Relationship between structures Natural Frequency and Contact Mechanics
Relationship between structures Natural Frequency and Contact Mechanics
(OP)
I understand that techniques such as FEA can be used to the mode shapes and natural frequencies of structures. I am wondering if finding out the mode shapes and natural frequencies can help in providing any information or inclination of the the materials ability to cope with contact conditions? I understand that contact conditions depending on the properties and geometry of both (or more) bodies in contact. However, I am think purely on based on comparing the same structure with different material properties. I would really appreciate any discussion and input on this. Thanks.





RE: Relationship between structures Natural Frequency and Contact Mechanics
Why don’t you explain to us how you think the two different analyses might be remotely related? Obviously, if you had sufficient vibration so as to eliminate contact for periods/intervals of time you would have some sort of a peening action rather than constant contact. If you had dynamic actions which caused the two bodies to move w.r.t. each other, at the contact point, you would have wear, fretting and the like. Otherwise, it seems to me that they are two pretty distinct concerns and analyses. I don’t get the connection you are imagining.
RE: Relationship between structures Natural Frequency and Contact Mechanics
Are the two structures touching each other or are they clamped together?
Is your FEA capable of understanding contact forces in compression, but not tension? Can it deal with separation of the two structure?
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JHG
RE: Relationship between structures Natural Frequency and Contact Mechanics
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RE: Relationship between structures Natural Frequency and Contact Mechanics
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RE: Relationship between structures Natural Frequency and Contact Mechanics
I am just brainstorming here and trying to think outside the box. All you comments and input is very much appreciated. I will try to give an example. Lets say we have a structure with a very complex range of material properties i.e. each element of the FE model has assigned a different material property (Youngs modulus, Poisson's ratio and density). If then it becomes very difficult to create an assembly of and conduct a contact analysis then how else could we assess the structures performance under contact in relation to the same structure with different material properties. As suggested by electricpete we could compare the stiffness of each structure.
dhengr: Sorry, I do not have a sensible answer to your question.
drawoh: The components would not be clamped, but touching e.g. a ball in socket joint. In terms of contact forces, it would be conducted using the contact algorithms in Abaqus.
I really enjoyed reading your kind comments and input, thank-you again.
RE: Relationship between structures Natural Frequency and Contact Mechanics
If all the components in your structure have different Young's Moduli and Poisson's ratios, you just punch the values into your software. Your fabricator is going to hate you. I see no problems doing analysis.
A ball and socket joint is fully clamped in a truss. If a beam is free to rotate, I don't know how FEA can analyse it.
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JHG
RE: Relationship between structures Natural Frequency and Contact Mechanics
There are ways around this - you could consider a 50% duty cycle contact as being a bit like a compliantly mounted pin joint, but that would be very application, and excitation specific. Generally contacts create 3rd, 5th etc harmonics which of course a simple k/m analysis can't even begin to consider.
Cheers
Greg Locock
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RE: Relationship between structures Natural Frequency and Contact Mechanics
RE: Relationship between structures Natural Frequency and Contact Mechanics
Many years ago I learned of a way of faking contact by using constraint equations between the nodes on the two contacting surfaces. I don't remember too much about the details thoug since I have never used it again since then,
However, if your contact problem involves static loads you can simply run a static analysis with contact.
RE: Relationship between structures Natural Frequency and Contact Mechanics