Frequency Options
The Frequency dialog box lets
you select the desired options for a frequency study.
Loads affect the modal characteristics of
a body. For example, compressive loads decrease resonant frequencies and
tensile loads increase them. This fact is easily demonstrated by changing
the tension on a violin string. The higher the tension, the higher the
frequency (tone). Loads are not used for frequency studies used for linear
dynamic studies.
If the working scenarios of the model include
dynamic loads, it is important to calculate at least one frequency that
is higher than the frequency of the load. In most situations, resonance
is not desirable because it causes failure. However, some devices exploit
resonance to trigger an event while providing measures to control the
excessive associated deformation.
Calculate
frequencies closest to (frequency shift). Select this option to
specify a frequency value of interest. The software calculates the frequencies
closest to the specified value. This option is referred to as frequency
shift in the literature. You can use this option to avoid calculating
rigid body modes.
Upper Bound Frequency.
Lets you set the upper bound frequency of the desired frequency range.
Use the default value of zero unless you are not interested in natural
frequencies higher than a certain value. Entering zero results in calculating
the specified number of frequencies.
For the FFEPlus solver, you
can specify the Number of Frequencies
or the Upper Bound Frequency.
For the Direct Sparse solver, you can only specify the Number
of Frequencies and specify a frequency shift.
Use soft spring
to stabilize model. Select this option to
add soft springs to stabilize inadequately supported models.
Improve accuracy
for no penetration contacting surfaces (slower).
This method produces continuous and more accurate stresses in regions
with definitions of no penetration contact. The method is used when defining
contact between faces to faces and faces to edges. When this option is
selected, the software may take more time to solve the problem. This method
is referred to as mortar contact in the literature.
Simplified bonding
contact. When this option is checked, the program overrides the
default surface-based bonding contact and resumes to node-based bonding
contact. Check this option only in cases you run into performance issues
when solving models with extensive contact surfaces. The default option
of surface-based contact formulation results in longer solution time than
the node-based contact formulation.
Bonding is most accurate when
the mesh is compatible.
Solver.
Lets you specify the solver to be used in calculating resonant frequencies
and the associated mode shapes. To include the effect of loading on the
resonant frequencies, select Automatic
or Direct sparse.
Automatic.
The software selects the solver based on the study type, analysis options,
contact conditions, etc.
Direct sparse.
Check this option to use the Mode Extraction Routine powered by the Direct
Solver when running the study.
FFEPlus.
Check this option to use the FFEPlus solver when running the study.
Results folder. Lets you specify the directory to store
the simulation results folder.
Related Topics
Remark
What
is Frequency Analysis...