Occupant Safety And Airbag Deployment

Chapter 21: Occupant Safety and Airbag Deployment

21

Occupant Safety and Airbag Deployment 

Summary



Introduction



Requested Solutions



FEM Solution



Results



Pre- and Postprocess with SimXpert



Input File(s)



Animation

375 376 376

376

379

418 418

380

CHAPTER 21 375 Occupant Safety and Airbag Deployment

Summary Title

Chapter 21: Occupant Safety and Airbag Deployment

Features

Airbag Deployment with Occupant

Geometry

Material properties

Unit dimensions: mm, kg, ms, KN, GPa, K, J

Car frame:

Rigid

Airbag:

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.

Dummy:

Hybrid 3 - 50 (LSTC.H3.022908_Beta_Rigid.50th

Seatbelt:

fabric (MATD034) and seatbelt material (MATDB01)

Analysis type

Transient explicit dynamic analysis (SOL 700)

Boundary conditions

Fixed except an airbag and a dummy

Applied loads

Initial velocity 15 mm/ms to a dummy. Prescribed Mass Flow Rate and Temperature of Inflator Gas

Element type

1-D beam element, 2-D shell element, 3-D solid element

FE results

Plots of deformed shapes at various steps.

376 MD Demonstration Problems CHAPTER 21

Introduction Automotive 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 Solutions A numerical analysis will be performed to predict the behavior of an airbag and an occupant dummy during crash simulation.

FEM Solution The 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 the INFLATOR key word.

AIRBAG + + + + + + + + +

3 CFD

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

20.

20.

286.98 2

1004.

1004. 1191.

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

20. 1.

CHAPTER 21 377 Occupant Safety and Airbag Deployment

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

8.76E-7

0.3

0.2

0.04 0.35 3.

0.06

0.1

0.4

0.0

0.0

0.0

0.0 1. 0.0

0.0 292

1.E-6

0.0

0.0 0.0 2.9

2.9

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

1.E-6

61

62

3.

61 0.0 4.2

0.0 0.45

0.05

1.7

0.5

6.7 7.6

1.00

8.2

0.0

0.0

1.00

8.2

62

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 Bodies BCTABLE 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+

378 MD Demonstration Problems CHAPTER 21

+ + + ..

20. 1. MASTERS

1.

YES+

6

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

2

1

2

3

6 2527

1 THRU

THRU 10922

2516

4

7

.. Using the BCTABLE and several BCBODY, BCSEG, and BCSURF entries, the following contacts are defined as: Contact Number

Slave

Master

1

Airbag

Airbag

2

Pelvis

Connection bones to legs

3

Neck ring

Neck

4

Ribs

Torso

5

Ribs

Breast

6

Airbag

Dummy upper parts

7

Seatbelt

Torso - lower body - neck

8

Lower body

Chair

9

Feet - hands

Frame

Airbag

Frame

10

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.

CHAPTER 21 379 Occupant Safety and Airbag Deployment

SPCD2 SPCD2 TABLED1 555 + 0.

6 6

RIGID RIGID 0.

MR289 MR289 1000.

6 7 0.

0 0 ENDT

Results

Figure 21-1

Occupant and Airbag at Various Positions

555 555

1. 1.

380 MD Demonstration Problems CHAPTER 21

Pre- and Postprocess with SimXpert In 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

CHAPTER 21 381 Occupant Safety and Airbag Deployment

Specify the Model Units a. 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

382 MD Demonstration Problems CHAPTER 21

Specify Input/Output a. 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

d

b c

a

e

g f

h

CHAPTER 21 383 Occupant Safety and Airbag Deployment

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

a

b

c d

e

384 MD Demonstration Problems CHAPTER 21

Import the Airbag Model a. 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

d a

e

b

f g

h

CHAPTER 21 385 Occupant Safety and Airbag Deployment

Check the Airbag Data To 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

a b

c

c

c

c

d

386 MD Demonstration Problems CHAPTER 21

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

a b

c

d

CHAPTER 21 387 Occupant Safety and Airbag Deployment

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

a c

b

d

388 MD Demonstration Problems CHAPTER 21

Import Car Frame Model a. 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

CHAPTER 21 389 Occupant Safety and Airbag Deployment

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

390 MD Demonstration Problems CHAPTER 21

Dummy Positioning a. 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

c

b

e

CHAPTER 21 391 Occupant Safety and Airbag Deployment

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

392 MD Demonstration Problems CHAPTER 21

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

d

e

f

g

g

CHAPTER 21 393 Occupant Safety and Airbag Deployment

Create Seat Belt Plot 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

394 MD Demonstration Problems CHAPTER 21

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

h c d

g e

i

j

CHAPTER 21 395 Occupant Safety and Airbag Deployment

Check Seat Belt: Shell Property Create 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

396 MD Demonstration Problems CHAPTER 21

Check Seat Belt: 1D Element Property Create 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 e

f

CHAPTER 21 397 Occupant Safety and Airbag Deployment

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

398 MD Demonstration Problems CHAPTER 21

a e

b

g

h

c g

d

f

i k

j k

CHAPTER 21 399 Occupant Safety and Airbag Deployment

Delete Imported Simulation Data and Some Incorrect Contact Definitions a. 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

400 MD Demonstration Problems CHAPTER 21

Check Duplicate ID’s a. Tools: ID Management b.Select Duplicate ID Manager c. Click OK

a

b

c

CHAPTER 21 401 Occupant Safety and Airbag Deployment

Create Contact Bodies a. 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

c

b

b Pelvis

c Axes

d

e

e Ring Neck d Ribs

402 MD Demonstration Problems CHAPTER 21

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

b Torso

a Ribs Shoulder c

d

d Breast

c Plate Neck e

e Dummy

f

f Seatbelt

CHAPTER 21 403 Occupant Safety and Airbag Deployment

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

b Lower Body

a Chair c

d

d Hands Feet c Frame e

e Body

404 MD Demonstration Problems CHAPTER 21

Modify BCTABLE a. 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

CHAPTER 21 405 Occupant Safety and Airbag Deployment

a

c

b

d

e

f

g

h i

k

j l

406 MD Demonstration Problems CHAPTER 21

Modify BCTABLE (continued) Contact: Contact Table -> BCTABLE Contact

GROUP

IDSLAVE

FRIC

Method

SOFT

SFS

SFM

AUTO

IDMA

airbag

0

1

0.3

ss2way

2

1

1

yes

1

Pelvis bones

1

2

0.3

ss2way

2

5

5

yes

3

Ring plate neck

2

5

0.45

ss2way

2

1

1

yes

8

Ribs torso

3

4

0.3

ss2way

2

1

1

yes

7

Ribs breast

4

6

0.3

ss2way

2

1

1

yes

9

Airbag dummy

5

1

0.3

ss2way

2

1

1

yes

10

seatbelt dummy

6

11

0.3

blanks

2

1

1

yes

16

Dummy chair

7

13

0.3

ss2way

2

1

1

yes

12

Dummy frame

8

15

0.3

ss2way

2

1

1

yes

14

Airbag Frame

9

1

0.3

ss2way

2

1

1

yes

14

CHAPTER 21 407 Occupant Safety and Airbag Deployment

Define SPCD2 for Chair-ground-frame a. 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

408 MD Demonstration Problems CHAPTER 21

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 f

e l g

i

h

j

k

CHAPTER 21 409 Occupant Safety and Airbag Deployment

Initial Dummy Velocity a. 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

410 MD Demonstration Problems CHAPTER 21

Create SimXpert Analysis File a. 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

CHAPTER 21 411 Occupant Safety and Airbag Deployment

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

b d e

f

412 MD Demonstration Problems CHAPTER 21

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

a

b

Analysis Deck Corrections This step becomes obsolete as soon as the following CR’s 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

CHAPTER 21 413 Occupant Safety and Airbag Deployment

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

b a

c

d

414 MD Demonstration Problems CHAPTER 21

Access the MD Nastran Analysis Results File Access 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 can’t access the results, do the following: File -> Save File -> New File –> Attach Results Attach Options: BOTH OK

CHAPTER 21 415 Occupant Safety and Airbag Deployment

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

416 MD Demonstration Problems CHAPTER 21

Animate a Deformed Plot Create a deformed plot with animation a. 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

a

d

c i

j

b

Updated (Deformed)

h Original

f g

e

CHAPTER 21 417 Occupant Safety and Airbag Deployment

Animate a Deformed Plot (continued) Animation

a

b

c

d

e

f

418 MD Demonstration Problems CHAPTER 21

Input File(s) File

Description

Chapter21.dat

MD Nastran input file for airbag FSI example

Body_Final.bdf

Frame model

eulerbagconstant_new_spiral_simx.bdf

Airbag model

LSTC.H3.022908_Beta_RigidFE.50th.dat

Dummy model

Animation Click on the figure below to play the animation, Esc to stop.

Figure 21-2

Deployment of Airbag Animation