modal analysis

[G.mallesh]

hi

I have run a modal analysis for box assmbly using abaqus, i am getting 1st 5 modes on one of the plate are very low frequencies(in terms of 10s) where as if i run same plate without assmbly(single part with assembly constraint) i am getting mode frequencies in 100s (it seems to be correct theoritically). i am using same bc, matl prop and Mesh is fine. what could be the reason. mode shapes are matching. for assembly i have used fastener option in interactions.

 

[FEA way]

Do the boundary conditions in the single part (plate) model represent they way this plate’s motion is restricted in the assembly ? Otherwise it would be a different structure and thus resulting in different eigenfrequencies.

 

[G.mallesh]

Ya I have given similar boundary condition for part which represents same as assembly

 

[bkal]

You cannot expect us to help you if you do not give us more information. Show us both models and boundary conditions applied to them. Unless you have changed material properties between two models, b.c. are the most likely reason.