Definition of ultrasonic testing:

Ultrasonic testing is one of the industrial nondestructive testing methods. When ultrasonic waves enter an object and encounter defects, some sound waves will be reflected, and the receiver can analyze the reflected waves, so as to detect the defects extremely accurately, display the position and size of the internal defects, and determine the thickness of the material.

Principle of ultrasonic flaw detection:

1. Ultrasonic wave is a mechanical wave with a frequency higher than 20 kHz. The common frequency of ultrasonic flaw detection is 0.5~ 10 MHz. This kind of mechanical wave can propagate in the material at a certain speed and direction, and it will be reflected, refracted and converted when it meets the non-uniform interface with different acoustic impedance (such as defects or the bottom of the measured object).

2. This phenomenon can be used for ultrasonic flaw detection, and pulse reflection method is the most commonly used method. During flaw detection, the voltage emitted by the pulse oscillator is applied to the probe, and the ultrasonic pulse emitted by the probe enters the material through the acoustic coupling medium and propagates in it. After encountering defects, part of the reflected energy returns to the probe in the original way, and the probe converts it into electric pulses, which are amplified by the instrument and displayed on the screen of the oscilloscope tube.

Advantages and disadvantages of ultrasonic testing and its application;

Advantages and disadvantages of ultrasonic testing:

1, advantages of ultrasonic testing:

The penetration ability is large, such as the effective detection depth in steel can reach more than 1 m; For plane defects such as cracks and interlayers, the detection sensitivity is high, and the depth and relative size of defects can be determined. The equipment is easy to carry, safe to operate and easy to realize automatic detection.

2. Disadvantages of ultrasonic testing method:

It is difficult to detect workpieces with complex shapes. The surface to be detected should have a certain smoothness, and the gap between the probe and the surface to be detected should be filled with coupling agent to ensure sufficient acoustic coupling. For some coarse-grained castings and welds, it is difficult to apply because it is easy to produce chaotic reflected waves.

Second, the application of ultrasonic testing:

Ultrasonic testing is usually used to detect forgings, welds, etc. Small cracks, slag inclusion, shrinkage cavity and incomplete penetration can be found in the workpiece. The object to be detected requires a simple shape and a certain smoothness of the surface. In order to quickly detect pipes, bars, steel plates and other profiles in batches, an ultrasonic flaw detection system equipped with mechanical transmission, automatic alarm, marking and sorting devices can be adopted.