You can use output filters to filter the output generated by the solver as well as to perform operations on the generated output. You can filter element and nodal field output before it is written to the simulation results. Typical output includes element, nodal, contact, integrated, and fastener interaction history. You can also operate on filtered or unfiltered (raw) output data to extract the maximum, minimum, or absolute maximum of the output variables over time. In addition, you can specify a limit value for the output variables, and you can stop the analysis when it reaches the limit. Note:
If you stop the analysis before reaching the
specified limits, Mechanical Scenario Creation writes an additional field frame to the output file, along with the expected
output variable from the original request. For example, if you were filtering on RM reaction
moments and stopped the analysis early, Mechanical Scenario Creation might also provide RF (reaction force) results to the output.
Mechanical Scenario Creation supports the use of the Operator, Butterworth, Chebyshev type I, and Chebyshev Type II filters. You can use low-pass Infinite Impulse Response filters such as Butterworth and Chebyshev filters to filter output variables susceptible to noise, such as accelerations and reaction forces or, to a lesser degree, stress and strain. However, digital filtering (such as the Operator filter) might be preferable for most element and nodal output variables as you can apply bounding values on unfiltered data for these output variables. The Butterworth, Chebyshev Type I, and Chebyshev Type II filters differ in their characteristic responses in the pass band and the stop band frequencies. The pass band is the range of frequencies that can pass through a filter. The stop band is a range of frequencies, between specified limits, through which a filter blocks the signals. The Butterworth filter is a type of signal processing filter with a maximally flat frequency response in the pass band. As compared to the Butterworth filter, the Type I Chebyshev filter has a sharper transition between the pass band and the stop band, with a ripple in the pass band. Like the Type I Chebyshev filter, the Type II Chebyshev filter also has a sharper transition between the pass band and the stop band than a Butterworth filter of the same order. The difference is that the Chebyshev Type II has a ripple in the stop band. Antialiasing filters filter the output based on time intervals. With the antialiasing filter, the cutoff frequency is specified internally to one-sixth of the time frequency (the time frequency is the inverse of the time interval, t, used for history output). Note:
The antialiasing filter is a second-order Butterworth type filter and does not
require you to specify a filter definition.
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