modelling and analysis of body structures …dynamicpublisher.org/gallery/ijsrr-d215.pdf · this...

MODELLING AND ANALYSIS OF BODY

STRUCTURES FOR A

5-DOOR CAR FIROZ KHAN#1, N.AMARA NAGESWARA RAO #2, RAFFI MOHAMMED*3,

Y.VENKATESH*4

#Department of Mechanical Engineering, Nimra College of Engineering & Technology. *Department of Mechanical Engineering, Ramachandra College of Engineering Eluru.

[email protected]

Abstract— A vehicle body structure is the main supporting structure of a motor vehicle to which all other components are

attached, comparable to the skeleton of an organism. The car body structure fatigue damage is mainly caused by the vehicle

dynamic response, which is usually expressed as stress or strain time history. Stress/Strain calculations for fatigue life

estimation can be performed in the time domain or Frequency domain. The detail car body stress analyses with ANSYS were

performed based on 3D Ls-Dyna and mode analysis is also performed here. Modal analysis is usually used to determine the

natural frequencies and mode shapes of car body structure. Vibration and Crash Analysis of Car Body using Ansys is carried

out and including dynamic, static, crash analysis and so on. The main objective of the project is to find fundamental

characteristics like frequency, stress and displacement for different material and velocity influence in the car body structure. If

the fundamental frequency is increased beyond our designable value, if possible engineering changes can be made in the car

body structure. In the car body structure the factor of safety value may be a half of the factor of safety of the existing material.

Car body design can be modelled by using Catia modelling software. Analysis can be analysed by using 3D LS-DYNA.

This project is analysis done on some of the body structure components with different materials and concludes that

these components withstand the loads and sudden impacts without deflection or distortion. The scope of the project involves,

Discretisation of sheet metal components of 5 door Cab body. Creation of LS-Dyna model suitable for safety analysis. Prepare

the Built Report. CATIA V5 is the modelling package used to model the body structure components and LS-DYNA is the

analysis package used to carry out analysis.

Keywords— LS-DYNA, CATIA V5

I. INTRODUCTION

A vehicle body structure is the main supporting structure of a motor vehicle to which all other components are

attached, comparable to the skeleton of an organism. The core element of any car is the body structure. The car body

connects all the different components; it houses the drive train and most importantly carries and protects passengers

and cargo. The body structure needs to be rigid to support weight and stress and to securely tie together all the

components. Furthermore, it must resist and soften the impact of a crash to safely protect the occupants. In addition,

it needs to be as light as possible to optimize fuel economy and performance. Over the years, various designs have

been used and each of them has its benefits and drawbacks. Until the 1930s, virtually every car had a structural

frame, separate from its body. This construction design is known as body-on-frame. Over time, nearly all passenger

cars have migrated to unibody construction, meaning their chassis and bodywork have been integrated into one

another.

The main functions of a body structure in motor vehicles are:

1. To support the vehicle's mechanical components and body

2. To deal with static and dynamic loads, without undue deflection or distortion.

These include:

• Weight of the body, passengers, and cargo loads.

• Vertical and torsional twisting transmitted by going over uneven surfaces.

• Transverse lateral forces caused by road conditions, side wind, and steering the vehicle.

• Torque from the engine and transmission.

• Longitudinal tensile forces from starting and acceleration, as well as compression from braking.

• Sudden impacts from collisions.

International Journal of Scientific Research and Review

Volume 7, Issue 3, 2018

ISSN NO: 2279-543X

http://dynamicpublisher.org/92

This work deals with the crash and modal analysis of a 5-door car for some of the body structures like Dash & Cowl

assembly, Front end structure, Floor, Back Panel assembly.

II. MODELLING OF BODY STRUCTURE PARTS

Components and Sub-assembly Modeled in Catia v5 List of assemblies and the number of sheet metal components modeled in each assembly by using CATIA V5

Assembly Name

Number of

Sheet metal

Parts modeled

DASH & COWL ASY 35

FRT END STRUCTURE 55

PANEL ROOF 7

BODY SIDE 56UNDERBDY FRT FLR 50

UNDERBDY CTR & RR FLR 26

BCK PNL STRUCTURE 10

HOOD 10

DOOR ASY DC FRONT DOOR 40DOOR ASY DC REAR DOOR 37

FENDER FRONT 2

BIP

Closures

1.DASH AND COWL ASSEMBLY

2. FRONT END STRUCTURE



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3. UNDERBODY FRONT FLOOR

4. UNDERBODY CENTER AND REAR FLOOR

5. BACK PANEL STRUCTURE



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III. ANALYSIS OF BODY STRUCTURES

A. INTRODUCTION

LS-DYNA WORKBENCH mode is used which one of the auxiliary modes is provided along with LS-DYNA. The

key features which make LS-DYNA WORKBENCH dominated over conventional classical mode of LS-DYNA are

i. No need to define element type

ii. Less mesh time

iii. Importing complete details of modelling

iv. Less analysis time

v. Ease of use

B. ANALYSIS PROCEDURE

• Save the modeled file that is prepared in CATIA or PRO/E packages to appropriate format that is supported by

ANSYS. ANSYS supports sat, agdb, model, dlv, CATIA Part, CATIA Product, tin, ipt, iam, igs, iges… the models

created in doing this project are saved in stp format.

• Open the ANSYS WORKBENCH mode and select simulation mode. This takes to a simulation mode where model

files can be imported and different analysis can be done on the problem.

• First the material properties are to be defined. For this change the current tab to project and select the current file

and tick the material properties and click on the engineering data icon located just below the standard toolbar. This

opens a new tab named engineering data. Enter the required properties of the material. Here lies a material library in

which some standard materials are saved with their properties. These parameters can be exported or can be directly

entered.

• Now change the tab to simulation tab. Select geometry icon in the toolbar and export the model file saved in

appropriate format. This imports the modeling file into the simulation mode. Now check whether the geometry is

ticked or not to ensure that all the modeling properties are imported or not.

• By importing geometry, the new branch named mesh is automatically displayed in the tree located left. By right

clicking on mesh, size of mesh can be defined. In this analysis the size of mesh is defined as 0.01mt. To generate

mesh right click on mesh and click on generate mesh.



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C. MESHING SHOWN FOR BODY STRUCTURE PARTS

IV. RESULTS AND DISSCUSSIONS

A. Assumptions

• Adhesive lines missing the link surfaces in hood are not modelled.

• Hinge is modelled using low torsional stiffness beam.

• Closure Lock is modelled using rigid due to non-availability of the detailed latch mechanism.

• Clinches, MIG welding and Bolts are modelled using rigid.

• Floor mounting bush is assumed to be rigid. Rigid elements are connected to the components the bush is

welded. The bush mass is represented using mass element

• The node representing bush mass is constrained in Z-direction in explicit.

• Contact tied is modelled between spot weld / adhesive hexa element nodes and the components. Automatic

single surface contact is defined between the components



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B. Node and Element Numbering Schema

Start End Start End

DASH & COWL ASY 1100000 1160286 1100000 1159825 60287 59826FRT END STRUCTURE 1200000 1257902 1200000 1255815 57903 55816

PANEL ROOF 1300000 1353187 1300000 1352172 46673 45639

BODY SIDE 1400000 1580388 1400000 1574440 180389 174441

UNDERBDY FRT FLR 1600000 1715865 1600000 1712894 115865 112895

Mass Element for FRT FLR 1799998 1799999 1799998 1799999 2 2UNDERBDY CTR & RR FLR 1800000 1862725 1800000 1861226 62726 61227

Mass Element for RR FLR 1899998 1899999 1899998 1899999 2 2

BCK PNL STRUCTURE 1900000 1927321 1900000 1926848 27322 26849551169 536697Total in BIP

BIP Numbering SchemaNumber of

nodesNo of

elementsNODE ELEMENT

C. Element Quality Check Summary

C. Element Quality Distribution

BIPQuality Check

Min

Siz

e

Ma

x Si

ze

Asp

ect

Ra

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Max

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An

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Min

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uad

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Jaco

bia

n

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n %

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.7

% o

f T

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s

DASH & COWL ASY 4.0 13.8 2.6 15.0 135.0 45.0 118.0 30.0 0.60 0.44 9.48

FRT END STRUCTURE 4.0 12.0 2.3 15.0 135.0 45.0 114.1 30.0 0.60 0.37 8.00

PANEL ROOF 4.0 12.0 2.2 14.9 135.0 45.0 109.8 30.0 0.60 0.25 1.10

BODY SIDE 4.0 18.8 2.4 15.0 135.0 45.0 115.1 30.0 0.55 0.91 4.10

UNDERBDY FRT FLR 4.0 13.7 2.4 15.0 135.0 45.0 116.6 30.0 0.62 0.02 4.40

UNDERBDY CTR & RR FLR 4.0 12.0 2.3 15.0 135.0 45.2 111.8 30.0 0.52 0.84 4.50

BCK PNL STRUCTURE 4.0 15.1 2.2 15.0 135.0 45.0 117.4 30.0 0.60 0.47 4.20



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D. Modal Analysis for Integrity Check



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V. CONCLUSION

By conducting analysis on different body structure parts it can be concluded that the stresses induced in all the structures are

within their allowable limits.

Modal analysis of Mode Shape Frequency is 410.44Hz with decreasing the Dof Mode Shape Analysis Frequency is 116.046 Hz.

Doff Seventh Mode Shape Analysis Frequency is 417.26 Hz is increasing their modal and its equal to before impact of the

vehicle. And also Crash analysis for simulations is 70 km/hr after impact

REFERENCES

1. Ashby, M.F., On Engineering Properties of Materials, Acta Metall., 37, 1273, 1989.

2. L. Mei, C.-A. Thole, Data analysis for parallel car-crash simulation results and model optimization, Sim. Modelling

Practice and Theory16 (3) (2008) 329–337. doi:10.1016/j. simpat. 2007.11.018.

3. C. A. Thole, L. Nikitina, I. Nikitin, T. Clees, Advanced mode analysis for crash simulation results, in: Proc. 9th LS-

DYNA Forum, 2010.

4. J. A. Lee, M. Verleysen, Nonlinear dimensionality reduction, Springer, 2007

5. B. Peherstorfer, D. P fluger, H.-J. Bungartz, A sparse-grid-based out-of-sample extension for dimensionality reduction

and clustering with laplacian Eigen maps, in: D. Wang, M. Reynolds (Eds.), AI 2011: Adv. Artificial Intell., Vol. 7106

of LNCS, Springer, 2011, pp.112–121

6. S. Lloyd, Least squares quantization in pcm, IEEE Trans. Information Theory 28 (2) (1982) 129–

137.doi:10.1109/TIT.1982.1056489.

7. Vehicle Crash Worthiness and Occupant Protection by Paul Du Bois Clifford C. Chou Bahig B. Fileta, Tawfik B.

Khalil, Albert I. King, Hikmat by F. Mahmood, Harold J. Mertz, Jac Wismans.

8. CATIA Manual, Engineers Cadd Centre Pvt.Ltd.,

9. http://en.wikipedia.org/wiki/LS-DYNA

10. http://www.cybersteering.com/cbmain/utilcars/qualis_gs.html

11. http://en.wikipedia.org/wiki/Body Structures

12. http://en.wikipedia.org/wiki/CATIA



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