虚拟质量法
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各位高手，我是nastran的初学者，现在遇到一个问题，在应用虚拟质量法求
湿模态问题时，按照例子做能计算出结果，但换一个对象用同样的步骤做时就会出现下面的错误，从而计算不出结果。*** SYSTEM WARNING MESSAGE 6731 (SDCBOD)
ROW 244 OF LOWER TRIANGULAR FACTOR HAS DIAGONAL TERM = 0( OR .LT. 0 IF CHOLESKY )
*** USER INFORMATION MESSAGE 4158 (SDCBOD)
STATISTICS FOR CHOLESKY DECOMPOSITION OF DATA BLOCK SCRATCH FOLLOW
NUMBER OF NEGATIVE TERMS ON FACTOR DIAGONAL = 0
MAXIMUM RATIO OF MATRIX DIAGONAL TO FACTOR DIAGONAL = 7.5E+00 AT ROW NUMBER 169
*** USER WARNING MESSAGE 4645 (REIG)
THE SHIFTED STIFFNESS MATRIX IS NOT POSITIVE DEFINITE IN MGIVENS METHOD.
*** USER FATAL MESSAGE 4405 (PRTPRN)
NO EIGENVECTORS COMPUTED FOR COMPONENT MODE SYNTHESIS OR SYSTEM SOLUTION.
我所做的对象是一个轴向沿x轴，底面半径为0.2m，高为20m的长杆，使其完全浸没在水中，自由液面应当大于0.2m，而当自由液面选为大于0.2m时，就会出现上面的错误，当自由液面选为小于0.2m时就能计算出结果。我现在不知道到底是哪里出现问题，现将我做的bdf文件以附件形式给出，请各位高手帮帮忙，先谢谢了。
ROW 244 OF LOWER TRIANGULAR FACTOR HAS DIAGONAL TERM = 0( OR .LT. 0 IF CHOLESKY )
*** USER INFORMATION MESSAGE 4158 (SDCBOD)
STATISTICS FOR CHOLESKY DECOMPOSITION OF DATA BLOCK SCRATCH FOLLOW
NUMBER OF NEGATIVE TERMS ON FACTOR DIAGONAL = 0
MAXIMUM RATIO OF MATRIX DIAGONAL TO FACTOR DIAGONAL = 7.5E+00 AT ROW NUMBER 169
*** USER WARNING MESSAGE 4645 (REIG)
THE SHIFTED STIFFNESS MATRIX IS NOT POSITIVE DEFINITE IN MGIVENS METHOD.
*** USER FATAL MESSAGE 4405 (PRTPRN)
NO EIGENVECTORS COMPUTED FOR COMPONENT MODE SYNTHESIS OR SYSTEM SOLUTION.
我所做的对象是一个轴向沿x轴，底面半径为0.2m，高为20m的长杆，使其完全浸没在水中，自由液面应当大于0.2m，而当自由液面选为大于0.2m时，就会出现上面的错误，当自由液面选为小于0.2m时就能计算出结果。我现在不知道到底是哪里出现问题，现将我做的bdf文件以附件形式给出，请各位高手帮帮忙，先谢谢了。
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