注釈

Go to the end to download the full example code.

Torsional load on a bar using SURF154 elements#

This Ansys PyMAPDL script builds a bar and applies torque to it using SURF154 elements. This is a static analysis example.

Script initialization#

import os

import numpy as np

from ansys.mapdl.core import launch_mapdl

# start Ansys in the current working directory with default jobname "file"
mapdl = launch_mapdl(run_location=os.getcwd(), version=23.1)

Define cylinder and mesh parameters

torque = 100
radius = 2
h_tip = 2
height = 20
elemsize = 0.5
pi = np.arccos(-1)
force = 100 / radius
pressure = force / (h_tip * 2 * np.pi * radius)

Model creation#

# Define higher-order SOLID186
# Define surface effect elements SURF154 to apply torque
# as a tangential pressure
mapdl.prep7()
mapdl.et(1, 186)
mapdl.et(2, 154)
mapdl.r(1)
mapdl.r(2)

Aluminum properties (or something)

mapdl.mp("ex", 1, 10e6)
mapdl.mp("nuxy", 1, 0.3)
mapdl.mp("dens", 1, 0.1 / 386.1)
mapdl.mp("dens", 2, 0)

# Simple cylinder
for i in range(4):
    mapdl.cylind(radius, "", "", height, 90 * (i - 1), 90 * i)

mapdl.nummrg("kp")

# interactive volume plot (optional)
mapdl.vplot()

Mesh cylinder

mapdl.lsel("s", "loc", "x", 0)
mapdl.lsel("r", "loc", "y", 0)
mapdl.lsel("r", "loc", "z", 0, height - h_tip)
mapdl.lesize("all", elemsize * 2)
mapdl.mshape(0)
mapdl.mshkey(1)
mapdl.esize(elemsize)
mapdl.allsel("all")
mapdl.vsweep("ALL")
mapdl.csys(1)
mapdl.asel("s", "loc", "z", "", height - h_tip + 0.0001)
mapdl.asel("r", "loc", "x", radius)
mapdl.local(11, 1)
mapdl.csys(0)
mapdl.aatt(2, 2, 2, 11)
mapdl.amesh("all")
mapdl.finish()

# plot elements
mapdl.eplot()

Solution#

mapdl.slashsolu()  # Using Slash instead of / due to duplicate SOLU command
mapdl.antype("static", "new")
mapdl.eqslv("pcg", 1e-8)

# Apply tangential pressure
mapdl.esel("s", "type", "", 2)
mapdl.sfe("all", 2, "pres", "", pressure)

# Constrain bottom of cylinder/rod
mapdl.asel("s", "loc", "z", 0)
mapdl.nsla("s", 1)

mapdl.d("all", "all")
mapdl.allsel()
mapdl.psf("pres", "", 2)
mapdl.pbc("u", 1)
mapdl.solve()

Post-processing#

# Enter post-processor
mapdl.post1()
# Select the step you want to analyse
mapdl.set(1, 1)

Access element results as arrays

nodal_stress = mapdl.post_processing.nodal_stress_intensity()
elem_stress = mapdl.post_processing.element_stress("int")

print("Nodal stress : ", nodal_stress)
print("Element stress : ", elem_stress)

Plot interactively#

mapdl.post_processing.plot_nodal_displacement(cmap="bwr")
mapdl.post_processing.plot_nodal_component_stress("x", cmap="bwr")
mapdl.post_processing.plot_nodal_eqv_stress(cmap="bwr")

Plot non-interactively#

# Setting up the correct camera angle
cpos = [
    (20.992831318277517, 9.78629316586435, 31.905115108541928),
    (0.35955395443745797, -1.4198191001571547, 10.346158032932495),
    (-0.10547549888485548, 0.9200673323892437, -0.377294345312956),
]

mapdl.post_processing.plot_nodal_displacement(
    cmap="bwr", cpos=cpos, savefig="cylinder_disp.png"
)
mapdl.post_processing.plot_nodal_component_stress(
    "x", cmap="bwr", cpos=cpos, savefig="cylinder_comp_stx.png"
)
mapdl.post_processing.plot_nodal_eqv_stress(
    cmap="bwr", cpos=cpos, savefig="cylinder_eqv_st.png"
)

Stop MAPDL

mapdl.finish()
mapdl.exit()