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Moment of Inertia

Moment of Inertia

Moment of Inertia

(OP)
Hello all, hope you are doing great.


I am building an spreadsheet to calculate the reactions on 3D bolt group and I would like to confirm an information.



I calculated the moment of inertia about the centroid of my bolts in all 3 planes, my question is:

Can I add Ixx from xy plane and Ixx from xz plane ? I have to come up with only 1 Ixx to calculate the constants.

Thanks !

RE: Moment of Inertia

not really sure what calc you're doing ... can you show the geometry ?

I'm not sure how you get two inertia terms for all three axes ? I'd've thought that there be only one term ... unless the plane of the fasteners is generally inclined (but then you'd transform loads into this plane ... won't you ?).

another day in paradise, or is paradise one day closer ?

RE: Moment of Inertia

(OP)
The geometry is a circle, the diameter of the bolt is 0.18 in^2.

my spreadsheet is enclosed. go to 3D bolt group and formulas and calcs tab

RE: Moment of Inertia

your attachment is a screen shot.

If you have a bunch of bolts on a PCD, then you have Ixx = sum(A*y^2) = Iyy. You could calc Izz, but I'm not sure why you would (but in any case = 2*Ixx).

another day in paradise, or is paradise one day closer ?

RE: Moment of Inertia

yes, now you've linked your s/sht.

I don't know I'd consider the Z (= 4) term and calc Ixz and Iyz.

You seem to be doing a lot with this. I don't think I've ever seen people include the local I of the bolt (and just use Ay^2).

another day in paradise, or is paradise one day closer ?

RE: Moment of Inertia

(OP)
I see... I got some results that matches with other spreadsheets.

Thanks !

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