Query: Numerical simulation of laser arc hybrid welding 

title: Numerical simulation of laser arc hybrid welding of high strength steel

title: ANSYS Application on Numerical Simulation of Laser arc Hybrid Welding
abstract: This paper use thick high strength steel for the study, use finite element analysis, combined with numerical calculation. The results and conclusions of the numerical simulation coincide with each other.

title: Model for Numerical Simulation of Temperature Field and Bead Profile in Hybrid Laser Arc Welding of T Joint
abstract: The development and implementation of automated and robotic welding production lines is an urgent task of the last decade. The wide application of hybrid laser arc welding (HLAW) is difficult due to sensitivity to changes in a large number of process parameters, as well as fluctuations in gap between welded edges and to the edge preparation quality. The need to solve these problems has led to the development of methods and algorithms for the numerical simulation of the HLAW. The developed mathematical model is able to predict effects of process parameters and heat flux distribution of the hybrid heat source on the formation of the surface of weld bead and temperature field in welded joint. The model is divided into the following sub models: wire melting; heat conduction in the molten pool and the substrate; formation of the surface of the weld. Comparison of the calculated and experimental data of melting rate of the electrode wire and the formation of welded joints during HLAW of T joint showed good agreement. The effect of fluctuations in the process parameters on the quality of welded joints was established by simulation.

title: Numerical simulation of keyhole behaviors and fluid dynamics in laser gas metal arc hybrid welding of ferrite stainless steel plates
abstract: The fluid dynamics in weld pool and keyhole behaviors in laser gas metal arc hybrid welding play a dominant role in affecting the weld quality of ferrite stainless steel plates. In this study, a transient model is developed for numerical simulation of the keyhole dynamics and heat transfer fluid flow in hybrid weld pool. The heat, mass and momentum transfer due to droplets as well as the interaction between laser and arc are taken into account. The formation, expansion and sustainment of keyhole in weld pool are numerically simulated, and the transient variation of keyhole is demonstrated in three stages. The weld pool and keyhole shapes and sizes, and the fluid flow and thermal field in hybrid weld pool are quantitatively analyzed. The model is validated by hybrid welding experiments on ferrite stainless steel plates. It lays foundation for optimizing the process parameters in hybrid welding.

title: Numerical simulation for pulsed laser gas tungsten arc hybrid welding of magnesium alloy
abstract: Based on the extended application of COMSOL multiphysics, a novel dual heat source model for pulsed laser gas tungsten arc (GTA) hybrid welding was established. This model successfully solved the problem of simulation inaccuracy caused by energy superposition effect between laser and arc due to their different physical characteristics. Numerical simulation for pulsed laser GTA hybrid welding of magnesium alloy process was conducted, and the simulation indicated good agreements with the measured thermal cycle curve and the shape of weld beads. Effects of pulse laser parameters (laser excited current, pulse duration, and pulse frequency) on the temperature field and weld pool morphology were investigated. The experimental and simulation results suggest that when the laser pulse energy keeps constant, welding efficiency of the hybrid heat source is increased by increasing laser current or decreasing pulse duration due to the increased ratio of the weld bead depth to width. With large laser currents, severe spatters tend to occur. For optimized welding process, the laser current should be controlled in the range of 150 175 A, the pulse duration should be longer than 1 ms, and the pulse frequency should be equal to or slightly greater than 20 Hz.

title: Numerical and experimental investigation of the formation mechanism and the distribution of the welding residual stress induced by the hybrid laser arc welding of AH36 steel in a butt joint configuration
abstract: Formation mechanism of the welding residual stress (WRS) is a key part of welding research. However, there is a lack of meaningful numerical models of the WRS. In this work, a thermal metallurgical mechanical (TMM) model was developed using SYSWELD to investigate the distribution and the formation mechanism of WRS during the hybrid laser arc welding of AH36 steel. A series of simulations were conducted to explore the effects of various factors on the WRS. The numerical results matched well with the experimental data. The computational accuracy was improved by considering the typical "wine glass" weld profile and the dilution rate during simulation. The evolution of the WRS is strongly affected by the interaction of phase transformation and strain hardening. The austenite martensite transformation has a great potential to reduce the WRS whereas the austenite bainite transformation produces high levels of WRS. The phase transformation temperature has a great influence on WRS.

title: Numerical analysis of hybrid plasma in fiber laser arc welding
abstract: A 3D non axisymmetric hybrid plasma model in fiber laser arc welding is developed, in which the laser induced plasma is considered as ejecting vapor from keyhole with specific radius, temperature and velocity. The effects of the ejecting vapor temperature and velocity, and the distance between laser and arc are simulated and discussed. From the simulation results, the height of the laser induced plasma is higher with lower ejecting vapor temperature, bigger ejecting vapor velocity and larger distance between laser and arc. The temperature of the hybrid plasma decreases compared with the temperature of arc plasma under all the simulation parameters, which is very benefical to reduce distortion resulted from bigger heat input. The current density of the hybrid plasma has a complex dependence on the studying parameters. When the ejecting temperature is 10 000 K, or the ejecting velocity is 50 m s 1 or distance between laser and arc is 4 mm, the current density in the laser induced plasma affected zone is larger than that of the arc plasma at the same position, while it becomes smaller under other simulation parameters. In addition, the current becomes more concentrated with lower vapor temperature, larger vapor velocity and smaller distance between laser and arc.

title: Characterization of different light intensity areas for plasma induced during fiber laser arc hybrid welding
abstract: In this paper, fiber laser arc hybrid welding plasma was studied by using the multiple imaging method. Four images of plasma with different light intensity areas can be simultaneously observed in a picture. The arc plasma and metal plasma can be distinguished in the high light intensity area, and the arc plasma has an approximate average light intensity distribution. The metal plasma is mainly concentrated above the keyhole, and its temperature/electron density first increases and then decreases along the laser beam direction. The light intensity of plasma is approximately proportional to its temperature in the low light intensity area, and its morphology is similar to its temperature field profile obtained by numerical simulation. By using the multiple imaging method, the high light intensity area morphology of plasma can be measured, and the simulation results of the plasma temperature field in the low light intensity area can be verified.

title: Numerical Simulation of Temperature Field and Residual Stress in Laser Arc Hybrid Welding
abstract: A three dimensional FEM model was put forward for the laser TIG hybrid welding,the heat source model combined two heat sources was established in this paper,in which the model of laser welding was Gaussian volume heat source and the model of TIG arc was double ellipsoid volume heat source.Based on the model established,the temperature and residual stress distributions of TC4 alloy plate with thick 3 mm for the laser welding,the TIG welding and the laser TIG hybrid welding were calculated and compared.The results showed that the simulation results were well agreed with the experimental results,which proved that the heat transfer model was more close to physical reality.

title: Influence of laser arc hybrid welding conditions on cold cracking generation
abstract: For extending application of laser arc hybrid welding on manufacture and fabrication of large steel structures such as bridges and ships, proper welding conditions should be identified. In order to mechanically evaluate welding cold cracking by laser arc hybrid welding, a series of experiments and numerical simulation was carried out. A numerical simulation model by finite element analysis for laser arc hybrid welding was proposed. The validity of the simulation model was verified by comparing the analytical results with the experimental results. It was confirmed that the restraint strain proposed as a measure for cold cracking in arc welding could be applied on the laser arc hybrid welding. Based on the evaluation measure, the influence of laser arc hybrid welding conditions on the cold crack occurrence was investigated.