THE PRACTICAL USE OF THE HOLE METHOD IN PHOTOELASTICITY

A small circular hole has already been used in plane elasto-static pho toelasticity to determine the stress tensor for any general loading si tuation. Originally the idea required the determination of the stress at four points at the free boundary of the hole, then it was found tha t more precision would be obtained if the measurements were taken at p oints located at a distance from the center of the hole equal to twice its radius. Later it was suggested that probably still better results would be obtained from points located at 1.4 times the radius. This p aper has three objectives: (1) to improve the precision of the measure ments by taking them at any point in the vicinity of the hole, which r equires that the expressions giving the principal stresses be presente d in a different form, as a function of the normalized variable distan ce from the center of the hole; (2) to show the consistent application of the method, using the values of the birefringence at various arbit rary radial locations, to plane elasto-static loading problems; and, ( 3) to present the application of this approach in a concise form so th at its application is practical.