analysis of chassis

CADmantra Technologies Pvt. Ltd.

All right reserved @ cadmantra technologies pvt. ltd.

STRUCTURAL ANALYSIS OF A CHASSIS OF

EICHER 11.10 USING “ANSYS”

Bhola Patel

Design Engineer


Contact: [email protected]

ABSTRACT : Automotive chassis is an important part of an automobile. The chassis serves as an frame work

for supporting the body and different parts of the automobile. Also, it should be rigid enough to withstand the

shock, twist, vibration and other stresses. Along with strength, an important consideration in chassis design is to

have adequate bending and torsional stiffness for better handling characteristics. So, strength and stiffness are

two important criteria for the design of the chassis. This report is the work performed towards the optimization

of the automotive chassis with constraints of stiffness, strength and natural frequency. The design improvement

study performed resulted in a maximum torsional stiffness of 6448Nm/deg, an increase of 377% over the

baseline model. A maximum increase in efficiency of 286% to 23g/Nm/deg for a mass of 148.3Kg accompanied

this increase in torsional stiffness. Following optimization of the model to gain minimum mass for a stiffness of

6000Nm/deg a torsional stiffness of 6030Nm/deg was realised for a mass of 127Kg, giving an increase in

efficiency of 322% over the baseline model to 20.99g/Nm/deg.

1. INTRODUCTION Automobile chassis usually refers to the lower body

of the vehicle including the tires, engine, frame,

driveline and suspension. Out of these, the frame

provides necessary support to the vehicle components

placed on it. Also the frame should be strong enough

to withstand shock, twist, vibrations and other

stresses. The chassis frame consists of side members

attached with a series of cross members.

Along with the strength an important consideration in

the chassis design is to increase the stiffness (bending

and torsion) characteristics. Adequate torsional

stiffness is required to have good handling

characteristics. Normally the chassis are designed on

the basis of strength and stiffness. In the conventional

design procedure the design is based on the strength

and emphasis is then given to increase the stiffness of

the chassis, with very little consideration to the

weight of the chassis. One such design procedure

involves the adding of structural cross member to the

existing chassis to increase its torsional stiffness. As

a result weight of the chassis increases. This increase

in weight reduces the fuel efficiency and increases

the cost due to extra material. The design of the

chassis with adequate stiffness, strength and lower

weight provides the motivation for this project.

The goal of the structural design is to obtain

minimum component weight and satisfying

requirements of loads (stresses), stiffness, etc. The

process of producing a best structure having optimum

structural performance is termed as structural

optimization. Structural systems like the chassis can

be easily analyzed for the stress, and stiffness, etc.

using finite element techniques. The limitations on

the stress, strength etc. are the constraints for

optimization.

2. CASE STUDY The four models in this study represent the same

bracket. It is rigidly supported at the back and loaded

with uniform pressure applied to the top of the

hollow cantilever. Each model produces different

results.

3. MODEL

It uses a first-order solid tetrahedral element which,

by design, can only model constant stress within its

volume. Knowing that, there are two big problems.

First, only one element is placed across the thickness

of the plate in bending. This model is not capable of

representing bending stress which changes from

compressive to tensile across the plate thickness.

Consequently, bending stresses are badly represented

by constant stress. The second problem is that the

elements are highly distorted. Each type of element

works well only if it is within specified shape limits.

If element distortion is beyond these limits, then

numerical procedures used to calculate displacements

and stresses return false results.

Figure 1. Results for Model show a maximum Von

Mises stress of 18,000 psi



LOADS ON THE FRAME

The frame experiences loads of different nature

during motion of the vehicle. These loads, in turn,

produce stresses and strains of various kinds.

Generally, the following types of loads are sustained

by the frame.

FLEXURAL (OR BENDING) LOAD

It is produced in a vertical plane of the side members

due to

Dead weight of the vehicle

Weight of the passengers

Engine torque

Braking torque

Flexure load also develops in lateral plane of the side

members due to

road Camber

cornering force

side wind

CALCULATION FOR EICHER E211.10

CHASSIS

Model No. = 11.10 (Eicher E2)

Capacity of Eicher = 8 ton

Capacity of Eicher with 1.25% = 78480 N

Weight of the Eicher = 2 ton

Total Load acting on the Chassis = Capacity of the

Chassis + Weight of Eicher

Calculation of the Deflection for Individual Side

Bar

Mmax = 37526845 N-mm

76.20

203.20

h

b1

b

Moment of Inertia around the X – X axis:-

Ixx = {bh3 – [b1(h)

3]} / 12

= [(76.20 x 203.203) – (66.67 x 184.14

3)] / 12

=18588475.09 mm3

Section of Modules around the X – X axis:-

Zxx = {bh3 – [b1(h)

3]} / 6h

= [(76.20 x 203.203) – (66.67 x 184.14

3)] / (6 x

203.20) = 182957.432 mm3

Basic Bending equation are as follow :=(M / I) = (σ /

y) = (E / R)

Material of the “C” channel:-

Material : St 52

E = 2.10 x 105 N / mm

2

Poisson Ratio = 0.28

Radius of Gyration R = (203.20 / 2)

=101.60 mm

Maximum Bending Moment acting on the Beam: -

Mmax = 37526845 N-mm

I = 18588475.09 mm4

Y = 101.60 mm

CALCULATION FOR TORSIONAL STRESS

GENERATED IN CHASSIS

Reaction generated on Beam at the center of wheel

alignment: - 29430 N

With the consideration of at the rate of angle of twist

= 1˚

θ = (1˚ x π / 180) = 0.017452

By considering the whole system as a one rotational

body as per following data when in twist from its

support.

Width of the chassis: - 800mm

Length of chassis; - 6900mm

Distance between two reaction: - 4900mm

Modulus of rigidity for structural steel: - 80000

N/mm2

Now basic rule for Twisting Moment is:-

(T / J) = (τ / r) = (G x θ / L)

Now equating

(T / J) = (G x θ / L)

For the rotational shaft J is 2 times higher the Mass

Moment of inertia:-

Mass moment of Inertia for Chassis body = 4.65 x

107 mm

4

So, Polar Moment of Inertia J= 2 x I

J= 2 x 4.65 x 107

J= 9.3 x 107

T = (G x θ x J) / L

T = (80000 x 0.017452 x 9.3 x 107) / 6900

T = 18817808.70 N-mm

Torsional stress generated in Chassis body :-

Take width of body as a radius o rotational body r =

800mm

(T / J) = (τ / r)

τ = (T x r) / J

τ = (18817808.70 x 800) / 9.3 x 107

τ = 161.87 N/mm2

4. CONCLUSION

At present time the problem of enhancing safety is

very actual for the world automotive industry and

chassis is the backbone of the automotive system.

Day by day modification has been done in existing

system to increase strength and durability with

minimum possible cost. Here is the one approach

presented.

This project represent to study the stress-distribution

of automobile chassis. When different parts are

mounted o n it at that time no. of stresses are produce

in chassis. First Design stress is calculated then it was

compare with the stress result of Finite element

Analysis report by using pro-Mechanica tool. Its

9.53



comes within the limit So we can say that design is

safe.

5. REFERENCES

[1] Automobile Engineering – Vol.1 -

K.M.Gupta , Umesh Publication – 2001, page no. 54

to 61

[2] Automobile Mechanics , Dr. N. K. Giri,

Khanna Publisher, Delhi-2003, page no. 161 to 164

[3] Technical manual of Eicher E2 11.10,

Apco motors pvt. Ltd., Himmatnagar. Eicher motors

sells & service center.

[4] www.eicherworld.com

[5] Automobile Engineering, Vol.-I by Kirpal

sing, Standard Publisher and Distributor, Delhi-2003.

[6] Optimization of frameworks by means of

FEM use, By J. GADUŠ, Slovak Agricultural

University, Nitra, Slovak Republic, RES. AGR.

ENG., 49, 2003 (1): 32–36

[7] Analysis of Torsional Stiffness and design

improvement study of a Kit Car Chassis Prototype,

by Wesley Linton, M.Sc. THESIS, CRANFIELD

UNIVERSITY,SCHOOL OF INDUSTRIAL AND

MANUFACTURING SCIENCE MOTORSPORT

ENGINEERING AND MANAGEMENT 2001-2

[8] M.Tech. Dissertation “Structural

Optimization of Automotive Chassis” By Roopesh

Shroff, Department of Mechanical Engg. , IIT

,Bombay -Academic year 2002

[9] “Finite element analysis” by – Chandra

Patla.

[10] “Finite element analysis” by – Robert D.

cook