Power source of electromagnetically induced acoustic emission based on DDS

Electromagnetically induced acoustic emission (EMAE) technology is 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 high current to stimulate acoustic emission (AE). The technique of AE induced by eddy current 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.