can we use CGAP elements to represent gap between two parts(eg: 30mm) in modal and vibration analysis
Hello All,
i want to represent a gap between two parts by using spring (CGAP elements) in both modal and Vibration analysis.
I tried using CGAP elements in my assembly for modal analysis but i could not find any difference of using springs.
with and without springs modal frequencies are same.
If you have any idea please do share your ideas/suggestions.
Thanks in Advance,
Nageswara Rao B
Answers
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Modal and FRF are still linear analysis domain, meaning that it is not possible to consider the NL behavior of the gap elements, as you were expecting.
In modal and FRF, these gaps will act exactly as springs with same stiffness for traction and compression.
The only loadcase that would allow this as NL, would be NL TRansient analysis, but it is very computationally expensive depending on your model, and frequency of interest.
Can you describe better what are you trying to calculate?
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Adriano A. Koga_21884 said:
Modal and FRF are still linear analysis domain, meaning that it is not possible to consider the NL behavior of the gap elements, as you were expecting.
In modal and FRF, these gaps will act exactly as springs with same stiffness for traction and compression.
The only loadcase that would allow this as NL, would be NL TRansient analysis, but it is very computationally expensive depending on your model, and frequency of interest.
Can you describe better what are you trying to calculate?
How it would be to perform a nl static analysis with gap elems and defining this nl subcase as preload under normal modes step sir @Adriano A. Koga ? I'm confused about the non-linearities in lineer dynamic analyses since I see an article of a Nastran expert such this:
https://www.eng-tips.com/viewthread.cfm?qid=325574
Even though if it is ok to define gap elems i.e. with a initial gap of 2mm ; this gaps aren't at the opposite side of the small displacement theory?
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