Forced Vibration

1. Prepared by : Darawan Abdulwahid E-mail : darawan.me@gmail.com
Prepared by : Darawan Abdulwahid E-mail : darawan.me@gmail.com
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University of salahaddin | college of Engineering | Mechanical Department
Experiment NO.4
“Forced Vibration”
Prepared by :Darawan Wahid Rahman
Group : A1
Date: 26-Feb-2016

2. Prepared by : Darawan Abdulwahid E-mail : darawan.me@gmail.com
Prepared by : Darawan Abdulwahid E-mail : darawan.me@gmail.com
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Experiment NO.4 | “Forced Vibration”
Theory
Forced vibrations occur if a system is continuously driven by an external agency. A simple
example is a child’s swing that is pushed on each downswing. Of special interest are systems
and driven by sinusoidal forcing. This leads to the important phenomenon of resonance.
Resonance occurs when the driving frequency approaches the natural frequency of free
vibrations.
Forced vibration is when a time-varying disturbance (load, displacement or velocity) is
applied to a mechanical system. The disturbance can be a periodic and steady-state input, a
transient input, or a random input. The periodic input can be a harmonic or a non-harmonic
disturbance. Examples of these types of vibration include a washing machine shaking due to an
imbalance, transportation vibration caused by an engine or uneven road, or the vibration of a
building during an earthquake. For linear systems, the frequency of the steady-state vibration
response resulting from the application of a periodic, harmonic input is equal to the frequency
of the applied force or motion, with the response magnitude being dependent on the actual
mechanical system.
Procedure
My tools or components that consist of two main types (hardware & software).
At first I set the hardware components (which shown in Figure.1 on page 7) ,which consist of a
table and an aluminum beam which connected over the table and a Hand-held Exciter which
connected over the beam at the end of it , and a Force transducer which located between the
beam and the Hand-held Exciter , and an Accelerometer which connected at the center of the
beam . And a Data acquisition which receives all reaction from the accelerometer which
connected with the Data acquisition via cable at channel 1 and the Force transducer (load cell)
via cable at channel 2 the Hand-held Exciter at the out put port via cable . After converting send
the signals from the Data acquisition to the PC. In the PC we have a software, which named by
Pulse Lab. Shop which is control these signals and show us the result form a value and curve
which (shown on figure .2 at the last page).

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*Hardware :
Accelerometer (Type 4507): Accelerometer Types 4507 and 4508 are specifically designed to
withstand rough environments. A combination of high sensitivity, low mass and small physical
dimensions makes them ideal for modal measurements such as automotive body and power-
train ones as well as for modal analysis on aircraft, trains and satellites.
Specifications :

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Prepared by : Darawan Abdulwahid E-mail : darawan.me@gmail.com
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Data acquisition: is the process of sampling signals that measure real world physical conditions
and converting the resulting samples into digital numeric values that can be manipulated by a
computer. Data acquisition systems, abbreviated by the acronyms DAS or DAQ, typically
convert analog waveforms into digital values for processing. Data acquisition applications are
usually controlled by software programs developed using various general
purpose programming languages such
as Assembly, BASIC, C, C++, Fortran, Java, LabVIEW, Lisp, Pascal,Pulse Lab. Shop, etc.. we have
more type of Accelerometer, but in this experiment we worked with (model-7539_A)

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8230 - Force transducer IEPE, 110 mV/N
[Load cell : measure force procedure]
Specifications

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Hand-held Exciter — Type 5961
Specifications 5961
NPUT VOLTAGE:
2.0 VRMS (Distortion <3%)
3.5 VRMS (Max input)
BATTERY LIFETIME:
Approx. 3 hours constant use
DIMENSIONS:
Length:
155mm (6.1in)
Diameter:
52 mm (2.05 in)
Weight:
500 grams including battery (17 oz.)
FREQUENCY RANGE:
45 Hz to 15 kHz
SENSITIVITY:
150 mN/Vin (typical and broadband) where
Vin= 2.0 Volt RMS, Load mass = 2 kg.
FORCE RATING (RMS)
2N (typical at resonance)
100 mN (typical at 10 kHz)
See graph of Force vs. Frequency

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Figure.1 ( The procedure setting )