Identification method of infrared radiation precursor information of coal sample failure and instability under uniaxial compression

• Published in: Infrared physics & technology 2021-12, Vol.119, p.103957, Article 103957
• Main Authors: Tian, He, Li, Zhonghui, Shen, Xiaofan, Zang, Zesheng, Song, Jingjing, Zhang, Quancong
• Format: Article
• Language: English
• Subjects: Autocorrelation coefficient; Infrared radiation; Infrared thermal image; Number of IRT points; Variance
• ISSN: 1350-4495; 1879-0275
• DOI: 10.1016/j.infrared.2021.103957

•The IRT rise buffer can be as the precursor information to determine the failure.•The IRT count is large in the medium-temperature zone and small in the other zones.•The critical slowing down theory is used to improve the accuracy of predicting. This study is aimed at investigating the effective precursory information of coal sample instability and failure under uniaxial compression. To achieve this aim, first, the infrared radiation temperature (IRT) variations of coal sample under the same loading mode were analyzed. Next, the variations of IRT counts on the coal sample surface, numbers of IRT points in high-temperature and low-temperature zones and IRT differences in the two zones were analyzed based on the infrared thermal image. Furthermore, the variations of variance and autocorrelation coefficient of IRT were explored with reference to the critical slowing down theory. The following results were obtained. The changes in IRT exhibit different characteristics in different stages of loading. Before the main rupture occurs, both the maximum infrared radiation temperature (MIRT) and the average infrared radiation temperature (AIRT) present a cooling precursor and an IRT rise buffer section. When the main rupture occurs, the MIRT surges, while the AIRT plunges. The high-temperature zone in the infrared thermal image keeps expanding with the increase of stress, and the low-temperature zone also expands considerably before the main rupture. The number of IRT points in the high-temperature zone decreases first and then increases with the increase of stress, while the number of IRT points in the low-temperature zone increases continuously with it. The IRT differences in the high-temperature and low-temperature zones vary in a basically consistent way with the number of IRT points in the two zones, respectively. The MIRT curve, and the curve of number of IRT points in the high-temperature zone and the variance curve of MIRT can all be taken as the precursor signal for identifying coal sample instability and failure. Among the three, the variance curve of MIRT boasts the most superior effect.