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A tailored graphical user interface (GUI) for finite element analysis, fully integrated into Microsoft Windows 3.1, has been developed. The current application is the simulation of flat sheet extrusion of thermoplastics, but many of the features would be common to a wide range of finite element analyses. Microsoft’s C/C++ Professional Development System 7.0, including the Software Development Kit 3.1 (SDK), has been used as the programming tool for the GUI. The interface is based on the Common User Access Advanced Interface Design Guide, which is part of the IBM Systems Application Architecture Library, and The Windows Interface: An Application Design Guide, which is part of the SDK. A memory handling technique is proposed to break the imposed 64 KB data segmentation. Connected finite element calculation routines are written in Fortran and compiled by the Salford FTN77/x86 32‐bit compiler. The protected mode interface of the Fortran compiler allows direct access by the GUI, and allows the computation to run as a 32‐bit background application, without memory limitations, in the multitasking environment. Finite element routines are supported by pre‐ and post‐processors comprising mesh generation, post‐processing for derived results, and graphical displays. A convenient contouring algorithm is proposed to generate contoured plots of nodal quantities in the form of iso‐lines or iso‐fields.

The main purpose of this paper is to present and compare two different models for bubble growth and foam formation and to conduct a thorough assessment in terms of their numerical implementation and prediction accuracy.

The two models are assessed and validated against experimental measurements. The first model is known as a single bubble growth model and treats the foaming process as a single bubble growing in a large pool with enough gas available for growth, while the second model (cell model) takes into account the finiteness of gas supply availability as well as the effects of surrounding bubbles. The models are based on the application of the conservation of continuity and momentum principles and on constitutive equations to represent the viscosity of the melt. The models are numerically implemented using a finite difference scheme and their predictions are compared against experimental measurements.

The results demonstrate that the single bubble model predicts an infinite bubble growth with time due to the assumption of unlimited supply of the blowing agent. Meanwhile the cell model gives an equilibrium bubble size because it accounts for gas depletion. From this work, it was concluded that the cell model is the best model that adequately describes experimental data.

The problem of bubble growth and foam formation is of great importance in the process industry as it plays a key role in diverse technological fields such as the production of foamed plastics.

The findings here are important for the appropriate modeling of bubble growth and foam formation and for scheduling and optimizing the process. A simple model will suffice for the early stage of the process while a cell model is more appropriate for the entire duration of the process.

This chapter theorizes a proposal for applying the study of Brexit as a pedagogical strategy in an European Studies (ES) bachelor program, as a means to activate theoretical knowledge for different disciplinary and thematic fields of study about the European Union. The proposal uses the problem-based learning (PBL) approach as a pedagogical methodology and the bachelor of ES at the Faculty of Arts and Humanities at the University of Coimbra as a case study to rehearse teaching innovation. It is based on a theoretical part, conciliating PBL as a pedagogical tool in social sciences and humanities with the exceptionalism of Brexit within the European integration theories and the study of European policies to activate and question prior scientific knowledge, and on a survey to bachelor’s students and alumni on the pertinence of PBL and of Brexit as an empirical element for scientific knowledge in ES. As a result, specific proposals to use Brexit in PBL experiences in different disciplinary areas of ES are made, paving the way for a range of teaching and learning opportunities and challenges released by Brexit to make progress in the ES pedagogical framework.

This study aims to develop mathematical models for the determination of the effects of heating or cooling on neck growth in Selective Laser Sintering (SLS) and Fused Filament Fabrication (FFF). Two particle shapes are studied: spherical and cylindrical.

The time required for the coalescence (sintering) process is determined by balancing the work of surface tension forces and viscous dissipation. Heating and cooling effects are studied by incorporating temperature dependence of viscosity in an exponential form. Heating by a laser, convective and/or radiative heat transfer is assumed. It is also assumed that there are no temperature gradients within the coalescing molten polymers (lumped parameter heat transfer analysis).

The models predict faster sintering with heating and slower with cooling, as expected because of the effect of temperature on viscosity. For the isothermal case of pairs of cylinders, the present model predicts significantly longer time for completion of sintering than a previously developed and frequently cited model by Hopper.

An isothermal sintering model for two spheres was reworked for two long cylinders, and for the first time it has been compared to other models available in the literature. The mathematical models are capable of predicting neck growth under non-isothermal conditions for both spheres and cylinders. They are useful in assessment of bonding in selective laser sintering and fused deposition fabrication.

This paper aims to present a survey concerning the accuracy of thermoplastic polymeric parts fabricated by additive manufacturing (AM). Based on the scientific literature, the aim is to provide an updated map of trends and gaps in this relevant research field. Several technologies and investigation methods are examined, thus giving an overview and analysis of the growing body of research.

Permutations of keywords, which concern materials, technologies and the accuracy of thermoplastic polymeric parts fabricated by AM, are used for a systematic search in peer-review databases. The selected articles are screened and ranked to identify those that are more relevant. A bibliometric analysis is performed based on investigated materials and applied technologies of published papers. Finally, each paper is categorised and discussed by considering the implemented research methods.

The interest in the accuracy of additively manufactured thermoplastics is increasing. The principal sources of inaccuracies are those shrinkages occurring during part solidification. The analysis of the research methods shows a predominance of empirical approaches. Due to the experimental context, those achievements have consequently limited applicability. Analytical and numerical models, which generally require huge computational costs when applied to complex products, are also numerous and are investigated in detail. Several articles deal with artificial intelligence tools and are gaining more and more attention.

The cross-technology survey on the accuracy issue highlights the common critical aspects of thermoplastics transformed by AM. An updated map of the recent research literature is achieved. The analysis shows the advantages and limitations of different research methods in this field, providing an overview of research trends and gaps.

Fused Filament Fabrication (FFF) is an extrusion-based manufacturing process using fused thermoplastics. Despite its low cost, the FFF is not extensively used in high-value industrial sectors mainly due to parts' anisotropy (related to the deposition strategy) and residual stresses (caused by successive heating cycles). Thus, this study aims to investigate the process improvement and the optimization of the printed parts.

In this work, a meshless technique – the Radial Point Interpolation Method (RPIM) – is used to numerically simulate the viscoplastic extrusion process – the initial phase of the FFF. Unlike the FEM, in meshless methods, there is no pre-established relationship between the nodes so the nodal mesh will not face mesh distortions and the discretization can easily be modified by adding or removing nodes from the initial nodal mesh. The accuracy of the obtained results highlights the importance of using meshless techniques in this field.

Meshless methods show particular relevance in this topic since the nodes can be distributed to match the layer-by-layer growing condition of the printing process.

Using the flow formulation combined with the heat transfer formulation presented here for the first time within an in-house RPIM code, an algorithm is proposed, implemented and validated for benchmark examples.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming and powder metallurgy are briefly discussed. The range of applications of finite elements on the subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for the last five years, and more than 1100 references are listed.

The design of vacuum calibrators for the cooling of complex PVC profiles is central to the production of high quality extrudates. One important parameter governing cooling efficiency is the heat transfer coefficient at the interface between the stainless steel calibrator and the PVC extrudate, whose value is often taken as constant regardless of the extrusion velocity and the applied pressure vacuum. In this paper, a method is proposed to evaluate the variation of the heat transfer coefficient over the entire calibrator length. The idea is to use temperature measurements together with heat transfer simulation to derive a heat transfer correlation that can be used in practical design cases.

In this article we report on progress in the development of software tools for fluid flow prediction in the polymer processing industry. This involves state‐of‐the‐art numerical techniques and the study of a number of non‐trivial model flow problems, in an effort to investigate realistic transient problems relevant to industrial processes. Here we study particularly the effects of variations in non‐Newtonian and heat transfer properties of the flowing materials in the flows, both throughout the transient development period and at steady‐state.

This paper aims to investigate the effects of epoxy resin on the rheological and mechanical properties and water absorption rate of wood flour/high-density polyethylene (HDPE) composites (wood-plastic composite [WPC]).

The reactive mixing of various epoxy resins with 60 Wt.% wood flour and HDPE was carried out in a twin-screw extruder with a special screw element arrangement. Polyethylene-grafted maleic anhydride (MAPE) was used as a coupling agent to improve the interfacial interaction between wood flour, epoxy resin and HDPE.

The tensile, flexural and impact properties of the composites increased initially and then decreased with the increasing content of epoxy resin. The complex viscosity decreased with increasing epoxy resin content, but a trend reversal was observed at 8 Wt.% epoxy resin. The epoxy resin-modified wood-HDPE composites chemically coupled by MAPE showed minimal water absorption.

The cured epoxy resins impart high-aspect-ratio and plate-like polymeric fillers, affect the rheological behavior of the WPC and can also be oriented in a flow direction. Epoxy resin has good interaction with the cellulose structure of wood flour because of the polar functional groups within the cellulose.

This method provided a simple and practical solution to improve the performance of WPC.

The WPC modified by epoxy resin in this study had high performance in rheological and mechanical properties, and thus can be widely used for domestic, packaging and automotive applications.