HELP: contact area of Cylinder inside a larger Cylinder?

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Discussion Overview

The discussion revolves around determining the contact area of a smaller cylinder positioned inside a larger cylinder. Participants explore different interpretations of "contact area," including whether it pertains to surface area or volume, and consider the orientation of the cylinders (vertical vs. horizontal) in their analysis. The context includes theoretical considerations and potential practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant seeks clarification on the definition of contact area, questioning whether it involves volume or just surface area.
  • Another participant suggests calculating the contact area as the area of the bases of the smaller cylinder if the cylinders are oriented vertically.
  • A different viewpoint indicates that if the cylinders are horizontal, the contact area may be negligible, potentially reducing to a line of contact.
  • There is a query about whether the contact area of a cylinder resting on a plane is equivalent to that of a cylinder inside another cylinder with a slightly larger inner diameter.
  • One participant proposes a limit approach to define the contact area mathematically.
  • A later reply asserts that if both cylinders are assumed to be perfectly rigid, the contact area would be the same in both scenarios, but acknowledges that real cylinders are flexible, suggesting that this complicates the analysis.

Areas of Agreement / Disagreement

Participants express differing views on the definition and calculation of contact area, particularly regarding the orientation of the cylinders and the assumptions about their rigidity. No consensus is reached on the correct approach or interpretation.

Contextual Notes

Participants note the importance of assumptions regarding the rigidity of the cylinders and the orientation in determining the contact area, highlighting that real-world conditions may affect the theoretical calculations.

mhl
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Laydies and Gents

can anyone help me here? suppose there are well known formulas for this.

That is, contact area of a known size cylinder lying inside a larger know size cylinder...

hope problem is clear

thank you

best regards

martin
 
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Contact area? is it involving volume or just area? or sth other than pure value of area?
my guess is that, let CyLarge and CySmall,
so if u re finding volume, calculate the CyLarge volume subtract CySmall volume.
if it's area, CyLarge Area - CySmall Area.

sorry if i misreading ur question. =)
 
Hmm. To clearify:

I am tryoing to find the contact area of a given cylinder that is lying inside another cylinder. That mean the outside area of the smallest cylinder touching the inner wall of a known larger cylinder.

Ex: a 1 meter long cylinder with 5" diameter lyes inside a 1 meter long cylinder with 7" diameter. What is the contact area between the two cylinders...?

hope this was better.
 
No, it isn't. If the two cylinders have their axes vertical, under gravity, then the "contact" area is just the area of the two bases of the smaller cylinder:49 \pi m^2. If the two cylinders have there axes horizontal, then there would be a very slight contact between the curved areas. Although, I suspect that in ideal cylinders, that would just be a single line of contacet, having 0 area: so we are back to 49\pi m^2.
 
mmm, yes hallsofivy, that was my though as well (the axis are horizontal, they are lying down i guess).

Still, does that mean that a given cylinder, for example OD of 1m, lying on a straight plane has the same contact area to it's underlayer (tha plane) as the same cylinder lying inside a cylinder with ID of 1.001m? (all things ideally and so on and so fourth)...

thoughs...?
 
Would it be a limit? like lim as deltaX approaches 0 of (Xo * Height)?

(please excuse notation)
 
mhl said:
Still, does that mean that a given cylinder, for example OD of 1m, lying on a straight plane has the same contact area to it's underlayer (tha plane) as the same cylinder lying inside a cylinder with ID of 1.001m?

Yes, if you assume both cylinders are perfectly rigid.

For real cylinders the answer is no, because they are flexible. Google for "Hertz contact" for more about that.
 

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