Exciting at nodal point
Exciting at nodal point
(OP)
Hey all,
I have a question about resoance frequency on a simple cantilever beam. I am wondering what would happen if I excite a beam at a nodal point.
I am tryig to understand the mode shapes at different frequencies. I know this can be done by a simple modal analysis, by using accelerometer and impulse hammer. If I excite the beam near a nodal point how will the mode vectors change w.r.t exciting at antinodal point.
Thanks
Deepak
I have a question about resoance frequency on a simple cantilever beam. I am wondering what would happen if I excite a beam at a nodal point.
I am tryig to understand the mode shapes at different frequencies. I know this can be done by a simple modal analysis, by using accelerometer and impulse hammer. If I excite the beam near a nodal point how will the mode vectors change w.r.t exciting at antinodal point.
Thanks
Deepak





RE: Exciting at nodal point
If you excite at a node point of a particular mode shape you simply are not exciting that mode. (but you are exciting others)
I don't think that will work with a hammer test though. You will always get the sums in this case.
Fe
RE: Exciting at nodal point
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Exciting at nodal point
- Steve
RE: Exciting at nodal point
The screwdriver test is the ideal tool for locating the rear mount on a longitudinal installation, sadly the Health and Safety implications mean that an accelerometer survey is more appropriate (and I grudgingly admit might give more useful results).
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Exciting at nodal point
Nodal points will change for every frequency at which you are exciting the beam (different mode shapes). However, I would like to know how do you know beforehand where the nodal point will be with a hammer hit for different frequencies? I think a shaker will be more useful.
Thanks
Mert
http://www.novosim.com
Product Development Services (cad/cae/test)
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RE: Exciting at nodal point
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Exciting at nodal point
http://www.novosim.com
Product Development Services (cad/cae/test)
Medical Device R&D
RE: Exciting at nodal point
For mode2 the node is at 78%
For mode3 the nodes are at 50% and 87%