Journal of Mechanical Engineering, Automation and Control Systems
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Improving the quality of cast blanks by applying force to the solidifying metal
Get PDFIn the course of the research, the authors studied the formation of structures of cast blanks on various alloys, depending on the conditions of metal crystallization, including under the influence of vibration. An analysis of the structures of the control samples (blanks) confirmed that solidification under normal conditions occurs mainly according to the sequential crystallization scheme, as evidenced by the width of the structural zones in them. The external vibration effect on solidifying alloys leads to a significant change in the conditions of their crystallization, in particular, to a significant grinding of the macrostructure of the workpieces and a change in the size of the structural zones, which indicates a volume-sequential scheme of their crystallization. It is established that vibration increases the physico-mechanical properties of cast metal and significantly reduces their anisotropy over the section of the workpieces
Study on the impact of wheel roundness defects on axle fatigue damage
No full textWith the continuous increase in the operating mileage of China’s high-speed railway network, wheel out-of-roundness has become increasingly common in electric multiple unit (EMU) vehicles. Wheel out-of-roundness directly increases the vibration level of the axle, affects various vehicle components, and in severe cases, may lead to fatigue fracture of the axle – a key load-bearing component – thereby causing major safety incidents. To investigate the influence of wheel out-of-roundness on axle dynamic stress and to evaluate the fatigue strength of the axle under such conditions, this study analyzes the effects of different wheel flat lengths, polygon orders and depths, as well as various operating speeds on the dynamic stress of EMU axles. Based on numerical simulation results, the fatigue damage of the axle under wheel out-of-round conditions and the impact of wheel polygonal wear over one development cycle are calculated. The findings show that within a single re-profiling cycle, wheel flats shorter than 50 mm have a negligible effect on axle fatigue damage. Furthermore, a reference limit for polygonal wear depth is proposed, providing theoretical guidance for wheel maintenance and safety assessment of EMU vehicles
Modal and optimization analysis of a 12-degree-of-freedom engine mount system considering engine elasticity
Get PDFThe multi-degree-of-freedom engine mount system presents a coupling issue that significantly impacting its vibration isolation performance. Although the optimization theories for decoupling 6-degree-of-freedom (6-DOF) and 12-degree-of-freedom (12-DOF) engine mount systems are relatively well-developed, previous studies have predominantly focused on engine response and often overlook the impact of car body vibrations. To address this gap, this article conducts an in-depth investigation into how the elasticity of the car body affects the vibration isolation performance of the engine mount system. Initially, the dynamics of the engine mount system are modeled with 6 degrees of freedom, incorporating an elastic base with 9 and 12 degrees of freedom, respectively. The study then analyzes how body elasticity influences the natural frequencies and modal shapes of the engine mount system. Subsequently, the sensitivity of the engine mount system is assessed using Isight analysis to evaluate the three directional stiffnesses of the mount. Finally, the decoupling optimization of the 12-degree-of-freedom engine mount system is performed using the NLPQL (Sequential Quadratic Programming) method. The findings indicate that: (1) considering the car body’s influence directly affects the natural characteristics and decoupling efficiency of the engine mount system; (2) body elasticity in the Z-direction has the greatest impact on the system’s vertical natural frequency; and (3) the NLPQL method effectively enhances the decoupling rate of the engine mount system
Permeability test of geotextile-soil system under different sand filling heights
Get PDFGeotube 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
Stress-strain state of a welded high-strength steel pipeline in the presence of surface defects
Get PDFThe construction of main pipelines is now predominantly carried out using high-strength steels. This makes it possible to increase pipeline capacity while maintaining the existing pipe geometry. However, the issue of ensuring the strength of such pipelines in the presence of surface defects is still relevant. This is especially true for pipeline segments that are located in hard-to-reach places, and therefore, it is difficult to repair and restore. At the same time, the introduction of high-strength steels involves a complex system of material alloying and special thermo-mechanical strengthening technologies. As a result, special structures of increased strength can be produced, but they are sensitive to reheating, in particular when welding technologies are used. This is due to the formation of a special zone of thermal deformation influence in the vicinity of the weld. Material properties of the pipes differ from their original characteristics. The stress-strain state is formed, which also affects the strength of the welded pipeline. The nature of the stress-strain state of welded joints of pipes made of high-strength materials differs from the well-studied stress distributions in pipelines built in the past sixty-eighty years of the past century. In particular, several localized maxima of stresses can be located not only on the weld axis but also in the zone of thermal deformation influence. Therefore, it is important to evaluate the effect of weld stresses in welded joints of high-strength steel pipes on the strength of the pipeline in the presence of surface defects. Since the defect may be located at an arbitrary distance from the weld axis, the predicted strength of the welded pipeline segment can vary significantly
Erratum: Vibrodiagnostics and dynamic operation of reinforced concrete sleepers under the influence of moving load
Get PDFA new self-adaptive anti-galloping device in suppressing conductor galloping in transmission lines
Get PDFConductor galloping is a serious threat to transmission line integrity, inducing excessive conductor tension that may lead to catastrophic failures including conductor breakage and tower collapse. This study proposes a novel self-adaptive anti-galloping device (SAGD) to mitigate galloping amplitudes and reduce associated risks. In this paper a novel self-adaptive anti-galloping device (SAGD) to mitigate galloping amplitudes and reduce associated risks was proposed. The structural design scheme of the device is provided, and its operation sequence was verified through static loading experiments. Conductor free-falling experiments validated the SAGD's vibration control performance, with test results demonstrating its practical applicability for transmission line protection. A finite element model for the conductor-SAGD system was developed, enabling numerical simulation of galloping displacement time history and analysis of endpoint support reaction dynamics. The device's galloping suppression effectiveness is systematically evaluated under varying stroke lengths and threshold conditions
Maintenance, repair, and overhaul of robotic systems
Get PDFThis paper not only explores the fundamental aspects of but also brings new ideas for maintenance, repair, and overhaul (MRO) operations of robotic systems (RS). This synthesis is based on the limited scholarly research in this area and on information gathered from comprehensive web searches and analysis of corporate websites so that the results reflect the current views of RS developers and operators. The paper describes several crucial areas concerning RS MRO: maintenance of robotic systems, challenges and best practices for RS MRO, predictive maintenance variables and key performance indicators, data analytics, software solutions for RS MRO, and logistics/supply chain approach that should be considered. These insights provide not only a comprehensive understanding of the current state of RS MRO but also describe trends and suggestions for the future of RS MRO, emphasizing the novelty of the proposed research conducted. Key trends that organizations will need to address include the use of artificial intelligence (AI) models and the increasing importance of RS MRO logistics and supply chain management
Improved APF-based path planning for aircraft towbarless towing vehicle system
Get PDFTo enhance the maneuvering efficiency and safety of the aircraft towbarless towing vehicle (TTV) system, this study presents an optimized path planning method based on an improved artificial potential field (APF) algorithm. First, comprehensive kinematic and dynamic models are established, incorporating both lateral and yaw motions of the TTV system. Second, to mitigate obstacle interference challenges in complex airport environments, the proposed method introduces an innovative relative-distance safety factor and implements a dual-repulsive-force cooperative planning strategy, effectively overcoming the traditional APF algorithm’s limitations regarding goal unreachability and local minima. Furthermore, the integration of Bézier curves ensures curvature continuity in the planned path, thereby maintaining compliance with kinematic constraints. Finally, a constrained-motion TTV simulation model is developed to validate the algorithm’s performance. Simulation results demonstrate that, in static obstacle scenarios, the proposed method successfully enables autonomous path planning, generating smooth and collision-free trajectories. This approach offers a robust solution for ensuring stable and reliable operation of the TTV system in real-world airport environments
Research on the temperature system of an evaporator based on Smith-VUF PID
Get PDFTemperature serves as a critical process parameter in industrial systems, directly influencing reaction kinetics, product quality, and operational efficiency. The variation of temperature can affect reaction rate, product quality, and impurity generation, directly impacting production efficiency and product performance. However, due to the nonlinearity of temperature control systems, traditional controllers cannot meet design requirements, particularly in scenarios demanding high - temperature control accuracy, it is difficult for them to achieve a small deviation range. Therefore, this study focuses on the evaporator as the controlled object and conducts modeling, simulation analysis, and control strategy research on the evaporator temperature control system. It establishes the Smith-variable universe fuzzy PID(Smith-VUF-PID) temperature control system and deploys control strategies, solving issues such as large overshoot and inadequate control accuracy often encountered with traditional methods