Search Results (11)

Although asbestos has been banned in the European Union since 2005, asbestos-containing materials, such as brake pads and clutch linings, may still occur in waste streams due to the long service life of vehicles, legacy equipment, and international trade in spare parts. The persistence of these materials raises environmental and occupational health concerns, particularly in waste management systems. This study aims to assess the presence, temporal trends, and sectoral distribution of asbestos-containing friction materials in the Hungarian waste management system two decades after the EU ban, and to evaluate the associated regulatory and occupational risk implications. The analysis is based on national hazardous waste datasets classified under EWC code 16 01 11* (asbestos-containing brake pads), with a specific focus on this waste category rather than on the full range of asbestos-related waste streams recorded in the national database. The results indicate that asbestos-containing friction materials are still present in the waste stream, with measurable quantities recorded annually. Despite regulatory control, identification challenges and potential misclassification may contribute to underreporting. The continued occurrence of asbestos-containing materials highlights the persistence of legacy hazardous materials within circular economy systems. Strengthened monitoring, improved identification protocols, and enhanced occupational safety measures are necessary to mitigate residual exposure risks. The findings underline that asbestos is not merely a historical issue but remains a contemporary environmental and public health challenge. Full article

Runway friction is a critical factor in aircraft safety, affecting braking performance during landing and take-off. This study evaluates friction measurement variability and runway life-cycle dynamics at four typical Australian airports, using GripTester data from calibration strips and operational runways. The results show that friction measurements are influenced by seasonal effects, random errors, and testing equipment tire wear, with greater variability at lower speed (65 km/h) than at higher speed (95 km/h). Analysis of runway friction decay indicates that friction reduction rates are higher in touchdown zones and decelerating rate gradually decrease as friction declines, while regular rubber removal significantly restores friction, sometimes exceeding post-construction levels. Current internationally recommended friction testing intervals may not adequately ensure safety, with a sufficient probability of friction dropping below maintenance planning levels between tests. Based on observed reduction rates, updated intervals of approximately 3000 to 4000 landings are proposed to achieve 90% confidence in maintaining safe friction levels. The findings provide practical guidance for friction management and maintenance scheduling as part of an optimized airport pavement management system. Full article

The continuous worsening of the natural surroundings requires accelerating the exploration of green energy technology. Utilising ambient vibration to power electronic equipment constitutes an important measure to address the power crisis. Vibration power is widely dispersed in the surroundings, such as mechanical vibration, acoustic vibration, wind vibration, and water wave vibration. Collecting vibration energy is one of the research hotspots in the field of energy. Meanwhile, it is also an important way to solve the energy crisis. This paper illustrates the working principles and recent research progress of five known methods of vibrational energy harvesting, namely, electromagnetic, piezoelectric, friction electric, electrostatic, and magnetostrictive vibrational energy harvesters. The strengths and weaknesses of each method are summarised. At the end of the article, the future trends of micro-nano vibrational energy collectors are envisioned. Full article

This contribution underscores the importance of selecting an appropriate interphase momentum transfer model for accurately predicting the distribution of the solid phase in a full-scale circulating fluidized bed (CFB) riser equipped with a smooth C-type exit. It also explores other critical factors such as domain configuration, grid size, the scope of time averaging, and turbulence modulation. The flow in a cold-CFB riser is simulated using the Eulerian–Eulerian two-fluid model within a commercial CFD package. Particle interactions in the rapid-flow regime are determined utilizing the kinetic theory of granular flow while enduring particle contacts are accounted for by incorporating frictional stresses. The turbulent dynamics of the continuous phase are described using two-equation turbulence models with additional modulation terms. The three-dimensional computational domain replicates an actual CFB riser geometry where experimental measurements are available for particulate phase axial and radial solid concentration. The simulation results reveal that the choice of drag model correlation significantly impacts both axial and radial solid distribution. Notably, the energy-minimization multi-scale drag model accurately depicts the dense solid region at the bottom and core–annular flow structure in the upper part. The solid-phase fluidization is overestimated in the lower riser section when a 2D domain is utilized. Neglecting turbulence modulation terms in the k-$\omega$ SST model results in nearly flat solid volume fraction radial profiles in the analyzed upper sections of the riser, resembling those obtained with the k-$ϵ$ model. Full article

Road dust is a mixture of fine and coarse particles released into the air due to an external force, such as tire–ground friction or wind, which is harmful to human health when inhaled. Continuous dust emission from the road surfaces is detrimental to the road itself and the road users. Due to this, multiple dust monitoring and control techniques are currently adopted in the world. The current dust monitoring methods require expensive equipment and expertise. This study introduces a novel pragmatic and robust approach to quantifying traffic-induced road dust using a deep learning method called semantic segmentation. Based on the authors’ previous works, the best-performing semantic segmentation machine learning models were selected and used to identify dust in an image pixel-wise. The total number of dust pixels was then correlated with real-world dust measurements obtained from a research-grade dust monitor. Our method shows that semantic segmentation can be adopted to quantify traffic-induced dust reasonably. Over 90% of the predictions from both correlations fall in true positive quadrant, indicating that when dust concentrations are below the threshold, the segmentation can accurately predict them. The results were validated and extended for real-time application. Our code implementation is publicly available. Full article

To assess the medium-term performance of porous asphalt pavement during service and its influence on tire/pavement noise level, a seven-year continuous observation and data analysis study was conducted. Key performance indicators were measured and calculated by using automated pavement technology testing equipment. The noise levels were tested by using the on-board sound intensity (OBSI) method on three types of porous asphalt pavements (PUC-10, PAC-13, and PUC-10 + PAC-13) and one dense thin layer course (DTC) for comparison. The findings indicated that the Damage Rate (DR) and Surface Friction Coefficient (SFC) of porous asphalt pavements diminished greatly over time, while the International Roughness Index (IRI) and Rut Depth (RD) remained relatively stable. The two-layer porous asphalt pavement showed the largest noise reduction over the medium-term. Compared to DTC, the OBSI noise levels of these structures were lower by 2.09 dB, 1.53 dB, and 2.88 dB, respectively. The OBSI was found to be closely correlated with the SFC, IRI, test speed, lane, and pavement type. The RD had a notable effect on the OBSI in PUC-10 pavements. In PUC-10 + PAC-13 pavements, a significant linear relationship was observed between the OBSI and SFC. This is mainly because of the polishing of the coarse aggregates, which leads to micro-texture reduction, high frequency noise increase, and SFC decrease. This study makes a valuable contribution to understanding the laws of porous asphalt pavement performance changes and the relationship between tire/pavement noise and pavement characteristics. Full article

Ceramics are considered to be candidate materials for galvanising pot bearing materials due to their excellent corrosion resistance in many molten metals. Galvanising pot roll bearings must have excellent wear resistance, and, therefore, it is important to understand the wear behaviour of prospective bearing materials. This study investigates the friction- and wear-resistant properties of select ceramics, namely, pure hBN, BN M26, AlN-BN, Macor, 3YSZ, Al₂O₃ and Si₃N₄. The ceramics were tested at different sliding speeds using a pin-on-disc device equipped with SiC pins. The lowest coefficient of friction (COF) achieved was below 0.1, and it was measured for pure hBN at a 3.14 m/min sliding speed. However, a wear scar analysis showed that the BN grades suffered from severe wear. The highest wear rate was obtained for BN M26 at a 9.42 m/min sliding speed and was equal to 17.1 × 10⁻⁶ mm³ N⁻¹ m⁻¹. It was shown that the wear coefficient of the tested ceramics varied exponentially with hardness. The lowest wear was observed on the 3YSZ, Al₂O₃ and Si₃N₄ ceramics, which showed no volume loss, and, for this reason, they can be potentially used as bearing materials in continuous galvanising lines. Full article

Hydraulic support is important equipment in the fully mechanized mining face, and the control performance of the hydraulic support multi-cylinder system directly affects the smooth progress of coal mining process, which is the basis for the continuous advancement of the coal face. However, the friction force of the hydraulic support in the process of pulling the frame is complex due to the underground environmental load. Moreover, the parameters of the moving cylinder are uncertain, and the state of the system cannot be fully measured, which increases the difficulty of control. A proportional-integral-derivative controller is usually used in electro-hydraulic closed-loop control systems because of its computational complexity, but its robustness is poorly adapted to variable load conditions in the coal mine. Therefore, a robust output feedback position controller is proposed in this paper to improve control accuracy and system robustness with only position signal. The multi-cylinder system of hydraulic support is modeled as a standard type, and then a high-order differentiator is proposed to estimate the immeasurable system states using the output position signal. A neural network compensator is applied to estimate and compensate for the external disturbance of the moving cylinder. Furthermore, the parameters of the ZY3200/08/18D hydraulic support are adopted to analyze the effectiveness of the designed controller in simulations. Finally, a real-time control system of hydraulic support is built, and the experimental results show that the novel robust output feedback controller has improved by 47.2% and 30.6% in tracking accuracy compared to PI controller. Full article

Brake particle emissions number (PN) and mass (PM) of a light-duty hybrid-electric vehicle have been assessed under realistic driving patterns on a chassis dynamometer. Therefore, the front-right disc brake was enclosed in a specifically designed casing featuring controlled high scavenging air ventilation. The WLTC cycle was chosen for most measurements. Different scavenging flow rates have been tested assessing their influence on the measured particles as well as on the temperature of the braking friction partners. Particle transport efficiencies have been assessed revealing scavenging flow rates with losses below 10%. During the performed cycle, most brake particle emissions occurred during braking. There were also isolated emission peaks during periods with no brakes in use, especially during vehicle accelerations. Sequential WLTC cycles showed a continuous decrease in the measured PN and PM emissions; however, size-number and size-mass distributions have been very similar. The measured PN emission factors (>23 nm) at the right front wheel over the WLTC cycle lie at 5.0 × 10¹⁰ 1/km, whereas the PM emission factor lies at 3.71 mg/km for PM < 12 µm and 1.58 mg/km for PM < 2.5 µm. These values need to roughly triple in order to obtain the brake particle emission of all four brakes and wheels of the entire vehicle. Thus, the brake PN emissions factors have been in the same order of magnitude as the tailpipe PN of a Euro 6 light-duty vehicle equipped with a particle filter. Finally, differences between brake particle emissions in hybrid and all-electric operating modes have been assessed by a series of specific measurements, demonstrating the potential of all-electric vehicle operation in reducing brake particles by a factor of two. Full article

This study concerns the development and testing of three types of Anti-lock Brake Systems (ABS): a standard on-off wheel’s acceleration control; a wheel’s longitudinal slip controller based on a discrete Proportional-Integral-Derivative (PID) control; and a novel type of ABS that involves controlling the wheel’s speed through a discrete PID. This work was developed inside a wider project that will lead to the implementation of stability control systems in a prototype car. For this reason, the typologies of ABS must not require extra sensors compared to those in standard vehicles: Inertial Measurement Unit (IMU) and 4-wheel speed sensors. Furthermore, they must be easily integrated with other controls and electronic components in terms of sampling time and values. The standard ABS seems more appropriate than the others two because it uses only parameters defined by sensors and it has a simple architecture that does not have the problem of computational time. However, in recent years, cars have been equipped with Electro-Hydraulic-Braking (EHB) units that improve the performance of the system controls. In fact, it is possible to use a control that allows actuators to follow a continuous target and smooth out pressure actions. Even if the longitudinal Slip Controller has a simple architecture and uses a PID control, it is limited to using quantities estimated instead of measured: the tires’ friction coefficient, the tires’ longitudinal stiffness, and the car’s speed. Therefore, the use of a Wheel Speed Controller is the right compromise to link the advantages of both controllers by following the braking pressure continuously and not needing to know the condition and properties of the tires. The results of tests carried out in a Hardware-In-the-Loop (HiL) system are showed and involved a complex vehicle model implemented in real-time. Full article

The tribological behavior of electrical contacts, especially separable type electrical connectors at low contact loads, are considered. The reliability of these connectors has been a major concern due to the fretting phenomenon that can lead to an unacceptable increase in contact resistance. This study analyzes various aspects of the fretting mechanism from a tribological perspective where friction and wear are the primary cause of degradation in electrical components. With the use of precise tribological equipment (high data acquisition rate of 5000 Hz), the electrical contact resistance and coefficient of friction at the contact interface are measured. The measurements were made in-situ for a simulated fretting environment under various constant loading conditions. It was observed that low contact loads (1 N) and low fretting frequency (1 Hz) leads to a high degree of fluctuation in the coefficient of friction. However, for the same conditions, the lowest wear rate and electrical contact resistance were observed. The reason behind this could be due to the lack of continuous electrical contact and a high degree of fretting frequency under low contact loads, ultimately leading to extended periods of an open circuit. Experimental analysis indicates the existence of an optimum loading condition at which the fretting wear effect is at its minimum. Detailed analysis of post fretting surface roughness, coating wear, and wear debris is conducted, as well as transfer film formations to explain the mechanism of fretting observed. Full article