Surface Pressure 1

[daparojo]

I am wondering if you could help.

I have a component (Female Cover) that has a parallel OD and a Taper Bore. The Taper Bore inner surface is subject to a constant pressure due to a component (Rod) that slides inside the bore, with a corresponding male taper (similar to a morse taper). The whole assembly is then inserted into a bore of a jig under a clearance condition (0.06mm) . The Rod is then tightened to created an axial movement that in turn expands the Female Cover into the Bore to create an interference fit.

Bore = 40mm
Clearance = 0.06mm
Load Required to expand the Female Cover 0.06mm = 130 kN
Interface Pressure Between Female Cover / Rod = 80 N/mm2 - this is based on Thick Walled Cylinder Theory

What I require is the Interface Pressure between the Bore/Cover.

My theory is that it will be less than the Interface Pressure between the Female Cover / Rod. But by how much?

My thought is to take the ID of the mid point of the Taper Female Cover and calculate the area.

Then Calculate the area of the hole (the Female Cover expands to fit the Bore).

So my calculation was to take the Interface Pressure Cover/Rod X Mid Area Female Cover

Then divide the result by the larger area of the Bore to get a rough Interface Pressure between the Cover OD and Bore.

Am I on the right lines?

 

[Compositepro]

Your calculations are entirely theoretical and leave out so many factors that I cannot see much usefulness in your exercise. How accurate do the answers have to be and how will the answers affect what you do next?

What about the modulus of all the materials, thermal expansion coefficients, friction, creep, dimensional tolerances etc. In the end you will have to test.

 

[LittleInch]

If I understand this right in essence you have a tapered piston inside a cylinder with a small clearance (60 micron). This inner hollow piston is being expanded as a result of a tapered rod being pushed into the hollow piston

~As there will be no pressure between the piston and the cylinder until the piston has expanded 60 micron, the pressure on the piston to cylinder will be much less than the piston to rod pressure. At an expansion of 59 micron there is, in theory, no pressure between the piston (female cover) and cylinder.

How much pressure the piston can exert is variable by how much more force is exerted on the rod beyond the expansion of the piston by 60 micron. At a crude level this is a force diagram based on the angle of the taper.

Once you reach touching between the piston/cover and the cylinder then all the additional pressure exerted on the inner taper should then transfer to the piston / cover interface.

There are though a lot of variables here including true roundness of the components, surface friction between the rod and the piston etc.

A drawing and force diagram would help.

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