Stress Analysis from internal pressure

[karthur1]

I am trying to model the stress in a hydraulic cylinder/ gland assembly.  I would like to see how the cylinder will buldge when hydraulic pressure is applied. I can build the model and apply a fixed constraint between the two parts, but I would like to model it more "Real World" where the gland bolts are holding the cylinder in place.

I know that when internal pressure is applied, the cylinder buldges outward, the OD of the cylinder will heal off on the gland.  The ID of the cylinder will tend to lift away from the gland as the end of the cylinder face tilts over. 

I have tried several different ways to apply constraints to this, but it is either over constrained or under constrained.  Is there a way to constrain the OD of the cylinder to the gland, but still allow the face of the cylinder to tilt.

Any help would be appreciated.  Model attached.

Thanks

[johnsonshiue]

Hi Kirk,

Instead of using Fixed constraints, you might want to apply Pin constraints in those holes. It would simulate more like real world when the bolts are holding the parts in place. Do you get the more desirable results?

Many thanks!

[admaiora]

Hi Kirk,

Why don't you have applied the pressure in the upper surface too?

Avoid to fix edges ( or points)

You can apply a fixed constrain in the bolted surfaces, or , as suggested, and closer to reality a pin constraint, where you can control the 3 degree of freedom (axial, radial, tangential).

That in general works fine, for more complex analysis and cases/behaviors you can specify the contact behavior (sliding, separation, etc)

[karthur1]

I wasn't getting the results that I wanted and I would like to see the stress in the connecting bolts as well.  So I modeled the bolts and put them into the assembly.  I placed a bonded constraint between the bolts and the threaded holes and a "sliding/no separation" between the bolt head and the gland.  This seems ideal, but when I run it, it shows a warning "Model separates into 2 independent components" (see attached model). 

I also don't see the bulge in the cylinder now that I would expect and that was shown in the previous simulation.  How do I constrain this to simulate whats happening under this load?

When the bolts are torqued, it will place an initial clamping force on the cylinder.  Is there a way to simulate this also?

Thanks