This example uses
Abaqus Scripting Interface
commands to evaluate the sensitivity of the shell elements in
Abaqus
to skew distortion when they are used as thin plates.
Further details can be found in
Skew sensitivity of shell elements.
The problem investigates the effects on the accuracy of the bending moment
computed at the center of a shell using:
different shell formulations and
at different angles.
Figure 1
illustrates the basic geometry of the simply supported skew plate with a
uniform distributed load.
The plate is loaded by a uniform pressure of 1.0 × 10−6 MPa
applied over the entire surface. The edges of the plate are all simply
supported. The analysis is performed for five different values of the skew
angle, :
90°, 80°, 60°, 40°, and 30°. The analysis is performed for two different
quadrilateral elements: S4 and S8R.
The example is divided into two scripts. The controlling script,
skewExample.py, imports
skewExampleUtils.py. Use the
fetch utility to retrieve the scripts:
You should use
Abaqus/CAE
to create your model and to save the resulting model database. You will then
use scripting to parameterize your model, submit an analysis job, and operate
on the results generated.
Start
Abaqus/CAE,
and create a model database from the Start Session dialog
box. By default, you are operating on a model named
Model-1. The model should include the following:
Part
Create a three-dimensional planar shell part, and name it Plate.
Use an approximate size of 5.0. Sketch a square where all sides are 1.0 m long, with the
lower-left vertex at (0, 0, 0). Delete all perpendicular and vertical constraints, and
apply the following:
fixed constraints to the lower-left and lower-right vertices,
horizontal constraints to the top and bottom edges (if they are not already defined),
parallel constraints to the left and right edges, and
an angle dimension to the lower-left vertex (90°).
Material
Create a material, and name it Steel. The
Young's modulus is 30 MPa, and the Poisson's ratio is 0.3.
Section
Create a homogeneous shell section that refers to the material called
Steel. Name the section
Shell. The plate thickness is 0.01 m. The
length/thickness ratio is, thus, 100/1 so that the plate is thin in the sense
that transverse shear deformation should not be significant. Assign the section
to the plate.
Assembly
Create the assembly using a single, independent part instance of
Plate.
Abaqus/CAE
names the part instance Plate-1. Creating an
independent part instance means that the mesh is based at the assembly level.
Step
Create a static step and name it Step-1.
Enter Apply pressure for the step
Description. Accept the default time period of 1.0 and the
default initial increment of 1.0.
Output database
requests
Edit the default output database request for field output and select only U,
Translations and rotations. Create a second field output request for
SF, Section forces and moments, and specify
Nodes as the element output position. Both field output requests
should be for the whole model after every increment. Delete all requests for history
output.
Boundary
condition
Create a displacement boundary condition, and name it
Pinned. The boundary condition pins the exterior
edges of the plate.
Load
Create a pressure load, and name it Pressure.
Apply the load to the face of the plate. Accept the default side of the plate
and use a magnitude of 1.0. This positive pressure will result in a negative
displacement in the 3-direction.
Set
Partition the plate into quarters by sketching lines between the midpoints
of the four edges. Create a set that contains the vertex at the center of the
plate, and name the set CENTER.
Mesh
Create a 4 × 4 mesh of quadrilateral elements on the plate.
Job
Create a job, and name it skew. The job must
refer to the model Model-1.
If you want, you can complete the above steps for creating the model using a function in
skewExampleUtils.py. In the command line interface area of Abaqus/CAE, type the following commands: