fedoo.weakform.StressEquilibrium

class StressEquilibrium(constitutivelaw, incompressibility=None, convert_tangent=True, name='', nlgeom=None, space=None)

Mechanical equilibrium equation for solids.

The main point to consider are:

• This weak form can be used for solid in 3D or using a 2D plane assumption (plane strain or plane stress).

• Include initial stress for non linear problems or if defined in the associated assembly.

• This weak form accepts geometrical non linearities if simcoon is installed. (nlgeom should be in {True, ‘UL’, ‘TL’}. In this case the initial displacement is also considered and several different corotational formulation may be used by setting the corate attribute.

• For nearly incompressible material, a method to avoid the volumetric locking should be selected with the incompressibility attribute.

• The consistent geometric stiffness is enabled automatically for finite-strain tangent conversion. Set geometric_stiffness explicitly to override that default.

Parameters:

• constitutivelaw (ConstitutiveLaw name (str) or ConstitutiveLaw object) – Material Constitutive Law (fedoo.constitutivelaw)

• incompressibility (str, optional) – Method used to avoid the volumetric locking of nearly incompressible materials. See the incompressibility attribute. By default (None), the standard displacement formulation is used.

• convert_tangent (bool, default=True) – Convert the constitutive corotational Kirchhoff tangent to the formulation tangent (dS/dE for TL, spatial Lie for UL). Set to False only when the constitutive law already returns that final formulation-dependent tangent.

• name (str) – name of the WeakForm

• nlgeom (bool, 'UL' or 'TL', optional) – If True, the geometrical non linearities are activate based on the updated lagrangian method. This parameters is used only in the context of NonLinearProblems such as fedoo.problem.NonLinearStatic or fedoo.problem.NonLinearNewmark. If nlgeom == ‘UL’ the updated lagrangian method is used (same as True). If nlgeom == ‘TL’ the total lagrangian method is used. If not defined, the problem.nlgeom parameter is used instead.

• space (ModelingSpace) – Modeling space associated to the weakform. If None is specified, the active ModelingSpace is considered.

__init__(constitutivelaw, incompressibility=None, convert_tangent=True, name='', nlgeom=None, space=None)

Methods

StressEquilibrium.copy()	Return a shallow copy sharing the weak form's model objects.
StressEquilibrium.get_all()	Return the list of all weak forms.
StressEquilibrium.get_dissipation()	Return the optional dissipative provider for a time integrator.
StressEquilibrium.get_storage()	Return the optional storage weakform for a time integrator.
StressEquilibrium.get_weak_equation(assembly, pb)	Get the weak equation related to the current problem state.
StressEquilibrium.initialize(assembly, pb)	Initialize the weakform at the begining of a problem.
StressEquilibrium.iter_leaf()	Iterate over the leaf weakforms contained in this object.
StressEquilibrium.reset()
StressEquilibrium.set_damping([damping])	Mechanical alias for set_dissipation.
StressEquilibrium.set_dissipation([...])	Attach a dissipative contribution.
StressEquilibrium.set_inertia(density_or_storage)	Mechanical alias for set_storage.
StressEquilibrium.set_start(assembly, pb)	Start a new time increment.
StressEquilibrium.set_storage(storage[, ...])	Attach a time-storage weakform to this static weakform.
StressEquilibrium.sum(wf1, wf2)
StressEquilibrium.to_start(assembly, pb)	Reset the current time increment.
StressEquilibrium.update(assembly, pb)	Update the weakform to the current state.
StressEquilibrium.update_2(assembly, pb)	Update the weakform to the current state.

StressEquilibrium.convert_tangent	Whether Fedoo converts the finite-strain constitutive tangent.
StressEquilibrium.corate	Corotational strain mesure for strain.
StressEquilibrium.geometric_stiffness	Whether to add geometric effects to the stiffness matrix.
StressEquilibrium.incompressibility	Method used to avoid volumetric locking.
StressEquilibrium.name	Return the name of the WeakForm.
StressEquilibrium.nvar	Number of variables in the modeling space associated to the WeakForm.
StressEquilibrium.space	Return the ModelingSpace associated to the WeakForm if defined.
StressEquilibrium.nlgeom	Method used to treat the geometric non linearities. * Set to False if geometric non linarities are ignored. * Set to True or 'UL' to use the updated lagrangian method (update the mesh) * Set to 'TL' to use the total lagrangian method (base on the initial mesh with initial displacement effet).