Heat Source Modeling and Residual Stress Analysis for Metal Directed Energy Deposition Additive Manufacturing

Abstract

The advancement in additive manufacturing encourages the development of simplified tools for deep and swift research of the technology. Several approaches were developed to reduce the complexity of multi-track modeling for additive manufacturing. In the present work, a simple heat source model called concentrated heat source was evaluated for single- and multi-track deposition for directed energy deposition. The concentrated heat source model was compared with the widely accepted Goldak heat source model. The concentrated heat source does not require melt pool dimension measurement for thermal model simulation. Thus, it reduces the considerable time for preprocessing. The shape of the melt pool and temperature contour around the heat source was analyzed for single-track deposition. A good agreement was noticed for the concentrated heat source model melt pool, with an experimentally determined melt pool, using an optical microscope. Two heat source models were applied to multi-track 3D solid structure thermo-mechanical simulation. The results of the two models, for thermal history and residual stress, were compared with experimentally determined data. A good agreement was found for both models. The concentrated heat source model reported less than the half the computational time required for the Goldak model. The validated model, for 3D solid structure thermo-mechanical simulation, was used to analyze thermal stress evolution during the deposition process. The material deposition on the base plate at room temperature results in lower peak temperatures in the layers near the base plate. Consequently, the higher thermal stress in the layers near the base plate was found, compared to the upper layers during the deposition process.

Elevated Temperature Baseplate Effect on Microstructure, Mechanical Properties, and Thermal Stress Evaluation by Numerical Simulation for Austenite Stainless Steel 316L Fabricated by Directed Energy Deposition

“…The material was deposited by using the InssTek MX-600 metallic deposition system (InssTek, Daejeon, Korea). The DED process parameters provided by the DED machine manufacturer were used for material deposition [20].…”

“…A finite element model was developed for both thermal and mechanical simulation using 3DExperience software (Dassault Systèmes, Vélizy-Villacoublay, France). The melt pool created from the laser was simulated using a concentric heat source model [20]. The moving heat source was set to 500 W power as per the experimental input data.…”

“…A progressive material deposition strategy that represented the DED process of new material addition with time was implemented [20]. As the upper-deposited layers were exposed to ambient conditions, this resulted in continuous evolution of the cooling surface with time.…”

“…Extensive previous reports mentioned above have contributed to our understanding about the baseplate preheating effect on the reduction of residual stress and distortion generated during AM. However, these works focused on either the reduction of the negative effects of concentrated heat during the deposition process by using numerical simulations in [19,20], or the relationships between the baseplate preheating effect and microstructure and mechanical properties, without providing thermal information. A collective and direct understanding of thermal history-induced microstructure and mechanical properties for AM materials is needed in order to have a clearer picture of the baseplate preheating effect for better utilization of its positive effects.…”

“…The present numerical simulation of deposition at elevated temperatures was compared with that at room temperature. The results for the thermo-mechanical simulation of baseplates at room temperature were derived from our previous work [20].…”