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Kek T.,University of Ljubljana | Kusic D.,Slovenian Tool and Die Development Center
Emerging Technologies in Non-Destructive Testing VI - Proceedings of the 6th International Conference on Emerging Technologies in Nondestructive Testing, ETNDT 2016 | Year: 2016

This paper presents the experimental results regarding acoustic emission signals measured during the injection moulding of those standard test specimens commonly used for examining the shrinkage behaviour of various thermoplastic materials. In daily industrial production of different plastic products we often have to deal with various errors that practically occur on the mold primarily as a result of tool wear and tear, improper storage and improper settings on the injection molding machine. In the testing phase of plastic materials we use many times different inserts that are made from standard tool steels, such as OCR12VM. In case of tool steel inserts after some years of usage a few micro-cracks can occur in the early stage, which can later quickly spread according to the applied loading. With the help of different non-destructive testing methods we know that we can most certainly detect possible formation of cracks on the tool steel inserts. The acoustic emission was measured on an injection mould with the visible sign of a crack on the cavity’s surface, using two contact PZT sensors under normal and increased injection pressure loads. In this paper, we focused exclusively on the acoustic emission signal acquisition by using two resonant 150 kHz piezoelectric AE sensors on such tool steel inserts that are already affected by macro-cracks. On such tool steel insert the obtained acoustic emission results were compared with those obtained from a brand new tool steel insert. The final obtained acoustic emission results on the crack defected tool steel insert revealed as expected that the energy and intensity of the captured AE signals is higher compared with the ones that were captured on the brand new engraving insert under same processing conditions. © 2016 Taylor & Francis Group, London. Source


Kek T.,University of Ljubljana | Kusic D.,Slovenian Tool and Die Development Center | Grum J.,University of Ljubljana
Research in Nondestructive Evaluation | Year: 2016

ABSTRACT: Ten adult readers, advanced in their control of two languages, Korean and English, were recruited for a study of academic literacy practices to examine the various linguistic repertoires on which they drew. Analysis of their language use revealed many instances of translanguaging, that is, a flexible reliance on two languages to serve one’s immediate needs. All participants engaged in various cognitive reading strategies associated with translanguaging. These translanguaging practices in academic literacy were interpreted through the lens of Hornberger’s (2013) bilingual continua model, providing a perspective on the complex interplay of bilingual content, context, media, and development. © 2016 American Society for Nondestructive Testing. Source


Kek T.,University of Ljubljana | Kusic D.,Slovenian Tool and Die Development Center | Grum J.,University of Ljubljana
Applied Sciences (Switzerland) | Year: 2016

This paper presents measurements of acoustic emission (AE) signals during the injection molding of polypropylene with new and damaged mold. The damaged injection mold has cracks induced by laser surface heat treatment. Standard test specimens were injection molded, commonly used for examining the shrinkage behavior of various thermoplastic materials. The measured AE burst signals during injection molding cycle are presented. For injection molding tool integrity prediction, different AE burst signals' descriptors are defined. To lower computational complexity and increase performance, the feature selection method was implemented to define a feature subset in an appropriate multidimensional space to characterize the integrity of the injection molding tool and the injection molding process steps. The feature subset was used for neural network pattern recognition of AE signals during the full time of the injection molding cycle. The results confirm that acoustic emission measurement during injection molding of polymer materials is a promising technique for characterizing the integrity of molds with respect to damage, even with resonant sensors. © 2016 by the authors. Source


Jeselnik M.,Slovenian National Institute of Chemistry | Jeselnik M.,Slovenian Tool and Die Development Center | Zagar E.,Slovenian National Institute of Chemistry
Cellulose | Year: 2014

A glycosylated 2,2-bis(methylol)propionic acid (bis-MPA) derivative as a versatile glycodendritic building block was synthesized by direct O-glycosylation of benzyl protected bis-MPA with d-glucose pentaacetate. After removal of the benzyl protection group by hydrogenation, the obtained bis-O-glycosylated bis-MPA unit with free carboxyl group was applied for modification of trityl protected chitosan by amidation. The removal of the 6-O-trityl protection group on chitosan backbone under acidic conditions yields acetyl protected glycosylated chitosan that forms gel in water. The acetyl protection group of d-glucose was removed under alkaline conditions to form glycosylated chitosan which is water-soluble at physiological conditions and, thus, it is suitable for further investigation as a potential carrier in drug delivery systems. © 2014, Springer Science+Business Media Dordrecht. Source


Gantar G.,ENVITA D.o.o. | Glojek A.,Slovenian Tool and Die Development Center | Mori M.,University of Ljubljana | Sekavcnik M.,University of Ljubljana
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2013

The selection of most appropriate design and technological solutions to produce certain mould should capture technical performance, economical issues as well as environmental impacts occurred during the mould life cycle. In the paper an approach is presented to support the selection of alternative mould design solutions in the early design stage. It includes the use of Life Cycle Assessment methodology, Life Cycle Cost methodology and is supported by numerical simulations. The approach is applied to a case study where three mould designs for production of the same plastic product were compared. Finally, general conclusions regarding the resource efficient injection moulding processes are presented. ©2013 Journal of Mechanical Engineering. All rights reserved. Source

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