Femap, Tips

Femap with NX Nastran allows some “cheats” to run certain types of dynamic analysis, even without the (as usual, very cost-effective) Dynamics add-on.

Firstly, given that Non-linear transient simulation is part of the standard capability, this allows a time history analysis to be run – and with the included multi-core / multi-cpu SMP capability.  The fact that a model may well include or not include any non-linearities is irrelevant – this solution method can be used to run time history dynamic analyses.  Structural damping, initial conditions, discrete dampers, remote masses – key ingredients of many dynamic analyses – can be included when creating a non-linear transient simulation.  The Dynamics Add-on has the benefit of adding modal transient analysis (modes superposition method for “linear” dynamic problems), which is numerically very efficient compared to solving the full equations of motion.

Secondly, Femap itself has an in-built method for doing frequency response analysis as a post-processing method subsequent to natural frequency analysis.  This is accessed via Model | Output | Forced Response.  Typical inputs (apart from previously running the natural frequencies) would then be: damping (eg. vs frequency and/or overall); loads (which become harmonic loads for this analysis); and frequencies for which response results are required.  Depending what result types are required, the natural frequency analysis may need to have additional result types requested.  Output can be in the form of results at different frequencies, or functions (graphs) of response quantities vs frequency.

Again, the Dynamics Add-on provides the incremental benefit of more efficient runtimes for big models (plus random response analysis, response spectrum, damped natural frequency analysis, and certain types of acoustics simulation) – but it is worth knowing that a helpful collection of dynamics capability is available as-is.

Forced Response Analysis in Femap

Using Femap’s inbuilt capability to run Frequency Response analysis.


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