| The brazing technology is widely used in the national defense,automobile manufacturing,aeronautical,aerospace,and microelectronics packaging fields.The traditional solder metals usually contain the harmful elements of cadmium and lead to improve the welding and preparation properties.It is not beneficial for the environmental demand of sustainable development,so the research and application of the environmental solder metals without cadmium and lead elements have been widely concerned and highly regarded.When the environmental solder sheet metals are prepared by the traditional methods,much alloyed brittle phase will generate.It results in very bad formability and it is very hard to produce thin sheets.Because of this,our team has suggested the preparation process of powder electromagnetic pressing and sintering to avoid the problem that it is difficult for the subsequent forming process after alloying by the traditional methods.For the new preparation process,the welding property of solder metals is affected by the density of powder electromagnetic pressing.The coil and amplifier are two critical issues to affect the density of powder electromagnetic pressing,so it is necessary to comprehensively study the effect of coil and amplifier on the electromagnetic pressing process in order to increase the density of pressed powder,improve the propertied of solder metals,and provide the theoretical fundamentals for the optimal design of electromagnetic pressing device.In this thesis,the research status of the silver-based solder metals,the electromagnetic forming technology and coil and amplifier has been presented at first;the main forms of coil in the electromagnetic forming and the basic theory of electromagnetic field analysis have been introduced,the electromagnetic field analysis model of the flat spiral coil has been established for by the finite element software of ANSYS,it is concluded that the stress of the flat spiral coil is biggest in the half of radius,and gradually becoming smaller with the spreading distance;for the nonlinear effects of the coil cross section size proportion,the distance between the drive and coil,the coil turn spacing,the ratio of coil size and drive duration on the driving impulse,the approximate model is established on basis of BP neural network;the effects of the above-mentioned coil structure parameters on the driving impulse have been analyzed,these parameters have been optimized by using particle swarm algorithm,the result shows that when the coil section size ratio is 2.4,the distance between the drive and coil is 1.2 mm,the coil turn spacing is 0.7 mm,the size of the coil and drive ratio is 0.5,and the action time is 3?10??s,the driving impulse is largest;the finite element model has been established for the electromagnetic forming process,the driving force in the electromagnetic field analysis has been mapped to the electromagnetic pressing process simulation,the effect of the different amplifier angles on the electromagnetic pressing process has been analyzed,the loading condition of the pressing punch have been discussed for the amplifier with different angles,it is concluded that when the amplifier angle is45°,the energy of punch is largest and it is beneficial for powder pressing. |
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