Bicrystal Probes and RF Methods of Inspection

In NDT, bicrystal probe is a common tool which consists of two longitudinal wave wafers or two transverse wave wafers and is called longitudinal wave bicrystal probe or transverse wave bicrystal probe. Due to its high transmitting and receiving sensitivity,probe test system bicrystal probes have a wide range of applications in flaw detection.

Generally speaking, a probe with two wafers in the probe housing is called a bicrystal probe, also known as a split probe. The bicrystal probe synthesized by two longitudinal wave wafers is called longitudinal wave bicrystal probe, also known as bicrystal straight probe; bicrystal probe composed of two transverse wave wafers is called transverse wave bicrystal probe, also known as bicrystal slant probe. Among these two kinds of bicrystal probes, bicrystal straight probes are more widely used.

Specifically, the two longitudinal wave wafers of the bicrystal straight probe are used for transmitting ultrasound and one for receiving ultrasound. Most of the transmitting piezoelectric wafers are lead zirconate titanate with good transmitting performance, and most of the receiving piezoelectric wafers are lithium sulfate with good receiving performance. In contrast to single-crystal probes, bicrystal probes have higher transmit and receive sensitivities.RF probes In addition, between the two wafers of the bicrystalline probe there is a sound-absorbing, insulating sound insulation layer, which is not only used to overcome the emission of sound beams and reflection of sound beams of mutual interference and blockage, but also to make the pulse narrower, improve the resolution, eliminating the emission of the wafer and the delay block of the reflection of the wavelength between the wavelengths of the wavelengths of the receiving wavelengths, and effectively reduce the clutter.

When utilizing the bicrystal probe for flaw detection, it is necessary to correctly select and use the bicrystal probe. First, the choice of probe frequency is an important factor. Generally speaking, the emission frequency of ultrasound largely determines the detection capability of ultrasonic flaw detection. For different kinds of materials and workpieces, it is necessary to choose the appropriate frequency of the probe according to the actual situation. Secondly,probe card the choice of wafer size is also a key factor. The wafer size of the bicrystalline probe is only related to the size of the detection area of the workpiece, when the detection area is large, in order to improve the detection efficiency, it is desirable to use a larger wafer size probe; on the contrary, when the detection area is small or the detection surface with a certain degree of curvature, it is desirable to use a small wafer size probe in order to reduce the loss of coupling. Finally, the choice of focal length is also very important. The two wafers of the bicrystalline probe have a certain tilt angle, so it is necessary to select the appropriate focal length according to the thickness of the inspected workpiece.