The most common testing method for industrial flaw detectors - X-ray

There are many detection methods for X-ray industrial flaw detectors, and the most common ones are five and five of the most conventional detection methods. Firstly, the editor will introduce the specific situation of conventional testing methods and characteristics, and then select the appropriate testing method for oneself.

1. X-ray inspection method

X-ray detectors utilize ray penetration and linear defect detection methods. Although these rays may not be as direct as those visible to the naked eye, they can be used to make photographic film or to pick up a special radio receiver. Commonly used for detecting radioactive isotopes such as X-rays and gamma rays, respectively referred to as X-ray testing and radiographic testing. When light passes through (light), the density and intensity of the material decrease, and the larger the ray, the stronger it can penetrate the material. At this point, if film is used to receive and the passive photosensitive amount is small; If the instrument is used for reception and the signal is weak. Therefore, if the internal defects such as pores, slag inclusions, or rays passing through the wrong path are less dense than those passing through the material without defects, the strength of the parts will be lower, that is, the strength of the parts passing through will be greater. If negative films are used for reception, The large number of photosensitive elements can reflect the plane projection of defect rays in the vertical direction from this movie. If other receivers are used, tools can be used to reflect the ray projection of defects in the vertical direction plane, and the ray passes through the volume. Therefore, under normal circumstances, cracks are not easily detected by X-ray detectors, or conversely, X-ray detectors are not sensitive to cracks. Therefore, X-ray detectors with porosity are most sensitive to volumetric defects such as slag inclusion and incomplete penetration. Radiographic testing is suitable for volumetric defect inspection and for areas that are not suitable for defect detection.

2. Ultrasonic testing methods

The frequency range of sound waves that can be directly received by the human ear is usually 20 Hz to 20KH7. This is the frequency of sound (sound), which is called the sound frequency below 20 Hz, and it is called ultrasonic high dry 20KHZ. A few megahertz commonly used in the ultrasonic testing industry. Ultrasonic waves have a high propagation frequency, strong linearity, and are solid, making them easy to propagate. They also reflect easily at the interface of two different media, so you can use them for testing. Usually, ultrasonic probes are used to make contact with the ground, which can effectively detect the workpiece and obtain the reflected ultrasonic waves at the (defect) interface. At the same time, they are converted into electrical signals and then transferred to the instrument for processing. You will know the location of the defect based on the speed of the ultrasonic wave propagation medium (usually referred to as the speed of sound) and the propagation time. When there are defects, the larger the reflective surface, the greater the reflective energy. The reason for the larger the reflective energy can be found based on the size (equivalent) of each defect. The commonly used detection waveforms include longitudinal and transverse waves, surface waves, etc., which are suitable for detecting surface defects before dry detection of internal defects, but with high requirements for surface conditions.

3. Magnetic Particle Testing Method

Magnetic particle testing is a magnetic testing method based on the principle of dry magnetic flux leakage. When the magnetic field line passes through the ferromagnetic material and its products, it will generate a leakage magnetic field, which is a discrete form of the magnetic pole. At this time, with thousands of magnetic particles or inverted magnetic levitation, Poles will absorb magnetic particles and can directly observe obvious magnetic marks with the naked eye. Therefore, magnetic marks can be used to display defects in ferromagnetic materials and their products. Magnetic particle testing methods can detect surfaces, but small defects cannot be directly observed with the naked eye or with a magnifying glass. It can also detect surface defects that are not exposed, but are buried several meters away from the nearby surface. In this way, Although it can also detect defects such as incomplete penetration of the number and type of inclusions with varying degrees of porosity, defects with more sensitive areas are more suitable for inspecting quenching, forging, casting, welding, electroplating, grinding, and those caused by fatigue cracks.

There are many methods for magnetic testing that display useful magnetic particles for defects, and there are no magnetic particles available. Magnetic particle inspection, also known as magnetic particle display, is one of the most commonly used methods due to its direct display, simple operation, and people's willingness to use it. Do not use magnetic particles, traditionally known as magnetic flux leakage testing, which usually uses induction coil susceptibility Hall elements to reflect defects. For example, it is healthier than magnetic particle inspection, but not as intuitive as the former. Due to the current use of magnetic particle testing to display defects, it is sometimes referred to as direct magnetic testing, and magnetic particle testing equipment is called magnetic testing equipment.

4. Eddy current testing method

Eddy current detection is the alternating magnetic field generated by the action of alternating current to detect conductive materials that induce pot flow. If there are defective materials, it will interfere with eddy current, which is the formation of interference signals. Detect interference signals with eddy current flaw detectors and then determine the status of defects. It is said that there are many factors that affect eddy current signals, and there are many factors related to these signals and materials. How to use signals from many different signals is currently a problem of eddy current. Researchers have made some progress, and over the years, under certain conditions, some problems can be solved, but it is still far from meeting the on-site requirements and technological development.

The characteristics of eddy current testing are that the material can work, but it may not necessarily be ferromagnetic, but it reduces the impact on ferromagnetic materials. Secondly, it is discussed that the smooth surface of the working surface has a significant impact on the full flow inspection interface. Therefore, eddy current testing is often used to inspect copper and other non ferromagnetic components with dry shape rules, smooth surface.

5. Penetrant testing methods

Penetration testing is a method of verifying the use of hand tubes. The surface of the parts is smooth, clean, and the color (red) is often used with belts or fluorescent, highly permeable liquids, and the above ground part of the coating surface. If the surface microcracks cannot be directly observed with the naked eye, due to the strong permeability of the liquid, it will penetrate along the cracks to the root. Then wash the liquid that permeates the surface, and apply a large amount of liquid (usually white). After a moment, the dry cracks are very small. The effect of hand fine phenomenon is significant, and the original penetration crack penetration will rise to the surface diffusion, showing a thick red line on the white substrate, indicating the shape of the crack on the surface. Therefore, it is commonly referred to as penetration inspection. If liquid fluorescent penetrant is used, the liquid that rises to the surface through capillary phenomenon will emit fluorescence under ultraviolet radiation, which can display the shape of the surface pattern on the chardonnay. The reason is that it is commonly referred to as penetration testing directly in this repeated fluorescence detection. This detection method can also be used to inspect dry metal and non-metal surfaces, and has a strong odor. Testing the use of liquid agents often has certain toxicity.