Multi-constrained Quality of Service (QoS) routing algorithm is always a difficult problem in routing research area, which is a NP problem. Software Defined Network (SDN) is a new network architecture, in which there's few research on QoS routing. This paper generates the whole network virtual topology according to the characteristics of SDN, and based on the principle of simulated annealing, proposes a nonlinear annealing algorithm, which adapts to the SDN. Firstly we simplify the network topology by Dijkstra-like algorithm, and then introduce the nonlinear energy function, and then iterate the initial solution according to the simulated temperature, until find a feasible path from the source node to the destination node which satisfies the condition. Experimental results show that this algorithm has a higher success rate, better expansibility of network size, and better transplantation for the SDN than traditional QoS routing algorithm.

Wheel polygon amplitude can greatly affect wheel-rail vibration and sound radiation. Based on multi-body dynamics theory, a vehicle-track rigid-flexible coupling dynamics model was established. According to the actual running wear condition of the wheel, the wheel-rail vibration response was calculated and analyzed (the order of wheel polygons is 20, and the polygon amplitude is 0.01/0.02/0.03/0.04 mm, respectively). Together with the finite element/boundary model of the wheel, the calculated wheel-rail force was used as an external incentive to analyze the effects of polygon amplitude on the time-frequency domain of wheel noise. The research results show that: when the polygon order is 20, with the increase of polygon amplitude, the wheel-rail vertical force and the acceleration of wheel, rail and track slab increase gradually. It’s also found that the rail acceleration is obviously more sensitive to the amplitude than the track slab acceleration, while the vertical displacement of the rail and track slab is less sensitive to the polygon amplitude. At the same amplitude, the closer to the wheel rolling line, the more obvious the sound pressure decreases with the increase of height. At different amplitudes, the sound pressure at different positions will increase with the rise of the polygon amplitude. The root mean square value of sound power increases gradually with the addition of amplitude: When the amplitude changes from 0.01 mm to 0.04 mm, the calculated sound power increases by 4.1 dB.

High-level wheel polygon wear is common in high-speed EMUs. Wheel polygon wear causes high-frequency vibration of vehicles and track systems, which seriously affects the safe operation of vehicles. Some key influencing factors are of great significance for restraining wheel polygon wear. In this paper, a long-term wear iterative model is established by combining the coupled vehicle/track dynamic model with the Archard wear model, which is used to simulate the whole development process of high-speed train wheel polygon. The development process of wheel polygon is simulated when the vehicle runs at 300 km/h. The simulating results are consistent with the actual situation. It is found that changing the speed of the vehicle can prevent the rapid development of the wheel polygon of a fixed order, so as to slow down the development of the wheel polygon. As the wheel hardness increases, the roughness level gradually decreases. If there is corrugation in the rail, it will greatly accelerate the development of wheel polygon, especially when the wavelength of rail corrugation can divide the wheel circumference. In addition, with the increase of rail corrugation amplitude, the promoting effect will gradually increase.

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The fatigue resistance and failure behaviour of penetration 1.5 + 0.8-P and non-penetration 0.8 + 1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated. The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance, and their hardness was lower than that of the plates. The 1.5 + 0.8-P joint exhibited a better resistance to high-cycle fatigue failure, while the 0.8 + 1.5-N joint showed a higher resistance to low-cycle fracture. The failure modes of 0.8 + 1.5-N and 1.5 + 0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture, respectively, and the primary cracks were initiated at welding fusion lines on the lap surface. There were long plastic ribs on the penetration plate fracture, but not on the non-penetration plate fracture. The fatigue resistance stress of the penetration and non-penetration plates in the crack initiation areas calculated based on the mean fatigue limits is 408 MPa and 326 MPa, respectively. The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.