Abstract: A Photoelastic method for the measurement of the difference between principal stresses is applied to the measurement of a two dimensional ultrasonic stress. The stress of an ultrasonic plane progressive wave or cylindrical progressive wave at any point in a transparent solid can be determined.
The method of the measu’rement and its principle is presented, including the derivation of the relation between the principal stresses difference and the principal stresses for plane or cylindrical progressive wave. A practical example of measurement is described, its results being compared with those of an electrical method.