1. Analysis of a dilatometer test in over-consolidated sediments, basin of the Duero river, SpainFélix Escolano Sánchez, Manuel Bueno Aguado, 2015, original scientific article Abstract: A dilatometer test is a useful method for in-situ geotechnical surveys. It can be compared with the results obtained using a mathematical model. The mathematical model of concentric rings shown in this article is governed by the constitutive equation of the “Hardening Soil Model”. A large number of tests made on the Dueñas Geological Facies, with a consistency ranging from firm clays to soft rocks, are compared to the model results. In this way, the “Hardening Soil Model” parameters are adjusted to the Dueñas Facies materials.
Keywords: Dueñas, geotechnical parameters, hardening soil model, soft rocks and clays deformation
Published in DKUM: 14.06.2018; Views: 1304; Downloads: 100
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2. Synthesis and characterization of hardened Cu-Fe-Ni-P alloyGoran Brovč, Goran Dražić, Blaž Karpe, Igor Đorđević, Gorazd Lojen, Borut Kosec, Milan Bizjak, 2015, original scientific article Abstract: In the manufacturing industry of electrical contacts, the prohibition of the use of toxic metals (Cd, Be), and desire to avoid the alloying with precious metals (Ag) has created a need for new alloys with good electrical conductivity and high mechanical properties at elevated temperatures. As a potentially useful material for this purpose, we have analyzed the continuously cast Cu-Fe-Ni-P alloy in various heat treatment conditions. Sequence of phase transformations during heat treatment was followed by 4 point D.C. electrical resistivity measuring method, and analyzed by scanning (SEM) and transmission (TEM) electron microscopy. Measurements of Vickers hardness and electrical conductivity after various heat treatment procedures indicate on high potential of Cu-Fe-Ni-P alloys as a material for electrical contacts.
Keywords: copper alloys, precipitation hardening, electrical contacts, electrical conductivity
Published in DKUM: 03.07.2017; Views: 2320; Downloads: 97
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3. A new method for estimating the Hurst exponent H for 3D objectsMatej Babič, Peter Kokol, Nikola Guid, Peter Panjan, 2014, original scientific article Abstract: Mathematics and computer science are very useful in many other sciences. We use a mathematical method, fractal geometry, in engineering, specifically in laser techniques. Characterization of the surface and the interfacial morphology of robot-laser-hardened material is crucial to understand its properties. The surface microstructure of robot-laser-hardened material is rough. We aimed to estimate its surface roughness using the Hurst parameter H, which is directly related to the fractal dimension. We researched how the parameters of the robot-laser cell impact on the surface roughness of the hardened specimen. The Hurst exponent is understood as the correlation between the random steps X1 and X2, which are followed by time for the time difference t. In our research we understood the Hurst exponent H to be the correlation between the random steps X1 and X2, which are followed by the space for the space difference d. We also have a space component. We made test patterns of a standard label on the point robot-laser-hardened materials of DIN standard GGG 60, GGG 60 L, GGG 70, GGG 70 L and 1.7225. We wanted to know how the temperature of point robot-laser hardening impacts on the surface roughness. We developed a new method to estimate the Hurst exponent H of a 3D-object. This method we use to calculate the fractal dimension of a 3D-object with the equation D = 3 - H.
Keywords: fractal structure, Hurst exponent, robot, hardening, laser
Published in DKUM: 14.03.2017; Views: 1685; Downloads: 159
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4. Problems associated with a robot laser cell used for hardeningMatej Babič, Matjaž Milfelner, Igor Belič, Peter Kokol, 2013, original scientific article Abstract: Laser hardening is a surface-hardening process. It is used exclusively on ferrous materials suitable for hardening, including steel and cast iron with acarbon content of more than 0.2 %. This article describes robot laser hardening, the results of previous work, research and experience with robot laser hardening. The second part of the paper describes the problems associated with robot laser hardening at different angles. We wanted to find the impact of the angles on the hardness of the material. Therefore, we directed the laser beam at different angles, including perpendicular, in the process of hardening. We made test patterns of a standard label on the materials of DIN standard 1.2379.
Keywords: hardening, robot, laser, parameters, hardening, robot laser, parameters
Published in DKUM: 10.07.2015; Views: 1858; Downloads: 119
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5. Hardening of concrete with a planned delayed ettringite formationSamo Lubej, Andrej Ivanič, Milan Radosavljević, 2009, published scientific conference contribution Abstract: Delayed ettringite formation (DEF) in cementitious materials is widely considered as a harmful chemical reaction that causes extensive damages in hardened concrete. However, preventative measures and possible improvements in general are not extensively studied and require further attention. In this study was presented an investigation into a type of controlled DEF in places of finely dispersed crystallisation nuclei and provide evidence that the process may improve compressive strength of cementitious materials. The Alkali-Silica Reaction (ASR) in hydrated concrete was achieved with the addition of fly ash and was further accelerated with the Dugganćs test. Achieved strengths and monitoring of microstructure development conducted with electronic microscopy revealed that growth of ettringite crystals in the nuclei led to harmless internal compressive stresses, expansion of hydrated concrete and overall strengthening of the concrete matrix.
Keywords: delayed ettringite formation, concrete, hardening
Published in DKUM: 31.05.2012; Views: 1803; Downloads: 46
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