Modern advanced manufacturing technologies have the potential to revolutionize the way we fabricate components in the future. However, to be widely adopted by industry, adjustments to current industry methodologies and standards for part certification and qualification are needed to capture the increased complexity surrounding those manufacturing processes. Toward this goal, there is a growing research focus on developing new methodologies for certification and qualification that synthesize modeling and simulation, in-situ monitoring, and ex-situ characterization. In this context, thermal imaging has an important role to play as it can provide direct measurements of the manufactured components or of the machine itself. In this presentation, we will illustrate how thermal imaging is used to advance the field of advanced manufacturing by providing a series of examples on additive and hybrid manufacturing systems from the ORNL Manufacturing Demonstration Facility.

In the presented work the principle of super-resolution imaging using structured illumination is applied to thermography. Scattered light which can penetrate under the surface of a sample heats subsurface light absorbing structures. The diffused heat is measured on the sample surface e.g. with an infrared camera, which allows to image the subsurface structures. The deeper these structures are below the surface, the more blurred their images become. Blind structured illumination inside the sample is used to calculate a super-resolution image which less blurring. The structured illumination inside the sample can be generated by interference of scattered light producing laser speckles.

Trapped humidity is a deleterious condition in several industrial sectors. Beyond reducing performance in process industry, it can create or accelerate structural damage mechanisms like corrosion, where thermally insulated equipment are the main concerning structures. Underneath the insulation, the corrosion evolves invisible at uncontrolled rates until leakage or more catastrophic failure occurs. The aim of this work is then to establish a passive thermographic technique to be deployed in such environments that can reliably detect trapped humidity. The Multivariate Thermography, based on the Partial Least-Squares regression, can efficiently separate indications from different physical phenomena and drastically reduce the effect of surface finish on the detectability. Preliminary results are encouraging to potentially extend the applicability of thermography to considerably low levels of surface emissivity and reduce the incidence of false positives in thermographic inspection.

Pulse eddy current thermography (PECT) is used in detecting small flaws in metal surface. PECT is based on high frequency (HF) electromagnetic radiation generating eddy current and monitoring the heat produced using thermal imager. Lately we have seen lot of systems with good performance, but none is portable or commercially available. All are quite large only suitable for stationary use. We report a small system including innovative excitation coil, compact HF generator and uncooled thermal imager. Combined with equivalent wavefield based software enables to detect and determine the dimensions of the flaw with high sensitivity.

Infrared Thermography (IRT) is a Nondestructive Testing (NDT) method that can complement the concrete infrastructure condition assessment in a fast and contactless manner. When applied to large structures in outdoor areas, the heat source is usually the Sun, which is dynamic and varies through the days, months, and year. Solar irradiation is vulnerable to changes in environmental conditions, which affects the upcoming IRT measurements. Besides that, vertical elements have multiple locations and orientations, where the solar exposure varies according to the solar cycle. Consequently, column faces can experience reduced energy flow, where low or inexistent thermal contrast restrains the detection of existing subsurface damages. In this study, three signal processing techniques, named Principal Component Thermography (PCT), Pulsed Phase Thermography (PPT), and Partial Least Square Thermography (PLST), were applied to thermograms sequences acquired from a concrete element under varying solar exposure. One reinforced concrete column was constructed with ten simulated subsurface defects positioned in the Northeast, Southeast, Northwest, and Southwest faces. This column was inspected hourly through different days of summer and winter periods. It was demonstrated the difference between the signature contrast registered in thermograms acquired from faces exposed to small and large periods of solar irradiation. The preliminary results of using thermographic signal processing techniques verified the possibility of increasing the signal-to-noise ratio and thermal contrast in elements under unfavorable solar exposure. In addition, the research explored the use of different image sequence intervals on the performance of the signal processing techniques.