1,721,064 research outputs found
Micro injection molding of LCP-modified PA66
No full textInjection molded micro parts require accurate replication of micro-scale features. This replication is governed by complex mechanisms and its quality depend on the plastic material properties, the geometry of the features and the process conditions The objective of this paper is to improve the replication of the micro-scale features by decreasing the polymer viscosity. The effects of melt viscosity and molding conditions on replication of microscopic features in injection molded parts were examined for a PA66 blended with a LCP additive. The replication was measured at different contents of LCP and at different process conditions
Three dimensional viscoelastic simulation of thin-wall injection moulding with micro-features
No full textDedicated simulations software fail to correctly describe me melt flow in microstructures, mainly because phenomena such as tendency of polymers to slip in microchannels, micro scale surface effects and micro scale rheological behaviour are not considered. It is conjectured that wall slip would more easily occur in micro channels based on die viscoelastic behaviour of the polymer. Numerical simulations on a micro component are carried out according to the viscoelastic models implemented in Ansys Polyflow® and compared to the experimental results. Viscoelastic data are obtained from a careful material characterization conducted on a rotational and a capillary rheometers
Investigation in the use of LCP additives for microstructured surfaces replication
No full textInjection moulded micro parts and microstructured surfaces require accurate replication of micro-scale features, which depends on polymer properties, features geometry and process parameters. The objective of this paper is to improve the replication quality of moulded micro-scale features by blending a PA66 with a LCP additive. Both experimental tests and numerical modelling were used to evaluate the single and combined effects of the polymer rheological properties, moulding conditions and features orientation on the replication at different contents of LCP. Tensile tests were also carried out to assess how LCP affects the PA66 mechanical properties
Economical break-even analysis between steel and aluminium moulds by early cost estimation
No full textThis paper provides a systematic and quantitative method for the analysis of the economical break-even between steel and aluminium moulds used in the injection moulding process. The proposed approach takes into account both mould manufacturing (material purchase and machining) and injection moulding costs (cycle time). Thermoplastic material cost is not considered since it does not change in a comparative analysis. The total costs are estimated against the part life volume and the break-even point between steel and aluminium technological solution is determined. The proposed method is validated through an industrial case study
Calibrating the numerical simulation of the injection moulding process for liquid silicone rubber
No full textIn this work, a new Computer Aided Engineering method was developed to predict optimal design and process conditions for stretch blow moulded bottles, minimizing the cost associated with the design of a new container. The proposed approach evaluates final product characteristics by process numerical simulations in a user friendly environment. The implemented algorithm seeks for the optimal conditions in terms of preform geometry and operating parameters, subjected to process and design constraints. Special attention was devoted to material characterization, obtained by simple and inexpensive instruments, and to the material model implementation, in order to improve results accuracy. For the process simulations commercial general purpose numerical codes were used. With reference to an industrial case study, the predicted optimization results were compared to the experimental outcomes to assess the validity and the robustness of the proposed approach
On the performance of a viscoelastic constitutive model for micro injection moulding simulations
No full textThe numerical simulation of the injection moulding process involving microstructures presents several challenges, mainly due to the surface effects that dominate the flow behaviour at the microscale. In this paper a new approach, which employs weld lines as flow markers, is used to evaluate whether the numerical codes that are normally used to simulate the conventional injection moulding process, are suitable to characterize the melt flow patterns in the filling of micro features. The Cross-WLF viscous model and the Giesekus viscoelastic model were evaluated using 3D models of a micro part implemented in two different numerical codes. A micro cavity was designed in order to compare the results of numerical simulations and experiments. While the viscous simulations were found to be inappropriate for multi-scale structures, the accuracy of micro filling predictions was significantly improved by implementing a viscoelastic material model
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
