Non Isothermal Tube Model Characterization for High Speed Thermoforming Stretch
Accurate non isothermal tube characterization reduces thermoforming wall variance to under six percent at hundred hertz stretch rates.
Rolie Poly Constitutive Equation
Meaning
Mathematical description of linear polymer melts under rapid shear and elongation provides the basis for simulating extrusion and molding processes. Utilizing the rolie poly constitutive equation allows engineers to model the flow behavior of linear polymers like high-density polyethylene or polystyrene. This simplified model captures both the stretch and orientation relaxation of polymer chains during rapid deformation.
Relaxation Dynamics
Linear polymers stretch and orient themselves under flow forces, then relax through process-dependent mechanism routes. The rolie poly constitutive equation simulates these relaxation dynamics by incorporating terms for convective constraint release and chain stretch. This mathematical framework enables the prediction of shear-thinning and strain-hardening behaviors, which are essential for understanding how the polymer melt will fill a complex die cavity.
Mold Design
High extrusion speeds can lead to defects such as melt fracture or sharkskin if the shear rates at the die wall become too high. Designers use the rolie poly constitutive equation in simulation software to identify high-stress zones within the flow channel before manufacturing the die. This predictive capability allows for the refinement of flow channel geometry to reduce shear stress and prevent the formation of surface blemishes.
Process Simulation
Predicting how a linear resin will behave in high-speed processing requires models that remain stable under extreme flow conditions. The simplicity of the rolie poly constitutive equation makes it computationally efficient, allowing for its integration into full three-dimensional simulation codes. This efficiency helps processors run complete virtual molding trials, allowing them to refine temperature profiles and line speeds to achieve uniform part properties across the production batch.
Utilizing this model reduces the dependence on physical trial runs, saving both energy and polymer materials on the factory floor during product development.