Maintenance, Reliability and Condition Monitoring
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Structure design and sensitivity analysis of flexible ultrasonic transducer array
Full text linkTo investigate the influence of element parameters on the performance and acoustic field of flexible ultrasonic transducer arrays, this study employs finite element multiphysics simulation software to analyze various parameters of flexible ultrasonic transducers within a multiphysics coupled field. The analysis begins with simulating the width and thickness of piezoelectric materials in a single-element ultrasonic transducer structure. Simulation results indicate that the electromechanical coupling coefficient of the ultrasonic transducer exhibits a quasi-sinusoidal relationship with width. When the piezoelectric material width is 1.8 mm, the electromechanical coupling coefficient reaches its maximum at a thickness of 0.4 mm. Subsequently, simulations were conducted on various parameters of the flexible ultrasonic transducer array. Key investigations included the effects of piezoelectric unit count, inter-unit spacing, and frequency on the ultrasonic focusing performance of linear phased array transducers. Findings indicate that the focusing capability of flexible ultrasonic transducer arrays improves with reduced spacing and increased unit count. However, due to varying practical application requirements and manufacturing precision constraints, array parameters should be selected by comprehensively considering real-world factors. Overall, this study employs multiphysics coupling simulation to visually demonstrate how array element parameters influence the performance of flexible ultrasonic transducers. It provides valuable reference for advancing flexible ultrasonic technology from laboratory research toward commercial application
Study on the compaction and dynamic properties of loess enhanced by waste tyre rubber particles
Full text linkThis study investigates the compaction and dynamic properties of rubber particle-loess from Inner Mongolia through laboratory tests, including compaction tests and dynamic triaxial tests. Four rubber particle sizes (10 mesh, 20 mesh, 40 mesh, and 100 mesh) and four contents (5 %, 10 %, 15 %, and 20 % by volume) were tested under varying conditions: confining pressures of 50 kPa, 100 kPa, and 200 kPa, and freeze-thaw cycles of 0, 1, 3, 6, and 9. The tests aimed to simulate environmental conditions relevant to infrastructure in Inner Mongolia's loess regions. Results revel that adding 5 % 40-mesh rubber particles maximized dynamic shear modulus, damping ratio, and compactness. The dynamic shear modulus exhibited strain-softening behavior, which decreased with increasing dynamic strain, rubber content, and freeze-thaw cycles, but increased with confining pressure. The damping ratio showed a non-linear relationship with moisture content, showing a minimum at optimum moisture and increasing with freeze-thaw cycles while decreasing with confining pressure. Notably, the damping ratio of rubber particle-loess consistently exceeded that of plain soil. These results highlight the potential of waste tire rubber particles as an eco-friendly material to enhance loess engineering properties, particularly in cold regions with significant freeze-thaw effects. The study provides a theoretical basis for improving loess stability and seismic performance in geotechnical applications
Field evaluation of the geotechnical behavior of lime-ground cushions in the Republic of Tajikistan
Full text linkThe article presents the methodology for conducting field tests of lime-soil cushions to examine the technology of their construction, gain strength, their operation under rigid stamps, and the characteristics of stress-strain state development. The results of field studies showed that the lime-soil mixture can be used as a structural material in the preparation of bases on loess- loess soils in the conditions of the Republic of Tajikistan. Field tests showed that the lime-soil mixture achieved a dry density of 1.53-1.56 t/m3, while the deformation modulus increased by 5-10 times compared to natural loess soils
Structural damage detection by progressive continuous wavelet transform and singular value decomposition of noisy mode shapes
Full text linkFor decades, damage identification based on structural mode shapes has been a popular research topic. While mode shapes provide valuable spatial structural information, the sensitivity to localized damage remains limited. In contrast, modal curvature exhibits high sensitivity to local damage, enabling precise damage localization. However, its susceptibility to environmental noise poses a significant limitation. To this end, a novel damage identification method is proposed by integrating continuous wavelet transform (CWT) and singular value decomposition (SVD). First, the CWT is applied to structural mode shapes for generating continuous wavelet coefficients. Subsequently, the SVD is performed on these coefficients, yielding new damage indicator termed as the singular image of continuous wavelet coefficients (SICWC). The SICWC enhances damage sensitivity and localization accuracy by suppressing noise-induced global trends in structural mode shapes. The effectiveness of proposed method is validated through numerical simulations of a cantilever beam under noisy conditions, as well as experimental detection of a cracked beam using mode shapes acquired via a scanning laser vibrometer. The results demonstrate that SICWC effectively mitigates the limitations of traditional damage detection methods based on mode shape and curvature
Permeability test of geotextile-soil system under different sand filling heights
Full text linkGeotube dams are constructed by stacking geotubes, which are non-homogeneous structures composed of geotextiles and filled sand. Therefore, studying the permeability characteristics of the geotextile-soil system is of great significance for seepage analysis in geotube dams. While the permeability characteristics of geotextiles and filled sand have been extensively studied individually, there has been relatively little research on the permeability characteristics of the geotextile-soil system formed by the combination of geotextiles and soil. In this study, a self-designed permeameter was used to investigate the permeability characteristics of the geotextile-soil system under different sand filling heights. The test results indicate that the permeability coefficient of the geotextile-soil system decreases continuously with the increase in permeation time and eventually stabilizes. The permeability coefficient of the geotextile-soil system increases with the sand-filling height and finally approaches but remains slightly smaller than that of pure sand with the same gradation. The influence of geotextiles on the permeability of the geotextile-soil system is significant within the range of 0 to 5 cm. Additionally, the water permeability of geotextiles affects the permeability performance of the geotextile-soil system. Specifically, a larger porosity corresponds to higher water permeability, and a greater permeability coefficient of the geotextile leads to a higher permeability coefficient of the geotextile-soil system
Modern strengthening techniques for enhancing the load-carrying capacity of in-service road bridges in Uzbekistan
Full text linkThe sustained growth of traffic intensity and axle loads in Uzbekistan has accelerated the deterioration of in-service road bridges, making cost-effective strengthening a national priority. This paper presents a structured review and comparative assessment of strengthening approaches grouped into: (i) traditional cross-section enlargement and substructure rehabilitation, (ii) structural scheme optimization and dead-load reduction (including external prestressing and span continuity), and (iii) advanced solutions based on carbon-fiber-reinforced polymers (CFRP). A worked example for a typical reinforced-concrete girder span demonstrates the compensation of a deficient bending moment of ΔM= 70 kN·m and indicates an ~18-25 % increase in load-carrying capacity after strengthening. The paper further synthesizes implementation considerations for arid-continental climates, including surface preparation, adhesion control, protective coatings, and staged load testing. Drawing on regional practice, CFRP systems are highlighted as offering high strength-to-weight benefits, installation speed, and minimal traffic disruption; reported gains for flexural elements typically range from 25 % to 45 %, subject to detailing and quality assurance. The results support integrating CFRP-based measures and complementary dead-load optimization into bridge rehabilitation programs in Uzbekistan, with recommendations for monitoring intervals (6-12 months) and future durability studies on adhesives and UV/moisture protection. Overall, the study consolidates methods and provides quantitatively grounded guidance for extending service life under contemporary traffic demands
Enhancing the Carrying capacity of complex mountain railway sections through the optimization of train mass standards
Full text linkIt is known that the current train mass standards for railway sections often do not allow locomotives to fully utilize their tractive power. This limits the throughput and Carrying capacity of the railway sections. This article examines the issues of increasing the carrying capacity of freight trains by optimizing train mass standards, using the “Angren-Pop” railway section, which has the most complex profile in “Uzbekistan Railways” JSC, as an example. Updated optimal train mass standards have been proposed for freight trains operating on the “Angren-Pop” railway section, and experimental tests have been carried out based on these standards, followed by their implementation in practice. Based on traction calculations, the interstation travel times of trains for the updated mass standards have been determined. Methods for effectively increasing the transport capacity of the section have been recommended by implementing measures such as increasing the train mass standards and interstation running speeds of freight trains, as well as systematically organizing the use of electric locomotives with high tractive power
Experimental thermal fatigue crack on brake disc of heavy vehicle
Full text linkBrake system reliability is critical for the safety and performance of heavy vehicles, including semi-trailers, passenger buses, and industrial transport units. This study investigates the thermal fatigue failure mechanisms in brake discs (BDs), which are subjected to extreme operational conditions. The primary motivation is to enhance brake disc durability and reduce the risk of catastrophic failures by understanding the interplay between material properties, thermal stress, and fatigue resistance. A comprehensive experimental approach was employed, including visual inspections, chemical composition analysis, metallurgical structure examination, hardness testing, and tensile strength evaluation. The study compares brake discs that have undergone extensive service with those in an undamaged state to identify critical degradation patterns. The results indicate that temperature fluctuations and cyclic thermal stresses induce crack formation and propagation, with rough graphite inclusions significantly reducing fatigue strength. Furthermore, deviations in silicon and carbon content were found to impact material integrity, contributing to premature failure. The findings of this research provide actionable insights for optimizing brake disc design, material composition, and manufacturing processes. By modifying graphite distribution, refining alloy compositions, and improving thermal resistance, future brake systems can achieve greater durability and reliability. These advancements will directly enhance braking efficiency, reduce maintenance costs, and improve overall vehicle safety
Potential of handheld laser beam welding
Full text linkSince 2023 at the latest, handheld laser beam welding systems (HLBW) gained interest by many companies. This is mainly due to two factors. Firstly, the cost of such a system has fallen considerably in recent years. Secondly, there is an economic pressure for the manufactures of welded products, partly due to the shortage of skilled workers. This publication addresses various aspects of HLBW, in particular the current state of the art and the potential applications. The higher throughput, less straightening work due to the lower heat input, and the use of less experienced personnel has to be mentioned here. However, welders still need to be qualified, especially to get informed about the hazards of laser radiation. In addition to welding, many systems for HLBW also include a cleaning function, some even a cutting function. The risks to be considered for both last mentioned are significantly greater, since on one hand, a touchdown or contact control is often omitted and on the other, the laser beam is conditioned for a longer working distance. For HLBW, the requirements of the process must be taken into account during the design phase already. This continues with edge preparation, e.g. pre-weld cleaning. HLBW is a supplement to traditional arc welding processes. Arc processes will be still used in the future as well, e.g. for small, complex geometries or in terms of accessibility. However, for longer welds, e.g. 1.5 m long 2 mm thick stainless steel sheets, HLBW sets currently the standard, especially with regard to the welding speed for manual welding
