高频电磁力作用下金属液内电磁超声波的生成

为解决由机械振动产生的超声波无法在高温环境中成功应用的难题，提出了利用静磁场和交流电流、静磁场和交流磁场的相互作用分别在金属液内直接生成高强度电磁超声波的方法，运用超声波压力传感器对用这两种方法在金属液内生成的电磁超声波的强度进行了测量。研究表明：电磁超声波的强度与所施加的高频电磁力的强度成正比，频率与电磁力的频率相同；实验结果和理论解析结果基本一致；利用高频电磁力的局部作用在金属液全场范围内生成的电磁超声波可以在金属精炼及凝固过程中获得广泛应用。

Generation of electromagnetic ultrasonic waves in liquid metal under high frequency electromagnetic forces

In order to overcome the difficulties that occur when ultrasonic waves excited by mechanical vibration method applied to metallurgical processes of materials, two electromagnetic methods are proposed to generate intense ultrasonic waves directly in liquid metal in this study. One is the simultaneous imposition of a high frequency electrical current and a static magnetic field; the other is that of a high frequency magnetic field and a static one. A mathematical model based on compressible fluid dynamics and electromagnetic fields theory has been developed to derive the pressure distribution of the generated waves in a metal. It is show that the intensities of the electromagnetic ultrasonic waves are proportional to the product of the static magnetic field and the alternating current of the static and alternating magnetic fields respectively. And the frequency is the same with that of the imposed electromagnetic force. On basis of the theoretical analysis, the pressure changes in a liquid gallium were examined by a pressure transducer under different conditions. The observed results approximately agreed with the prediction derived from the theoretical analysis and calculations. This study shows that electromagnetic ultrasonic waves can be generated in a liquid metal by imposing a high frequency force locally on it and these waves can be used in the refining and solidifying processes of metals.