Snap Fit Design - Insertion Force and Bending Force

[E-N-E ENG]

Anyone can help on how this equation is derived?

Thank you

 

[SWComposites]

Where is mu defined?
Seems like there should be more equations that use all of the variables.
Where did your equation come from?

 

[E-N-E ENG]

Where is mu defined?
Seems like there should be more equations that use all of the variables.
Where did your equation come from?

Hi,

Friction is along the angled surface.

This equation from the snap fit design on fictiv.

 

[E-N-E ENG]

 

[E-N-E ENG]

Another reference.. slightly different equation

 

[HTURKAK]

Draw the FBD of inclined surface and write the equations of equilibrium ,
- μ is the friction btw the contact surfaces ,
- N is the vertical component to the inclined surface of P
Sum of the forces on X axis ;
Σ F x =0 = Fi- μN*Cos (α)- N*Sin (α) >>
Sum of the forces on Y axis ;
Σ F y =0 = N*Cos (α)- μN*Sin (α) -P
Combine these two equations and get the force F

Fi= P ( μ*Cos (α) + Sin (α) )/ ( Cos (α)- μ*Sin (α))
Then divide nominator and denominator to Cos (α)

Fi= P ( μ +TAN (α) )/ ( 1 - μ* TAN (α))

I could not find the mistake but this should be the way to derive.

P.S . = I assumed the driving force is Fi.

EDIT:Today Morning ,When i was preparing my post there were only OP 's post and SWComposites' post and my respond was the second.Later i looked to the Thread and see that my post is the 4th respond. If somebody out there can explain what could be the reason ?

​

 

[GregLocock]

"Another reference.. slightly different equation"

That word slightly is doing a LOT of work. Consider the case where mu=1 and alpha = 45 degrees. (this makes me think the - sign in the denominator is correct)

 

[HTURKAK]

Another reference.. slightly different equation

JO ENGINEERING ,

Another reference somehow different.

In your first and second post i understood that the object is movable and pushed by Fi insertion force .

Now i understand that the object could be fixed at left and a bending force P is applied.
Both cases seems similar but the resisting friction force direction will change .

If the object is fixed and a bending force P is applied , the original expression with (+ sign ) in the denominator is correct.

Kind regards.