<title>Cases of weak and strong birefringence in integrated photoelasticity</title>

Integrated Photoelasticity for Axisymmetric Thermal Stress Measurement Using the Stress Function

“…Equations (1) and (2) are valid if either birefringence is weak or rotation of the principal stress axes on light rays is small [4][5][6]. Let us use the first and third equilibrium equations of the theory thermoelasticity…”

“…In linear approximation the principal formulas of integrated photoelasticity take the form [4][5][6] V * 1 x z = 1 C cos 2 (57)…”

“…In the case of weak birefringence [3,4], stress components z and rz can be determined directly from the measurement data [3,5]. For the determination of the stress components r and the equilibrium and compatibility equations are usually used [2,3].…”

Photoelastic tomography for residual stress measurement in glass

“…In a different way the formulas (16) and (17) were derived in Ref. 18, where the domain of their applicability was investigated. Linear approximation is valid if birefringence is weak (optical retardation is less than about 1/3 of the wavelength) or the rotation of the principal stress axes is small.…”

<title>Determination of 3D stress by optical sensor field tomography</title>

“…Ifthe wave is travelling in z-direction through an optically birefringent material with the spatially varying refractive tensor nxx@t) () n@) () -n@) n() n() , (2) n@) n() n@) the electrical field vector changes according to the ordinary differential equation 3x) _ k n () ) , (3) where k is the wave number and flxx xy ] (4) nxy nyy is the tensor of the transverse refractive indices, omitting the spatial dependence. (1) one has the possibility to use an optical method to examine the distribution of the stress tensor in the transparent model.…”