Why Do Stress Levels Vary Between Two Gauges on a Thin-Walled Pressure Vessel?

[imnotadmin]

pls help-- thin-walled pressure vessel

Hi, all. I have done an experiment of “thin-walled pressure vessel”. The vessel: length 200mm, outside radius 526mm, inner radius 47.6mm. There were two rectangle rosettes gauge in the vessel surface. Based on the experiment data (100 psi), the actual principle stresses of the two gauges are calculated: 1) 72 Gpa (hoop) and 37 Gpa (axial). 2) 66 Gpa (hoop) and 32 Gpa (axial). And the theoretical principles are: 62 Gpa (hoop) and 31 Gpa (axial).

I am wondering why the stresses of gauge one are mush bigger than the gauge 2. Can somebody tell me why?


Thank you very much!

 

[imnotadmin]

Sorry I put a wrong data in the first thread. The diameter of the vessel is 100mm and the thickness is 0.55 mm. The r/t = 90. I have checked a textbook and it mentioned " when r/t =10, the results of a thin-wall analysis will predict a stress that is approximately 4%. For larger r/t, this error will be even smaller."

So I don't understand why the stress of rosettes 1 is so much than rosettes 2 and the theoretical values.