Electromagnetic forming(EMF)is a high-velocity manufacturing technique which uses electromagnetic(Lorentz)body forces to shape sheet metal parts.One of the several advantages of EMF is the considerable ductility incre...Electromagnetic forming(EMF)is a high-velocity manufacturing technique which uses electromagnetic(Lorentz)body forces to shape sheet metal parts.One of the several advantages of EMF is the considerable ductility increase observed in several metals,with aluminum featuring prominently among them.Electromagnetically assisted sheet metal stamping(EMAS)is an innovative hybrid sheet metal processing technique that combines EMF into traditional stamping.To evaluate the efficiency of this technique,an experimental scheme of EMAS was established according to the conventional stamping of cylindrical parts from aluminum and the formability encountered was discussed.Furthermore,a "multi-step,loose coupling" numerical scheme was proposed to investigate the deformation behaviors based on the ANSYS Multiphysics/LS-DYNA platform through establishing user-defined subroutines.The results show that electromagnetically assisted deep drawing can remarkably improve the formability of aluminum cylindrical parts.The proposed numerical scheme can successfully simulate the related Stamping-EMF process,and the deformation characteristics of sheet metal reflect experimental results.The predicted results are also validated with the profiles of the deformed sheets in experiments.展开更多
本文通过电磁发音仪(Electro Magnetic Articulography,EMA)AG500,以200帧/秒的采样率采集了英语和汉语的标准发音动作数据,然而,交叉语言比较的首要任务就是要消除特定说话人声道特性及其它个人生理特性等音素而引起的固有差别,本文采...本文通过电磁发音仪(Electro Magnetic Articulography,EMA)AG500,以200帧/秒的采样率采集了英语和汉语的标准发音动作数据,然而,交叉语言比较的首要任务就是要消除特定说话人声道特性及其它个人生理特性等音素而引起的固有差别,本文采用了基于说话人归一化的普氏算法来进行说话人归一化处理,获得了英汉相似音素发音的元音对比最小对,最后成功揭示了2种语言易混淆元音发音文本对在口腔内外发音动作上的区别。展开更多
An experimental study on the quasi-static-dynamic formability specified in electromagnetically assisted sheet metal stamping(EMAS)was presented.A series of uniaxial and plane-strain tensile experiments were carried ou...An experimental study on the quasi-static-dynamic formability specified in electromagnetically assisted sheet metal stamping(EMAS)was presented.A series of uniaxial and plane-strain tensile experiments were carried out on AA5052-O sheet by using a combined quasi-static stretching and pulsed electromagnetic forming(EMF)method.Failure strains representing formability beyond conventional quasi-static forming limits are observed under both uniaxial tensile and plane-strain states.The total forming limits of the as-received aluminum alloy undergoing both low and high quasi-static pre-straining are almost similar in quasi-static-dynamic deformation.Ultimate total formability seems to depend largely on the high-velocity loading conditions.Thus, it appears that for quasi-static-dynamic deformation,the quasi-static pre-straining of material is not of primary importance to the additionally useful formability.These observations will enable to develop forming operations that take advantage of this improvement in formability,and will also enable the use of a quasi-static preform fairly close to the quasi-static forming limits without weakening its total formability for design of an EMAS process in shaping large aluminum shell parts like auto body panels.展开更多
基金Project(50805036)supported by the National Natural Science Foundation of China
文摘Electromagnetic forming(EMF)is a high-velocity manufacturing technique which uses electromagnetic(Lorentz)body forces to shape sheet metal parts.One of the several advantages of EMF is the considerable ductility increase observed in several metals,with aluminum featuring prominently among them.Electromagnetically assisted sheet metal stamping(EMAS)is an innovative hybrid sheet metal processing technique that combines EMF into traditional stamping.To evaluate the efficiency of this technique,an experimental scheme of EMAS was established according to the conventional stamping of cylindrical parts from aluminum and the formability encountered was discussed.Furthermore,a "multi-step,loose coupling" numerical scheme was proposed to investigate the deformation behaviors based on the ANSYS Multiphysics/LS-DYNA platform through establishing user-defined subroutines.The results show that electromagnetically assisted deep drawing can remarkably improve the formability of aluminum cylindrical parts.The proposed numerical scheme can successfully simulate the related Stamping-EMF process,and the deformation characteristics of sheet metal reflect experimental results.The predicted results are also validated with the profiles of the deformed sheets in experiments.
文摘本文通过电磁发音仪(Electro Magnetic Articulography,EMA)AG500,以200帧/秒的采样率采集了英语和汉语的标准发音动作数据,然而,交叉语言比较的首要任务就是要消除特定说话人声道特性及其它个人生理特性等音素而引起的固有差别,本文采用了基于说话人归一化的普氏算法来进行说话人归一化处理,获得了英汉相似音素发音的元音对比最小对,最后成功揭示了2种语言易混淆元音发音文本对在口腔内外发音动作上的区别。
基金Project(50805036)supported by the National Natural Science Foundation of China。
文摘An experimental study on the quasi-static-dynamic formability specified in electromagnetically assisted sheet metal stamping(EMAS)was presented.A series of uniaxial and plane-strain tensile experiments were carried out on AA5052-O sheet by using a combined quasi-static stretching and pulsed electromagnetic forming(EMF)method.Failure strains representing formability beyond conventional quasi-static forming limits are observed under both uniaxial tensile and plane-strain states.The total forming limits of the as-received aluminum alloy undergoing both low and high quasi-static pre-straining are almost similar in quasi-static-dynamic deformation.Ultimate total formability seems to depend largely on the high-velocity loading conditions.Thus, it appears that for quasi-static-dynamic deformation,the quasi-static pre-straining of material is not of primary importance to the additionally useful formability.These observations will enable to develop forming operations that take advantage of this improvement in formability,and will also enable the use of a quasi-static preform fairly close to the quasi-static forming limits without weakening its total formability for design of an EMAS process in shaping large aluminum shell parts like auto body panels.
