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dustball23
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- TL;DR Summary
- I wish to compare the bending stress of 2 different designs.
- In both designs, a PVC pipe is being bent 90 degrees, fixed at each end.
- In both designs, the pipe is fixed at both ends.
- In both designs, the pipe is 1" (inner diameter) Schedule 40 PVC pipe, 450 PSI. Material code PVC 1120. NSF pw-G ASTM D1785 PPFA 02199101H6BX 0934.
- In design A, the length of the pipe that bends is 7.75'. (The actual pipe is 10' long but the ends will not bend much for two different reasons. The one end slides over a 1' pole to hold it in place. The other end slides 1.25' into a larger pipe. So the middle 7.75' must bend 90 degrees.
- In design B, the 10' pipe is cut in half, and a 2' rigid outer sleeve joins them in the middle. So the part that bends (the 7.75' from the original design) is now only 5.75' - but really two separate sections of 2.875' each.
Design A will last longer because there is less bending stress. Design A is a well known and well-tested design for temporary shade structures in the desert. Design B is easier to transport because the 10' pipes are cut in half, but will fail earlier because the pipes will get bent too much too early. How much additional bending stress is happening? (Typically, these structures are used 10 days a year, and will be reused every year until the pipes get too bent.)