Model Of Selective Laser Melting Research Articles

Simulation of the selective laser sintering/melting process of bioactive glass 45S5

Additive manufacturing processes, including selective laser sintering (SLS) and selective laser melting (SLM), are rapidly developing industrial fields that require scientific support. Although SLS and SLM are very similar, the level of modeling and simulation of SLM is much higher than that of SLS. This results in the number of publications before 2024 according to Web of Science with SLM simulation approximately five times more than with SLS. To test the possibility of adequate SLS simulations, a platform based on the lattice Boltzmann method (LBM), previously developed and applied to model the SLM process, was used. In addition, the possibility of modeling similar processes (SLM, SLS, and SLS/SLM) using the same modeling tool on the same modeling platform is important. The objective of this paper is to present a model of the SLS process and confirmation of the possibility of using LBM for simulation of the SLS process. A simulation of SLS and SLM with the use of LBM, and qualitative comparison of the results of these simulation for bioactive glass 45S5 is the basis of the methodology used for the research. The simulation presented in this study confirmed the possibility of simulating SLM, SLS processes using common principles, approaches, and models. The results of SLS process simulations can be treated as qualitative and require further verification, whereas SLM simulations have been previously verified. The application of the lattice Boltzmann method, which is a computational fluid dynamics (CFD) method, opens the possibility of using almost every CFD method for the simulation of several kinds of SLS, and can accelerate research in this field.

A simulation model of selective laser melting (SLM) of glass silica monolayer

A simulation model of selective laser melting (SLM) of glass silica monolayer

Simulation Study on the Energy Utilization Efficiency of a Turbine Impeller Based on a Selective Laser Melting Process

In this paper, a simulation model for Selective Laser Melting (SLM) technology is established to simulate the additive manufacturing process of a turbine impeller for an aerospace engine. By utilizing the simulation model, variations in laser power and scanning speed are employed to obtain simulated results of thermal deformation for the turbine impeller under different laser power and scanning speed conditions. The results indicate that the thermal deformation of the component increases with the augmentation of laser power, decreases with the escalation of scanning speed, and eventually stabilizes. Based on the relationship between thermal deformation and energy, the energy utilization efficiency of the SLM process under different conditions is calculated. The findings demonstrate that, within a certain range of power, the synergistic effect of laser power and scanning speed allows for an increase in energy utilization efficiency and a reduction in processing time while ensuring the mechanical performance of the formed parts. Consequently, this approach proves effective in lowering production costs for complex components based on SLM technology.

A Densification prediction Model of Selective Laser Melting Based on BP Neural Network

A Densification prediction Model of Selective Laser Melting Based on BP Neural Network

On the importance of heat source model determination for numerical modeling of selective laser melting of IN625

Accurate prediction of temperature distribution and melt pool geometry in metal additive manufacturing is highly dependent on the appropriate selection of heat source models. In the present study, a three-dimensional (3D) finite element (FE) heat transfer model is developed utilizing Abaqus by integrating different heat source models focusing on the surface heat source model and volumetric heat source model for selective laser melting (SLM) of Inconel 625 (IN625). All of the predicted peak temperatures, molten pool width, and depth are evaluated and compared with the experimental results cited from open literature. The relative error in simulated peak temperature and melt pool geometry from the surface heat source model is much higher in comparison to the volumetric heat transfer model. Further, a hybrid heat source model incorporating surface and volumetric heat models is developed to fulfill the numerical modeling of SLM of IN625 with high accuracy, which is highly recommended for the in-depth simulation study.

Numerical simulation on evolution process of molten pool and solidification characteristics of melt track in selective laser melting of ceramic powder

A three-dimensional high-fidelity physical model for selective laser melting (SLM) of ceramic powder was created based on computational fluid dynamics (CFD) to examine the physical mechanism of molten pool and solidified tracks at mesoscopic scale. The discrete element method (DEM) was used to generate a randomly packed powder bed, and the volume-of-fluid method (VOF) was applied to dynamically monitor the free surface of the molten pool. The formation mechanism and evolution characteristics of the molten pool were found and analyzed, and the effects of laser power on the typical characteristics of solidified ceramic tracks of SLM were investigated. The molten pool was eventually solidified into a concave geometric shape track by surface tension. The laser power played a significant impact on the shaping quality of solidified ceramic track. When the laser power was too low, the melt track suffers from severe porosity and distortion defects, which can be effectively solved with increasing laser power. The simulation results were validated via single track selective laser melting of TiC ceramic powder.

3D finite element modeling of selective laser melting for conduction, transition and keyhole modes

Selective Laser Melting (SLM) consists one of the most widely used 3D printing methods, capable of producing metallic parts of high density and quality. During SLM, complex physical mechanisms and phenomena are taking place, affecting the overall process, thus, extensive relevant research is conducted in the recent years. Along with the experimental research that is carried out, different modeling methodologies have been proposed to simulate the process and to gain a better understanding, exploiting the capability to predict and optimize the process' results. The current paper presents a modeling methodology to simulate the formation of the melting pool during a single track in SLM, for conduction, transition and keyhole modes depending on the utilized Volumetric Energy Density (VED). A heat transfer model has been combined with deformed geometry to simulate the material vaporization, depending on the VED, since the material vaporization mechanism can be considered as a major importance parameter in the keyhole formation. To retain the generality and the simplicity of the model, only one coefficient that needs an estimation was adopted, namely, the atom recombination factor βR, which is directly correlated with the VED, while other parameters were defined based on analytical solutions and basic physics models. The accuracy of the model was validated through a “blind” comparison with experimental results from literature in terms of melting pool depth and Heat Affected Zone (HAZ) depth and width, with the simulation result being in high agreement with experimental ones. Finally, conclusion regarding the material vaporization rate and the evolution of the process in a more microscopic level were also deduced.

Numerical and experimental investigations of built orientation dependent Johnson–Cook model for selective laser melting manufactured AlSi10Mg

Powder bed fusion based additive manufacturing techniques involve melting or sintering of powder particles via laser beams to join them in order to attain desired shapes. This study aims to provide basis for material constitutive parameters of widely used aluminum alloy AlSi10Mg alloy. Initially, tensile samples of AlSi10Mg alloy samples were manufactured by using SLM technology. Afterwards, through quasi-static and high temperature tensile tests, an attempt has been made to determine the Johnson–Cook material model of AlSi10Mg. in order to conduct quasi-static tensile tests, strain rates of 10−3 s−1, 10−2 s−1 and 5 × 10−2 s−1 were considered and tests were conducted at ambient temperature. Whereas, for high temperature tensile tests 24, 150, 300 °C temperature values were considered at the reference strain rate value of 10−3 s−1. The numerically simulated tensile results achieved by using the established Johnson–Cook model were then compared with experimental results. It was observed that the maximum error between the test and simulation results was around of 7.5%. The error percentage is well within the acceptable, thus proving the accuracy of the established material model.

Rapid prediction of the relationship between processing parameters and molten pool during selective laser melting of cobalt-chromium alloy powder: Simulation and experiment

In this study, the ANSYS19.0 (APDL) was used to build a finite element model of Selective Laser Melting (SLM) forming cobalt-chromium alloy. The model parameters included the conversion of material properties, convective heat transfer, physical properties with different temperatures, and so on. Based on this model, the dimension of molten pool, temperature gradient, liquid lifetime and cooling rate were predicted at different processing parameters. In addition, the reliability of the model was checked by conducting relevant experiments and studying the micro-hardness and microstructure of specimens. The metal parts with high density and excellent forming quality could be acquired with the scanning speed of 750 mm/s and laser power in the range of 160–200 W. Especially, when the laser power was 160 W, the molten pool existed for a suitable time (0.3133 ms), and the liquid phase acquired good fluidity which was beneficial to the overlap of adjacent molten pools.

On the incorporation of a micromechanical material model into the inherent strain method—Application to the modeling of selective laser melting

AbstractWhen developing reliable and useful models for selective laser melting processes of large parts, various simplifications are necessary to achieve computationally efficient simulations. Due to the complex processes taking place during the manufacturing of such parts, especially the material and heat source models influence the simulation results. If accurate predictions of residual stresses and deformation are desired, both complete temperature history and mechanical behavior have to be included in a thermomechanical model. In this article, we combine a multiscale approach using the inherent strain method with a newly developed phase transformation model. With the help of this model, which is based on energy densities and energy minimization, the three states of the material, namely, powder, molten, and resolidified material, are explicitly incorporated into the thermomechanically fully coupled finite‐element‐based process model of the micromechanically motivated laser heat source model and the simplified layer hatch model.

Selective Laser Melting under Variable Ambient Pressure: A Mesoscopic Model and Transport Phenomena

Recent reports on the selective laser melting (SLM) process under a vacuum or low ambient pressure have shown fewer defects and better surface quality of the as-printed products. Although the physical process of SLM in a vacuum has been investigated by high-speed imaging, the underlying mechanisms governing the heat transfer and molten flow are still not well understood. Herein, we first developed a mesoscopic model of SLM under variable ambient pressure based on our recent laser-welding studies. We simulated the transport phenomena of SLM 316L stainless steel powders under atmospheric and 100 Pa ambient pressure. For typical process parameters (laser power: 200 W; scanning speed: 2 m∙s −1 ; powder diameter: 27 μm), the average surface temperature of the cavity approached 2800 K under atmospheric pressure, while it came close to 2300 K under 100 Pa pressure. More vigorous fluid flow (average speed: 4 m∙s −1 ) was observed under 100 Pa ambient pressure, because the pressure difference between the evaporation-induced surface pressure and the ambient pressure was relatively larger and drives the flow under lower pressure. It was also shown that there are periodical ripple flows (period: 14 μs) affecting the surface roughness of the as-printed track. Moreover, the molten flow was shown to be laminar because the Reynolds number is less than 400 and is far below the critical value of turbulence; thus, the viscous dissipation is significant. It was demonstrated that under a vacuum or lower ambient pressure, the ripple flow can be dissipated more easily by the viscous effect because the trajectory length of the ripple is longer; thus, the surface quality of the tracks is improved. To summarize, our model elucidates the physical mechanisms of the interesting transport phenomena that have been observed in independent experimental studies of the SLM process under variable ambient pressure, which could be a powerful tool for optimizing the SLM process in the future.

Modeling Laser Beam Absorption of Metal Alloys at High Temperatures for Selective Laser Melting

Selective Laser Melting (SLM) is a promising technology to fabricate metallic components with complex geometries. However, determining process windows for specific materials and SLM machines by trial‐and‐error experiments is time consuming and expensive. Numerical simulation has been demonstrated as an efficient way to aid the process development. A crucial aspect is the absorption and reflection of the laser by the material. While there exist elaborated ray tracing approaches and absorption models, the most important drawback is to measure a reliable reflection coefficient of the material for different temperatures and phases. In this work, we discuss the application of a laser beam absorption model for SLM of metal alloys in the high temperature regime. The model bases on fundamental physical laws by taking reflection, refraction and absorption into account. The corresponding reflection coefficient is related to other physical quantities, like the electrical resistivity. The computed reflection coefficients are compared with reflection coefficient measurements of liquid NiFe alloys and with SLM of stainless steel 316L and Ti–6Al–4V. Finally, the laser beam absorption model is implemented in SAMPLE2D, a software for simulation of additive manufacturing on the powder scale, and is exemplary applied on single track melting experiments on compact Ti–6Al–4V plates.

Emergy-based environmental impact evaluation and modeling of selective laser melting

Additive manufacturing (AM) technologies, such as direct laser and selective laser melting (SLM) manufacturing, allow the fabrication of functional products with high added value. This paper proposes an emergy-based method for evaluating the environmental impact and economic cost of the SLM manufacturing process while considering the environmental flows (materials, energy, and wastes) and economic factors (time, costs, and quality). By analyzing the emergy flows in an SLM system, sustainable evaluation indexes are developed to estimate its sustainability level. Then, the method is applied to analyze the environmental impact and economic cost of the SLM of a part. The results show that the cost of the process for a single part is high, the net emergy yield ratio of the SLM system is low, and its environmental load rate is very high. The sustainability indexes of the system indicated a high environmental impact and low production efficiency. However, the waste emergy output ratio of the system was very low, which reflected the near-net-shape characteristics of SLM, indicating a high sustainability potential. The results of this study are expected to contribute to increased sustainability and optimization of SLM.

Reduced order modeling of selective laser melting: from calibration to parametric part distortion

Additive manufacturing is an appealing solution to produce geometrically complex parts, difficult to manufacture using traditional technologies. The extreme process conditions, in particular the high temperature, complex interactions and couplings, and rich metallurgical transformations that this process entails, are at the origin of numerous process defects. Therefore, the numerical simulation of the process is gaining the interest of both the scientific and the industrial communities. However, simulating that process demands impressive computational resources, limiting high resolution simulations to the microscopic and mesoscopic scales. This paper proposes a thermo-mechanical modeling framework at the process scale as well as its associated reduced order simulation counterpart, enabling the parametric evaluation of the part distortion. It deeply addresses the process calibration using a high-resolution computational procedure based on the use of an in-plane-out-of-plane separated representation at the heart of the so-called Proper Generalized Decomposition (PGD), as well as the analysis of the transient thermal effects, defining the conditions in which the thermal and mechanical analyses can be decoupled.

Reduced order modeling of selective laser melting: from calibration to parametric part distortion

Reduced order modeling of selective laser melting: from calibration to parametric part distortion

Reduced order modeling of selective laser melting: from calibration to parametric part distortion

Reduced order modeling of selective laser melting: from calibration to parametric part distortion

Numerical simulation of selective laser melting with local powder shrinkage using FEM with the refined mesh

A mathematical model of selective laser melting (SLM) of fine-grained metallic powders under the pulse laser annealing conditions has been developed. The processed powder bed is considered in the approximation of continuous medium where its effective thermophysical properties depend on local porosity. The model allows simulation of unsteady distributions of temperature, specific enthalpy, local porosity, morphology and thickness of the processed track. In the paper, all stages of problem analysis are described including its mathematical formulation and numerical implementation. To take into account shrinkage of the powder layer during sintering and remelting, the numerical model utilizes the arbitrary Lagrangian–Eulerian (ALE) method. Thus the finite element mesh provides robust control of quality and dynamic remeshing through adaptive mesh refinement. Using the proposed numerical model the unsteady thermal fields and local porosity of a Fe-based powder layer processed with a pulsed laser has been investigated.

Modelling of selective laser melting process with adaptive remeshing

ABSTRACTSelective laser melting involves manufacturing of a part layer-by-layer by localised melting and solidification of metal powders. The geometry, composition, structure and property of the solidified deposit are significantly influenced by repeated exposure to the laser beam at a high scanning speed. A computationally efficient heat transfer model of selective laser melting is reported here using the finite element method with adaptive remeshing. The model has incorporated a very fine mesh, moving with the laser beam, to capture the local thermal gradient in and around the melt pool. A gradually varying coarser mesh is used away from the melt pool. The computed results are verified with that calculated using a uniform fine mesh and against reported experimental observations.

A thermo-metallurgical-mechanical model for selective laser melting of Ti6Al4V

A thermo-metallurgical-mechanical coupling model is developed to predict temperature, solid-state phase and residual stress fields for the multi-track multi-layer selective laser melting process of Ti6Al4V. The model considers the solid-state phase transformation (SSPT) and powder-liquid-solid transition which includes melting, vaporization, solidification, shrinkage and cooling phenomena. The thermal analysis is based on the transient heat conduction problem with a volumetric heat source describing the laser absorption and scattering in the powder bed. The volume fraction evolution of metallurgical phases is determined by temperature history and used to obtain the volumetric change strain due to the SSPT. An elasto-plastic constitutive law considering the strains that are induced by thermal gradients and the SSPT is proposed to evaluate stress fields. Modelling results reveal that the consideration of the SSPT leads to the decrease of tensile residual stresses and increase of compressive residual stresses, and the residual stress component in the scanning direction is larger than the other two stress components.

Predictive Model for Thermal and Stress Field in Selective Laser Melting Process—Part I

During the part forming in laser powder bed fusion process, thermal distortion is one big problem due to the thermal stress which is caused by the high cooling rate and temperature gradient. Therefore, it is important to know the effect of process parameters on thermal and stress evolution in the melt zone. In this paper, a 3D finite element model for Selective Laser Melting (SLM) process based on sequentially coupled thermo-mechanical field analysis was developed for accurately predicting thermal history and surface features, like distortion and residual stress. Temperature dependent material properties for performed material 304L stainless steel are incorporated into the model capturing the change from powder to fully dense solid stainless steel. Surface temperature gradients and thermal stress were fully presented in the development of different parameter sets, which designed for the probability of reducing defect formation. Simulation results showed that the sequent thermal cyclic melting in successive scanned tracks resulted in alternating compressive and tensile thermal stresses. A predictive model for thermal and stress field in large part by selective laser melting process is come up in Part II. After the parts cooled down to room temperature, higher residual stresses were found in longitudinal stress. This paper will provide guidance on how to achieve minimum residual stresses and deformations by the study of the process parameters.