occupant safety and airbag deployment

Chapter 21: Occupant Safety and Airbag Deployment

21

Occupant Safety and Airbag Deployment

Summary Introduction

375 376 376

Requested Solutions FEM Solution Results 379 376

Pre- and Postprocess with SimXpert Input File(s) Animation 418 418

380

CHAPTER 21 375 Occupant Safety and Airbag Deployment

SummaryTitle Features Geometry Chapter 21: Occupant Safety and Airbag Deployment Airbag Deployment with Occupant Unit dimensions: mm, kg, ms, KN, GPa, K, J

Material properties

Car frame: Airbag:

Rigid Fabric (MATD034) Density = 8.76E-07 Ea = 0.3; Eb = 0.2 nab= 0.2; Gab = 0.04 CSE = 1; EL = 0.06; PRL = 0.35 LRATIO = 0.1; DAMP = 0.4

Initial airbag gas: Density = 1.2E-9; Pressure = 0.000101; Temperature = 294.34 Gamma gas constant = 1.4; R gas = 286.98; CP gas = 1004 Inflator: Rigid R gas inflator = 353.78; CP gas inflator = 1191 The Inflator Mass Flow Rate and the Temperature of the gas as a function of time are defined by tables. Hybrid 3 - 50 (LSTC.H3.022908_Beta_Rigid.50th fabric (MATD034) and seatbelt material (MATDB01)

Dummy: Seatbelt: Analysis type Boundary conditions Applied loads Element type FE results

Transient explicit dynamic analysis (SOL 700) Fixed except an airbag and a dummy Initial velocity 15 mm/ms to a dummy. Prescribed Mass Flow Rate and Temperature of Inflator Gas 1-D beam element, 2-D shell element, 3-D solid element Plots of deformed shapes at various steps.

376 MD Demonstration ProblemsCHAPTER 21

IntroductionAutomotive companies perform crash simulations including airbags and dummies to predict the forces that would be exerted on the passenger. For people of average size, the airbag can be simulated using a uniform gas bag method where a pre-determined pressure profile is applied inside the airbag surface. In some crash scenarios, such as Out-ofPosition (OOP), the passenger is already leaning forward at the time of airbag deployment, in which case the flow is not uniform and the pressure method is not accurate. Instead, Full Gas Dynamic approach (CFD method) is used to accurately simulate the gas jet, and its pressure distribution inside the bag. This crash example is based on the full gas dynamic approach where an occupant dummy impacts the airbag.

Requested SolutionsA numerical analysis will be performed to predict the behavior of an airbag and an occupant dummy during crash simulation.

FEM SolutionThe units of this model are mm, kg, msec, KN, GPa, K, and J.TSTEPNL describes the number of time steps (20) and time increment (2 msec) of the simulation. End time is the product of the two entries. Notice here that the time increment is only for the first step, and in this analysis, it is overruled by the addition of an initial time step parameter: PARAM, DYINISTEP, 1.E-7. The actual number of time increments and the exact value of the time steps are determined by SOL 700 during the analysis. The time step is a function of the smallest element dimension during the simulation. TSTEPNL 1 20 2.

AIRBAG instructs SOL 700 to create an airbag using either the full gas dynamic (CFD) method or using a uniform gas

bag method. Here, the CFD method will be used. Inflow of gas into the airbag is defined by the entries following theINFLATOR key word.

AIRBAG + + + + + + + + +

7 ON 1 1.2E-9 NONE INITIAL0.000101 294.34 INFLATOR 9 1 353.78 1191. GAS 2 0.0 0.02897CONSTANT GAS 4 0.0 0.0235CONSTANT

3 CFD

20. 286.98 2 1004. 1191.

20. 1004.

20. 1.

MATD034 represents SOL 700 Material #34. It is used to model fabric material.


For the airbag and the Seatbelt the following fabric materials are used respectively: MATD034 0.2 + 1. + 0.0 + 0.0 + 0.0 MATD034 + + + 2 0.06 0.0 0.0 0.0 292 1.E-6 0.0 1. 0.0 2.9 0.0 0.0 2.9 8.76E-7 0.04 0.35 3. 0.3 0.1 0.0 0.0 0.2 0.4

The ends of the Seatbelt are modeled with Seatbelt elements (CBELT), Seatbelt property (PBELTD), and Seatbelt material (MATDB01). The loading and unloading curves (force vs. strain) are defined in the following tables:MATDB01 TABLED1 + 0.1 + ENDT TABLED1 + ENDT 293 61 0.0 4.2 0.5 62 0.0 0.0 1.00 8.2 0.45 0.0 6.7 7.6 0.05 1.00 1.7 8.2 1.E-6 61 62 3.

The dummy is modeled by using many element types and joints: CPENTA, CHEXA, RBJOINT, RBJSTIFF, CBAR, CBEAM, HGSUPPR, CSPR, PSPRMAT, MAT1, MATRIG, and several of MATD0**.EOSGAM defines the ideal gas inside the airbag.

EOSGAM

1

1.4 286.98

Bulk Data Entries that Define Contact Relations and Contact BodiesBCTABLE defines Master-Slave as well as self contact.

BCTABLE 1 + SLAVE 1 + + + + + + MASTERS + SLAVE 5 + + 0.3 + +

1 0.5 + 2 0.5 1 0.3 SS2WAY 2 3 5 YES+


+ + + ..

20. 1. MASTERS 6 1. YES+

BCBODY is a bulk data entry that defines a flexible or rigid contact body in 2-D or 3-D. It could be specified with a BSURF, BCBOX, BCPROP, or BCMATL entry.

BCBODY BCBODY ..

1 5

3D 3D

DEFORM DEFORM

2 13

Two types of entries are used to define 3-D contact bodies.BPROP and BSURF define 3-D contact regions by element properties and a contact surface or body by element IDs,

respectively. BCPROP .. BSURF .. Using the BCTABLE and several BCBODY, BCSEG, and BCSURF entries, the following contacts are defined as: Contact Number 1 2 3 4 5 6 7 8 9 10 2 6 2527 1 1 THRU 2 THRU 10922 3 2516 4 7

Slave Airbag Pelvis Neck ring Ribs Ribs Airbag Seatbelt Lower body Feet - hands Airbag

Master Airbag Connection bones to legs Neck Torso Breast Dummy upper parts Torso - lower body - neck Chair Frame Frame

Boundary conditions are specified for the car frame, and chair. Because the car frame is rigid, enforced motion entry (SPCD2) is used. $ Constraint for Frame chair floor SPCD2 6 RIGID MR289 SPCD2 6 RIGID MR289 SPCD2 6 RIGID MR289 SPCD2 6 RIGID MR289 1 2 3 5 0 0 0 0 555 555 555 555 1. 1. 1. 1.


SPCD2 SPCD2 TABLED1 555 + 0.

6 6 0.

RIGID RIGID

MR289 MR289 1000. 0.

6 7 ENDT

0 0

555 555

1. 1.

Results

Figure 21-1

Occupant and Airbag at Various Positions


Pre- and Postprocess with SimXpertIn this example, a folded airbag and its interaction with a dummy with a seat belt are shown. Also, an animation of the deformation of the airbag and the displacement of the dummy is shown. To enter the MD Explicit Workspace:a. Click MD Explicit b. File: Save As c. File name: airbag d. Click Save

a

b

c

d


Specify the Model Unitsa. Tools: Options b. Select Units Manager c. Click Standard Units d. Select the line with mm, kg, ms, ... e. Click OK f. Return to User Options screen and click OK

b

c

a f

d

e


Specify Input/Outputa. Tools: Options b. Select Input/Output c. Click Nastran Structures d. Unselect Reduce Parts e. Click Apply f. Click GUI Options g. Click Solver Card h. Click OK

b c

d

a

e

g f

h


Import the Airbag Modela. File: Import b. Select Nastran c. Look in: AIRBAG d. Select airbagconstant_new_spiral_simx.bdf e. Click Open

a

b

c d

e


Import the Airbag Modela. Tools: Transform b. Select Rotate c. R.Axis: For X, enter 0; for Y, enter 1; for Z, enter 0 d. For Angle, enter 90 e. Select Elements f. Click All g. Click Done h. Click Exit

c

da

e

b

f g h


Check the Airbag DataTo rotate the airbag Rigid Wall.a. Right click Rigidwall Planar_2 b. Click Properties c. Modify WALL: For XP, enter -1.5; for ZP, enter 0; for NX, enter 1; for NZ, enter 0 d. Click Modify

ab

c

c

c

c

d


Check the Airbag Data (continued)To Change Damping Coefficient Fabric Materiala. Right click Material MATDO34 b. Click Properties c. For DAMP, enter 0.4 d. Click Modify

a b

c

d


Import Dummy Modela. File: Import b. Select Nastran c. Select LSTC.H3.022908_Beta_RigidFE.50th.dat d. Click Open

a c

b

d


Import Car Frame Modela. File: Import b. Select Nastran c. Select Body_Final.bdf d. Click Open e. Right click Model Views, select Right

a c

b

d

d

e


Import Car Frame Model (continued)a. View: Entity Display b. Select Coordinate Frames Shown c. Select Rigid Elements d. Select Unreferenced Nodes Shown

a

b

c

d


Dummy Positioninga. Safety: Positioner Panel b. Select Parts by clicking Torso c. Dummy Positioning: select Dummy H-Point d. For H Point Location, change X to 560; change Y to -279.90; change Z to 55 e. For Rotation, change Y to 10; change Z to 180

a

b d e

c

b


Dummy Positioning (continued)a. Component Positioning: For FullArm_UpDown_, change X to -10.00 (do once for each arm) b. For lower_arm_right, change Z to -90.0 c. For lower_arm_left, change Z to -90.0 d. For neck_head, change Y to 7.0

a b

c d


Dummy Positioning (continued)a. Component Positioning: For Upper_leg_left, Curr. X = 5.00 b.For lower_leg_left, change to -21.0 c. For upper_leg_right, Curr. X = 10.00 d. For lower_leg_right, Curr. X = -32.00 e. For foot_right, change to 15.0 f. Click Exit g. Right click Render, select FE Shaded

a

b c e d f

g

g


Create Seat BeltPlot dummy and chair only:a. Right click LSTC.H3.022908_..., select Show Only b.Right click PSHELL_2468_..., select Show c. Tools: Options, Window d. Color: Entity, select Edge Color, Gray e. Click OK f. Shift Right mouse, Screen Rotate

a b b a

f c d

e


Create Seat Belt (continued)Create seat belt:a. Safety: Route Seat Belt b.Click Torso c. Click Pelvis d. Click Upper Leg Left e. Click Done f. Click Node 1 g. Click Node 2 h. Click Node 3 i. Click Done j. Click Exit

a f

b c d j

h

g e

i


Check Seat Belt: Shell PropertyCreate seat belt:a. Right click SeatBeltShellMaterial b.Click Exit c. Right click SeatBeltShellProperty d. Double click MID e. Select SeatBeltShellMaterial 290 f. Click OK g. Click Modify

a b c

d

g

e f


Check Seat Belt: 1D Element PropertyCreate tables for seat belt load and unloading curves (Force vs. Strain):a. Field/Tables: TABLED1 b. Click ADD six times to make six rows c. Fill in X-Y values d. Click Update e. Click Create f. Click Exit g. Repeat a. through d. for the second table except for step b. For step b., click ADD two times to make two rows

a

c

g

b

d ef


Check Seat Belt: 1D Element Property (continued)Add tables for seat belt load and unloading curves (Force vs. Strain) to SeatBeltMaterial:a. Right click SeatBeltMaterial b.Double click LLCID c. Select TABLED1_60_60 d. Click OK e. Double click ULCID f. Select TABLED1_61_601 g. Click OK; then click Modify h. Right click SeatBeltProperty i. Double click MID1 j. Select SeatBeltMateriaL 291 k. Click OK; then click Modify


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c d g

f

i k

j k


Delete Imported Simulation Data and Some Incorrect Contact Definitionsa. Under LSTC.H3.022908_Beta_RidigFE.50th.dat tree, right click Simulation; select Delete b. Under LSTC.H3.022908_Beta_RidigFE.50th.dat tree, select DEFORM_5 through BCTABLE (click and Shift click); right click and select Delete c. Under eulerbagconstant new spiral simx.bdf tree, select BCPROP_1 through BCPROP (click and Shift click); right click and select Delete

a

b

c


Check Duplicate IDsa. Tools: ID Management b.Select Duplicate ID Manager c. Click OK

a

b

c


Create Contact Bodiesa. LBCs tab: Deformable Body b. Name: Deform_2; click PSOLIDD_72_...; Ctrl click PSOLIDD_79_...; click Apply c. Name: Deform_3; click PSOLIDD_49_...; Ctrl click PSOLIDD_50_...; click Apply d. Name: Deform_4; click PSOLIDD_25_...; Ctrl click PSOLIDD_26_...; Ctrl click PSOLIDD_28_...; Ctrl click PSOLIDD_29_... Ctrl click PSOLIDD_86_...; Ctrl click PSOLIDD_262_... Ctrl click PSOLIDD_263_...; Ctrl click PSOLIDD_264_... Ctrl click PSOLIDD_265_...; Ctrl click PSOLIDD_267_... Ctrl click PSOLIDD_268_...; Ctrl click PSOLIDD_269_...; Click Apply e. Name: Deform_5; click PSOLIDD_10_...; click Apply

a

b

c

b Pelvis d e

c Axes

e Ring Neck d Ribs


Create Contact Bodies (continued)a. Name: Deform_6; click PSOLIDD_25_...; Ctrl click PSOLIDD_26_...; click PSOLIDD_28_...; Ctrl click PSOLIDD_29_...; click PSOLIDD_268_...; Ctrl click PSOLIDD_269_...; click Apply b. Name: Deform_7; click PSOLIDD_65_...; click Apply c. Name: Deform_8; click PSOLIDD_98_...; click Apply d. Name: Deform_9; click PSOLIDD_263_...; click Apply e. Name: Deform_10; click PSOLIDD_18_...; Ctrl click PSOLIDD_65_...; Ctrl click PSOLIDD_72_...; Ctrl click PSOLIDD_93_...; Ctrl click PSOLIDD_68_...; Ctrl click PSOLIDD_69_...; Ctrl click PSOLIDD_70_...; Ctrl click PSOLIDD_71_... Ctrl click PSOLIDD_267_...; Ctrl click PSOLIDD_268_... Ctrl click PSOLIDD_269_...; click Apply f. Name: Deform_11; click SeatBelt_Shell; click Apply

a

b

a Ribs Shoulder c d

b Torso

d Breast

c Plate Necke

f

e Dummy

f Seatbelt


Create Contact Bodies (continued)a. Name: Deform_12; click PSHELL_22468_...; click Apply b. Name: Deform_13; click PSOLIDD_73_...; Ctrl click PSOLIDD_74_...; Ctrl click PSOLIDD_75_...; Ctrl click PSOLIDD_76_...; Ctrl click PSOLIDD_79_...; click Apply c. Name: Deform_14; click PSHELL_2376_...; Ctrl click PSHELL_2377_...; click Apply d. Name: Deform_15; click PSOLIDD_80_...; Ctrl click PSOLIDD_87_; Ctrl click PSOLIDD_70_; Ctrl click PSOLIDD_71_; click Apply e. Name: Deform_16; click PSOLIDD_65_...; Ctrl click PSOLIDD_72_...; Ctrl click PSOLIDD_93_...; click Apply

a

b

a Chair c d

b Lower Body

d Hands Feet c Frame e

e Body


Modify BCTABLEa. Right click: BCTABLE_1; select Properties b. # NGROUP = 10 c. Click # NGROUP Group 0 : Airbag - Airbag (Imported) (not shown) Group 1 : Pelvis - Leg Bones d. Double click +c19 IDSLAV,1 e. Click and select Deform2_2; click OK f. Click +c19 FRIC,1, enter 0.3 g. Click +c25 METHOD,1, select SS2WAY h. Click +c27 SOFT,1, select 2 i. Click +c29 SFS,1, enter 1; click +c29 SFM,1, enter 1; click +c29 AUTO,1, select Yes j. Double click +c36 IDMA,1 k. Click and select Deform3_3; click OK Continue with Groups 2 through 9 (see the following page) l. Click Modify


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c d

b f

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hi

k

jl


Modify BCTABLE (continued)Contact: Contact Table -> BCTABLEContact airbag Pelvis bonesGROUP IDSLAVE

FRIC

Method ss2way

SOFT

SFS

SFM

AUTO

IDMA

0

1 2

0.3

2

1

1

yes

1 3

1

0.3

ss2way

2

5

5

yes

Ring plate neckRibs torso Ribs breast Airbag dummy seatbelt dummy Dummy chair Dummy frame Airbag Frame

23

54 6 1 11 13 15 1

0.450.3

ss2wayss2way

22

11

11

yesyes

87 9 10 16 12 14 14

4

0.3

ss2way

2

1

1

yes

5

0.3

ss2way

2

1

1

yes

6

0.3

blanks

2

1

1

yes

7

0.3

ss2way

2

1

1

yes

8 9

0.3 0.3

ss2way ss2way

2 2

1 1

1 1

yes yes


Define SPCD2 for Chair-ground-framea. Fields/Tables: Tabled: TABLED1 b. Click Add twice to make two rows c. In Row 1, for X, enter 0.; for Y, enter 0.0; in Row 2, for X, enter 1000.; for Y, enter 0.0 d. Click Create e. Click Exit

a

c b

d

e


Define SPCD2 for Chair-ground-frame (continued)a. Click LBC, select Part BC, select B Presc Motion Rigid b. Right click Part, select Material c. Click [020] MAT_RIGID d. Ctrl click PSHELL_2468_Body_Final.bdf, PSHELL_2377_Body_Final.bdf, PSHELL_2376_Body_Final.bdf e. Click Done f. Click D1, D2, D3, D5, D6, D7 g. Click SPCD2 h. Double click LCID i. Click TABLED_62 62; click OK j. Click Store k. Click Exit l. Click Exit

a b

c

d e l g h f

i

j

k


Initial Dummy Velocitya. Right click LSTC.H3..., click Show Only b. Click LBC, select Nodal BC, click Initial Transient Condition c. Click Define App Region d. Using the mouse, select the complete dummy in the window e. Click XVEL, enter -15 f. Click Create g. Click Exit2

a

b d

c

e f g


Create SimXpert Analysis Filea. In the Model Browser, right click eulerbagconsta....... b. Select Create new Nastran job c. Click Solver Input File d. For File name:, enter Chapter21 e. Click Save f. Click OK g. Observe that there is a Newjob in the Model Browser tree

a

b

c

g

f

d

e


Create SimXpert Analysis File (continued)a. In the Model Browser under Newjob, right click Displacement Output Request and click Delete b. In the Model Browser under Newjob, right click Element Output Request and click Delete c. In the Model Browser under Newjob, right click Loadcase Control and click Properties d. For Ending Time:, enter 40 e. For Number of Time Steps:, enter 20 f. Click Apply

c a

bd e

f


Export the SimXpert Analysis Filea. In the Model Browser under Newjob, right click Newjob b.Click Export

a

b

Analysis Deck CorrectionsThis step becomes obsolete as soon as the following CRs are solved: CR 1-136647181 : BCTABLE issues Airbag-Dummy CR 1-192117741 : Incorrect numbering Seatbelt elements Edit Chapter21.bdf and modify the following values: Row 12 : BCONTACT = 1 1234567$1234567$1234567$1234567$1234567$1234567$1234567$ Row 39833 : CBELT 50001 2470 79297 80456 0 0.0 Row 39834 : CBELT 50002 2470 79267 80457 0 0.0


Run MD Nastran Solvera. Double click the desktop icon b. For the input file, select Chapter21.bdf c. Click Open d. Click Run

b a

c

d


Access the MD Nastran Analysis Results FileAccess the results by attaching the d3plot file.a. File: Attach Results b. Click File Path icon c. Select Chapter21.dytr.d3plot d. Click Open e. Click OK

a b c

e

d

Note: If SimX cant access the results, do the following: File -> Save File -> New File > Attach Results Attach Options: BOTH OK


Access the MD Nastran Analysis Results File (continued)Change the model visualization.a. Right click Model Views; click Right b. Right click on the vertical line (wall); click Hide c. Right click Render; click FE Shaded with Edges d. Click Hide Unreferenced nodes

a

b

c

d


Animate a Deformed PlotCreate a deformed plot with animationa. Results: Deformation b. To select all Result Cases, click ch21a.dytr c. Result type: select Displacement Components d. Click Deformation e. For Deformed display scaling, select True f. For Deformed shape, Render style, select Shaded g. For Deformed shape, Edge color, select cyan h. Click Plot Data i. Click Animate j. Click Update

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d

c ib

j

Updated (Deformed)

hOriginal

f g

e


Animate a Deformed Plot (continued)Animation

a

b

c

d

e

f


Input File(s)File Chapter21.dat Body_Final.bdf eulerbagconstant_new_spiral_simx.bdf LSTC.H3.022908_Beta_RigidFE.50th.dat Description MD Nastran input file for airbag FSI example Frame model Airbag model Dummy model

AnimationClick on the figure below to play the animation, Esc to stop.

Figure 21-2

Deployment of Airbag Animation

occupant safety and airbag deployment

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