What does a complex eigenvector output from QRDAMP mean, and can you provide an example?
At 9.0, the complex eigenvector can be requested with MODOPT,QRDAMP,,,,,ON using the QR Damped eigenvalue extraction method. This type of output was already available in the past with DAMP or UNSYM methods. Essentially, complex eigenvector output implies that there is phase difference, analogous to harmonic analysis output. Combining the real and imaginary results with a userdefined macro (use ANHARM.MAC in the "apdl" subdirectory as a starting point, for example) will aid the user in visualizing the timevarying response. For proportional damping (such as with alpha and/or beta damping), since there is no phase difference, the imaginary eigenvector will essentially be zero. For nonproportional damping, however, the imaginary eigenvector will be nonzero. An example of a simple beam is shown below:  finish /clear NO_ELEM = 20 /prep7 et,1,3 r,1,1,1/12,1 mp,ex ,1,10e6 mp,dens,1,0.1/386.1 n,1,0,0,0 n,2,100,0,0 fill,1,2,NO_ELEM,3,1 type,1$real,1$mat,1 e,1,3 e,NO_ELEM+2,2 e,3,4 *repeat,NO_ELEM1,1,1 et,2,14 keyopt,2,2,2 r,2,,1e1 nsel,s,node,,node(33,0,0) cm,TEMPNODE,node ngen,2,100,all type,2$real,2 eintf cmsel,u,TEMPNODE d,all,all et,3,14 keyopt,3,2,2 r,3,,5e1 nsel,all nsel,s,node,,node(66,0,0) cm,TEMPNODE,node ngen,2,101,all type,3$real,3 eintf cmsel,u,TEMPNODE d,all,all allsel,all finish /solu antype,modal modopt,qrdamp,10,,,yes mxpand,10 d,1,all allsel,all solve finish /post1 set,1,2 pldisp,2 *afun,deg *get,MY_DSCALE,graph,1,dscale,dmult /user,all /dscale,all,MY_DSCALE /seg,dele /seg,multi lcdef,1,1,2,0 lcdef,2,1,2,1 *do,MY_ANGLEINCR,0,330,30 /com, angle: %MY_ANGLEINCR% REAL_COMP=cos(MY_ANGLEINCR) IMAG_COMP=(sin(MY_ANGLEINCR)) lcfact,1,REAL_COMP lcfact,2,IMAG_COMP *if,REAL_COMP,eq,0,then lcfact,1,1e10 *endif *if,IMAG_COMP,eq,0,then lcfact,2,1e10 *endif lcase,1 lcoper,add,2 /replot *enddo /com, loop finished /seg,off anim,12,1,0.2  

