Sine-On-Random Vibration Analysis

[WolfgangFischer4396]

I have to run a finite element analysis on a helicopter mounted structure for the load as per the diagram attached. The load consists of a random vibration load and four frequencies of sinusoidal load. My questions are:
- Should I convert the sinusoidal loads into PSD and then run a random vibration analysis on all of it? If yes, how to convert the sinusoidal loads into PSD? I guess I have to define a sampling bandwidth?
- Or should I run a frequency response ("harmonic") analysis for the sinusoidal loads and a random vibration analysis for the PSD loads and then superimpose the results? Would the output of a SRSS superposition be valid?

I have submitted this request also to Autodesk Support

[Andrew.Sartorelli]

Hi Wolfgang,

I thought I would provide the community with part of my response from your technical support case. In order to introduce the harmonic loads into the PSD you would need the sampling bandwidth (units of delta-Hz) to be able to add the loads. Generally speaking, this sampling bandwidth is something that the test engineer would document however its not often included in reports for whatever reason.

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