抄録
The mechanical and optical constitutive equations for the Tresca type plastic materials are defined, which are subjected to the Tresca yield condition. The stress in simple shear is analyzed and the dimensionless stress components are calculated for three values of the dimensionless material constant. The shear stress shows the hypo-elastic yield and the maximum difference between the principal stresses increases monotonically against the angle of shear and approaches to a yield value. The birefringence also shows the Tresca yield, which is called the optical yield, while the extinction angle does not show any yield phenomenon.
