Weakest Point of Cylinder in Pressure Piston Homework

In summary: It seems like you don't have enough knowledge yet to solve this problem properly. There is going to be a hoop stress in the cylinder wall, and there is going to be an axial stress. These need to be taken into account in evaluating the failure of the cylinder wall. You would also need a failure criterion expressed in terms of the principal stresses.
  • #1
FG314
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Homework Statement


In a cylinder & piston system, where is the weakest point on the cylinder (the point that will break under increasing pressure)?
You may assume the joint between edges are as strong as the material.
This is homework for A-level students.

Homework Equations


P = F/A
Surface Area of Flat Surface= πr2
Surface Area of Curved Surface = 2πrl

The Attempt at a Solution


F = PA, if 2l > r, then curved surface will face more force and will break first?
 
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  • #2
I'm not sure that the idea is to compare flat with curved. Maybe you are just supposed to consider different regions and/or different failure modes of the curved surface.
The failure mode of the flat surface is complicated. It depends on how the piston flexes.
Anyway, it isn't total normal force on the component that matters. Start with something simpler, like a sphere, and consider how it will fail.
 
  • #3
Does the cylinder wall have a thickness, or is it infinitely thick? Is the stress in the cylinder wall higher if the wall is thin or if it is thick? What course is this from? Is it Strength of Materials? Do you know how to calculate the stress in the cylinder wall? If so, what are the principal stresses on the inside and the outside of the wall?

Chet
 
  • #4
Chestermiller said:
Does the cylinder wall have a thickness, or is it infinitely thick? Is the stress in the cylinder wall higher if the wall is thin or if it is thick? What course is this from? Is it Strength of Materials? Do you know how to calculate the stress in the cylinder wall? If so, what are the principal stresses on the inside and the outside of the wall?

Chet
It is a homework that is supposed to be challenging and makes us think, AS level physics knowledge should be adequate. material for flat and curved surface is the same, with uniform thickness, and the joint is as strong as the material itself.
 
  • #5
FG314 said:
It is a homework that is supposed to be challenging and makes us think, AS level physics knowledge should be adequate. material for flat and curved surface is the same, with uniform thickness, and the joint is as strong as the material itself.
Have you learned about the concept of principal stresses?

Chet
 
  • #6
Chestermiller said:
principal stresses
nope. only basic pressure, and young modulus.
 
  • #7
FG314 said:
nope. only basic pressure, and young modulus.
It seems like you don't have enough knowledge yet to solve this problem properly. There is going to be a hoop stress in the cylinder wall, and there is going to be an axial stress. These need to be taken into account in evaluating the failure of the cylinder wall. You would also need a failure criterion expressed in terms of the principal stresses.

Chet
 
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Likes FG314

1. What is the weakest point of a cylinder in pressure piston?

The weakest point of a cylinder in a pressure piston is typically the point where the cylinder and piston interface. This is because this area is subjected to the highest stress and is where cracks or deformations are most likely to occur.

2. How can the weakest point of a cylinder in pressure piston be identified?

The weakest point of a cylinder in a pressure piston can be identified through stress analysis techniques and simulations. These methods can help determine the areas of highest stress and potential failure points.

3. What factors can contribute to the weakening of a cylinder in pressure piston?

There are several factors that can contribute to the weakening of a cylinder in a pressure piston. These include material defects, high operating pressures, fatigue from cyclical loading, and improper assembly or maintenance.

4. How can the weakest point of a cylinder in pressure piston be strengthened?

The weakest point of a cylinder in a pressure piston can be strengthened through various methods such as using stronger materials, increasing the thickness of the cylinder walls, adding reinforcements, and improving the design to distribute stress more evenly.

5. Can the weakest point of a cylinder in pressure piston be completely eliminated?

While the weakest point of a cylinder in a pressure piston can be strengthened and minimized, it cannot be completely eliminated. The nature of high-pressure systems means that there will always be areas of stress concentration and potential failure points. The goal is to reduce these points to a safe and manageable level.

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