M.E. Seminar 3

Harshal R. Borole

Finite Element Analysis Techniques

for Stress Calculations and safety of

Dump Truck Frame

Introduction

Nowadays, transportation industry plays a major role in

the economy of modern industrialized and developing

countries. The goods and materials carried through

heavy trucks are dramatically increasing.

There are many aspects to consider when designing a

heavy trucks chassis, including component packaging,

material selection, strength, stiffness and weight.

A dump truck frame is the most crucial part of the truck

that gives strength and stability to the vehicle under

different conditions.

A dumper frame – rigid to withstand shock, twist,

vibration and other stresses.

A well structured and properly built frame improves crash

worthiness, passenger safety and weight efficiency

Significance of the dumper frame

Dump truck is the variant on the basis of chassis, mainly

consisted of the chassis, power transmission device,

lifting mechanism, sub-frame, special-purpose box

and back flip axis etc.

The sub-frame plays the role of transitional frame to

enable the main frame support as much homogeneous

load as possible.

Sub-frame is connected to main frame through u-shape

bolts and thrust connection board, and is hinged

with cargo body through the back flip axis and

lifting cylinder.

Frame is subjected to various loads at different

conditions.

a) Static load of the carriage and main body.

A 3D model of various mountings on the dump truck frame

during unloading process

Dump Truck Frame

A Dumper truck frame is a complex assembly which supports the loads

from lifting cylinder and carriage and also is subjected to harsh, uneven

road conditions.

The frame should have optimum strength along with adequate bending and

torsional stiffness to withstand such loads and conditions.

FEA study provides the basis for designing the frame since the frame is

modeled in various CAD softwares and analysis for strength and bending is

done by applying boundary conditions and different loads.

Different researchers have used different analysis techniques for optimizing

the design of frame for strength and weight reduction.

AGENDA

Statement of Purpose

Design Considerations

FEA Techniques

Modeling and Analysis

Results & Discussions

Statement of Purpose

To Study various finite element analysis

techniques used for

a) Calculating different types of stresses induced

and deformation of dump truck frame

subjected to various loading conditions.

b) Determining the critical areas of stress

concentration for a fail-safe and lightweight

structure.

Design Considerations

The dumper frame is very critical in designing as there

are various factors to be considered while

a) Dumper frame at rest – Static loads supported by the

frame.

b) Dumper is moving - different sets of vibration modes of

the frame.

c) Dumper is unloading – Dynamic loads and torque

reactions.

For the first case, FEA is done on different sections of

the frame for determining the critical areas of stress

concentration.

For second case, FEA is done on the whole frame

which is excited to different low frequencies which are

close to potential exciting sources like oscillations of

road, vibration from engine etc.

Finite Element Analysis

Techniques

Based on the conditions, dumper truck frame is

analyzed for stress optimization by following

techniques :

1) FEA for Static load.

2) Modal analysis for determining various mode

shapes and predicting different dynamic responses

under excitations.

3) Dynamic analysis of the frame structure during

initial state of cylinder lifting and critical state of

goods declining.

4) FEA by reinforcement technique for stress

optimization.

Static Load Analysis For this analysis, a standard dump truck with following

specifications was used and the frame model was

prepared in CATIA and finally analyzed with the help of

ANSYS software.

Gross Vehicle Weight (GVW): 25000kg.

Gross Combined Weight (GVW + Payload): 26200kg.

Frame: Ladder type heavy duty frame, depth- 285mm,

width- 65mm, frame width- 903mm.

The magnitude of pressure on the upper side of chassis

is determined by dividing it into 3 parts.

1) P1= F/A = 128511 / 65 * 10-6 * 6670 = 290321.9248 N/m2

2) P2 = 1200 * 9.81 / 65 * 10-6 * 1400 = 129362.6374 N/m2

3) P3 = 1200 *9.81 / 65 * 10-6 * 740 = 244740.1247 N/m2

Total Deformation of frame by static analysis

Modal Analysis Of Truck Frame

Frame forms the backbone of the dump truck, when the

truck travels along the road, the truck chassis is excited

by dynamic forces caused by the road roughness,

engine, transmission etc.

After constructing a finite element model for the frame,

modal analysis can be used a tool to determine natural

frequencies and mode shapes.

Sr. no. Mode no. Frequency Displacement

1 1 16.894 Twisting about X-axis

2 2 25.537 Bending about Y-axis

3 3 27.427 Deformation about X-axis and bending

about Y-axis

4 4 28.746 Twisting about X-axis and Bending

about Y-axis

5 5 33.971 Twisting about X-axis

6 6 34.316 Deformation about X-axis and bending

about Y-axis

7 7 36.564 Deformation about X-axis and Y-axis

8 8 46.316 Deformation about X-axis

FEA Of Frame During Unloading

Condition

The dump truck loads the goods by large construction

machinery, so the phenomenon of biased loading goods

frequently happens.

In the unloading process, because of the biased load of

goods, the stresses induced in the frame are worse.

So force analysis should be carried out to detect critical

areas of stress concentration.

The unloading of goods condition consists of two parts –

1) Initial state of oil cylinder lifting

2) Critical state of goods declining

Initial State Of Oil Cylinder Lifting

In this state, because the static friction torque of each

hinge point in lifting system is large and the lifting Angle

of oil cylinder is the most adverse, the lifting force should

be the largest.

Meanwhile, the reaction force oil cylinder against to the

secondary frame is also the largest.

Critical State Of Goods Declining In this state, the cargo body has left away from the

surface of the frame when goods are about to decline,

so all the weight is carried by the back flip axis and the

oil cylinder.

FEA By Reinforcement Technique

For Stress Optimization

In this, finite element analysis is performed on a truck

frame and critical areas of stress concentration are

determined in terms of von-mises stresses.

Reinforcement is the technique of adding cover plates on

external side members at highly stressed regions to

improve the strength and life of the frame.

A CAD model of the frame is prepared in CATIA V5R19 and

structural analysis is done in ANSYS workbench.

The meshed model has applied boundary conditions and

load is applied on side rails.

The load is applied on complete span of the side rail as

uniformly distributed load.

Von mises stress distribution in original frame

Von mises stress distribution in reinforced frame

Total deformation of original frame

Total deformation of reinforced frame

Maximum principal stress in original frame

Maximum principal stress in reinforced frame

Type Main frame Reinforced frame

Pressure (MPa) 0.07395 0.07148

Total Deformation

(mm)

5.0671 4.8307

Von-Mises Stress

(MPa)

295.21 200.45

Max Principal Stress 132.79 128.89Table no. 2 Structural analysis results for original frame and

reinforced frame

From the above table and analysis, we can conclude that –

Maximum stress and maximum displacement in reinforced

frame is lower than original frame.

Reinforced technique decreases deformation of frame by 4.7

% and stress by 31.42 %

In order to obtain same deformation or stress level, we can

apply additional load of 600 kg on the frame.

So reinforced frame increases the load carrying capacity with

same factor of safety as of original frame.

References

Jing-ping Si, Guo-sheng Wang, Xian-long Ding,

‘Analysis of Dump Truck Unloading Condition

Based on ANSYS’, Advanced Materials Research Vol.

548 [2012]

Z. Chen et. Al.,‘The Lightweight Design of a Dump

Truck Frame based on Dynamic Responses’, 18th

International Conference on Automation & Computing,

September [2012]

Pratik Sarda, Prof. Baskar P. et. al., ‘Stress

Optimization of Frame with Reinforcement

Technique by FEA’, International Journal of

Engineering Research & Technology (IJERT) Vol. 3

Issue 5 [2014]

References

Monika S. Agrawal, Md. Razik ‘Finite Element

Analysis of Truck Chassis’, International Journal of

Engineering Research & Technology (IJERT) [2013]

Nouby M. Ghazaly, ‘Applications of Finite Element

Stress Analysis of Heavy Truck Chassis: Survey

and Recent Development’, Journal of Mechanical

Design and Vibration, [2014]

Patel Vijaykumar V, Prof. R. I. Patel, ‘Structural

Analysis of Automotive Chassis Frame and Design

Modification for Weight Reduction’, International

Journal of Engineering Research & Technology (IJERT)

Vol. 1 Issue 3 [2012]