ijetae_0214_40

International Journal of Emerging Technology and Advanced Engineering

Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 2, February 2014)

253

Structural Analysis of Ladder Chassis for Higher Strength Abhishek Singh

1, Vishal Soni

2, Aditya Singh

3

1PG student,

2Assistant Prof., Dept. of Mechanical Engineering, Oriental Institute of Science & Technology, Bhopal-462021,

India

3UG student, Dept. of Mech. Engineering, Shri Ram College of Engg & Management, Gwalior-476444, India

Abstract— Automotive chassis is an important part of an

automobile. It forms the bones of a vehicle. The chassis

serves as a frame work for supporting the body and

different parts of the automobile, it should be rigid enough

to withstand the shock, twist, vibration and other stresses &

its principle function is to carry the maximum load for all

designed operating condition safely. An important

consideration in chassis design is to have adequate bending

stiffness along with strength for better handling

characteristics. Therefore, maximum shear stress and

deflection are important criteria for the chassis design. This

paper describes Structural analysis & optimization of

vehicle chassis with constraints of maximum shear stress

and deflection of chassis under maximum load. In the

present work, we have taken higher strength as the main

issue, so the dimensions of an existing vehicle chassis of a

TATA LP 912 Diesel BS4 bus is taken for analysis with

materials namely Steel alloy (Austenitic) subjected to the

same load. The four different vehicle chassis have been

modeled by considering four different cross-sections.

Namely C, I, Rectangular Box (Hollow) and Rectangular

Box (Intermediate) type cross sections. For validation the

design is done by applying the vertical loads acting on the

horizontal different cross sections.

Software used in this work Pro e 4.0 & Altair

Hyperworks 11.0.0.39 (Hypermesh).

Keywords— Vehicle chassis, Static analysis, Steel alloy

(Austenitic), C, I, Rectangular Box (Hollow) and

Rectangular Box (Intermediate) type cross sections.

I. INTRODUCTION

Automotive chassis is a frame just like skeletal on

which various machine parts like engine, tires, axle

assemblies, brakes, steering etc. are bolted. It gives

strength and stability to the vehicle under different

conditions. Frames provide strength as well as flexibility

to the automobile. Automotive chassis is the supporting

frame like backbone of any automobile to which the body

of an engine, axle assemblies are affixed. Tie bars, which

are essential parts of frames, are fasteners that bind

different automotive parts together. Automotive frames

are generally manufactured from steel alloys. Frame

holds the body and motor of an automotive vehicle.

According to the structure of chassis, the body of a

vehicle is flexibly molded at the time of manufacturing.

Automobile chassis is generally made of light sheet

metal. It provides strength needed for supporting

vehicular components and payload placed over it.

Chassis of Automotive or automobile helps keep an

automobile rigid, stiff and unbending. Automobile

chassis ensures less noise, vibrations and harshness

throughout the automobile.

The different types of automobile chassis are as

follows:

A. Ladder Chassis:

Ladder chassis is one of the oldest forms of

automotive chassis these are still used in most of the

SUVs today. It is clear from its name that ladder chassis

resembles a shape of a ladder having two longitudinal

rails inter linked by lateral and cross braces.

Fig 1: Model of C cross section type of ladder chassis

B. Monocoque Chassis:

Monocoque Chassis is a one-piece structure it is

overall shape of a vehicle. Such type of automotive

chassis is manufactured by welding floor pan and other

pieces together. Therefore monocoque chassis is cost

effective and suitable for robotized production, now a

day most of the vehicles make use of steel plated

monocoque chassis.

C. Backbone Chassis:

In Backbone chassis it has a rectangular tube type

backbone, which is usually made up of glass fiber that is

used for joining front and rear axle together. This type of

automotive chassis or automobile chassis is strong and

powerful enough to provide support it is used in smaller

sports car. Backbone chassis is easy to manufacture and

also cost effective.



254

II. LITERATURE REVIEW

Roslan Abd Rahman: does stress analysis on heavy

duty truck chassis by finite element package ABAQUS.

To improve the fatigue life of components at critical

point by design modifications the stresses can be reduces.

He uses ASTM low alloy steel a 710 C (Class 3) with

552 MPa of yield strength and 620 MPa of tensile

strength for chassis founds the maximum stress 386.9

MPa at critical point occurred at opening of chassis. This

critical point is located at element 86104 and node 16045,

which was in contacted with the bolt from it he

concludes, that this critical point is an initial to probable

failure.

Cicek Karaoglu: does stress analysis of heavy duty

truck chassis with riveted joints by using a finite element

package ANSYS version 5.3. He examine the effect of

the side member thickness and connection plate thickness

with length change, the thickness of the side member is

varied from 8 to 12 mm, and the thickness of the

connection plate is also varied by local plate from 8 to 12

mm, the connection plate thickness is varied from 7 to 10

mm, and the length of the connection plate (L) is varied

from 390 to 430 mm during his study. From it he

concluded that if it is not possible to change the side

member thickness using local plates, because of increase

in weight of chassis then choosing an optimum

connection plate length (L) seems to be best practical

solutions for decreasing the stress values.

Mohd Azizi Muhammad Nor: determine the stress

analysis of an actual low loader structure having I-beams

design application of 35 ton trailer. He uses CATIA

V5R18 for modeling. Analysis results show that the

location of maximum deflection and maximum stress

agrees with theoretical maximum location of simple

beam under uniform loading distribution. This shows that

there is discrepancy between the theoretical (2-D) and

numerical (3-D FEA) results. It shows that the maximum

deflection is pointed in situated in between BC1 and BC2

with magnitude of 7.79mm. The results show the

numerical analysis revealed that the location of

maximum deflection and maximum stress agrees well

with theoretical maximum location of simple beam

loaded by uniform force.

N.K. Ingole: make the modifications in existing model

of tractor trailer chassis by 1) Variation in cross members

in there Cross sectional areas, 2) Variation in cross and

longitudinal members in there cross sectional areas, 3)

Variation in cross and longitudinal members in there

cross sectional areas and 4) Changing the position of

cross members of main frames of chassis, Considering

variable cross sectional areas of cross and longitudinal

members. It was found that, maximum stress present in

existing chassis was 75 MPa and weight of chassis was

751.82 kg. Case 4 leads to reduction in weight of approx.

112 kg as compared to case 1, 2 and 3. So that the

modifications as per case 4 are also recommended, case 3

the weight reduction is 88 kg with maximum stress level

in range of 25MPa to 66 MPa.

III. PROBLEM STATEMENT

In present the Ladder chassis which are uses for

making buses and trucks are C and I cross section type,

which are made of Steel alloy (Austenitic). In India no of

passengers travel in the bus is not uniform, excess

passengers are travelling in the buses daily due to which

there are always possibilities of being failure/fracture in

the chassis/frame. Therefore Chassis with high strength

cross section is needed to minimize the failures including

factor of safety in design. Basically C cross section type

of chassis is used in buses and I cross section type in

heavy trucks where high strength is required. So we have

taken Rectangular Box type cross section for making

ladder chassis by fabricating it which is used in small

trucks. It will give best strength among all above three.

Another type of cross section we have taken is also

rectangular box type section but it is filled diagonally so

that this type of intermediate structure can increase the

strength of chassis.

The problem to be dealt with for this dissertation

work is to Design and Analyses using suitable CAE

software for ladder chassis.

IV. OBJECTIVES

The aim of this work is to achieve good strength

of automotive ladder chassis, so engineering solution to

the component addressing functionality during the

service life of the component. The component should

withstand all the forces acting on it without rupture or

failure or undue deformation that might render the

component incapable during its service life because of a

mishap due to sudden failure during operation.

An attempt to evolve an improved design resisting the

failure and in turn enhancing the life would be the

objective for this dissertation work. The key objectives

for this work:

1) Identify and study using software tools (for

simulation/ analysis), the nature and

characteristics of stresses acting on the

component.

2) Evaluate the influence of the loads/ mass/

geometry/ boundary conditions over the nature and

extend of stresses.

3) Review the existing design and consider

improvement for negating the harmful influences

of undue stresses.



255

V. METHODOLOGY

A finite element stress analysis need to be carried out

at the failure region to determine the stress distribution

and possible design improvement. Since suitable

software like ProE, Catia, Solid Works, Unigraphics, etc.

are normally utilized for creating the geometry of the

component (3D model). The design verification can be

achieved without elaborate need for prototypes at each

phase saving time and effort. A final prototype for the

final design review can be employed for verifying the

analytical results.

Specification of Ladder chassis:

Wheel Base (WB) = 4920 mm

Rear Overhang (ROH) = 2700 mm

Front Overhang (FOH) = 1275/1430 mm

Gross Vehicle Weight (GVW) = 9000 kg = 9 ton

Length = 8897 mm

Width = 2200 mm

Specification of Material (Steel alloy -Austenitic):

Mass density = 7.86 g/cm3

Yield strength = 207 MPa

Ultimate Tensile Strength = 345 MPa

Young’s Modulus = 220 GPa

Poisson’s ratio = 0.275

Shear Modulus = 86.2745 Gpa

Basic Calculation for Chassis:

Weight of passengers = Weight per passenger × No. of

passengers

= 75kg × 51

= 3825 kg = 3.825 ton

Total load acting on chassis

= Gross vehicle weight + Weight of

passengers

= 9000 kg + 3825 kg = 12825 kg

= 9 ton + 3.825 ton = 12.825 ton

Chassis has two longitudinal members so load will be

acted upon these two longitudinal members. Therefore,

load acting on each member will be half of the total load

acting on chassis.

Load acting on one longitudinal member = 12.825

ton ÷ 2

= 6.288

ton

Fig 2: CAD Model of C cross section type of ladder chassis

Fig 3: CAD Model of I cross section type of ladder chassis

Fig 4: CAD Model of Rectangular Box (Hollow) cross section type

of ladder chassis

Fig 5: CAD Model of Rectangular Box (Intermediate) cross section

type of ladder chassis



256

A). Analytical Method:

The analytical/ computational approach offers results

through simulation/ analyses for the case study

predefined for the solver. The technique would deploy

any of the following software tools: Ansys, Hyper mesh,

Nastran, Abaqus, Radioss or any compatible CAE

software in the `Structural’ domain.

Fig 6: Mesh on C cross section type of ladder chassis

Fig 7: Mesh on I cross section type of ladder chassis

Fig 8: Mesh on Rectangular Box cross section type of ladder chassis

Fig 9: Mesh on Rectangular intermediate cross section type of

ladder chassis

Fig 10: Mesh quality check on C cross section type of ladder chassis

Fig 11: Mesh quality check on I cross section type of ladder chassis

Fig 12: Mesh quality check on Rectangular Box cross section type of

ladder chassis

Fig 13: Mesh quality check on Rectangular intermediate cross

section type of ladder chassis



257

B). FEA for ladder chassis:

Now a day’s in industry shorter product development

cycle and faster time-to-market is done, with increased

emphasis on up-front analysis to design, develop, and

optimize a reliable and durable product. Electronic

prototyping, reduce development costs instead of

hardware prototyping.

Today structural analysis is to perform system

analysis instead of component analysis. The advent of

faster computers and robust FEA software allows

Design engineers to build larger, more refined and

complex models resulting in timely, cost-effective,

accurate, and informative solutions to customer

problems.

The effects of stress, strain and displacement are

computed in the structural analysis under the varying

load condition.

C). Structural analysis of Ladder Chassis:

C- CROSS SECTION TYPE:

Fig 14: Displacement on C cross section type of ladder chassis

Fig 15: Von Mises stress on C cross section type of ladder chassis

Fig 16: Max Shear stress on C cross section type of ladder

chassis

I- CROSS SECTION TYPE:

Fig 17: Displacement on I cross section type of ladder chassis

Fig 18: Von Mises stress on I cross section type of ladder chassis

Fig 19: Max Shear stress on I cross section type of ladder chassis



258

Rectangular Box (HOLLOW) Cross Section Type:

Fig 20: Displacement on Rectangular Box (Hollow) cross section


Fig 21: Von Mises stress on Rectangular Box (Hollow) cross section


Fig 22: Max Shear stress on Rectangular Box (Hollow) cross section


Rectangular Box (INTERMEDIATE) Cross Section Type:

Fig 23: Displacement on Rectangular Box (Intermediate) cross


Fig 24: Von Mises stress on Rectangular Box (Intermediate) cross


Fig 25: Max Shear stress on Rectangular Box (Intermediate) cross


In the analysis of existing component, we have

taken quad element of 3mm size for meshing. Element

size is taken in such a way every geometry feature

should be captured in mesh. If there is any hole then

washer is provided on it to get adequate result. More the

number of elements accuracy will increase but solution

time will also increase so a proper combination between

accuracy and solution time is considered while choosing

the element size.

VI. RESULT

After the calculation carried on Hyper Mesh we have

concluded that our Rectangular Box (intermediate)

section is safer under 12.825 tone load which is the Total

weight of vehicle including gross vehicle weight and

weight of passengers. The displacement is good of our

Rectangular Box (intermediate) section in comparison to

C, I and Rectangular Box (hollow) section type chassis

therefor our chassis is more safer among all type of cross

sections.



259

TABLE I

COMPERATIVE ANALYSIS OF DIFFERENT CHASSIS

S.

No

Cross-

sections

Displacem

ent

(mm)

VonMise

s Stress

(Mpa)

Max. Shear

Stress

(Mpa)

1

C-Type

6.153

3.01×102

1.59×102

2

I-Type

4.786

2.34×102

1.24×102

3

Rectangular

Box (Hollow)

Type

2.683

1.27×102

6.53×101

4

Rectangular

Box

(Intermediate)

Type

1.839

1.12×102

5.81×101

VII. CONCLUSION

From the results, it is observed that the Rectangular

Box (Intermediate) section is more strength full than the

conventional steel alloy chassis with C, I and Rectangular

Box (Hollow) section design specifications. The

Rectangular Box (Intermediate) section is having least

deflection i.e., 1.839 mm in all the four type of chassis of

different cross section. Finite element analysis is

effectively utilized for addressing the conceptualization

and formulation for the design stages. The results

obtained are quite favorable which was expected. The

iterations are carried out in the analysis phase which

yields the suitable values for design parameter.

Following information is achieved.

1) Part is safe under the given loading condition.

2) To improve performance, geometry has been

modified which enables to reduce stress levels

marginally well below yield limit.

REFERENCES

[1] Yucheng Liu, ―Crashworthiness Analysis of Finite Element Truck Chassis Model Using LS-DYNA‖, 11th International LS-DYNA

Users Conference, Department of Mechanical Engineering,

University of Louisiana, Lafayette, LA 70504, USA.

[2] Vijaykumar V. Patel, R. I. Patel, ―Structural analysis of a ladder

chassis frame‖, World Journal of Science and Technology 2012, 2(4):05-08, ISSN: 2231 – 2587.

[3] Hemant B.Patil, Sharad D.Kachave, Eknath R.Deore, ―Stress

Analysis of Automotive Chassis with Various Thicknesses‖, IOSR Journal of Mechanical and Civil Engineering (IOSR-

JMCE), Vol. 6, Issue 1 (Mar. - Apr. 2013), PP 44-49.

[4] N.V.Dhandapani, Dr. G Mohan kumar, Dr K.K.Debnath, ―Static

Analysis of Off-High Way Vechile Chassis supporting Structure

for the effect of various Stress dstributions‖, IJART, Vol.2 Issue 1, 2012, 1-8.

[5] Haval Kamal Asker, Thaker Salih Dawood, Arkan Fawzi Said, ―Stress Analysis os standard Truck Chassis during ramping on

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Engineering and Applied Sciences, Vol. 7, NO. 6, June 2012

[6] M. Ravi Chandra, S. Sreenivasulu, Syed Altaf Hussain,

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Research and Development (IJMPERD ) ISSN 2249-6890 Vol.2,

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[7] Monika S. Agrawal, Md. Razik, ―A Review on Study of

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Engineering Research (IJMER), Vol.3, Issue.2, March-

April. 2013, pp-1135-113.

[8] Roslan Abd Rahman, Mohd Nasir Tamin, Ojo Kurdi ―Stress

analysis of heavy duty truck chassis as a preliminary data for its fatigue life prediction using FEM‖ Jurnal Mekanikal December

2008, No. 26, 76 – 85.

[9] Cicek Karaoglu, N. Sefa Kuralay ―Stress analysis of a truck

chassis with riveted joints‖ Elsevier Science B.V Finite Elements

in Analysis and Design 38 (2002) 1115–1130.

[10] Mohd Azizi Muhammad Nora,, Helmi Rashida, Wan Mohd Faizul

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