Three-dimensional annular heat source for the thermal simulation of coaxial laser metal deposition with wire

Abstract

Coaxial laser metal deposition with wire (LMD-w) is an innovative additive manufacturing technology in which a wire is coaxially fed through the center of a hollow laser beam into a laser-induced melt pool. This special configuration results in a direction-independent process, which facilitates the manufacturing of thin-walled metal components at high deposition rates. However, laborious experimental test series must be conducted to adjust the process parameters so that the substrate and the part do not overheat. Therefore, models are needed to predict the resulting temperature field and melt pool dimensions efficiently. This paper proposes a finite element simulation model using an innovative heat source, which considers the unique intensity distribution of the annular laser spot. The heat source parameters were calibrated experimentally based on fusion lines obtained from metallographic cross sections of aluminum alloy samples (AA5078 wire and AA6082 substrate). Subsequently, the temperature distribution in the substrate plate was measured by means of thermocouples to validate the developed model. It was shown that the proposed heat source replicates the heat input accurately. With the presented model, essential features for process development, such as the temperature field and the melt pool dimensions, can be reliably predicted. The model contributes to a better understanding of the LMD-w process and facilitates an efficient process development in future research work as well as for industrial applications. Key words: thermal simulation, annular laser spot, heat source, laser metal deposition, coaxial wire feeding, directed energy deposition

Experimental and simulative investigation of welding sequences on thermally induced distortions in wire arc additive manufacturing

“…In literature, a number of dedicated heat source models have been proposed for the simulation of welding processes. Heat source shapes range from planar Gaussian power distributions (Pavelec et al , 1969) over volumetric double-ellipsoid power distributions (Goldak et al , 1984) to specifically designed power distribution geometries for DED processes (Montevecchi et al , 2016, Zapata, 2023). The aforementioned heat source models were designed to capture the melt pool shape and, thus, require a high temporal and a high spatial resolution in the simulation, entailing a high number of time steps and a fine mesh.…”

A Review on Wire-Laser Directed Energy Deposition: Parameter Control, Process Stability, and Future Research Paths

“…Unlike lateral deposition heads, the use of concentric or coaxial heads (Figure 9a) eliminates the need for table or head rotation, allowing material deposition in virtually any direction [73,89,120]. Specialized optics have been developed to shape the laser beam in a way that enables wire feeding through the center of the beam to ensure a distribution of laser radiation over the wire [121][122][123]. The coaxial approach consists of feeding the wire in the center of multiple single lasers (donut shape) or inside an annular laser beam, providing diverse options for the process [54,79,124,125].…”

“…Thermocouples, pyrometers, and infrared (IR) cameras are used to monitor the melt pool's temperature during the processes. Thermocouples are often in direct contact with the build plate, enabling temperature measurements [122,214]. Alternatively, both pyrometers and IR cameras can be integrated into the processing head, allowing for unrestricted movement and directional independent data acquisition [85].…”

Simulation of Wire Arc Additive Manufacturing in the Reinforcement of a Half-Cylinder Shell Geometry

“…The variable represents the time- and space-dependent internal cuboid heat source given by: where denotes the power output of the welding power source at a specific time and location, represents the heat source efficiency, and , , and denote the height, width, and length of the heat source, respectively. While more refined heat source shapes have been proposed in the literature, such as the Goldak double-ellipsoid heat source [ 18 ] and the annular heat source [ 19 ], these models were designed to capture the melt pool shape and require a high temporal and spatial resolution in the simulations. For thermo-mechanical simulations focusing on distortions at a part scale, a computationally less expensive cuboid heat source is sufficient [ 15 ].…”