Thank you for your response. The pure Longitudinal stress is PD/4t, but if there are other longitudinal pressures/stresses induced on the tube how can I account for these? I need to know this, in case it becomes larger than the circumfrential stress, and will therefore be the failure mode.
Up to now I have used the hoop sress formula, PD/2t, to calculate the bursting pressure of pressure vessels. But how can longitudinal forces be accounted for? For example a hydraulic cylinder which has 200 bar hydraulic pressure, and is creating a force of 4 tonnes between fixing pins.
If you're a practical guy and you want less academic answers, here's my side of the story. You can try looking up for the torque values (in manufacturers' catalogs) of the standard nut corresponding to the thread of the bolt you use. Of course you should find the value for the nut with the...