Laser cladding (LC) is a process in which materials with certain properties are added to the surface of a substrate

Speed uplift has become the leading trend for the development of current railway traffic. Ideally, under the high-speed transportation infrastructure, trains run at specified positions with designated speeds at appointed times. In view of the faster adaptation ability of multiple-model adaptive control with second-level adaptation (MMAC-SLA), we propose one type of MMAC-SLA for a class of nonlinear systems such as cascaded vehicles. By using an input decomposition technique, the corresponding stability proof is solved for the proposed MMAC-SLA, which synthesises the control signals from the weighted multiple models. The control strategy is utilised to challenge the position and speed tracking of high-speed trains with uncertain parameters. The simulation results demonstrate that the proposed MMAC-SLA can achieve small tracking errors with moderate in-train forces incurred under the control of flattening input signals with practical enforceability. This study also provides a new idea for the control of in-train forces by tracking the positions and speeds of cars while considering power constraints.

Offshore wind turbine generators usually demand higher requirements for key component materials because of the adverse working environment. Therefore, in this study, electromagnetic-assisted laser cladding technology was introduced to prepare the nickel-based composite coating on the Q345R matrix of wind turbine generator key component material. By means of Scanning Electron Microscope (SEM), X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), the Vickers hardness tester, friction and wear tester, and electrochemical workstation, the effects of different magnetic field intensities on the macroscopic morphology, microstructure, phase composition, microhardness, wear resistance, and corrosion resistance of the coating were analyzed. The experimental results show that the addition of a magnetic field can effectively reduce the surface defects, improve the surface morphology, and not change the phase composition of the coating. With the increase in magnetic field intensity, the microstructure is gradually refined, and the average microhardness increases gradually, reaching a maximum of 944HV_0.5 at 8 T. The wear resistance gradually increases with the increase in magnetic field intensity, especially when the magnetic field intensity reaches 12 T, the wear rate of the coating is reduced by 81.13%, and the corrosion current density is reduced by 43.7% compared with the coating without a magnetic field. The addition of an electromagnetic field can enhance the wear resistance and corrosion resistance of the nickel-based laser cladding layer.

A new kind of low-carbon bainite steel with excellent strength and toughness was developed, serving as the bogie of the next-generation high-speed train. However, the softening of the heat-affected zone (HAZ) in laser-arc hybrid welding (LAHW) needs to be overcome. In this study, the effect of the cooling rate of the LAHW process on the microstructure and mechanical properties in the HAZ was explored via thermal simulation. The results showed that with increased cooling rate, the grain size increased, the content of lath martensite decreased, and the lath bainite gradually changed to a granular shape in the thermal simulation specimen. With the decrease in the cooling rate, i.e., with the increase of t_8/5, the strength–toughness matching of the material showed a downward trend. The thermal simulation specimen with a t_8/5 of 6~8 s had higher strength and good toughness, which can be considered a potential welding parameter reference. The content of martensitic austenite (M-A) constituents was the main factor that determined the strength and toughness of the joint. During the tensile test, the axial force caused the material to tighten, and the transverse stress as obvious in the part of the M-A constituents that are prone to microcracks and many defects, resulting in cracks, paths, and multi-component layers in the center. As a result, the thermal cycle specimens had mixed fracture characteristics.