Pick-up Truck Frontal Crash

Chapter 32: Pick-up Truck Frontal Crash

32

Pick-up Truck Frontal Crash



Summary



Introduction



Requested Solutions



FEM Solution



Results



Input File(s)

512 513

513

515 515

513

512 MD Demonstration Problems CHAPTER 32

Summary Title Geometry

Material properties

Chapter 32: Pick-up Truck Frontal Crash Width= 1,954 mm Length= 5,454 mm Height= 1,841 mm

Three different material types are used: • Elastic material: MAT1 • Elasto-plastic material: MATD024 • Rigid material: MATD020 Almost all structures are made by elasto-plastic material (Young’s modulus) = 2.1e+5. N/mm2  (Poisson’s ratio) = .3 E

(density) = 7.89e-9 tonne/mm3  pu (ultimate plastic strain) = .9 

Analysis type

Transient explicit dynamic analysis

Boundary conditions

Fixed condition of the rigid wall

Applied loads

Initial velocity of 5000 mm/sec. defined for the pick-up truck

Element type

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

FE results

t = 90 ms

CHAPTER 32 513 Pick-up Truck Frontal Crash

Introduction Auto companies perform crash tests simulation to increase safety of the vehicles and comply with government regulations such as those of FMVSS (Federal Motor Vehicle Safety Standards). This is an example of a pick-up truck frontal crash at 15 m/s (34 m.p.h.) against a rigid wall. To model the simulation, contact was defined between the truck and the rigid wall to predict the stress and deformations of the structure.

Requested Solutions A numerical analysis will be performed to find the behavior of a pick-up truck during crash simulation.

FEM Solution Three contacts are defined in the simulation: 1. The truck and rigid wall surface 2. The truck tires and the ground surface 3. Self contact for the truck to avoid penetration among various components SET is an executive control entry in SOL 700 that defines a set that contains some grid points. The set will later be referred by the CSPOT entry in the bulk entry section.

SET ..

990009

=

105843

105655

TSTEPNL describes the number of Time Steps (10) and Time Increment (9.e-3 sec.) of the simulation. End time is the product of the two entries. Notice here, the Time Increment is only for the first step. The actual number of Time Increments and the exact value of the Time Steps are determined by SOL 700 during the analysis. The step size of the output files is determined by the Time Increment as well.

TSTEPNL 20

10

9e-3

1

5

To define a 3-D contact region, BCPROP and PSURF are used. BCPROP and PSURF specify a contact body by element properties and element IDs, respectively. BCPROP .. BSURF ..

1

1

2

3

4

10

11

12

5

5

6

7

8

9

10

11

105038

105039

Concentrated masses are defined by CONM2 entry. CONM2

1990624 91344

1e-06

Rigid nodes which are attached to a reference node are defined by RBE2 entry. RBE2 ..

5

104247

123456

104272

104614

104615

Applied forces and motions in the model are gravitational force and the initial velocity on the truck.

514 MD Demonstration Problems CHAPTER 32

GRAV defines acceleration vectors for gravity or other acceleration loading.

GRAV

3

0

9806.

0.

0.

-1.

Initial velocity of the pick-up truck is given. All nodes of the truck have an initial velocity specified by the TIC entry. TIC defines values for the initial conditions of variables used in structural transient analysis. Both displacement and velocity values may be specified at independent degrees of freedom. TIC

1

1

1

15000.

Boundary conditions are limited to the rigid wall and ground. All nodes of the rigid wall and the ground have been constrained in all the degree of freedom. SPC1

1

123456

990803

THRU

991384

Spot weld definition is used at several points. CSPOT is used to define spot-weld with several types of failure criteria. Normal force criterion at failure (1.e+8 N) is applied to the spot weld entry. The number of a specific SET defined in the executive control section is referred in the entry. CSPOT

990009

990009 1e+08

.. MATD20M is used to merge MATD020 rigid bodies into one assembly for SOL 700 only.

MATD20M 181 ..

180

221

182

183

RBJOINT defines a Joint between two rigid bodies. This entry supports 14 different types of rigid joint. This analysis has two different types of rigid joint. REVOLUTE type describes the revolute joint type which allows only axial rotation with other degrees of freedom fixed. UNIVERS type describes the universal joint type which allows all rotational

degrees of freedom with all translational degrees of freedom fixed.

CHAPTER 32 515 Pick-up Truck Frontal Crash

Results t = 0 ms

t = 25 ms

t = 50 ms

t = 75 ms

t = 90 ms

Figure 32-1

Deformation History

Input File(s) File

Description

nug_32a.dat

MD Nastran main analysis input file

nug_32b.dat

Pick-up truck model file

nug_32c.dat

Definition of rigid connection file