Search

Current numerical research on snow accumulation on bogies often simplifies train models as 1.5 cars or 3 cars, and there is less research on long marshalling trains with real bogies. In this article, based on the Euler–Lagrange method, the airflow structure and snow accumulation characteristics in the bogie area of an 8-car high-speed train (HST) are studied by numerical simulation. The results show that the airflow velocity and snow distribution concentration inside the bogie cabin vary along the flow direction. The downstream bogie cabin has a lower airflow speed, spatial snow particle concentration, and components snow accumulation. Because of the bogie cabin cover structure, the main airflow direction above the first and second bogie cabin is different, resulting in higher snow concentration and range on the windward side of the first bogie. There is a significant difference in snow accumulation characteristics between powered and nonpowered bogies. The powered bogie gearbox is directly affected by the airflow carrying snow particles, leading to severe snow accumulation on the windward side. This study provides a research foundation and engineering guidance for the snow protection strategy of HST bogies and is important for improving the comfort and safety of HSTs on snow-covered rails. [ABSTRACT FROM AUTHOR]

CoCrMo alloys are often used in the manufacture of artificial joints in the medical field, and their special working environment will lead to corrosion and abrasion of the surface materials, thus reducing the service life of the joints. Surface texturing technology can improve the friction performance of joints by reducing the friction area, storing abrasive particles and lubricants, etc. Its application in the field of CoCrMo alloy joint surface strengthening is of great significance. This paper analyses the characteristics of surface fabrication processing technology and the friction reduction mechanism of surface fabrication under fluid lubrication and dry friction conditions, summarizes the influence of various fabrication parameters (fabrication depth, size, density, shape, etc.) on the friction performance of the alloy, introduces other surface technologies of CoCrMo alloy as well as common medical materials, summarizes the existing problems in the research of CoCrMo alloy surface reinforcement technology at this stage and makes a study on the development direction of the surface reinforcement technology of CoCrMo alloy in the field of artificial joints. The development direction of CoCrMo alloy in the field of artificial joints is also prospected. [ABSTRACT FROM AUTHOR]

As a breakthrough of the additive manufacturing technology being achieved, many fields have broadly applied laser cladding due to its unique advantages. But the surface characteristics of the cladding layer are not frequently aligned with the standards necessary for industrial use. Consequently, with a particular focus on refining its surface roughness, it has emerged as a significant area of interest among numerous investigators. This paper reviews a variety of methods for optimizing the surface roughness of laser cladding, covering from deterministic algorithms such as Taguchi's method, orthogonal experimental method, gradient descent method, to stochastic algorithms including neural network, genetic algorithm, Gray Wolf algorithm, and even hybrid algorithms combining multiple algorithms like neural network genetic algorithm, adaptive neural fuzzy reasoning algorithm, and improved genetic algorithms for response surface analysis, and so on. Through comparative analysis, it is found that the hybrid algorithms can quickly generate the optimal optimization parameters for the sake of achieving the optimal surface quality since they may combine the accuracy of deterministic algorithms and the robustness of stochastic algorithms. In addition, this paper also looks forward to the future development direction of surface quality optimization methods for laser cladding, aiming at laying a foundation for the research work of high-quality coating preparation. [ABSTRACT FROM AUTHOR]

In the biomedical field, the commonly used metal implant materials are prone to "stress shielding" because of their mechanical properties and elastic modulus are very different from human bone. The mechanical properties of metal materials are often difficult to maintain in corrosive media and release harmful ions. Nor can it reliably establish a sufficient combination with human bones, resulting in a service life that does not reach the desired goal. Researchers in this field propose to combine the superior mechanical properties of metals with bioactive materials, such as bioactive ceramics and the emerging ferrous glass, and achieve this through surface modification techniques. The laser cladding technique is of great interest for its low dilution rate, high bond strength and fine organisation. This review paper describes the development of common medical metal materials and the research progress of laser cladding surface modification technology. [ABSTRACT FROM AUTHOR]

In this paper, we provide a summary of six output variables in the milling process. These variables include cutting force, tool wear, surface roughness, surface burr, residual stress, and microhardness. The cutting force has an impact on the power consumption during the cutting process and serves as a reflection of the cutting state. The tool wear degree determines the performance of cladding layer after milling. Surface roughness and surface burrs can affect the surface quality and final use of the workpiece after milling. Excessive residual stress can cause distortion, deformation, and even cracking of the parts. Microhardness is used to evaluate the service life and reliability of materials. Examined the various influencing factors on the six output variables' influence. These various influencing factors not only impact the output variables, but also affect the cutting state, workpiece surface quality, tool life, and other aspects of the cutting process. The generalization of the various influencing factors primarily encompasses various milling parameters, cutting directions, treatments of the fused cladding layer, construction orientations of the fused coating layer, and machinability of the fused coating layer. By studying the output variables and influencing factors of molten cladding milling, researchers have gained a more comprehensive understanding of this process. Ultimately, they have also forecasted future development directions for molten cladding milling, the utilization of ultrasonic vibration machining, Electrical Discharge Machining assisted machining, and computer simulation technology in cladding layer milling shows promising development prospects. [ABSTRACT FROM AUTHOR]

In the present paper, a unique laser cladding-assisted high-frequency vibration device was applied to prepare the AISI 316L cladding layer by laser cladding on the surface of the AISI 316L stainless steel substrate. The macroscopic morphology, microstructure, microhardness, and wear resistance of the cladding layer were analyzed by optical microscope, scanning electron microscope, Vickers microhardness tester, friction and wear tester, and three-dimensional optical profiler. The laser cladding-assisted high-frequency vibration device uses a high-frequency oscillator with a fixed frequency (20 KHz) to transfer vibration energy through the probe in contact with the substrate and close to the molten pool. This paper explores the effect of different laser powers on the dilution rate of the cladding layer, compares and observes the cross-sectional morphology and microstructure of the cladding layer with and without high-frequency vibration, and analyzes the reasons for the different results. [ABSTRACT FROM AUTHOR]