Shipbuilding
Eddy current flaw detection is a flaw detection method that uses the principle of electromagnetic induction to detect surface defects of components and metal materials. The detection method is the detection coil and its classification and the structure of the detection coil.
The advantages of eddy current flaw detection for seamless tubes are: the flaw detection results can be directly output by electrical signals, which is convenient for automatic detection; due to the non-contact method, the flaw detection speed is very fast; it is suitable for flaw detection of surface defects. The disadvantages are: the defects in the deeper parts under the surface of the seamless steel tube cannot be detected; it is easy to generate messy signals; it is difficult to directly distinguish the type of defects from the displayed signals obtained through detection.
In addition, alternating current changes the direction of the current at a certain frequency over time. There is a certain difference in the phase of the excitation current and the reaction current, and this phase difference changes with the shape of the test piece, so this phase change can also be used as a piece of information to detect the state of the seamless steel tube test piece. Therefore, when the test piece or coil is moved at a certain speed, the type, shape and size of steel pipe defects can be known according to the waveform of the eddy current change. The alternating current generated by the oscillator is passed into the coil, and the alternating magnetic field is applied to the test piece. The eddy current of the test piece is detected by the coil and sent to the bridge circuit as an AC output.
