What is the scope of application for ultrasonic non-destructive testing?

You can take a look at NB/T47013-2015.

1. Definition of ultrasonic testing: A technique that involves using ultrasonic waves to interact with the test specimen, studying the reflected, transmitted, and scattered waves, in order to detect macroscopic defects, measure geometric properties, assess changes in the structural organization and mechanical properties of the specimen, and thereby evaluate its suitability for specific applications. 2. Principle of ultrasonic operation: It is mainly based on the propagation characteristics of ultrasonic waves within the test specimen. a. The sound source generates ultrasonic waves, which are then directed into the test specimen in a certain manner; b. The ultrasonic waves propagate through the specimen and interact with the material of the specimen as well as any defects present therein, causing changes in their direction or properties; c. The altered ultrasonic waves are detected by monitoring equipment, where they can be processed and analyzed; d. Based on the characteristics of the detected ultrasonic waves, it is possible to assess the specimen itself and determine whether there are any defects within it, as well as the nature of those defects. 3. Advantages of ultrasonic testing: a. It is suitable for non-destructive testing of various materials such as metals, non-metals, and composite materials; b. It has strong penetration capability, allowing the detection of internal defects in specimens with relatively large thicknesses. For metal materials, it can detect thin-walled tubes and sheets with a thickness of 1–2 mm, as well as steel forgings several meters long; c. Defect location is relatively accurate; d. It has a high detection rate for area-type defects; e. It has high sensitivity, enabling the detection of defects with very small sizes inside the test specimen; f. The inspection cost is low, the speed is fast, the equipment is lightweight, it is harmless to humans and the environment, making it convenient for use on-site. 4. Limitations of ultrasonic testing: a. Further research is needed to achieve accurate qualitative and quantitative assessment of defects in the test specimens; b. It is difficult to perform ultrasonic testing on specimens with complex shapes or irregular outlines; c. The location, orientation, and shape of defects have an impact on the test results; d. Material properties and grain size have a significant influence on the testing process; e. When using the conventional manual A-mode pulse reflection method, the test results are not intuitive, and there is no direct record of the test outcomes. 5. Scope of application for ultrasonic testing: a. In terms of the material of the object to be inspected, it can be used for metals, non-metals, and composite materials; b. In terms of the manufacturing process of the object, it can be applied to forgings, castings, welded parts, bonded parts, etc.; c. In terms of the shape of the object, it can be used for sheets, bars, tubes, etc.; d. In terms of the size of the object, the thickness can range from as little as 1 mm to several meters; e. In terms of the location of defects, they can be either surface defects or internal defects.

Ultrasound examination is one of the four traditional diagnostic methods, but it has limitations. Generally, the detection accuracy is poor for values below 6 mm.