Welding Deformation Research Articles

Flame correction analysis of tunnel boring machine shield body roundness

Tunneling boring machine is a kind of special construction machinery suitable for underground excavation, mainly composed of cutter head, shield body, screw conveyor, supporting system and so on, mostly used in modern infrastructure construction. Shield body is the key accessory of tunnel boring machine which plays an important role in excavation. Its roundness affects the progress and smoothness of construction directly, so it is of great significance to analyze roundness correction technology. Due to the large self-weight of shield body and influence of irregular welding deformation, it is difficult to make roundness under control in ideal state through existing manufacturing process. The out-of-tolerance part should be corrected after welding. Flame correction is a convenient technology to correct welding deformation which apply to roundness correction of shield body. This paper mainly expound and analyze shield body compositions, difficulties of roundness control and key technical points of flame correction.

Reductions in the Laser Welding Deformation of STS304 Cylindrical Structure Using the Pre-Stress Method

Welding deformation occurs due to non-uniform thermal expansion, thermal contraction, restraint, and phase transformation in a metal by a local welding heat source. This causes problems such as low buckling strength and the reduced workability of the production process. Correcting welding deformations in stainless steel using heat—such as by linear heating—causes metal sensitization, which should be avoided. Herein, welding deformation was reduced by applying tension stress instead of correcting the deformation by heating. A deformation-prevention jig was used to reduce welding deformation during the manufacturing of a cylinder made of STS304 by laser welding. The tensile stress was induced by pushing the cylinder shell outward using the deformation-prevention jig. A thermo-elastoplastic analysis was performed to investigate the effects of the magnitude of the tensile stress on welding deformation. Furthermore, the parametric results—which indicated a reduction in welding deformation—were verified through experiments. The thermo-elastoplastic analysis suggested that deformation did not occur when the magnitude of tensile stress was approximately 50% of the yield stress of the base metal. Moreover, the deformation was experimentally reduced by 11–20% when a tensile stress of 30 MPa was applied to the cylinder, compared with that in the absence of tensile stress.

Research on welding deformation of hollow thin-walled complex structural parts based on plane bending theory of constant section beam

In order to effectively forecast the welding deformation and deformation pattern of hollow thin-walled aluminum alloy complicated structural parts, based on the plane deformation theory of constant section beam and workpiece constraint conditions, the complex feature structure was split and the deflection curve equation of each position was constructed. Moreover, the inherent strain method was used to solve the welding equivalent load, and the welding deformation was calculated by combining the equivalent load with the deflection curve equation. On the basis of the theoretical load value, the welding deformation at different positions during and after welding was numerically simulated by finite element simulation. What's more, the theoretical deformation of each plate is verified by the simulated deformation results. Besides, the simulation deformation results of post welding deformation are verified by welding experiment. The results show that the shrinkage deformation of the welding position is the largest, the transverse and longitudinal deformation are 0.007 mm and 0.018 mm respectively, the error rates of theory and simulation are 5.2 % and 5.5 % respectively. What's more, the welding deformation at the non-welding position is mainly reflected in the vertical direction of the upper skin plate. After the external constraints are released, the actual maximal deformation values of the two sides of the upper skin plate are 0.08 mm and 0.064 mm respectively. The deformation presents an M-shaped distribution, which is comparable to the deformation distributions of theory and simulation. The deformation value caused by the welding process accounts for 10 % of the total deformation after the removal of external constraints. In addition, the welding process is the main stage of forming the deformation distributions at each position, and the release of external constraints is the main factor leading to the final deformation.

Study on influence of gas cutting on welding deformation after submerged arc welding at removing constraint jig plates

In order to investigate the effect of gas cutting during removal of constraint jig plates on deformation after submerged arc welding, the authors have conducted the experiments on a series of processes using a constraint jig plates in a test specimen modeling the deck of a steel bridge. In this paper, an Idealized explicit FEM developed by the authors is applied to investigate in detail the factors that cause springback deformation during the gas cutting of the constraint jig plates. A series of welding and cutting processes using a constraint jig plates were modeled, and then a three-dimensional thermo-elastic-plastic analysis was performed using the Idealized explicit FEM. As a result, it is confirmed that the experimental and analytical results were in good agreement, and the validity of the analysis method was demonstrated. In addition, it is found that the inherent deformation during gas cutting had a significant influence on the springback deformation by the numerical analysis. Then, we proposed a simplified mechanical model to estimate the deformation during gas cutting. As a result, it was found that the proposed mechanical model showed quantitatively good agreement with the springback deformation.

Numerical and Physical Simulation of MAG Welding of Large S235JRC+N Steel Industrial Furnace Wall Panel

This paper presents the results of a study on the development of a Metal active gas (MAG) welding technology for an industrial furnace component made of steel S235JRC+N with respect to the minimizationof welding deformation. A numerical simulation of the welding process was performed in the first phase of the research. The numerical simulation was carried out with the SYSWELD software. For the numerical simulation of the welding process, the FEM method was used. In the simulation, four variants of restraint of the industrial furnace wall panel elements during the execution of the welding process were investigated. They differed in the number of restraints (model 1-4). It was found that the difference between the maximum mean strain in model 1 and the lowest mean strain in model 4 was only 11%. A physical simulation of the welding process was then performed with a restraint variant according to model 1. The displacement results obtained from the physical simulation of the welding process were compared with the displacement results from the numerical simulation. Discrepancies between numerical and physical simulation displacement values were found. The quality of selected welded joints was also evaluated. Visual testing (VT) and measurements of weld geometries were performed for this purpose. Metallographic tests and hardness measurements were performed to determine of influence of the welding process on the microstructure of the welded joint area, especially the heat affected zone (HAZ). The results obtained confirm the correctness of the assumptions made regarding the technology of manufacturing the furnace wall panels.

Laser welding simulation of large-scale assembly module of stainless steel side-wall

Due to the advantageous characteristics of laser welding technology, it is being increasingly used for constructing stainless steel rail vehicles. It can improve the appearance of a vehicle, enable designs with a relatively high degree of flatness, and ensure higher-quality connections between different parts of a vehicle. Moreover, it can improve the strength and stiffness of the components of the vehicle. In this study, a large-scale assembly module of a stainless steel side-wall was considered as the research object. The combined heat source model of a Gaussian heat source and a cylindrical volume heat source was used to obtain the heat source parameters of laser welding to match the experimental data. Based on the thermal cycle curve method (TCCM), the influence of the number of weld segments and mesh divisions of the local model on the efficiency and accuracy of laser welding simulations was investigated. Thereafter, the research results were applied to the welding simulation of the whole side-wall module. The shape of the molten pool obtained using the combined heat source was closer to that of the experiments (error < 10%), demonstrating the accuracy and effectiveness of the developed the heat source model for laser welding simulation. For local model laser welding using the TCCM, a coarse mesh was used, and the weld was divided into four segments, and highly accurate results were obtained. This calculation time was only 5.97% of that of a moving heat source in case of the thermo-elastic-plastic method (TEPM). Residual stress and welding deformation of the stainless steel side-wall module were calculated according to actual process parameters and the results of local model simulation. Residual stress was discontinuously distributed at the weld segments, and it only slightly influenced the overall stress distribution. The maximum residual stress (462.15 MPa) occurred at the weld of the large crossbeam. Welding eight small and two large crossbeams influenced the deformation change and the maximum deformation (1.26 mm) appeared in the middle position of the left side-wall. The findings of this study show that the TCCM has high calculation accuracy and is sufficiently economical for predicting laser welding of large structures.

Orbital friction welding of steel bars – heat generation and process modelling

Welding of rails in the field is usually associated with a large heat input, which results in a large heat-affected zone (HAZ), which in turn may impair the welded rail head and decrease its service life. An innovative orbital friction welding (OFW) process with an intermediate eccentrically oscillating disk is proposed, and a demonstrator has been constructed. This enables welding of rails, which have a non-symmetric cross-sectional area and must be stationary during welding. The process is characterized by low heat input, creating a narrow HAZ, and low welding deformations. A thermo-mechanical finite element model is developed to determine suitable process parameters to create a narrow HAZ. A phenomenological model for heat generation during friction welding is developed for pearlitic rail steel with parameters calibrated from rotary friction welding experiments on pipes. The temperature dependence of the friction coefficient in the interface is established. Pilot tests with the demonstrator OFW machine on bars with a quadratic cross section showed that preheating will be required to guarantee a fully pearlitic weld zone. This was verified by the simulations of the thermo-mechanical finite element model.

The deformation analysis of friction stir welding with different clamping distances for large thin-walled joints

Clamping scheme may change the local stiffness and affect the welding deformation which is very important for the large thin-walled joints connected by friction stir welding with heavy load and heat production. In this paper, the welding experiments of large thin-walled joints were conducted and the numerical simulation model is established based on three-dimensional stress mapping method. The accuracy of the numerical model is verified and welding deformation with various clamping distances is discussed. The restraint intensity index is employed to describe the influence of clamping distance on the stiffness of welding seam and welding deformation. The mechanism of welding deformation with the effect of clamping distance is well revealed by the analysis of welding stress and restraint intensity.

Effect of Laser Peening on the Corrosion Properties of 304L Stainless Steel.

Dry canisters used in nuclear power plants can be subject to localized corrosion, including stress corrosion cracking. External and residual tensile stress can facilitate the occurrence of stress corrosion cracking. Residual stress can arise from welding and plastic deformation. Mitigation methods of residual stress depend upon the energy used and include laser peening, ultrasonic peening, ultrasonic nanocrystal surface modification, shot peening, or water jet peening. Among these, laser peening technology irradiates a continuous laser beam on the surface of metals and alloys at short intervals to add compressive residual stress as a shock wave is caused. This research studied the effect of laser peening with/without a thin aluminum layer on the corrosion properties of welded 304L stainless steel. The intergranular corrosion rate of the laser-peened specimen was a little faster than the rate of the non-peened specimen. However, laser peening enhanced the polarization properties of the cross-section of 304L stainless steel, while the properties of the surface were reduced by laser peening. This behavior was discussed on the basis of the microstructure and residual stress.

Residual stress and deformation in UHS quenched steel butt-welded joint

For the low-alloy ultra-high strength (UHS) quenched steels with a yield strength of 1500 MPa, the welded joints have two obvious characteristics, namely solid-state phase transformation (SSPT) in the heat-affected zone (HAZ) and softening effect in the subcritical heat-affected zone (SCHAZ). In the current study, a UHS single-pass butt-welded joint with filler wire of ER307Si was fabricated, and thermal cycles at specific points were measured by thermocouples. After welding, relevant measurements of residual stress, deformation, microstructure and hardness were carried out. In this paper, based on the experimental hardness on the cross-section of the joint, a novel softening model was proposed. Meanwhile, based on coding subroutines of ABAQUS software, an advanced computational approach considering the thermal-metallurgical-mechanical coupling behaviour including the strain hardening as well as the annealing effect in fusion zone, SSPT in HAZ, and softening in SCHAZ was developed to implement thermal, metallurgical and mechanical analyses of the UHS quenched steel butt-welded joint. Comparing numerical and experimental results of temperature field, residual stress distribution and welding deformation of the joint, the calculated results of welding residual stress, angular distortion and transverse shrinkage are in good agreement with the measured data when both SSPT and softening effect were considered in the finite element model. The computed results indicate that SSPT has a significant influence on both the magnitude and the distribution of longitudinal residual stress, but it has a small effect on transverse residual stress. Moreover, the softening effect dramatically decreases the peak value of longitudinal residual stress in the SCHAZ, while it has an insignificant influence on transverse residual stress. The simulation results suggest that SSPT has a small effect on both transverse shrinkage and angular distortion, while the softening effect has very limited influence on welding deformation.

Laser Additive Manufacturing of 316L Stainless Steel Thin-wall Ring Parts

The process parameters of laser additive manufacturing have an important influence on the forming quality of the produced items or parts. In the present work, a finite element model for simulating transient heat transfer in such processes has been implemented using the ANSYS software, and the temperature and stress distributions related to 316L stainless steel thin-walled ring parts have been simulated and analyzed. The effect of the laser power, scanning speed, and scanning mode on temperature distribution, molten pool structure, deformation, and stress field has been studied. The simulation results show that the peak temperature, weld pool size, deformation, and residual stress increase with an increase in laser power and a decrease in the scanning speed. The scanning mode has no obvious effect on temperature distribution, deformation, and residual stress. In addition, a forming experiment was carried out. The experimental results show that the samples prepared by laser power P = 800 W, V = 6 mm/s, and the normal scanning method display good quality, whereas the samples prepared under other parameters have obvious defects. The experimental findings are consistent with the simulation results.

Відновлення та зміцнення деталей і робочих органів сільськогосподарських машин, працюючих в абразивному середовищі

The working bodies of tillage agricultural machines (ploughshare, plow shelf, cultivator paw, harrow disc) work in conditions of abrasive operation, shock loads and the impact of external aggressive environment. Their repair is to restore the original size of parts and wear resistance of functional work surfaces. During the operation of tillage machines and units, the working surfaces are subjected to uneven wear, which reduces the life of parts and increases the cost of their replacement and restoration. The working bodies of tillage agricultural machines (ploughshare, plow shelf, cultivator paw, harrow disc) work in conditions of abrasive operation, shock loads and the impact of external aggressive environment. Their repair is to restore the original size of parts and wear resistance of functional work surfaces. During the operation of tillage machines and units, the working surfaces are subjected to uneven wear, which reduces the life of parts and increases the cost of their replacement and restoration. The current level of operation of agricultural machinery is characterized by increased speeds and high productivity, which, in turn, leads to increased wear of parts. accordingly, the reliability of the recovered ensure the restorative parts. Surfacing makes it possible to obtain layers of any thickness and chemical composition on the working surfaces of parts; apply a welded layer with different properties, ie high hardness and wear resistance. In this work we use point (point) hardening, which consists in micro-dripping of the hard alloy into the surface structure of parts that undergo intense abrasive wear. The geometry of the hardening point is a spherical sector, which facilitates the rapid removal of heat from the surfacing bath in the base metal and the environment, so the hardening points harden at high speed and in a short time. At point strengthening of details one of the main conditions providing stable quality of process - coordination of welding current and arc voltage. The sawtooth profile of the ploughshare blade (cultivator paws) is maintained throughout its service life. providing effective cutting even with the blades worked. We will fully consider the welding stress and deformation of the steel and tungsten carbide, to ensure the using performance of products. About tungsten carbide, we use the most advanced production equipment and the most reasonable production process during the material selection, burdening, pressing and sintering. We always fully consider the special requirements of different products on the strength, hardness, grain size of tungsten carbide.

Investigation of Applicability of Welding Deformation Prediction Simulation Model for Automotive Components

Investigation of Applicability of Welding Deformation Prediction Simulation Model for Automotive Components

Research on an SVM Prediction of Welding Deformation Rectification for High-Strength Steel Fillet-Welded Joints after Traveling Induction Heating

_ To effectively realize the welding deformation rectification of high-strength steel fillet-welded joints in hull construction, a traveling induction coil was used to research the rectification effect of the welding deformation, and the support vector machine (SVM) method was applied to study the ability to predict the rectification amount. Welding and induction heating experiments were carried out on the fillet-welded joints, and finite element models, which were used to expand the prediction sample library of the SVM model, were established according to the experimental process. Then, the induction current, frequency, moving rate of the induction coil, weld deformation amount, and sheet thickness were selected as the input characteristic parameters of the SVM model to predict the rectification results achieved by traveling induction heating. It can be concluded that the established finite element model can accurately simulate the continuous machining process of welding-induction heating in reality, the induction heating method can actively eliminate welding deformation, and the SVM algorithm based on the radial basis function can predict the rectification result of weld deformation with high precision. Introduction The welding process of fillet-welded joints is one of the most common basic construction process units in shipbuilding, and the welding deformation caused by thermal elastoplastic deformation directly threatens the structural strength of hull construction (Liang et al. 2015; Yi et al. 2020). Extensive results indicate that welding deformation and welding residual stress are the main causes of hull structure deformation and stress corrosion; therefore, how to effectively realize the welding deformation rectification of fillet-welded joints has become a research topic of interest (Zhou &amp; Wang 2019). At present, the flame heating method is the preferred method used to rectify a welding deformation; however, some disadvantages in the flame heating method, which include temperature control difficulties, poor automation, harsh construction environments, and ease of material property damage, can seriously affect the quality and strength of a hull structure (Kotani et al. 2016; Kalyankar &amp; Shah 2018). In contrast, electromagnetic induction heating technology, which has a high degree of controllability, environmental friendliness, high heating efficiency, and low dependence on worker experience, has attracted the attention of researchers (Barclay et al. 2013; Haglund &amp; Kristoffersen 2014).

Numerical Simulation of Temperature Field in Ultra-Narrow Arc Welding of Thick-Walled Steam Turbine Valve Body Material

The welding problems of large and thick plates are becoming more prominent as the application of large-scale and thick-plate metal structures grows. Due to the issue of excessive welding deformation between the 60mm thick steam turbine valve body and the pipe joint, a new process method is employed to connect. In this paper, the welding technology of flux strip confined arc ultra-narrow gap is proposed to carry out welding test on the ZG13Cr9Mo2Co1NiVNbNB cast steel test block of steam turbine valve body material with a thickness of 60 mm. The welding temperature field is measured by means of a K-type thermocouple and numerical simulation. The results show that the thermal cycle curve obtained by the homogeneous body heat source simulation is basically consistent with the thermal cycle curve measured during the experiment, and the simulation results of the molten pool morphology are also consistent with the actual macroscopic morphology of the weld.

Preventing Crack in an Aluminum Alloy Complex Structure during Welding Process Based on Numerical Simulation Technology

Aluminum alloy structures are widely used for weight reduction in aviation, shipbuilding, rail vehicles and automotive industries. Fusion welding technology is one of the most important joining methods for lightweight structure assembly due to its advantages such as flexibility in design, high production efficiency, and low cost. However, the local centralized heating during fusion welding inevitably produces residual stress and welding deformation. For actual engineering structures, if the product design is unreasonable or the external restraint is inappropriate, the transient stress or residual stress become a key factor resulting in cracking during the assembly process. In the current study, an effective computational approach was developed based on the MSC Marc software to simulate transient and residual stress fields for complex aluminum alloy structures during the welding process. In the developed computational approach, according to the location and arrangement of welding lines, an instantaneous heat source model was used to replace the traditional moving heat source model, and as a result significanlty improved the calculation efficiency to meet actual engineering needs. The welding stresses, including transient and residual stress, of an A6061 aluminum alloy complex structure were calculated by the developed numerical simulation technology. The simulation results indicated that the cracking was produced by excessive transient stress during welding process. Subsequently, the effect of external restraint intensity on welding stress at the key location was examined numerically. Based on the simulation results, measures to reduce welding stress and cracking risk were put forward based on adjusting the external restraint intensity.

Numerical simulation analysis of laser-arc hybrid welding of austenitic stainless steel

Laser-arc hybrid welding heat source has high energy density, and the temperature field is very uneven and unstable. It is impossible to systematically study the welding temperature field only through process tests. For this reason, the calculation of the thermal process of hybrid welding is of great significance to the systematic study of the temperature field of hybrid welding. In this paper, the laser-arc hybrid welding process of 8mm thick austenitic stainless steel was simulated by SYSWELD software. The results indicate that with the increase of laser energy, the melting time increases, and the peak temperature rises from 1,230°C to about 2,000°C; When the laser energy is 3.0 kW, the welding deformation reaches the minimum value of 0.68 mm, but the peak value of equivalent stress is high, which is 476.8193 MPa. When the arc voltage increases, the peak temperature rises from 1,650°C to 1,850°C, and the melting time increases. The arc voltage has little effect on the equivalent stress of the weld and has a clear impact on the welding deformation. When the voltage is 18 V, the maximum deformation reaches 2.191 mm.

Effect of welding conditions on the deformation of lithium battery pack of aluminum alloys

Lithium battery pack, made of aluminum alloys, consisted of hundreds of welding seams. Due to the complicate distribution of welding seam and low stiffness of aluminum alloys, large welding deformation was found in the lithium battery pack. This paper analyzed the effect of welding parameters and the welding sequences on the deformation of lithium battery pack, then proposed a method to reduce the welding deformation of lithium battery pack maintaining the welding quality of single weld seam of aluminum alloys. By the coupling optimization of welding sequences and welding parameters, the welding deformation of lithium battery pack decreased from 1.69 to 1.29 mm with the reducing rate of 23.7% and hundreds of welding seams contours met the requirements of manufacturing quality. These findings could pave the way to improve the manufacturing quality of lithium battery pack made of aluminum alloys.

Evaluation of the functional acceptability of the ITER vacuum vessel

The International Thermonuclear Experimental Reactor (ITER) vacuum vessel (VV) is one of the critical components of the ITER tokamak fusion reactor. The first sector of the ITER VV was delivered to ITER Organization in 2020, and it is ready to assemble into the tokamak system. After manufacturing the ITER VV, an evaluation should ensure that the components are designed and manufactured to meet the functional requirements, such as vacuum leak tightness and structural integrity. The factory acceptance test (FAT) is essential for confirming acceptance in engineering and manufacturing. This paper introduces the engineering process and technical method of the FAT, which is applied explicitly to the first-of-a-kind ITER VV. We establish a visual inspection, pre-pumping assessment, pressure test, helium (vacuum) leak test, and final dimensional inspection for the FAT. The visual inspection revealed no blockages in the cooling channels of the double walls. The pre-pumping assessment conducted to check the vacuum level and residual gas condition, concluded that the inside of the VV was flawless and thus met the leak test requirements of 1 × 10−8 Pa m3 s−1. We confirmed no leakage or deformation through the pressure test under reduced pressure. The helium leak test demonstrated engineering soundness with leak tightness of 6.08 × 10−9 Pa m3 s−1, which is more stringent than the allowable limit. Furthermore, three-dimensional metrology was utilized to determine the as-built dimensions of the manufactured sector. Due to unavoidable weld deformation and tight tolerances, the as-built result does not perfectly meet the assigned tolerance level. Nevertheless, it can be considered as advanced information for assembly with in-vessel components and other sectors. Based on the conformance and suitability of the suggested FAT for the first ITER VV sector, we will determine the acceptability of the upcoming VV sectors, which will be manufactured and delivered by Korea shortly.

Welding process optimization for the inner tank of the electric water heater by numerical simulation and experimental study

The inner tank is the core weldment of the electric water heater (EWH). During service, leakage often occurs at the welds of the inner tank due to stress concentration. Reducing the welding residual stress and deformation is crucial to improve its service life. In this paper, the welding process optimization of the inner tank was investigated by numerical simulation and experimental validation. The influence of the welding sequence and welding start location of the circumferential welds (C-Welds) on the welding residual stress and deformation have been fully analyzed. The results show that the welding sequence has little effect on decreasing the welding residual stress and deformation. The peak welding residual stress and deformation reach a minimum of 170.06 MPa and 0.897 mm when the welding start location of the C-Welds was adjusted from 180° to 270° clockwise from the longitudinal weld (L-Weld), a reduction of 15.17 % and 12.98 %, respectively. The welding start location of the C-Welds is the determining factor of welding residual stress and deformation. To verify the effectiveness of the proposed welding process, full-scale welding and pulse pressure experiments were carried out. The pulse number of the inner tank has reached over 100,000 times, which satisfies the requirements of welding quality of the enterprise. This article is valuable for guiding the service life improvement of the inner tank, which results in economic efficiency growth.