Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or...Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or minimum plastic work path), the concept of an optimum forming path is proposed in this paper. The forming path can be described by the initial configuration, objective configuration and a series of intermediate configurations. According to the deformation theory and constitutive equation in ideal path forming, a finite element method to calculate the initial configuration is set up. The functional to determinate intermediate configurations is introduced and the numerical method to solve the configuration is presented. Based on the method presented in the paper, multi-step multi-point forming tests for sheet metal are designed. The test results demonstrate that when the sheet is deformed along an approximate optimum forming path, the maximum deformation curvature for the sphere objective shape and saddle objective shape are 11%∼40% and 15%∼50% greater than those of a sheet deformed along a common path respectively.展开更多
The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation too...The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.展开更多
A series of bias extension tests was carried out on balanced plain woven composite preforms with various aspect ratios, disclosing that different aspect ratios may result in differ- ent initial failures. An energy met...A series of bias extension tests was carried out on balanced plain woven composite preforms with various aspect ratios, disclosing that different aspect ratios may result in differ- ent initial failures. An energy method is adopted to quantify several deformation modes. By the competition of the required energies, the initial failure is predicted, showing a good accordance with the experimental observation. The results of the present research are valuable for the further understanding of the material＇s behaviour in bias extension test. It also provides an effective way for modelling the material＇s formability in other more complicated forming processes.展开更多
Owing to their excellent mechanical flexibility, electrical conductivity, and biocompatibility, conductive hydrogels(CHs) are widely used in the fields of energy and power, and biomedical technology. To arrive at a be...Owing to their excellent mechanical flexibility, electrical conductivity, and biocompatibility, conductive hydrogels(CHs) are widely used in the fields of energy and power, and biomedical technology. To arrive at a better understanding of the design methods and development trends of CHs, this paper summarizes and analyzes related research published in recent years. First,we describe the properties and characteristics of CHs. Using Scopus, the world’s largest abstract and citation database, we conducted a quantitative analysis of the related literature from the past 15 years and summarized development trends in the field of CHs. Second, we describe the types of CH network crosslinking and basic functional design methods and summarize the three-dimensional(3D) structure-forming methods and conductive performance tests of CHs. In addition, we introduce applications of CHs in the fields of energy and power, biomedical technology, and others. Lastly, we discuss several problems in current CH research and introduce some prospects for the future development of CHs.展开更多
The number of wireless electronic gadgets used in mobile communication, vehicle collision avoidance system, compact radars, etc. is extremely increasing at a rapid rate. Thus, the characteristics of the antennas invol...The number of wireless electronic gadgets used in mobile communication, vehicle collision avoidance system, compact radars, etc. is extremely increasing at a rapid rate. Thus, the characteristics of the antennas involved in these gadgets are to be designed very stringently so as to avoid interferences & coupling and to improve compatibility, susceptibility, etc. Compact smart antenna with improved performance is highly essential to meet this challenging scenario. Mutual coupling between various elements of an array is one of the main factors which can be considered for improvement of performance of the antenna. Influence of mutual coupling on performance of the antenna is considered in this paper and various techniques to minimize this effect are presented. Effect of mutual coupling on radiation characteristics of the antenna can be compensated employing various methods like Conventional Mutual Impedance (CMI), Receiving Mutual Impedance (RMI). Analysis is presented as comparison between the two methods for different number of elements in the array. Analysis is also presented for different geometries of the array like circular and elliptical for improved performance. The results show performance improvement in the proposed array for parameters like SNR and Speed of convergence.展开更多
文摘Ideal forming results will be achieved if the sheet metal is formed along an optimum forming path. Such a path can be realized by multi-point forming technique. On the basis of the theory of the ideal forming path (or minimum plastic work path), the concept of an optimum forming path is proposed in this paper. The forming path can be described by the initial configuration, objective configuration and a series of intermediate configurations. According to the deformation theory and constitutive equation in ideal path forming, a finite element method to calculate the initial configuration is set up. The functional to determinate intermediate configurations is introduced and the numerical method to solve the configuration is presented. Based on the method presented in the paper, multi-step multi-point forming tests for sheet metal are designed. The test results demonstrate that when the sheet is deformed along an approximate optimum forming path, the maximum deformation curvature for the sphere objective shape and saddle objective shape are 11%∼40% and 15%∼50% greater than those of a sheet deformed along a common path respectively.
文摘The paper starts with a brief overview to the necessity of sheet metal forming simulation and the complexity of automobile panel forming, then leads to finite element analysis (FEA) which is a powerful simulation tool for analyzing complex three-dimensional sheet metal forming problems. The theory and features of the dynamic explicit finite element methods are introduced and the available various commercial finite element method codes used for sheet metal forming simulation in the world are discussed,and the civil and international status quo of automobile panel simulation as well. The front door outer panel of one certain new automobile is regarded as one example that the dynamic explicit FEM code Dynaform is used for the simulation of the front door outer panel forming process. Process defects such as ruptures are predicted. The improving methods can be given according to the simulation results. Foreground of sheet metal forming simulation is outlined.
文摘A series of bias extension tests was carried out on balanced plain woven composite preforms with various aspect ratios, disclosing that different aspect ratios may result in differ- ent initial failures. An energy method is adopted to quantify several deformation modes. By the competition of the required energies, the initial failure is predicted, showing a good accordance with the experimental observation. The results of the present research are valuable for the further understanding of the material＇s behaviour in bias extension test. It also provides an effective way for modelling the material＇s formability in other more complicated forming processes.
基金supported by the Research Project Funding of National University of Defense Technology of China (No.ZK19-33)the National Postdoctoral International Exchange Program Funding for Incoming Postdoctoral Students (Postdoctoral No.48127)+1 种基金the Science and Technology Innovation Program of Hunan Province (No.2020RC2036)the National Natural Science Foundation of China (Nos.52105039 and 52175069)。
文摘Owing to their excellent mechanical flexibility, electrical conductivity, and biocompatibility, conductive hydrogels(CHs) are widely used in the fields of energy and power, and biomedical technology. To arrive at a better understanding of the design methods and development trends of CHs, this paper summarizes and analyzes related research published in recent years. First,we describe the properties and characteristics of CHs. Using Scopus, the world’s largest abstract and citation database, we conducted a quantitative analysis of the related literature from the past 15 years and summarized development trends in the field of CHs. Second, we describe the types of CH network crosslinking and basic functional design methods and summarize the three-dimensional(3D) structure-forming methods and conductive performance tests of CHs. In addition, we introduce applications of CHs in the fields of energy and power, biomedical technology, and others. Lastly, we discuss several problems in current CH research and introduce some prospects for the future development of CHs.
文摘The number of wireless electronic gadgets used in mobile communication, vehicle collision avoidance system, compact radars, etc. is extremely increasing at a rapid rate. Thus, the characteristics of the antennas involved in these gadgets are to be designed very stringently so as to avoid interferences & coupling and to improve compatibility, susceptibility, etc. Compact smart antenna with improved performance is highly essential to meet this challenging scenario. Mutual coupling between various elements of an array is one of the main factors which can be considered for improvement of performance of the antenna. Influence of mutual coupling on performance of the antenna is considered in this paper and various techniques to minimize this effect are presented. Effect of mutual coupling on radiation characteristics of the antenna can be compensated employing various methods like Conventional Mutual Impedance (CMI), Receiving Mutual Impedance (RMI). Analysis is presented as comparison between the two methods for different number of elements in the array. Analysis is also presented for different geometries of the array like circular and elliptical for improved performance. The results show performance improvement in the proposed array for parameters like SNR and Speed of convergence.
