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Integrated 3D DIC and PRTS analysis of long-termdegraded power plant steel
No full textThis paper presents an experimental investigation of the stress–strain behavior of Pipe RingTensileSpecimen (PRTS) made of X20CrMoV12-1 power plant steel after 200,000 hours of service. The objective was to determine the hoop-direction mechanical response of the material using a 3D Digital Image Correlation(3D DIC) method, evaluate dimensional changes with a 3D scanning system, and record temperature field evolution using a thermal imaging camera during tensile loading. A total of 12 PRTS samples were prepared from two pipe segments: the fracture zone segment I and a straight-pipe segment II. The results show that the fracture forces of segment I specimens are lower compared to II due to material degradation near the crack region and reduced wall thickness. Cross-sectional analysis revealed pronounced ductile behavior, with an average thickness reduction of 40.1% and width reduction of 23.5%. Experimental stress–strain curves provided characteristic mechanical values, including an engineering ultimate strength of 367.47 MPa(463.4MPa true value) and a 0.2% offset yield strength of 208 MPa. Comparison with the theoretical Ramberg–Osgood curve for X20CrMoV12-1 showed good agreement in the elastic region, with notable deviations in plastic domain caused by long-term service exposure. The findings demonstrate that the PRTS methodology combined with 3D DIC offers a reliable approach for assessing material degradation and remaining load-bearing capacity of power plant tubing in the hoop direction without flattening and without introducing additional residual stresses
The Methodology for the Design of Underactuated Adaptive Robotic Finger for Precision Grasping Tasks
No full textRobotic grippers are essential components in modern automation, enabling robots to interact with and manipulate objects in various tasks. While traditional designs excel in the manipulation of identical objects in structured environments, they often lack the adaptability required for handling various objects in unstructured settings. This limitation has led to increased focus on adaptive solutions, with underactuated robotic hands emerging as a promising alternative that combines dexterity, mechanical simplicity, and cost efficiency. Unlike fully actuated hands, which are complex and expensive, underactuated designs use fewer actuators than degrees of freedom and rely on passive elements such as springs and mechanical limits for adaptation to object’s shape. This paper presents the design of a two-phalanges underactuated robotic finger actuated by a four-bar linkage and gear mechanism. The finger is intended for robotic hand primarily used for precision grasping tasks. A methodology for calculating optimal linkage dimensions and mechanism for adaptability are also described, as well as the method for the analysis of grasping force during precision grasping.under the contract No. 451-03-137/2025-03/20010
Identification of crack initiation cause in slewing platform horizontal plate of the excavator SchRs630
No full textA crack occurred on a lower horizontal plate of a slewing platform of bucket wheel excavator (BWE)SchRs630. Numerical calculation model of pylons, slewing platform and undercarriage was formed. Calculationswere performed using finite element method (FEM) for different load cases in order to identify load that causedthecrack. All the loadings repeat in cycles, particularly loading with inertial forces caused by bucket wheel boomandcounterweight boom masses while breaking slew drive, and also a workload causing bending of pylons. All theseloads cause (not high) stress concentration in this spot and could be the cause of a fatigue crack. To completethewhole picture of the structure behaviour dynamic analysis was performed. Simple redesign solution of this part ofthe structure was proposed.contracts no. 451-03-137/2025-03/ 200105 and 451-03-137/2025-03/ 200213 from 04.02.202
Evaluation of Aerodynamic Coefficients of Supercritical Airfoil NASA sc(2) 0712: A Comparative Study of 2D and 3D Flow Models with Experimental Validations
No full textThis study presents a comparative numerical analysis of 2D and 3D compressible, turbulent flows around the supercritical airfoil NASA sc(2) 0712 at Mach number M = 0.5 using the finite volume method implemented in ANSYS Fluent, focusing on the estimation of drag coefficients in relation to existing experimental data. In addition, different types of computational grids and turbulence models are tested. The investigation aims to highlight the discrepancies observed between the two modeling approaches and their implications for aerodynamic performance predictions. Through rigorous numerical simulations and validation against experimental results, we demonstrate that 2D models often yield overestimated drag values due to simplified flow assumptions. In contrast, 3D simulations provide a more accurate representation of fluid behavior, resulting in closer alignment with experimental findings. By performing spatial computations of turbulent flow around a supercritical airfoil, it is possible to reduce the relative error of drag coefficients by less than 10%
The effect of blade turning angle on rotation improvement of a small horizontal axis wind turbine
No full textOptimization of wind turbine aerodynamic performances implies solving the problem in the domains such as airfoil selection, blade rotation angle, chord optimization, number of blades, appropriate tip speed ratio, etc. The current paper studies the effect of blade rotation angle (β = 5, 7, 10°) on power coefficient (CP), torque (T) and mechanical power (PM) in a small horizontal axis wind turbine (HAWT). The analysis involves two models of blades (V and) of the airfoil
class SD 7003. The first part of the paper employs numerical analysis, that is, Ansys CFX and Ansys Fluent software packages, to define wind turbine characteristics. The obtained results indicate that as the rotation angle (β) increases the CP increases within an appropriate range of tip speed ratio (λ) change. The second part describes experimental investigation conducted on considered HAWT to define the values of T and PM for studied blade rotation angles and comparison with the values obtained from Ansys. Existing differences in values are a consequence of the design of the HAWT, that is, the influence of the mass moment of inertia of the rotor and generator as well as the placement of the generator. Experimental setup and methodology allow for investigating the effect of different blade models, rotor and generator structure on wind turbine torque and mechanical power output characteristic
A Short Discussion on the Circulation in the Turbulent Swirling Flow in the Axial Fan Jet
No full textIn this paper is analyzed distribution of the circulation in the turbulent swirling flow in
the axial fan jet. Experimental results are obtained by use of the three component LDV system.
Development of the circulation profile in the central zone, up to r = R obeys hierarchical
distribution downstream, while this is not a case in the outer zones. Positions of the circulation
extreme values are also discussed, as well as its gradients.Ministry of Science, Technological Development and Innovation of the Republic of Serbian, for scientific research work of teaching staff at accredited higher education institutions in 2025, no. 451-03-137/2025- 03/200105
Extended abstract, M34
https://sdm.org.rs/congress/2025/docs/proceedings.pd
Speed Control of a Rotary Servo-Base Unit: Lyapunov and MIT Rule Approaches
No full textThis paper presents a comparative study of two speed control techniques for a rotary servo-base unit using Lyapunov-based adaptive control and the MIT rule technique. The primary objective is to achieve precise and stable speed control and to analyze the influence of adaptation gain on the system performance. A mathematical model of the rotary system is analyzed, followed by the development of adaptive controllers based on the Lyapunov stability theory and the MIT rule. Choosing a suitable reference model is examined, and parameter adaptation laws are designed to optimize system performance. The impact of different adaptation gains on system response is evaluated through simulations in MATLAB/Simulink. Figures illustrating the evolution of adaptation parameters over time, as well as system response, are provided. Various performance criteria, settling time, overshoot, and different objective functions are used to compare the control approaches. The results highlight the advantages and limitations of each method. Recommendations for tuning adaptation parameters are provided to improve overall system performance.under contract 451-03-137/2025-03/200105, from date 04.02.202
WHOLE-BODY VIBRATION MEASUREMENT AT THE MINING MACHINERY OPERATOR’S WORKPLACE IN SMES
No full textIncreased mechanization in mining results in a larger number of workers being
exposed to longer durations of whole-body vibration (WBV). Occupational exposure to vibration is associated with an increased risk of musculoskeletal pain in the back, neck, hands, shoulders, and hips; the development of peripheral and cardiovascular disorders and gastrointestinal problems; and it may even increase the risk of developing certain cancers. In that aim, in this survey, whole-body vibration exposure levels were measured during the shift at 22 mining machinery operators’ workplaces in 3 surface mining. A triaxial accelerometer V31 was used to measure vibration exposure. Measurements were conducted in accordance with the procedures described in applicable standards in the field. The results indicate that the observed workplaces exceeded the action limit values according to the EU Directive 2002/44/EC, as well as the lower limit values of health risks according to the ISO 2631 standard. The lower limit value of health risk according to the ISO 2631 standard was exceeded at 50% of machines. The action value of WBV according to the EU Directive 2002/44/EC was exceeded in 36% of machines. The dominant vibrations were indicated along the X and Y axes. Operators on bulldozers and loaders are most often exposed to the harmful influence of WB vibrations. Research indicates that there is a risk of harmful impact of WBV that needs to be prevented and highlights the need for further research to identify the most critical risk factors and develop effective prevention and protection strategies for mining machinery operators’workplace risks caused by vibrations
THE INFLUENCE OF CRYOGENIC TREATMENT ON THE HARDNESS OF ROLLING BEARINGS’ BALLS
No full textThis study examines the effects of Deep Cryogenic Treatment (DCT) applied after conventional quenching (Q) and tempering (T) on the hardness of rolling bearing balls—a geometric shape that has been significantly less studied compared to other sample forms, such as plates or cylindrical specimens. The primary objective is to determine whether DCT, when applied to commercially available rolling bearing balls (supplied by the manufacturer after completing Q and T), negatively impacts their performance or enhances it. The bearing balls analyzed in this study were from bearing types 6306, 6308, and 6310, manufactured from 100Cr6/AISI 52100 steel. The DCT process involved a controlled cooling rate of 1.5°C per minute, a soaking temperature of -160°C, and a soaking duration of 24 hours. Experimental results revealed that the hardness of the bearing balls remained largely unchanged, with a percentage variation of less than 1% across all tested bearings. Although previous studies on the same bearing material have suggested that DCT can improve hardness, our findings indicate that this effect may not be as significant when DCT is applied to bearing balls after quenching and tempering under the specific conditions of this study. Future research will explore the influence of DCT on additional factors such as dimensional stability, surface roughness, and residual stress to gain a more comprehensive understanding of its overall impact on bearing performance
VAT PHOTOPOLYMERIZATION RISK ASSESSMENT USING THE KINNEY METHOD
No full textAdditive manufacturing technologies are becoming increasingly prevalent across industries, educational institutions, and even households. Their primary application lies in the production of prototypes and components with intricate geometries. However, despite their widespread adoption, the potential risks these technologies pose to occupational safety and human health remain insufficiently explored. This paper presents a risk assessment of one of the most widely used additive manufacturing processes—Vat Photopolymerization. The evaluation was conducted using the Kinney risk assessment method to identify potential hazards associated with the technology. Based on the findings, appropriate safety measures were proposed to mitigate risks and enhance workplace safety