Crash Analysis trends in the Automotive Industry

Dilip Bhalsod2017 3rd China LS-DYNA User’s conference

1

Vehicle models in 1986

3500 elements

2

3

Model size today

small overlap

• Total number of elements: 17 200 000• Simulation time: 250ms • Number of CPU’s: 480• Run time: 84h• Number of elements reduced from 19 400 000 (two

complete cars) due to memory issues.

Cores per job trend

1 core

480 cores

Numbers of cores per jobIncrease ~20% yearly

1986 2017

4

Crash model size Increase trend

Model size increase ~30% yearly

3500 elementsIn 1986

14 millionelements today

1986 2017

5

Today’s challenges

Airbags, material failure, spotweld failureDeformable wheel rims, deflation of tires,Glass failure, dummies, suspension parts breakable

6

Required for Validation through CAE

• Accurate material models

• Failure in materials

– Plastics, metal, glass

• Accurate modeling of tires, material failure in tire models

• Suspension links, sub-frame need to consider breaking parts

• Spotweld failure modeling very critical

7

Required for Validation through CAE

• Accurate dummy modeling

– Human body modeling

• Airbag modeling

– Driver, passenger, knee, head-thorax, curtain

• Deformable barrier modeling

8

9

Challenges of todays crash models

Challenges of todays crash models

• Typical crash models now range between 5 to 15 million elements

• 96 -256 cpus per job

• Common mesh for Crash, NVH and Durability analysis

• Possible to move from mpp-lsdyna to hybrid-lsdyna to improve job turnaround times.

• Ford study of 100 million element model revealed issues– for pre-processing , solver and post-processing

– More than 100 Gb memory needed to load 100 million element model

– Fringing of plastic strain took several hours

• Use of different unit system by different departments within a company results in confusion and time loss

10

Challenges of todays crash models

• Material Fracture• Sensing• Restraint system modeling• Positioning seats for different load cases• Friction between parts• Connectors

– BOLTS, SPR, SPOTWELD, MIG WELD

• Sled creation– Pulse convert from full vehicle– Restraint modeling

• Automated Bolt Modeling (with Pre-stress)• OneStep Forming (Manufacturing data)

11

Challenges of todays crash models

• Chassis modeling– Knuckle, ball joints, control arms

• Electrical cables• Windscreen• Active hood• Ped pro zones mapping• Occupant injury report• HAZ modeling• Strain mapping on fuel tanks from manufacturing

process• Fabric Tearing and package tear in OOP

12

Material Models

29 in 1986

Over 300 material modelstoday to capture accurate modeling of materials

2017

13

LSTC family of Dummies and barriers

ECER95shell

IIHSshell/solid

ODBshell/hybrid

214shell/solid

AE-MDBshellRCAR Barrier RMDB MCB rigid PDB barrier

LSTC PDB Model Validation for Global NCAP

Progressive Deformable Barrier

Rigid curved barrier model forFMVSS 301

16

Laminated glass modeling

• Accurate modeling of glass critical for:– Pedestrian protection

– Roof crush

– FMVSS 208

*MAT_280/*MAT_GLASS

17

Combined FEA + IGA – Accurate geometry

Talk 6.2 Current Status of LS-DYNA® Iso-geometric Analysis in Crash Simulation Y. Chen, S-P. Lin, O. Faruque, J. Alanoly, M. El-Essawi, R. Baskaran

Accurate airbag modeling

• Driver, passenger, side, curtain, knee....– Airbag folding

– Uniform pressure or CPM method

– Accurate venting methods

• Vent holes

• Porosity

• Adaptive vents

• Pushout vents

19

20

Airbag Folding Process Demonstration- Courtesy of Autoliv

Simulation Folding

21

Curtain bag roll folding

Driver side airbag folding

Simulation Folding – packaging curtain airbag

22

Simulation Folding –Encapsulating airbag

23

New airbag venting methodsPush out vent

24

New Method to capture Accurate Bag Kinematics

Current method IAIR=2

New method IAIR=4

Airbag deformed shapes at 42 ms

Courtesy of Autoliv

Chambers did not get filled in time

Improved airbag deployment

27

Multi-Physics

FEM

SPHALE Particle GasDEM

Coupled Multi-Physics Solver

ICFD The Driver benchmark is part of the QA

Designed by TUM, Inst. For Aerodynamics. The objective is to perform automotive aerodynamics validation. It is a generic reference model with a modern car geometry. There is wind tunnel experimental data for comparison. LS-DYNA provides

excellent agreement with the experimental data.

Configuration used in the study F_D_wM_wW. Fastback_Detailed underbody_with Mirrors_with Wheels

ICFD DEM coupling

Mud and Snow Deposition. Potential applications include drug delivery, erosion of river bed and FSI using particle

bonding capabilities

DEM with capillary force coupled to a turbulent flow

Electric vehiclesEM - New battery module

Lithium-Ioncell

What happens to batteries in a crash- short circuit and heat generation

31

Mapping forming effects Automation flow

Vehicle Model

Choose parts to be stamped

Prepare Onestep Model

Include results to map data into crash Analysis model

Run LSDYNA

32

Crash models

• Automotive companies focus on building

body models and using supplier provided

models like:– Airbag and streering wheel assembly

– Seat models

– Steering column

– Instrument panel

• With this approach subsystems are

validated by suppliers.

33

34

ImplicitLS-OPTLS-TaSC

Human Body Modeling

Implicit Roof Crush

• No speed up• Robust• Comparable to explicit

Satish Pathy and Thomas Borrvall,”Quasi-Static Simulations using Implicit LS-DYNA” 35

LS-OPT MDO: Vehicle Crash and Body Dynamics

6 Crash Modes + Body Dynamics Mode:

- approximately 3 million element models

Allen Sheldon, Ed Helwig (Honda R&D)

36

𝑣0 = 0.3 𝑚𝑚𝑚𝑠

1.LC

2.LC𝑣0 = 0.3 𝑚𝑚𝑚𝑠

Shape optimizationLS-TaSC Example: Bottle opener

Starting design and load cases

Material: plastic

Desired mass fraction 0.4

Geometry Constraint Extrusion

37

1st Principal Stress

Shape optimizationLS-TaSC Example: Bottle opener

Results

From Initial Design to Optimized Structure (density distribution)

Iso-surface

Start from solid

End with mass optimized shape

38

Human body models

Today’s research interestinterests in the automotive industry

A number of companies are activelyworking in this area

39

40