Research on the formability of tailor rolled blank （TRB） is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight. However, the forming...Research on the formability of tailor rolled blank （TRB） is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight. However, the forming of TRB is problematic because of the varying properties; especially, springback is a main challenge. The transverse bending （bending axis is perpendicular to the rolling direction） of TRB U channel was studied through simulation and experiment. The forming characteristics of TRB U channel during transverse bending were analyzed. The mechanisms of forming defects, including bending springback and thickness transition zone （TTZ） movement, were revealed. On this basis, effects of blank geometric parameters on springbaek and TTZ movement were discussed. The results indicate that springback and TTZ movement happen during transverse bending of TRB U-channel. Nonuni form stress distribution is the most fundamental reason for the occurrence of springback of TRB during transverse bending. Annealing can eliminate nonuniform stress distribution, and thus diminish springbaek of TRB, especially springback on the thinner side. Therefore, springback of the whole TRB becomes more uniform. However, annealing can increase the TTZ movement. Blank thickness and TTZ position are the main factors affecting the formability of TRB U-channel during transverse bending.展开更多
In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation...In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation and stamping experiments.Fundamental theories of springback were analyzed.The stamping and springback processes of annealed 1.2 / 2.0mm TRB , 1.2mm and 2.0mm plates for U-channel were simulated , and the simulation results were compared with the experiments.The results indicate that the springback of TRB falls in between those of the 1.2mm and 2.0mm plates.It is desirable for the TRB U-channel to have die clearance of 1.1times maximum blank thickness and friction coefficient of about 0.12 , and longer thickness transition zone is preferable.The simulation data demonstrate reasonably good agreement with the experiments.展开更多
低截获概率(low probability of intercept,LPI)雷达信号凭借其卓越的抗截获能力,在现代电子战中得到了广泛应用。但LPI雷达信号的低峰值功率使其极易被加性白高斯噪声(additive white Gaussian noise,AWGN)淹没,导致信噪比(signal-to-n...低截获概率(low probability of intercept,LPI)雷达信号凭借其卓越的抗截获能力,在现代电子战中得到了广泛应用。但LPI雷达信号的低峰值功率使其极易被加性白高斯噪声(additive white Gaussian noise,AWGN)淹没,导致信噪比(signal-to-noise ratio,SNR)较低,给信号的检测和识别带来了极大的挑战。为了从AWGN背景中提取原始LPI雷达信号,本文提出了一种名为LPI-U-Net的深度神经网络(deep neural network,DNN),用于端到端的时域LPI雷达信号增强。该网络由特征提取模块(feature extract module,FEM)、特征聚焦模块(feature focus module,FFM)和信号恢复模块(signal recover module,SRM)组成。首先FEM通过卷积操作提取信号的特征,然后FFM利用卷积和通道间注意力进一步关注对信号增强任务有利的特征,最后SRM利用反卷积操作从特征中重构信号,从而完成LPI雷达信号增强。仿真实验表明LPI-U-Net在低SNR下的LPI雷达信号增强性能优于传统信号处理中典型的降噪方法,验证了其可行性和有效性。展开更多
基金Item Sponsored by National Natural Science Foundation of China(51475086)Natural Science Foundation of Hebei Province of China(E2016501118,E2015501073)China Postdoctoral Science Foundation(2016M591404)
文摘Research on the formability of tailor rolled blank （TRB） is of good practical significance and application value because of the enormous potential of TRB in the aspect of automobile lightweight. However, the forming of TRB is problematic because of the varying properties; especially, springback is a main challenge. The transverse bending （bending axis is perpendicular to the rolling direction） of TRB U channel was studied through simulation and experiment. The forming characteristics of TRB U channel during transverse bending were analyzed. The mechanisms of forming defects, including bending springback and thickness transition zone （TTZ） movement, were revealed. On this basis, effects of blank geometric parameters on springbaek and TTZ movement were discussed. The results indicate that springback and TTZ movement happen during transverse bending of TRB U-channel. Nonuni form stress distribution is the most fundamental reason for the occurrence of springback of TRB during transverse bending. Annealing can eliminate nonuniform stress distribution, and thus diminish springbaek of TRB, especially springback on the thinner side. Therefore, springback of the whole TRB becomes more uniform. However, annealing can increase the TTZ movement. Blank thickness and TTZ position are the main factors affecting the formability of TRB U-channel during transverse bending.
基金Item Sponsored by National Natural Science Foundation of China ( 10932003 , 50974039 , 50872126 )National Basic Research Program of China ( 2010CB832700 )Fundamental Research Funds for Central Universities of China ( 893324 , DUT11ZD202 )
文摘In order to grasp the springback rule of TRB ( tailor rolled blank ) parts after forming , the springback behavior of TRB was investigated by integrating such three means as theoretical research , numerical simulation and stamping experiments.Fundamental theories of springback were analyzed.The stamping and springback processes of annealed 1.2 / 2.0mm TRB , 1.2mm and 2.0mm plates for U-channel were simulated , and the simulation results were compared with the experiments.The results indicate that the springback of TRB falls in between those of the 1.2mm and 2.0mm plates.It is desirable for the TRB U-channel to have die clearance of 1.1times maximum blank thickness and friction coefficient of about 0.12 , and longer thickness transition zone is preferable.The simulation data demonstrate reasonably good agreement with the experiments.
