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

Metals ◽  
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.

scholarly journals A Study on Welding Deformation in Fiber Laser Welding of 9% Nickel Steel through Finite Element Analysis Part I: Implementation of Welding Heat Source Model

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2188
Author(s):  
Changmin Pyo ◽  
Jaewoong Kim ◽  
Du-Song Kim
Keyword(s):  
Natural Gas ◽  
Heat Source ◽  
Laser Welding ◽  
Fiber Laser ◽  
Source Model ◽  
Heat Transfer Analysis ◽  
Welding Deformation ◽  
Nickel Steel ◽  
Fiber Laser Welding ◽  
Heat Source Model

Due to various environmental regulations, the demand for natural gas, i.e., a clean energy, is expected to increase continuously. In terms of efficient storage and transportation of natural gas, liquefied natural gas has an advantageous volume of 1/600 compared to natural gas, but the materials that can be used at a cryogenic temperature of −163 °C are limited. A 9% nickel steel is a material recommended by IMO through IGC. It has excellent mechanical properties compared to other cryogenic materials, but its use has been limited due to its disadvantages in arc welding. Therefore, the main topic of this study is the automatic welding of 9% nickel steel using fiber laser and its purpose is to predict the welding deformation during fiber laser welding. First, an investigation was conducted to find the fiber laser welding heat source. A model that can cover all the models in prior studies such as curve, exponential, conical, conical-conical combination, and conical-cylinder combination models was proposed and the heat source model was constructed in a multi-layer format. Heat transfer analysis was performed using the ratio of a heat source radius and heat energy of each layer as a variable and the pass or failure of a heat source was determined by comparing the analysis results to the experimental results. By changing the variables in conjunction with the optimization algorithm, the main parameters of a passed heat source model were verified in a short period of time. In addition, the tendency of parameters according to the welding speed was checked.

Stochastic Methods Applied to Structural Mechanics

2018 ◽  
pp. 199-220
Author(s):  
Siham Ouhimmou
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Global Optimization ◽  
Transformation Method ◽  
Stochastic Methods ◽  
Element Analysis ◽  
Local Method ◽  
Structural Problem ◽  
Finite Element Software ◽  
The Finite Element Analysis

Uncertainty modelling with random variables motivates the adoption of advanced PTM for reliability analysis to solve problems of mechanical systems. Probabilistic transformation method (PTM) is readily applicable when the function between the input and the output of the system is explicit. When these functions are implicit, a technique is proposed that combines finite element analysis (FEA) and probabilistic transformation method (PTM) that is based on the numerical simulations of the finite element analysis (FEA) and the probabilistic transformation method (PTM) using an interface between finite element software and Matlab. Structure problems are treated with the proposed technique, and the obtained results are compared to those obtained by the reference Monte Carlo method. A second aim of this work is to develop an algorithm of global optimization using the local method SQP. The proposed approach MSQP is tested on test functions comparing with other methods, and it is used to resolve a structural problem under reliability constraints.

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