VCS 3D SIMULATIONS

Visual Crash Studio

3D Constructors

Visual Crash Studio-Overview

Macro Elements:

Beams and Joints

Honeycomb barriers:

MDB & ODB

Rigid bodies

New integration

schemes (explicit)

Global scalar and

vector fields

Contact/impact

modeling

SuperJoint Constructor - Modeling concept

Crashing response of joint element

involves interaction of:

• denting

and

• lateral crushing

of thin walled shells “weak response”

and

•beam-like response

of

• joint legs

(“strong response”).

Correctly designed joint should show “strong

response” under assigned crash loading. The NCS

joint module is developed to help engineers design

“strong-response” of joints.

SuperJoint Constructor - The mechanics of SuperJoint Element

Connecting shellConnecting shell

The interaction between “strong” and “weak” response is controlled by parts of the

joint referred to as “connecting shells”

The SuperFolding Elements II are used to model the transition

between joint legs and connecting shells

The SuperFolding Elements II are used to model the transition

between joint legs and connecting shells

SuperJoint Constructor

Constructors of deformable barriers - Overview

VCS implements three deformable barriers according to the following specifications:

MDB FMVSS 214

MDB 96/27/EC

ODB IIHS/EEVC

Visual Crash Studio

Simulation module

Setting up 3D simulation model - Basic procedures

1. Define 3D nodes & fixed b.c. 2. Define SBE 3. Split SBE on longitudinals

4. Add engine mounts (solid cross

section beam)

5. Add rigid bodies: engine and

gearbox

6. Add radiator and barrier nodes

& corresponding b.c.

Setting up 3D simulation model

Basic procedures - rigid bodies options

7. Add radiator and barrier (rigid

boxes)

8. Add nodes of wheel objects. 9. Add wheels (cylinders)

Define global fields contact settings and contact characteristics

Global model fields and general contact

Free fall in gravitation field

Earth gravitation

defined along Z axis

Contact flags of rigid

bodies set to false

Sphere and cylinder

penetrate fixed

parallelepiped

Global model fields and general contact

Intuitive contact definition 1

Contact flags of ALL rigid

bodies set to true

Multiple contacts flag set

to false

Cylinder bounces back

from green box

Sphere penetrates both

rigid bodies

Global model fields and general contact

Intuitive contact definition 2

Contact flags of ALL rigid

bodies set to true

Cylinder bounces back

from green box

Sphere contacts cylinder

and bounces back

Cylinder hits the box

second time

Multiple contacts flag set

to true

Global model fields and general contact

Contact Pairs

Contact pair defines

exclusive contact between

two selected elements

(based on standard law or

user defined characteristic

•2 contact pairs defined:

cylinder-box and sphere-

box. Sphere penetrates

cylinder

•3 contact pairs defined.

Contact detected between

all elements

Setting up 3D simulation model

Contact settings in elementary model of front end

Contact spheres (node window)

and bumper barrier contact

pairs

Contact spheres and wheels

longitudinals contact pairs

Contact spheres (node window)

and bumper barrier contact

pairs

Bumper radiator contact pairs Complete model Results of simulation

Contact/Impact procedures

Contact envelopes

In VCS the default beam contact algorithm

uses the concept of envelopes.

The envelope consists of:

• cylinder and

• sphere

that surrounds one half of the beam element

together with corresponding node. The radius

of the envelope is defined as an average

width of the cross section and can be

modified by the user for specific contact

models.

Setting up 3D simulation model

Contact envelopes for deformable barrier contact

Replace rigid barrier by IIHS (rigid

contact pairs removed automatically)

Set contact envelopes for

deformable barrier contact

Results of central crash test

simulation

Close up on contact area Offset crash scenario Offset crash simulation

Modified explicit integration scheme

Richard Courant and stability condition for linear

p.d.e.

Born: 8 Jan 1888 in Lublinitz, Germany (now Lubliniec, Poland)

Died: 27 Jan 1972 in New Rochelle, New York, USA

LC

oooooo

o

mm

E

llAl

EA

mk

mm

mmk

24421

21

21

Critical time step:

L

o

c

lt

2*

oVtV )0(

Discrete Continuous

oVtV )0(

Modified explicit integration scheme

Stability condition for nonlinear material response and

reversal point analysis.

Perfectly plastic and viscous materials (monotonic loading)

Nonlinear elastic

elastic/plastic material

(monotonic loading,

unloading and reloading)

Perfectly plastic and viscous materials (monotonic loading)

Nonlinear elastic

elastic/plastic material

(monotonic loading,

unloading and reloading)

k

m

Vt

Vt

kmV

E

ukkuF

o

oo

k

22

242

4

*

4

4

4*

2

43

o

o

ooo

o

k

oo

P

Vmt

VtPuP

mV

DE

uPDconstPF

*

**

2

22

const

Vmt

Vtconstuconst

mV

constVF

constVVVVF

o

oo

o

o

*

**

2

22

;

)(

0)(lim *

0

o

VVt

o

)(lim *

0o

VVt

o

)(tV

t

0W

0W*t

oVoVAnalysis of the reversal

point is necessary

Modified explicit integration scheme

Details: kinetic and internal energy of an Element .

,tconstm

Fa

#

2

#

2........)(

........

nodes

o

v

k

nodes

D

vpowerstress

VmdvVVE

dvFddvW

Basic assumption of explicit scheme:

Kinetic and internal energy of an Element

z

yx

z

yx

Kinematics of representative d.o.f. at iteration step

2)(

)(

2attVtu

taVtV

o

o

)(tV

t

0W

0W*t

taVtV o )(o V

Modified explicit integration scheme

Details: energy production and reversal point analysis.

)(tV

t

0W

0W*t

taVtV o )(o V

22

0)(

*

2

*

*

**

oo

o

Vt

a

Vu

a

Vt

tVV

Classic elastic material and Courant condition

22

42

1

2

1

2

:

2

*

2

2*2*

2

2

k

mt

Vtkuk

mV

EcaseLimiting

kuW

oo

k

Discrete version of Courant

stability condition

Note that m is a mass of the

node, u is an incremental

deformation and PI is a

contribution of given d.o.f. to

total potential energy of an

element.

Advanced modeling options

Kinematic constraints and concentrated loadings

Constraints and loadings can be assigned to all d.o.f. in a given group or

to a specific d.o.f. as explained in the table below

• set the same kinematic constraints to all d.o.f.

• set the same kinematic constraints to linear velocities

• set kinematic constraints for y d.o.f.

This procedure is the same for an individual node or a group of nodes.

Constraints and loadings can be assigned to all d.o.f. in a given group or

to a specific d.o.f. as explained in the table below

• set the same kinematic constraints to all d.o.f.

• set the same kinematic constraints to linear velocities

• set kinematic constraints for y d.o.f.

This procedure is the same for an individual node or a group of nodes.

Advanced modeling options - Complex loading histories

0–10 [ms] Bezier function 10–20 [ms] constant velocity 20–30 [ms] linear deceleration0–10 [ms] Bezier function 10–20 [ms] constant velocity 20–30 [ms] linear deceleration