Research on parameters influencing performance of vibrating platforms during transporting the dry earth mass

Jedan od osnovnih zahtjeva pri korištenju vibracijskih transportnih platformi ogleda se u ostvarenju maksimalnog učinka tijekom njihovog rada, uz istovremeno usitnjavanje mase i odvajanje pojedinih sastojaka iz same mase. U radu je primjenom response surface methodology (RSM), koja je bazirana na design of experiments (DoE), formiran matematički model za istraživanje utjecajnih geometrijskih i kinematskih parametara na optimalni radni učinak vibracijske platforme. Provedenim eksperimentom, korištenjem višefaktornog ortogonalnog plana tipa 2k formirane su krive hiperboličkog tipa i utvrđeno je da se one uvijek nalaze između krivih koje su formirane na temelju rezultata teorijskog modela, čime su potvrđeni i verificirani istraživački rezultati.One of the main requirements related to application of vibrating platforms is to achieve the maximum productivity during their operation and, at the same time, to break mass and separate some components from the mass itself. Application of response surface methodology (RSM), which is based on design of experiments (DoE), resulted in mathematical model for exploring geometrical and kinematic parameters influencing the optimum operating performance of vibrating platform. The experiment was conducted by means of multifactor orthogonal plan type 2k and hyperbolic curves were formed. It was also determined that these curves are always between the curves formed on the basis of results of theoretical model, which verifies the research results

Analysis of the Drive Shaft Fracture of the Conveyor Belt for Transport of Coal

The conveyor belt for slag and coal transport in the open mine pit "Kolubara" – Serbia is driven by means of two drive drums, attached on separate shafts. Each shaft is driven by two electric motors on both sides. During exploitation, the conveyor belt drive shafts are subjected to torques and transverse forces due to belt tension. The gearboxes and the bearing units on both sides of the drive drum support each shaft. A fracture of one of the drive shafts of the conveyor belt occurred at its connection point with the gearbox. The first part of the paper defines the loads relevant for shaft calculation, based on measurements in different phases of operation and the manufacturer’s data. It is followed by the FEM analysis and fatigue analysis, for the most unfavourable load case. It has been established that the critical stress value has occurred near the connection point between the shaft and the gearbox, in the fracture zone. The second part of the paper presents chemical composition and mechanical properties of material, as well as metallographic examination of fracture surface. The experimental test procedure shows that the fracture has occurred not because of an error in the material but as a consequence of the inadequate heat treatment. Superposition of two negative influences: material fatigue and inadequate heat treatment, expressed in the cross section at the point of fracture is the main case of the conveyor belt shaft fracture

Analysis of the Drive Shaft Fracture of the Conveyor Belt for Transport of Coal

The conveyor belt for slag and coal transport in the open mine pit "Kolubara" - Serbia is driven by means of two drive drums : attached on separate shafts. Each shaft is driven by two electric motors on both sides. During exploitation, the conveyor belt drive shafts are subjected to torques and transverse forces due to belt tension. The gearboxes and the bearing units on both sides of the drive drum support each shaft. A fracture of one of the drive shafts of the conveyor belt occurred at its connection point with the gearbox. The first part of the paper defines the loads relevant for shaft calculation, based on measurements in different phases of operation and the manufacturer's data. It is followed by the FEM analysis and fatigue analysis, for the most unfavourable load case. It has been established that the critical stress value has occurred near the connection point between the shaft and the gearbox, in the fracture zone. The second part of the paper presents chemical composition and mechanical properties of material, as well as metallographic examination of fracture surface. The experimental test procedure shows that the fracture has occurred not because of an error in the material but as a consequence of the inadequate heat treatment. Superposition of two negative influences: material fatigue and inadequate heat treatment, expressed in the cross section at the point of fracture is the main case of the conveyor belt shaft fracture

Komparativna analiza i optimizacija T i I poprečnih preseka dizalične kuke primenom dva algoritma inspirisana fizikom

This paper presents analysis and optimization of the geometric parameters of T and I cross-sections of crane hook, observed for the most critical location of its structure. The reduction of the cross-sectional area of crane hook was set as the goal in this study. The stresses at characteristic points of the most critical cross-section are taken as constraint functions, calculated according to Winkler-Bach theory, and some geometric conditions are set, too. Two metaheuristic algorithms based on the laws of physics, Charged System Search (CSS) algorithm and Thermal Exchange Optimization (TEO) algorithm, were selected for optimization methods, using by MATLAB software package. The goal of this research is to show that the proposed cross-sections give significant savings in comparison to standard crane hook, wherein the one standard capacity was observed. Both observed cross-sections were analyzed in two variants, and the comparison of their optimization results was performed to show which one achieves the best results. Also, the comparison of the applied optimization algorithms was performed.Publishe

Aksijalno-radijalni ležaj kao segment veze okretne platforme sa nosećom konstrukcijom

The paper presents the connection of rotating platforms in building and transport machines depending on the type of driving mechanism. A special attention is paid to axial-radial bearings having big diameters made by prominent manufacturers. There are some necessary conditions which have to be met by supporting frames because working capacity of the bearings depends on them. Also, the law of distribution of load of moment of external forces is proposed because it provides identification of maximum load as a starting basis for further research on determination of optimal laws of distribution of acting forces which are caused by the moment of forces.Publishe

Prilog analizi krutosti ramova utovarno-istovarnih kolica pretovarnih mosnih dizalica

The paper analyzes the dependence of the stiffness of the support frames of the cranes with loading-unloading trolley on the change of geometrical parameters of the frames. The calculation model of the frames with transverse stiffness was formed because it additionally stiffens the supporting surface of the frames for connection with the axial-radial bearing. The relations of characteristic geometrical sizes of longitudinal and transverse elements were established, at which the necessary stiffness of the frames of loading-unloading trolley was achieved. Also, the variables and constants of geometric size were introduced, as well as the constant values of appropriate coefficients, the variation of which provides the possibility to form the optimal structure of the frames of loading-unloading trolley.Publishe

Stabilnost i optimizacija stuba dizalične staze

This research has presented the built-up column analysis with batten, applied to crane runaway support, where stability is put in the foreground. Also, optimization of all essential geometrical parameters of the built-up column was performed for a given height of the crane column and changing the load capacity. The chord members were composed of as-welded I-sections instead of fabricated hot rolled sections witch are commonly used in these constructions. The mass of the built-up columns, which consists of the chord and Web members (battens) members, was taken as the goal function in this research. Additional stability and load capacity conditions were used as constraint functions, as well as specific design recommendations. The optimization procedure was performed in the Ms. EXCEL software package, using the GRG2 algorithm because certain benefits are essential in this optimization problem. In this way, the justification of applying the proposed model of calculation and optimization was shown because the necessary geometrical parameters can be reached very quickly when designing these types of structures, considering that there are a large number of variables and constraint functions. It is also shown how the mass of the column changes and the optimal geometric parameters when the compression force on the column of the runaway crane support increases.Publishe

Primena metode konačnih razlika kod određivanja ugiba nosača kontinualno promenljivog poprečnog preseka

Amongst others, the deformation criterion is to be fulfilled in the process of steel structure design. Often, it can be more restrictive than the stress criterion. Although the stress state is within the permissible limit, excessive structure deformation can lead the additional load to emerge in the carrying structure and cause improper operation and shorter life of attached devices and equipment. For that reason, besides other requirements, the allowable deformation limits of the steel carrying structure are defined. The stress-strain analysis of the structure is usually conducted by utilization of finite element method (FEM) in the early phase of the design process. Alternatively, this paper shows the application procedure of the finite difference method (FDM) for the deflection determination on the simple elastically restrained cantilever beam with continuously varying box-like cross-section and linear change of section height. Dependence of the deflection on the design parameters is obtained through programming in MATLAB and the comparison is made with the results from the finite element model built in ANSYS. The results from both numerical approaches showed excellent compliance.Publishe

Application of the MODIPROM method to the final solution of logistics centre location

Awareness of the role of logistics centres is the precondition for successful planning, optimization, design, management, control and analysis of logistics processes and subsystems. Transportation requirements in supply chains, ecological requirements and the need for quality life in cities particularly emphasize the importance of selection of logistics centre locations, manner and time of supply. Taking into account the significance of selection and ranking of different locations, it is necessary to compare, as objectively as possible, the influences of various criteria and reduce them to a common function, i.e. present the methodology of solving complex problems associated with ranking of alternatives. The proposed method is expected to be a comprehensive tool of decision makers during the selection of the optimal logistics centre locations

Analiza stanja vitalne čelične konstrukcije kabine rukovaoca rotornog bagera nakon havarije i sanacije

There are 2 bucket -wheel reclaimers, internally labelled as DU1 and DU2, made by French manufacturer 'Ameco', that operate at the open pit surface mine which belongs to the thermal power plant 'Nikola Tesla A' in Obrenovac. They are moving along the polar path and it should be noted that there are only 3 reclaimers of that kind in Eastern Europe. The third bucketwheel reclaimer, made by the same manufacturer, operates at the open pit surface mine that belongs to the thermal power plant 'Nikola Tesla B' in Obrenovac. In this paper the state analysis of the vital steel structure of the bucket-wheel reclaimer DU2 operators' cabin, made of pipes of various diameters and thicknesses, after the breakdown caused by a rock that hit the horizontal support of the structure is presented. The rock was located in the excavated coal within a bucket of the bucket-wheel reclaimer. The horizontal support of the operators' cabin structure has Bent and welded joints between flanges at the middle of the horizontal support, as well as welded joints at bonds of the horizontal support with vertical supports of the structure, have cracked due to the impact of the rock. Taking into account the fact that the user of the bucket-wheel reclaimer does not own the design and technical documentation, damage repair was carried out under the assumption that the lattice structure of the operators' cabin was made of structural steels, which are mostly being used for the manufacture of bucket-wheel reclaimers. On the basis of state analysis after the temporary repair of damages the conclusion arose that for the permanent provision of integrity of the support steel structure of the bucket-wheel reclaimer DU-2 operators' cabin as a whole it is necessary to replace the damaged horizontal support.Publishe