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Shock Absorber Valve Shim Deflection Formula
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Posted by: jamiedaugherty

01/12/2009, 08:10:43

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I'm wanting to develop a formula (or series of formulas) to predict the behavior of shock absorber valving. Ultimately what I would like to do is be able to generate the velocity of the shaft under a given load for a particular valve configuration. To begin with I'd like to develop a means to determine the deflection of the valving shim stack.

For those who are not familiar, a modern shock absorber uses a valve piston that flows the oil freely in both directions. The ports in the valve are capped with a stack of thin shims when, under pressure, will deflect to open the ports and allow the fluid to pass.

What you have is a situation where the shims are deflecting under a constant distributed load (the fluid pressure coming through the port) but not over the entire 360 of the face (ports are not totally annular). The last part I'm not that concerned with as I think I can take care of it separately. I've thought about using the disc spring formulas but 1) none that I have found show deflection for a distributed load over the face and 2) the shim starts as a flat and bends upward, which is the opposite of the disc spring.

I'm almost sure that I've seen something on here before concerning this but I was unable to find it in a search. Please help!








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: Shock Absorber Valve Shim Deflection Formula
: Shock Absorber Valve Shim Deflection Formula -- jamiedaugherty Post Reply Top of thread Engineering Forum
Posted by: jamiedaugherty

01/13/2009, 12:39:28

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As a follow up, I have found the following information on eFunda:

http://www.efunda.com/formulae/solid_mechanics/plates/calculators/apFC_PRing.cfm

I think this is real close. The only problem I can find now is that the valve shims are stacked 6+ per side. These shims are decreasing in diameter. The formulas in the link are ok for a single shim, but what about multiple shims in series? I'm hoping someone can give me some guidance so I don't have to work this out the hard way!

Thanks!!!








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