Welding Temperature Field Research Articles

Finite element analysis and experimental study on laser welding temperature field of dissimilar metal materials

Aiming at saving defects and cracks of dissimilar metal materials laser welding, the finite element analysis of temperature field and new welding process of stainless steel/Al, stainless steel/Cuwere developed in this work.Taking stainless steel/Al, stainless steel/Cu dissimilar materials laser welding for example, the physical model was established, and the finite element simulation of three-dimensional temperature field of laser welding was carried out based on Abaqus CAE. The results show that the simulation of temperature field provides reference for experimental process parameters, fiber laser welding is applicable to stainless steel/Cu, stainless steel/Al with lower laser welding defect.The process parameters were optimizedto achieve better welding quality and solve welding defects.The accurate prediction of temperature field distribution in dissimilar materials laser welding is great significance for practical process guidance.

Numerical simulation of residual stresses in aluminum alloy welded joints

The lightweight design makes thin-plate welded structures used widely, especially for the aluminum alloy thin-plate welded structure, it is very important to study the fatigue fracture properties of the structure considering the influence of residual stress. A solid model of a butt joint of aluminum alloy with a double-pass weld is established. Both the welding temperature fields and residual stress fields are simulated through the thermal elastic–plastic method. The welding experiment is also performed with the corresponding joint, which is welded by means of metal inert-gas (MIG) welding. Consequently, the computational and experimental results of residual stress are in good agreement. Moreover, the thermal elastic–plastic method is employed to calculate the residual stress fields of typical welded joints. Based on the inherent strain theory, the transverse and longitudinal inherent strain of the joints are decomposed from the total strains and applied to both solid and shell models of the three types of joints to calculate the residual stress fields of them. The results of the solid and shell models using the two methods are practically consistent, which indicates that the inherent strain method can predict the residual stress on the shell model efficiently and accurately. Thus, the method of predicting the welding residual stress of thin-plate structures based on the inherent strain is proposed, which provides a reference for the structural fatigue assessment under the influence of residual stress.

The Numerical Simulation of Temperature Field in Friction Stir Welding of 7075 Aluminium Alloy

Considering friction heat generation between rotating tool and workpiece and plastic deformation heat generation of material, a numerical simulation model of friction stir welding of 7075 aluminium alloy sheet was established. In this study, the temperature field of the welding process was analysed, and the effects of different stirring speeds and welding speeds on the temperature field were compared. The results show that the high temperature region is located below the shoulder and diffuses outward in a ring shape. After the welding is completed, the workpiece center temperature is high and the ambient temperature is low. The stirring speed of the tool has a large effect on the peak temperature during the welding process. The effect of the welding speed on the peak temperature is less than the stirring speed. The comparison shows that the welding temperature is about 478°C at a stirring speed of 800r/min and a welding speed of 120mm/min, which is a suitable welding parameter.

Quantitative Correlation between Thermal Cycling and the Microstructures of X100 Pipeline Steel Laser-Welded Joints.

Due to the limitations of the energy density and penetration ability of arc welding technology for long-distance pipelines, the deterioration of the microstructures in the coarse-grained heat-affected zone (HAZ) in welded joints in large-diameter, thick-walled pipeline steel leads to insufficient strength and toughness in these joints, which strongly affect the service reliability and durability of oil and gas pipelines. Therefore, high-energy-beam welding is introduced for pipeline steel welding to reduce pipeline construction costs and improve the efficiency and safety of oil and gas transportation. In the present work, two pieces of X100 pipeline steel plates with thicknesses of 12.8 mm were welded by a high-power robot laser-welding platform. The quantitative correlation between thermal cycling and the microstructure of the welded joint was studied using numerical simulation of the welding temperature field, optical microscopy (OM), and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The results show that the heat-source model of a Gaussian-distributed rotating body and the austenitization degree parameters are highly accurate in simulating the welding temperature field and characterizing the austenitization degree. The effects of austenitization are more significant than those of the cooling rate on the final microstructures of the laser-welded joint. The microstructure of the X100 pipeline steel in the HAZ is mainly composed of acicular ferrite (AF), granular bainite (GB), and bainitic ferrite (BF). However, small amounts of lath martensite (LM), upper bainite (UB), and the bulk microstructure are found in the columnar zone of the weld. The aim of this paper is to provide scientific guidance and a reference for the simulation of the temperature field during high-energy-beam laser welding and to study and formulate the laser-welding process for X100 pipeline steel.

Experimental and numerical study of temperature field and molten pool dimensions in dissimilar thickness laser welding of Ti6Al4V alloy

Laser study is an important consideration in the present century with advances in laser technology. Titanium alloys are of great importance to the defense industry, aerospace and other industries due to its properties, including strength to weight. In this research, experimental and numerical study are investigated for laser welding on sheets of Ti6Al4V alloy with different thicknesses. Analysis of the temperature distribution around the molten pool and dimensions of the depth and width of the molten pool are performed by changing the parameters of laser such as focal length, speed of laser welding and power. The results show that the heat affected zone (HAZ) and molten pool is diverted to the thinner sheet. Also, by decreasing the focal length, the temperature of the workpiece and the dimensions of depth and width of the molten pool are increased. In addition, with enhancing the laser speed, the laser beam contact time with the workpiece surface reduces and the temperature decreases, resulting in a decrease in the dimensions of the depth and width of the molten pool. Eventually, as the power increases, the dimension of the melt pool increase and at both 180 W and 240 W powers, the thinner sheet experiences higher temperatures compared to the thicker sheet. In this study, the results of numerical simulation are matched with the experimental results and can be applied to obtain the temperature and geometry of the melt pool in other cases to reduce the cost and time.

Influence of arc interactions on heat and mass transfer during a two-arc hybrid welding

The quantitative analysis of the heat and mass transfer in weld pool is of great significance for the optimization of welding parameters in manufacturing process with a high-quality weld bead. In this study, the arc deflections caused by the electromagnetic force of two-arc hybrid welding was calculated. The heat source and arc force models of the hybrid welding were proposed considering the influence of the arc deflection and surface deformation of weld pool. Compared with single heat welding, the distributions of the arc heat energy, arc pressure, and arc shear stress in two-arc hybrid welding were studied based on three-dimensional transient computational models. The temperature field and the fluid flow on the upper surface and the longitudinal and cross -sections of the weld pool were analyzed to reveal the heat and mass transfer in workpiece. Experiments were carried out and the results showed that the simulated cross-section weld bead, thermal cycle, temperature field, and flow field agreed well with the experimental values.

A Study of the Effect of Post-Heating Pulse on Hot Cracking Susceptibility in Pulsed Laser Welding of Invar Alloy

Hot cracking is one of the major challenges in laser welding of Invar alloy. In this study, welding hot cracking susceptibility experiments are conducted with fish-bone-type Invar alloy sheets under pulsed laser welding condition. The pulse wave consists of two distinct power levels: welding pulse and post-heating pulse. The welding temperature field can be controlled by changing the duration of the post-heating pulse. The results of experimental measurements and finite element method calculation show that increasing of the post-heating pulse duration leads to a decline in the cooling rate of weld metal within the brittle temperature range, although the welding hot cracking susceptibility decreases at first and then increases. Neither the heat input nor the cooling rate is the only decisive factor for hot cracking during the welding process. 1. Introduction Invar alloy is widely applied in precision measurement devices and low-temperature-resistant structures for its low linear expansion coefficient at ambient temperature, which is less than 1.6 × 10—6 k—1, about 1/10 of the low carbon steel, and it changes very little within a large temperature range (Corbacho et al. 1998; Park et al. 2011; Zhao et al. 2015; Qiu et al. 2016). With the increase in demand for natural gas, the liquefied natural gas (LNG) carrier has been developed rapidly as a means of long-distance transport. The material of primary and secondary barriers on the containment insulation system of membrane-type LNG carrier is welded Invar alloy with a thickness of .7 mm, which directly contacts the — 163°C LNG (American Bureau of Shipping 2006; Bureau Veritas 2011; Wang et al. 2006). The total weld length of Invar alloy on an LNG carrier over 13 million cubic meters can reach up to 100 km according to statistics. Hot cracking is the major problem in the welding of Invar alloy, and currently Tungsten inert gas (TIG) arc welding is commonly used. However, the problem of hot cracking cannot be solved completely, and requires that the operator have good technical knowledge. Invar alloy has high hot cracking susceptibility during the welding process because of its single-phase austenite structure and high content of Ni (Kou 2003). Studies show that the welding hot cracking susceptibility of Invar alloy can be reduced when elements such as Ti, Mn, and Mo are added (Hirata et al. 2001), but these alloying elements will increase the linear expansion coefficient of the weld, resulting in the deterioration of mechanical properties at low temperature. Thus, laser welding and friction stir welding are proposed by researchers to solve the welding hot cracking problem of Invar alloy from the aspect of reducing welding heat input.

Practical Research on Welding Simulation of Q345 Steel

In this paper, we use TCL/TK integrated language analysis software and semi-ellipsoid heat source model and life-death element method to simulate the butt welding process of Q345 steel plate with thickness of 10 mm. We simulated and analyzed the temperature field, stress field and welding deformation of multi-layer welding. Through welding simulation analysis, we extracted the distribution of welding residual stress and welding deformation of butt joint, and obtained the transverse and longitudinal shrinkage of butt plate and the main reasons. The results show that the multi-layer butt welding seam and its adjacent area are under tension, and the numerical value generally reaches the yield strength, and the two sides are under compression. The tensile stress in the middle of the weld bead is the largest and decreases gradually toward both ends. The cross-sectional area of single-sided multi-layer welding seam is larger and asymmetric along the thickness of the plate. After welding, the transverse shrinkage and angular deformation of the welded parts are larger. At the same time, the accuracy of the simulation results is verified by actual welding and testing.

Welding Temperature Distribution and Residual Stresses in Thick Welded Plates of SA738Gr.B Through Experimental Measurements and Finite Element Analysis.

A numerical and experimental study of welding temperature distribution and residual stresses in thick welded plates of SA738Gr.B was conducted. Within the framework of numerical investigations, the temperature field of SA738 thick plate welding was simulated and analysed by using 2-D modelling technology. The temperature field was checked by using the thermal cycle curve with the aim of increasing the computational accuracy and efficiency, and the temperature field was verified by using the thermal cycle curve and heat affected zone. The welding stress field was analysed based on the temperature field, and the indentation test method was used to verify the stress field, and the error was controlled to within 12.5%. With the help of a welding model established for SA738Gr.B thick-plate welding the sequence was simulated. Seen from welding sequence 1 to welding sequence 3, transverse stress S11 changed significantly, decreasing by 14% and 17% respectively, adjusting the welding sequence can reduce welding residual stresses.

Formation of welding burrs on deep-sea oil pipe based on electromagnetic heating

High-frequency resistance welding relates to electromagnetic-thermal coupling, causing the formation of welding burrs under the action of an extrusion force, and the morphology of the welding burrs is influenced by the welding temperature field. The welding burr model of solid-liquid two-phase deformation in a high-frequency electromagnetic heating process established in this paper discloses how the temperature and velocity fields vary in the welded zone under the action of an extrusion force and the mechanism of action of temperature on burr morphology. This is the core basis for establishing artificial intelligence (AI) for burr morphology based on machine vision. With the increase in extruded length, the high-temperature zone gathers toward the internal and external welding burrs. At the weld seam, the resultant velocity is relatively high on both internal and external surfaces and is lowest in the middle. On this basis, the influences of different process parameters on burr morphology and the welding quality are analyzed. As the welding temperature rises, the ratio of weld reinforcement to burr width decreases gradually. The correlations between the process parameters for electromagnetic heating and burr morphology are disclosed quantitatively by expounding the extrusion welding process for welded pipes under electromagnetic heating for the purpose of exploring the welding quality characterized by burr morphology under different process parameters and to promote the development of AI for electromagnetic extrusion processes.

Analysis of the Temperature Field in Al-Cu Dissimilar Materials Friction Stir Welding

Friction stir welding (FSW) as a solid-state joining method has been applied to the Al-Cu dissimilar joint. However, most research has focused on the technical study of FSW and little attention has been paid to the investigation of the heat source. This paper aims to develop a numerical thermomechanical model for Al-Cu dissimilar FSW process. The model results show that the calculated temperature values are closely correlated with the experimental temperature value, ensuring the accuracy of the model. Furthermore, the model is used to analyze the characteristics of the dissimilar FSW temperature field. It is observed that the temperature field was asymmetrical, which was caused by the different properties of the materials and the different heat inputs in the welding process. Moreover, the variation in the temperature field decreases with the increase in the offset.

Residual stress and welding distortion of Al/steel butt joint by arc-assisted laser welding-brazing

Abstract The thermo-elastic-plastic finite element method (FEM) is used to simulate the thermo-mechanical behavior of Al/steel tungsten inert gas (TIG) arc-assisted laser welding-brazing (A-LWB) butt joint. The influence of material nonlinearity, geometrical nonlinearity and work hardening on the welding process is studied, and the differences in the welding temperature field, residual stress and welding distortion by A-LWB and by single laser welding-brazing (SLWB) are analyzed. The results show that the thermal cycle, residual stress distribution and welding distortion by the numerical simulation are in good agreement with the measured data by experiments, which verifies the effectiveness of FEM. Compared with the SLWB, A-LWB can make the high-temperature distribution zone of weld in width direction wider, decrease the transverse tensile stress in the weld and reduce the distribution range of longitudinal tensile stress. And the welding deformation also decreases to some extent.

Research on Quality Control of Arc Welding Robot Based on Molten Pool Contour extraction

In order to overcome the influence of various uncertainties on the welding quality in robot welding process, this paper proposes a multi-information fusion detection method. At first, in order to obtain the geometrical characteristics of the molten pool image, the adaptive Wiener filtering algorithm was used to denoise the image, and the Otsu threshold method was used to binarize the image. Then the binarized image was co rroded, swelled, removed and small area operation. The complete clear edge information of the weld pool is extracted; then the simple and effective geometric feature parameters are used to describe the shape of the weld pool. According to the characteristics of the arc welding temperature field, the method of radiation temperature measurement and the wavelength selection principle are discussed. From the arc temperature, wavelength and the angle of the thermometer with respect to the molten pool area, the interference of the arc at the temperature measurement point in the near-melting pool area was analyzed; It is proved quantitatively that the radiation temperature measurement method is feasible under the condition of small arc current.

Numerical simulation of temperature field of B1500HS steel/Q235 laser tailored blanks by external thermal action

Taking high-strength B1500HS steel/Q235 laser tailored blanks as the research object, this paper established the finite element model of the laser welding process of high-strength B1500HS steel /Q235 laser tailored blanks based on the theoretical model of laser welding temperature field. The temperature field of laser tailored blanks was numerically simulated under the conventional condition and External Thermal Action (ETA). The thermal cycle curve of welded joints was compared and analyzed, and the influence of welding power and welding speed on the welding width was analyzed. The results show that, under ETA condition, the cooling rate of weld and heat affected zone decreases greatly, and the residence time above the phase transition temperature becomes longer. And it is conducive to the homogenization of austenite structure at high temperature and the coordination of mechanical properties of welded joints. In addition, under the same welding power, the welding width of ETA is wider than that of conventional welding, and the larger the welding speed is, the smaller the welding width is. In order to ensure the penetration of welding, the welding speed should between 2mm/s and 7mm/s.

Welding residual stress and distortion in ZS100 motorcycle rear fork welded joints

Finite element (FE) method was utilized to analyze the welding temperature field, stress and distortion in a ZS100 motorcycle rear fork. The FE models were simplified due to symmetry of the structure. Simulation results show that temperature distributions, residual stress variation and distortion in the structure are complex and related to welding current. Magnitudes of residual stress occur in HAZ and weld metal for components of side tube-connecting tube and side tube-axle tube. Increasing welding current can result in higher residual stress level and post-welding distortion. Therefore, relative small welding current is preferred for the sake of reduce welding stress and distortion.

Simulation of Temperature Distribution and Microstructure Evolution in the Molten Pool of GTAW Ti-6Al-4V Alloy.

In this paper, a three-dimensional (3D) finite element model was established by ABAQUS software to simulate the welding temperature field of a Ti-6Al-4V alloy under different welding currents based on a Gaussian heat source model. The model uses thermo-mechanical coupling analysis and takes into account the effects of convection and radiation on all weld surfaces. The microstructure evolution of the molten pool was calculated using the macro-micro coupling cellular automaton-finite different (CA-FD) method. It was found that with the increase of the welding current, the temperature in the central region of the moving heat source was improved and the weld bead became wider. Then, the dendritic morphology and solute concentration of the columnar to equiaxed transition (CET) in the weld molten pool was investigated. It is shown that fine equiaxed crystals formed around the columnar crystals tips during solidification. The coarse columnar crystals are produced with priority in the molten pool and their growth direction is in line with the direction of the negative temperature gradient. The effectiveness of the model was verified by gas tungsten arc welding experiments.

Numerical simulation optimization for laser welding parameter of 5A90 Al-Li alloy and its experiment verification

Weight reduction is very important to aircraft. Laser welding technology is beneficial to reduce the weight of aircraft structure. However, due to the unclear laser welding properties of Al-Li alloy, the research on laser welding of Al-Li alloy is necessary. In current study, the temperature field, stress field and deformation of laser welding are simulated. The optimal welding parameters are obtained by simulation, which are used to weld the real Al-Li alloy sheet. Besides, the microstructure and mechanical property of welded joints are analyzed. It is found that the simulated optimal welding parameters are suitable for welding real Al-Li alloy sheet. And the simulation results are consistent with the experimental results.

Coupling Computation between Weld Mechanics and Arc Plasma Process for Residual Stress Analysis

Abstract This article presents an advanced computational framework to accurately simulate weld residual stress, which is generated as a result of thermomechanical behavior during welding. The basis of the framework is coupled process–mechanics modeling and analysis of gas tungsten arc welding (GTAW). In the developed modeling and analysis, a heat source model dependent on the welding heat input condition was constructed by considering the physics of the welding arc. Formation of the weld pool and temperature field was calculated through a combined conductive and convective heat transfer analysis with the constructed heat source model. Transient temperature fields obtained were used for large-deformation thermal elastic–plastic analysis of residual stress induced by welding. The modeling and analysis were applied to calculate the welding thermomechanical problems of low-carbon austenitic stainless steel. The calculated weld penetration, temperature profiles, and distribution of residual stress in the welds were compared with the experimental measurements to validate the accuracy of the modeling and analysis. The effect of convective heat transfer on weld pool formation was further investigated in relation to a parameter derived from welding thermal conduction theory for a moving point heat source. The dimensions of weld penetration and the convective heat transfer effect were estimated by the parameter. Thus, it was concluded that the developed modeling and analysis techniques successfully achieved an accurate weld residual stress analysis and provided a more detailed understanding of the convective heat transfer effect on weld pool formation.

Temperature Field and Residual Stress of Butt Welding for IN182 Plate

The welding process is a nonlinear phenomenon in nature which leads to deformation and residual stresses in weldments. To overcome the structural changes in the weldments the computational packages can be effectively used for analyzing the changes in its life. Inconel superalloys have excellent mechanical properties and are used in the industrial applications. The present simulation is carried out for single pass butt-joint. Simulation studies are used for effective selection of process parameters for improving mechanical properties in the weld structures. In this work, coupled thermo-mechanical simulation process was carried out for predicting the temperatures, distortion and residual stress distribution in the weldments using Finite element analysis at the transverse direction on the welded surface.

Effects of heat source geometric parameters and arc efficiency on welding temperature field, residual stress, and distortion in thin-plate full-penetration welds

The Goldak’s double-ellipsoid volumetric heat source model is commonly used for arc welding in numerical simulation. Usually, heat source geometric parameters and arc efficiency need to be calibrated in thermal analysis until a good agreement with experiments is achieved. However, the influence of individual heat source geometric parameters and arc efficiency on welding temperature field, residual stress, and distortion is still unclear. In this study, this influence has been systematically investigated in a thin-plate full-penetration weld by methods of both numerical simulation and experimental method. The predicted and measured results indicate that the location of HAZ boundary and the Δt8/5 time can only be influenced by arc efficiency (significantly) and heat source width (slightly) in thin-plate full-penetration welds. Furthermore, the variation of arc efficiency can significantly affect welding residual stress and distortion, while the reasonable change of heat source geometric parameters has a slight effect. In this study, a calibration procedure of heat input model in FE simulation of thin-plate full-penetration welds is provided.