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[FAQ]

Grms is a relative feel. For an example, if you have cantilever beam subjected to 1000 N tip load in case-A and in case-B the same cantilever subject to 5000 N tip load. Now you will get a feel that Case-B loaded heavier than Case-A. Grms is used to qualitatively access both the Input PSD and Response PSD (RPSD). For an example, you have bracket mounted on a chassis subjected to base excitation, which is specified in terms of PSD and your objective is to access a bracket design through PSD analysis. Let say, this bracket is to be accessed for two different road conditions 1) Smooth Highway road < PSD-A input curve> 2) Rough Off road . For both the PSD-A input curve and PSD-B input curve, Grms-A and Grms-B can be calculated respectively, as explained here (https://www.vibrationresearch.com/public_pdf/RandomRMSCalculation.pdf). More the Grms heavier the loading, again; its a relative feel. Like for input PSD, from the RPSD also Grms can be calculated. For an example ; for ONE give input PSD profile, you want to ascertain 2 different bracket design. After doing PSD analysis for both the brackets you will give two different RPSDs one from each bracket. Now you can also calculate two different Grms (output / response). Among there Output Grms values, higher Grms bracket qualitatively tells that there is more dynamics magnification, compared to other bracket. Just with the Grms value, an engineer can’t understand any thing, more details should be accompanied along with Grms.