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mass1,mass2

Purpose

Concentrated mass elements.

Description

mass1 places a diagonal concentrated mass and inertia at one node.

In a model description matrix, element property rows for mass1 elements follow the format 

 [NodeID mxx myy mzz ixx iyy izz EltID]

where the concentrated nodal mass associated to the DOFs .01 to .06 of the indicated node is given by

   diag([mxx myy mzz ixx iyy izz])

Note feutil GetDof eliminates DOFs where the inertia is zero. You should thus use a small but non zero mass to force the use of all six DOFs.

For mass2 elements, the element property rows follow the format 

 [n1 M I11 I21 I22 I31 I32 I33 EltID CID X1 X2 X3 MatId ProId]

which, for no offset, corresponds to matrices given by

 [
M  symmetric  
 M
  M
   I11 
   −I21I22 
   −I31−I32I33 
]=[
∫ρ dV
  symmetric  
 M
  M
   
∫ρ (x2+y2)dV 
   −I21I22 
   −I31−I32I33 
]

Note that local coordinates CID are not currently supported by mass2 elements.

See also

femesh, feplot


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