基于DDS技术的电磁声发射涡流加载电源

Power Source of Electromagnetically Induced Acoustic Emission Based on DDS

电磁声发射技术是一种新型的无损检测技术,通过对导电部件进行电磁加载产生洛仑兹力,进而激发声发射效应,并通过这个效应来进行无损检测。传统的电磁声发射技术使用电极直接加载的方式引入电磁激励,存在激励电流过高、加载不方便等缺点。本文使用电磁线圈引入电磁激励,利用电磁线圈激发的瞬时电磁场加载在缺陷处,激发缺陷自身产生声发射信号,以提高对金属薄板中微细缺陷的检测能力。针对电磁声发射技术要求电源的输出功率较大、输出脉冲数可以调整并且电路的输出频率变化较大的特点,本文设计了一种基于直接数字频率合成技术的新型涡流激励电源。该电源主要包括信号产生、功率放大、串联谐振三部分,其中控制电路为核心部分。实验结果证明,该系统工作稳定,参数调节方便,能够满足电磁声发射检测对激励源提出的要求。

Electromagnetically induced acoustic emission （ISMAIS） tecnnology lS a new type of nondestructive test （NDT） techniques, which does nondestructive detection with the effect of dynamic electromagnetic loading to generate a stress field stimulating stress waves from the defects. The traditional EMAE uses the direct loading to introduce the electromagnetic stimulation. But the direct loading method is not convenient and needs very technique of AE induced by eddy current high current to stimulate acoustic emission （AE）. The introduces the electromagnetic stimulation by an electromagnetic coil. The defect itself can generate acoustic emission signals, which could be used to boost the detection ability of small cracks in the thin-walled metallic structures. In order to satisfy the requirement of EMAE testing, such as high power output, pulse counts adjusting and the frequency of the output in wide range, a new power source based on direct digital synthesis （DDS） was designed. The power source included signal generating, power amplifying and series resonance, which the control circuit was the core part. Experiments＇ results show that the system can satisfy requirement of the EMAE testing with the merits of outstanding stability and flexible parameter adjustment.