May 18, 2022 at 8:10 am

albin.linderstam

Subscriber

*Further questions (not enough room in one post):***Question 4: Type of support**

PSD G Acceleration ÔÇô Should I always select

*All Supports*here? All Ansys-videos I watched have used

*All Supports*, but they are not specific about why. LetÔÇÖs say that IÔÇÖve used fixed support in my modal analysis, will it make any difference if I use Fixed Support or All Supports?

**Question 5: Random vibration in x,y,z**

Can I apply PSD G Acceleration in X, Y and Z during same simulation or do I need to take them separately? I assume separately. What is happening when I use PSD G in x,y,z simultaneously? I notice that the results change a bit.

https://forum.ansys.com/discussion/10768/combining-multi-axis-psd-vibration-results

**Question 6: What does the PSD Tool tells me, i.e. what does the PSD counts tell me? I've problem understanding this, perhaps one can use the curves below to ease explanation.**

According to Mechanical User’s Guide: “You can apply a Response PSD Tool to any Random Vibration analysis (only) in order to control the frequency sampling of Response PSD probes.”

This is result when performing PSD G Acceleration in X/Y/Z-direction, see below. I assume that one only examine the Response PSD in the direction of the PSD G Acceleration, one at a time.

Since this Response PSD is measured on a vertex, is it the same as when we apply accelerometers (x,y,z)?

**X:**

**Y:**

**Z:**

**Question 7: What is your recommendation, total deformation and equivalent stress in 1-sigma, 2-sigma or 3-sigma? It seems conservative to use 3-sigma (which is easier to motivate).**

Meachanical User’s Guide: “Meaningful equivalent stress is computed using a special algorithm by Segalman-Fulcher. Note that the probability distribution for this equivalent stress is neither Gaussian nor is the mean value zero. However, the “3 σ” rule (multiplying the RMS value by 3) yields a conservative estimate on the upper bound of the equivalent stress.”

Kind regards

Albin