【讨论】LS_DYNA的求解时间步长是否与最小单元相关.

ADAMSLAU

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httcm

ADAMSLAU wrote:
LS_DYNA的求解时间步长是否与最小单元相关.

1.Timestep must Subdivide Smallest Natural Period of the Mesh
    The timestep used by MSC.DYTRAN must be smaller than the smallest natural period of the mesh.  Imagine doing an eigenvalue analysis with the same mesh and extracting every possible mode.  The timestep must be smaller than the period associated with the highest natural frequency given.  The mode shape associated with this eigenvalue is typically one grid point oscillating on the stiffness of the elements to which it is attached.
2.Courant Criterion
    Since it is impossible to do a complete eigenvalue analysis every cycle to calculate the timestep, an approximate method, known as the Courant Criterion, is used.  This is based on the minimum time for a stress wave to cross on elements.
  
    It depends on the smallest element dimension, L
  
    where c is the speed of sound through the element material and S is the timestep Scale Factor (<1).
For 1-D elements:
  　c=√(Young's Modulus/Density)

httcm

ADAMSLAU wrote:
LS_DYNA的求解时间步长是否与最小单元相关.

1.Timestep must Subdivide Smallest Natural Period of the Mesh
    The timestep used by MSC.DYTRAN must be smaller than the smallest natural period of the mesh.  Imagine doing an eigenvalue analysis with the same mesh and extracting every possible mode.  The timestep must be smaller than the period associated with the highest natural frequency given.  The mode shape associated with this eigenvalue is typically one grid point oscillating on the stiffness of the elements to which it is attached.
2.Courant Criterion
    Since it is impossible to do a complete eigenvalue analysis every cycle to calculate the timestep, an approximate method, known as the Courant Criterion, is used.  This is based on the minimum time for a stress wave to cross on elements.
  
    It depends on the smallest element dimension, L
  
    where c is the speed of sound through the element material and S is the timestep Scale Factor (<1).
For 1-D elements:
  　c=√(Young's Modulus/Density)