Determination analysis of temperature regimes, functional characteristics and sliding curves of a hydrodynamic clutch

Analysis of output quality of power transmitters is possible in position when characteristics are determined earlier. This is the reason why we focused on determination of these characteristics for a concrete power hydro-transmitter. This means that the investigation task primarily consisted of determination of functional characteristics, defining of the sliding curves and temperature regimes of a concrete hydrodynamic clutch. Results of velocity and pressure field investigations in the working space of this clutch, obtained by use of the same test setup, are the basis for determination and analysis of the functional characteristics, sliding curves and temperature regimes. In this work we also analyzed function of the hydrodynamic transmitter in assembly with an internal combustion engine, as well as a process of acceleration and deceleration of a vehicle with this assembly in it

Optimal welding technology of high strength steel S690QL

In this paper is presented the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic - proneness to appearance of cold cracks.  That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint

Effects of welding on mechanical and microstructural characteristics of high-strength low-alloy steel joints

© 2018 Institute of Physics Publishing. All rights reserved. In this paper effects of welding on mechanical and microstructural characteristics of high-strength low-alloy steel joints is presented. Testing was done at models prepared with V-groove butt joints that are done by two different welding processes. Considered welding processes were done by MMA or MIG for root pass and MAG for other passes with related consumables. Experimentally determined basic mechanical characteristics were put in correlation to relate ones that were numerically calculated. The experimentally obtained yield strength and tensile strength showed that welding process MMA/MAG provide better mechanical properties then MIG/MAG. It is implicated that selection of welding process at high-strength low-alloy steels is multi criterion analysis. If only proper welding is obtained, applications of high-strength low-alloy steel are adequate. Those applications caused specific problems related to its specific characteristics and properties especially weldability. As welding processes can be analysed from different aspects, selection of specific welding process at high-strength low-alloy steel are more complex

Analysis of certain physical properties of four rock materials

© 2019 Published by the Serbian Academic Center. This paper presents an analysis and the test results of certain physical properties of the rock materials excavated from quarries in Serbia. The four rock aggregates, considered in this analysis, are used for building the driveway constructions' layers on roads, streets, airports and base layers on railways. To that purpose, both the general and specific technical properties (petrographic, physical, mechanical and technological) of those rocks must be known to users. The four rocks, whose physical properties are analyzed, are the most important types of the building stones: limestone, dolomite marble, calcite-dolomite marble and andesite. Their physical properties tested included volumetric mass, specific mass (density), porosity and water absorption. The service life, reparation jobs and maintenance procedures of the construction machinery parts, which come into direct contact with building materials like rocks and stones, strongly depend on those stones' properties. The four tested rock materials belong into a group of the massive rocks with various porosities and tendency to absorb water

Influence of the Friction Time on the Shape and Microstructure of the Mixing Zone of the Friction Welded Joint

© 2016. Published by Manufacturing Technology. All rights reserved. An analysis of the friction time influence on creation and structure of the mixing zone during the friction welding process of the two dissimilar steels is presented in this paper. The changes were monitored on the two welded samples, made of the highly-alloyed steel HS 6-5-2-5 and the high carbon C60 steel. The objective of this work was to show how the mixing zone is created and to point to its influence on the quality of the whole welded joint, since it is characterized by the inhomogeneity of the microstructure and the chemical composition. Those problems arise due to the thermal and deformation conditions, so during the experiment the welding pressure (70-90 MPa) and the welding time (3-18 s) variations were monitored. Experimental results have shown that the shape and the structure of the friction zone are strongly dependent on the friction time and that by its variation one can obtain the desired structure and thus the quality of the friction welded joint. Based on obtained results the minimum value for the friction time is recommended

Selecting the Low Alloy-Tempered Steel for Manufacturing the Highly Loaded Responsible Parts

The selecting procedure of the optimal material for manufacturing the highly loaded responsible parts for military applications is presented in this paper. The considered part is in exploitation subjected to complex compressive-impact loading and cyclically to high temperatures, as well. The proper selection of material can be done exclusively based on the theoretical and experimental analysis of properties of the steel in question. The theoretical and experimental selecting of adequate steel for manufacturing such parts is done based on requirements arising from their working conditions. Based on the available data for various steels, chemical composition, mechanical and technological properties, available CCT diagram, the optimal steel was selected for the given working conditions. After the selection of the material, experimental investigations on specially prepared material samples were conducted. The real chemical composition of material was established, its most important mechanical properties were determined, the hardness was measured and the microstructure was determined, as well. After the conducted theoretical and experimental investigations, the responsible machine part was manufactured from the selected material by forging. Then, the mechanical and heat processing was executed, after which the part was tested in the real working conditions. Based on investigations of part's behavior in the real working conditions, it was concluded that the selection of the material was adequate

Comparison of the PMMA mechanical properties after cutting by the laser beam and milling

© Faculty of Mechanical Engineering, Belgrade. This research was focused on characterization of the influence of laser cutting on the material made from the PMMA. The comparison of mechanical properties of samples cut by the laser beam to the properties, obtained after the conventional method of cutting by milling, are presented in this paper, as well. The 4 mm thick samples were prepared from the PMMA and subjected to tensile test to establish their material strength after the two different types of cutting. Samples that were cut by the laser beam were also subjected to tempering to improve their mechanical properties. It was concluded that the way of cutting has a strong influence on the PMMA samples mechanical properties. The outcome of the experiment is a direct assessment of roughness of the cut samples. It is shown that the laser cutting produces lower values of the surface roughness. However, for manufacturing the structural elements, the more suitable would be application of the milling technology since it results in better mechanical properties of the cut sample

New method of defining of process parameters in double side thinning strip ironing test

© 2020 Published by Faculty of Engineering. New way for defining of main process parameters procedure in the strip ironing process with double side thinning, as well as appropriate experimental results are presented in this paper. Given is improved analysis for friction coefficient and contact pressure defining. Classical common so called “Schlosser model” and other similar models are not suitable in certain cases, and give unreal values for both of main process parameters. Expressions obtained here were verified in suitable examples which are, also, presented in the paper. Verification was performed on the base of experimental results. Realized was the single and four phases ironing process of mild steel DC04 in sheet stripes drawing test. Stripes were 20 mm wide and 2.5 mm thick. Lateral force intensities were 5, 10 and 15 kN. Maximal obtained thinning deformation in one phase was about 17 %. Appropriate lubrication with mineral oil and grease was used in conditions of lower speed of 20 mm/min. Results shows that proposed improved procedures enables more precise process monitoring and precise quantification of lateral force, contact pressure and thinning strain influence on friction

Impact of the hard facing technology and the filler metal on tribological characteristics of the hard faced forging dies

© 2015, Strojarski Facultet. All rights reserved. The forging dies are parts, which are operating at elevated temperatures, while simultaneously subjected to variable loads that can be compressive - even impact and shear. Impact of the hard facing technology is very strong since varying of the hard facing parameters directly affects the output characteristics of the hard faced layers. The criterion for estimating that impact was based on results of performed tribological investigations. The tribological parameters that were monitored were the friction coefficient, the wear scar/trace width and the wear area of the hard faced layers, with the two different types of lubricants. Hard facing technology implied selection of the welding process, filler metals, preheating temperatures and other parameters of the hard facing process. The influence of the proposed hard facing technology was determined by monitoring hardness, microstructure and wear resistance of the executed joints after the hard facing and after tempering. The objective of this work was to establish the correlation between the selected hard facing technology, filler metals and applied heat treatment on mechanical and tribological characteristics of the executed hard faced layers