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
A shear wave electromagnetic acoustic transducer(EMAT)optimized structure is proposed by using circumferential annular Halbach magnet structure.Based on the orthogonal test,the effects of the coil conductor width,the ...A shear wave electromagnetic acoustic transducer(EMAT)optimized structure is proposed by using circumferential annular Halbach magnet structure.Based on the orthogonal test,the effects of the coil conductor width,the spacing between adjacent conductors,the number of turns and the lifting distance on EMAT energy conversion effect are studied,and the optimal parameter combination is given.The structural design of the Halbach magnet is proposed.The cost coefficient S of the Halbach structure is defined,and the optimal thickness of auxiliary magnetic pole is obtained.The optimized EMAT coil diameter is reduced by 35%and the echo signal strength is significantly improved.Finally,C-scan imaging is carried out on the sample to verify the detection ability of EMAT.展开更多
Objective:The aim of this study was to investigate the biological effects of occupational extremely low-frequency electromagnetic field(ELF-EMF)exposure on the thyroid gland.Methods:We conducted a prospective analysis...Objective:The aim of this study was to investigate the biological effects of occupational extremely low-frequency electromagnetic field(ELF-EMF)exposure on the thyroid gland.Methods:We conducted a prospective analysis of 85 workers(exposure group)exposed to an ELF-EMF(100μT,10-100 Hz)produced by the electromagnetic aircraft launch system and followed up on thyroid function indices,immunological indices,and color Doppler images for 3 years.Additionally,116 healthy volunteers were randomly selected as controls(control group),the thyroid function of whom was compared to the exposure group.Results:No significant difference was observed in thyroid function between the exposure and control groups.During the follow-up of the exposure group,the serum free triiodothyronine(FT3)level was found to slowly decrease and free thyroxine(FT4)level slowly increase with increasing exposure time.However,no significant difference was found in thyroid-stimulating hormone(TSH)over the three years,and no significant difference was observed in the FT3,FT4 and TSH levels between different exposure subgroups.Furthermore,no significant changes were observed in thyroid autoantibody levels and ultrasound images between subgroups or over time.Conclusion:Long-term exposure to ELF-EMF may promote thyroid secretion of T4 and inhibit deiodination of T4 to T3.ELF-EMF has no significant effect on thyroid immune function and morphology.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A shear wave electromagnetic acoustic transducer(EMAT)optimized structure is proposed by using circumferential annular Halbach magnet structure.Based on the orthogonal test,the effects of the coil conductor width,the spacing between adjacent conductors,the number of turns and the lifting distance on EMAT energy conversion effect are studied,and the optimal parameter combination is given.The structural design of the Halbach magnet is proposed.The cost coefficient S of the Halbach structure is defined,and the optimal thickness of auxiliary magnetic pole is obtained.The optimized EMAT coil diameter is reduced by 35%and the echo signal strength is significantly improved.Finally,C-scan imaging is carried out on the sample to verify the detection ability of EMAT.
基金supported by.the National Military Research Project of China(No.JGXM201507).
文摘Objective:The aim of this study was to investigate the biological effects of occupational extremely low-frequency electromagnetic field(ELF-EMF)exposure on the thyroid gland.Methods:We conducted a prospective analysis of 85 workers(exposure group)exposed to an ELF-EMF(100μT,10-100 Hz)produced by the electromagnetic aircraft launch system and followed up on thyroid function indices,immunological indices,and color Doppler images for 3 years.Additionally,116 healthy volunteers were randomly selected as controls(control group),the thyroid function of whom was compared to the exposure group.Results:No significant difference was observed in thyroid function between the exposure and control groups.During the follow-up of the exposure group,the serum free triiodothyronine(FT3)level was found to slowly decrease and free thyroxine(FT4)level slowly increase with increasing exposure time.However,no significant difference was found in thyroid-stimulating hormone(TSH)over the three years,and no significant difference was observed in the FT3,FT4 and TSH levels between different exposure subgroups.Furthermore,no significant changes were observed in thyroid autoantibody levels and ultrasound images between subgroups or over time.Conclusion:Long-term exposure to ELF-EMF may promote thyroid secretion of T4 and inhibit deiodination of T4 to T3.ELF-EMF has no significant effect on thyroid immune function and morphology.
