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Overflow is usually used to keep fluid continuously flowing to avoid the fluid from changing flow direction and subsequently inducing large stresses. To explore the mechanism of flow-induced stress evolution, a flow model was established in terms of compressible, non-isothermal, and viscoelastic flow. Based on the Leonov model and the mid-plane approach, a pseudo-Poisson type equation for pressure was derived to decouple the interdependence between velocity and pressure. To improve computational efficiency, a numerical approach involving double iterations was proposed to solve the flow problem. Two kinds of mold cavities, with and without overflow, were designed and manufactured. Molding experiments were conducted, and corresponding simulations based on the proposed model and algorithm were performed. The results show that the simulated contours of flow-induced stress are in good agreement with the photoelastic streaks. The use of overflow can significantly reduce flow-induced stresses. If the slot thickness is set to a proper value, the flow-induced stress can be reduced by more than 80%. On the other hand, a slot that is too thick does not have significant reducing effects. Therefore, using overflow to reduce flow-induced stresses during transparent part production is a promising approach if the material cost is worthy of the quality. Highlights * A double iteration method is proposed for viscoelastic flow problem. * Overflow can reduce the stress as much as 80% if the dimension is properly set. * The simulated stress streaks are in good agreement with photoelasticities. KEYWORDS finite element method, flow-induced stress, Leonov model, overflow, viscoelastic, 1 | INTRODUCTION Injection molding (IM) is the most efficient mass-production technology for manufacturing polymers in complex and detailed geometries with high precision. In view of these advantages, most transparent [...]

Polymerie materials are widely used in structural components and systems, and the accurate prediction of their complex time-dependent behavior is critical. Several constitutive models are available for different types of mechanical behaviors and loading conditions. However, selecting the model and the correct calibration of its parameters is often a challenge. This paper evaluates the applicability of the two-layer viscoplasticity (TLV) model to predict the viscoplastic behavior of polyvinylidene fluoride (PVDF) in a large range of strain rates and complex states of strain. The setting of parameters and model validation was made by performing experimentally and numerically uniaxial compression tests and relaxation tests. The model parameters were also analyzed in performing microindentation tests. The TLV model using the same set of parameters selected well predicted the PVDF behavior in a wide variety of compressive loading conditions. KEYWORDS elastoplastic-viscoelastic model, finite element analysis, instrumented indentation test, polyvinylidene fluoride, two-layer viscoplasticity model, 1 | INTRODUCTION Flexible pipelines are multilayered structures that transport fluids between wells and floating units in offshore oil fields. [1] They are composed of helical armoring layers and polymer [...]