Bearing stress in a single shear lug loaded by moment and force 4

[joydeutch]

Dear all,

This is my first post and I would like to say hello to everybody
I m an aeronautical engineer working at the moment in a spacecraft project and I have the following question:

I m not able to find any reference to justify the bearing stress in case of a single shear lug loaded through a pin by a shear load (with an offset) and a pure bending moment.

Thank you a lot for your help

Best regards

joy

 

[rb1957]

i take it the moment is out-of-plane (the shear load is off-set out of the plane of the lug) ?

the direct shear bearing is simple (either uniform or cos(theta)), right? for the moment i'd say the pin has a typical bending stress distribution, which for the bearing would be contact loads on opposite sides, varying linearly to the mid-thickness. so the moment becomes a set of forces, and make an equivalent set of bearing loads (ie like the shear load)

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

 

[stressebookllc]

No what he means is that at the lug hole due to the offset loading there will be a moment due to the bolt bearing on opposite sides of the edges of the hole.... if I understood it correctly. Its a bad design.

http://www.stressebook.com

Stressing Stresslessly!

 

[rb1957]

yes, the pin is cantilevered in the lug (out-of-plane of the lug, with the shear force parallel to the plane of the lug) ... yes?

joy (OP) ... maybe a pic ?

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

 

[KSshopper]

Single shear lugs are addressed in section 9-5 of the Air Force's "Stress Analysis Manual" by Maddux. A pdf can be downloaded at: Link

 

[stressebookllc]

Looks like a busy person rb1957..

http://www.stressebook.com

Stressing Stresslessly!

 

[joydeutch]

good morning all!

thank you a lot for your tips

the scenario it is like that depicted in the attached file.
the pin is cantilevered in the lug (out-of-plane of the lug, with the shear force parallel to the plane of the lug)

I used the method described in the HSB 26101-01 issue D year 1999, and I get a positive margin of safety but I m going to check also the "Stress Analysis Manual" by Maddux

have a nice week
joy

 

[joydeutch]

here the picture
,-)

 

[rb1957]

recognise that the sketch is a very simplistic "cartoon" of a structure. in the real world i'd expect much more "stuff". i don't think designers like to rely on bore loads (bearing) to react bending and would rather use nuts or shoulders to locate the pin and to fix the pin onto the plate (so that the moment would be transferred into the plate via the nut faces).

but that is what i thought you were talking about. it should be a simple summation of bearing loads, a uniform one for the shear and two triangluar dist'ns for the beaning, yes?



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

 

[RPstress]

In the past we've used a distribution like the attached and compared the load per inch with the allowable lug load per inch. This is safe and has been used in cert calcs.

 

[stressebookllc]

Nicely done RPstress. I like the method.

http://www.stressebook.com

Stressing Stresslessly!