hello,

i was trying to run an APDL PSD analysis but with a material dependent damping which means i defined the damping in the modal analysis using the QR damped method. to consider the material damping on MODOPT the CPXmod must be =yes. in this case the solutions are complex where the real part is the stability of the system and the imaginary part is the natural frequency (figure1). however when running the PSD analysis it always considers the real part of the modal solution which is the stability not the natural frequency which leads to wrong results, to confirm that i desactivated the CPXmod option and compared the two (figure 2&3).

so my question is, is it possible to force the PSD analyses to use the imaginary part of the modal solution ? knowing that i ran the same model under workbench and it runs perfectly.

thank you