
Sensors in Engineering and Science 63
2.7 Photoelastic
Methods using transmitted light can be used to determine stress and strain
fields. The photoelastic method determines stress fields in certain trans-
parent materials, such as plastics or materials coated with a photoelastic
layer. The moir´e method determines the strain field in a material and re-
quires a grating material to be fixed to the material’s surface. Both methods
rely upon developing an interference pattern consisting of bright and dark
regions.
The photoelastic method is based upon the principle that certain
materials will polarize light when they are strained. More specifically, if light ...