stress_strain_component#
- pytwin.stress_strain_component(str_vectors, item, comp, effective_pr=None)#
Reduce an array of stress or strain tensors to an array of scalar values.
The function applies transformations to return the following outputs at each input location from an input snapshot stress or strain vector:
Individual stress or strain normal or shear components.
Individual stress or strain principal components.
Stress or strain intensity.
Equivalent (von Mises) stress or strain.
Maximum shear stress or strain.
Absolute maximum principal stress.
Signed equivalent (von Mises) stress.
- Parameters:
- str_vectors
np.ndarray
(n, 6)
array of stress or strain vectors of symmetric Cauchy tensor components, X,Y,Z,XY,YZ,XZ.This ordering is consistent with the conventions used in Ansys TBROM snapshots and Ansys Mechanical APDL (2.1.1. Stress-Strain Relationships).
Shear strains are interpreted as being the engineering shear strains, which are twice the tensor shear strains.
Planar stress or strain values can be entered by setting the relevant out-of-plane values to zero.
- item
str
Label identifying the result type of
str_vectors
.S
for stress andE
for strain.- comp
str
|int
Component of the item. See the table below in the notes section.
- effective_pr
float
|None
,default
=None
Effective Poisson’s ratio for calculating equivalent strain. Assumed to be constant for all entries in
str_vectors
. Refer to 2.4. Combined Stresses and Strains for potential values when handling strains other than elastic strain.
- str_vectors
- Returns:
- Raises:
ValueError
if shape of
str_vectors
is not(n, 6)
.ValueError
if invalid combinations for
item
andcomp
are entered.ValueError
if
item = E
andcomp = EQV
andeffective_pr
is not given.
Notes
This table lists the results values available to this method.
item
comp
Description
S
X, Y, Z, XY, YZ, XZ
Component stress.
1, 2, 3
Principal stress.
dir1, dir2, dir3
Principal stress direction cosine.
INT
Stress intensity.
EQV
Equivalent (von Mises) stress.
maxShear
Maximum shear stress
absMaxPrin
Absolute maximum principal stress.
sgnEQV
Signed equivalent (von Mises) stress.
E
X, Y, Z, XY, YZ, XZ
Component strain.
1, 2, 3
Principal strain.
dir1, dir2, dir3
Principal strain direction cosine.
INT
Strain intensity.
EQV
Equivalent (von Mises) strain.
maxShear
Maximum shear strain
Outputs are calculated as described in 2.4. Combined Stresses and Strains and 19.5.2.3. Maximum Shear in the Ansys Mechanical APDL and Ansys Mechanical help.
Examples
>>> import numpy as np >>> from pytwin import stress_strain_component >>> stress_vectors = np.array([[-10,50,0,40,0,0], [15,40,0,30,0,0]]) >>> S_absMaxPrin = stress_strain_component(stress_vectors, 'S', 'absMaxPrin') >>> S_absMaxPrin array([70., 60.])
Calculate equivalent strain for a material with Poisson’s ratio of 0.3 (for example steel). Input strains lie in the XZ plane.
>>> strain_vectors = np.array([[-2.1e-4, 0.0, 5.0e-5, 0.0, 0.0, 1.5e-6]]) >>> E_vonMises = stress_strain_component(strain_vectors, 'E', 'EQV', effective_pr=0.3) >>> E_vonMises array([0.00018382])