According to statistics, metal fatigue is easy to cause the failure of mechanical parts, and about 70% of the failure of mechanical parts is caused by metal fatigue. Failure of parts is easy to cause safety accidents, economic losses and even casualties. Therefore, it is necessary to study and test the fatigue strength of metal materials through experiments and test the anti-fatigue performance. There are several common fatigue test methods for metal, such as single point fatigue test, lifting fatigue test, high-frequency vibration fatigue test, ultrasonic fatigue test, infrared thermal imaging fatigue test. Next we will focus on infrared thermal imaging fatigue test methods.

Thermal stain of metal fatigue damage

Due to the effect of infrared cold emission (IRCE) and infrared thermal emission (IRHE), there are obvious infrared emission energy changes in the stress concentration area of metal pressure vessel during the fatigue compression process of working stress. After a certain period, the fatigue damage zone will produce irreversible temperature increase.

Fatigue test method for infrared thermal camera

Infrared thermal imaging technology is a wavelength conversion technology, which converts the thermal radiation of the target into visible light, and uses the difference of the thermal radiation of each part of the target to obtain the image. Computer image processing technology and infrared temperature measurement technology are used to realize the display, analysis and accurate measurement of the temperature field distribution on the surface of the object. In order to increase the specific emissivity of the metal surface, a very thin layer of infrared transmission coating is usually applied to the sample surface during the test. There are multiple results show that the fatigue and cracks of metal pressure vessel pressure vessel fatigue damage zone under the condition of stress at work, there is always hot patches exists, this hot spot photovoltaic trace as the fatigue crack extension, although its morphology and track changes, but by its exact location signs of fatigue damage area doesn't change, especially to the fatigue damage of the late heat patches pattern, already can clearly see the size of the crack. The fracture analysis of the fatigue leakage area proves that the thermal speckle detection of the fatigue damage area in the early stage by thermoelastic stress infrared image is correct. The infrared thermal camera is used to detect the thermal speckles calculated by fatigue, so as to help the experimenter to conduct effective data analysis and judgment, thus the research results are obtained. It can be seen that the effect of infrared thermal camera used to test the fatigue strength of metal is still considerable.