A Method for Identifying Precursors Information on Infrared Radiation of Instability and Failure in Wood

Anomalies in infrared radiation temperature (IRT) are usually accompanied via the sprouting and expansion of cracks. Precursor information of crack sprouting and extension is essential for predicting the condition as a material of structural fields. In order to investigate the precursor information of instability and failure of wood, the infrared radiation characteristics of wood during failure were analyzed by a three-point bending test. Based on the IRT probability distribution conforming to the Gaussian distribution, an indicator is defined in this paper: the peak probability density (PPD) of IRT. The changes in PPD were combined with the four stages of typical damage to determine the precursor information, and identified a precursor point on the PPD-time curve. The relations between IRT indicators and wood fracturing were also investigated to explain the anomalies in IRT indicators, the precursor point characterize the transition zone from the elastic to the plastic phase of deformation when the wood is under pressure. Besides, the samples before and after the precursor point were also compared by macroscopic (digital image correlation, DIC) and microscopic (scanning electron microscope, SEM), the results proved the validity of the precursor information. Comparison with other IRT indicators, the IRT indicator proposed in this paper has a higher sensitivity to IRT abnormalities in the failure process of wood structures.