scholarly journals Development of an Elongated Ellipsoid Heat Source Model to Reduce Computation Time for Directed Energy Deposition Process

2021 ◽  
Vol 8 ◽  
Author(s):  
Vaibhav Nain ◽  
Thierry Engel ◽  
Muriel Carin ◽  
Didier Boisselier ◽  
Lucas Seguy
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Heat Source ◽  
Correction Factor ◽  
Energy Deposition ◽  
Computation Time ◽  
Metal Deposition ◽  
Time Increment ◽  
Directed Energy ◽  
Simulation Time

Directed Energy Deposition (DED) Additive Manufacturing process for metallic parts are becoming increasingly popular and widely accepted due to their potential of fabricating parts of large dimensions. The complex thermal cycles obtained due to the process physics results in accumulation of residual stress and distortion. However, to accurately model metal deposition heat transfer for large parts, numerical model leads to impractical computation time. In this work, a 3D transient finite element model with Quiet/Active element activation is developed for modeling metal deposition heat transfer analysis of DED process. To accurately model moving heat source, Goldak’s double ellipsoid model is implemented with small enough simulation time increment such that laser moves a distance of its radius over the course of each increment. Considering thin build-wall of Stainless Steel 316L fabricated with different process parameters, numerical results obtained with COMSOL 5.6 Multi-Physics software are successfully validated with experiment temperature data recorded at the substrate during the fabrication of 20 layers. To reduce the computation time, elongated ellipsoid heat input model that averages the heat source over its entire path is implemented. It has been found that by taking such large time increments, numerical model gives inaccurate results. Therefore, the track is divided into several sub-tracks, each of which is applied in one simulation increment. In this work, an investigation is done to find out the correct simulation time increment or sub-track size that leads to reduction in computation time (5–10 times) but still yields sufficiently accurate results (below 10% of relative error on temperature). Also, a Correction factor is introduced that further reduces computation error of elongated heat source. Finally, a new correlation is also established in finding out the correct time increment size and correction factor value to reduce the computation time yielding accurate results.

An Appropriate Design in Dimensions of Submount with Extra-Low Thermal Resistance for High Power LED

2013 ◽  
Vol 284-287 ◽  
pp. 824-828
Author(s):  
Farn Shiun Hwu ◽  
Ho Chih Cheng ◽  
Ya Hui Hu ◽  
Gwo Jiun Sheu
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Numerical Model ◽  
Aspect Ratio ◽  
Heat Source ◽  
Thermal Resistance ◽  
Symmetry Axis ◽  
Contact Ratio ◽  
Convective Effect ◽  
Internal Thermal Resistance

A numerical simulation model to obtain the extra-low internal thermal resistance for submount of LED is presented. The 3-D numerical model for calculating thermal resistance is demonstrated on examining the aspect ratio of submount, the contact ratio between chip and submount, and the surrounding condition. According to the analysis by accurate numerical simulations of heat transfer; the appropriate dimensions for different conditions of ambient are determined. The thickness of submount should be over a specially designated value. Besides, a higher contact ratio between heat source and submount, a larger external convective effect, and the heat dissipated from symmetry axis of submount will decrease the spreading thermal resistance.

scholarly journals Optimization of Thin Walls With Sharp Corners in SS316L and IN718 Alloys Manufactured with Laser Metal Deposition

2020 ◽  
Author(s):  
Juan Carlos Pereira ◽  
Herman Borokov ◽  
Fidel Zubiri ◽  
Mari Carmen Guerra ◽  
Josu Caminos
Keyword(s):  
Layer Thickness ◽  
Energy Deposition ◽  
Deposition Process ◽  
Metal Deposition ◽  
Powder Materials ◽  
Laser Metal Deposition ◽  
Thin Walls ◽  
Directed Energy ◽  
Position Parameter ◽  
Sharp Corners

In this work, the manufacture of thin walls with sharp corners has been optimized by adjusting the limits of a 3-axis cartesian kinematics through data recorded and analyzed off-line, such as axis speed, acceleration and the positioning of the X and Y axes. The study was carried out with two powder materials (SS316L and IN718) using the directed energy deposition process with laser. 1 mm thick walls were obtained with only one bead per layer and straight/sharp corners at 90º. After adjusting the in-position parameter G502 for positioning precision on the FAGOR 8070 CNC system, it has been possible to obtain walls with minimal accumulation of material in the corner, and with practically constant layer thickness and height, with a radii of internal curvature between 0.11 and 0.24 mm for two different precision configuration. The best results have been obtained by identifying the correct balance between the decrease in programmed speed and the precision in the positioning to reach the point defined as wall corner, with speed reductions of 29% for a programmed speed of 20 mm/s and 61% for a speed of 40 mm/s. The walls show minimal defects such as residual porosities, and the microstructure is adequate.

scholarly journals History Reduction by Lumping for Time-Efficient Simulation of Additive Manufacturing

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 58 ◽  
Author(s):  
Andreas Malmelöv ◽  
Andreas Lundbäck ◽  
Lars-Erik Lindgren
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Residual Stresses ◽  
Energy Deposition ◽  
Computation Time ◽  
Layer By Layer ◽  
Efficient Simulation ◽  
Computational Welding Mechanics ◽  
Directed Energy ◽  
Short Time

Additive manufacturing is the process by which material is added layer by layer. In most cases, many layers are added, and the passes are lengthy relative to their thicknesses and widths. This makes finite element simulations of the process computationally demanding owing to the short time steps and large number of elements. The classical lumping approach in computational welding mechanics, popular in the 80s, is therefore, of renewed interest and is evaluated in this work. The method of lumping means that welds are merged. This allows fewer time steps and a coarser mesh. It was found that the computation time can be reduced considerably, with retained accuracy for the resulting temperatures and deformations. The residual stresses become, to a certain degree, smaller. The simulations were validated against a directed energy deposition (DED) experiment with alloy 625.

scholarly journals Numerical modeling of the thermoelectric cooler with a complementary equation for heat circulation in air gaps

Open Physics ◽  
2017 ◽  
Vol 15 (1) ◽  
pp. 27-34 ◽  
Author(s):  
En Fang ◽  
Xiaojie Wu ◽  
Yuesen Yu ◽  
Junrui Xiu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Heat Source ◽  
Thermoelectric Cooler ◽  
Thermoelectric Coolers ◽  
Air Gaps ◽  
Experimental Apparatus ◽  
A Tec ◽  
Complementary Equation

AbstractIn this paper, a numerical model is developed by combining thermodynamics with heat transfer theory. Taking inner and external multi-irreversibility into account, it is with a complementary equation for heat circulation in air gaps of a steady cooling system with commercial thermoelectric modules operating in refrigeration mode. With two modes concerned, the equation presents the heat flowing through air gaps which forms heat circulations between both sides of thermoelectric coolers (TECs). In numerical modelling, a TEC is separated as two temperature controlled constant heat flux reservoirs in a thermal resistance network. In order to obtain the parameter values, an experimental apparatus with a commercial thermoelectric cooler was built to characterize the performance of a TEC with heat source and sink assembly. At constant power dissipation, steady temperatures of heat source and both sides of the thermoelectric cooler were compared with those in a standard numerical model. The method displayed that the relationship betweenΦfand the ratio$\varPhi_{{\text c}}'/\varPhi_{{\text c}}$was linear as expected. Then, for verifying the accuracy of proposed numerical model, the data in another system were recorded. It is evident that the experimental results are in good agreement with simulation(proposed model) data at different heat transfer rates. The error is small and mainly results from the instabilities of thermal resistances with temperature change and heat flux, heat loss of the device vertical surfaces and measurements.

scholarly journals Thermal analysis of Wire Arc Additive Manufacturing process

2021 ◽  
Author(s):  
Mohamed Belhadj ◽  
Sana Werda ◽  
Asma Belhadj ◽  
Robin Kromer ◽  
Philippe Darnis
Keyword(s):  
Additive Manufacturing ◽  
Numerical Model ◽  
Heat Source ◽  
Manufacturing Process ◽  
High Energy ◽  
Metal Deposition ◽  
Innovative Technology ◽  
Thermal Cycles ◽  
Predictive Tool ◽  
Wire Arc Additive Manufacturing

Wire arc additive manufacturing process (WAAM) is an innovative technology that offers freedom in terms of designing functional parts, due to its ability to manufacture large and complex workpieces with a high rate of deposition. This technology is a metal AM process using an electric arc heat source. The parts manufactured are affected by thermal residual stresses due to high-energy input between wire and workpiece despite numerous advantages with this technology. It could cause severe deformation and change the global mechanical response. A 3D transient thermal model was created to evaluate the thermal gradients and fields during metal deposition. The material used in this study is a steel alloy (S355JR-AR). This numerical model takes into account the heat dissipation through the external environment and the heat loss through the cooling system under the base plate. Birth-element activation strategy was used to generate warm solid part following the movement of the heat source. The metal deposition is defined with constant welding speed. Goldak model was used to simulate the heat source in order to have a realistic heat flow distribution. Results were in concordance for thermal cycles at different points comparing with experimental results issued from bibliography in terms of: (1) Temperature maximum, (2) Thermal cycles and (3) Cooling gradient phase. This study enabled to check the numerical model and used as a predictive tool

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