Mode Shapes in Abaqus

Question

Mode Shapes in Abaqus

sheila (Materials)

(OP)

21 Jan 02 01:40

Hi,
I analyzed a mainframe and engine of motorcycle using ABAQUS to get natural frequencies and modeshapes. The natural frequencies I got are quite similar to the experimental results. But why the mode shapes are look different?What are the reasons for that?

brad (Mechanical) · Answer 1 · 2002-01-21 12:24:31

Any number of reasons. As you have not explained what method you used to obtain the FEA frequencies, I will presume that you used an eigenvalue extraction.

The most likely reason for differences is that your experimental approach was not 'apples-to-apples' with a the eigenvalue extraction procedure.

Experimental frequency tests usually are hammer-test or forced-frequency tests. You may want to try and find the numerically-equivalent approach to what your experimental test actually is doing.

Lacking more details than you have provided, I can't be more specific than that.

Brad

sheila (Materials) · Answer 2 · 2002-01-22 20:25:25

To Brad,
Thank you for replying. Actually,we performed Modal Analysis using hammer and shaker.I then used Lanszos solver to get the FEA frequencies.:)

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Mode Shapes in Abaqus