Membrane property definition

@MEMBRANE_PROPERTY_DEFINITION {
@MEMBRANE_PROPERTY_NAME {MbnPropName} {
@THICKNESS_PROPERTY_NAME {ThickPropName}
@YOUNG'S_MODULUS {E}
@POISSON'S_RATIO {ν}
@STIFFNESS_MATRIX_A {a1, ...a9}
@MATERIAL_DENSITY {ρ}
@DAMPING_COEFFICIENT {μs}
@COMMENTS {CommentText}
}
}

NOTES

  1. The thickness distribution of the surface of the membrane is defined by the thickness property, ThickPropName.
  2. The physical mass and stiffness properties of a membrane are defined in this section. The mass properties are computed from the material density, ρ.
  3. In general, the stiffness characteristic of a membrane can be represented in the following matrix form N = A ε, where NT = {Nc3, N22, N12} is the vector of in-plane forces per unit length of the membrane and εT = {εc3, ε22, ε12} the corresponding in-plane strains. All loading and strain quantities are measured in a material frame of reference. The thickness of the membrane is allowed to vary over the surface that defined the membrane. Hence, the physical properties will be defined in a non-dimensional manner with respect to thickness.
  4. There are two ways of defining the stiffness properties of the membrane according to the keyword appearing next.
    1. @YOUNG'S_MODULUS: the membrane is assumed to be made of an isotropic, linearly elastic material. The stiffness matrix will be computed from the Young's modulus, E and Poisson's ratio, ν.
    2. @STIFFNESS_MATRIX_A: the membrane is assumed to be made of an anisotropic, linearly elastic material. The stiffness matrix will be computed from constants .
  5. Damping in the membrane can be modeled by viscous forces Nd* proportional to the strain rates, Nd* = μs A dε*/dt, where μs is the damping coefficient.
  6. It is possible to attach comments to the definition of the object; these comments have no effect on its definition.