Normal Modes, mass density or weight density?

[stressebookllc]

In a normal modes analysis, do you use PARAM WTMASS all the time or are there instances where you choose to use weight density?

Param WTMASS is generally set to 1/386.4 in english units. It converts the material densities to mass density when you use weight density in the material definition.

I was told it is always best to use mass density for normal modes.

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[nlgyro]

f = sqrt(K/m) , where m = mass NOT weight.

 

[stressebookllc]

Cool. Simple and to the point, boy that was embarrassing,

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