注釈

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Generating and Extracting Rotational Displacement#

In this example we show how to work with shells and rotation displacements.

Not all element types have rotational degrees of freedom, but generally, "shell" ones do. In this example we create a square shell with thickness of 0.1 and bend it, creating rotational displacement.

We subsequently plot the cumulative principal stresses and use ansys.mapdl.core.inline_functions.Query to extract the exact values of rotational displacement at the four corners of our square.

# start MAPDL and enter the pre-processing routine
from ansys.mapdl.core import launch_mapdl

mapdl = launch_mapdl()
mapdl.prep7()

Mesh Setup#

In this example we create a simple 2D square, 1 x 1 in dimension, and give it the 'SHELL181' element type because this type has rotational degrees of freedom. Following this we:

  • Give the material an elastic modulus of 2e5 (EX)

  • Give the material a major poissons ratio of 0.3 (PRXY)

  • Set the section type to 'SHELL'

  • Set the thickness to 0.1

  • Set the element size to 0.2

  • Mesh the square

  • Plot the mesh

mapdl.et(1, "SHELL181")
mapdl.mp("EX", 1, 2e5)
mapdl.mp("PRXY", 1, 0.3)
mapdl.rectng(0, 1, 0, 1)
mapdl.sectype(1, "SHELL")
mapdl.secdata(0.1)
mapdl.esize(0.2)
mapdl.amesh("all")
mapdl.eplot()

Applying Boundary Conditions#

  • Enter solution mode

  • Set analysis type to 'STATIC'

  • Remove all degrees of freedom for nodes at x = 0

  • Apply a displacement of uz = -0.1 at x = 1

  • Select all nodes

  • Solve the model

mapdl.run("/SOLU")
mapdl.antype("STATIC")
mapdl.nsel("s", "loc", "x", 0)
mapdl.d("all", "all")
mapdl.nsel("s", "loc", "x", 1)
mapdl.d("all", "uz", -0.1)
mapdl.allsel("all")
mapdl.solve()

Plotting Stresses#

  • Extract the results

  • Plot the cumulative (0) equivalent stress (SEQV) - Set the colormap to 'plasma' because it is perceptually uniform - Show displacement so that we can see any deformation

result = mapdl.result
result.plot_principal_nodal_stress(
    0, "SEQV", show_edges=True, cmap="plasma", show_displacement=True
)

Extracting Rotational Displacements#

  • Get a ansys.mapdl.core.inline_functions.Query instance from the queries property

  • Locate the nodes at the four corners of the square

  • Extract all 3 rotational displacement components for each one

  • Print them all

q = mapdl.queries

node1 = q.node(0, 0, 0)
node2 = q.node(0, 1, 0)
node3 = q.node(1, 0, 0)
node4 = q.node(1, 1, 0)

nodes = [node1, node2, node3, node4]

rotations = [(q.rotx(n), q.roty(n), q.rotz(n)) for n in nodes]

message = f"""
(0,1) B _________ C (1,1)
       |         |
       |         |
       |         |
       |_________|
(0,0) A           D (1,0)

N | (x_rot_disp, y_rot_disp, z_rot_disp)
--|------------------------------------
A | {rotations[0][0]:11.6f},{rotations[0][1]:11.6f},{rotations[0][2]:11.6f}
B | {rotations[1][0]:11.6f},{rotations[1][1]:11.6f},{rotations[1][2]:11.6f}
C | {rotations[2][0]:11.6f},{rotations[2][1]:11.6f},{rotations[2][2]:11.6f}
D | {rotations[3][0]:11.6f},{rotations[3][1]:11.6f},{rotations[3][2]:11.6f}

"""

print(message)

Stop mapdl#

mapdl.exit()