Modal Mass Participation (Effective Weights) From MSC.NASTRAN

sunnygu

Modal Mass Participation (Effective Weights) From MSC.NASTRAN

Two methods are given here for determining the modal mass participation using MSC.NASTRAN.

1. Using MEFFMASS case contol commnad (for MSC/NASTRAN 2001)
2. Using Modal Participation DMAP (for MSC/NASTRAN v. 70.5)
Method 1.
MSC/NASTRAN version 2001 has the capability to extract modal mass participation directly from nomal modes analysis. No DMAP is required and it can be used with the normal modes solution sequence (unlike the UAI command on which it is based). The following is a sample executive and case control deck for a normal modes run with modal mass extraction. The cards that are specific for the modal mass extraction are shown in bold.

Sample Input

ID XYZ,MODALWT
SOL 103
TIME 10
APP DISP
CEND
TITLE=XYZ TEST VERIFIED MODEL (english - renumbered) (08/96)
SUBTITLE=FIXED BASE DYNAMICS W/ASET
SPC=1
echo=none
SPCFORCE=ALL
METHOD=100
MEFFMASS(ALL)=YES
BEGIN BULK

Sample Output


           M O D A L   E F F E C T I V E   M A S S   S U M M A R Y



                           TOTAL EFFECTIVE MASS FRACTION
                 REFERENCE POINT AT ORIGIN OF BASIC COORDINATE SYSTEM


     T1                T2                T3                R1              R2             R3
3.948519E-01      7.700374E-01      9.790530E-01      9.802241E-01    5.374004E-01    4.438883E-01


(This is the total percentage of mass represented in the number of modes extracted in the EIGR card)



                                 EFFECTIVE MASS MATRIX   
***                                                                                  ***
*   1.301470E-02 -1.445757E-05  6.120819E-04 -1.217158E-02  7.967635E-01  2.766647E-01 *
*  -1.445757E-05  2.536148E-02 -3.641499E-04  3.149053E-03 -8.146847E-04 -3.397166E-04 *
*   6.120819E-04 -3.641499E-04  3.227054E-02 -6.531930E-01  2.772698E-02  1.234497E-02 *
*  -1.217158E-02  3.149053E-03 -6.531930E-01  1.323802E+01 -5.505087E-01 -2.455033E-01 *
*   7.967635E-01 -8.146847E-04  2.772698E-02 -5.505087E-01  4.954358E+01  1.663506E+01 *
*   2.766647E-01 -3.397166E-04  1.234497E-02 -2.455033E-01  1.663506E+01  6.176721E+00 *
***                                                                                  ***

                                 A-SET RIGID BODY MASS MATRIX
***                                                                                  ***
*   3.296097E-02  9.154070E-21 -5.196499E-20  9.980221E-19  1.717233E+00  6.654800E-01 *
*   9.154070E-21  3.293540E-02 -6.146909E-22 -5.571844E-05  3.835558E-19  1.002346E-04 *
*  -5.196499E-20 -6.146909E-22  3.296097E-02 -6.654800E-01 -9.742095E-05 -9.906851E-19 *
*   9.980221E-19 -5.571844E-05 -6.654800E-01  1.350510E+01  1.926013E-03 -2.541951E-05 *
*   1.717233E+00  3.835558E-19 -9.742095E-05  1.926013E-03  9.219119E+01  3.458480E+01 *
*   6.654800E-01  1.002346E-04 -9.906851E-19 -2.541951E-05  3.458480E+01  1.391504E+01 *
***                                                                                  ***

zhouchao

我也想问这里边这些东西都代表什么啊？有什么用？看不懂啊！！请教高手！