Design of Semi-Automatic Vibration Absorber by using FEA

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 2718
Design of Semi-Automatic Vibration Absorber by using FEA
R. S. Autade1, S. A. Pawar2, A. B. Atpadkar3
1 Asst. Professor, Dept. of Mechanical Engineering, Fabtech college of engg., Maharashtra, India.
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Abstract – When any elastic body such as spring, shaft or
beam, is displaced from the equilibrium position by the
application of external forces & then released, it commences
cyclic motion. Such cyclic motion of body or a system, due to
elastic deformation under the action of external forces, is
known as vibration.
The dual mass vibration absorber can be effectively used to
reduce the vibration of the beam. This absorber is tuned to
excitation frequency by moving the dual masses in or out
easily. The experimental result shows that around the
absorber attachment location the vibration of beam become
negligible. This absorber also reduces the vibration of beam
other than attachment point.
Key Words: Active DVA, passive DVA, mode shapes etc.
1. INTRODUCTION When any elastic body such as
spring, shaft or beam, is displaced from the equilibrium
position by the application of external forces & then
released, it commences cyclic motion. Such cyclic motion
of body or a system, due to elastic deformation under the
action of external forces, is known as vibration.
When machines are operating they create
vibrations. In some cases these vibrations have a negative
influence on the performance of the machine. For instance,
in a milling machine the whole construction vibrates when
the tool rotates and material is cut. This can have a
negative impact on the precision of the manufactured
products, the lifetime of the machine and the environment.
A solution to this problem can be found in the application
of dynamic vibration absorber (DVA). A DVA is a
construction that can be mounted on the vibrating
machine and which is connected to a controller. Whenever
the vibration characteristics of the machine change, the
controller adjusts the DVA so that the vibrations get
damped as good as possible. The aim is to design active
DVA.
1.1 PRINCIPLE OF ABSORBER:
As shown in Fig 1.1 a sinusoidal force Fosinwt acts on an
undamped main mass-spring system (without the
absorber mass attached).When the forcing equal the
natural frequency of the main mass the response is infinite
Fig 1.1 Principal of vibration absorber
This is called resonance, and it can cause server problems for
vibrating system. When an absorbing mass-spring system is
attached to main mass and the resonance of the absorber is
tuned to match that of the main mass, the motion of the main
mass is reduced to zero at its resonance frequency. Thus, the
energy of the main mass is apparently "absorbed" by the

tuned dynamic absorber.
1.2 APPLICATION
Fig 1.2 Application of vibration absorber to reduce the
vibrations of variable speed pump
The application of a TVA for suppression of chatter
vibrations in the boring manufacturing process is
presented. The boring bar is modeled as a cantilever
Euler–Bernoulli beam and the TVA is composed of mass
and spring and dashpot elements.
Fig 1.3 Application of vibration absorber to reduce the
vibrations of boring bar
2.1 MODAL ANALYSIS OF ABSORBER
In order to gain an accurate prediction of the
modes of the absorber, a numerical analysis using finite
elements was used. This analysis allows determination of
the resonance frequency of each mode, which will be a
function of the location of the mass along the two shafts.
The suitability of this element was based on its bending
and membrane properties. For the modeling of the two
shafts, absorber masses & housing SOLID92, tetrahedral
was used. More detail can be found within the ANSYS
manuals.
Fig 2.1 Solid92 3-D-Node tetrahedral structural
solid.
SOLID92 is well suited to model of irregular
meshes. The element is defined by 10 nodes having three
degree of freedom at each node translations in the nodal in
x, y, and z direction.
The boundary conditions were then programmed
by fixing (in all directions) one side of the square housing.
Note that one of the shafts will be threaded and the other
is smooth. When absorber is turned, the end masses will
move in or out.
Dimension and properties of the absorber
Length of rod = 160mm,
Diameter of rod = 6mm,
Length of mass = 25mm,
Diameter of mass = 40mm,
Density of material = 7800 kg/m3,
Modulus of elasticity =200Gpa
2.1.1 Analysis of absorber
Fig 2.2 shows the mode shape of absorber for the
first six natural frequencies. For the first two mode shapes
masses moves laterally in horizontal direction. For the first

mode shape the mass moves out of phase and for second
mode shape move in phase
Fig 2.2a) First mode shape at frequency 49.8 Hz
Fig 2.2 b)Second mode shape at frequency 49.9Hz
For the third and fourth mode shapes masses moves in
vertical direction. For the third mode shape the mass
moves out of phase and for fourth mode shape move in
phase
Fig 2.2 c) Third mode shape at frequency 97.3 Hz
Fig 2.2d)Fourth mode shape at frequency 99.27Hz
For the fifth, sixth mode shapes the masses are in torsion.
For the fifth mode shape the mass moves out of phase and
for sixth mode shape move in phase
Fig 2.2 e) Fifth mode shape at frequency 279.1Hz
Fig 2.2 f) Sixth mode shape at frequency 279.1 Hz
Fig 2.2: Mode shapes of dual mass absorber for first six
natural frequencies.
Table 1: Frequencies for different mass position along rod
length

Mass
pos.
in mm
Frequency (Hz)
1 2 3 4 5 6
130 49.88 49.94 97.36 99.27 27.17 279.18
125 51.79 51.86 101.48 103.5 283.69 283.71
120 54.35 54.42 107.05 109.3 289.70 289.72
115 57.13 57.21 113.15 115.69 296.17 296.19
110 60.10 60.19 119.85 122.68 303.08 303.11
105 63.31 63.41 127.23 130.42 310.53 310.61
From table it is seen that for different mass positions from
outside to inside frequency goes on increasing and vice
versa. In this table shows first
six frequencies for various position
Fig. 3 Dual Mass Vibration Absorber
Fig. 2.3 Graph of variation of frequency
(Displacement in microns) with distance
(position) of masses.
CONCLUSIONS: The dual mass vibration absorber can
be effectively used to reduce the vibration of the beam.
This absorber is tuned to excitation frequency by moving
the dual masses in or out easily.
REFERENCES
1. K. Aso,* K. Kan,, “Effects Of Vibration Absorbers On
The Longitudinal Vibration Of A Pipe String
In The Deep Sea - Part 1”, International journal of
Offshore and Polar engineering.
2. Yuri Khazanov, “Dynamic Vibration Absorbers
Application with variable speed machine”, Pump
and systems 119 2007, 114-119
3. H.Moradia, F. Bakhtiari-Nejadb, “Tuneable
vibration absorber design to suppress vibrations:
An application in boring manufacturing process”.
Journal of sound and vibration 318 (208) 93-108
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