Analysis of the effective utilization of infrared thermography in additive manufacturing through advanced finite element modeling

Additive manufacturing is a powerful technique capable of producing fully dense metallic components. However, process instabilities can introduce defects that may compromise the structural integrity and performance of the fabricated parts. Among the most critical defects are lack of fusion and gas porosities, which significantly affect mechanical properties. Joule Heating Thermography (JHT) represents a promising non-destructive testing method to detect manufacturing defects in metal components. Nevertheless, its application to additive manufactured parts remains limited and requires proper calibration to ensure accurate and reliable measurements. To support calibration and interpretation of experimental data, numerical simulations are an effective tool. The objective of this thesis is to develop a numerical model capable of simulating the JHT process on components manufactured using additive manufacturing techniques for metals and to use the developed model to evaluate the influence of part geometry and defects characteristics on defect detectability. A finite element method (FEM) model was developed and implemented using ABAQUS/CAE. Simulations were conducted by solving a three-dimensional transient coupled thermal-electric problem. The developed model was adopted to conduct several numerical designs of experiments. These assessed the influence of the current applied to the samples to conduct JHT, the physical properties of the material (thermal and electrical conductivity of bulk and powder material) and the geometry of the defects, on the detectability of the defect. The developed model was also applied to replicate the defect detection on a PBF-EB component available in the literature. Numerical results were processed considering the temperature gradients generated by the presence of defects in the sample, considering the dimensions of the defects. The models were then validated by comparing numerical with experimental thermography performed on a specimen produced by powder bed fusion with electron beam in which defects were intentionally seeded.