This work is concerned with the analytical characterization of the electromechanical nonlinear effects on the fields surrounding the tip of an interface crack between ferroelectric-plastic bimaterials. A strip electric saturation and mechanical yielding model is developed for a mode III interfacial crack with electrical polarization reaching a saturation limit and shear stress reaching a yield stress along a line segment in front of the crack. The electrical saturation zone and mechanical yielding zone may have dierent length scales depending on loading conditions. This model may be considered as a generalization of the classical Dugdale model for plastic yielding near cracks in homogenous materials. The results reveal insight into the structure of stress and electric displacement fields for different load conditions. The energy release rate and COD dIII are also obtained, which indicates the possibility of fracture criterion based on the COD dIII.