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如何提取模态质量
模态分析过程中打开振型型则化开关(MODOPT命令的Nrmkey设置为ON)，A YS程序将自动将每阶模态的最大位移单位化，就可以提取模态质量。计算方法如下：
1、利用 UM对ETABLE 动能数据求和获得结构总动能( ）；
2、将结构总动能除以 得到 ，其中 是系统的角频率。
下面是《A YS Verification Manual》中VM89.DAT稍加修改后提取模态质量的例子：
/PREP7
/TITLE, VM89, NATURAL FREQUENCIES OF A TWO-MA - RING SYSTEM
C*** VIBRATION THEORY AND A LICATIO , THOMSON, 2ND PRINTING, PAGE 163,EX 6.2-2
ET,1,COMBIN14,,,2
ET,2,MA 21,,,4
R,1,200 ! RING CO TANT = 200
R,2,800 ! RING CO TANT = 800
R,3,.5 ! MA = .5
R,4,1 ! MA = 1
N,1
N,4,1
FILL
E,1,2 ! RING ELEMENT (TYPE,1) AND K = 200 (REAL,1)
TYPE,2
REAL,3
E,2 ! MA ELEMENT (TYPE,2) AND MA = .5 (REAL,3)
TYPE,1
REAL,2
E,2,3 ! RING ELEMENT (TYPE,1) AND K = 800 (REAL,2)
TYPE,2
REAL,4
E,3 ! MA ELEMENT (TYPE,2) AND MA = 1 (REAL,4)
TYPE,1
REAL,1
E,3,4 ! RING ELEMENT (TYPE,1) AND K = 200 (REAL,1)
M,2,UX,3
OUTPR,BASIC,1
D,1,UY,,,4
D,1,UX,,,4,3
FINISH
/SOLU
ANTYPE,MODAL
MODOPT,su a,2,,,2,ON
MXPAND,2,,,YES
SOLVE
FINISH
/post1
set,1,1
etabl,kene,kene
um
*get,keneval1, um,,item,kene
*get,freqval1,mode,1,freq
eigen1=(2*3.14159*freqval1)**2
pma 1=2*keneval1/eigen1
set,1,2
etabl,kene,kene
um
*get,keneval2, um,,item,kene
*get,freqval2,mode,2,freq
eigen2=(2*3.14159*freqval2)**2
pma 2=2*keneval2/eigen2
finish