Role of Marangoni Convection in a Repetitive Laser Melting Process

2020 ◽  
Vol 978 ◽  
pp. 34-39 ◽  
Author(s):  
Saurabh Das ◽  
Satya Prakash Kar
Keyword(s):  
Molten Metal ◽  
Laser Scanning ◽  
Marangoni Convection ◽  
Melting Process ◽  
Flow Dynamics ◽  
Work Piece ◽  
Algebraic Equations ◽  
Scanning Velocity ◽  
Melt Pool ◽  
Marangoni Force

To effectively interpret the fluid flow dynamics in the molten metal pool, a numerical model was established. The moving repetitive Gaussian laser pulse is irradiated in the work piece. The consideration of laser scanning speed makes the transport phenomena complex. The continuity and momentum equations are solved to get the flow velocity of the molten metal in the melt pool. The energy equation is solved to know the temperature field in the work piece. The algebraic equations obtained after discretization of the governing equations by Finite Volume Method (FVM) are then solved by the Tri Diagonal Matrix Method. Enthalpy-porosity technique is used to capture the position of the melt front which determines the shape of the melt pool. Marangoni convection is considered to know its effect on the shape of the melt pool. The surface tension coefficient is taken as both positive and negative value while calculating the Marangoni force. The two possible cases will cause the Marangoni force to distort the flow dynamics in the melt pool . It's dominance over the buoyancy force in controlling the melt pool shape is focused in the present study. Further, the present model will present an insight to the consequences of laser scanning velocity over the melt pool dimensions and shape.

Thermal Modeling of Transport Phenomena for a Pulsed Laser Melting Process

2020 ◽  
Vol 978 ◽  
pp. 114-120
Author(s):  
Siladitya Sukumar ◽  
Satya Prakash Kar
Keyword(s):  
Transport Phenomena ◽  
Pulsed Laser ◽  
Melting Process ◽  
Maximum Temperature ◽  
Work Piece ◽  
Computational Domain ◽  
Laser Melting ◽  
Laser Applications ◽  
Melt Pool ◽  
Volume Method

Single pulsed laser melting in a cylindrical titanium alloy work piece is studied numerically using an axisymmetric model. Finite volume method and Tri-Diagonal Matrix Algorithm (TDMA) are used for discretization of the energy equation and solving the resulting algebraic equation respectively in order to obtain temperature distribution inside the computational domain. Heat losses from the irradiated surface takes place through convection and radiation and other surfaces are kept insulated. A volumetric and Gaussian laser is irradiated on the work piece. Validation of the present model with the existing literature is done first and the results agree very well. Then, the detailed transport phenomena during the laser melting process is studied using the model. The enthalpy porosity technique is used track the melt pool shape and size. The role of natural convection and Marangoni convection in controlling the shape of melt pool is discussed. Maximum temperature results at domain centre and it then decreases exponentially along the axial and radial direction of the work piece because of Gaussian nature of the pulse. The numerical results obtained can provide the direction to develop models for all type of laser applications used in the industry.

Numerical Investigation of Selective Laser Melting Process for 904L Stainless Steel

2012 ◽  
Author(s):  
Miranda Fateri ◽  
Andreas Gebhardt ◽  
Maziar Khosravi
Keyword(s):  
Heat Flux ◽  
Stainless Steel ◽  
Selective Laser Melting ◽  
Melting Process ◽  
Full Density ◽  
Laser Melting ◽  
Scanning Velocity ◽  
Selective Laser Melting Process ◽  
Fine Mesh ◽  
Melt Pool

Selective Laser Melting process (SLM) is an important manufacturing method for producing complex geometries which allows for creation of full density parts with similar properties as the bulk material without extensive post processing. In SLM process, laser power, beam focus diameter, and scanning velocity must be precisely set based on the material properties in order to produce dense parts. In this study, Finite Element Analysis (FEA) method is employed in order to simulate and analyze a single layer of 904L Stainless Steel. A three-dimensional transient thermal model of the SLM process based on phase change enthalpy, irradiation scattering, and heat conductivity of powder is developed. The laser beam is modeled as a moving heat flux on the surface of the layer using a fine mesh which allows for a variation of the shape and distribution of the beam. In this manner, various Gaussian distributions are investigated and compared against single and multi-element heat flux sources. The melt pool and temperature distribution in the part are numerically investigated in order to determine the effects of varying laser intensity, scanning velocity as well as preheating temperature. The results of the simulation are verified by comparing the melt pool width as a function of power and velocity against the experimentally obtained results. Lastly, 3D objects are fabricated with a SLM 50 Desktop machine using the acquired optimized process parameters.

Mesoscopic Simulation Model to Predict Temperature Distribution and Melt Pool Size During Selective Laser Scanning

2018 ◽  
Author(s):  
Subin Shrestha ◽  
Kevin Chou
Keyword(s):  
Laser Scanning ◽  
Numerical Study ◽  
Melting Process ◽  
Pool Size ◽  
Scale Model ◽  
Single Track ◽  
Track Width ◽  
Mesoscopic Simulation ◽  
Melt Pool ◽  
Melt Pool Size

Selective Laser Melting (SLM) has been a major subject of study in the field of powder bed additive manufacturing (AM) process. It is desired to know the melt pool size and the associated thermal gradient during the powder melting process. However, there are challenges associated with accurately measuring the melt pool size as a whole by experiment alone. Therefore, the combination of experimental and numerical study may help analyze the melt pool shape in a better way. In this study, a 3D powder scale model using volume of fluid (VOF) approach has been developed using ANSYS FLUENT. A temperature dependent material property is defined and then volumetric heat source is applied to melt the powder particles. The single track results obtained from the simulation are compared with the experiment and the results show that single track width predicted by the simulation is in good agreement with the experimental counterpart. The predicted track width is within 10% error.

scholarly journals Fabrication of Mesh Patterns Using a Selective Laser-Melting Process

2019 ◽  
Vol 9 (9) ◽  
pp. 1922 ◽  
Author(s):  
Tae Woo Hwang ◽  
Young Yun Woo ◽  
Sang Wook Han ◽  
Young Hoon Moon
Keyword(s):  
Selective Laser Melting ◽  
Laser Scanning ◽  
Dimensional Accuracy ◽  
Base Plate ◽  
Steel Powder ◽  
Melting Process ◽  
304 Stainless Steel ◽  
Process Conditions ◽  
Laser Melting ◽  
Metal Mesh

The selective laser-melting (SLM) process can be applied to the additive building of complex metal parts using melting metal powder with laser scanning. A metal mesh is a common type of metal screen consisting of parallel rows and intersecting columns. It is widely used in the agricultural, industrial, transportation, and machine protection sectors. This study investigated the fabrication of parts containing a mesh pattern from the SLM of AISI 304 stainless steel powder. The formation of a mesh pattern has a strong potential to increase the functionality and cost-effectiveness of the SLM process. To fabricate a single-layered thin mesh pattern, laser layering has been conducted on a copper base plate. The high thermal conductivity of copper allows heat to pass through it quickly, and prevents the adhesion of a thin laser-melted layer. The effects of the process conditions such as the laser scan speed and scanning path on the size and dimensional accuracy of the fabricated mesh patterns were characterized. As the analysis results indicate, a part with a mesh pattern was successfully obtained, and the application of the proposed method was shown to be feasible with a high degree of reliability.

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

Prediction of Melt-Pool Characteristics in SLM Process for Ti6Al4V Using a Semi-Analytical Model

2021 ◽  
Author(s):  
Shubhra Kamal Nandi ◽  
Rakesh Kumar ◽  
Anubhav ◽  
Anupam Agrawal
Keyword(s):  
Temperature Distribution ◽  
Finite Volume ◽  
Computational Models ◽  
Single Layer ◽  
Layer By Layer ◽  
Scanning Velocity ◽  
Melt Pool ◽  
Alternating Direction ◽  
Volume Method ◽  
Melt Pool Characteristics

Abstract Selective Laser Melting (SLM) is a powder-based layer-by-layer manufacturing technique to produce metallic customized shape components. The exceptionally high thermal gradient induces residual stress and distorts the part geometry affecting the yield quality. Computational models are instrumental in optimizing the process controls to fabricate high-quality components, and hence several such methods have been explored to simulate the thermal behavior of the process and the heat transfer in the melt-pool. Most of the practiced techniques are computationally expensive, making it infeasible to perform a parametric study. Based on closed-form exact heat conduction solution and Finite Volume Method (FVM), a pseudo-analytical thermal modeling approach has been employed to estimate the melt-pool characteristics and temperature distribution of the SLM process. A moving volumetric Gaussian heat source laser model and Green’s function have been adopted to model the heat input by conduction. The heat loss by conduction and convection has been calculated by implementing Finite Volume discretized equations on a 2-dimensional thin-walled domain with appropriate part boundary conditions. Additionally, the Alternating Direction Implicit iterative technique has been implemented for the fast convergence of the simulation. The model is used to demonstrate the influence of the process parameters and non-linear material phase change for a single-line single layer and multilayer part fabrication. The computed melt-pool dimensions and temperature distribution for varying laser-power, scanning velocity, and layer thickness for Ti6Al4V are validated with the experimental data from the literature with fair agreements.

scholarly journals Influence of Material Property Variation on Computationally Calculated Melt Pool Temperature during Laser Melting Process

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 456 ◽  
Author(s):  
Sazzad H. Ahmed ◽  
Ahsan Mian
Keyword(s):  
Thermal Conductivity ◽  
Specific Heat ◽  
Process Parameters ◽  
Laser Power ◽  
Laser Scanning ◽  
Peak Temperature ◽  
Powder Layer ◽  
Laser Melting ◽  
Melt Pool ◽  
Melt Pool Temperature

Selective Laser Melting (SLM) is a popular additive manufacturing (AM) method where a laser beam selectively melts powder layer by layer based on the building geometry. The melt pool peak temperature during build process is an important parameter to determine build quality of a fabricated component by SLM process. The melt pool temperature depends on process parameters including laser power, scanning speed, and hatch space as well as the properties of the build material. In this paper, the sensitivity of melt pool peak temperature during the build process to temperature dependent material properties including density, specific heat, and thermal conductivity are investigated for a range of laser powers and laser scanning speeds. It is observed that the melt pool temperature is most sensitive to melt pool thermal conductivity of the processed material for a set of specific process parameters (e.g., laser power and scan speed). Variations in the other mechanical–physical properties of powder and melt pool such as density and specific heat are found to have minimal effect on melt pool temperature.

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