Washer as load bearing element (analysis)

[ERCPT]

I'm having some difficulty approaching the stress analysis of a washer with a load applied uniformly over 360 degrees.

The setup is a washer held against the end of a 24mm shaft via a standard machine cap screw. On the shaft is a cylindrical mass which sees a load (Mass OD > Washer OD, Mass ID =24mm)). If you want a number, we'll say 1500lb-f total from the mass onto the washer.

Arbitrary washer dimensions are t=2mm (thickness), D1=6.4mm (ID), D2=26mm (OD).

Primary shear is easy (F/2*(pi)*r*t) with r=12mm, but bending stress is giving me a headache.

Any thoughts on how to approach this? Since the bending is evenly distributed to every point along the 360 degree ontact area, would integrating the standard bending stress equation (stress = Mc/I) do me any good? I'd hate to go through the motions and find it a waste of time, as it would appear at first to be a difficult problem to set up.

Thanks in advance for your input.

 

[israelkk]

This is a simple case of a circular disc supported on the OD or ID and uniformly loaded in the OD or the ID. See Roark's book Formulas for Stress and Strain (any version) for an analytic solution.

 

[CoryPad]

Yes, Roark's shows this case. They have the bending stress formula as:

[σ] = 6M/t²

M varies with loading conditions.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[rb1957]

uh ?

doesn't a washer have load applied on one face, it appears by a nut about the size of the washer (so the load isn't concentrated on a part of the washer) and isn't this load reacted by a distributed pressure on the other face of the washer ...

it looks to me like loadin = load out and the washer isn't doing much to move the load around ??

 

[MotorVib]

So one bet me to it Roark's has a section with nothing but loading like that.

Chris

"In this house, we obey the laws of thermodynamics." Homer Simpson

 

[ERCPT]

Thanks for the tip, Israel/Cory!

This is a resource I'm not familiar with currently, but will look into.

Rb, this setup is not the generally accepted use for a washer . I'm just trying to get away with a cheap solution.

Thanks all.

 

[rb1957]

"this setup is not the generally accepted use for a washer" ... from your description, the washer is acting as a packer. is the washer taking a concentrated load (near its ID) and reacting it near the OD ?