My 10-node tet (SOLID168) model seems to output the wrong CG
(center of gravity) information in the d3hsp file for each part. Why?
This appears to be an obvious bug in the 5434 build of LS970. LSTC Technical Support was notified on February 3rd, 2005. This should be fixed in an upcoming build of LS-DYNA, if possible. There may be some inherent limitation with the element that prevents outputting the correct value. The good news is that the mass calculation seems to be accurate and the CG information that is printed out is probably not used internally by the code. If additional details become known concerning this issue, they will be posted in this solution. In the example below, there are two blocks, one centered at (0,-1.5,0) and made of bricks and one at (0,1.5,0) and made of tets. The 1st is fine, and gives even better results in double precision, but the 2nd (tet block) gives poor results and shows no improvement in double precision. = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = fini /clear /view,,1,2,3 /plopts,info,1 /title, CG Test in ANSYS LS-DYNA /prep7 et,1,SOLID164 et,2,SOLID168 r,1 mp,ex,1,30.0e6 ! Young's modulus, psi. mp,nuxy,1,0.30 ! Poisson's ratio, unitless. mp,dens,1,0.0007 ! mass density, lbf-sec^2/in^4 block,-1,1,-2,-1,-1,1 ! CG at (0,-1.5,0) block,-1,1,1,2,-1,1 ! CG at (0,1.5,0) esize,0.25 type,1 vmesh,1 type,2 vmesh,2 eplot fini /solu time,0.0001 edrst,10 edhtime,10 edopt,add,,both d,all,ux,0.0,,,,uy,uz eddbl,double ! comment out for single precision ... save solve save fini /eof = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Single Precision Results: ========================= Date: 02/03/2005 Time: 16:34:30 ___________________________________________________ || | Livermore Software Technology Corporation | | || 7374 Las Positas Road| | Livermore, CA 94551 | | Tel: (925) 449-2500 Fax: (925) 449-2507 | | <a target=_blank href="http://www.lstc.com">http://www.lstc.com</a>http://www.lstc.com | |_________________________________________________| | | | LS-DYNA, A Program for Nonlinear Dynamic | | Analysis of Structures in Three Dimensions| | Version: 970 Date: 07/30/2004 | | Revision: 5434 Time: 15:01:01 | | | | Features enabled in this version: | | ANSYS Database format | | Shared Memory Parallel | | | | Licensed to: | | | | Platform : | | OS Level : WINDOWS XP | | Hostname : pghxpdciabat4 | | Precision : Single precision (I4R4) | | | | Unauthorizeduse infringes LSTC copyrights | |_________________________________________________| ******************************************************************************** m a s s p r o p e r t i e s o f p a r t # 1 total mass of part = 0.27999885E-02 x-coordinate of mass center = 0.20423112E-07 y-coordinate of mass center =-0.15000001E+01 z-coordinate of mass center =-0.12992835E-08 inertia tensor of material row1= 0.1225E-02 -0.8555E-10 -0.6821E-12 row2= -0.8555E-10 0.1925E-02 -0.2071E-09 row3= -0.6821E-12 -0.2071E-09 0.1225E-02 principal inertias i11 = 0.1225E-02 i22 = 0.1925E-02 i33 = 0.1225E-02 principal directions row1= 0.1000E+01 -0.1222E-06 -0.1465E-02 row2= 0.1226E-06 0.1000E+01 0.2957E-06 row3= 0.1465E-02 -0.2959E-06 0.1000E+01 ******************************************************************************** m a s s p r o p e r t i e s o f p a r t # 2 total mass of part = 0.27999992E-02 x-coordinate of mass center =-0.18247974E-02 y-coordinate of mass center =-0.73751835E-02 z-coordinate of mass center =-0.40418007E-02inertia tensor of material row1= 0.8649E-04 0.1336E-06 -0.9997E-06 row2= 0.1336E-06 0.7841E-04 -0.2711E-06 row3= -0.9997E-06 -0.2711E-06 0.9025E-04 principal inertias i11 = 0.8624E-04 i22 = 0.7841E-04 i33 = 0.9051E-04 principal directions row1= 0.9701E+00 -0.1384E-01 -0.2422E+00 row2= 0.8161E-02 0.9997E+00 -0.2442E-01 row3=0.2424E+00 0.2172E-01 0.9699E+00 ******************************************************************************** m a s s p r o p e r t i e s o f b o d y total mass of body = 0.55999998E-02 x-coordinate of mass center =-0.91239851E-03 y-coordinate of mass center =-0.75368762E+00 z-coordinate of mass center =-0.20209064E-02 inertia tensor of body row1= 0.4431E-02 0.3947E-05 -0.1010E-05 row2= 0.3947E-05 0.2003E-02 0.8175E-05 row3= -0.1010E-05 0.8175E-05 0.4434E-02 principal inertias of body i11 = 0.4430E-02 i22 = 0.2003E-02 i33 = 0.4435E-02 principal directions row1= 0.9706E+00 -0.1627E-02 -0.2406E+00 row2= 0.2389E-02 0.1000E+01 0.2873E-02 row3= 0.2406E+00 -0.3363E-02 0.9706E+00 *****************-02 z-coordinate of mass center =-0.40418134E-02 inertia tensor of material row1= 0.8649E-04 0.1336E-06 -0.9997E-06 row2= 0.1336E-06 0.7841E-04 -0.2711E-06 row3= -0.9997E-06 -0.2711E-06 0.9025E-04 principal inertias i11 = 0.8624E-04 i22 = 0.7841E-04 i33 = 0.9051E-04 principal directions row1= 0.9701E+00 -0.1384E-01 -0.2422E+00 row2= 0.8162E-02 0.9997E+00 -0.2442E-01 row3= 0.2424E+00 0.2172E-01 0.9699E+00 ******************************************************************************** m a s s p r o p e r t i e s o f b o d y total mass of body =0.56000000E-02 x-coordinate of mass center =-0.91239862E-03 y-coordinate of mass center =-0.75368759E+00 z-coordinate of mass center =-0.20209067E-02 inertia tensor of body row1= 0.4431E-02 0.3947E-05 -0.1010E-05 row2= 0.3947E-05 0.2003E-02 0.8175E-05 row3= -0.1010E-05 0.8175E-05 0.4434E-02 principal inertias of body i11 = 0.4430E-02 i22 = 0.2003E-02 i33 = 0.4435E-02 principal directions row1= 0.9705E+00 -0.1627E-02 -0.2411E+00 row2= 0.2390E-02 0.1000E+010.2872E-02 row3= 0.2411E+00 -0.3364E-02 0.9705E+00 ******************************************************************************** = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = . |
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