Hydraulic cilinder 2

[Johnatan88]

Hello guys,
this is my first time here take an apology if I choose wrong section of forum.
I just want to know should in shell of hydraulic cylinder (as in presses hydraulic cylinder) should longitudinal/axis stress be analyzed beside radial and Circumferential/hoop stress and take in consideration.
I searched everywhere and couldn't find answer. I know that longitudinal stress is not important for open end cylinder such as gun barrel, but what about hydraulic press cylinder??

Thanks in advance

 

[JStephen]

For something like a pressure vessel, where both ends are closed, the longitudinal stress is only half the circumferential stress. It still needs to be considered, but usually doesn't control the design.

For a double-acting hydraulic cylinder, you'd get longitudinal tension on the wall when retracting?

 

[Johnatan88]

Yes, this is double-acting cylinder. I was working on something and I cant figure it out.
So longitudinal stress should be considered(I mean they're not zero) for double-acting cylinder?

 

[zeusfaber]

So longitudinal stress should be considered(I mean they're not zero) for double-acting cylinder?

Absolutely. When you're pressurising the annulus with the rod in tension, the load path is through the rod, then through the fluid (in compression) onto the neck bush and down the length of the cylinder (in tension) into the cylinder mounting.

This applies whether you're pulling a load in, or braking an overhauling load as it pulls the rod out.

A.

 

[Johnatan88]

And one more question. Is cylinder like this considered as closed end cylinder:

I couldn't find anywhere exact definition what is closed end and what open end cylinder.

P.S. It's maybe obvious for you but I'm not that experienced and English is not my first language.

 

[zeusfaber]

That one is closed at both ends. There's a space at the rod end (between the upper piston seal and the rod seal) which is "closed" to the extent that you can pump oil into it under pressure without oil squirting out past the rod.

By contrast, single acting cylinders are "open" to the atmosphere at one end. There's nowhere to pump oil in; if you did, it would just come out again and, importantly, you can't pressurise that end of the cylinder.

A.