Advanced Materials Research Vols. 39-40

Abstract: Applications of vision systems for control and monitoring are becoming more widespread. However, there are still specific problems in the glass industry, especially transparency of glass (many times colourless) that requires the use of special illuminations, adapters for lenses, filters, software filters, analyses of images, etc. An important problem is the choice of an optimal analysis for obtained images that should correspond with the character of obtained data. Our research is developing the use of cameras (an area scan cameras, a line scan cameras, and an intelligent cameras) for quality monitoring of glass production with connection to a PC or compact vision systems, software solutions with appropriate image analyses (using standard and new algorithms) and to solve of real problems for industry applications. The first stage of the research is: using a digital camera, an area scan camera and a line scan camera for glass melt and glass products monitoring to solve specific problems with lighting and to test some standard and non-standard analysis such as fractal geometry for the evaluation of productions and products. This article briefly shows basic information about our results and possibilities of application in the glass industry.

Abstract: The overflow fusion process was an important method for the manufacture of glass sheet that is currently used for the production of TFT/LCD display devices. The design of forming apparatus was critical for very high surface quality of glass to allow the successful application of semiconductor type material. However, there is only a little of researches had been presented in the literatures, because of difficulties and expansions in experiments. In this study, a numerical model for simulation of molten glass flow through the isopipe during overflow fusion process was carried out. The effect of temperature of forming apparatus and of molten glass on the flow patterns during overflow fusion process was investigated. It was found that the stability and flatness of sheet glass was influenced strongly by the temperature of forming apparatus and molten glass. A precise control of overflow temperature and temperature distribution of isopipe was needed for maintaining a stable flow and uniform thickness.

Abstract: Improving technology and materials in glass production for the 21st century supposes implementation of high-level innovations. These innovations are necessary not to be only developed, produced and set up but also their qualities and perspectives need to be evaluated so that the ratio of their application is increased. The application ratio of developed innovations lies among 1-3% at present. All stages of glass processing like melting, forming or cold working have mostly limitations of its own further development which are necessary to be detected so that further possibility of innovation can be predicted. At present it is not sufficient to have only theoretic and expert knowledge of the field and IT applications but it is necessary to know the methods of creative thinking for achievement and application of required innovation. Understanding of the system of creative thinking makes possible to better and faster adapt to real life practice which changes very fast. TRIZ (Theory of Inventive Problem Solving) is a powerful method of creative technical thinking which originated by studying patents and by generalization of successful process solving. The method TRIZ makes possible to find a correct formulation of a task out of unclearly described situation as well as to solve the newly re-formulated task by using unique strong instruments of the TRIZ method [1]. Application of the TRIZ method is supported by a unique SW designed for collection of information, analyses, synthesis of solutions and verification of the found solutions. Practical examples of using the TRIZ method will be presented in the contribution on chosen glass technologies.

Abstract: Consistent model including structural relaxation is necessary for correct glass stress calculation in numerical computations of glass forming processes. Calculation of glass relaxation phenomena is often done by combining independent empirical formula on stress relaxation (for a simple temperature regime) and independent model of time-temperature dependence on Tool fictive temperature, Tf. Another approach was developed and verified here. Tool-Narayanaswamy and Moynihan/Mazurin relaxation model was adopted. Relaxation was obtained not from empirical model, but from calculated time-temperature dependence of Tool fictive temperature (Tf), dynamic viscosity, heat capacity and coefficient of thermal expansion. Heat conduction in a glass probe of known temperature history, structural relaxation and stress calculation were used in one computation scheme using Matlab. The stress of glass probe was measured using polarized light (Senarmont method). Rather high stress computation accuracy was obtained in comparison to stress experimental results. The applied model approach is being to be extended for application in commercial finite element codes for modeling of glass forming processes.

Abstract: In the contribution problem of dynamic loading of glass moulds is analysed. Possibilities of FEM for evaluation of tensile states initiated with temperature variations are shown on a particular case. Critical areas where cracks nucleation as a result of thermal fatigue can be expected are evaluated. Results are used for relative comparison of service life of mould with classical design and mould with optimised design (with control cooling).

Abstract: Zinc selenite, calcium selenite and metallic selenium have been consecutively introduced as decolorizing agents in a flint glass production. The selenium concentration in the glass has been measured by wet-chemical analysis, optically by the evaluation of the cielab a-value and electrochemically by means of a voltammetric sensor. All measuring techniques showed the highest selenium retention for calcium selenite followed by zinc selenite and the least retention using metallic selenium. The best reproducibility is achieved using zinc selenite while both calcium selenite and metallic selenium provide only poor reproducibility.

Abstract: Recent trends in architecture are characterized with wide applications of laminated glass plates in facing systems of high-rise buildings, where the plates are oriented in both vertical and horizontal planes. This paper deals with mathematical description of optimization problem for location of finite number of rigid supports horizontally placed on jumbo flat glass plate with free edges. Associated state problem corresponding to Kirchhoff’s hypothesis of plate theory is solved. Further the optimization problem for finding location of the finite number of rigid supports, with respect to the condition for minimal deflection of the plate in the sense of 1 C -norm, is solved. Theoretical results are used in numerical simulation by the finite element method (FEM). It allows us to reduce the computation time for solution of real projects. Further application of such results is for example in the area of automatic handling in the flat glass production in the case of engineering design for location of vacuum gripping heads components of handling devices.

Abstract: Flat glass disks are thermally tempered by air-cooling with two air jets at the centre of their surfaces. Numerical modelling and photoelasticity measurements are proposed to analyze the distribution of the residual stresses through the glass thickness at the centre of the tempered disks. For the modelling, glass properties dependent of the temperature are used for the conductive heat transfer. Radiation is modelled by an improved approximation method. By taking both structural and stress relaxations into account, the transient and residual stresses are computed along the disk thickness. For experimentation, a complete procedure is proposed to access to the stress state in the centre of the disks using a scattered light polariscope. The average distribution of the residual stresses is deduced from stress profile measurements taking four radial orientations at the disk centre into consideration. Comparison between numerical and experimental values is finally discussed for the residual surface and half-thickness stresses at the disk centre.

Abstract: Portable energy-dispersive micro X-ray fluorescence spectrometry (-EDXRF) is a useful device for non-destructive chemical analysis of different materials. Despite its evident potential in the fields of glass analysis, only few archaeometric studies have been performed yet. In this work preliminary results on the analysis of different types of industrial glass by -XRF are presented in view to apply this method in industrial applications (monitoring of glass cullet, production quality control, classification of end products, etc.). The experimental results show a reliable qualitative recognition of detectable elements in the glass. A good correlation line intensity/concentration was verified for several important elements. Furthermore very low limits of detection were estimated for critical elements such as Fe, Cr and Pb.

Abstract: The goal of the work was to determine and characterize the inclusions of nickel sulphide in tempered glass. During the tempering process where the glass is heated the nickel sulphide stones are completed transformed to the high temperature modification which is unstable when the temperature decreased. The glass samples, which include the NiS stones, were investigated by microscopic method (SEM) and characterized by EDAX analysis. The glass samples were analysis by elastooptic studies but it did not prove occurrence of stresses. Obtained results will help to solve the problem with forming nickel sulphide inclusions.