An improvement of automatic ultrasonic testing through a double probe technique along the longitudinal bar axis used in a round bar, with a diameter of several millimeters, is proposed. Non-metallic inclusions of several tens of micrometers in the cross-sectional length can be detected using this novel technique, whereas the detectability in a conventional normal beam technique is limited to 100–150 µm. The main advantages of this technique are an increased working sensitivity owing to a decreased surface echo width and the use of a shear wave with a shorter wavelength as compared with a conventional normal beam technique. As another advantage of this technique, malfunctions caused by air bubbles in the coupling medium can be eliminated. Further, the beam paths of the surface echo and the bottom echo are discussed herein using the propagation time difference between both echoes in Appendix.

提出了一种改进的自动超声测试方法，该技术通过沿直径为几毫米的圆棒中沿棒的纵向棒轴使用双探针技术进行。可以使用这种新技术检测横截面长度为几十微米的非金属夹杂物，而常规法线束技术的可检测性仅限于100-150 µm。与常规法线束技术相比，该技术的主要优点是由于减小了表面回波宽度而提高了工作灵敏度，并使用了波长较短的切波。作为该技术的另一个优点，可以消除由耦合介质中的气泡引起的故障。进一步，