ross.BearingElement

ross.BearingElement#

class ross.BearingElement(n, kxx, cxx, mxx=0, kyy=None, kxy=0, kyx=0, cyy=None, cxy=0, cyx=0, myy=None, mxy=0, myx=0, kzz=0, czz=0, mzz=0, frequency=None, tag=None, n_link=None, scale_factor=1, color='#355d7a', **kwargs)#

A bearing element.

This class will create a bearing element. Parameters can be a constant value or speed dependent.

Parameters:

nint: Node which the bearing will be located in
kxxfloat, array, pint.Quantity: Direct stiffness in the x direction (N/m).
cxxfloat, array, pint.Quantity: Direct damping in the x direction (N*s/m).
mxxfloat, array, pint.Quantity: Direct mass in the x direction (kg). Default is 0.
kyyfloat, array, pint.Quantity, optional: Direct stiffness in the y direction (N/m). Default is kxx.
cyyfloat, array, pint.Quantity, optional: Direct damping in the y direction (N*s/m). Default is cxx.
myyfloat, array, pint.Quantity, optional: Direct mass in the y direction (kg). Default is mxx.
kxyfloat, array, pint.Quantity, optional: Cross coupled stiffness in the x direction (N/m). Default is 0.
cxyfloat, array, pint.Quantity, optional: Cross coupled damping in the x direction (N*s/m). Default is 0.
mxyfloat, array, pint.Quantity, optional: Cross coupled mass in the x direction (kg). Default is 0.
kyxfloat, array, pint.Quantity, optional: Cross coupled stiffness in the y direction (N/m). Default is 0.
cyxfloat, array, pint.Quantity, optional: Cross coupled damping in the y direction (N*s/m). Default is 0.
myxfloat, array, pint.Quantity, optional: Cross coupled mass in the y direction (kg). Default is 0.
kzzfloat, array, pint.Quantity, optional: Direct stiffness in the z direction (N/m). Default is 0.
czzfloat, array, pint.Quantity, optional: Direct damping in the z direction (N*s/m). Default is 0.
mzzfloat, array, pint.Quantity, optional: Direct mass in the z direction (kg). Default is 0.
frequencyarray, pint.Quantity, optional: Array with the frequencies (rad/s).
tagstr, optional: A tag to name the element Default is None.
n_linkint, optional: Node to which the bearing will connect. If None the bearing is connected to ground. Default is None.
scale_factorfloat, optional: The scale factor is used to scale the bearing drawing. Default is 1.
colorstr, optional: A color to be used when the element is represented. Default is ‘#355d7a’ (Cardinal).

Attributes:

_save_attrslist: Extra instance attributes to persist on save/load, beyond __init__ parameters and coefficients. Subclasses can extend this to include derived quantities that are expensive to recompute.
For speed dependent parameters, each argument should be passed
as an array and the correspondent speed values should also be
passed as an array.
Values for each parameter will be_interpolated for the speed.

Examples

>>> # A bearing element located in the first rotor node, with these
>>> # following stiffness and damping coefficients and speed range from
>>> # 0 to 200 rad/s
>>> import ross as rs
>>> kxx = 1e6
>>> kyy = 0.8e6
>>> cxx = 2e2
>>> cyy = 1.5e2
>>> frequency = np.linspace(0, 200, 11)
>>> bearing0 = rs.BearingElement(n=0, kxx=kxx, kyy=kyy, cxx=cxx, cyy=cyy, frequency=frequency)
>>> bearing0.K(frequency[-1])
array([[1000000.,       0.,       0.],
       [      0.,  800000.,       0.],
       [      0.,       0.,       0.]])
>>> bearing0.C(frequency[-1])
array([[200.,   0.,   0.],
       [  0., 150.,   0.],
       [  0.,   0.,   0.]])

Methods

C(frequency)#

Damping matrix for an instance of a bearing element.

This method returns the damping matrix for an instance of a bearing element.

Parameters:

frequencyfloat: The excitation frequency (rad/s).

Returns:

Cnp.ndarray: A 3x3 matrix of floats containing the cxx, cxy, cyx, cyy, and czz values (N*s/m).

Examples

>>> bearing = bearing_example()
>>> bearing.C(0)
array([[200.,   0.,   0.],
       [  0., 150.,   0.],
       [  0.,   0.,  50.]])

G()#

Gyroscopic matrix for an instance of a bearing element.

This method returns the mass matrix for an instance of a bearing element.

Returns:

Gnp.ndarray: A 3x3 matrix of floats.

Examples

>>> bearing = bearing_example()
>>> bearing.G()
array([[0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])

K(frequency)#

Stiffness matrix for an instance of a bearing element.

This method returns the stiffness matrix for an instance of a bearing element.

Parameters:

frequencyfloat: The excitation frequency (rad/s).

Returns:

Knp.ndarray: A 3x3 matrix of floats containing the kxx, kxy, kyx, kyy and kzz values (N/m).

Examples

>>> bearing = bearing_example()
>>> bearing.K(0)
array([[1000000.,       0.,       0.],
       [      0.,  800000.,       0.],
       [      0.,       0.,  100000.]])

M(frequency)#

Mass matrix for an instance of a bearing element.

This method returns the mass matrix for an instance of a bearing element.

Parameters:

frequencyfloat: The excitation frequency (rad/s).

Returns:

Mnp.ndarray: Mass matrix (kg).

Examples

>>> bearing = bearing_example()
>>> bearing.M(0)
array([[0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])

__init__(n, kxx, cxx, mxx=0, kyy=None, kxy=0, kyx=0, cyy=None, cxy=0, cyx=0, myy=None, mxy=0, myx=0, kzz=0, czz=0, mzz=0, frequency=None, tag=None, n_link=None, scale_factor=1, color='#355d7a', **kwargs)#

dof_local_index()#

Get the local index for a element specific degree of freedom.

Returns:

local_index: namedtupple: A named tuple containing the local index.

Examples

>>> # Example using BearingElement
>>> from ross.bearing_seal_element import bearing_example
>>> bearing = bearing_example()
>>> bearing.dof_local_index()
LocalIndex(x_0=0, y_0=1, z_0=2)

dof_mapping()#

Degrees of freedom mapping.

Returns a dictionary with a mapping between degree of freedom and its index.

Returns:

dof_mappingdict: A dictionary containing the degrees of freedom and their indexes.

Examples

The numbering of the degrees of freedom for each node.

Being the following their ordering for a node:

x_0 - horizontal translation y_0 - vertical translation z_0 - axial translation

>>> bearing = bearing_example()
>>> bearing.dof_mapping()
{'x_0': 0, 'y_0': 1, 'z_0': 2}

format_table(frequency=None, coefficients=None, frequency_units='rad/s', stiffness_units='N/m', damping_units='N*s/m', mass_units='kg')#

Return frequency vs coefficients in table format.

Parameters:

frequencyarray, pint.Quantity, optional: Array with frequencies (rad/s). Default is 5 values from min to max frequency.
coefficientslist, str, optional: List or str with the coefficients to include. Defaults is a list of stiffness and damping coefficients.
frequency_unitsstr, optional: Frequency units. Default is rad/s.
stiffness_unitsstr, optional: Stiffness units. Default is N/m.
damping_unitsstr, optional: Damping units. Default is N*s/m.
mass_unitsstr, optional: Mass units. Default is kg.

Returns:

tablePrettyTable object: Table object with bearing coefficients to be printed.

classmethod from_table(n, file, sheet_name=0, tag=None, n_link=None, scale_factor=1, color='#355d7a')#

Instantiate a bearing using inputs from an Excel table.

A header with the names of the columns is required. These names should match the names expected by the routine (usually the names of the parameters, but also similar ones). The program will read every row bellow the header until they end or it reaches a NaN.

Parameters:

nint: The node in which the bearing will be located in the rotor.
filestr: Path to the file containing the bearing parameters.
sheet_nameint or str, optional: Position of the sheet in the file (starting from 0) or its name. If none is passed, it is assumed to be the first sheet in the file.
tagstr, optional: A tag to name the element. Default is None.
n_linkint, optional: Node to which the bearing will connect. If None the bearing is connected to ground. Default is None.
scale_factorfloat, optional: The scale factor is used to scale the bearing drawing. Default is 1.
colorstr, optional: A color to be used when the element is represented. Default is ‘#355d7a’ (Cardinal).

Returns:

bearingrs.BearingElement: A bearing object.

Examples

>>> import os
>>> file_path = os.path.dirname(os.path.realpath(__file__)) + '/tests/data/bearing_seal_si.xls'
>>> BearingElement.from_table(0, file_path, n_link=1)
BearingElement(n=0, n_link=1,
 kxx=[1.379...

get_class_name_prefix(index=None)#

Extract prefix of the class name preceding ‘Element’, insert spaces before uppercase letters, and append an index number at the end.

Parameters:

indexint, optional: The index number to append at the end of the resulting string. Default is None.

Returns:

prefixstr: The processed class name prefix.

Examples

>>> # Example using BearingElement
>>> from ross.bearing_seal_element import bearing_example
>>> bearing = bearing_example()
>>> bearing.get_class_name_prefix()
'Bearing'

classmethod get_subclasses()#

Get all subclasses of the Element class.

Returns:

subclasseslist: A list containing all subclasses of the Element class.

classmethod load(file)#

Load an element from a .toml or .json file.

Parameters:

filestr, pathlib.Path: The name of the file the element will be loaded from.

Returns:

The element object.

plot(coefficients=None, frequency_units='rad/s', stiffness_units='N/m', damping_units='N*s/m', mass_units='kg', fig=None, **kwargs)#

Plot coefficient vs frequency.

Parameters:

coefficientslist, str: List or str with the coefficients to plot.
frequency_unitsstr, optional: Frequency units. Default is rad/s.
stiffness_unitsstr, optional: Stiffness units. Default is N/m.
damping_unitsstr, optional: Damping units. Default is N*s/m.
mass_unitsstr, optional: Mass units. Default is kg.
**kwargsoptional: Additional key word arguments can be passed to change the plot layout only (e.g. width=1000, height=800, …). *See Plotly Python Figure Reference for more information.

Returns:

figPlotly graph_objects.Figure(): The figure object with the plot.

classmethod read_toml_data(data)#

Read and parse data stored in a .toml or .json file.

Overrides the base Element method to pass extra saved keys (e.g. pre-computed coefficients) as kwargs to the constructor. This allows subclasses to skip expensive computation when coefficients are already available from a saved file.

Parameters:

datadict: Dictionary obtained from toml.load() or json.load().

Returns:

The element object.

save(file)#

Save the element in a .toml or .json file.

This function will save the element to a .toml or .json file. The file will have all the argument’s names and values that are needed to reinstantiate the element.

Parameters:

filestr, pathlib.Path: The name of the file the element will be saved in. The format is determined by the file extension (.toml or .json).

Examples

>>> # Example using DiskElement
>>> from tempfile import tempdir
>>> from pathlib import Path
>>> from ross.disk_element import disk_example
>>> # create path for a temporary file
>>> file = Path(tempdir) / 'disk.toml'
>>> disk = disk_example()
>>> disk.save(file)

summary()#

Present a summary for the element.

A pandas series with the element properties as variables.

Returns:

A pandas series.

Examples

>>> # Example using DiskElement
>>> from ross.disk_element import disk_example
>>> disk = disk_example()
>>> disk.summary()
n                             0
n_l                           0
n_r                           0...

classmethod table_to_toml(n, file)#

Convert bearing parameters to toml.

Convert a table with parameters of a bearing element to a dictionary ready to save to a toml file that can be later loaded by ross.

Parameters:

nint: The node in which the bearing will be located in the rotor.
filestr: Path to the file containing the bearing parameters.

Returns:

datadict: A dict that is ready to save to toml and readable by ross.

Examples

>>> import os
>>> file_path = os.path.dirname(os.path.realpath(__file__)) + '/tests/data/bearing_seal_si.xls'
>>> BearingElement.table_to_toml(0, file_path)
{'n': 0, 'kxx': array([...

ross.BearingElement

Contents

ross.BearingElement#