Analysis of shimming performance and clearance influence under manipulation state

During the roll control process of an aircraft, shimmy often occurs, usually manifested as high-frequency and low amplitude vibrations. In order to better analyze the essential causes of landing gear shimmy, this paper establishes a flexible shimmy dynamics model for the nose landing gear and analyzes the influence of the hydraulic stiffness of the control actuator. The analysis shows that a decrease in stiffness will reduce the stability of the system, and the shimmy frequency will decrease, but the frequency will be higher than the reduced shimmy state. Finally, the system damping ratio is compared to evaluate the stability of the system. Based on the above model and combined with clearance theory, a set of shimmy dynamics model considering the influence of clearance was established. The results show that radial clearance has almost no effect on shimmy; The presence of axial clearance can cause equal amplitude vibration in the system, and increasing the clearance value can cause an increase in amplitude; When the initial swing angle of the system is different, the system will gradually swing to the same amplitude of vibration; There is a coupling effect between system stiffness and clearance values, and as the system stiffness decreases, its amplitude will increase nonlinearly

Research of the structure and properties of nanostructured coatings based on chrome

Nanostructured chromium-based coatings have been researched. In some cases, it is expedient to use vacuum methods of deposition of chromium coatings by methods of thermal evaporation of pure chromium from tungsten coils or by ion-plasma (magnetron) sputtering method. Due to the low deposition temperature of coatings, there is a possibility of their formation on metallic and non-metallic materials. Based on the above, it is necessary to note the relevance of the study of the technology for the formation of chromium-based coatings by the ion-plasma method. To apply wear-resistant chromium coatings to samples made of R6M5 steel, the method of ion-plasma (magnetron) sputtering with a preliminary treatment of the surface with an ion source was used. The thickness, adhesive strength and corrosion resistance of chromium-based coatings were determined. Electron microscopy methods have been used to study the morphology of the surface and the size of nanoparticles in the structure of chrome coatings. It was revealed that depending on the modes of formation, the coating consists of nanoparticles with sizes from 15 nm to 230 nm

Mechanics of composite fiber pull-out from concrete with fly ash using the DCB test

This study explores novel concretes where cement is partially replaced by oil shale ash (OSA), reducing CO2 emissions, and incorporates patented composite fibers for enhanced mechanical performance. The mechanics of fiber pull-out and interfacial bond strength in concrete reinforced with short fibers, where cement is partially replaced by either fly ash or OSA, using the Double Cantilever Beam (DCB) test. The research aims to assess how these eco-friendly additives impact the fiber-matrix bond and crack propagation resistance in fiber-reinforced concrete. In the experimental setup, two partially sawn concrete beams were joined along their length by a thin, fiber-reinforced concrete layer and subjected to a tensile force, simulating crack opening. Concrete specimens (400×210×100 mm) with varying ash contents were tested, focusing on key parameters such as peak load, energy absorption, and interfacial toughness. Findings indicate that both fly ash and basalt enhance the mechanical properties of the concrete, with significant improvements in load transfer and fiber pull-out resistance observed, particularly at higher ash contents. Analysis of force-displacement curves and fracture surfaces demonstrated a shift from brittle to more ductile behavior as ash content increased, enhancing the fracture resistance of the composite. This research supports the use of alternative cementitious materials like fly ash and basalt in developing sustainable, high-performance fiber-reinforced concrete, with potential applications in structural engineering and eco-friendly construction practices

A rolling bearing fault diagnosis method under insufficient samples condition based on MSLSTM transfer learning

It usually affects the accuracy and reliability of deep learning based intelligent diagnosis methods under the condition of insufficient samples. Existing methods for handling insufficient samples often have problems such as requiring rich expert experience or consuming a lot of time. To solve the above problems, a rolling bearing fault diagnosis method under insufficient samples condition based on multi-scale long-term and short-term memory network (MSLSTM) transfer learning is proposed, which mainly consists of an improved long-term and short-term memory network named as MSLSTM and transfer learning. By introducing multi-scale convolution operation into the traditional LSTM to improve its drawback that only extracts single type of fault feature information, which leads to poor diagnostic performance in noisy environments. Besides, the pooling layer and global average pooling layer in traditional LSTM are replaced with convolution operation to avoid the problem of information loss. Subsequently, the MSLSTM is combined with transfer learning, and a rolling bearing fault diagnosis method under insufficient samples condition based on MSLSTM transfer learning is proposed, which fine tunes the model parameters using a small amount of target domain data. Feasibility of the proposed method is verified through two kinds of experiments. The proposed method has stronger feature extraction ability and training efficiency compared with other models

Design and simulation of a cable-driven elbow rehabilitation device

With the increasing prevalence of neurological and musculoskeletal disorders, the demand for effective rehabilitation technologies has grown. This study presents the AlmatyExoElbow system with a cable-driven exoskeleton for elbow rehabilitation with two degrees of freedom. The device was designed in SolidWorks CAD and tested in SolidWorks Motion to evaluate flexion/extension and pronation/supination trajectories. The design is simple, adaptable, and cost-effective, making it a promising candidate for future clinical integration and personalized therapy

Analysis of heat treatment parameters of 60Si2CrV steel to enhance the mechanical properties of elastic structural elements

The article analyzes how the temperature of the quenching medium during heat treatment influences the mechanical properties of spring steel grade 60Si2CrV. It presents the correlations between the quenching medium temperature and such parameters as hardness, tensile strength, and elongation. The study identifies the optimal cooling medium temperature range to be 20-30 °C, which ensures enhanced mechanical performance of the steel. The findings can be applied to improve the heat treatment processes of cylindrical springs used in freight wagons, thereby increasing their service life and operational reliabilit

Improved iterative reweighted L1 norm minimization method for sound source identification

Sparse reconstruction algorithm is one of the main research topics in compressed sensing. To address the shortcomings of existing iteratively reweighted l1-norm minimization methods, which exhibit poor performance in low-frequency sound source identification and weak anti-interference capability, this paper proposes an improved iteratively reweighted l1-norm minimization method. Unlike traditional methods, this method introduces a log-sum penalty function and constructs a surrogate function, transforming the problem into an effective form for solving the source strength distribution vector. Through numerical simulations comparing the two methods under different frequencies and signal-to-noise ratios (SNR), the results demonstrate that the proposed method enhances both the sound source identification accuracy and anti-interference capability of the algorithm, while also being able to adapt to lower frequency ranges

Improvement of the classification of causes for the decommissioning of large-size tires

The article presents the results of the analysis of the causes of failure of large-size tyres operated in the conditions of Navoi MMC. On the basis of generalisation of the accumulated data the classification of the main factors leading to tyre failure is proposed. All causes are grouped into three key categories: wear, mechanical damage and thermal damage. Wear includes the processes of natural and accelerated tread abrasion, as well as various forms of uneven wear arising from deviations from the recommended operating conditions. Mechanical damage is considered as a result of short-term or long-term external impacts, including punctures, cuts, cord breaks and frame deformations. In 2024, the plant used more than 19 thousand car tires with a total value of about 1.4 trillion soums. These quarry dump trucks use tires manufactured by Bridgestone, Goodyear, Luan, Michelin, Techking, Advance, Aeolus, Maxam and Noble. For transport enterprises, the task of rational use of tire resources by improving the condition of quarry roads and reducing premature tire failure is relevant. The results obtained can be used to improve tyre maintenance and condition monitoring systems at mining enterprises

Research of heat transfer processes in motor-axial bearings of traction electric motors of diesel locomotives

Original calculation schemes of the motor-axle bearing and the distribution of heat flows in the process of heat removal from the surface layer of lubricant to the axle journal of the wheel pair and to the motor-axle bearing liner are proposed, taking into account its middle layer. In order to substantiate the maximum amount of heat released in the motor-axle bearings of a freight diesel locomotive of the 2TE10 series and caused by the action of friction forces in the zone of contact their with the journals of the axles of the wheel pairs, taking into account the theoretical foundations of heat transfer and the accepted assumptions in the specified calculation schemes, analytical dependencies were obtained to determine the quantities characterizing heat removal from the mentioned motor-axial bearings using three flows. As a result of implementing the proposed analytical dependencies and performing numerical calculations, it was proved that the operation of the studied motor-axial bearings is carried out in the semi-fluid friction mode and at negative temperatures of the external (atmospheric) air, their normal operation is not ensured due to the low proportion of heat removal by the lubricant, which does not exceed 1.5 percent, and therefore, this leads motor-axial bearings to premature wear and failure, and thereby reduces the operational reliability of the wheel-motor unit of diesel locomotives

Enhancing the mechanical and functional characteristics of structural spring steel through the advancement of heat treatment technologies

The article discusses the improvement of the technology of heat treatment of springs made of structural spring-spring steel grade 55Si2, used in rolling stock of railway transport. The authors conducted extensive experiments to study the effect of different temperatures and duration of heat treatment on the mechanical properties of springs. During the research, optimal quenching and tempering modes were identified, which significantly improved the strength characteristics, wear resistance and stability of the springs. The results of the work formed the basis of new technological instruction aimed at improving the quality and increasing the yield of usable products, which is important for improving the reliability of freight wagons operation