stress. Or more clearly, stress is directly proportional to strain. These solids obey Hook's law of elasticity, known as the Hookian solid. Viscoelastic behavior. Some materials obey the properties of solids and liquids up to a limited range of deformation. This superposition of elastic and viscous flow behavior is called viscoelastic behavior. And this is the topic of interest in this project. Rheological equation of state: is the relationship between the stress acting at a point and the deformation that occurs as a result of their action. The relationship between stress and strain for a particular type of viscoelastic material is called the rheological equation of state. RHEOLOGICAL MODELS: There are many models that are purely practical and selective for some materials. Through which we can know the relationship between viscosity, shear stress and deformation relationship. Some of the important models are described below. Cross Model: The cross model is given by the Cross equation and can be written