Welding Position Research Articles

A Wideband Antenna Calibration Network Using Multi-Layer Coupling Technology

In this paper, the design methodology of an antenna calibration network using multi-layer stripline-slotline coupling is proposed. A multi-layer coupler and a two-stage Wilkinson power divider are designed to ensure the basically stable amplitude-phase characteristics of coupling and achieve the wide frequency band. To minimize phase imbalance, the lengths of channels should be kept equal to the maximum extent possible. In addition, the transmission line conversion structure is applied at each port for integration with the antenna array. Aiming at the problems of signal crosstalk and mutual coupling, the isolated via holes are installed near the lines and metal spacers are placed over the ports. By using the semi-closed structure, part of substrates is dug out to expose the resistor welding position. A semi-closed calibration network in series-parallel-fed is fabricated to verify the design methodology. In 8-16 GHz, the amplitude-phase characteristics are considerable, in which the coupling is 37-44 dB and phase deviation is below 8∘. The isolation between ports T1-T16 is greater than 33 dB and voltage standing wave ratio (VSWR) of them is lower than 1.8.

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.

Automatic Aluminum Alloy Surface Grinding Trajectory Planning of Industrial Robot Based on Weld Seam Recognition and Positioning

In this paper, we propose a novel method for planning grinding trajectories on curved surfaces to improve the grinding efficiency of large aluminum alloy surfaces with welds and defect areas. Our method consists of three parts. Firstly, we introduce a deficiency positioning method based on a two-dimensional image and three-dimensional point cloud, which enables us to accurately and quickly locate the three-dimensional defective areas. Secondly, we propose a 2D weld positioning method based on the defect area and obtain the spatial position of the 3D weld by combining the relationship between 2D and 3D images. Additionally, we propose an orthogonal projection method from the point cloud to the aluminum alloy surface to calculate the weld reinforcement. Thirdly, we present a space spiral grinding trajectory planning method for complex curved surfaces based on the characteristics of the weld reinforcement, spatial position, and spatial position information of the defect area. This method shortens the grinding time of the defect area and improves efficiency. Simulation and experimental results show that our grinding trajectory planning method is more efficient than other grinding methods in removing defects from the surface of aluminum alloys. Moreover, the defect area after grinding is smoother than before.

Forming optimization for WAAM with weaving deposition on curved surfaces

A stable and consistent dimension of the weld bead is crucial and fundamental in manufacturing and remanufacturing components on the complex curved surface by the wire arc additive manufacturing (WAAM) method. In this work, a novel weaving deposition strategy for WAAM was developed to overcome the difficulty in formability caused by the gravity effect at various welding positions on complex surfaces. The relationship between process parameters and response parameters of the woven weld bead was statistically modeled through response surface methodology, and the effects of the forming process parameters and their interaction on the geometric dimensions and the formability of the woven weld bead were investigated systematically. Multi-objective optimization based on the established models was carried out to acquire a stable and consistent weld bead at any angle and any deposition direction on the curved surfaces. The experiments of WAAM with weaving deposition strategy on two curved surfaces were conducted to verify the formability of the optimal forming process parameters. Results indicated that the effects of forming process parameters on the geometric dimension and formability of the woven weld bead are quite complicated, with various influential trends and amplitudes, and strong nonlinear interaction effects. Deposited by the optimal parameter, a stable and consistent weld bead with the dimensional deviation and unevenness index of bead surface being less than 1.55% and 0.035 can be obtained on a curved surface. The overall thickness of multi-bead deposition on curved surfaces is evenly distributed between 2.4 mm and 2.9 mm, with a maximum variation of 0.5 mm between the peak height and valley height of adjacent weld beads. The inconsistency in forming dimension and morphology caused by the geometry of the curved surface is overcome at the upward and downward welding positions by adopting the optimal process parameters. The research was helpful in improving the forming dimensional accuracy and surface quality of WAAM on complex surfaces.

Simulation of Temperature Field in FSW of 6061T6 Aluminum Alloy IGBT Liquid Cooled Radiator Panel

Heat input and temperature field distribution in the welding process are crucial to welding quality. The parameters in the FSW process are optimized to study the influence of the temperature field on a car Insulated Gate Bipolar Transistor(IGBT) liquid cooled radiator panel 6061T6 aluminum alloy under friction stir welding. This paper established the liquid cooled radiator panel with friction stir welding fully coupled thermo-mechanical model, and explored the thermal physical parameters of 6061T6 aluminum alloy based on JMATPRO. Then, the temperature field distribution rules of friction stir welding at the inlet of liquid cooling plate and the weld joint under different welding time are explored by using ABAQUS. The effects of different rotational and welding speeds on the temperature field of the welded joint are also studied. Results show that most of the heat in the FSW process is generated by the shaft shoulder of the tool, and the heat at the welding position is a conical shape. Under the assumption that other technological parameters remain unchanged, the rotational speed of the pin is the most important factor affecting the temperature field of the FSW process.

Electropolishing parameters study for surface smoothening of low-[formula omitted] 650 MHz five-cell niobium superconducting radio frequency cavity

Electropolishing (EP) is applied to niobium (Nb) superconducting radio frequency (SRF) cavities, which are used in particle accelerators for their surface treatment. The EP process for 1.3 GHz cavities has been extensively studied earlier. In this work, a parametric study on EP of low-β (0.61) 650 MHz Nb SRF cavities (LB650), which will be used in pre-production cryomodule for proton improvement plan-II (PIP-II) linear accelerator, was conducted to determine adequate EP conditions for attaining a smooth surface of the cavities. EP performed with the standard parameters and an initial cathode (cathode-I) having a cathode surface area of ∼5% of the cavity surface area yielded a rough equator surface of the cavity. The grain step height on the equator weld position was measured to be ∼32μm. The rough surface was attributed to preferential grain etching confirmed by a polarization curve showing a linear relationship between the EP current and voltage and the absence of the current plateau region. The cathode was modified to make its surface area twice that of cathode-I. The modified cathode (cathode-M) provided a current plateau region in the corresponding I-V curves measured at different cavity temperatures. The onset voltage for the plateau was found to be higher at higher cavity temperatures. This study revealed that even with cathode-M, the standard 18 V was low for EP of such large-sized cavities when the cavity temperature was ≥18 °C. EP performed at a higher voltage of 22–24.5 V with cathode-M yielded a smooth surface with a grain step height of only ∼0.6μm. The applied EP conditions also improved removal uniformity along the cavity length. In contrast to the cavity treated with cathode-I, the cavities treated with cathode-M achieved a significantly higher accelerating gradient (Eacc) in vertical tests conducted in a cryostat at 2 K. The modified EP was found efficient to produce the cavities that achieved Eacc of 22.4 MV/m, required by PIP II project in the baseline RF tests, to qualify for further surface processing used to enhance their quality factors.

Morphology Study of the Corrosion Rate on Weld Joint of Double Side Friction Stir Welding Aluminum Alloy AA6061

DSFSW welding uses the rotating of a tool in the workpiece to create heat owing to friction between workpiece and tool to be connected. Corrosion is influenced by the presence of high heat owing to friction and a non-uniform cooling rate. The heat transforms the metal in the Heat Affected Zone (HAZ) and Weld Metal (WM) region, which can result in flaws such porosity, kissing bond, fractures, voids (from welding penetration), and flash as well as changes to the microstructure. Changes in the microstructure of welded joints can affect the resistance of welded joints to corrosion. The purpose of this study is to experimentally analyze the main causes of failure of AA6061 DSFSW joints based on welding temperature, weld defects, microstructure, corrosion rate and morphology of the corroded surface. Temperature testing using thermocouple to analyze the temperature, welding joint defects using DSLR camera and radiography test, microstructure using optical microscope, corrosion rate using AUTOLAB PGSTAT and morphology of corroded surface using SEM. The temperature analysis results show that the advancing side has a higher temperature than the retreating side, due to friction between the tool and base metal accompanied by the opposite welding direction. Visual inspection shows that all specimens and welding positions produce flash that is quite rough on the top (1G) and bottom (4G) surfaces and radiographic test results show incomplete fusion in 4 specimens. Microstructure shows a change in shape and size resulting in recrystallization in the form of fine grains. The highest corrosion rate is found in specimen B 1G welding position of 0.63856mm/year and the lowest corrosion rate in specimen A of 0.058567mm/year. SEM test results show the type of corrosion that occurs in DSFSW welding joints is pitting corrosion.

Failure Analysis and Improvement of Check Valve Reverse Cut-off Seal

Given the failure of reverse cut-off seal performance in the test process of the check valve, the fault location and mechanism analysis were carried out, and the improvement measures were proposed and verified by the test. It is analyzed that the main reason for the failure is the unreasonable design of the moving pair and the welding position of the check valve, which makes the sealing pair cannot fit effectively after the welding of the check valve, leading to the failure of the reverse cut-off seal. By controlling the ratio of the length of the guide surface to the diameter of the guide surface to 1.25, and controlling the distance between the welding position and the sealing pair to 10mm, the failure problem of the reverse cut-off seal of the check valve caused by the unreasonable design of the moving pair and the weld position is successfully solved. The effectiveness of the improved scheme of the check valve is verified by the test.

Physical mechanism of material flow and temperature distribution in keyhole plasma arc welding at initial unstable stage

The initial unstable stage associated with keyhole plasma arc welding affects the stability and quality heavily, especially in the non-vertical welding position, which is difficult to control and restricts the process development and application. This work clarifies the temperature distribution and flow behavior of the process from the digging keyhole stage to the keyhole stable movement stage via an infrared thermography system and high-speed camera system. The experimental results showed that the molten metal on the rear side of the keyhole gradually accumulates and solidifies on the exit side and rear wall of the keyhole. When enough molten metal accumulates on the keyhole rear sidewall, it closes under the action of surface tension. The angle (86°–90°) of the keyhole rear sidewall formation can be used to determine whether the keyhole rear side is closed and reached the keyhole stable movement stage. Simultaneously, the influence of the shifting direction of gravity on the temperature distribution, flow behavior, and solidification morphology of the keyhole weld pool was investigated, which further revealed the initial unstable stage of the welding process. In the flat position, at this stage, the high-temperature area within the keyhole rear sidewall surface gradually accumulates close to the exit side of the weld pool. More molten metal flows to the keyhole exit side by gravity and shear forces, which causes a separation area on the keyhole rear side that is nearer to the exit side of the weld pool. This makes it harder to close the keyhole wall when it is in a flat position during the initial unstable stage. Furthermore, the temperature distribution and flow behavior of the keyhole rear side can be used as another factor to characterize the flow state of the weld pool in all positions and stages of welding.

Experimental investigation on flexural performance of T-joint concrete-filled steel tube with PBL

T-joint concrete filled-steel tube (CFST) members are widely used in many modern structures. The performance of T-joint CFST is studied as the brace is under axial compressive load and chord bends in this paper. A total of eight specimens were designed and manufactured, and FE models were built by ANSYS. The effect of different parameters, including the brace-chord width ratio, the brace-chord thickness ratio, the influence of the PBL, the thickness of the stiffener, the opening diameter and opening space of the PBL, the material strength, and the number and welding position of stiffeners, on the performance of T-joint CFST were investigated through experimental and numerical studies. A criterion for determining when the T-joint CFST with PBL reaches the ultimate bearing capacity is presented. The calculation method in this paper for ultimate moment capacity is derived based on the limit balance theory. The method considering the reinforcement of the brace on the upper flange of the chord, the confinement effect of the steel tube on concrete, and the plastic stress distribution of the steel tube is in better agreement with the test and FE analysis. The results show that the proposed method can well predict the ultimate moment capacity of T-joint CFST, while the method in DBJ is more conservative.

Double side friction stir welding effect on mechanical properties and corrosion rate of aluminum alloy AA6061

Friction Stir Welding (FSW) is a solid-state welding method that has diffusion and different metal structures can blend well. Friction stir welding (FSW) has a weakness, one of which is the lack of flexibility the welding process is only carried out on one side of the plate being welded, so it is not applied on thick materials. Double side friction stir welding is a double working process in which the plate to be welded is subjected to friction from two tools on opposite sides. In the DS-FSW welding process, the dimensions and geometry of the tool and pin greatly affect the quality of the joint. This study to determine the mechanical properties and corrosion rate of Double side friction stir welding aluminum 6061 with variation rotation speed and axis of top and bottom tools. The results of this radiographic test can be seen that specimen 4 welded with variations in speed and tool position has defects in the form of incomplete fusion (IF). The results of microstructural observations showed that the heat caused by the welding process resulted in recrystallization in the form of fine grains in the stirring area and there was no phase change. The highest hardness value in the welding area is specimen B. The largest bending value at the 1G welding positions is specimen D, which is 41.86 MPa with a strain value of 13.23%, while the smallest value at the 4G welding position is specimen A, which is 38.18 MPa with a strain value of 5.03%. The fracture and crack surfaces showed that crack initiation, propagation and material stirring failure occurred in all test specimens, even though the impact test specimen was cut in a small area of Incomplete Fusion, but the test results showed that there was still a surface of the parent metal that had not been stirred. The corrosion test method uses three electrode cells with corrosion media as a substitute for seawater with a salinity of 3.5% NaCl, result of corrosion test is specimen B at the 1G welding position has the highest corrosion rate value of 0.63856 mm/year and specimen An at the 1G welding position has the lowest corrosion rate of 0.058567 mm/year.

PENGARUH POSISI SHIELDED METAL ARC WELDING (SMAW) GERAK SPIRAL KAMPUH V TERHADAP KEKUATAN TARIK DAN STRUKTUR MIKRO BAJA KARBON RENDAH

The purpose of this study was to determine the relationship between the position of shielded metal arc welding (SMAW) with spiral motion V on the tensile strength and microstructure of low carbon steel. The research was conducted by welding V-coated low carbon steel with horizontal 2G, vertical 3G and overhead 4G. The test results show that the welding position does not have a significant effect on the tensile strength of low carbon steel welds, where the 3G vertical position provides a higher tensile strength value than the 2G horizontal position and 4G overhead. The microstructure of acicular ferrite (AF) in the vertical position looks dominant uniformly and tightly.

The Effect Of Welding Current And Electrodes On The Results Of AISI 1045 Steel Welding Strength By Impact Testing

Welding is an activity of joining two or more metals by heating them until they melt, in which the melted or melted workpieces will unite with the help of additional materials to form a connection or a whole piece of metal. The purpose of this study was to determine the effect of welding current, type of electrode and pattern of electrode movement on the strength of the welds against the impact test in order to produce optimal welding strength. The method used in this study is the Taguchi Method. This study used a SMAW welding machine with a 1G welding position. The material used in this research is AISI 1045 steel. The experimental design uses L4 (23) which has been designed by Orthoghonal Array. Next, the welding process and impact test are carried out. The results of the Impact Test were then analyzed using ANOVA. The results of this study are that the highest percentage yield value for the strength of the weld results is found in the type of electrode with a percentage of 21% and the lowest percentage value for the strength of the weld results is in the movement pattern of the electrode with a percentage of 10%.

Crack Identification and Trajectory Planning for Automatic Gas Metal Arc Welding

Gas metal arc welding process has the capability of producing high quality, all position welding, and is easily adaptable for automated welding applications. Repair welding of random cracks on existing assembly/structure through automatic welding would need real time crack/gap identification and weld path generation. In this work, an image processing-based system is presented for identifying the crack geometry. Graphical user interfaces are also developed to take necessary user inputs required at different stages for crack identification, predicting weld bead dimension, and weld path generation. Based on the identified crack geometry and predicted weld bead feature, linear and curved weld path planning methodology is proposed. The proposed modules are validated for a case study by successfully generating the desired weld paths. Different natures of velocity profiles are considered to appraise the role on motion behaviour and a suitable profile is selected for reducing the jerks at sharp corners/via points on the weld path and maintaining uniform bead geometry.

Process Simulation and Optimization of Arc Welding Robot Workstation Based on Digital Twin

For the welding cell in the manufacturing process of large excavation motor arm workpieces, a system framework, based on a digital twin welding robot cell, is proposed and constructed in order to optimize the robotic collaboration process of the welding workstation with digital twin technology. For the automated welding cell, combined with the actual robotic welding process, the physical entity was digitally modeled in 3D, and the twin welding robot operating posture process beats and other data were updated in real time, through real-time interactive data drive, to achieve real-time synchronization and faithful mapping of the virtual twin as well as 3D visualization and monitoring of the system. For the robot welding process in the arc welding operation process, a mathematical model of the kinematics of the welding robot was established, and an optimization method for the placement planning of the initial welding position of the robot base was proposed, with the goal of smooth operation of the robot arm joints, which assist in the process simulation verification of the welding process through the virtual twin scenario. The implementation and validation process of welding process optimization, based on this digital twin framework, is introduced with a moving arm robot welding example.

Feasibility study on sensing and prediction of backside weld geometry in cold metal transfer welding of X65 pipeline in the vertical-up position

Good root-pass welding is the basic guarantee for the formation of high-performance welded joints. In the 3G (vertical) position, the difference in the directions of gravity and arc force induces the issues of uneven weld shaping and discontinuous weld penetration more serious than those in the 1G (flat) position. In order to obtain a good weld penetration state for cold metal transfer (CMT) root-pass welding in the vertical-up position, the characteristic signals that could characterize the backside weld geometry were explored, and a prediction model for the backside weld width Wb was established. In this study, the topside weld pool images and the electrical signals were collected in real time. It was found that the two-dimensional topside weld pool geometrical parameters, such as weld pool area A, cannot accurately characterize the backside weld geometry. Due to the difference in arc force, the backside weld geometry with large differences can be obtained with a similar A. After the analysis of the electrical signals, the characteristic signals, namely welding heat input HI and the peak current time ratio PTR, which can represent the heat and force in the CMT welding process, respectively, were extracted, and the two were combined to establish a Wb prediction model, which had a good accuracy and laid the foundation for the weld penetration control after that.

Development of 16Cr8Ni low transformation temperature welding material for optimal characteristics under various dilutions due to all repair welding positions

A new low transformation temperature (LTT) welding material 16Cr8Ni was developed to satisfy the optimal characteristics in diluted welds due to all repair welding positions. Its good weldability for all welding positions was tested. The measured Ms temperature of weld metals with different dilutions was between 150°C and 250°C which is the optimal range for compressive residual stress generation and fatigue life extension. The in-situ observation of phase evolution by the synchrotron-based X-ray diffraction technique validated the solidification mode of LTT welds for the prevention of solidification cracks. Moreover, the mechanical properties in the diluted LTT welds were measured by miniature uniaxial tensile tests. Large compressive residual stresses at the welded joints due to all welding positions were confirmed numerical analyses.

Research on 3D curved weld seam trajectory position and orientation detection method

The "teaching-reproduction" mode and off-line programming mode are widely used in traditional welding robots. For curved welding workpieces, the operators need to visually inspect the position and orientation of the weld seam during processing to select the teaching points or the starting point for programming. The welding accuracy depends on the operators’ experience. Re-teaching or re-programming is required after adjusting the welding position or orientation, resulting in poor welding accuracy and efficiency. To enhance the adaptability of the robot to various welding conditions, we propose a 3D curved weld seam trajectory position and orientation detection method. A local welding workpiece point cloud is obtained by laser vision sensor scanning. The point cloud is smoothed by using the moving least squares (MLS) method. The surface variation of each point is calculated, and the surface variation threshold is set to extract the weld seam feature points. The weld seam orientation is calculated by solving the basic vectors of the spatial curve according to the parametric equation of the weld seam trajectory. The rotation angles of the robot are calculated by the transformation matrix between the weld seam local coordinate system and the robot base coordinate system. According to the experiments, the proposed method can adapt to various orientations of the curved welding workpiece and improve the robot's adaptability to orientations, therefore, the accuracy and efficiency of welding will be enhanced.

A novel visual guidance framework for robotic welding based on binocular cooperation

• An initial welding position guidance framework based on uncalibrated visual servoing and binocular cooperation is studied. The proposed method combines the advantages of passive and active vision sensors, and improves the flexibility of the vision system. • The global camera first controls the robot to approach the workpiece through the proposed EKF based uncalibrated visual servoing. Then, the derived cooperative motion equation will lead the robot towards the IWP. • 2 The features extraction algorithms for realizing UVS are studied. The method to estimate the desired position of welding torch is discussed. And a compression strategy for Yolo-v4 is designed to realize real-time welding torch detection, which can be an optional solution for target detection tasks on computational-resource-limited devices. • The simulation experiments demonstrate the feasibility and stability of the proposed guidance framework. The comparison experiments indicate that the framework can increase the flexibility of the vision system while maintaining satisfactory accuracy. Visual sensor based welding guidance technology has played an essential part in intelligentized robotic welding. However, scanning trajectory dependence of the laser vision sensor (LVS) and low accuracy of the passive vision sensor limit the application of single visual sensor based guidance methods in practical welding guidance. Aiming at this problem, a global camera is introduced to LVS system, and a novel initial welding point (IWP) guidance framework based on binocular cooperation is put forward. The robot is first controlled by the global camera to approach the workpiece through the proposed extended Kalman filter based uncalibrated visual servoing (UVS). Then, the derived cooperative equation of the LVS and the global camera will lead the robot toward the IWP. Subsequently, the feature extraction algorithms for UVS are designed. A compression strategy for Yolo-v4 is present to realize real-time welding torch detection in small computing platforms, and the estimation method of desired features is analyzed. Finally, the feasibility of the proposed algorithm is verified through experiments. The proposed framework combines the advantages of rich information for global camera and high precision for LVS, and could be a feasible solution to realize fully autonomous welding guidance.

Research Progress of Robot Vision Sensing Weld Seam Tracking Technology

As the key technology of intelligent welding, seam tracking plays a vital role in the welding process. The development and application of visual sensing technology has laid the foundation for obtaining accurate weld position information. The intelligent combination of visual sensing and welding robots improves the stability and accuracy of welding seam tracking technology. This paper introduces the composition and principle of the welding seam tracking system, and the classification of visual sensing technology. This paper summarizes and analyses the welding seam image processing method and the research status of robot tracking control technology around the process of welding seam tracking. This paper summarizes the current problems of weld tracking technology and looks forward to the future development trend.