Source code for felupe.mechanics._solidbody_gravity
# -*- coding: utf-8 -*-
"""
This file is part of FElupe.
FElupe is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
FElupe is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FElupe. If not, see <http://www.gnu.org/licenses/>.
"""
import numpy as np
from scipy.sparse import csr_matrix
from ..assembly import IntegralForm
from ._helpers import Assemble, Results
[docs]
class SolidBodyGravity:
r"""A gravity (body) force on a solid body.
Parameters
----------
field : FieldContainer
A field container with fields created on a boundary region.
gravity : ndarray or None, optional
The prescribed values of gravity :math:`\boldsymbol{g}` (default is None). If
None, the gravity vector is set to zero (the dimension of the gravity vector is
derived from the first field of the field container).
density : float, optional
The density :math:`\rho` of the solid body (default is 1.0).
Notes
-----
.. math::
\delta W_{ext} = \int_V
\delta \boldsymbol{u} \cdot \rho \boldsymbol{g} \ dV
Examples
--------
.. pyvista-plot::
>>> import felupe as fem
>>>
>>> mesh = fem.Cube(n=6)
>>> region = fem.RegionHexahedron(mesh)
>>> field = fem.FieldContainer([fem.Field(region, dim=3)])
>>> boundaries = fem.dof.symmetry(field[0])
>>>
>>> umat = fem.NeoHooke(mu=1, bulk=2)
>>> solid = fem.SolidBody(umat, field)
>>> gravity = fem.SolidBodyGravity(field, density=1.0)
>>>
>>> table = fem.math.linsteps([0, 1], num=5, axis=0, axes=3)
>>> step = fem.Step(
... items=[solid, gravity],
... ramp={gravity: 2 * table},
... boundaries=boundaries,
... )
>>>
>>> job = fem.Job(steps=[step]).evaluate()
>>> solid.plot("Principal Values of Cauchy Stress").show()
"""
def __init__(self, field, gravity=None, density=1.0):
self.field = field
self.results = Results(stress=False, elasticity=False)
self.assemble = Assemble(vector=self._vector, matrix=self._matrix)
self._form = IntegralForm
self.results.gravity = np.zeros(self.field[0].dim)
if gravity is not None:
self.results.gravity = np.array(gravity)
self.results.density = density
[docs]
def update(self, gravity):
self.__init__(self.field, gravity, self.results.density)
def _vector(self, field=None, parallel=False):
if field is not None:
self.field = field
# copy and take only the first (displacement) field of the container
f = self.field.copy()
f.fields = f.fields[0:1]
self.results.force = self._form(
fun=[self.results.density * self.results.gravity.reshape(-1, 1, 1)],
v=f,
dV=self.field.region.dV,
grad_v=[False],
).assemble(parallel=parallel)
if len(self.field) > 1:
self.results.force.resize(np.sum(self.field.fieldsizes), 1)
return -self.results.force
def _matrix(self, field=None, parallel=False):
if field is not None:
self.field = field
n = np.sum(self.field.fieldsizes)
self.results.stiffness = csr_matrix(([0], ([0], [0])), shape=(n, n))
return self.results.stiffness