中文摘要：

为了建立一个描述任意脉冲磁场下电磁力特性的数学模型,利用数学解析法推导建立任意波形周期脉冲电磁力的模型和理论解。利用此模型考察了三角脉冲磁场下电磁场和电磁力周期变化规律、脉冲频率、占空比和静磁场对电磁力的影响。结果表明：任意波形周期脉冲磁场可通过时谐场叠加得到,各个时谐场的频率为基频的整数倍。三角脉冲电磁力方向呈现交替变化,并且其电磁压力绝对值大于电磁拉力。在脉冲磁场某时间段内,介质内部同时存在电磁拉力和电磁压力。随着脉冲频率增大或占空比减小,电磁压力与电磁拉力都增大,但是电磁压力增幅远大于电磁拉力。随着静磁场感应强度增大,脉冲电磁力增大同时作用深度也增加。枝晶破碎是脉冲磁场细化晶粒组织的机理之一,枝晶在交替变化的脉冲电磁力作用下,可视作产生疲劳损伤,因此脉冲磁场电磁力特性能够增加枝晶破碎的几率。一方面可以通过设计调整脉冲频率、占空比和静磁场获得满足细化凝固晶粒组织所需电磁力；另一方面当脉冲电磁力足以使枝晶破碎时,降低脉冲频率或增大占空比,以便脉冲电磁力作用深度大,从而使凝固细化作用效果更佳。

英文摘要：

In order to build common model,which can descript electromagnetic force under arbitrary pulse electromagnetic field,the model and theoretical solution of arbitrary cycle pulse electromagnetic force were carried out through mathematical analysis.Under the triangular pulse magnetic field,variation of the electromagnetic force with pulse frequency,duty cycle and static magnetic field was investigated using the model.The results show that superposition of harmonic magnetic field can get arbitrary pulsed magnetic field,whose frequency is the integer multiple of fundamental frequency.The direction of electromagnetic force changes once,and pressure force is greater than pull force in a period under triangular pulse magnetic field.There are sometime pressure force and pull force at the same time Pulse electromagnetic force can evidently become stronger with increasing pulse frequency,but become weaker by increasing duty cycle.Application of the static magnetic field increases magnitude of electromagnetic force and promotes effect depth of force.The dendrites broken is as one mechanism of grain refinement of pulsed magnetic field.The dendrite broken under pulse magnetic field can be considered as fatigue damage processing.So the rate of dendrite broken can be increased under alternate electromagnetic force.On the one hand adjusting pulse frequency /duty cycle or static magnetic field can acquire electromagnetic force which can break dendrite of grain,on the other hand pulse frequency should be as lower as possible or pulse duty should be as larger as possible under the premise that dendrites can be broken under pulse electromagnetic force,so that penetration depth of the electromagnetic force is larger and effect of grain refinement is better.