Hi there, I'm a university student and am stuck regarding a literature review for my individual project. I was given a schematic sketch of the setup of my experiment that showed a force acting on a hollow ring, and a strain gauges attached on the ring measured strain for the set force. I was wanting to know/find out as to why a ring is more effective than, eg. a square cutout, in measuring strain? I tried looking for information on Proving Rings, but not found any answer there. Main question is that is there any book/journal that highlights how the geometry affects the accuracy and/or effectiveness of strain measurement?