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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

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