When the ultrasonic wave is transmitted in the tested material, the acoustic properties of the material and the change of the internal structure have a certain influence on the propagation of the ultrasonic wave, which is known as ultrasonic detection through the detection of the influence degree and the condition of the ultrasonic.
Ultrasonic testing methods usually have a penetrating method, digital ultrasonic flaw detectors, such as pulse reflection method and tandem method, are now usually used to transmit ultrasound to objects (such as industrial materials, human body), then use their reflection, Doppler effect, transmission, etc。 to obtain the information inside the object being measured and to process the image。
Ultrasonic flaw detectors The Doppler effect method is used to obtain the characteristics of the motion direction and velocity of the object when the Doppler frequency shift effect occurs when the object is in motion. The transmission principle is that the internal characteristics of the object are obtained by analyzing the changes of ultrasonic after penetrating the measured object, and its application is still in the development stage. Ultrasonic flaw detectors Here is the most widely used method to obtain the internal characteristic information of the object by the reflection method.
The reflection method is based on the principle that the ultrasonic can be reflected when the interface of different acoustic impedance is changed. As we know, sound waves are reflected at the interface between the two when they propagate from one medium to another, and the larger the difference between the media, the greater the reflection, So we can be able to launch an object with strong penetrating, linear transmission of ultrasound, ultrasonic flaw detector and then reflected back of the ultrasonic wave to receive and based on the reflection of the ultrasonic wave back to the extent of the scale, and so on, can determine the size of the various media contained in the organization, Distribution and the contrast between various media and other information (in which the reflected back of the ultrasonic wave can reflect the reflective interface from the surface of the detection, amplitude can reflect the size of the medium, contrast and other characteristics), ultrasonic flaw detectors to determine whether the object is abnormal. In this process involves many aspects of the content, including ultrasonic generation, reception, signal conversion and processing.
The method of producing ultrasonic wave is to generate the excitation signal through the circuit to pass to the crystal (such as quartz, lithium sulfate, etc.) which has the piezoelectric effect, so that it vibrates to produce ultrasonic wave; while receiving the echo back The piezoelectric crystals are also subjected to the pressure of the reflected sound waves to generate electrical signals and transmit them to the signal processing circuitry for a series of processing, and the ultrasonic flaw detectors finally form images for people to observe and judge.
According to the image processing method (that is, the resulting signal into what form of the image) can be divided into a-type display, M-type display, B-type display, C-type display, F-type display. The type a display is to receive the ultrasonic signal processing into a waveform image, according to the shape of the waveform can be seen whether there are anomalies and defects in there, how big, etc., ultrasonic flaw detectors are mainly used in industrial testing; The M-type display is a one-dimensional "spatial multi-point movement sequence diagram", which is suitable for observing the internal moving object, the ultrasonic flaw detector such as the moving organ, the arterial blood vessel, etc. The B-type display is a two-dimensional composite of a group of detection information that is treated by a number of luminance reflecting the "anatomical image" of the internal fault section of the object being measured (the B-ultrasound used in the hospital is made with this principle), the ultrasonic flaw detector is suitable for observing the internal static object, while the C-type display and the F-type display are now used relatively little.
Ultrasonic flaw detectors can not only be very accurate detection, but also relative to other detection methods more convenient, faster, and will not be harmful to the detection object and operator, so people have been more and more popular, has a very broad prospects for development.
The Ultrasonic flaw detectors will usually use 3.7V/7.4V/12V lithium ion battery,which will help people to finish long time outdoor test work.
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