Finite element analysis of engine mounting bracket by considering pretension effect and service load

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 04 Issue: 08 | August-2015, Available @ http://www.ijret.org 327
FINITE ELEMENT ANALYSIS OF ENGINE MOUNTING BRACKET BY
CONSIDERING PRETENSION EFFECT AND SERVICE LOAD
Sandeep Maski1
, Yadavalli Basavaraj2
1
PG student, Department of mechanical engineering, BITM, Bellary, Karnataka, India
2
Professor & Head, Department of mechanical engineering, BITM, Bellary, Karnataka, India
Abstract
Bracket is one of the important components of an engine mount assembly, heavy performance truck has their engine supported by
bracket and this engine mounting brackets assembly is used in chassis front frame which has been designed as a framework to
support engine along with transmission member. The main function of the engine mount bracket is to properly balance the engine
and transmission on the vehicle chassis, engine mount is an important part of the vehicle to reduce the vibration and noise, by
which smooth ride of the vehicle can be achieved. Vibration and strength of engine bracket has been continuously a concern
which may lead to structural failure if the resulting vibration and stresses are severe and excessive. The present work focuses on
the FEA analysis of engine mount bracket for three materials by using meshing and analysis software which are HYPERMESH
and ABACUS, the materials used are cast iron, wrought iron and mild steel, modal analysis and static analysis carried out by
which maximum von-misses stress and natural frequency are computed. The main objective is to select the best material from the
obtained result under prescribed conditions.
Key Words: Engine mount bracket, Vehicle chassis, Modal & Static analysis, pretension load, & Service load.
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1. INTRODUCTION
In this automotive era the need for light weight structural
materials is increasing as there is a more focus on fuel
consumption reduction and improvement in decreasing the
emission. The magnitude of production volumes has
traditionally placed severe requirements on the robustness of
process used in the manufacturing. The manufacturers have
strong importance on the cost has the demand for the
component to improve the material performance and to
deliver these materials at low cost is the requirement. There
are number of vibrations and noise equipments which affect
the vehicle body. Due to uneven roads and by bad
suspension, vibration and noise are generated in a vehicle
body, which will result in the high frequency. The noise and
vibration generated by the equipments is transferred to the
vehicle body points. Body attachment stiffness plays a vital
role for NVH performance improvement. Due to disturbance
from the road and engine at idle, usually below 30 Hz
frequency is developed. To reduce and control the vibrations
engine mount bracket should be stiff. In the other case of
high frequency range of 30 -250 Hz from the engine has to
be absorbed by bracket, so engine mount bracket must
satisfy these criteria.
In automobile sector the extremely competitive automotive
business needs manufactures to pay a lot of attention
to traveling comfort. Resonant vibration is from
unbalanced masses exist within the engine body, this is
causing the designers to direct their attention to the
event of top quality engine mounting brackets so as to
confirm that there is improvement in riding comfort. The
demandfor higher playacting enginemount
brackets should not be offset by arise within
the production prices and/or development cycle time.
Due to the varying speeds and uneven roads, chassis bodies
have underwent uneven balancing force. These tendencies
bring about to unwanted vibrations that cause associate
uncomfortable ride and conjointly cause extra stresses
within the automobile frame and body. An engine mounting
system includes a front mount, rear mount, and a
transmission mount. Mounting axis of the engine mount,
front mount, and rear mount area unit is vertical where as
the mounting axis of that transmission mount is lateral. The
transmission mount might vary its spring constant
throughout vehicle movement. Resilient mounting will offer
longer life for frame and block mounting brackets. The front
engine together with associate in nursing engine mount
bracket that is fastened on one finish thence, the front engine
mount mounting the engine with the material endured the
opposite finish thence ,front engine mount mounting the
engine with the material interposed between the engine and
also the engine mount bracket, the material supporting the
engine bracket fastened to the front aspect of the engine,
wherever area is provided between the front aspect of the
engine and engine mount bracket and an off-line equipment
disposed in area between the front aspect of the engine and
mount bracket, wherever within the front engine mount
features a strength against the load applied there to within
the longitudinal direction of the vehicle but that of the off-
line equipment.
In diesel engine, the engine mounting bracket is the major
problem as there is unthrottled condition and higher
compression ratio and even there are more speed

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irregularities at low speed and low load when compared to
gasoline engines. So due to this there are more vibration
excitation. By this vibration engine mount bracket may fail,
so by optimizing the shape and thickness of engine mount
bracket we can improve the performance at initial design
stages. By some studies it is observed that brackets saved
38% of mass. Structural optimization is an important tool
for an optimum design; comparison in terms of weight and
component performance structural optimization techniques
is effective tool to produce higher quality products at lower
cost.
1.2 Literature Review
Umesh S Ghorpade, D.S Charan, Vinay Patil and Mahendra
Giakwad [1]., In this paper they have designed engine
mount bracket of a car and focused on to determine natural
frequencies of car engine mount bracket. They have
considered the three materials for engine mount bracket that
is aluminum alloy, magnesium alloy, gray cast iron when
modal analysis is carried out, it is found natural frequencies
of gray cast iron is low which will prove more hindrance in
vibration of engine mount bracket so they have eliminated
gray cast iron, in terms of analysis aluminum alloy and
magnesium alloy are showing almost near value of natural
frequency in practical terms as magnesium alloy is having
better strength that is low stress value, so preferably
magnesium alloy is selected as better material by study.
Mr. Pramod Walunje, Prof. V.K. Kurkute [2]., In this work
they have mainly focused on the use of light weight material
for bracket and also to reduce the weight of the bracket, in
this paper the same model and materials has been taken as
the paper [1]. Here the weight of the material is reduced and
pre processing and post processing is carried out and even
with this an experimental setup is also used to find the stress
level of the materials they have observed that aluminum
alloy have good natural frequency and stresses are also
within the yield strength, so by considering the aluminum
and reducing its thickness further by 2mm than original
component, they found that now von misses stresses are also
with in yield stress so they have achieved reduction in the
mass of bracket up to 0.43kg when compared to previous
one.
In the above references the authors carried out the FEA of
engine mount bracket for the static type of loading and
analysis carried out was static and modal analysis with
optimization of materials,
By information from the above survey it is decided the task
to be carried out
1. Understanding the loading conditions on the engine
mount bracket.
2. Selecting the type of materials which can be used in
manufacturing of engine bracket.
3. Selecting the proper designing tools for modeling
4. Selecting the suitable meshing and analysis tool.
2. FINITE ELEMENT ANALYSIS
The Finite Element Method is a numerical approximation
method, in which the complex structure is divided into
number of small parts that is pieces and these small parts are
called as finite elements. These small elements are
connected to each other by means of small points called as
nodes. As the finite element method uses matrix algebra to
solve the simultaneous equations, so it is also known as
structural analysis and it’s becoming primary analysis tool
for designers and analysts.
The three basic FEA process are
a) Pre processing phase
b) Processing or solution phase
c) Post processing phase
2.1 HyperWorks
HYPERWORKS is one of the most used software to solve
finite element analysis which will provide solid meshing,
surface meshing then the processors or solvers used are
MSC Nastran, Marc, Abacus, LS-DYNA, ANSYS, and
Pam-Crash.
Altair hyper works is having many tools for the creation of
ready models and to analyze for non-linear, linear, thermal,
explicit dynamics and other types of finite element
problems. To deal with gaps in a model there is a tool called
geometry cleanup which will make engineers easy to
modify. For the creation of models from scratch there is a
tool called solid meshing tool so it is very easy to create FE
models by using hyper mesh. Meshing can be easily done on
the surfaces by using automated meshing tool and even there
are manual methods which provide more control. In this
finally boundary conditions, loads and analysis is built in for
most FE solvers, which will minimize the need to edit input
decks.
2.2 Abaqus
Abacus is important simulation program in this any range of
problems can be solved from simple linear analysis to non
linear simulations. Abacus is having library of elements
which is used for studying structural problems and more
(stress/displacements). By this problems can be simulated in
areas such as heat transfer, thermal management, mass
diffusion, acoustics, solid mechanics and piezoelectric
analyses. In most simulation even including non linear ones,
the user needs to provide engineering data information such
as geometry of model, material behavior, boundary
conditions and load applied on it. But for non linear analysis
in abacus, it chooses automatically appropriate load
increments and convergence tolerance.
Finite element mesh is the main goal of preprocessing, after
this material properties have to be assigned and boundary
conditions to be applied in the form of restraints and loads.
Geometry is subdivided into elements by finite element
mesh, which contains nodes. In space nodes are just point
locations which are present at each side of element corner.
In this 2D-elements or 3D-elements may be present. Plane
stress, axis symmetric and plane strain are conditions for

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2D-elements and physical thickness in three dimensions is
present for 3D element. Three translation degree of freedom
per nodes are present for solid element. Depending upon the
class of analysis degree of freedom is assigned, for example
only temperature or many temperature of degree of freedom
are present at each node in thermal analysis. As meshing is
most time consuming job in FEA so free meshing is carried
out, which automatically subdivides meshing region into
elements thus doing easy meshing. With the type of solution
material properties will vary. Linear static analysis requires
elastic modulus and Poisson’s for each material type, after
this analysis the input file is run in abacus to get the onp file
which will give the complete result and is viewed in
hyperview
2.3 Scope of Project
This thesis is part of a research project whose aim is to
design engine mount bracket. The overall aim of the project
is to develop models of engine mount bracket by using
CATIA software. In order to create computational tools that
facilitates the design of engine mount bracket with improved
performance. This model has been developed in order to
create a finite element (FE) model of an available
automotive engine mount bracket, so that it’s current static
and modal behavior could be analyzed, several materials can
be tested in this model and, perhaps, improvements to the
current performance specifications can be achieved.
Computational modeling and simulation of an available
engine mount are performed to gain such an understanding
and to evaluate the effectiveness of current solutions
available in the market. Special attention is given to the
correct modeling of nonlinear effects on the static behavior
of the engine mount bracket. The FE analyses in this thesis
have been performed in ABAQUS. The choice of using a
commercial FE code makes it easier to focus on the
engineering problem rather that a detailed description of
complex FE models. It also results in methods that can be
put directly to use in industry.
2.4 Objective of Project
To do static structural and modal analysis of engine
mounting bracket for three different materials viz. Mild steel
(MS), Wrought Iron (WI) and Cast Iron (CI) and suggest
best material for the bracket.
3. Engine Mount Bracket
The engine mounting bracket is most important part of
vehicle in reducing vibrations and harshness for the smooth
ride of the vehicle. The important function of an engine
mounting bracket is to balance the engine & transmission
properly on the vehicle chassis for good balance control
when vehicle is in motion. In this engine mount bracket of a
truck is modeled using CATIA.
Fig -1: CATIA model of Engine mount bracket
3.1 Meshing of Engine Mount Bracket
For meshing the model solid mesh is generated by keeping
mesh size as 5 mm.
Fig -2: Meshed model of Engine mount bracket
3.2 Boundary and Loading Conditions
Constraints: The element which is used to fix engine
mounting bracket and body of the vehicle is fixed and used
as a rigid element. In this chassis frame which is fixed and
connected to the bracket and is made constrained at the both
ends, further after constraining analysis is carried out.
Loads: Specific values of load are applied on engine
mounting bracket. The load is taken as 1000N which is
considerable as the distributed weight of the engine; this
load is taken as service load as shown below in fig.
Pretension Load of 24000N is applied on the bolt, which is
the standard pretension load calculated for the M12 bolt, to
calculate the pretension effect as shown below in fig.

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Fig -3: Service load acting on bracket
Fig -4: pretension load acting on bolt
Table -1: Mechanical properties of materials used for
engine mount bracket
Sl.
No
Mechanical
Property
Mild
Steel
Cast
iron
Wrought
iron
1
Young’s modulus
(Mpa)
2.1e+5
1.2 e+5
1.9 e+5
2 Poisson’s ratio 0.30 0.28 0.30
3 Density(Kg/mm3
) 7.89e-9
7.20e-9
7.75e-9
4
Yield Strength
(N/mm2
)
370 130 210
5
Ultimate
Strength(N/mm2
)
440 220 320
3.3 Analysis
Modal analysis -
Modal analysis is used to determine the vibration features of
a component in the form of mode shapes and natural
frequency. The normal modal analysis is carried out for
engine mount brackets, in three design iterations. The three
design iterations are carried out for different materials with
constant of thickness which is mentioned as per the
company standards. Our objective is to perform modal
analysis to determine the natural frequencies and mode
shapes for natural vibration modes for three structures in
which the damping and applied load is neglected.
Static analysis -
A static structural non linear analysis is the time
independent analysis where we do check for displacements,
stress and strain of a component. Static analysis for all the
above materials is processed using Altair Hyper works and
solved using the software Abacus. Here static analysis is
carried out to all the above events to determine the
stress concentration and the displacement. The stress
concentration and the displacement are carried out for both
service load and the pretension load. The results obtained
are shown in the figures.
3.4 Modal Analysis Results
Fig -5: Modal analysis of mild steel bracket
Fig -6: Modal analysis of cast iron bracket

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Fig -7: Modal analysis of wrought iron bracket
Table -2: Comparison of Modal analysis Results for three
materials of engine mount bracket
Design
iteration
Materials
Thickness
3.4mm
Mode frequency (HZ)
1 2 3 4
01 Mild steel 66 102 175 185
02 Cast iron 55 87 168 171
03 Wrought iron 64 100 174 182
3.5 Discussion
By comparing normal modal analysis for all materials of
engine mount bracket that is the first fundamental natural
frequency of mild steel is 66Hz which is found to be good
compared with two materials. To select the suitable material
for the engine mount bracket, we can’t decide only on the
basis of modal analysis, so further static analysis is carried
out to know the stress and displacement of the materials
which will be helpful to choose the suitable material for the
engine mount bracket.
3.6 Static Analysis Results
Fig 8: Displacement for pretension load acting on bolt
Fig -9: Displacement for service load acting on bracket
Table -3: Maximum displacement of bracket
Material displacement
(mm)
Mild
steel
Cast
iron
Wrought
iron
Pretension load 0.5 0.5 0.5
Service load 1.6 2.2 1.7
Fig -10: Maximum stress for pretension load of mild steel
bracket
Fig -11: Maximum stress for pretension load of cast iron
bracket

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Fig -12: Maximum stress for pretension load of wrought
iron bracket
Fig -13: Maximum stress for service load of mild steel
bracket
Fig -14: Maximum stress for service load of cast iron
bracket
Fig -15: Maximum stress for service load of wrought iron
bracket
Table -3: comparison of stress of engine mount bracket for
different materials
Different
materials
Stress for
pretension
load in
N/mm
2
Stress
for
service
load in
N/mm
2
Yield
strength
in
N/mm
2
Ultimate
strength
in
N/mm
2
Mild
steel
284.39 283.53 370 440
Cast
iron
289.20 289.05 130 220
Wrought
iron
284.44 283.93 210 320
Chart -1: Stress analysis for different material bracket

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3.7 Discussion
In the comparison of material variation, From the above plot
of figures we can clearly see the deformation of engine
mount bracket is taking place in all the materials for the
applied service load and displacement is varied in all the
materials, but the maximum deformation is 2.2mm, which is
in the cast iron engine bracket, this is due to the fact that
density of the material is different for all the materials. The
minimum deformation is in the mild steel bracket that is
1.6mm because mild steel is having more density when
compared to cast iron and wrought iron.
From the table-3 it can be seen that von misses stress for all
three materials are almost nearer, this is due to fact that area
and force for all materials is same but stress coming on the
mild steel bracket are well within the yield strength
(370Mpa) but von misses stress of cast iron and wrought
iron is greater than yield strength, so we cannot select cast
iron and wrought iron as suitable for the bracket.
4. CONCLUSIONS
As vibration and strength plays an important role in the
design of engine mount bracket, so in this paper special
attention has been given for selection of suitable material for
engine mount bracket so that it can withstand high strength
and vibrations.
It can be seen from the obtained results and discussion that
for modal analysis first fundamental natural frequency of
mild steel is high that is 65Hz compared with cast iron and
wrought iron and in case of static analysis displacement of
mild steel is 1.6mm which is less when compared to other
two materials and the maximum von-misses stress coming
on mild steel is lesser than yield point, hence mild steel is
considered as better material to design engine mount bracket
REFERENCES
[1]. Umesh.S.Ghorpade, d.s.chavan, vinay patil &
mahendra gaikwad, “Finite element analysis and
natural frequency optimization of engine bracket”
(IJMIE) ISSN No. 2231 –6477, Vol-2, Iss-3, 2012.
[2]. Mr.Pramod Walunje, Prof.V.K.Kurkute, “Engineering
Optimization of Engine Mounting Bracket Using FEA”
Indian Journal of Research ISSN-2250-1991 volume:2,
Issue:12, Dec 2013.
[3]. Pavan.B.Chaudhari, Dr.D.R.Panchagade “Comparison
of Magnesium, Aluminum and Cast Iron to obtain
Optimum Frequency for Engine Bracket using Finite
Element Analysis”(IJERA) ISSN: 2248-9622 Vol.2,
Issue 5, September- October 2012.
[4]. A.S.Adkine, V.S.Kathavate, G.P.Overikar,
S.N.Doijode, “Static Behavior of Engine Mounting
Bracket” International Advanced Research Journal in
Science, Engineering and Technology ISSN (Online)
2393-8021Vol. 2, Issue 4, April 2015.
BIOGRAPHIES
Sandeep Maski received the B.E degree in
mechanical engineering in 2012 from
BITM, Bellary affiliated to Visvesvaraya
technological university Belagum and
worked as Mechanical engineer in Hospet
steels ltd, presently pursuing MTECH 2nd
year from BITM, Bellary.

Finite element analysis of engine mounting bracket by considering pretension effect and service load

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Finite element analysis of engine mounting bracket by considering pretension effect and service load