how does ANSYS scale the eigenvalue shape ?

[frisbee]

I am using the upcoord command to induce an imperfection on
a beam in order to do a buckling analysis..
Is ANSYS multiplying the factor that I am specifying with the max value (1) of one of the categories DOF UY or UZ or is it taking USUM as the reference ?

Thanks, Timo

 

[FeaGuru]

Your question seems quite confusing and I think you are confused.

First, the eigenvalue is a proportionality factor for the critical load. The eigenvector is the shape of the deformed geometry, but only the shape and not real deformation.

Second, I do not understand why you apply an imperferfection on an eigenvalue buckling solution. This is not necessary as what is happening is the sum of the geometric and tangent stiffness matrix = 0 allows you to find the eigenvector and eigenvalue. You would apply an imperfection is you were to solve the problem using a nonlinear analysis.

Third, to find the critical load (buckling load) mulitply the load you applied by the eigenvalue.

I do not know if this is what you were after, but the question can not be answered as you posed it.