A magnetoelectric-ultrasonic multimodal system for synchronous NDE of surface and internal defects in metal

In the field of non-destructive evaluation (NDE) of solid metal materials, it has been a challenge to detect surface and internal defects simultaneously by using a single physical mechanism technique. Conventionally, different testing techniques, in which each one is particularly sensitive to a certain type of defect, are employed to gain full defect information. However, a separated testing method is always a time-consuming and laborious work. Here, we report a magnetoelectric-ultrasonic hybrid transducer and multimodal system for quantitative NDE of metal, which integrates a magnetoelectric composite wrapped with a coil for generating alternating current field and simultaneously measuring magnetic abnormal of surface defects (referred to as ME-ACFM) and a dual-piezoceramic ultrasonic transducer (DP-UT) for generating acoustic pulses and detecting the echo signal of internal defects, respectively. A bipulse signal with different pulse widths is used for excitation of the hybrid transducer, in which one is corresponded to the resonant frequencies of 5 MHz for DP-UT, and another to 122 kHz for ME-ACFM. The huge difference between two resonant frequencies is helpful for restraining signal interference each other. Experimental investigations show that when scanning the tested specimens (standard steel No.45 and aluminum plates), the surface and internal defects information can be obtained simultaneously almost without a dead zone. The surface defect resolutions of 0.1 mm width and 0.1 mm depth, and the inside defect resolution of 2 mm blind hole are obtained; the experimental errors for surface defect (crack) depth up to 5 mm are around 5 %; while experimental errors for ultrasonic depth measurement (with a blind zone of 1.25 mm) is less than 0.63 mm. The proposed hybrid transducer and multimodal system open up a new way for designing multi-physical mechanism based NDEs.