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Application of 2D and 3D Digital Image Correlation in Biomedical Material and Structure Testing
No full textDigital Image Correlation (DIC) is an advanced non-contact optical method extensively utilized for
full-field strain measurement. This study presents several distinct applications of both 2D and 3D
DIC techniques in the field of biomedicine. Specifically, the research highlights the efficiency of
DIC methods in the precise mechanical evaluation of dental materials, providing essential insights
into their deformation behavior under clinical-relevant loads. The paper evaluates their mechanical
performance and identifying deformation patterns that are critical for predicting functional stability
and reliability. Additionally, 3D DIC has been successfully implemented for monitoring real dental
and biomedical structures (e.g. dental and hip implants), demonstrating the method’s potential in
detecting early signs of material deterioration and structural failure. The results underscore the
versatility and precision of 2D and 3D DIC methods, reinforcing their indispensable role in
advancing material testing and facilitating the development of robust structures for various
biomedical engineering applications
Synthesis and characterisation of metal–glass composite materials fabricated by liquid phase sintering
No full textIn recent years, there has been a global increase in environmental awareness, which has driven the application of natural materials or the synthesis of novel, environmentally compatible materials. Composite materials hold a prominent position among modern materials and are typically developed to achieve resistance to various damage mechanisms, thereby extending the service life of structures. This study presents the synthesis and characterisation of high-density metal–glass composite materials. The commercially available 316L stainless steel powder was used as the matrix material, while andesite basalt powder was used as the reinforcement phase. Andesite basalt aggregate, ground into powder, is a cost-effective, widely available, and environmentally friendly natural raw material. Powder metallurgy was employed to produce the composite materials. Sintering was performed at 1250 ◦C for 30 min in a vacuum. The density of the sintered composite samples was analysed as a function of andesite basalt content, with sintering conducted in the presence of a liquid phase. Composite materials were characterised using optical and scanning electron microscopy, X-ray structural analysis, and hardness testing. This study confirmed that the optimal combination of properties was achieved in the composite with 20 wt.% andesite basalt, present as a glass phase within the 316L steel matrix
Dimensional accuracy assessment of 3D-printed CT specimens produced by selective laser sintering
No full textAdditive manufacturing is increasingly used for producing standardized fracture-mechanics specimens, allowing the fabrication of Compact Tension (CT) samples with complex geometries that would be difficult to machine conventionally. However, the dimensional accuracy of selective laser sintering remains a crucial factor for ensuring reliable mechanical and fracture-toughness measurements. In this study, the geometric accuracy of 3D-printed cobalt–chromium CT specimens was evaluated by comparing three design variants to their corresponding CAD reference models. Optical scanning and qualitative surface-deviation mapping revealed that differences in accuracy were strongly influenced by specimen geometry, particularly in regions involving sharp transitions and stress-concentrating features. While some designs showed noticeable deviations attributable to manufacturing complexity, others remained within acceptable tolerance limits for fracture testing, requiring minimal post-processing. These findings underscore the importance of carefully optimizing build orientation, scanning strategies, and post-processing protocols when using additive manufacturing to produce CT specimens intended for high-precision mechanical characterization
МИНИМИЗАЦИЯ ВРЕМЕНИ ПРИ ОДНОВРЕМЕННОМ ПРОДОЛЬНОМ И ВРАЩАТЕЛЬНОМ ДВИЖЕНИИ КОНЬКА ЧАПЛЫГИНА
No full textАнализируется задача минимизации времени движения конька Чаплыгина в горизонтальной плоскости. В качестве управлений рассматривается сила, направленная вдоль вектора линейной скорости,
и вращающий момент. Применение принципа максимума Понтрягина позволяет установить, что
возможны три типа управления: регулярное управление, принимающее граничные значения («бангбанг») для силы и момента, сингулярное (особое) управление первого порядка для силы и сингулярное управление второго порядка для момента. Если управление является особым для силы на
всем интервале, то решение оптимизационной задачи неедиинственно. Участок особого управления
второго порядка может быть сопряжен с неособым участком только с помощью «чэттеринг»-режима.
Предлагается более простое субоптимальное управление, содержащее конечное количество переключений. Рассмотрены примеры для заданных конечных состояний полностью и частично заданных
конечных состояний, проведен анализ возможных комбинаций особых и неособых дуг траектории.Engleska verzija rada:
DOI: 10.1134/S106423072570062
INFLUENCE OF THE JOINT GEOMETRY ON HEAT ENERGY, GENERATED DURING THE PLUNGE STAGE OF FRICTION STIR WELDING
No full textThe numerical simulation of friction stir welded T-joints made of AA2024 T3 is investigated. Analysis of heat generation due to friction and plastic work is performed, as well as of the reaction force in the normal direction during the plunge stage of the friction stir welding. The effect of joint geometry is studied for butt joints and T-joints produced from the same material. Different tool rotation speeds and tool pin lengths were considered for T-joint FSW welding. It was shown that the temperature at the root of the weld below the tool pin is lower in the T-joint than in the butt joint, due to the efficient conduction of the heat produced through the normal plate. Also, the reaction force was higher for the T-joint than for the butt joint; so, heat production by friction was more intense in comparison with the heat produced by plastic deformation. The reaction force was moderately increased for the tool with a shorter pin, increasing both components of the heat produced. An increase in the tool rotation speed decreased the resistance to the tool plunging into the T-joint, increasing the frictional heat and decreasing the amount of heat generated by plastic deformation.contr. 451-03-136/2025-03/200287, 451-03-137/2025- 03/200105 and 451-03-136/2025-03/20013
VIRTUAL REALITY ENVIRONMENT FOR TEACHING ASSEMBLY SEQUENCE ANALYSIS TO PRODUCTION ENGINEERING STUDENTS
No full textAssembly sequence analysis represents the first step in assembly process design and plays a very important role in achieving optimal production time and cost, which is of great importance in large-scale and mass production. There are several different approaches to address this issue. As a rule, they start from the analysis of product components and their mutual liaisons (contacts, i.e., mates or joints), followed by generation of all feasible assembly sequences and, finally, selection of the optimal sequence according to appropriate criteria. However, mastering these tasks can be challenging for students who encounter them for the first time, and particularly when physical interaction with the product is limited. To facilitate and enhance students’ understanding of these methods by making the learning process more intuitive and easier, while also assisting educators in effective teaching, the Virtual Reality (VR) technology can be used. This paper presents a VR-based learning workflow for teaching methods for assembly sequence analysis to production engineering students. The workflow contains predefined tasks that students follow in VR to achieve the intended learning outcomes without the need for significant manual effort. For this workflow several VR environments are developed. In addition to these environments, the paper presents the analysis of the students’ experiences in their utilization
Occupational health and safety performance in a changing mining environment: Identification of critical factors
No full textAlthough the mining industry plays a pivotal role in driving economic growth, it is also known for being one of the most dangerous work environments due to the high rates of injuries. Companies in the mining industry are faced with the challenge of applying occupational health and safety (OHS) measures in a manner to advance worker safety, health, and overall welfare, but also to improve productivity, enhance product and/or service quality, foster work motivation, and elevate employee satisfaction, and finally to enhance the quality of life for individuals and society. There is a noticeable research gap in the literature that simultaneously addresses multiple safety and health factors and their combined influence on employee safety satisfaction and performance. Hence, this paper seeks to address the gap in the existing literature by conducting a comprehensive analysis of how work equipment and environmental factors, human behaviour factors related to OHSs, and organizational climate factors influence operators’ safety satisfaction and how these, in turn, affects overall performance stemming from occupational health and safety initiatives. After developing a measurement and structural model, based on the data collected from the mining machinery operators, adequate statistical tests were used for evaluation and the hypotheses testing. The results of this study provide insight into the relationship between mining machine operators’ opinions on examined safety factors and employees’ safety satisfaction, where the organizational climate factors and safety satisfaction demonstrated a positive impact on safety performance, consequently resulting in their improvement. The theoretical implications of this study lie in establishing a comprehensive theoretical framework integrating safety factors, such as work equipment and environmental factors, human behaviour, and organizational climate, and their influence on the safety satisfaction of mining machinery operators. The practical implication of this research contributes to determining the critical safety factors (organizational support, co-worker support, supervisor support, worker engagement, the training related to OHS, and management commitment) that exert the most significant impact on the satisfaction of mining machinery operators and safety performance. These findings serve as a roadmap for decision-makers within mining companies, facilitating the identification of priority areas for enhancing both worker satisfaction and safety performance
Editorial of the 12th Annual Conference of Society for Structural Integrity and Life (DIVK12) conference
No full textThe 12th Annual Conference of Society for Structural Integrity and Life (DIVK12), organized between 17th and 19th of November 2024, at the Faculty of Mechanical Engineering of the University of Belgrade, Serbia, gathered more than 160 participants (both in person and on-line) from all over the world, with more than 25 nationalities demonstrating the vitality and importance of this new event. This Special Issue gathers the 71 papers presented at the conference, including some keynote lectures and regular presentations. Awards for special contribution in certain topics were delivered attributed during the conference. The Organizing Committee of the DIVK12 conference sincerely thanks all contributing authors for playing a significant role in the overall success
of this event, with their exciting presentations. The members of the International Scientific Committee are also fully acknowledged for their support of the DIVK12 event. Special thanks to the Keynote Speakers for their dedication and knowledge and energy brought to this event. The Organizing Committee would also like to express their gratitude to the sponsors for their support without which the conference would be impossible to organize. Finally, chairmen sincerely thank the tireless efforts of Organizing Committee members, as well as Faculty of Mechanical Engineering, IMS institute and Innovation Center of Faculty of Mechanical Engineering staff
Thermodynamic Evaluation and Working Fluid Selection for a Heat Pump Integrated into a Hydropower Plant HVAC System: A Case Study from Serbia
No full textThis paper presents a thermodynamic analysis of two types of heat pumps integrated into the heating, ventilation, and air conditioning (HVAC) system
of the “Bajina Bašta” hydropower plant located in Serbia. The study aims to replace existing electric boilers with more energy-efficient solutions by utilising
renewable heat sources. A comparative evaluation of water source heat pump (WSHP) and air source heat pump (ASHP) configurations was conducted using a
custom-developed MATLAB model based on CoolProp data of working fluids. The analysis was supported by real data obtained through in situ measurements
of air and water temperatures at the selected location, ensuring accurate input parameters for the simulations. Five refrigerants (R-410A, R-407C, R-134a,
R-32, and R-1270) were used, and R-32 was selected as the optimal working fluid because of its high efficiency, moderate flammability, and low environmental
impact. The lowest coefficient of performance (COP) for the WSHP was 3.27 in January, while the seasonal coefficient of performance (SCOP) reached 3.36,
approximately 15.5 % higher than the ASHP counterpart (SCOP = 2.91). The study confirms that, upon analyzing the entire heating period, WSHP systems are
technically and environmentally superior to ASHPs in the locations studied. The proposed configuration, based on real measured data and obtained results, can
significantly improve energy efficiency and reduce internal electricity consumption in hydropower plants, thereby supporting the decarbonisation of large-scale
renewable energy facilities. While most previous studies have focused on improving energy efficiency in buildings, this work demonstrates the substantial yet
underexplored potential for efficiency improvements in the electricity production sector in Serbia. The study specifically examines hydropower plants in Serbia,
where heating and air conditioning systems built in the 1960s remain highly energy inefficient. By quantifying the benefits of integrating WSHP and ASHP
systems, the research highlights a pathway toward significantly enhancing the energy efficiency of hydropower infrastructures.451-03-66/2024-03/20010
Finite-Time Stability of a Class of Nonstationary Nonlinear Fractional Order Time Delay Systems: New Gronwall–Bellman Inequality Approach
No full textThis paper aims to analyze finite-time stability (FTS) for a class of nonstationary
nonlinear two-term fractional-order time-delay systems with α, β ∈ (0, 2). Using a new
type of generalized Gronwall–Bellman inequality, we derive new FTS stability criteria for
these systems in terms of the Mittag–Leffler function. We demonstrate that our theoretical
results are less conservative than those presented in the existing literature. Finally, we
provide three numerical examples using a modified Adams–Bashforth–Moulton algorithm
to illustrate the applicability of the proposed stability conditions.No. 451-03-137/2025-03/200105 from 04.02.202