Experimental Study on the Static Strain Aging of Q345 Steel Using Complementary In-Situ Non-destructive Testing Techniques

The detection of the static strain aging extent of steel structures holds paramount significance in the safety assessment system. Tensile tests were performed on Q345 steel specimens subjected to static strain aging treatment, while simultaneously employing complementary in-situ detection techniques: acoustic emission, infrared thermography, and digital image correlation for real-time monitoring. The physical effect mechanism is initially confirmed through an analysis of the mechanical response of strain aging Q345 steel. The acoustic emission signals from the cluster 3 exhibiting high frequency and low amplitude are linked to the microplastic yield phenomenon. These signals, detected through acoustic emission technology, are considered representative of the dislocation activity in Q345 steel after strain aging. Illustrating via specimen S16-150, it is evident that as strain aging advances, there is a notable decrease of 63.02% in information entropy, 22.4% in partial power, and 55.04% in the wavelet coefficient of typical acoustic emission signals. Subsequently, digital image correlation was utilized to examine the local strain variation associated with microplastic deformation, and it was observed that Lüders bands did not form in specimens S12-150 and S16-150 due to strain aging. Finally, infrared technology was employed to monitor the instantaneous temperature of strain aging Q345 steel, facilitating the examination of its thermal energy conversion efficiency. Specimen S16-200 exhibited a fracture instantaneous temperature that was 21% higher compared to specimen S0-25. These findings establish a solid foundation for the integrity assessment of steel structures.