1. Eddy current testing. There are many forms of eddy current testing, commonly used are conventional eddy current testing, far-field eddy current testing, multi-frequency eddy current testing and pulse eddy current testing, etc., the use of eddy current sensors to induce metal, different defect types and shapes on the surface of the square tube will produce different types of signals. Its advantages are high detection accuracy, high detection sensitivity, fast detection speed, can detect the surface and subsurface of the pipe to be detected, and is not affected by impurities such as oil stain on the surface of the square pipe to be detected. The disadvantage is that it is easy to judge the non-defective structure as a defect, the false detection rate is high, and the detection resolution is not easy to adjust.
2. When the ultrasonic wave enters the object and encounters a defect, a part of the sound wave will be reflected, and the transmitter and receiver can analyze the reflected wave to detect the defect with extraordinary accuracy. Ultrasonic testing is often used in forging detection, and the detection and flaw detection sensitivity is high, but it is not easy to inspect the pipe with complex shapes, and the surface of the square tube to be inspected is required to have a certain finish, and the couplant needs to fill the gap between the probe and the inspected surface.
