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Due to the short distance between stations, frequent acceleration and braking for urban rail trains cause voltage fluctuation in the traction network and the regenerative braking energy loss. In this study, a hybrid energy storage system (HESS) was proposed to recover braking energy and stabilize the traction network voltage, where the on‐board ultracapacitors were used to accommodate the rapid exchange of acceleration and braking energy of the permanent magnet traction system while the lithium batteries installed in the bilateral stations provided stable and long‐lasting energy exchange, which can stabilize traction network voltage and be charged at off‐peak night time. In order to realize the energy coordinated control between the permanent magnet traction system and HESS, a real‐time energy management strategy was proposed to dynamically allocate the traction power based on the principle of giving priority to on‐board ultracapacitors while lithium batteries as auxiliary power supply. Moreover, the charging and discharging voltage thresholds of the lithium batteries were dynamically set according to train positions and their charge status. Comparing with the traditional strategies, the RT‐LAB semi‐physical real‐time simulation shows that the proposed strategy can provide more effective energy allocation, and stabilize the voltage fluctuation while maximizing the energy saving.

With the development of wind turbines to the large scale with high rated powers, how to reduce fatigue loads is the key factor for modern wind turbine control. Aiming at reducing the wind turbine structural fatigue loads, an individual pitch control (IPC) method based on SVM estimation of blade root loads was proposed in this paper. The blade root loads were dynamically estimated by a SVM model according to light detection and ranging (LIDAR) wind speed data. Two approximate decoupling systems for yaw moments and pitch moments were then obtained through Coleman transform. Meanwhile, two individual pitch controllers were designed to reduce the loads and a wind speed feedforward controller was adopted to improve the pitch control performance. The proposed method was verified by a FAST, LIDAR and RT-LAB semi-physical real-time combined simulation system. On this basis, a master control unit was developed and the overall unit was further verified by a CRRC wind turbine master control and pitch joint test platform. Compared with collective pitch control (CPC) and the IPC based on azimuth, the proposed method is effective on reducing fatigue loads and vibration.

The supply voltage of traction systems fluctuates frequently due to acceleration and braking during urban rail train running process. In order to achieve better performance for ultracapacitor energy storage systems, a bilateral ultracapacitor energy storage system structure is adopted, and a method based on dynamic setting and coordination is proposed, in which the charge and discharge voltage thresholds of ultracapacitors are dynamically set and the energy flows are coordinated controlled between the bilateral ultracapacitor energy storage systems. The simulation results show that the proposed control strategy can achieve good energy-saving effect and stabilize the traction network voltage under the premise of balanced use of the ultracapacitor energy storage systems.

The formability of aluminum alloy AA7075 at elevated temperature was investigated through experiment. Stress–strain relationship at different temperatures and forming speeds were investigated through tensile testing. Deep drawing and stretch formability were also tested through limiting drawing ratio (LDR) and limiting dome height (LDH) tests. Finally, post forming mechanical property testing was conducted to investigate the effects of exposure to warm forming temperatures on the mechanical properties. Results show that deep drawing and stretch formability of AA7075 can be significantly improved when the blank is heated to 140–220°C. At temperature over 260°C, formability and post forming mechanical properties begin to decrease due to the effect of the heating and forming processes on the material's temper.

Superplastic forming (SPF) is a manufacturing process that can facilitate increased use of aluminum in automobile body structures. Despite considerable advantages with regards to formability and tooling costs, the process has been mostly limited to low volume production due to relatively long cycle times and the need to use specially processed sheet alloys. To address these issues, advanced processes such as two stage gas forming (TSGF) and hot draw mechanical pre-forming (HDMP) have been developed. Advantages of these processes have been demonstrated on the forming of a complex dash panel part. Final thickness distribution and forming time on this part manufactured with these two processes were compared to that of the same panel produced with conventional SPF. The HDMP technology which combines hot stamping with SPF was found to have the capability of forming a complex shaped component with a superior thickness profile and faster forming cycle than that formed with a conventional single stage or two stage forming cycle. Additionally, the HDMP process proved to be a robust process with a wide temperature window and allowed for the forming of lower-cost, non-spf aluminum, and magnesium sheet alloys. Finally, analysis of the post-form microstructure indicated that there was essentially no cavitation in panels formed with the HDMP process and that material with a coarse grain structure could be successfully formed.

As an important sheet metal forming process, stretch flanging is widely applied in automobile industry. The formability of sheet metal during stretch flanging depends on appropriate process parameters. In this paper, an elastic–plastic large deformation FEM program is developed based on Mindlin shell element model. A quasi-flow corner theory of elastic–plastic finite deformation and a normally anisotropic yield criterion are introduced. Then the stretch flanging of a V-shaped sheet metal part is simulated and the effects of geometry and material on flanging are unveiled according to the calculated results. Meanwhile, a mathematical model for axisymmetric case (flanging tube) is developed based on the total strain theory and membrane assumption. Compared with material parameters, geometrical parameters exert greater effects on the formability and the flange angle is the most influential parameter affecting the free edge strain. The analytical model is easy to use, but it gives reasonable results only when the flange angle or initial flange length is small.

In this paper, the superplastic forming (SPF) potential of two fine-grained 5083 aluminum alloys were studied under various stress states with the use of both high temperature tensile testing and pneumatic bulge testing. Experiments with the pneumatic bulge test were performed at temperatures ranging from 475 to 525 °C under three different strain paths ranging from equi-biaxial to approaching plane strain. The effects of temperature on total elongation, m-value, final thickness distribution, dome height, and cavitation were investigated for the case of uniaxial and equi-biaxial stretching. Increased temperature in bulge forming was found to improve the thickness distribution in the formed parts, but did not have a significant effect on dome height. The shape of the forming limit diagram (FLD) was found to be significantly different than that of FLDs commonly used in room temperature stamping. Results indicate that determination of forming limits in SPF cannot be represented with a simple FLD and additional metrics such as external thinning and internal cavitation need to be considered to determine a material’s SPF potential.