Temperature field simulations during selective laser melting process based on fully threaded tree

Abstract

Selective laser melting (SLM) is the commonly term to describe the process in which a high energy laser beam scans the surface of a metal powder bed and the melted powder solidifies to form the bulk part [1] . SLM make it possible to create final function parts without post processing steps. Manufacturing businesses aiming to deliver their new products more quickly increasingly employ selective laser sintering/melting (SLS/SLM) for fabricating high quality, low cost, repeatable, and reliable alloy powdered parts for automotive, aerospace, and aircraft applications [2] . SLS can indirectly form integral control-shaped capsule for hot isostatic pressing (HIP) and mould core for casting, and SLM can directly and rapidly form HIP-shaped capsule [3] . SLM is complicated because of its high laser scan velocity and phase transformation in a sharply short time. Temperature field in this process is inhomogeneous [4][5][6] . Meanwhile, temperature evolution history would have significant Abstract: Selective laser melting (SLM) is a promising technique for additive manufacturing. During SLM of metallic powder, the temperature field and thermal history are important to understand physical phenomena involved. The purpose of this study is to simulate the temperature field during the SLM process of a hollow cylinder shape part based on a fully threaded tree (FTT) technique, and to analyze the temperature variation with time in different regions of the part. A revised model for temperature field simulation in the SLM process was employed, which includes the transition of powder-to-dense sub-model and a moving volumetric Gaussian distribution heat source sub-model. The FTT technique is then adopted as an adaptive mesh strategy in the simulation. The simulation result shows that during the SLM process of cylinder part, the temperature of inner powder bed is obviously higher than external one. The temperature at the internal of the molten pool is also higher than external, which may lead to differences in microstructures and other properties between the two regions.Key words: fully threaded tree; selective laser melting; temperature distribution; numerical simulation effects on final quality of parts. Large temperature gradients increase residual stresses and distortion and even lead to cracks in parts. Therefore, it is significant for SLM researchers to understand the mechanism of this process and effects of the parameters. Experiments regarding temperature fields, which greatly influence the formation of defects during the process, are lacking. It is a difficult work for most researchers to gain the detailed temperature field and its history during SLM process based on present experiment conditions. So, numerical simulation plays a significant role in the study of thermal behaviour during SLM process. The aim to perform temperature field simulation of SLM processes is to reduce the experimental cost, reveal the transient thermal history that cannot be obtained by limited experiment, and understand the evolution of microstructure...

A finite addition of matter elements method for modeling and solution of an SLM thermal problem by a multiscale method

“…At each iteration of the algorithm detailed above, one can prove (see 68 ), that each of the discrete mixed linear Arlequin system (19) has a unique solution. To solve this system, we use a classical extension of the Gauss elimination algorithm, ending with a Schur-Complement finite linear system whose unknown vector is made of the discrete Lagrange multiplier coordinates.…”

“…In the context of AMP, the pure thermal problem for the electron beam melting process of Ti‐6Al‐4V is h‐refined only in the direct vicinity of the electron beam zone in Reference 18. In Reference 19, the thermal field evolution during the SLMP process is simulated by using a fully threaded tree technique to refine the mesh in the moving laser impact zone. Let us finally mention recent developments in Reference 20 (and the references mentioned therein), where a multilevel h‐p ‐finite element method is combined with the finite cell method.…”