Analytic and Finite Element Solution of Temperature Profiles in Welding for Transient State and Quasi Steady State Using Point Heat Source Model

Selective laser melting (SLM) and laser cladding are laser additive manufacturing methods that have been developed for application to the near-net-shape process and 3D printing. The temperature distributions and track profiles of SLM and clad layers require additional in-depth investigation to optimize manufacturing processes. This research involved developing a tailored laser heat source model that contains a comprehensive selection of laser beam characteristics and can be used in finite element analysis of the laser melting process. This paper presents a systematic experimental validation of the applicability of the proposed laser heat source model to single-track Nd:YAG and CO2 laser melting simulations. The evolution of the melt pool isotherms and the variation in track profiles caused by adjusting the laser power and scanning speed were numerically predicted and experimentally verified. Appropriate process parameters and the threshold power for continuous track layer formation were determined. The balling phenomenon on preplaced powder was observed at power levels below the threshold values. Nd:YAG laser melting resulted in a wide and shallow track profile, which was adequately predicted using the numerical simulation. CO2 laser melting resulted in a triangular track profile, which deviated slightly from the finite element prediction. The results indicated a high level of consistency between the experimental and the numerical results regarding track depth evolution, whereas the numerically predicted track width evolution deviated slightly from the experimentally determined track width evolution. This parametric laser melting study validated the applicability of the proposed laser heat source model in numerical analysis of laser melting processes such as SLM and laser cladding.

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Novel Calibration Strategy for Validation of Finite Element Thermal Analysis of Selective Laser Melting Process Using Bayesian Optimization

Materials ◽

10.3390/ma14174948 ◽

2021 ◽

Vol 14 (17) ◽

pp. 4948

Author(s):

Masahiro Kusano ◽

Houichi Kitano ◽

Makoto Watanabe

Keyword(s):

Thermal Analysis ◽

Finite Element ◽

Heat Source ◽

Selective Laser Melting ◽

High Speed ◽

Thermal Analyses ◽

Source Model ◽

Bayesian Optimization ◽

Laser Melting ◽

Heat Source Model

Selective laser melting (SLM) produces a near-net-shaped product by scanning a concentrated high-power laser beam over a thin layer of metal powder to melt and solidify it. During the SLM process, the material temperature cyclically and sharply rises and falls. Thermal analyses using the finite element method help to understand such a complex thermal history to affect the microstructure, material properties, and performance. This paper proposes a novel calibration strategy for the heat source model to validate the thermal analysis. First, in-situ temperature measurement by high-speed thermography was conducted for the absorptivity calibration. Then, the accurate simulation error was defined by processing the cross-sectional bead shape images by the experimental observations and simulations. In order to minimize the error, the optimal shape parameters of the heat source model were efficiently found by using Bayesian optimization. Bayesian optimization allowed us to find the optimal parameters with an error of less than 4% within 50 iterations of the thermal simulations. It demonstrated that our novel calibration strategy with Bayesian optimization can be effective to improve the accuracy of predicting the temperature field during the SLM process and to save the computational costs for the heat source model optimization.

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Application of discrete distribution point heat source model to simulate multipass weld thermal cycles in medium thick plates

Science and Technology of Welding & Joining ◽

10.1179/136217104225017189 ◽

2004 ◽

Vol 9 (1) ◽

pp. 72-82 ◽

Cited By ~ 4

Author(s):

A. J. Ramirez ◽

S. D. Brandi

Keyword(s):

Heat Source ◽

Discrete Distribution ◽

Source Model ◽

Point Heat Source ◽

Thermal Cycles ◽

Heat Source Model ◽

Thick Plates ◽

Distribution Point ◽

Multipass Weld

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Estimation of Heat Source Model’s Parameters for GMAW with Non-linear Global Optimization—Part I: Application of Multi-island Genetic Algorithm

Metals ◽

10.3390/met10070885 ◽

2020 ◽

Vol 10 (7) ◽

pp. 885

Author(s):

Changmin Pyo ◽

Jisun Kim ◽

Jaewoong Kim

Keyword(s):

Genetic Algorithm ◽

Finite Element Analysis ◽

Finite Element ◽

Global Optimization ◽

Heat Source ◽

Source Model ◽

Boundary Line ◽

Welding Deformation ◽

Heat Source Model ◽

Element Analysis

Estimating the thermo-elasto-plastic deformation by arc welding through finite element analysis has been used in various industrial fields. The Goldak heat source model is one of the most important and widely used models in finite element analysis, and its parameters are estimated based on the results of previous studies and tests. Part I of this study focused on the adequate heat source model, and the study for the welding deformation with the moving heat source will be done on the latter research. This study used the parameters of Goldak’s heat source model, weld efficiency, and the location of the heat source as design variables, and defined the Heat Affected Zone (HAZ) boundary line of Bead on Plate (BOP) welding as the target. BOP welding was performed using SS400 plates, the HAZ boundary line was determined based on examining the shape of the cross-section, and the optimization condition was that temperature inside the boundary line exceeded 727 °C while the temperature outside the line did not exceed 727 °C during the welding process. During this process, a multi-island genetic algorithm (non-linear global optimization method) was used to obtain the optimal results out of 1000 candidate groups, in which the HAZ boundary was similar to the experimental results. Applying a global optimization algorithm to determine the parameters of the most important heat source model to analyze welding deformation is significant, and this may be applied in various industrial fields that use welding including shipbuilding, aviation, and machinery industries.

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