2D temperature distribution reconstruction of steel bars under thermal transient from sequences of occluded infrared images

• Stitching multiple transient thermographic images for moving objects. • Space and time alignment methodology based on data-driven thermal transient model. • Application to moving high temperature steel bars. In-line thermography evaluates surface temperature distributions for quality control. This paper addresses the issue when the thermal imaging camera cannot fully capture a moving component undergoing successive stages of processing with transient thermal behavior. Reconstruction of the 2D temperature distribution requires stitching sequential partial images. When the object is moving and undergoing a thermal transient, simple stitching of sequential images leads to discontinuities and erroneous temperature distribution because the images are framed at different times. The correction of such artifacts is demonstrated using steel bars coming out of an induction furnace as an example. Two strategies are compared: temporal alignment and spatial alignment. Spatial alignment considers cooling relative to the distance from the furnace, requiring knowledge of the transient thermal pattern of the bar. The performance of the method is discussed in terms of effectiveness, uncertainty, and practical implementation.