Abstract
Most of the methods of contemporary experimental mechanics permit measurement of the stresses and strains only on the surface of the test object. Photoelasticity gives the possibility to investigate non-destructively also 3D stress fields. However, in the general case photoelastic tomography is very complicated due to complicated optical phenomena which occur when polarized light passes a 3D inhomogeneous and birefringent medium. In linear approximation, from the equations of integrated photoelasticity two integral equations can be derived which relate photoelastic measurement data with integrals of certain components of the stress tensor. Using these equations, Radon transform of a component of the stress tensor can be expressed through the tomographic photoelastic measurement data. That opens the possibility to determine normal stress distribution in an arbitrary section of a 3D test object using Radon inversion. Linear approximation is valid when either birefringence is weak or rotation of the principal stress axes is small. The method is realized with a computer-controlled photoelastic polariscope supplied with a rotating device. Application of the method is illustrated by several examples of residual stress measurement in glass articles.
