1、 Infrared nondestructive testing

Infrared nondestructive testing is to identify the quality of metal or non-metallic materials and detect internal defects by measuring heat flow or heat. For some local defects that cannot be detected by X-ray and ultrasonic, infrared nondestructive testing can achieve better results.

Infrared nondestructive testing mainly has the following typical applications:

(1) Nondestructive testing of welding defects.The welded junction surface is uneven, so it is difficult to find defects by X-ray, ultrasonic, eddy current and other methods. If an AC voltage is applied to both ends of the welding area, AC current will flow through the crater. Due to the skin effect of current, the current density near the surface will be greater than that of the lower layer. Due to the action of current, the crater will generate a certain amount of heat. The amount of heat is proportional to the resistivity of the material and the square of the current density. In the welding area without defects, the current distribution is uniform, the heat generated everywhere is roughly equal, and the surface temperature distribution of the welding area is uniform. The welding area with defects has high resistance, which increases the loss and temperature in this area. Thermoelectricity can be clearly measured by using infrared temperature measuring equipment, so it can be concluded that there are welding defects under the hot spot.

(2) Internal defect detection of castings.The internal structure of some precision castings is very complex, and the traditional nondestructive detection method can not accurately find the internal defects. When infrared nondestructive detection is used, only liquid Freon cooling is needed inside the casting to achieve the best cooling effect, and then the infrared thermal imager is used to quickly scan the whole surface of the casting. If there is residual core or uneven wall thickness in the channel, it can be clearly seen in the heat map. If the cooling channel is unblocked and the cooling effect is good, a series of uniform white stripes are displayed on the heat map; If the passage is blocked and the cooling liquid is blocked, black stripes are displayed at the blockage

(3) Fatigue crack detection.A point radiation source is used to inject energy into a small area of the skin surface. Then, the surface temperature is measured with infrared radiation thermometer. If there are fatigue cracks on or near the skin surface, the heat conduction will be affected, and the heat near the crack will not be transmitted quickly, causing the surface temperature near the crack to rise quickly. When the radiation source is on both sides of a crack, the temperature on both sides is very high because the crack does not allow heat flow. When the heat source moves to the crack, the surface temperature drops to the normal temperature. In the actual measurement, due to the limitation of the size of the radiation source, the influence of the position of the radiation source and infrared detector, and the influence of the high-speed scanning speed, there will be some errors.

2、Application of infrared detection in PCB Fault Diagnosis

The existing conventional circuit fault detectors need to measure the voltage, current, impedance of key points and lines in the circuit and the necessary parameters of components. According to the relevant results obtained from the measurement, combined with the fault phenomenon and the in-depth understanding of the schematic diagram, they can diagnose the fault position of the circuit board or the fault components. It is difficult to meet the requirements of modern national defense through this conventional circuit board fault detection method, because this method has several defects: (1) it must have detailed maintenance information such as circuit schematic diagram, board diagram, component layout diagram, etc. (2) Its measurement method is contact measurement, which will inevitably affect the distribution parameters of the circuit, and it is impossible to be used for real-time fault detection of high-frequency circuits. (3) It is slow, time-consuming and laborious, and it is difficult to meet the high requirements for time and speed in the war environment. (4) It is difficult to diagnose potential faults, so it is difficult to avoid sudden failures of equipment at critical moments.

Using the infrared detection technology, the working state of hundreds of devices in a wide range can be detected quickly without touching at the same time without the need for staff to conduct in-depth analysis of the circuit, and the fault circuit or component in the circuit can be identified within dozens of seconds or even a few seconds after power on, without affecting the frequency characteristics of the circuit during detection; Moreover, it can quantitatively subdivide the state of components in the circuit from intact to fault into several levels, which enables the maintenance personnel to discover the hidden dangers of circuit faults in time and avoid the sudden occurrence of faults at critical moments.

3、Fault detection principle and equipment

When the circuit board is working, the components on it will emit heat, and the thermal image of the circuit board can be taken by the infrared instrument. During fault detection, firstly, it is necessary to take the thermal image of the normal circuit board when it is working, and save it to the database as a standard board; Secondly, take the thermal image of the faulty circuit board when it is working as the board to be tested; Thirdly, through the method of image processing, the plates to be tested are preprocessed, registered, compared and information extracted; Finally, according to the preset threshold, the number and location of faults are obtained.

Due to the late start of our country, there are still relatively few infrared fault detection equipment. At present, the existing equipment includes printed circuit board infrared fault diagnosis instrument, which is the molding equipment engaged in the research of infrared detection earlier in China; TIP-I circuit fault detector has a high fault diagnosis rate; The portable infrared circuit fault detection system makes the infrared detector more miniaturized.

4、 Summary

The application of infrared detection technology is very extensive and of great significance, which leads to more and more branch studies. Infrared thermal imaging is a key technology in infrared inspection. Some countries with developed technology are competing to study thermal imaging technology and develop it with huge human and material resources, which is developing very rapidly. Improving the accuracy of infrared image processing and developing intelligent fault detection equipment are key research directions, and more in-depth research should be done in these areas in the future.

Applicable Machine

KB23E31 online infrared thermal imaging thermometer adopts 17 μm uncooled infrared focal plane detector, high-performance infrared lens and signal processing circuit, and embedded image processing algorithm, with small size, low power consumption, fast start-up, excellent imaging quality, accurate temperature measurement and other characteristics.

The device selection of KB23E31 on-line infrared thermal imaging thermometer fully considers the requirements of high and low temperature working performance to ensure that the whole machine has excellent environmental adaptability

Functional Characteristics

1. Using customized macro lens, you can observe subtle targets;
2. With high frame rate design, fast-moving targets can be observed;
3. Adopt self-developed temperature measurement correction algorithm to realize accurate temperature measurement;
4. The full stream lossless 16bit temperature data is output, and the client software and SDK development kit are provided to facilitate the secondary development and system integration of customers, and fully carry out personalized temperature analysis of the tested target.

Application Field

Scientific Research Institutions, Optical Fiber Testing, Nondestructive Testing, Customized Development