MAPDL modal beam analysis example

This example demonstrates how to perform a simple modal analysis and animate its results.

Objective

This example models a simple 3D elastic beam made of BEAM188 elements. These beams elements are made of a linear elastic material similar to steel, and have a rectangular section.

Procedure

• Launch MAPDL instance

• Material properties

• Geometry

• Finite element model

• Boundary conditions

• Solving the model

• Post-processing

• Stop MAPDL

Launch MAPDL instance

Launch MAPDL with interactive plotting

from ansys.mapdl.core import launch_mapdl

nmodes = 10
# start MAPDL
mapdl = launch_mapdl()
print(mapdl)

Product:             Ansys Mechanical Enterprise Academic Student
MAPDL Version:       24.2
ansys.mapdl Version: 0.68.5

Define material

Define material

mapdl.prep7()
mapdl.mp("EX", 1, 2.1e11)
mapdl.mp("PRXY", 1, 0.3)
mapdl.mp("DENS", 1, 7800)

MATERIAL          1     DENS =   7800.000

Create geometry

Create keypoints and line

mapdl.k(1)
mapdl.k(2, 10)
mapdl.l(1, 2)
mapdl.lplot()

Define finite element model

Define element type/section type - Rectangular beam section.

mapdl.et(1, "BEAM188")
mapdl.sectype(1, "BEAM", "RECT")
mapdl.secoffset("CENT")
mapdl.secdata(2, 1)

# Mesh the line
mapdl.type(1)
mapdl.esize(1)
mapdl.lesize("ALL")
mapdl.lmesh("ALL")
mapdl.eplot()
mapdl.finish()

***** ROUTINE COMPLETED *****  CP =         0.000

Specify boundary conditions

Fully fixed (clamped) end.

mapdl.solution()  # Entering the solution processor.
mapdl.nsel("S", "LOC", "X", "0")
mapdl.d("ALL", "ALL")
mapdl.allsel()
mapdl.nplot(plot_bc=True, nnum=True)

Solve the model

Setting modal analysis

mapdl.antype("MODAL")
mapdl.modopt("LANB", nmodes, 0, 200)
mapdl.solve()
mapdl.finish()

FINISH SOLUTION PROCESSING


 ***** ROUTINE COMPLETED *****  CP =         0.000

Postprocess

Enter the post processor (post1)

mapdl.post1()
output = mapdl.set("LIST")
print(output)

result = mapdl.result

*****  INDEX OF DATA SETS ON RESULTS FILE  *****

     SET   TIME/FREQ    LOAD STEP   SUBSTEP  CUMULATIVE
       1  8.3233851             1         1         1
       2  16.274527             1         2         2
       3  50.891463             1         3         3
       4  60.248510             1         4         4
       5  89.208488             1         5         5
       6  129.85203             1         6         6
       7  138.63765             1         7         7
       8  182.23482             1         8         8

Animate results

mode2plot = 2
normalizeDisplacement = 1 / result.nodal_displacement(mode2plot - 1)[1].max()

result.plot_nodal_displacement(
    mode2plot,
    show_displacement=True,
    displacement_factor=normalizeDisplacement,
    n_colors=10,
)

result.animate_nodal_displacement(
    mode2plot,
    loop=False,
    add_text=False,
    n_frames=100,
    displacement_factor=normalizeDisplacement,
    show_axes=False,
    background="w",
    movie_filename="animation.gif",
    off_screen=True,
)

• 
• 

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[(16.153550716504107, 11.153550716504107, 11.153550716504107),
 (5.0, 0.0, 0.0),
 (0.0, 0.0, 1.0)]

Stop MAPDL

mapdl.finish()
mapdl.exit()