1. Eddy current testing. There are many forms of eddy current testing. Commonly used ones include conventional eddy current testing, far-field eddy current testing, multi-frequency eddy current testing and pulsed eddy current testing. Eddy current sensors are used to sense metal. Different types and shapes of defects on the surface of square tubes will produce different type of signal. Its advantages are high detection accuracy, high detection sensitivity and fast detection speed. It can detect the surface and sub-surface of the pipe to be inspected and is not affected by impurities such as oil stains on the surface of the square pipe to be inspected. The disadvantage is that it is easy to judge non-defective structures as defects, the false detection rate is high, and the detection resolution is not easy to adjust.
2. When ultrasonic waves are used to enter an object and encounter defects, part of the sound waves will be reflected. The transmitter and receiver can analyze the reflected waves, and the defects can be measured extremely accurately. Ultrasonic testing is often used for forging inspection. The detection sensitivity is high, but it is not easy to inspect pipes with complex shapes. The surface of the square pipe to be inspected is required to have a certain smoothness, and the coupling agent needs to be filled to fill the gap between the probe and the surface to be inspected.
