Rotation center Fixed nodes O o Fold (deformable nodes) Rotated nodes 90 o Fixed nodes 34

35 Folding pre-simulation: principal scheme Rotated nodes Rotation center Fixed nodes O o Fold (deformable nodes) Rotated nodes 90 o Fixed nodes 180 o Fold (deformable nodes) Rotated nodes Fixed nodes 35

36 Folding pre-simulation: principal scheme (video) 36

37 Folding pre-simulation: blade scheme (video) Rotated elements are deformable and trapped between two rigid blades by a contact 37

38 Folding pre-simulation: knife scheme (video) All airbag elements are deformable. Folding is carried out by moving rigid knives 38

39 Folding pre-simulation: complete run Altair training airbag Element edges follow folding lines 4 symmetrical folds 39

40 Folding pre-simulation: three different meshes Element edges follow folding lines Folding is mesh independent Mesh rotated by 30 grad. Fold lines are parallel to mesh direction Arbitrary fine mesh 40

41 Folding pre-simulation: airbag deployment Fold lines introduced in the mesh Arbitrary fine mesh The airbags have same shape and fold plan but different mesh. Airbag deployment is similar 41

42 Folding pre-simulation: some notes - Radioss model for folding is generated automatically - No intersections and minor penetrations in folded airbag due to sensitive Radioss contacts - Final size of airbag is predicted before folding starts - Transfer from unfolded state (reference geometry) to folded is physically consistent (internal material forces and contact forces provide physically reliable strains in the airbag fabric during the folding) - Folding method is mesh independent - Folded mesh can be used for any solver (RADIOSS, DYNA) 42

43 Example: passenger airbag folding 43

44 Example: description Upper view Side view Airbag surface- typical 3D T-shape form Lower view Housing Inflator Mesh elements Average element size 5mm Simulation time 2h 44

45 Example: fold plan 45

46 Example: fold plan First step: symmetrical zig zag side folds 46

47 Example: fold plan First step: symmetrical zig zag side folds 47

48 Example: fold plan First step: symmetrical zig zag side folds Second: lower rolls Second step: lower rolls 48

49 Example: fold plan First step: symmetrical zig zag side folds Third step: upper roll Second: lower rolls Second step: lower rolls 49

50 Example: fold plan First step: symmetrical zig zag side folds Fourth step: press in housing Third step: upper roll Second: lower rolls Second step: lower rolls 50

51 Example: inputdecks Model of unfolded airbag #RADIOSS STARTER /BEGIN AIRBAG /MAT/FABR_A/1 MAT_FABRIC /PROP/SH_FABR/1 airbag_thickness /INTER/TYPE7/2 Internal Contact /INTER/TYPE11/1 Internal Contact EE /END Fold plan FOLD FOLD 3 (sym to 2) FOLD END FOLD SCRIPT Fold includes Model of unfolded airbag with folding includes #RADIOSS STARTER /BEGIN AIRBAG ## #include FOLD00_0000.inc #include FOLD01_0000.inc ## /MAT/FABR_A/1 MAT_FABRIC /PROP/SH_FABR/1 airbag_thickness /INTER/TYPE7/2 Internal Contact /INTER/TYPE11/1 Internal Contact EE /END # FOLD 2 START /SENSOR/TIME/ T= #enddata 51

52 Example: folding of a passenger airbag (video) Mesh elements Average element size 5mm Simulation time 2h 52

53 Example: fit passenger airbag in housing (video) Mesh elements Average element size 5mm Simulation time 15min 53

54 Example: deployment of the passenger airbag (v) Mesh elements Average element size 5mm Uniform pressure, Simulation time 0.5h 54

55 Conclusions Promising technology for numerical airbag folding Easy to implement in HW No need of additional explicit solver for folding simulation Radioss model for folding is generated automatically Simulation delivers a reliable strains in the folded airbag Folded mesh can be used for any solver (RADIOSS, DYNA) 55

56 Thank you for the attention! 56

Simulation of Curtain Airbag with Arbitrary. Eulerian- Lagrangian Method

Simulation of Curtain Airbag with Arbitrary Eulerian- Lagrangian Method Dmitri Fokin, Eivind Dessarud Altair Engineering Claes Ljungqvist Saab Automobile AB Abstract: Computer simulation is a powerful