Ultrasonic Flaw Detector Theory: Reflection Method

Ultrasonic flaw detector is a type of non-destructive testing tool widely used to detect internal defects in objects such as cracks, pores, looseness, inclusions, etc. Its working principle is based on the changes that occur when ultrasound propagates through an object, influenced by the object's material and structure. Common ultrasonic flaw detection methods include the Doppler effect method, transmission method, and reflection method, with the reflection method being the most widely used. This article will discuss in detail the reflection method in the principle of the ultrasonic flaw detector.

Reflection Method Ultrasonic Flaw Detector Theory

The basic principle of the reflection method is to utilize the reflective properties of ultrasound. When ultrasound travels from one medium to another, reflection occurs at their interface, and the greater the difference between the two media, the more pronounced the reflection. When using the reflection method for detecting defects within an object, ultrasound is first transmitted into the object under inspection, and the reflected ultrasound signals are then received. By comparing the transmitted ultrasound with the received ultrasound, the ultrasonic flaw detector theory can determine whether there are internal defects within the object, as well as the type and location of the defects.

In practical operation, the reflection method can determine the size and location of internal defects by detecting the time delay and reflection intensity of the ultrasound. For example, when ultrasound propagates through defect-free uniform material, its reflection signal will be relatively stable, while at defect locations, the reflection of the ultrasound signal will change significantly, thereby being detected by the flaw detector. This method is especially suitable for non-destructive testing of metal materials and has been widely used in quality control of welds, castings, and forgings.

Application of Image Processing in Ultrasonic Flaw Detector

During the reflection method flaw detection process, the acquired ultrasound signals are converted into intuitive images through image processing for observation and analysis. In the ultrasonic flaw detector theory, there are various image processing methods, with the most common being A-scan display. The A-scan display uses the propagation time or distance of ultrasound in the material as the horizontal axis and the reflection amplitude as the vertical axis. Based on the shape of the image, inspectors can quickly determine whether there are internal defects and their location and size.

In addition to the A-scan display, B-scan display, M-scan display, C-scan display, and F-scan display are also common image processing methods. The B-scan display generates images similar to anatomical cross-sections of an object's interior, suitable for detecting static objects, such as the commonly used ultrasound scanner in hospitals. The M-scan display is suitable for detecting dynamic objects, such as the heart and arterial vessels. Although the C-scan and F-scan displays were once widely used, they have gradually been phased out due to operational inconvenience and incomplete display results.

In practical applications, the choice of image processing depends on the specific testing requirements. By combining different image processing methods, the ultrasonic flaw detector theory can provide more comprehensive defect detection information, helping inspectors make accurate judgments.

Ultrasonic Flaw Detector detects internal defects in objects by utilizing the reflective properties of ultrasound, with the reflection method being the most widely used detection method. By analyzing the reflection signals, inspectors can determine the location, size, and type of defects. Image processing technology further enhances the intuitiveness and accuracy of ultrasonic flaw detection, making this technology widely used in industrial and medical fields.

Ultrasonic flaw detector theory not only excels in non-destructive testing of metal materials but also shows great potential and development prospects in other fields.