Welding Of Parts Research Articles

Random vibration fatigue life assessment and optimization of a train buffer beam considering welding residual stress

The traditional fatigue design of accessories attached to a train body does not consider welding residual stress for fatigue life prediction of welded structures during the design stage, thereby resulting in insufficient fatigue strength for local welded parts. The power spectral density of random excitation caused by rail irregularity from American six-level spectrums was obtained in this paper. Through welding thermal elastoplastic theory combined with ellipsoid heat source model, a numerical simulation for welding residual stress production and distribution of a train buffer beam was conducted. In accordance with the coupling stress component, the fatigue performance of a train buffer beam under random loads was evaluated by the AA6082 welded joint S-N curve, whose lifetime did not satisfy design requirements. Then, the surrogate model of a train buffer beam for anti-fatigue optimization design was constructed based on the response surface method. The fatigue life of the optimized train buffer beam increased by two orders with the use of the genetic algorithm to find the optimal solution in global variables.

Repeated Weld Repair and its Influence on Welded Carbon Steel

Weld repair usually comprises of mechanical removal of weld part and redisposition of the filler wire using the same parameters. The defect may be removed by carbon arc gauging and grinding or machining. The strength and the microstructure of the material will changed when the repeated weld repair is applied to the material at the same area. The purpose of this study is to compare and identify the angle of distortion, hardness, and tensile strength and bend strength and to analyze the macro and microstructure between repairing method using carbon arc gauging and mechanical grinding process with the same number of repairing sequence. The result proved that repairing A36 steel increased the strength of the material itself but the ductility was decrease when the number of repair increases. It can be concluded that, the repair using carbon arc gauging can’t be applied to repair weld joint for material because it’s more significant to change the material process compared to mechanical grinding. Overall, the mechanical grinding technique is the most suitable practice which can serve as the suitable method for repairing the weld defect if the repaired focus area received high impact loads.

Acoustic emission source localization method for high-speed train bogie

Bogie is one of the most critical parts of high-speed train and is directly related to the operation quality and safety of the train. However, currently no dynamic non-destructive testing method exists for real-time monitoring. Therefore, this paper proposes a new damage localization method for high-speed train bogie dynamic testing. The acoustic emission testing technology is applied to test the vulnerable welding parts of the bogie with time reversal localization method. Firstly, the bogie welding parts structure model based on finite element software is established. Then an acoustic emission damage signal is sent from the model and the acoustic emission source signal is received by the preset acoustic emission sensor. And the accurate localization of damage is achieved by dealing with the received signal according to the time reversal focusing principle and imaging the acoustic emission source. The simulation experiments show that the proposed method can accurately find the damaged localization. And finally, the method has been verified through experiment, and the results show it can effectively improve signal energy of the damage source, and the position of the damage source can be shown accurately through signal reconstruction and localization in the detection area.

A study on seam tracking in robotic GMA welding process

Abstract In recent years, an image processing and sensor technology for welding automation, intelligence and information with rapid development of welding automation have become an inevitable trend. Owing to the features of mass information, high reliability and applicability in weld inspection for robotic arc welding, the sensor-based weld seam detection has been widely applied and gradually become a hot topic. Furthermore, the robotic arc welding can use its own machine vision system to obtain workpiece positioning information, weld space position, bead geometry and weld seam tracking. The most important task in the machine vision system is how to process the collected visual information to accurately locate the center of the weld and achieve weld tracking. During the welding process, the images taken are often unclear and the features are not obvious due to the interference of arc, splash and smoke. Therefore, it is necessary to carefully design the image acquisition process and the image processing algorithm to complete the weld inspection. In this study, the robotic GMA(Gas Metal Arc) welding has been applied to bead-on-plate welding with vertical position. Thermal images of two different angles (0°, 30°) based on infrared camera through experiments might be obtained for developing an optimal image processing algorithm which was applied in seam tracking. In image processing procedure, the first step is image pre-processing including noise removal, contrast enhancement and binarization. The obtained image adopts multi-scale edge detection method, which can extract complex image edges well, then segment the image, accurately locate the weld part, perform image size measurement and centerline extraction, and finally convert the image information of the weld into the world calibration. The calculated data is then fed to a controller which controls the welding electrode movement. Use of machine vision system has eliminated the requirement to pre-feed the workpiece data for the robot to detect the dimension and position of the workpieces. The developed algorithm can detect weld image effectively, and extract the edge and the center line of the weld successfully

Experimental Study of Microstructures in Bias Weld of Coiled Tubing Steel Strip With Multi-Frequency Eddy Current Testing

Coiled tubing technology is widely used in drilling and repairing operations, and the quality of bias weld directly determines the fatigue life of the coiled tubing. The microstructures consistency between the bias weld and the base metal determines that whether the fatigue resistance of the weld reaches the level of the base metal. In this paper, multi-frequency eddy current testing technique is used to detect the reactance of the bias weld zone and the base material zone within coiled tubing steel strip, which can be used to determine the microstructure consistency between the base metal area and the weld area, and in turn to improve the welding technology and heat treatment process. In this work, CT100 and CT90 materials with the bias weld for coiled tubing were used as the test samples, and the on-line real-time non-destructive testing technology was used to judge whether welding technology and heat treatment technology have been improved. The basis for determination is whether the mechanical properties and fatigue properties of the welding site reach the base material level. The weld zone and base metal zone can be identified by analyzing the characteristic cloud map of the detection signal, and then the quality of partial weld can be evaluated according to the difference of microstructure between them, which is of guiding significance for quality control and improvement of coiled tubing production process.

Effect of Current Variation on Microstructure and Properties of B4C Nickel-base Alloy by Plasma Surfacing

In order to study the hardness of nickel-based alloys and the effect of different mass fraction boron Carbide on the microstructure of nickel-based alloys. In this paper, different amounts of boron carbide are added to the nickel alloy powder. A layer of nickel alloy surface layer is welded on the surface of the Q235 steel plate by plasma surfacing technology. The microstructure of the laminate is observed and analyzed by using Caisijinxiang tissue microscope. The hardness of the welding layer was tested by microhardness meter and the influence of boron Carbide on nickel alloy was obtained. The results show that boron carbide and nickel base alloy are well fused. The surfacing layer is mainly composed of fine dendrites and herbaceous eutectic structures. The addition of boron carbide can significantly improve the hardness andfine structure of the surfacing layer. With the increase of the content of boron carbide, the hardness of the surfacing layer first increases and then decreases. The experimental data show that when the mass fraction contentof boron carbide is 6% and the current is 110A, the hardness of the welding parts is higher.

Experimental Investigation of Vibration Stress Relief of A106 Steel Pipe T-Welded Fittings

This research examines the use of vibratory treatments to reduce residual stresses in small welded parts. In this experimental investigation, a post weld vibration treatment was applied to T- A106 steel pipe fitting specimens to study the effect of the treatment on the residual stress and the hardness of the material. The vibratory stress relief treatment was carried out at different vibration frequency. The results have demonstrated that post-weld vibratory stress relief of small size fittings is possible and residual stress may be relieved, and the treatment may be an alternative method for heat treatment especially when unchange in dimensions and material stability are required.

Weld bead temperature and residual stresses evaluations in multipass dissimilar INCONEL625 and SS316L by GTAW using IR thermography and x-ray diffraction techniques

Thick plates of SS to Inconel are used in nuclear reactors to withstand high temperatures and pressures. This study is to evaluate the GTAW joining of SS316L to Inconel625 to evaluate the weldability; the temperature distribution in the longitudinal and transverse directions, resulting in distortions and the induced residual stresses. To obtain real-time temperature images Infrared thermography measurements were made. Similar welding joints of SS to SS and Inconel to Inconel were used as a reference for comparison with the dissimilar welding parts in this evaluation. Compatible Filler rods were selected: SS316 filler rod was used for welding of SS316L samples and ERNiCrMo-3 was used when a part is IN625. This study reports the temperature distribution for a SS to Inconel weld process and the resulting distortion and residual stresses were within the acceptable limits.

High accuracy Numerical simulation on 3D weld-pool shape of large parts

The shape of weld pool and the distribution function of heat source are the premise and foundation of all welding simulations, but many assumptions are given to them which lead to different or even contradictory results. So the model of three-dimensional weld pool should be established without predetermining the shape of weld pool, the shape of free surface and the distribution of heat flux density, moreover it is combined with the thermal model. Through decoupling, the fluid velocity field, the temperature contour and the law of temperature distribution of the weld pool are obtained, the shape of molten pool is also gotten out which is like a revolving body of the pen holder, and the density function of heat flux distribution is fitted out. The internal relationship between simulation results and weld fusion line are presented. Welding experiments of large parts are carried out under the same process conditions. It shows the weld fusion line and the shape of the surface of the weld are in good agreement with the simulation results. This has great practical significance for unifying simulation results, guiding production and improving quality of large welding parts.

A CFD-FEM Model of Residual Stress for Electron Beam Welding Including the Weld Imperfection Effect

Residual stress of electron beam welding (EBW) is associated with the heat transfer, fluid flow, and keyhole dynamics occurred in the process. In engineering, it was commonly simulated by pure heat conduction-based thermomechanical modeling with an experimentally calibrated heat source model. This method, however, is difficult to be used to consider the effect of weld imperfections such as the spiking and porosity defect. In this study, we proposed a novel combined computational fluid dynamics and finite element method (CFD-FEM) model to predicate the residual stresses of EBW. This model allows us to include the integral effect of heat transfer, fluid flow, and keyhole dynamics as well as process defects on residual stresses for the first time. A phenomenological heat source model dependent on the dynamic keyhole was considered in the CFD model part. A mapping algorithm was developed to build a new heat source model of FEM modeling part from the CFD simulations. Parametrical simulations and experiments of EBW of a 10-mm-thickness Ti-6-Al-4-V alloy plate were carried out and good agreements were obtained by the comparisons. It was shown that for deep penetration EBW the keyhole oscillates in radial and depth directions and the spiking defect occurs, particularly under large heat input parameters. Interestingly, the equivalent and principle residual stresses exhibits strong oscillations in the bottom part of welds along the welding direction, in which the amplitudes are around 9 pct (73.69 MPa) of the equivalent stress and 24 pct (121.84 MPa) of the principle stress in penetration direction, respectively, when the power of electron beam is 1.5 kW. As the power of electron beam increases, the effect of spiking on the residual stress enhances. When the welding power increases to 2.25 kW, the amplitudes of equivalent residual stress increase to 12 pct (119.2 MPa). Our results provide a quantitative method connecting the weld pool dynamics and process defects with the residual stress of EBW, which previously could be understood only in a qualitative way, and demonstrate the possibility of residual stress predications only from the information of materials and process parameters before welding, without the knowledge of post-weld profiles.

Fatigue design of weld part in non-combustible magnesium alloy based on fracture mechanics

Fatigue design of weld part in non-combustible magnesium alloy has been studied. Specimens for fatigue test were produced by TIG welding with different welding conditions. According to result of fatigue strength tests, all weld specimens tested in the present study were broken at the weld prat, and a weld defect was found as a fatigue fracture origin. Fatigue life was well arranged by effective stress intensity factor calculated with a size of weld defect played as a fracture origin and applied stress. Therefore, it is speculated that fatigue strength of weld part is depending on a size of weld defect and threshold stress intensity factor at the weld part. Size of weld defect and value of threshold stress intensity factor possibly changed by welding condition. Therefore, relationship between heat input during welding process and threshold stress intensity factor was studied by conducting fatigue crack growth test at the weld part. The value of threshold stress intensity factor range increased with increase in heat input of welding process. However, values for threshold stress intensity factor range almost coincided when the crack growth curves were arranged by effective stress intensity factor range. Difference in threshold stress intensity factor range due to difference in heat input of welding process was mainly induced by change in crack closure effect. It is proposed that effect of crack closure depending on mechanical property of weld part should be taken into account on fatigue design of weld part in non-combustible magnesium alloy.

Modelling a Platform for Smart Manufacturing System

The characteristics of industry ecosystems in the 21st century that have evolved from advances in technology and connectivity in manufacturing include cyber-physical systems (CPSs), the Internet of Things (IoT), big data, and artificial intelligence (AI). These characteristics allow the manufacturer to monitor operation and control systems to improve performance through effective, efficient, and flexible production methods. Industry 4.0 continues to drive the manufacturing sector to use smart manufacturing systems to meet companies’ challenges. For example, a smart welding system can be created by integrating a robot welding part of a manufacturing operation with smart manufacturing, which enlists all the necessary manufacturing assets. Such a smart welding system can improve the uptime and performance of the operation and control systems. Here, the Reference Architectural Model Industry 4.0 (RAMI 4.0) is applied as a service-oriented architecture to demonstrate how to transform a robot welding system to meet the challenges of smart manufacturing in a structured way. This paper proposes using certain characteristics of I4.0 technologies for a smart welding system, based on a RAMI 4.0 conceptual approach, and designs a platform for a smart welding station.

An analytical solution for temperature distribution in fillet arc welding based on an adaptive function

This paper presents an analytical solution that can be applied to predict temperature distribution in fillet welds using adaptive function approach developed by authors. The adaptive function method is a general approach to solve the partial differential equation of engineering problem based on developing a flexible function of dimensionless parameters, which circumvent the simplification assumptions required in numerical and analytical solutions proposed so far. This paper intends to develop the adaptive function by manipulating Rosenthal’s equation so that it can be adjusted according to the experimental data, which are the weld pool dimensions and temperature measured at some arbitrary points. To apply the adaptive function in a fillet weld, a new coordinate system is defined in which the x-axis is parallel to the legs of the fillet weld (width direction of the weld plate), the y-axis is parallel to the welding trajectory, and the z-axis is parallel to the penetration of the weld (depth direction of the weld plate). A polar coordinate system is defined for the corner part of the fillet weld. The adaptive function in this part is defined to preserve the consistency of the isotherms. The experimental data were provided by performing GTAW on a stainless steel 316L with various welding current. The results indicate that the novel approach is fast and simple and agrees well with results from experiments.

The Influence of Shielding Gas on Strength of the Laser Welded Thin Sheet Lap Welds

The laser welding is usable method for joining thin plates with low energy input and precise penetration control. When joining of very thin sheets such as 0.5 mm the shape of the weld must be complete in order to achieve a good strength of the joint. The part of the test welds were welded without shielding gas and other part of the test welds by using 65 mm shielding gas nozzle behind the key hole. The strength of the laser weld of 0.5 mm Austenitic stainless steel (ASS) plate was measured in welds without shielding gas and Ar shielded weld. The strength of the shielded weld joints was significantly better than the joint weld without shielding gas due to convex shielded welds. In addition the shielded welds were bright which improves the corrosion properties of the joint.

Recognition and identification the position and location of tooth saw butt joint shape

This research presents a new approach vision-based to recognize and locate the tooth saw joint position in butt welding joint. The research came out because some joints are quite difficult to recognize the butt welding position and location especially in a corner side or which one belongs to the tooth saw shapes. Thus, the main objective of this paper is to synthesize a novel approach that is related to weld joint identification and detection, and then develop a new approach based on contour regions for recognition and identification of butt welding joint in robot welding. The methodology involved in identification and detection approach was implemented in two stages: (1) pre-processing and (2) segmentation. The butt welding joint for recognizing position from the starting, auxiliary 1, auxiliary 2, and ending of the joint shape was obtained from contour and region points. The recognized process was done in two stages: (1) a new approach based on the shape of weld joints and (2) weld joint representation in three approaches which are (1) middle point of each end of two lines, (2) maximum or minimum row of the lines depending on auxiliary points, and (3) intersection point between the two lines. The findings of the approach show that the largest image-matching error happened in approach (3); however, this approach has a smaller matching error compared to the actual position. The expected output is that a weld joint can allocate the position from the start, auxiliary 1 and auxiliary 2, and end points in x-y coordinates to instruct the welding robot to weld. This research will significantly increase the welding process of mass production from low to medium volume manufacturing either repair or maintenance work should be faster than welding parts manually.

Effect of TIG-Welding on the Structure and Mechanical Properties of the Pseudo-β Titanium Alloy VT19 Welded Joints

Analysis of the TIG-welding impact on the structure and mechanical properties of pseudo-β titanium alloy VT19 welded joints, obtained with different welding speed, different filler wire amount in welded joint, with and without flux layer. Microstructure of obtained welded joints were investigated. Using welded joints microsections approximate amount of β-phase in different parts of welds have been obtained. Mechanical properties of the obtained welded joints were analyzed and dependency of tensile strength and amount of β-phase were build.

Microstructure and Properties of Welded Joint of 6063 Aluminum Alloy Medium and Thick Plate

In this paper, the welding parts of the 6063 aluminum alloy 15mm and 20mm plate on the solar wing expansion frame of a certain type of satellite are studied. The structure of the welding structure is analyzed and tested. The relationship between the distribution characteristics of the joint and the mechanical properties of the weld and the influence law of the weld are analyzed, and the welding process is rationally formulated in the actual production. Provide theoretical basis and technical support for improving welding quality. The two thickness aluminum plates are formed by MIG welding. The metallographic samples and tensile specimens are intercepted from the welded parts, and the metallographic samples are prepared. The microstructure and tensile strength and hardness of the welded joints are analyzed by metallographic microscope, scanning electron microscope, X ray diffractometer, tensile test machine and microhardness tester. Degree. The results show that there is a softening zone in the welded joint, which mainly exists in the heat affected zone; at the same time, there will be a high hardness point (15mm 84.6HV; 20mm 70HV) in the fusion zone, which is due to the presence of more strengthening phase Mg2Si and a small amount of Al12Mg17. The average tensile strength of the welded joint with two thickness is 166MPa and 218MPa respectively, and the thickness of 15mm is lower than the tensile strength of 6063 aluminum alloy, while the 20mm thickness is higher than the theoretical tensile strength of 6063 aluminum alloy, and the elongation is higher than that of the 6063 aluminum alloy theory, in which the joint of 15mm thick welded joint is pulled from the 15mm at the weld seam. Extension fracture, 20mm thick welded joint tensile fracture at the weld.

Research of Urban Rail Transit Vehicle Aluminum Alloy Bolster FSW Welding Technology Based on Thermal-Mechanical Coupling

With the rapid development of urban rail transit and the increasing level of research and development, aluminum alloy materials feature excellent physical and mechanical properties, and thus an urban rail transit vehicle adopts aluminum alloy materials. Friction Stir Welding (FSW) technology is adopted in the production process of a bolster in this article and research of stress strain of friction stir welding parts plays an important role for engineering application of friction stir welding technology.

Investigation on the Effect of Initial Welding Imperfection on Fatigue strength of Tubular Member by FEM

Steel tube structure is used for steel structure such as offshore platform, bridges and so on. Also, all circular members of tubular structures are mainly connected by welding. When the steel tubular structures are subjected to repeated loading, not only the load carrying capacity is reduced but also fatigue cracks may develop at the joint part of steel tubular members which are connected by welding.Carrying out welding, welding initial imperfection such as welding deformation and residual stress are inevitably generated at weld part. It was well known that the effect of welding residual and welding deformation on fatigue strength. However, It’s not clear which affects fatigue strength more. However, it’s difficult to clear the effect on fatigue strength by experiment. To clarify these effect, fatigue analysis was carried out by FEM which is based on continuum damage mechanics. On the other hand, coupled three-dimensional non-steady heat conduction analysis, and the thermal elastic-plastic analysis was carried out to reproduce the initial weld state of tubular member. From the result, not only the fatigue strength of welded tubular member but also the fatigue life could be found by FEM fatigue analysis.

Characterization on the Microstructure Evolution and Toughness of TIG Weld Metal of 25Cr2Ni2MoV Steel after Post Weld Heat Treatment

The microstructure and toughness of tungsten inert gas (TIG) backing weld parts in low-pressure steam turbine welded rotors contribute significantly to the total toughness of the weld metal. In this study, the microstructure evolution and toughness of TIG weld metal of 25Cr2Ni2MoV steel low-pressure steam turbine welded rotor under different post-weld heat treatment (PWHT) conditions are investigated. The fractography and microstructure of weld metal after PWHT are characterized by optical microscope, SEM, and TEM, respectively. The Charpy impact test is carried out to evaluate the toughness of the weld. The optical microscope and SEM results indicate that the as-welded sample is composed of granular bainite, acicular ferrite and blocky martensite/austenite (M-A) constituent. After PWHT at 580 °C, the blocky M-A decomposes into ferrite and carbides. Both the number and size of precipitated carbides increase with holding time. The impact test results show that the toughness decreases dramatically after PWHT and further decreases with holding time at 580 °C. The precipitated carbides are identified as M23C6 carbides by TEM, which leads to the dramatic decrease in the toughness of TIG weld metal of 25Cr2Ni2MoV steel.