| Number
of Frequencies |
Lets you set the required number
of natural (resonant) frequencies to be calculated. The default is
to calculate the lowest five frequencies. Rigid body modes are
calculated by the FFEPlus solver. A body without any restraints has
six rigid body modes. Rigid body modes have zero frequencies
(infinite period). 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.
|
| Upper
Bound Frequency |
Lets you set the upper bound
frequency of the required 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
Intel Direct sparse solver, you can only specify the Number of Frequencies and
specify a frequency shift.
|
| Decouple the mixed free body
modes |
When you select this option, the solver separates the mixed free body
modes into pure translational and pure rotational mode
shapes.
A mixed mode shape might exhibit both translational and rotational
degrees of freedom in more than one direction of motion. By
selecting to decouple the mixed free body modes, the solver
separates the translational and the rotational degrees of
freedom in distinct modes in a specific direction of motion (X,
Y, Z, or an oblique direction).
Decoupling the mixed free body modes helps
you visualize the locations of a model that might be
insufficiently restrained during a simulation.
|
| Calculate frequencies closest to (frequency
shift) |
Available for the Intel Direct
Sparse solver. 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. In cases where the frequency
analysis cannot run because of singularity of the stiffness
matrix, use the frequency shift option to overcome the
singularity issue. Increase the shift value gradually from zero
until the Intel Direct Sparse solver successfully calculates the
requested frequencies. If you set a higher
value for the frequency shift, the Intel Direct Sparse
solver selectively calculates the requested number of
frequencies, which are clustered around the shift value.
Thus, you can avoid the computation of lower range
frequencies (including the rigid body modes), which might be
of no interest to your analysis, and save computational
time.
|
| Use
inplane effect |
This option is internally
activated to account for the effects of any applied loads on the
model's stiffness.
See
also Use Inplane Effect. |
| Use
soft spring to stabilize model |
Select this option to add soft
springs to stabilize inadequately supported models. |