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

Primena hidrostatičkog klipnog uređaja za proveru sile pritezanja i dilatacije zavrtnja pri ostvarivanju zavrtanjske veze

For the most responsible screw connections (especially those with large prestressing) it is very important to precisely define the required tightening force Fp which must not be less than the minimum necessary force Fpmin, nor greater than the maximum permissible force Fpmax . If Fp Fmax plastic deformations may occur and consequently permanent damage of some elements of screw connection.Therefore, the tightening force should be defined as precisely as possible, and then in practice it needs to be adequately measured and controlled in a screw connection. The paper presents an original laboratoryexperimental method for measuring the forces and dilatations of the screw during tightening based on the application of a special hydrostatic piston device as well as a brief description and operating principle of the device. The device was designed at the Higher Technical School of Mechanical Engineering in Trstenik and it can be used for laboratory exercises in technical schools and faculties, as well as in the industry for checking the mechanical properties of the screws before being mounted, and also for various experiments in research laboratories and institutes.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

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

Optimization of trapezoidal cross section of the truck crane boom by lagrange's multipliers and by differential evolution algorithm (DE)

The cross sections of truck crane booms are complex box-like cross sections, which should provide continuous stress allocation. It is difficult to analytically determine optimal relations among geometric parameters of such cross sections. The paper deals with the method for determining relations among geometric parameters in order to achieve the optimal shape of the cross section. The method is based on Lagrange's multipliers used for determination of extreme values. The optimisation of geometric parameters has also been done with the method of differential evolution (DE). The optimisation of the cross section is based on the strength criterion. The results of the applied methods have been verified by means of numerical example for an existing solution. The comparative analysis of the results of both methods has also been done. © 2011 Journal of Mechanical Engineering. All rights reserved

Parameters influencing the dynamic behaviour of the carrying structure of a type H portal crane

© 2016 Journal of Mechanical Engineering. This paper deals with the problems investigating of parameters that influence the dynamic behaviour of the carrying structure of type H portal cranes with high carrying capacities excited by the motion of the crane and the load swing. The introduction of the paper presents the importance of the problem of the dynamics of structures. In accordance with the given problem, dynamic spatial models of the boom and portal of the crane were formed and solved. The main part of the paper presents a modal analysis and determines dynamic responses of the space structure with the application of the finite element method and direct integration. The influence of changes in speed and acceleration on the dynamic response of the structure was analysed. The influence of the change of boom rotation angle on the dynamic response of the structure was also analysed. The investigation results provide significant bases and conclusions for designing portal cranes and continuation of research in this field

OPTIMIZATION OF THE BOX SECTION OF THE MAIN GIRDER OF THE DOUBLE BEAM BRIDGE CRANE ACCORDING TO THE CRITERIA OF LATERAL STABILITY AND LOCAL STABILITY OF PLATES

Abstract The paper considers the problem of optimization of the box section of the main girder of the double beam bridge crane for the case of placing the rail above the web plate. Reduction of the girder mass is set as the objective function. Research on the mutual dependence of geometric parameters of cross section, and their ratio, using the method of Lagrange multiplier as characteristic criteria is done. Also, the paper shows an algorithm for selection of the optimal criteria and determining the optimal geometric parameters of cross section. The criteria of lateral stability and local stability of plates were applied as the contraint functions. The obtained results of optimization of geometrical parameters were verified on numerical examples

Increasing the Efficiency of Railway Transport by Improvement of Suspension of Freight Wagons

Railway transport has a very important role in economy of every country. The efficiency of railway transport depends both on the quality of transport organization and on the technical reliability of the railway rolling stock. During operation of the railway freight wagons in the last years, a large number of breaks of suspension system elements have been noticed. This feature is especially reported at four-axle double wagon for coal transport (designated Fbd) and three-axle wagon for transport of cars (designated DDam). Frequent breaks of suspension system elements reduce the efficiency of transport and in some cases cause derailment of wagons and lead to large economic losses. In this paper, the causes of breakage of suspension on both wagons (Fbd and DDam) have been analyzed, but also the possibilities of how to resolve these problems, i.e. how to reduce them to a minimum or avoid them completely

Analysis of the influence parameters on the support structure stiffness of large radial-axial bearings

© 2019 Journal of Mechanical Engineering. All rights reserved. In certain types of crane and earth-moving machinery, such as portal cranes, loaders and excavators, the transfer of loads to crane tracks or the terrain is accomplished by means of undercarriage frames composed of box-like girders. The hypothesis that all four supports of the undercarriage frame do not lie in the horizontal plane is the basis for the formation of a calculation model. This paper analyses the influence of geometric parameters of box-like girders on the magnitude of additional forces at the supports of those frames when one of the supports is raised or lowered relative to the horizontal plane for the size Δ. Theoretical dependences between moments of inertia and stiffness under bending and torsion of those girders were thus established. Obtained relations leads to more concise forms of expressions for influential coefficients in Maxwell-Mohr integrals and simplifies optimization methods in the design of support structures. With experimental verification of the results, the influences of geometric parameters on the stiffness of the support structure are confirmed, and preconditions are created for further analysis of the connection made by large diameter bearings