Is the 1-sigma random vibration (PSD) EPELEQV (equivalent strain) computed like the Segalman-Reese SEQV (equivalent stress)?
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No. It is computed on a mode-by-mode basis and is summed directly (similar to how load case combinations are done with SUMTYPE,PRIN), so the value is an upper bound. This 1-mode test shows that EPELEQV is computed from the modal results (factored by the mode coefficient) and matches the EPELEQV reported for load step 3. /prep7 et,1,42 mp,ex,1,1e4 mp,nuxy,1,.3 mp,dens,1,.0025 rect,,10,,1 esize,1 amesh,1 nsel,s,loc,x,0 d,all,ux,0 nsel,r,loc,y,0 d,all,uy,0 nsel,all fini /solu antype,modal modop,lanb,1 mxpand,1,,,yes solve fini /solu antyp,spectrum spopt,psd,,yes psdfrq,1,,1,10,100,1000 psdval,1,1,1,1,1 nsel,s,loc,x,0 d,all,uy,1 nsel,all pfact,1 psdcom solve fini /post1 *get,var1,mode,1,mcoef sig1=sqrt(var1) set,1,1,sig1 nsel,s,loc,x,0 prnsol,epel,prin set,3,1 nsel,s,loc,x,0 prnsol,epel,prin |
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