International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
Analysis of Trunk Door Seal of Circular Cross
Section Using FEM
S. B. Yapalaparvi1, Mahantesh Tanodi1, D. N. Inamdar1, G.V.Chiniwalar1
1
Department of Mechanical Engineering, Hirasugar Institute of Technology, Nidasoshi, Karnataka, India
Abstract— Hyper elasticity refers to material that can
experience large elastic strain that is recoverable. Rubber like
and many other polymer material fall in this category.
Elastomers commonly referred as rubbers are hydrocarbons
polymeric material similar in structure to plastic resin. The
rubber seals are used as trunk door seals in automobiles cars
which act as a sealing material between the surrounding
environment and the inside region of the trunk door. These
seals are made up of elastomers (Hyperelastic materials). The
commercially available seals are circular and elliptical in their
cross section. In this paper a non-linear analysis is carried out
to study the behaviour of the seal material and to find the
deformation, stress distribution and the contact pressure
using ansys. This analysis is done for circular cross sectional
dimensions of the seals to find the contact pressure and stress
distribution. The selection criteria for these seals are that they
should develop a high contact pressure when the deflection is
applied. This is to ensure a leak proof sealing and also they
should have a low maximum stress distribution value for
durability, fatigue life of the seal. A seal with the above
criteria is selected from the analysis results recommended.
Keywords— hyperelastic material, trunk door seal, contact
pressure, circular cross-section
1. INTRODUCTION
Hyper elasticity refers to materials that can experience
large elastic strain that is recoverable. Rubber-like and
many other polymer materials i.e., elastomers fall in this
category [1]. Elastomers, commonly referred as rubbers,
are hydrocarbon, polymeric materials similar in structure to
elastomers began to replace the scarce natural rubber, and
since that time, production of synthetics has increased until
now their use for surpasses that of natural rubber. The
major distinguishing characteristic of elastomers is their
great extensibility and high-energy storing capacity. The
constitutive behaviour of hyperelastic materials is usually
derived from the strain energy potentials. Also,
hyperelastic materials generally have very small
compressibility. This is often referred to incompressibility.
The hyperelastic material models assume that materials
response is isotropic and isothermal. This assumption
allows that the strain energy potentials are expressed in
terms of strain invariants or principal stretch ratios. Except
as otherwise indicated, the materials are also assumed to be
nearly or purely incompressible. Material thermal
expansion is also assumed to be isotropic. A material is
said to be hyperelastic ifa there exists an elastic potential
function W (or strain energy density function) that is a
scalar function of one of the strain or deformation tensors,
whose derivative with respect to a strain component
determines the corresponding stress component. This paper
deals with analysis of one such hyperelastic material used
in trunk door seals of automobiles and stresses,
deformation and pressures developed are studied.
2. STATEMENT OF THE PROBLEM
A typical cross section of a trunk door seal is as shown in the
figure; as the door is operated, the hyper elastic structure deforms
and acts as a seal between the door and the mating component.
This seal gets enormous deformation. The seals are rubber
(elastomer) like materials capable of taking up very large strains
without plastically yielding. These materials need to be specially
treated in FEA in contrast to material like steel and cast iron,
etc. Analysis of the seal using FEM (ANSYS) approach is
requirement.
Fig. 1 Sketch of trunk door seal
plastic resins [2]. The difference between plastics and
elastomers in largely one of definitions based on the
property of extensibility or stretching. Up till World War II,
almost all rubber was natural. During the war, synthetic
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Fig. 2 Deformation of the seal
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
3. REVIEW OF LITERATURE
Hyper-Elastic Contact Analysis of a Push-Button
Diaphragm Seal (Jeffrey R Annis, Rockwell AutomationAlien Bradley): Presented is the non-linear finite 'element
analysis of a rubber diaphragm seal utilized in a
pushbutton design. Analysis considerations encompassed,
nonlinear hyperelastic material behaviour of the rubber,
large deflection analysis of seal complex motion, and
contact analysis with mating parts. Design parameters of
primary interest were, seal deflection patterns and seal
actuation force as a function of travel [5].
Nonlinear Finite Element Analysis -A Technical Paper
by MSC Softwere. MSC Software Corporation: This white
paper discusses the salient features regarding the
mechanics and finite element analysis (FEA) of elastomers.
Although the main focus of the paper is on elastomers (or
rubber like materials) and foams, many of these concepts
are also applicable to the FEA of glass, plastics, and
biomaterials. Therefore, this White Paper should be of
value not only to the rubber and tyre industries, but also to
those involved in the following materials like: glass,
plastics, ceramic, and solid propellant industries,
biomechanics and the medical /dental professions,
highway safety and flight safety seat belt design, impact
analysis, seat and padding design, passenger protection
packaging industry, sports and consumer industries helmet
design, shoe design, athletic protection gear etc. [3-4].
Natural rubber 13 February 1999: Newsletter of the
Rubber Foundation Information Centre for Natural Rubber:
This special of 'Natuurrubber' deals with rubber in
engineering applications. The following papers take the
reader on a journey along calculation methods with FEA
and computers, some spectacular, but also some general
applications, compounding aspects and relevant
properties, etc. Rubber in the building Industry: A
Technical Paper by Ing J.S. Havinga: Most people are
probably only familiar with the use of rubber in sealing
strips for windows and doors. But it can be used as a
building material tool. Rubber in building industry is not
the type of material that one could expect builders to use.
It can be used for many other things as well. On this
ground, this technical paper reveals the fact that rubber can
be found everywhere where tolerances can cause cracks
that leads to leaks and draughts.
materials, and most are treated to resist ozone and pollution
damage, too!
Fig. 4.1 Hardtop door seal
4.2 Hardtop Roof Rail Seals: Hardtop Roof Rail Seals
typically start at the lower windshield post and go up over
the door and rear quarter glass on each side of the roofline.
Most feature front moulded ends as original attached to
soft extruded rubber. Stop leaky or noisy upper windows
by replacing roof rail seals!
Fig. 4.2 Hardtop roof rail seal
4.3 U-Shaped Door Jam Seals: This part for hardtop
models is located behind the door and below the quarter
glass seal on the body. Keeps water and dirt from entering
the rear quarter panels and rusting the sheet metal there.
Made with moulded rubber and a solid metal core as
original
4. BODY WEATHERSTRIPS
4.1 Door Seals
Fig. 4.3 U-Shaped Door Jam Seal
Most of our door weather-strips have correct original
features like moulded ends and push-in clips. This image
displays a typical hardtop or convertible door seal. Door
seals for post sedan models go completely around the
outside edge of the door frame that surrounds the glass.
Super Car Specialty door seals are made of top quality
ISSN: 2231-5381
4.4 Door J-Seals: These parts are shaped like an inverted
"J", and are located on the upper front edge of many '55-'61
doors. They are separate of the door main seals, and keep
water and debris from entering at the leading edge of the
door.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
Fig. 4.4 Door J-Seal
Fig. 4.7 Trunk Door Seal Strip
4.5 Trunk Seals: This is one of many different profiles
used on various GM cars. Most trunk seals are located in
the trunk opening gutter on the body, although they were
installed on the trunk lid of some early models. Replacing
a trunk seal is cheap insurance against a rusted trunk floor.
American-made extrusion is the best available
Fig. 4.5 Trunk Seal
This part for hardtop models is located behind the
door and below the quarter glass seal on the body.
Keeps water and dirt from entering the rear quarter
panels and rusting the sheet metal there. These are
made with moulded rubber and a solid metal core as
original.
5. NONLINEAR ANALYSIS OF A TRUNK DOOR
SEAL
Fig. 5.1 Trunk door seal
In this session we will simulate large deformation (stresses
and deflections) of a rubber seal and its contact process
with a trunk door when being pushed in. The complex
shape of the seal also leads to rubber-rubber surface contact.
The purpose of the analysis is to examine the stresses and
deflections created within the rubber during the closing of a
door. The seal is made of a rubber material and therefore is
modelled using hyperplasic material properties. Since the
trunk door is much stiffer than rubber seal, the trunk door
will be modelled as a rigid body. Additionally, the rubber
seal will come in contact with itself. This contact must be taken
into account explicitly; otherwise the seal will pass through
itself.
The various deflection values given to the trunk door seal
from 1 mm to 5 mm and analysis results are tabulated as
shown below.
Fig. 4.6 Details of Door Seals of an Automobile car
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
Seal wall
thickness
in mm
Corner
radius
in mm
Deflection
In mm
Stress distribution
Contact pressure
1
2
3
2
0.5
4
5
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
ANALYSIS RESULTS FOR TRUNK DOOR SEAL
Maximum
Deflection in
Min Stress in
Deformation in
mm
MPa
mm
1
1.000
0.123E-03
2
2.016
0.335E-03
3
3.056
0.749E-03
4
4.081
0.876E-03
5
5.111
0.167E-03
Corner radius
in mm
Seal wall
thickness in
mm
0.5
2
6
5
Max. Deformation
4
Max. Stress
3
Contact Pressure
2
1
0
1
2
3
4
5
Deflection in mm
Graph 5.1
6. RESULTS AND DISCUSSIONS
The yield strength value for the hyper elastic material is
found to be 13 MPa, assuming suitable factor of safety or
by calculating the factor of safety by assuming Soderberg
equation, we get the permissible stress value for the hyper
elastic material as 4 MPa. From the above tabulated results
Seal wall
thickness and
corner radious in
mm
Max Stress in
MPa
0.164
0.407
0.715
1.145
1.725
Contact
Pressure in
MPa
0.016
0.074
0.093
0.151
0.144
we ensure that the maximum stress values obtained for the
trunk door seal are within the permissible limits. The
tabulation of the analysis results is further carried out for
the trunk door seal by varying the cross sectional wall
thickness dimension and the corner radius in order to study
the deformation, stress distribution and the contact
pressures and to compare the results with earlier results
since it is always desired a trunk door seal with low stress
value to get maximum life and a high contact pressure to
provide leak proof clearance. The cross sectional
dimensions are varied from 2 mm to 1.5 mm, 2.5 mm of
trunk door seal, also from the above analysis results it is
observed that maximum stress is at the corner radius and
hence the corner radius is changed from 0.5 mm to 0.75
mm of trunk door seal, the stress distribution in the
material and the contact pressures are analysed and the
results are tabulated as shown below.
Deflection in mm
Maximum
Deformation in mm
Min Stress in MPa
Max Stress in
MPa
Contact Pressure
in MPa
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1.000
2.016
3.056
4.081
5.111
1.000
2.952
5.616
7.525
8.363
1.000
2.000
3.009
4.037
5.046
1.033
2.032
3.244
4.910
5.010
0.123E-03
0.335E-03
0.749E-03
0.876E-03
0.167E-03
0.170E-03
0.230E-03
0.150E-03
0.380E-03
0.390E-03
0.750E-04
0.330E-03
0.260E-03
0.390E-03
0.290E-03
0.560E-04
0.950E-04
0.130E-03
0.299E-03
0.188E-03
0.164
0.407
0.715
1.145
1.725
0.126
0.277
0.434
0.537
0.575
0.191
0.353
0.524
0.752
1.092
0.162
0.315
0.486
0.731
0.955
0.016
0.074
0.093
0.151
0.144
0.023
0.031
0.031
0.024
0.044
0.056
0.108
0.028
0.063
0.062
0.041
0.061
0.059
0.086
0.147
2mm &R0.5
1.5mm &R0.75
2.5mm &r0.5
2mm &R0.75
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International Journal of Engineering Trends and Technology (IJETT) – Volume 9 Number 3 - Mar 2014
7. CONCLUSION
Trunk door seal find application on automobile passenger
car as a sealing material between the trunk and the outside
environment. When the door is closed the trunk door seal
gets elastically compressed between door and thereby
providing a sealing effect. The trunk door seals are made
up of hyper elastic material. Requirement of such seal is
that the working stress should be within allowable limits of
the material and at the same time the contact pressure
between the mating surface should be sufficiently
high(>0.2012 MPa) to ensure a leak proof effect. For these
conceptional designs of trunk door seals have been arrived
at a circular cross section design configuration varying the
wall thickness, fillet radii has been studied for this
configuration using ansys and computing the stresses
developed within members and contact stresses between
the seal and the body. The analysis showed that the design
variant to(trunk door seal with 2 mm wall thickness) is
superior as it gives a lowest of 1.145MPa and highest
contact pressure 0.151MPa. The stress 1.145MPa is less
than the permissible of 4 MPa.
8. REFERENCES
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