Numerical modeling of the coupled heat transfer and ultrasonic time of flight during monitoring of a laser powder bed fusion process

This paper proposes a numerical model coupling heat transfer and ultrasonic time of flight (TOF) phenomena within the Laser Powder Bed Fusion (LPBF) process. A three-dimensional layer scale thermal model is developed to simulate the temperature field evolution during the LPBF process, considering the laser energy input, heat conduction, and convection heat transfer. A TOF model is developed based on the measured velocity of the ultrasonic wave in the materials involved, taking into account the temperature-dependent variations of the wave velocity in the plate and the part by coupling it to the thermal model output. The models are calibrated using experimental data from an aluminum part manufactured in a Farsoon FS271M LPBF machine. The experimental data consist of IR camera images of the part surface temperature, thermocouple measurements on the back plate, and TOF measurements throughout the process. The numerical simulations are compared with the experimental data to assess the model's accuracy and identify key parameters affecting the heat transfer and ultrasonic wave propagation. This work provides a framework for understanding the relationships between the temperature field, the TOF signal, and the LPBF process parameters, paving the way for improved process control and monitoring strategies.