Modal analysis of Support bracket for air compressor system

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 07 | July -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1730
Modal analysis of Support bracket for air compressor system
Lokesh1, Pavan Prabhakar2
1Post Graduate student, Department of Mechanical Engineering, New Horizon college of Engineering,
Bangalore, India
2Assistant professor, Department of Mechanical Engineering, New Horizon college of Engineering,
Bangalore, India
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Abstract - This paper describes the static and modal
Analysis of supporting bracket for air compressor system.
Supporting bracket is a simple rigid structure in the shape of
an L, one arm of which is fixed to vertical surface, the other
projecting horizontally to support a shelf or other weight.
Natural frequency of supporting bracket is calculated by
performing a modal analysis using the finite element
method. Common name for this type of analysis is finite
element Analysis and failure of the supporting bracket is
mainly due to resonance is quite significant in many
industries, power plant, machineries etc, which leads to the
serious problems in production, efficiency of the system and
also financial losses. Hence performing modal analysis of
those system is unavoidable and important, it is also one of
the remedies to overcome those problems. This analysis
provides the frequency and mode shape for various vibrating
system which helps in improving performance and avoid
damage to system and its surrounding. The modal analysis
of the supporting bracket is performed using ABAQUS
workbench is used as a FEA tool to find the natural
frequencies of the supporting bracket.
Keywords: supporting bracket; free vibration; finite
element Analysis, Abaqus.
1. INTRODUCTION
In mechanical engineering a bracket is any intermediate
component for fixing one part to another, usually larger
part. What makes a bracket a bracket is the fact that it is
intermediate between the two and fixes the one to the
other. Brackets vary wildly in shape, but a prototypical
bracket would be the L-shaped metal piece that attaches a
shelf (the smaller component) to a wall (the larger
component). a vertical arm mounted on the wall, and a
horizontal arm projecting outwards for another element to
be attached on top of it or below it. To enable the
outstretched arm to support a greater weight, a bracket
will often have a third arm running diagonally between the
horizontal and vertical arms, or indeed the bracket may be
a solid triangle. By extension almost any object that
performs this function of attaching one part to another
(usually larger) component is also called a bracket, even
though it may not be obviously L-shaped. In our case the
bracket is used for to supporting the compressor system
mainly used the railways. This bracket is subjected to the
dynamic load so modal analysis is carried out.
1.1 OBJECTIVE FORMULATION
Design for strength with operating requirement of the
equipment.
Modal analysis to find the natural frequency and mode
shapes for the supporting bracket of air compressor
system
Analyze the vibration characteristic of supporting
structure for air compressor
1.2 METHODOLOGY
 Creating the supporting bracket of air compressor
model by CATIA V5
 Mesh Generation by HYPERMESH
 Exporting to ABAQUS
 Applying loads/boundary conditions
 Static analysis due to self weight
 Finding mode shape & Natural frequency
 Visualization
 Validation of Results
1.3 CALCULATIONS
Material properties
Material = ASTM a 36 steel
Young’s modulus = 200 x 103 N/mm2
Density = 7.85x 10-9 tonne/mm3
Poisons ratio = 0.26
Yield strength = 250N/mm2
Factor of safety = 1.5
Total mass = 35.72 kg

Calculation for static analysis
In order to solve the solve this problem, consider the
support bracket of air compressor system as a simple
cantilever beam and load of the air compressor assembly
is applied to cantilever beam.
Formula for calculation
Bending moment
Mb = force x perpendicular distance
Moment of inertia I = (bd3)/12
Bending stress
σb =Mb y/I
Calculation for modal analysis
Deflection of the cantilever beam section [2]
δ =Wa3 + Wa2 (L-a)
3EI 2EI
Natural frequency is given calculated by
fn =1/2Π x√(g / δ)
1.4 FE MODELING
The model is meshed using 2D shell element, Mesh
element size of 5 mm is chosen.
Total Elements : 6661
Total Nodes : 6881
Boundary condition and loads
The 4 bolt location in the vertical arm fixed in all degree of
freedom, C.G point of the motor has taken and motor mass
of 6 kg is applied to that point, Rigid body element is used
on bolt location to create a rigid region. Solis bolt element
are not required, it uses a RBE element to represent bolt,
as shown in Fig. 1.2. Tensile and bending loads can be
transferred through the RBE nodes.
In the Air compressor supporting bracket motor load is
transferred to the support bracket by using rigid element.
Fig-1: Cad Model
Fig-2: Meshed Model
1.5 FEM ANALYSIS
CASE-1 Static analysis due to self weight
Static analysis of the air compressor supporting bracket is
carried out due to self weight.
FEM RESULT
Fig-3: Static Analysis Result
The maximum stress obtained by FEM method is 25.90
N/mm2
The maximum stress obtained by the analytical method is
26.64 N/mm2..
Comparing with the permissible stress of 167N/mm2, the
calculated value 26.64 N/mm2 is less than the permissible
stress. Hence the bracket is safe under self load condition.

CASE-2 Modal analysis of support bracket
Mode shape & Natural frequency
A mode shape is a specific pattern of vibration executed by
a mechanical system at a specific frequency. Different
mode shapes will be associated with different frequencies.
The Analysis technique of modal analysis discovers these
mode shapes and the frequency
.
Fig-4: Mode1 at frequency 24.45 cycle/sec
Fig-5: Mode2 at frequency 123.10 cycle/ sec

The obtained natural frequency of the mode 1is
24.45 cycle/sec
Natural frequency obtained by the analytical method is
21.24 cycle /sec
By comparing the analytical and theoretical the obtained
error is 13.12%
Different modes and corresponding frequency listed
below
Fig-9: Different Modes and Frequency
3. RESULTS
In this project theoretical calculation is done by the above
given formula by considering as cantilever beam and
results are validated with the fem method
Table -1: Results of Support Bracket
FEM
method
Analytical
method
% of
variation
Case-1 Stress-
25.90
26.64 2.77
Case-2 Fn-
24.45
21.24 13.12
4. CONCLUSION
The strength criterion is satisfied with operating
requirement of the equipment
The supporting bracket designed with stands static and
dynamic, as per FEM analysis conducted and the design
which is validated with the analytical.
REFRENCE
[1] Tarundeep singh, Mr dalgeet sing ”dynamic analysis
of compressor mounting bracket ofautomobile air
conditioning system” Feb 2000.
[2] Sangameshwar patil, prabhuling sarasambi,
shravankumar b. kerur “dynamic analysis of composite l-
shaped bracket” June 2005.
[3] Kaori fujita, isao sakamoto, yoshimitsu ohashi and
masahiko kimura” static and dynamic loading tests of
bracket complexes used in traditional timber structures in
japan” June 2004.
[4] Monali Deshmukh, Prof. K R Sontakke” Analysis and
Optimization of Engine Mounting Bracket” Dec. 2001.
[5] Tushar P. Kamble, Rajratna A. Bhalerao”
“Optimization & Modal Analysis of Engine Mounting
Bracket for Different Materials by Using Finite Element
Analysis” August 2003.
[6] A.S. Adkine, Prof.G.P.Overikar and Prof. S .S. Surwase”
static and modal analysis of engine supporting bracket - a
literature review” December 2004.

Modal analysis of Support bracket for air compressor system

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Modal analysis of Support bracket for air compressor system