Natural Frequency Design Calculations
Natural Frequency Design Calculations
(OP)
"I am a design engineer working on a multidisciplened project. I am trying to design a welded sheetmetal box that will contain a heat exchanger. The box is attached to a turbine that is producing a certain frequency. The turbine is used to create a gas flow through the heat exchanger. What formulas are there to predict the natural frequency of the sheetmetal box (if I coin stiffinening ribs or panels into the sheetmetal)? I can calculate the natural frequency of the flat panels but I have found no help in any further calculations or design guides.
Any help would be appreciated.
Thank you,
Bill";
Any help would be appreciated.
Thank you,
Bill";





RE: Natural Frequency Design Calculations
The frequencies at the steady-state turbine speed are usually of greatest interest, but the start-up and shutdown frequency ramps should also be considered.
The box natural frequencies should well separated from the forcing frequencies, in order to avoid resonance.
Hand calculations are useful as a first approximation.
You will probably need to make a finite element model of the box system, however, in order analyze the box natural frequencies and mode shapes more accurately.
A good, practical reference is:
V. Adams and A. Askenazi, Building Better Products with Finite Element Analysis, OnWord Press, Santa Fe, N.M., 1999.
Available from:
http://www.amazon.com/exec/obidos/ASIN/156690160X/vibrationdata-20/002-5686648-3842444
Sincerely, Tom Irvine
Email: tomirvine@aol.com