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# Help in calculating fastener flexibility values in fastener joints

## Help in calculating fastener flexibility values in fastener joints

(OP)
Hello folks,
Firstly, this is mainly a FEM & specifically Nastran question but since it is almost used exclusively used in Aerospace industry (?), I thought it would be more appropriate here rather in the FEM sub-section of the forum. I can move there if deemed necessary.

I have a question on calculating fastener shear flexibility values for Nastran CBUSH element using Huth equation under a double shear setup.

I have created an image which hopefully will convey my question clearly.

So essentially my question is, does the industry use:

1. n=1 (i.e. single shear condition) for each CBUSH element and consider thickness of one of the plates as 't/2' during calculation of fastener shear flexibility using Huth equation?

2. n=2 in Huth equation for each CBUSH element?

Thx,
- B

### RE: Help in calculating fastener flexibility values in fastener joints

I'd say you're modelling both sides of the double shear as two single shear fasteners, so 1)

### RE: Help in calculating fastener flexibility values in fastener joints

(OP)
RB1957, thx for your response. Got me thinking to modify my question.

Just wanted to cast a wider net on my original post like which way is a double shear fastener FE modelled in Industry. As two single shear spring elements? Or is there a better way?

### RE: Help in calculating fastener flexibility values in fastener joints

(OP)
Folks, any suggestions on the above?

Thx,
- B

### RE: Help in calculating fastener flexibility values in fastener joints

I was wondering if you could use a CBUSH ? and maybe the dbl shear stiffness ??

### RE: Help in calculating fastener flexibility values in fastener joints

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