Forces on a rod through a pressurized container

In summary, the conversation was about the effects of pressure on a rod inside a container with a hole. One person argued that the pressure would cause the rod to compress, while the other believed that a measurement device placed inside the rod would measure a force equal to the pressure acting on a cross-sectional area of the rod. A book suggestion was given for further reading on the topic. The question was then raised about the relationship between stress in the rod and the force of pressure on a cross-sectional area. This is known as the "pinch-off" effect and can also occur in high-pressure vessels with O-rings.
  • #1
Hi!

A colleague and I were discussing pressures and forces when we arrived at a special situation where we do not fully agree and would like some help to better our understanding.

Imagine a box/container with a hole in the middle of two of the opposite sides. A rod/cylinder goes fully through the box through the holes, which are fitted with frictionless seals around the rod (idealized situation). The pressure inside the container is Pbox and the length of the rod inside the box and diameter of the rod is Lrod and Drod respectively.

The question we were discussing is what will happen to the rod when pressure Pbox is applied inside the box. My colleague argued if a measurement device were to be fitted inside the middle of the rod it would measure a force equal to what would be expected if the pressure were acting on a cross sectional area of the rod. I argued the increase in pressure would compress the rod slightly and that the stress/strain regime would be a function of the length of the rod, the surface area and the pressure inside the box.

I have attached a crude drawing of the situation and would appreciate any feedback on this.

Rgrds
mkartevoll
 

Attachments

  • rod in pressurized box.png
    rod in pressurized box.png
    2.8 KB · Views: 490
Physics news on Phys.org
  • #2
I see now I might have posted this question in the wrong forum! Is there a way to move it or should I delete it and post it again somewhere else?
 
  • #3
It counts as Gen. Phys.. See P. W. Bridgman, The Physics of High Pressure, for "pinch-off" effect.
 
  • #4
Thank you for the book suggestion, I will look into that when I can get myself to a library. If you are familiar with the parts of the book, do you know if the stress in the rod due to the pressure in the box would be equal to the force the same pressure would exert on the area of a cross section of the rod? Or is it a bit more complicated than that? Please excuse me if I am using the wrong terms in my questions, It's been a while since I studied and I think I might be mixing terms together.
 
  • #5
mkartevoll said:
the stress in the rod due to the pressure in the box would be equal to the force the same pressure would exert on the area of a cross section of the rod
This is pretty much it, the "pinch off" effect. It also occurs in O-rings placed in high pressure vessels.
 

1. What is the purpose of a rod in a pressurized container?

The rod provides structural support and helps distribute the forces exerted by the pressurized contents evenly throughout the container.

2. How does the pressure inside the container affect the forces on the rod?

The higher the pressure inside the container, the greater the force that the rod must withstand. This is because the pressure acts on the entire surface area of the container, including the rod.

3. What factors can affect the forces on a rod inside a pressurized container?

The size and shape of the container, the material of the rod, and the magnitude of the pressure are all factors that can affect the forces on the rod.

4. How can the forces on a rod be calculated in a pressurized container?

The forces on a rod can be calculated by using the formula F = PA, where F is the force, P is the pressure, and A is the cross-sectional area of the rod.

5. What safety precautions should be taken when working with pressurized containers and rods?

It is important to ensure that the rod is strong enough to withstand the forces exerted by the pressurized contents. Proper training and safety gear should also be used when handling pressurized containers to avoid accidents and injuries.

Suggested for: Forces on a rod through a pressurized container

Replies
12
Views
2K
Replies
22
Views
2K
Replies
23
Views
2K
Replies
13
Views
1K
Replies
15
Views
1K
Replies
7
Views
1K
Back
Top