modal mass and modal stiffness, effective mass and effective stiffness
modal mass and modal stiffness, effective mass and effective stiffness
(OP)
Dear all,
I want to obtain the modal mass and modal stiffness, effective mass and effective stiffness for some modes from my modal analysis in ANSYS.
By default, the modal mass is normallized in ANSYS, then the modal stiffness is equal to the square of natural frequency for a mode. Right?
Could anaybody help me?
Thanks in advance.
Richard
I want to obtain the modal mass and modal stiffness, effective mass and effective stiffness for some modes from my modal analysis in ANSYS.
By default, the modal mass is normallized in ANSYS, then the modal stiffness is equal to the square of natural frequency for a mode. Right?
Could anaybody help me?
Thanks in advance.
Richard





RE: modal mass and modal stiffness, effective mass and effective stiffness
[k(n)] = [omega]^2 . . . (1)
where [omega(n)]^2 is the eigenvalue for mode (n).
also:
[k(n)] = [omega(n)]^2*[M(n)] . . . (2)
where [M(n)] is the modal mass matrix. In ANSYS, the eigenvectors are normalised to the mass matrix by default, such that [M(n)]=1, hence there is a direct relationship between stiffness(es) and eigenvalue(s) given in (1). The modal mass is ported to the output file (jobname.out) post-solution as well as participation factors &c (being the root of the effective mass).
Hope this helps,
-- drej --