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Shear heating parameter of rubber compounds useful for process control in injection molding machine
No full textControl of the injection molding process of rubber is made complex by the influence of many parameters. Shear heating, heat generation due to viscous dissipation, is a phenomenon largely exploited in rubber to lower compound viscosity, particularly in the extrusion phase, but it is impossible to predict it from laboratory tests. With the aim of providing useful tools for process control, a parameter for on-line monitoring of shear heating phenomenon is proposed. This parameter is based on direct measurement of rubber surface temperature by infrared thermal camera at the nozzle outlet of the injection molding machine extruder. The measured rubber temperature is a process indicator to give the thermal history of the rubber injection and process safety. Measured temperature increase is then converted into a parameter having dimensions of viscosity, the shear heating parameter, gSH. Four different rubber compounds are investigated. The gSH results are compared to minimum torque (ML) from routine rheometric laboratory measurement. The calculated gSH values increase with increasing ML values. The ML value is a rough indication of the rubber compound viscosity, where its relevant variations affect the rubber processability. Meanwhile gSH is more sensitive to small processability variations and more accurate because it takes into account the thermal history during the injection stage. The found relationship provides deeper insights into the behavior of rubber, compared to laboratory tests, and how it can be used in the industrial practice to improve the process control by monitoring the shear heating effect during the injection stage
Monitoring of shear heating effects during injection molding of rubber to improve the process control
Get PDFThis work aims to get new insights into the “process monitoring tool” proposed by the authors for the online monitoring of the shear heating phenomenon during injection molding of technical rubber parts. The online monitoring is based on direct measurement of the surface rubber temperature (shear heating temperature, TSH) by an infrared thermal camera of the rubber as it leaves the extruder barrel of the injection molding machine. The measured rubber temperature is a process indicator giving the thermal history of the rubber compound injection and process safety. Therefore, this fast process control is applied to industrial applications to investigate the processing behavior of ethylene acrylate (AEM) rubber compounds. In particular, the relationships between TSH vs injection pressure, vs injection speed, vs screw speed rotation and vs screw length over diameter ratio (L/D ratio) and vs AEM rubber compound properties variation due to exceeding the shelf life are investigated. The results show that TSH is manly influenced by the screw L/D ratio, followed by injection pressure and screw speed rotation (especially if are set to higher levels), whereas the injection speed is the least effective parameter to reduce TSH. Furthermore, a previously found robust correlation between the shear heating parameter (ηSH) and the minimum torque measured in rheometric laboratory tests (ML) is used to show the noteworthy deviation from the proportional trend when the AEM rubber compound exceeded it shelf life. Therefore, the coefficient of determination of log ηSH vs ML curves provides a good indication of process stability, while it is running
Applications of shear heating parameter for injection molding process optimization of AEM rubber compounds
Get PDFShear heating phenomena during injection molding of rubber compounds greatly affect product quality but are difficult to control and replicate with laboratory tests. In this work, a very fast online process control of industrial injection molding is proposed, based on the measurement of surface temperature by infrared thermal camera of the rubber as it leaves the extruder barrel. Moreover, a new technological parameter (shear heating parameter, ηSH) is calculated from the measured temperature. A robust correlation between ηSH and viscosity from rheometric laboratory measurements was achieved for different rubber compounds. This represents an operating roadmap to support the process engineer in the improvement of process control. To show the potential of this tool, it was successfully used to optimize the injection molding of industrial production of AEM rubber compound affected by scorching and thermal degradation issues. ηSH was found to be suitable for industrial practice and able to provide accurate information about thermal history and process safety
A novel and sustainable rubber composite prepared from electric arc furnace slag as carbon black replacement
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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