Research on the Formation Mechanism of Surface Morphology in Three-Excitation Ultrasonic Spatial Vibration-Assisted Turning

To improve the machining performance of different processing materials, a three-excitation ultrasonic spatial vibration-assisted turning system is proposed, which realizes the non-unity of the plane where the cutting trajectory of the tool is located. The influence and formation law of three-excitation ultrasonic spatial vibration-assisted turning on the surface roughness of the workpiece under different vibration parameters (amplitude) and machining parameters (cutting speed, cutting depth, and feed) were analyzed by response surface methodology. The results show that in terms of vibration parameters, the influence of ultrasonic vibration applied in the horizontal direction on surface roughness is significantly greater than that of ultrasonic vibration applied in the vertical direction, while the feed has the greatest influence on surface roughness, followed by cutting speed. The surface roughness of common turning, one-dimensional ultrasonic vibration-assisted turning, ultrasonic elliptical vibration-assisted turning, and three-excitation ultrasonic spatial vibration-assisted turning were theoretically analyzed and experimentally compared. The results show that compared with the other three turning methods, the three-excitation ultrasonic spatial vibration-assisted turning can obtain a lower surface roughness and have good machinability.

Train Derailment Process Analysis on Heavy Haul Railway Bridge under Ship Impact

In order to research train derailment law under ship impact, the spatial vibration calculation model of a freight train-track-bridge (FTTB) system is used to establish the vibration model of the FTTB system under ship impact. Meanwhile, the calculation method of a train derailment process under ship impact is proposed based on the random analysis method of train derailment energy. Further, the train derailment process on a bridge under ship impact is calculated, and the variation law of the FTTB system spatial vibration response under different impact loads and speeds is analyzed. The results show that the ship impact load has a great influence on wheel lift value. When the impact load is greater than 15 MN, the wheel derails more easily. With the increase of impact load, the derailment coefficient, wheel load reduction rate, and lateral relative displacement of bogie and rail, the lateral displacement of the bridge increases significantly, but the limits of them make it difficult to determine whether the wheel has derailed. The lateral relative displacement of the bogie and rail considering the safety factor is calculated at the moment of derailment, which is taken as the early warning threshold of train derailment. The above conclusions can provide a reference for controlling train safety under ship impact.

Quantitative Evaluation for Reinforcement Effect of Auxiliary Steel Beams Based on Running Safety and Dynamic Response

Aiming at the existing heavy-haul railway, bridges hardly meet the transportation requirements. Based on the spatial vibration calculation model of the freight train–track–bridge (FTTB) system, the FTTB spatial vibration model under the condition of auxiliary steel beam reinforcement is established. Besides, according to the random analysis method of train derailment energy, coming up with an evaluation method of auxiliary steel beam reinforcement is based on safety and dynamic response, which is used to discuss the train safety and the change law of FTTB system vibration response. The results show that the derailment resistance of the FTTB system is increased by 22.6% after the auxiliary steel beam is reinforced. Compared with the previous speed (115.56 km/h), the speed is 132.73 km/h after the auxiliary steel beam reinforcement; at the same time, the allowable limit speed increases from 92.49 km/h to 106.18 km/h. In addition, the reinforcement of the auxiliary steel beam can not only effectively reduce the lateral vibration response of the FTTB system under the action of empty wagon but also effectively decline the vertical vibration response of the FTTB system under the action of the loaded wagon, which can meet the stability requirement for running at the speed of 90 km/h. In summary, the reinforcement of auxiliary steel beams can improve the running safety of trains, reduce the vibration response of the FTTB system, and meet the requirements of operation stability.

Synchronization of Two Eccentric Rotors Driven by One Motor with Two Flexible Couplings in a Spatial Vibration System

A dynamic model of a vibration system, in which eccentric rotors are driven by one motor with two flexible couplings, is developed in this study. The Lagrange equation is used to analyze the dynamic behavior of the vibration system. Synchronization theory and its motion law are investigated using Hamilton’s principle, and the validity of the theory is proven through numerical simulation and experimentation. Results show that the system has two synchronous motions, namely, 0 and π phases. When the torsional stiffness difference between two flexible couplings on both sides of the motor or the resistance moment difference between two eccentric rotors increases, the eccentric rotors maintain the synchronization and stability of the vibration system by adjusting its phase difference. Synchronization theory and the analysis method of the flexible-drive vibration system are extended in this study. Moreover, the synchronous motion law of the vibration system based on bilateral flexible drive by one motor is revealed to provide guidance for the development of high-performance vibrating machines.

On the oscillations of spatial vibration-isolating system of mining machines under the action of impact loads

Theoretical and experimental results concerning interaction between lumpy loads and loading sections of a belt conveyer have been represented. The rational parameters of the loading section of the conveyor belt are determined from the point of view of reducing the amplitude of oscillations after the interaction. The regularities of oscillation amplitude of a loading section after interaction with a single lump have been identified.