Inverse Thermal Analysis of Melting Pool in Selective Laser Melting Process

2015 ◽  
Vol 651-653 ◽  
pp. 1519-1524 ◽  
Author(s):  
Laurent van Belle ◽  
Alban Agazzi
Keyword(s):  
Heat Source ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Selective Laser Sintering ◽  
Solid Material ◽  
Melting Process ◽  
Layer By Layer ◽  
Laser Melting ◽  
Mechanical Modelling ◽  
Melting Pool

The Selective Laser Melting (SLM) process of metallic powder is an additive technology. It allows the production of complex-shaped parts which are difficult to obtain by conventional methods. The principle is similar to Selective Laser Sintering (SLS) process: it consists, from an initial CAD model, to create the desired part layer by layer. The laser scans a powder bed of 40 μm thick. The irradiated powder is instantly melted and becomes a solid material when the laser moves away. A new layer of powder is left and the laser starts a new cycle of scanning. The sudden and intense phase changing involves high thermal gradients which induce contraction and expansion cycles in the part. These cycles results in irreversible plastic strains. The presence of residual stresses in the manufactured part can damage the mechanical properties, such as the fatigue life. This study focuses on the thermal and mechanical modelling of the SLM process. One of the key points of the mechanical modelling is the determination of the heat source generated by the laser in order to predict residual stresses. This work is divided in three parts. In a first part, an experimental protocol is established in order to measure the temperature variation during the process. In the second part, a thermal model of the process is proposed. Finally, an inverse method to determine the power and the shape of the heat source is developed. Experimental and computational results are fitted. The influence of several geometries of the heat source is investigated.

Three-Dimensional Temperature Gradient Mechanism in Selective Laser Melting of Ti-6Al-4V

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
C. H. Fu ◽  
Y. B. Guo
Keyword(s):  
Temperature Gradient ◽  
Selective Laser Melting ◽  
Molten Pool ◽  
Three Dimensional ◽  
Melting Process ◽  
Layer By Layer ◽  
Laser Melting ◽  
Transient Nature ◽  
Melting Pool ◽  
Three Dimensional Finite Element

Selective laser melting (SLM) is widely used in making three-dimensional functional parts layer by layer. Temperature magnitude and history during SLM directly determine the molten pool dimensions and surface integrity. However, due to the transient nature and small size of the molten pool, the temperature gradient and the molten pool size are challenging to measure and control. A three-dimensional finite element (FE) simulation model has been developed to simulate multilayer deposition of Ti-6Al-4 V in SLM. A physics-based layer buildup approach coupled with a surface moving heat flux was incorporated into the modeling process. The melting pool shape and dimensions were predicted and experimentally validated. Temperature gradient and thermal history in the multilayer buildup process was also obtained. Furthermore, the influences of process parameters and materials on the melting process were evaluated.

scholarly journals Computational investigation of thermal behavior and molten metal flow with moving laser heat source for selective laser melting process

2021 ◽  
Vol 24 ◽  
pp. 100860
Author(s):  
Patiparn Ninpetch ◽  
Pruet Kowitwarangkul ◽  
Sitthipong Mahathanabodee ◽  
Prasert Chalermkarnnon ◽  
Phadungsak Rattanadecho
Keyword(s):  
Heat Source ◽  
Thermal Behavior ◽  
Selective Laser Melting ◽  
Molten Metal ◽  
Metal Flow ◽  
Melting Process ◽  
Computational Investigation ◽  
Laser Melting ◽  
Laser Heat Source ◽  
Molten Metal Flow

Finite Element Thermal Analysis of Melt Pool in Selective Laser Melting Process

2018 ◽  
Author(s):  
Zhibo Luo ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Heat Source ◽  
Selective Laser Melting ◽  
Computational Cost ◽  
Melting Process ◽  
Point Heat Source ◽  
Laser Melting ◽  
Line Heat Source ◽  
Powder Bed ◽  
Melt Pool ◽  
Gaussian Point

Selective laser melting is one of the powder bed fusion processes which fabricates a part through layer-wised method. Due to the ability to build a customized and complex part, selective laser melting process has been broadly studied in academic and applied in industry. However, rapidly changed thermal cycles and extremely high-temperature gradients among the melt pool induce a periodically changed thermal stress in solidified layers and finally result in a distorted part. Therefore, the temperature distribution in the melt pool and the size and shape of the melt pool directly determine the mechanical and geometrical property of final part. As experimental trial-and-error method takes a huge amount of cost, different numerical methods have been adopted to estimate the transient temperature and thermal stress distribution in the melt pool and powder bed. The most existing research utilizes the moving Gaussian point heat source to model the profile of the melt pool, which consumes a significant amount of computational cost and cannot be used to implement the part-level simulation. This research proposes a new line heat source to replace the moving point heat source. Some efforts are applied to reduce the computational cost. Specifically, a relatively large step size is used for the line heat source to reduce the number of time steps. In addition, a mesh refinement scheme is adopted to reduce the number of cells in each time step by refining the mesh close to the heat source and coarsening the mesh far away from it. On the other hand, efforts are implemented to increase the accuracy of the simulation result. Temperature-dependent material properties are considered in this FE framework. In addition, material transition among powder, liquid, and solid are incorporated in the developed FE framework. In this study, temperature simulation of one scanning track based on self-developed FE code is applied for Stainless Steel 316L. The simulation results show that the temperature distribution and history of melt pool within line heat source are comparable to that of the moving Gaussian point heat source. While the simulation time is reduced by more than two times depending on the length of line heat input. Therefore, this FE model can be used to numerically investigate the process parameters and help to control the quality of the final part.

scholarly journals Investigation of Residual Stresses Induced during the Selective Laser Melting Process

2013 ◽  
Vol 554-557 ◽  
pp. 1828-1834 ◽  
Author(s):  
Laurent van Belle ◽  
Guillaume Vansteenkiste ◽  
Jean Claude Boyer
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Complex Geometry ◽  
Melting Process ◽  
Hole Drilling ◽  
Internal Stresses ◽  
Laser Melting ◽  
Selective Laser Melting Process ◽  
Engineering Materials

The selective laser melting process (SLM), belonging to the family of additive manufacturing processes, can create complex geometry parts from a CAD file. Previously, only prototypes were created by SLM, but now this process is used to manufacture quickly and directly functional parts. For example, in the PEP (Pôle Européen de la Plasturgie), this process is used to fabricate tooling parts or injection molds with cooling channels that can’t be obtained by conventional routes. During the process, the laser beam generates violent heating and cooling cycles in the material inducing important thermal gradients in the consolidated part. The cyclic thermal expansions and contractions exceeding the maximum elastic strain of the material induce heterogeneous plastic strains and generate internal stresses the level of which can reaches the yield stress of the material and cracks may appear during the process. This paper deals with the measurement and analysis of residual stresses during the selective laser melting of a simple part in maraging steel. The objective of this study is the analysis of experimental results to validate the numerical model previously presented in [1]. Some authors have investigated the residual stresses produced in SLM parts using different experimental measurement methods such as the incremental hole drilling method in [2], the layer removal method see in [3] and [4] or the non-destructive method, by neutron diffraction in [5]. A new method is proposed to evaluate the residual stresses induced during the SLM process, a rosette is fixed on the bottom face of the support. The residual stresses in the created part are calculated from strain and temperature variations when the fused layer is consolidating during the cooling between two layers. Process parameters like the powder thickness or the time cooling between successive layers are studied in this paper. [1] L. Van Belle, G. Vansteenkiste, J.C. Boyer, Comparisons of numerical modeling of the selective laser melting, Key Engineering Materials Vols. 504-506 (2012) pp 1067-1072 [2] C. Casavola, S.L. Campanelli, C. Pappalettere, Experimental analysis of residual stresses in the selective laser melting process, Proceedings of the XIth International Congress and Exposition, June 2-5, 2008 Orlando, Florida USA [3] M. Shiomi, K. Osakada, K. Nakamura, T. Yamashita, F. Abe, Residual stress within metallic model made by selective laser melting process, CIRP Annals - Manufacturing Technology, Vol. 53, No. 1. (2004), pp. 195-198 [4] T. Furumoto, T. Ueda, M.S. Abdul Aziz, A. Hosokawa and R. Tanaka, Study on reduction of residual stress induced during rapid tooling process, influence of heating conditions on residual stress, Key Engineering Materials Vols. 447-448 (2010) pp 785-789 [5] M. Zaeh, G. Branner, Investigation on residual stresses and deformation in selective laser melting, Production Engineering, Volume 4, Number 1 (2010)

An Object-Oriented Class Library for Scanning Path Generation in SLS/SLM Process

2010 ◽  
Vol 44-47 ◽  
pp. 3309-3313
Author(s):  
Jie Liu ◽  
Yong Qiang Yang ◽  
Jian Bin Lu ◽  
Xu Bin Su
Keyword(s):  
Parallel Computing ◽  
Selective Laser Melting ◽  
Generation Time ◽  
Selective Laser Sintering ◽  
Object Oriented ◽  
Melting Process ◽  
Path Generation ◽  
Laser Melting ◽  
Class Library ◽  
Scanning Path

This paper presents an Object-Oriented class library for scanning path generation in SLS/SLM (Selective Laser Sintering/Selective Laser Melting) process. The classes in the library meet the minimal requirement for the scanning path generation. Specially, in order to take advantage of the Multiprocessor technology and save the generation time, parallel computing is considered in the class library. At last, an application was developed using the class library and an experiment is provided to verify the feasibility of the parallel computing algorithm in the library.

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