Stress Analysis of the Middle Ring

Since the middle ring has an extensive cut across the midplane on both sides as well as entrance and exit holes and loaded with about 25,000 lbs, calculations of the stresses and deformation of the midplane support area of the middle ring and deflection of the window opening were made using the finite element analysis code ANSYS . The work was conducted by a graduate student in the Department of Civil Engineering at the University of Virginia and a REU student. A scaled down model of the middle ring was constructed and then tested by applying forces to it using the Materials Testing Service of the Department of Transportation at the University. ANSYS was first checked by comparing calculations of the test model deflections to the actual data. Agreement was within $\pm$10%. Results of ANSYS for the target chamber showed that the maximum deflection of the opening of the window in the middle ring varied from 0.007 $in$ to 0.015 $in$ depending on how the middle ring was loaded. This was decided to be a safe limit. In the final design, several movable 7 $in$ long, 2 $in$ diameter aluminum support rods are placed in the window for added support. In addition, flanges defining the ports and coupling to the spectrometers can be added, giving additional support to the middle ring. Compressional stresses, calculated using ANSYS assuming the middle ring was attached to the top hat and loaded with 25,000 lbs, were less than 3000 psi almost everywhere. However, stresses over small areas rose to levels 6000 psi near the entrance and exit holes. These calculations indicated that we did not exceed the safety limit of 15,000 psi for aluminum. A simple model calculation shown in Appendix A gives the result 1434 psi, which represents some average value over the midplane contact area.