Search

This study aimed to investigate the metallographic structure and the impact of the heat treatment process on the MAR-M247 superalloy, a high-temperature nickel-based superalloy commonly used in turbine blades. The heat treatment process can potentially influence the mechanical properties of the MAR-M247 superalloy at different temperatures. A strength simulation analysis of gas turbine blades should include the variations in the mechanical properties of the material. The effect of heat treatment on grain size was investigated by metallographic experiments, and numerical calculations of material mechanical properties were conducted. The mechanical property parameters necessary for finite element analysis of turbine blades were determined. Finally, a finite element simulation model of the blade was established based on these mechanical property parameters, and strength analysis was performed. The simulation results provided the stress distribution and the strength of the turbine blade.

With the development of urban rail transportation, the environmental vibration problem caused by the running of metro vehicles has received attention. In order to reduce ground vibration near buildings caused by metro vehicles running on viaducts, this paper establishes the train–track–viaduct rigid–flexible coupling dynamics model and pier–soil–building finite element model and carries out the simulation calculation and analysis of ground vibration. The influence of train speed and fastener stiffness on ground vibration is explored, and the vibration reduction effect of the track vibration reduction pad and continuous support vibration reduction structure is studied. The results show that the ground vibration near the building caused by the train running on the viaduct decreases with the reduction in speed, when the speed is reduced to 40 km/h, the vibration attenuation is slower as the speed continues to be reduced; the reduction in the vertical stiffness of fasteners can reduce ground vibration; the arrangement of the vibration damping pad can effectively reduce ground vibration, and after installing a vibration damping pad, 0–23 Hz and 50–80 Hz ground vibration speeds are effectively suppressed. In order to meet the environmental requirements for ground vibration, the vehicle speed can be reduced to less than 35 km/h or vibration damping mats can be installed.

High-speed direct-drive permanent magnet synchronous motors (PMSMs), supported by elastic foil gas bearings, have broad applications, such as in microcompressors. However, some problems remain to be solved for the electrical performance analysis of PMSMs. For example, there is presently no related analytical model that can be used in rotor dynamics expression for this type of PMSM. This study aimed to establish theoretical models for electromagnetic force density and torque. The process involved both theoretical and experimental research. The analytic models of air gap magnetic density, electromagnetic force density, and electromagnetic performance were established for a PMSM with a parallel magnetized cylindrical permanent magnet. The analytic calculation was conducted, and the results of the analytic model were obtained. The analytical model of the electromagnetic torque and force can be applied in theoretical research on rotor dynamics. The model provides a theoretical basis and method for studying the influence of the electromagnetic load on rotor dynamics. A finite element simulation analysis of the electrical performance of the PMSM was carried out. An electrical performance experiment was conducted. The deviation between the experimental result and the theoretical value was less than 4%. This result indicated that the analytic models could be used in a dynamics analysis of compressors that are directly driven by a PMSM for application in engineering and industrial contexts.

The operation transfer path analysis (OTPA) technique was used to measure the vibration and noise transfer coefficient functions of wheel-rail noise and radiated noise from an electric multiple unit (EMU) train (high-speed train in China) trailer bogie structure to the central area of the trailer bogie for a train running at speeds of 0–5 km/h. By applying these transfer coefficient functions to the noise analysis of high-speed train operation, the contributions of wheel-rail noise and frame-radiated noise to the noise of the bogie area at high speeds are obtained, and the aerodynamic noise is separated from the total noise, providing a reference for vibration damping and noise reduction in high-speed trains. Analysis of test data shows that, in the central area of the trailer bogie of high-speed trains, the low-frequency noise mainly comes from the structural radiated noise of the bogie, and the mid- to high-frequency noise is primarily due to aerodynamic noise. In addition, when an EMU train operates at speeds below 250 km/h, the noise in the central area of the trailer bogie is primarily caused by the structural radiated noise. When the operating speed is higher than 250 km/h, the noise in the central area of the trailer bogie is mainly due to aerodynamic noise, and the aerodynamic noise contribution increases with increase in speed.

For noise simulation of a high-speed train passenger compartment, an equivalence study of vehicle body hollowaluminumprofiles is imperative for reducing the finite element calculation in the simulation process and adapting to the requirements of statistical energy analysis. From the perspective of structural vibration and acoustic radiation, hollow aluminum flooring was used as an example. This study provides a noise-, vibration-, harshness-(NVH) equivalent plate acquisition method for hollow profiles and plates and studies the engineering application conditions and deviations of the equivalent structure. In accordance with the NVH-equivalent method for hollow profiles, a basic process is furnished for acquiring the properties and parameters of the equivalent plate. The consistency of vibration and noise insulation between the equivalent plate and hollow profiles plate has been validated through simulation. An electric multiple unit (EMU) interior noise simulation example showed that for an interior noise simulation model using equivalent plates, the prediction accuracy of interior noise can meet the requirements of engineering applications while significantly reducing the simulation time. [ABSTRACT FROM AUTHOR]