INTEGRAL CONSTITUTIVE MODEL (K-BKZ) TO DESCRIBE VISCOELASTIC FLOW IN INJECTION-MOLDING

A novel theory which employs the K-BKZ viscoelastic integral constitut ive model was developed in this study for simulating the non-isotherma l injection molding filling process and the frozen stresses of a three -dimensional thin part. The simulation of viscoelastic model in such a problem has not yet been discussed in most previous works as a result of the complexity of this problem. A quasi-steady approximation conce pt was developed in the present investigation for solving the non-isot hermal filling process via K-BKZ viscoelastic integral constitutive mo del. Additionally, the numerical method of flow field was based on the control volume finite element method. The flow field of generalized N ewtonian fluid was used as the initial guess of flow kinematics. The q uasi-steady state approximation was introduced for each element to cal culate the flow kinematics and stress profile from the K-BKZ integral constitutive model. The finite difference method with streamline upwin d characteristic was adopted here for calculating the temperature fiel d of process. When the cavity is fully filled, the subsequent non-isot hermal stresses would relax after cessation of flow. Thereby, the froz en stresses (or frozen birefringence) could be obtained.