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Kt for filled hole
- Thread starter jetmaker
- Start date
Hi Jetmaker
If one looks at the SF at a hole, as per Niu, "Airframe Structual Design" (blue/green book) pp 238 et seq., then the full Kt at the hole is assumed inside the parenthesis of the SF formula. But the severity is reduced by the alpha and beta factors which account for the condition of the hole and the fit of the fastener. With no other reference that I can think of immediately, I would use this approach.
Hope this helps.
Regards,
Ed.
If one looks at the SF at a hole, as per Niu, "Airframe Structual Design" (blue/green book) pp 238 et seq., then the full Kt at the hole is assumed inside the parenthesis of the SF formula. But the severity is reduced by the alpha and beta factors which account for the condition of the hole and the fit of the fastener. With no other reference that I can think of immediately, I would use this approach.
Hope this helps.
Regards,
Ed.
- Thread starter
- #3
Hi Guys
Just to put my two cents in, I have had hundreds of coupons tested for different types of joints with both rivets and hiloks (different rivet types: ie solids and blinds; and different bolts as well). Both the Kt and the stress intensity are affected by two factors not just one. The interference of the hole and the clampup force. So, this being said and since these are both dependant on installation, each manufacturer generally performs tests to their own fastener installation specs to obtain this data. In lieu of this, there are various mathematical and fem models for determining the impact of interference on both kt and stress intensity which when validated against test data can provide good reliable results. Clampup is an entirely different matter and for rivets it depends on squeeze force and for bolts of course on collar shear off values. The alpha and betas in Niu book are good "approximations" but are not absolute by any means. Hope this info helps.
James Burd
Just to put my two cents in, I have had hundreds of coupons tested for different types of joints with both rivets and hiloks (different rivet types: ie solids and blinds; and different bolts as well). Both the Kt and the stress intensity are affected by two factors not just one. The interference of the hole and the clampup force. So, this being said and since these are both dependant on installation, each manufacturer generally performs tests to their own fastener installation specs to obtain this data. In lieu of this, there are various mathematical and fem models for determining the impact of interference on both kt and stress intensity which when validated against test data can provide good reliable results. Clampup is an entirely different matter and for rivets it depends on squeeze force and for bolts of course on collar shear off values. The alpha and betas in Niu book are good "approximations" but are not absolute by any means. Hope this info helps.
James Burd
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