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2.
A model of surface roughness constitution in the metal cutting process applying tools with defined stereometry
Stanisĺaw Adamczak, Edward Miko, Franc Čuš, 2009, original scientific article

Abstract: The process of surface roughness formation is complex and dependent on numerous factors. The analysis of the latest reports on the subject shows that mathematical relationships used for determining surface irregularities after turning and milling are not complete or accurate enough and, therefore, need to be corrected. A new generalized mathematical model of roughness formation was developed for surfaces shaped with round-nose tools. The model provides us with a quantitative analysis of the effects of the tool representation, undeformed chip thickness, tool vibrations in relation to the workpiece, tool runout (for multicutter tools) and, indirectly, also tool wear. This model can be used to prepare separate models for most of the typical machining operations. Surface roughness is represented here by two parameters Ra and Rt. Simulations carried out for this model helped to develop nomograms which can be used for predicting and controlling the roughness Ra of surfaces sculptured by face milling.
Keywords: metal cutting, surface roughness, finishing, face milling
Published: 31.05.2012; Views: 1083; Downloads: 9
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3.
Characterization of reducible hexagons and fast decomposition of elementary benzenoid graphs
Andrej Taranenko, Aleksander Vesel, 2008, original scientific article

Abstract: A benzenoid graph is a finite connected plane graph with no cut vertices in which every interior region is bounded by a regular hexagon of a side length one. A benzenoid graph G is elementary if every edge belongs to a 1-factor of G. A hexagon h of an elementary benzenoid graph is reducible, if the removal of boundary edges and vertices of h results in an elementary benzenoid graph. We characterize the reducible hexagons of an elementary benzenoid graph. The characterization is the basis for an algorithm which finds the sequence of reducible hexagons that decompose a graph of this class in ▫$O(n^2)$▫ time. Moreover, we present an algorithm which decomposes an elementary benzenoid graph with at most one pericondensed component in linear time.
Keywords: mathematics, graph theory, benzenoid graphs, 1-factor, hexagons, reducible hexagons, reducible face decomposition
Published: 07.06.2012; Views: 996; Downloads: 32
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4.
1-factors and characterization of reducible faces of plane elementary bipartite graphs
Andrej Taranenko, Aleksander Vesel, 2012, original scientific article

Abstract: As a general case of molecular graphs of benzenoid hydrocarbons, we study plane bipartite graphs with Kekulé structures (1-factors). A bipartite graph ▫$G$▫ is called elementary if ▫$G$▫ is connected and every edge belongs to a 1-factor of ▫$G$▫. Some properties of the minimal and the maximal 1-factor of a plane elementary graph are given. A peripheral face ▫$f$▫ of a plane elementary graph is reducible, if the removal of the internal vertices and edges of the path that is the intersection of ▫$f$▫ and the outer cycle of ▫$G$▫ results in an elementary graph. We characterize the reducible faces of a plane elementary bipartite graph. This result generalizes the characterization of reducible faces of an elementary benzenoid graph.
Keywords: mathematics, graph theory, plane elementary bipartite graph, reducible face, benzenoid graph
Published: 31.03.2017; Views: 257; Downloads: 104
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5.
Displacements in the exploratory tunnel ahead of the excavation face of Šentvid tunnel
Jure Klopčič, Janko Logar, Tomaž Ambrožič, Andrej Štimulak, Aleš Marjetič, Sonja Bogatin, Bojan Majes, 2006, original scientific article

Abstract: Fitting the displacement function to the measured displacements enables the assessment of the stabilization process of the observed cross section and the determination of its normal behaviour. The displacement function consists of three parts. Whilst the third part has been successfully applied for several times and thus proven to be very well defined, the first two parts were defined only on the basis of numerical simulations. To overcome this deficiency and to obtain the necessary coefficients of the pre-face part of the displacement function, the 3D displacement measurements ahead of the face due to tunneling should be performed. Such measurements were performed in the exploratory tunnel of the Šentvid tunnel during the excavation of the main tunnel. This paper presents the Šentvid tunnel project, the method of the 3D displacement measurements, the results of these measurements and their interpretation according to the geological structure of the site with an emphasis on items important for the coefficients of the displacement function.
Keywords: tunnels, exploratory tunnel, geodetic displacement measurements, pre-face displacements
Published: 17.05.2018; Views: 248; Downloads: 21
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6.
The stability of the excavation face of shallow civil and mining tunnels
Pierpaolo Oreste, 2011, original scientific article

Abstract: The stability of the excavation face of shallow tunnels excavated in difficult ground conditions is currently a relevant problem in the sector for tunnelling and mining. Even though face-reinforcement interventions with fibreglass dowels have proved to be efficient, there is still no reliable analysis and dimensioning method available. A new calculation procedure is illustrated in this paper for the analysis of the face static condition in shallow tunnels, also when reinforcement interventions with fibreglass dowels are used. The procedure is based on the limit-equilibrium method applied to the ground core ahead of the face. The main result of the calculation is that the safety factor of the excavation face is also obtained in the presence of reinforcements and from this it is then possible to proceed with the dimensioning of the intervention. The procedure has been applied to two real cases and satisfactory results have been obtained.
Keywords: fibreglass dowels, face reinforcement, surface tunnel, limit equilibrium method, factor of safety
Published: 13.06.2018; Views: 157; Downloads: 48
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