Why are the maximum ANSYS 8.1 PSD SEQV values 23 time higher than
a competitor's?
It doesn't seem to be an issue with how SEQV is computed from the 1 sigma values, because the component shear stress is very high also  around 9000 psi  so an SEQV value of 19000 is reasonable. Here is how you can hand calculate the variance of a mode per Theory Manual Eqn 17148: Q=Eff Mass x Integral{H(W)^2 x Input spectrum x 386.4^2} H is the transfer function between a sinusoidal excitation W and the natural frequency w. H(W)= 1/(w^2  W^2 + i(2x wW) For the first mode, w = 1929 and H^2 times Input Spectrum can be integrated numerically. For example, at 300 Hz (1885 rads/sec), the transfer function is H(W) = 1/(1929^2  1885^2 + 2x.02x1929x1885) = 3.19e6 The contribution of this mode to the 1 sigma value is the square root of the variance (neglecting modal crossterms.) 

