investigation of adhesive joint shear strength for a braking system

Rade et al., International Journal of Advanced Engineering Research and Studies
E-ISSN2249–8974
Research Paper
INVESTIGATION OF ADHESIVE JOINT SHEAR STRENGTH
FOR A BRAKING SYSTEM
1
Prashant Sudhiranjan Rade, 2Prof. Dr. Dheeraj S.Deshmukh, 3Swapnil S. Kulkarni
1
Address for Correspondence
ME-Design-pursuing, 2 Prof & Head of Mech. Engg. Dept. SSBT’s College of Engineering, &Technology,
Bambhori, Jalgaon
3
Director-Able Technologies India Pvt. Ltd., Pune
ABSTRACT:
This dissertation work is aimed to investigate the adhesive joint shear strength for a braking system. The problem is
investigated using mathematical analysis as well as analytical methodology with Finite Element Analysis. The dissertation
has is presented with variants of different adhesive layer thickness proposed for the shear strength investigation of adhesive
joint to be used in the automotive industry. In FEA, the competent software ‘NASTRAN’ is used for determining the shear
stress induced in different thickness of adhesive layer applied between brake pad and brake shoe. Comparative study for the
methodologies is presented while arriving at the most suitable variant of the brake shoe with respect to the thickness of the
adhesive layer and the geometry manifested by the pattern of the adhesive layer applied. A total of five variants with
different adhesive layer thickness are analyzed for concluding the thesis work.
KEYWORDS: Adhesives, Shear stress of a joint, Brake shoe.
INTRODUCTION
Materials can be joined by using a variety of
methods. Up to about 60 years ago, the principle
joining techniques were by mechanical fastening
(screws, rivets, bolts, etc.) or by welding, soldering or
brazing. All of these methods had advantages and
disadvantages. During the Second World War, a
series of novel adhesives, developed by Dr Norman
de Bruyne at the company which became to be
known as Ciba, was used for structurally bonding
aircraft such as the de Havilland Mosquito. Since that
time, enormous advances have been made in
adhesive bonding technology. With the benefit of
science and experience, we can now use adhesive
joints in load-bearing engineering situations which
can withstand many years of use. As well as aircraft,
adhesives are widely used in motor cars, and nearly
all lightweight structures. They are being used to
locate bearings and gears, and even to transfer loads
in enormous structures such as are used in civil
engineering [1]. Adhesion is concerned whenever
solids are brought into contact, for instance, in
PROBLEM DEFINITION
The Sponsoring Company is working on releasing a
new low cost four wheeler (passenger car segment)
into the consumer market. The emphasis for this car
being economy and stability at higher speeds. The
braking system is being designed with due
consideration for this segment of the consumer. For
technical specifications, the inputs offered for
research are as follows:
Mass of the Vehicle (Light weight
car segment
Maximum speed
Radius of the disc (where brake
pad is applied)
Width of brake shoe
Developed length of brake shoe
Thickness of brake shoe (pad)
750 kg
120 kmph
0.3 m (300 mm)
0.034 m (34 mm)
0.18 m (180 mm)
2 mm
OBJECTIVE:
The Objective of the proposed work is to find the
best configuration of the thickness and area of
contact for the adhesive to affect minimum
permissible Shear Strength of the joint.
MATHEMATICAL TREATMENT FOR CASE
STUDY
For the problem to be diagnosed, the empirical
formulae in the Engineering domain can be applied
for seeking a solution. The study over the subject
Int. J. Adv. Engg. Res. Studies/III/II/Jan.-March.,2014/58-61
coatings, paints, varnishes, multilayered sandwiches,
polymer blends, filled polymers, adhesive joints, and
composite materials. To make adhesion possible, it is
necessary to generate intrinsic adhesion forces across
the interface. Because the final performance or use
properties of these multi component materials depend
significantly on the quality of the interface that is
formed between the solids, it is understandable that a
better knowledge of adhesion phenomena is required
for practical applications.
Pressures on costs and vehicle weight (meeting
Corporate Average Fuel Economy (CAFE)
regulations), while meeting safety goals, and further
accentuate the challenge, driving the industry towards
new, less costly materials and processes. The trend
towards recycling the entire vehicle, already
relatively strong in Europe, has recently begun to
affect material and fastening choices in auto interiors
in Asia. Thus, new materials and processes are
continuously under development. Many of these
require changes in fastening or in companion
construction materials, such as adhesives [2].
done in the past has offered formulae derived by the
researchers in the respective field. Application of the
relevant mathematical rule to the problem at hand can
lend a credible solution for finding the best
alternative. Typically, the formulae in the field of
Applied Mechanics or Structures can be helpful for
finding a numerical value for specifying the quantum
of the unit or direction for the solution.
Now, it is given that
Mass of the Vehicle is 750 kg and maximum speed is
120 kmph, then
m = 750 kg and v = 120 kmph
K.E = ½ mv2
... (1)
= ½ x 750 x 33.332
K.E. = 416.58 x 103 Joules
... (2)
We know that,
... (3)
W.D. = fb x d
[Consider displacement of 2 m] then,
416.58 x 103 = fb x 2
fb = 208.29 x 103 N
... (4)
As, there are total 8 no. of brake shoes then
fb = 208.29 x 103/ 8
fb = 26.036 x 103 N
… (5)
Now, we know that
T = fb x r
... (6)
[Given radius of disc is 0.3 m] then,
T = 26.036 x 103 x 0.3
Rade et al., International Journal of Advanced Engineering Research and Studies
T = 7810.87 N-m
…(7)
For the application being studied the maximum shear
stress allowed by the manufacturer is 30 MPa. [for
details refer Appendix – Test reports]
For a single lap joint, the maximum adhesive shear
stress, τo, max, can be calculated using the following
equations.
σ
8Ga t
.. (8)
το, max = (1 + 3k)
8
E ta
Where,
P
… (9)
σ=
t
L
... (10)
c=
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Ansys/ Abaqus/ RadioSS or similar solver would be
deployed.
Steps in analytical treatment for case study using
Nastran:
Brake Shoe 3D modeling is done in CATIA.
2
cosh (u2c) sinh (u1L)
sinh (u1L) cosh (u2c) + 2 2 cosh (u1L) sinh (u2c)
… (11)
u1 = 2 2 u2
... (12)
k=
3σ (1 − γ 2 )
… (13)
2 Et 2
P = Load per unit width (as derived from equation 5)
L = Length of overlap (bond length)
t = adherend thickness
E = adherend modulus
Ga = adhesive shear modulus
ta = adhesive layer thickness
Ea = Adhesive tensile modulus
γ = adherend poisson’s ratio
u2 =
Now, based on the above formulation and from
equation (8) we will calculate the maximum shear
stress of adhesive joint for different thickness of
adhesives.
Analytical treatment for Case Study using Nastran
Analytical methods refer to techniques and
procedures for analyzing data collected while
conducting an evaluation. Two main types of
analytical methods include qualitative and
quantitative procedures. Quantitative methods
include statistical techniques for analyzing data, and
qualitative methods analyze information, such as
notes from interviews and observations, that cannot
easily be summarized in numerical terms.
Popular quantitative methods used in evaluation
include, but are not limited to, analysis of variance,
factor analysis and linear regression. Quantitative
methods make data easier to analyze and summarize,
and qualitative approaches are subject to varying
interpretations. Many evaluations, especially in
education and the social sciences, combine
qualitative and quantitative techniques. Typically,
Statistical tools are engaged like ANOVA, DOE or
other process control or parameter optimization
techniques. Typically, the software Minitab is
utilized for working on these tools.
Analytical method is also sometimes referred to as
Computational approach:
This presents a computational approach for the
assessment of the given problem. One of the main
features of the work is the search for simplicity and
robustness in all steps of the modeling, in order to
match the proposed method with industrial practices
and constraints. The proposed method utilizes
software in the domain of FEA (Finite Element
Analysis) for analyzing the effects of the variation in
the values of the design parameters influencing the
response parameter. For our case, a suitable CAE
software in the structural domain like Nastran/
Int. J. Adv. Engg. Res. Studies/III/II/Jan.-March.,2014/58-61
Fig. 1: 3 – D Model of Brake Shoe (I)
Fig. 2: 3 – D Model of Brake Shoe (II)
Load and Boundary Conditions:
Torque is applied at the centre of the wheel and upper
surface of abrasive is constrained to simulate the
shear.
Fig.3: 13 Details of Brake Shoe
RESULTS AND DISCUSSION
By using analytical treatment for case study for all
the 5 variants, shear stresses of adhesive joint are
observed as given below.
Variant No. 1:
(Thickness of Adhesive = 3 mm)
Fig. 4: Shear stress plot for adhesive of thickness 3 mm
Above Fig. shows shows the shear stress plot for
adhesive of thickness 3 mm. Here, we are getting
Rade et al., International Journal of Advanced Engineering Research and Studies
maximum
shear
stress
of
( το, max = 19.39 MPa ).
Variant No. 2:
(Thickness of adhesive = 2 mm)
19.39
MPa
Fig. 5: Shear stress plot for adhesive of thickness 2 mm
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Above fig. shows the shear stress plot for adhesive of
thickness 1 mm applied in the form of checkered
stripes. Here, we are getting maximum shear stress of
32.83 MPa ( ο, max = 32.83 MPa ).
Therefore, on the basis of mathematical and
analytical treatment for case study it seems that
Variant no. 1, 2 and 3 are within the permissible limit
of maximum shear stress of Adhesive joint. Table
given below shows the comparison of maximum
shear stress of Adhesive joint obtained by
mathematical and analytical treatment for variant no.
1, 2 and 3.
τ
Table 2: Maximum shear stress obtained by
mathematical and analytical treatment
Above Fig. shows the shear stress plot for adhesive
of thickness 2 mm. Here, we are getting maximum
shear stress of 20.47 MPa ( το, max = 20.47 MPa ).
Variant No. 3:
(Thickness of Adhesive = 1 mm)
Therefore, on the basis of above table it seems that
the maximum shear stress of Adhesive joint obtained
by mathematical and analytical treatment are nearby
same and within the permissible limit of shear stress.
Fig. 6: Shear stress plot for adhesive of thickness 1 mm
Above Fig. shows the shear stress plot for adhesive
of thickness 1 mm. Here, we are getting maximum
shear stress of 25.31 MPa ( το, max = 25.31 MPa ).
Variant No. 4:
(Thickness of adhesive is 1 mm and adhesive coat
are applied as stripes in longitudinal direction)
Fig. 7: Shear stress plot for adhesive of thickness 1
mm applied as stripes in longitudinal direction
Above fig. shows the Shear stress plot for adhesive of
thickness 1 mm applied as stripes in longitudinal
direction. Here, we are getting the maximum shear
stress of 33.26 MPa ( το, max = 33.26 MPa ).
Variant No. 5:
(Thickness of adhesive is 1 mm and checkered
stripes of adhesive coat are applied)
Fig. 8: Shear stress plot for adhesive of thickness 1 mm
applied as checkered stripes
Int. J. Adv. Engg. Res. Studies/III/II/Jan.-March.,2014/58-61
Fig. 9 Comparative Results for different thickness of
Adhesive
CONCLUSION AND FUTURE SCOPE
Conclusion:
The results for the five different variants evolved
during the study asserts the significance of the
parameters determined for this work. The parameters
for thickness of the adhesive and the area of contact
are best manifested in the variant no. 3 i.e., the
variant with 1 mm thickness of adhesive layer and
full coverage for the contact area. Other sub –
optimal variants can also be considered for use based
upon the discretion of the design engineer. Although,
variant no. 4 and variant no. 5 seems to exceed the
permissible limit of shear stresses and as such may
not be recommended for use. The stress distribution
observed over the interface of the brake pad suggests
non – uniform distribution of stresses. The side (end)
of the brake pad exposed to the torque exerted by the
moving brake disc experiences the highest stress
levels; (although the permissible limit of shear
stresses has not been exceeded at any point as per the
analytical results)
Future Scope:
• The recommended variant needs to be
implemented in practice. This might pose
several problems in terms of designing a
dispenser for releasing the adhesive over the
designated mating area of the brake shoe
and the brake pad. Further research work
could be taken up in this area (for
implementation).
• Varying grades and/or brands of adhesives
could be put to test for evolving improved
variants, other than proposed in this research
Rade et al., International Journal of Advanced Engineering Research and Studies
•
•
work. Thickness could be varied as also the
configuration of the pattern of application.
Texture/Surface finish/Surface treatment can
be explored as additional parameter while
pursuing further studies. Curing temperature
and curing time could also be tweaked while
seeking optimization over the influencing
factors.
This study could be replicated in similar
other areas of application in the consumer
products or the aerospace industry.
Fig. 10: Shear stress plot for adhesive of thickness 3 mm
Above Fig. shows shows the shear stress plot for
adhesive of thickness 3 mm. Here, we are getting
maximum
shear
stress
of
19.39
MPa
( το, max = 19.39 MPa ).
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