The mode shapes that ANSYS 8.1 gives for displacement controlled
buckling appear to be wrong. Is this a known error?
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Yes. Defect 25718 (see below) was filed and subsequently corrected in the daily build of ANSYS 9.0 on August 16th, 2004. A Class 3 Error report is being generated and will be distributed when complete. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Defect 25718 ========= Mode shapes for displacement controlled buckling appear wrong ============================================= Section 7.5.2. "Obtain the Static Solution" in the ANSYS 8.1 Structural Analysis Guide reads as follows: You can apply a nonzero constraint in the prestressing pass as the static load. The eigenvalues found in the buckling solution will be the load factors applied to these nonzero constraint values. However, the mode shapes will have a zero value at these degrees of freedom (and not the nonzero value specified). Therefore, the applied Z-direction displacement at the Z=0 location should NOT be given as the mode shape displacement for the attached input. FINISH /CLEAR,START,1 /plopts,info,1 ! arg1 = dispacement !!! arg1=0.01 !!! arg1=0.50 arg1=1.00 !!! arg1=10.0 *if,arg1,eq,0,then arg1=0.5 *endif ! Units: mm, ton, second, Newton, Mpa, ... /PREP7 w=100 h=20 t=1 l=200 ET,1,181 R,1,t MP,EX,1,205000 MP,NUXY,1,0.30 mp,dens,1,7.83e-9 K,1 K,2,w KGEN,2,1,2,1,,h l,1,3 l,3,4 l,4,2 KGEN,2,4,4,1,0,0,-l l,4,5 ADRAG,1,2,3,,,,4 ESIZE,5*t AMESH,ALL SAVE FINISH /SOLUTION ANTYPE,STATIC PSTRESS,ON outres,all,all LSEL,S,LOC,Z,-l-0.05,-l+0.05 NSLL,S,1 D,ALL,UZ,0 D,ALL,ROTZ,0 ALLSEL LSEL,S,LINE,,8 NSLL,S,1 D,ALL,UY,0 ALLSEL LSEL,S,LINE,,5 LSEL,A,LINE,,10 NSLL,S,1 D,ALL,UX,0 ALLSEL LSEL,S,LINE,,2 NSLL,S,1 D,ALL,UY,0 ALLSEL LSEL,S,LINE,,1 LSEL,A,LINE,,3 NSLL,S,1 D,ALL,UX,0 ALLSEL LSEL,S,LOC,Z,0 NSLL,S,1 D,ALL,UZ,-arg1 ALLSEL SAVE SOLVE save FINISH /SOLUTION ANTYPE,BUCKLE BUCOPT,LANB,1 MXPAND,1,,,yes SOLVE save FINISH /post1 SET,,, ,,, ,1 /VIEW,1,1,1,1 /ANG,1 /DSCALE,1,1.0 /title, Note Z displacement at Z=0 location ... /show,jpeg plns,u,sum /show,close /show,term /replot /eof . |
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