Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the defo...Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.展开更多
Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge bas...Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge base in a fault diagnosis expert system that was based on machine learning by the four-layer perceptron neural network. An example was presented. By combining differential function with not differential function and back propagation of error with back propagation of expectation, the four-layer perceptron neural network was established. And it was good for solving such a bottleneck problem in knowledge acquisition in expert system and enhancing real-time on-line diagnosis. A method of synthetic back propagation was designed, which broke the limit to non-differentiable function in BP neural network.展开更多
To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematic...To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematical and physical model to simulate flow and heat transfer in the laser welding molten pool of tin-coated copper used in solar panel busbars(a thin strip or wire of conductive metal embedded on the surface of a solar cell to collect and conduct the electricity generated by the photovoltaic cell).The model incorporates key external forces,including surface tension,solid-liquid interface tension,and recoil pressure.A moving and rotating Gaussian-body heat source is adopted,with temperature treated as an implicit function of enthalpy.Coupled iterative schemes for the temperature and velocity fields are constructed using a dual-distribution function approach with a D3Q15 lattice structure.The model is implemented in Python,utilizing libraries such as NumPy,SciPy,Mayavi,and Matplotlib for computation and visualization.Simulation results reveal that the heat transfer mechanism in the molten pool transitions from pure conduction to conduction-convection due to surface tension effects,leading to the formation of multiple counter-rotating vortex structures.The peak temperature at the pool center reaches 3200 K,with maximum melt depth and width measured at 0.5 and 1.2 mm,respectively.Over time,both penetration depth and melt width increase,though the width exhibits a more pronounced growth.Comparison with experimental thermal cycling data from laser weld joints shows strong agreement,with a maximum error of less than 1%,validating the accuracy of the proposed method.展开更多
为保证封闭母线运行时绝缘性能可靠,需要定期对其进行预防性试验。结合某水电站20 k V封闭母线交流耐压试验,介绍了封闭母线串联谐振耐压试验的原理及方法,根据试验过程中声光现象和电压、绝缘电阻测量值,判断封闭母线是否存在缺陷及缺...为保证封闭母线运行时绝缘性能可靠,需要定期对其进行预防性试验。结合某水电站20 k V封闭母线交流耐压试验,介绍了封闭母线串联谐振耐压试验的原理及方法,根据试验过程中声光现象和电压、绝缘电阻测量值,判断封闭母线是否存在缺陷及缺陷的具体位置。针对缺陷原因,进行相应处理。展开更多
基金the funds of the National Natural Science Foundation of China(No.51875456)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JM-450)+3 种基金the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20170518)the Key Laboratory of Advanced Manufacture Technology for Automobile Parts(Chongqing University of Technology),Ministry of Education(No.2018KLMT03)Materials Science and Engineering provincial-level superior discipline funding project of Xi'an Shiyou Universitythe Program for Young Innovative Research Team in Xi'an Shiyou University(No.2015QNKYCXTD02)。
文摘Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.
文摘Owing to continuous production lines with large amount of consecutive controls, various control signals and huge logistic relations, this paper introduced the methods and principles of the development of knowledge base in a fault diagnosis expert system that was based on machine learning by the four-layer perceptron neural network. An example was presented. By combining differential function with not differential function and back propagation of error with back propagation of expectation, the four-layer perceptron neural network was established. And it was good for solving such a bottleneck problem in knowledge acquisition in expert system and enhancing real-time on-line diagnosis. A method of synthetic back propagation was designed, which broke the limit to non-differentiable function in BP neural network.
基金Science and Technology Research Key Competitive Project of Quzhou Science and Technology Bureau(Nos.2023K266,2024K010)General Project for Cultivating Outstanding Young Teachers in Anhui Province’s Universities(2025).
文摘To address the limitations of traditional finite element methods,particularly the continuum assumption and difficulties in tracking the solid-liquid interface,this study introduces a lattice Boltzmann-based mathematical and physical model to simulate flow and heat transfer in the laser welding molten pool of tin-coated copper used in solar panel busbars(a thin strip or wire of conductive metal embedded on the surface of a solar cell to collect and conduct the electricity generated by the photovoltaic cell).The model incorporates key external forces,including surface tension,solid-liquid interface tension,and recoil pressure.A moving and rotating Gaussian-body heat source is adopted,with temperature treated as an implicit function of enthalpy.Coupled iterative schemes for the temperature and velocity fields are constructed using a dual-distribution function approach with a D3Q15 lattice structure.The model is implemented in Python,utilizing libraries such as NumPy,SciPy,Mayavi,and Matplotlib for computation and visualization.Simulation results reveal that the heat transfer mechanism in the molten pool transitions from pure conduction to conduction-convection due to surface tension effects,leading to the formation of multiple counter-rotating vortex structures.The peak temperature at the pool center reaches 3200 K,with maximum melt depth and width measured at 0.5 and 1.2 mm,respectively.Over time,both penetration depth and melt width increase,though the width exhibits a more pronounced growth.Comparison with experimental thermal cycling data from laser weld joints shows strong agreement,with a maximum error of less than 1%,validating the accuracy of the proposed method.
