Papers by Author: Péter Barkóczy

Abstract: Residual stresses of production origin superimposed with the operational stresses influences the reliability of glass products. The most widely used procedures for their detection and qualification are optical methods that can not be utilized for testing of non-transparent glasses. A recently developed glass qualifying procedure based on scratch test with integrated image processing is applicable for evaluating the residual stresses in surface of both the transparent and non-transparent glasses. The reliability of the suggested test method is greatly dependent on the information content provided by the involved image analysis procedure. The current paper introduces the principle, and methodology of the test method, furthermore presents the latest results gained by applying an improved algorithm of the image processing.

Abstract: Residual stresses significantly influence the strength and lifetime of the glass products, therefore their qualification and quantification during production is basically important for evaluating their probable reliability in application. The current paper aims at introducing a novel procedure of the suggested automatic glass quality test based on instrumented scratch test completed with computer aided image analysis. A special emphasis is put on the problem of limited reproducibility and reliability of the image processing, arisen in the first stage of the research work. The latest results consisting in the development of a new algorithm, providing a more reliable evaluation of the test data will be described.

Abstract: The anisotropy of dendritic structure is characterized in this paper. The direction of move of liquid/solid interface influence the velocity of the melt flow. In the course of the experiments the liquid/solid interface was moved in three different directions: i) at right angles to the direction of gravity vector, ii) in the direction identical with it and iii) in the direction opposite to it. Our purpose was to investigate the shape of solidifying dendrites as a function of the angle included by the gravity vector and solidification [6]. The measurements were done in real images fixed by us. The following parameters were chosen for characterizeing the anisotropy of dendrites: intersection number of the test lines and dendrite interface (P), orientation factor (
), dendritic surface in volume (SV). The material was solidified by using an equipment developed by the authors. The solidification rate is a constant value: 0.001 mm/s and 0.003 mm/s, the composition of material used for modelling purposes is: SCN (succinonitrile) -2.5-3 mass% of acetone. 100 images were processed in each direction. It was necessary to rotate the images in order to count the number of intersections. A program developed by the authors was used for this purpose; the number of intersections was given by the program as a function of the angle of rotation, and the perimeter and area of the dendrites.

Abstract: The CA method provides an excellent possibility for a lifelike simulation of transformation processes. Using CA method the processes can be displayed on the screen of the computer as a film. CA method is widely used to simulate the transformations controlled by short-range diffusion such as recrystallisation and grain growth. At the simulation of transformations based on long-range diffusion a well-known problem is that the results of simulation depend strongly on the selected nucleus geometry and the neighbourhood of cells. In this paper the influence of neighbourhood will be analysed in the case of simulated precipitation processes. On the one hand, it is verified that an anisotropic (dendritic) structure is formed if there is no strict restriction for the computational algorithm. On the other hand, it is demonstrated that an isotropic phase growth can be obtained by using a special simulation technique based on the joint application of finite difference (FD) and of CA methods.