Please understand this following para which is given in the webpage you mentioned:
"The response of the structure is different at each of the different natural frequencies. These deformation patterns are called mode shapes. Now we can better understand what Modal Analysis is all about - it is the study of the natural characteristics of structures. Both the natural frequency (which depends on the mass and stiffness distributions in my structure) and mode shape are used to help design my structural system for noise and vibration applications. We use Modal Analysis to help design all types of structures including automotive structures, aircraft structures, spacecraft, computers, tennis rackets, golf clubs, ..."
Explaination:
The modal analysis gives the natural frequencies and corresponding mode shapes
(displacement patterns) for the structure. We can only come to know the pattern
of displacement, not the quantity. If there is any forcing frequency matching
with any of the natural frequencies calculated from modal analysis, the
structure will vibrate with very large amplitudes in that mode shape (resonance
will occur). The natural frequencies calculated from modal analysis are used to
check the same. But there is no force involved in the modal analysis and it is
just the calculation of natural frequencies and mode shapes depending on mass
and stiffness distribution of the structure.
As natural frequency of the structure depends only on the mass and stiffness
distribution of the structure. If the stiffness is more the natural frequncy
will be more.
I hope now there is clear difference in modal analysis and harmonic analysis.
Regards,
Kaustubh
>>> andoks_lichon@yahoo.com.au 08/08/02 10:14PM >>>
try mpiuk.com.uk or do
google search for modal analysis and then surf the SEM website.
download pdf Peter lecture note (he's the director of the modal
analysis and control lab down at Univ. massachuset -lowell) titled
please explain modal analyis.
while your're at it have a look also at the mode shape and operating
deflection shape. some nice vib mode animation can also be
downloaded from the web.
for the nuts and bolts of modal analysis check out chapter 21 of harris shock and vibration handbook. of interest is the way modal analysis is evolving due to the development of dsp and vib. probe.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/ Received on Fri Aug 09 01:18:00 2002
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