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Error estimates for Gauss-type quadrature rules for variable-sign weight functions
No full textWhen the Gauss quadrature rule is applied, the weight function (or the measure) is usually assumed to be non-negative on the integration interval. In this paper, we consider a recently introduced Gauss-type quadrature formula with respect to a weight function that changes sign in the interior of the integration interval. To economically estimate the error of that formula, we propose extensions based on the Gauss-Kronrod, averaged Gauss, and generalized averaged Gauss quadrature rules. Numerical examples illustrate the accuracy of such introduced error estimates
The application of the thin and lumped appreoach for comparision of the drying kinetic registered for various thin clay slabs
No full textSMART, ERGONOMIC AND SUSTAINABLE MINING MACHINERY WORKPLACES: AN OVERVIEW OF THE SMARTMINER PROJECT
Get PDFDespite being the oldest, the mining industry continues to be a major source of pollution, with more people killed or injured than in all other industries. Additionally, social tension related to this sector is widespread around the world, since mining businesses continue to have a significant negative influence on land, water, air, biota, and people through direct and indirect mechanisms. The mining machinery workplaces, which are in the focus of this study have the largest environmental footprint. The dominance of technology-centered design in present research streams is most likely the explanation for the lack of advancement in the mining industry. The SmartMiner project creates shift from technology-centered design and its concept creates solutions for improving the standard of environmental quality in complex systems and suggests a paradigm change to a Human and Data-Centric Engineering. By aligning advanced operator I4.0&5.0 and society S5.0 standards, the SmartMiner project develops solutions for raising the level of environmental quality in complex interactions between physical, behavioural, and organizational processes field. Proposed paradigm can be easily transferred to other industries. The safety of mining machinery operators in their immediate surroundings and their regular alignment with value chain stakeholders are the first steps in our original idea approval process. Research moves to the operator macro-environment, which is determined by organizational contextual factors, and is encompassed by the development of intelligent, ergonomic, non-invasive, and dependable operator aid systems for regulating physical environment job stressors - noise, human vibration, lighting, temperature, air quality, workplace layout issues, etc., with high potential to solve environmental and human health issues and to influence overall performance
A RISK EVALUATION OF BULLDOZER DOWNTIMES AND ITS ECONOMIC JUSTIFICATION IN OPEN-PIT MINES
Get PDFThe mining industry has been steadily expanding annually to keep up with the increasing demands. Consequently, used machinery needs to work efficiently, which indicates that unexpected downtimes should be at the minimum possible level. Proper identification and risk evaluation of the potential breakdown is the most important element for efficient equipment maintenance and breakdown prevention. This research has focused on its reliability function determination and analyzed the consequences of downtime and the cost of repairs over a period of one year. Delays on the observed mining machine were classified according to the type of downtime: mechanical, technological, power/electricity, and downtime due to external influences. Input elements for risk assessment were severity of consequence (S), probability of occurrence (O), and failure detectability (D). The method used in this paper is based on the cost of maintenance and the impact of bulldozer breakdowns on reliability in order to maintain profitability and, by reducing the number of unwanted events caused by sudden failure of parts, increase safety during operation. Results show that the monitored bulldozer belongs to the lowest defined risk class, so its use is economically justifiable
Programming methods and program verification for 3-axis reconfigurable hybrid kinematics machine
No full textThis paper presents programming methods and program verification for the 3-axis reconfigurable hybrid kinematics machine MOMA V3, which represents an educational desktop milling machine with a horizontal position of the main spindle. The paper considers the different programming and program verification methods. For programming used CAD/CAM system PTC Creo, specialized CAM software CUT3D and new programming method based on STEP-NC. Program verification is based on tool path simulation, material removal simulation and virtual machine simulation. The paper presented the virtual machine in the programming system and the virtual machine integrated with the LinuxCNC control system. Final verification was achieved during the testing on machine by machining the selected workpieces which programmed with different programming methods.ISSN: 2620-2832
e-ISSN: 2683-4111 (On-line)
Co-Editors in Chief: dr Miladin Stefanović, dr Slobodan Mitrovi
Lateral-Directional Aerodynamic Optimization of a Tandem Wing UAV Using CFD Analyses
No full textThis paper presents the second stage of a tandem fixed-wing unmanned aerial vehicle
(UAV) aerodynamic development. In the initial stage, the UAV was optimized by analyzing its
characteristics only in symmetrical flight conditions. Posted requirements were that both wings
should produce relevant positive lift, the initial stall must occur on the front wing first, the center
of pressure should be close to the center of gravity, and longitudinal static stability should be in the
optimum range. Computational fluid dynamic (CFD) analyses were performed, where the applied
calculation model was derived from the authors’ previous successful projects. The eighth version
TW V8 has satisfied all longitudinal requirements. Lateral-directional CFD analyses of V8 showed
that the ratio of the lateral and directional stability at the nominal cruising regime was optimal, but
both lateral and directional static stabilities were too high. On further development versions, the
lower vertical tail was eliminated, a negative dihedral was implemented on the front wing, and
four inverted blended winglets were added. Version TW V14 has largely improved lateral and
directional stability characteristics, while their optimum ratio at the cruising regime was preserved.
Longitudinal characteristics were also well preserved. Maximum lift coefficient and lift-to-drag ratio
were increased, compared to the V8
Artificial Neural Network Model for Predicting Excavator Downtime
No full textPrevious research shows the significance of maintenance in enhancing performance levels and reducing
system costs of equipment. This paper aims to develop a quantitative model for predicting the failure rate of
excavators using artificial neural networks (ANN). As an input to the ANN, the duration times of 590
excavator downtimes measured over 198 days at the mining site in Serbia were used to obtain a classification
of failures longer than an hour based on the previous 14 days, in aim to prevent potential indirect financial
losses which could be over 15000€/hour. A Pareto analysis of the observed data was also performed and
showed the technological type of downtime as the most frequent. The results show that the ANN modeling is
suitable for mapping the non-linear relationship between excavation activities and the failure rates of
excavators. The results showed that the proposed ANN model provides an accurate estimating tool for the
early planning stage to predict failure rates of excavators. Future research avenue proposal is directed at
monitoring and forecasting the exact duration of excavator downtime in real-time
Matrices in Gauss-type quadratures for variable-sign weight functions
No full textWe consider a recently proposed Gauss-type quadrature formula with respect to a weight function that changes sign in the interior of the integration interval. An important step in its construction is to introduce a modifier function used to transform the given integral into a sum of one integral that does not cause a quadrature error and the other integral with a property that the points from the interior of the integration interval at which the weight function changes sign are the zeros of its integrand. Determining a modifier function requires solving an associated system of linear equations. For the same integral, different modifier functions can be chosen, and hence different linear systems can be obtained. From a theoretical perspective, only necessary is that the associated system has a solution, but from a computational perspective, it is also important that the associated system is not too ill-conditioned and that the structure of its matrix is as simple as possible. We analyze the conditions under which it is guaranteed to obtain, for instance, a system with a Vandermonde matrix or a system with an identity matrix. We also give examples where systems with an arbitrary matrix are obtained
Sensitivity and Eigensensitivity Analysis in Structural Dynamics Using Finite Element Substructuring
No full textThis paper explores sensitivity and eigensensitivity analysis methods to optimize structural performance in the field of structural dynamics, with a focus on vibration control and resonance management. Sensitivity analysis is crucial across engineering fields, allowing assessment of system responses to variations in design parameters. Within structural dynamics, eigensensitivity analysis examines how design changes impact eigenvalues and eigenvectors, particularly when it is necessary to control resonant frequencies for improved structural safety and performance. To conduct efficient dynamic simulations, finite element analysis (FEM) is applied to complex structures. Given the computational demands of models with numerous degrees of freedom, this study introduces a substructuring approach. By dividing the structure into interconnected substructures, each analyzed separately with a reduced eigenpair set, the model achieves substantial computational efficiency while maintaining accuracy in critical vibration modes. This substructuring technique not only enhances analysis feasibility but also supports rapid adjustments in design, enabling effective resonance frequency management and optimization. The case study demonstrates the practical application of eigensensitivity analysis in dynamic structural modification, achieving targeted performance improvements with reduced computational resources. Findings underscore the potential of combining sensitivity and eigensensitivity analyses with FEM substructuring for streamlined and effective structural design.Project no. 451-03-65/2024-03/20010
An advanced machining robot flexible programming methodology supported by verification in a virtual environment
No full textThe solutions for robot offline programming use different programming environments to facilitate
the deployment of robots in machining tasks with the development of specific postprocessors.
There is no easy exchange of data between programming software to realise robot machining
tasks. This paper presents a flexible programming methodology using several interchange file
formats that can be easily exchanged between different CAD, CAD/CAM, or specialised robot
programming software. Integrating the standard programming based on CAD, CAD/CAM systems,
and STEP-NC protocol through different output files enables data interoperability during the
realisation of the robot machining tasks. The developed methodology is proposed for executing
programming, verification supported by a virtual environment, postprocessing, and machining by
industrial robots. It uses the software for programming machine tools and adapts them to the
specifics of robots and their programming languages using a developed postprocessor. The
presented methodology enables the programming of robots for 2.5 to 5-axis machining tasks
depending on the neutral file format used. Programming verification was realised, first, by simula
tion on configured virtual robots and developed robot native language editor and, second, by
machining on the available robots. These experiments include different contours and shapes and
file formats, which show the programming’s reliability and accuracy