FRF for a rectangular plate

This example shows how to set up the keywords for computation of a FRF (frequency response function). The executable file for LS-DYNA is ls-dyna_smp_d_R13.1_138-g8429c8a10f_winx64_ifort190.exe.

Perform required imports

Peform the required imports.

import os
import sys


from ansys.dyna.core.pre import launch_dynapre
from ansys.dyna.core.pre.dynamaterial import MatElastic
from ansys.dyna.core.pre.dynanvh import (
    DynaNVH,
    FrequencyDomain,
    ExcitationDOF,
    Curve,
    NodeSet,
    ShellPart,
    ShellFormulation,
    ResponseDOF,
    ResponseType,
)
from ansys.dyna.core.pre import examples
from ansys.dyna.core.pre.misc import check_valid_ip

Start the pre service

Before starting the pre service, you must ensure that the Docker container for this service has been started. For more information, see “Start the Docker container for the pre service” in https://dyna.docs.pyansys.com/version/stable/index.html.

The pre service can also be started locally, please download the latest version of ansys-pydyna-pre-server.zip package from ansys/pydyna and start it refering to the README.rst file in this server package.

Once the pre service is running, you can connect a client to it using the hostname and port. This example uses the default localhost and port ("localhost" and "50051" respectively).

hostname = "localhost"
if len(sys.argv) > 1 and check_valid_ip(sys.argv[1]):
    hostname = sys.argv[1]
solution = launch_dynapre(ip = hostname)

Import mesh data (nodes and elements)

Import initial mesh data, which includes the predefined NODE, ELEMENT_ and PART cards.

fns = []
path = examples.nvh_frf_plate_damping + os.sep
fns.append(path + "frf_plate_damping.k")
solution.open_files(fns)

ret: true

Define global control cards

Define the global control cards.

nvhobj = DynaNVH()
solution.add(nvhobj)

Set initial timestep size

Set the initial timestep size in CONTROL_IMPLICIT_GENERAL.

nvhobj.implicitanalysis.set_initial_timestep_size(1.0)

Set number of eigen modes

Set the number of eigen modes to 100.

nvhobj.implicitanalysis.set_eigenvalue(number_eigenvalues=100)

Define linear solver

Define the linear solver by setting NSOLVR to 1 in CONTROL_IMPLICIT_SOLUTION.

nvhobj.implicitanalysis.set_solution(solution_method=1)

Define frequency domain cards

FREQUENCY_DOMAIN_FRF is used to compute the frequency response function due to nodal excitations. In this case, a base velocity is defined as an input at node 131. The base acceleration response is measured at nodes 131 and 651. The maximum natural frequency employed in FRF is limited to 2000 Hz.

fd = FrequencyDomain()
crv = Curve(
    x=[1, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 200],
    y=[0, 0, 0.0045, 0.00713, 0.00386, 0.00328, 0.0034, 0.00624, 7.2e-4, 8.3e-4, 0, 0],
)
fd.set_frequency_response_function(
    excitation_input_set=NodeSet([131]),
    excitation_input_dof=ExcitationDOF.Z,
    max_natural_frequency=2000,
    modal_damping_coefficient_curve_type=1,
    modal_damping_coefficient_curve=crv,
    response_output_set=NodeSet([131, 651]),
    response_output_dof=ResponseDOF.Z,
    response_output_type=ResponseType.BASE_ACCELERATION,
    frf_output_min_frequency=1,
    frf_output_max_frequency=400,
    frf_output_num_frequency=400,
)
nvhobj.add(fd)

Define material and section properties

Define the MAT_ELASTIC material. Set shell formulation to SR_HUGHES_LIU.

matelastic = MatElastic(mass_density=7870, young_modulus=2.07e11, poisson_ratio=0.292)

boxshell = ShellPart(1)
boxshell.set_material(matelastic)
boxshell.set_element_formulation(ShellFormulation.SR_HUGHES_LIU)
boxshell.set_thickness(0.002)
boxshell.set_shear_factor(0.833)

Set printout property and save input deck

Use the set_printout() method to set the printout property to 3. Save the input deck.

boxshell.set_printout(3)
nvhobj.parts.add(boxshell)

solution.save_file()

'/server/output'