Welding Operations Research Articles

An automatic exposure imaging and enhanced display method of line scan camera for X-ray defect image of solid rocket engine shell

During the long-term operation of solid rockets and equipment welding, some invisible defects will appear inevitably. These defective work pieces will bring major safety hazards during service. Based on the designed imaging device, this paper proposed two new automatic-exposure imaging methods suitable for line scan cameras. An efficient feature statistical welding positioning method was designed to ensure the best imaging quality of the effective welding area. To improve the identification of defect information, a new adaptive high-grayscale pseudo-color enhancement algorithm, dynamically updating the number of quantized colors, was designed. The experimental results show that the automatic exposure algorithm of the line scan camera not only can effectively achieve high-quality imaging of X-ray film, but also can greatly shorten the scanning time and improve the scanning efficiency of the X-ray film. The proposed algorithm has been well applied in the high-definition X-ray film digitization equipment developed.

Experimental and numerical analysis on flexural behavior of improved U-bar joint details for accelerated bridge construction

U-bar loop connection is achieving widespread applications in the precast deck panel systems for accelerated bridge construction (ABC), while the welding operations on U-bars poses massive inconvenience and serious cost to the on-site assembly of precast deck panels. To eliminate the heavy welding operations and provide guidelines for design and detailing of U-bar loop connection, a total of nine specimens associated with three U-bar joint details are designed and examined through four-point bending tests. The experimental results suggest that welded splices can be omitted without affecting the moment capacity of wet joints. A notched double-loop connection is further developed to resolve fit-up issues resulting from the interference between studs and U-bars. The joint details involve setting notches at both ends of precast panels and placing additional looped bars in the specifically designed notches. The looped bars inserted in notches overlap with U-bars embedded in precast panels, therefore achieving the continuity of longitudinal reinforcement. The U-bar joints exhibit flexural failure characteristics and satisfactory bearing capacity in the experiment. Furthermore, the influence of lap length, concrete and steel grade, and lacer bars on the flexural behavior of U-bar joints is investigated based on 182 FE models, and the minimum lap length for spliced U-bars in notched double-loop connection is thereby determined. Besides, the proposed equations provide an estimate for the minimum lap length with reasonable accuracy.

Multi-objective optimization approach for Inverse Kinematics of redundant manipulator for welding applications

This article presents an optimization-based approach for determining the Inverse Kinematics (IK) of redundant robot manipulators for industrial welding applications. Nine degrees of freedom (DOF) kinematic configuration of a robot manipulator with one prismatic and eight revolute joints has been modelled to improve maneuverability in a welding environment. To perform welding operations at desired task space locations (TSLs), the IK are to be determined. The IK problem is solved using a constrained multi-objective optimization technique with the objective of a reachability manipulator with minimal positional and orientational errors. An obstacle avoidance algorithm is also implemented to avoid collisions during welding operations. IK Simulations of the redundant manipulator in different welding applications were performed in a MATLAB environment. The obtained results shows that the welding manipulator reached desired locations successfully and this approach is adaptable for various shapes of weld joints.

General expressions for heat distribution, pressure, and current density in argon welding arcs

In welding and wire-arc additive manufacturing (WAAM), a mobile arc is the heat source that enables the deposition of metals and the resulting properties of the final product. Because the arc involves temperatures of 20 000 K, and gas velocities of the order of 300 m/s, there are only a few experiments and models available to determine optimal, or at least acceptable, parameters for the operation such as current, voltage, and arc length. On the other hand, there is a lack of engineering guidance to optimize the processes resulting in costly and time-consuming trial-and-error optimization methods, which also involve wasteful use of energy and scrap parts. In this work, a numerical model of the gas-tungsten arc welding (GTAW) arc was created and validated against experiments. The model considers the arc interactions between a non-consumable electrode and the weld pool and accounts for multiple coupled heat transfer mechanisms: Joule heating, conduction, advection, radiation, and Thomson effect. The conditions considered cover the vast majority of GTAW welding operations. The results are generalized in the form of engineering expressions suitable to be embedded in metamodels, in which the heat source is just a part. Applications include penetration and width of welds and deposition rate in external-wire WAAM.

Welding Line Detection Using Point Clouds from Optimal Shooting Position

A method for welding line detection using point cloud data is proposed to automate welding operations combined with a contact sensor. The proposed system targets a fillet weld, in which the joint line between two metal plates attached vertically is welded. In the proposed method, after detecting the position and orientation of two flat plates regarding a single viewpoint as a rough measurement, the flat plates are measured from the optimal shooting position in each plane in detail to detect a precise weld line. When measuring a flat plate from an angle, the 3D point cloud obtained by a depth camera contains measurement errors. For example, a point cloud measuring a plane has a wavy shape or void owing to light reflection. However, by shooting the plane vertically, the point cloud has fewer errors. Using these characteristics, a two-step measurement algorithm for determining weld lines was proposed. The weld line detection results show an improvement of 5 mm compared with the rough and precise measurements. Furthermore, the average measurement error was less than 2.5 mm, and it is possible to narrow the range of the search object contact sensor for welding automation.

Advances in Robotic Welding for Metallic Materials: Application of Inspection, Modeling, Monitoring and Automation Techniques

The robotic welding manufacturing of metal parts is a very important process, especially in heavy industries such as shipbuilding, oil and gas, automotive, and aerospace. There is a great variety of different techniques for manufacturing by robotic welding, and the welding operations are always in a constant process of evolution, as any advance can be significant to avoid defects during the welding process. Although a great deal of research work has been carried out in recent years, thanks to which results and reviews have been presented on this subject, the main aim of this publication is to define and review works that show the advances in the main inspection, modeling, monitoring, and automated operations during the welding process to avoid, or predictively identify, any possible defect in order to obtain an optimum degree of quality in the welding.

Mathematical modelling for prediction of angular distortion in the MIG welded Aluminium 6101 plates

Metals are commonly joined using the Metal Inert Gas (MIG) which is also known as the Gas Metal Arc (GMA) welding process in the fabrication industries because of their ability to weld an extensive diversity of metals as well as its alloys and composites. It can also get fully automated which makes it appropriate for mass fabrication. In this process, like other arc welding operations, there is a huge amount of heat input into the workpiece due to which there are rapid and non-uniform heating and cooling cycles involved. This results in the thermally generated stresses transverse to the weld due to which angular distortion is very likely to get introduced. The important input parameters which contribute significantly to the angular distortion are found to be voltage (V), torch angle (TA), wire feeding rate (WFR), nozzle-to-plate distance (NPD) and welding speed (WS). In the present work, the analytical method of design of experiments (DoE) is utilized to develop a mathematical model relating these with the angular distortion on the Aluminium 6101 plates. The fitness of the representation is scrutinized using the ANOVA technique. The graphical representation of the direct and the interactive consequences of input variables on the angular distortion is evolved by utilizing the response surface methodology (RSM) approach.

Effects of interlayer forms on the resistance welding performance of PAEK/CF thermoplastic composite laminates

The main purpose of this study is to investigate usability of resistance welding joining method for poly (aryletherketone) (PAEK) thermoplastic matrix/carbon fiber (CF) reinforced composite laminates (PAEK/CF). For this purpose, effects of six different Interlayer Forms having different stainless steel meshes as Heating Elements and different woven glass fiber forms as Insulating Layers were studied. After determining welding parameters for each specimen group, performance of the resistance welding operations was compared by ultrasonic inspection, microscopic examination, DSC analyses, and by three different interlaminar mechanical tests. Analyses and tests generally revealed that use of stainless steel meshes as Heating Elements could supply proper amperage level for the heating, melting and crystallization stages of the PAEK matrix during welding consolidation. Depending on the lay-up configuration of Interlayer Forms, “amperage levels” determined for the heating, melting dwell and crystallization dwell were in the ranges of 46–100 A, 40–90 A and 25–50 A, respectively, It was also observed that in order to prevent Current Leakage problem to the other layers in the composite laminate, rather thicker and heavier woven glass fiber forms as Insulating Layers should be used. Otherwise, not only voids could form in the thermoplastic matrix, but also delamination might occur in the upper or lower PAEK/CF composite laminates being welded. When thicker and heavier insulating layer was used; interlaminar mechanical properties of Single Lap Shear Strength, Fracture Toughness under Mode-I and Mode-II were determined as high as 36.77 MPa, 3.76 kJ/m2 and 4.71 kJ/m2, respectively.

Generation of rule-adhering robot programs for aluminium welding automatically from CAD

This paper presents a method to automatically generate robot welding programs from CAD to address the ever-constant demand for product customisation. Furthermore, to ensure that proper welding operations and structural integrity are met, the generated programs also consider the welding conditions and requirements. These welding conditions and requirements are defined by the weld direction and face relative to gravity and surrounding geometry, which has not been observed in the present research sphere. To achieve this, the approach leverages information that can be extracted from a topological analysis of tessellated geometry local to the weld joint in conjunction with available CAD API functions. Finally, an implementation of the method using Siemens NX and the Robotics Toolbox for Python is presented and tested on three geometrically different node configurations and a stiffener piece provided by industrial collaborators. In all, the proposed system was able to correctly generate programs adhering to allowed welding operations as long as a solution existed. For the more complex node configurations (which require reorientation when welded by humans), 32 weld path programs out of 42 were generated based on the given criteria. For the least complex node, a total of 20 out of 24 were generated with the same criteria. All 14 weld programs were generated for the stiffener representation.

Research on Welding Guidance System of Intelligent Perception for Steel Weldment

In order to achieve intelligent and flexible welding, complete the extraction and path planning of 3-D complex weld seam of large steel weldment, and solve the problems that in the vision-guided welding process, the scanning path depends on manual teaching, and the offline programming depends on the machining and assembly accuracy of the weldment; a vision-guided method for welding robots based on a line structured-light sensor is proposed. First, the 3-D computer aided design (CAD) model of the weldment is used to build an offline welding knowledge library, and then, the scanning path is planned in combination with the point cloud alignment. Then, the sensor collects the point cloud on the surface of the weldment along the scanning path. Second, different weld seam extraction algorithms are proposed according to different weld types. The random sample consensus (RANSAC) algorithm is used to identify the position of weld feature points, and the three-frame method is used to solve the pose of weld feature points. Finally, the weld seam is generated to guide the welding robot to complete the welding operation. The experimental results show that the proposed method can be used for different types and dimensions of weldments and provides flexible welding operations with better versatility and higher intelligence.

Current status and research progress of occupational health monitoring in welding fume operations

Welding operations are widely present in the manufacturing production process, involving a large number of occupational groups, and are the key occupations where work injuries and occupational diseases occur in China. For different welding processes and welding materials, the content and focus of occupational health monitoring are different. At present, the item of occupational health examination in welding operation is in poor consistency with the on-site exposure of occupational hazard factors, and it is mainly concentrated in the stage of disease development, which can not reflect the early health damage caused by welding dust exposure in time. The emergence of biomarkers of welding dust can make up for this defect. Therefore, it is of great significance to describe the current situation of occupational health monitoring of welding dust and summarize the research progress of related biomarkers for the early prevention of diseases caused by welding dust and the practice of occupational health monitoring.

Entropy optimization of Marangoni flow of hybrid nanofluid under the influence of viscous dissipation and activation energy: With melting phenomenon

AbstractAs nanotechnology and optimization develop, the demand for more effective and robust heat transfer fluids with much greater thermal conductivities than ordinary ones grows. Marangoni convection is often employed in coloring on the ground, for example, in fine art mechanisms. Melting and welding operations are the most prominent manufacturing uses of the Marangoni convection principle. This article aims to reveal the characteristics of hybrid nanofluid () and nanofluid () under the influence of Margorani convection and Entropy generation in a porous Darcy‐Forchheimer medium under melting circumstances. Viscous dispersion and activation energy's effects are also taken into account. The suggested fluid flow problem is mathematically modeled. A built‐in shooting technique algorithm tackles the dimensionless flow model. After applying suitable transformations, the governing nonlinear PDEs are reduced to highly nonlinear ODEs. The numerical outcomes of obtained ODEs are attained through the bvp4c technique built‐in MATLAB. The effects of various classes of significant parameters on the rate of heat generation and Bejan number profiles are investigated. The physical impact of the flow‐regulating constraint factors is visualized via graphical representations. The results are summarized based on numerical data compared to important engineering formulas such as surface drag force, Sherwood numbers, Nusselt, and density. In terms of final remarks, the main findings are successfully described. This article delves further into the uses of hybrid nanofluids in the primary study regions of medicine, space, ships, and defense. Some of these research areas include the automotive industry, heat exchangers coolant in machining, heat pipes, and manufacturing, electronic cooling, refrigeration, solar energy as well as applications for ventilation, heating, and air conditioning, nuclear system cooling, generator cooling, transformer cooling, and electronic cooling.

A novel steel bulkhead based on the method of prefabrication and assembly and its first application to the Yuliangzhou immersed tunnel

Temporary bulkheads installed at the end of each tunnel element are indispensable for immersed tunnel elements to be watertight and float. Currently, welded steel bulkheads and cast-in-place concrete bulkheads have been applied in the installation of most immersed tunnels; however, these bulkheads have many inherent drawbacks. For example, existing cast-in-place concrete bulkheads are bulky and cannot be recycled after demolition. In addition, existing welded steel bulkheads, which cannot be fully reused, are installed and dismantled with a large number of on-site welding operations. Relying on the Yuliangzhou Immersed Tunnel in China, a novel steel bulkhead based on the method of prefabrication and assembly, namely, a piece-assembled steel bulkhead, was developed to address the abovementioned problems. The structural components of the new steel bulkhead applied to realize full recycling mainly include steel bulkhead panels, ethylene-propylene-diene-monomer (EPDM) sealing gaskets, steel bearings, and steel connecting bolts. The water tightness function of the new bulkhead was achieved through the compression deformation of the designed EPDM sealing gaskets inside the assembly seams, which were designed as multihole structures to save manufacturing material. Nonlinear finite element simulations were conducted to investigate the gasketed seam mechanical and sealant behavior. It was concluded that the control threshold value of gasketed seam compression displacement needed to satisfy the design requirement for a 250 kPa waterproof capacity could be taken as 15 mm, while that for seam offset displacement was set to 40 mm. To achieve the fast and efficient construction of the new steel bulkhead, a strategy of symmetrically installing and removing steel bulkhead panels piece by piece at one carriageway bore was proposed, and an automatic installation trolley that adjusts the bulkhead panel position in three directions was designed and developed. Finally, the on-site monitoring of the assembly seam displacements and the stress and deformation of the H-shaped steel beam verified that the new steel bulkhead was in a safe state and displayed good watertightness. This bulkhead was successfully applied in the Yuliangzhou Immersed Tunnel project, and this test application supports the use of these technologies in immersed tunnel construction.

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.

Rotary Friction Welding Parameters Effects upon Mechanical Properties and Microstructure of AA2024 Weld Joints

The present work investigates Rotary Friction Welding (RFW) of AA2024 similar joints, where the welding operations were carried out using an adapted device to a column-drilling machine (SUPEMEC J320). This work aims to determine the optimal RFW parameters from an experimental study based on mechanical tests and microscopic observations of weld joints. The best compromise, which offers the highest tensile strength value (499 MPa) corresponds to the joint obtained by using a rotational speed of 2000 rpm, a friction pressure of 12 MPa, and a forging pressure of 17 MPa. The EDX results indicate the presence of the intermetallic compounds (IMCs) in each zone of the weld joints, with varying sizes and a random distribution. This study focuses also on the microscopic analyses of the interface of weld joints and the fracture surfaces that indicates a dominant ductile fracture mode.

Parametric design evolution for production setups; a case study for welding fixtures

Automated design evolution and optimization are concepts of utmost interest to the industry for reducing design time and cost. This paper addresses the development of an automated design solution based on an evolutionary algorithm for a parametric design problem. The design problem addresses welding fixture designs as an integrated geometric design and configuration problem. The suggested automation approach is based on the parameterization of the fixture geometry and the welding process to minimize collisions across moving and static bodies during the welding operation. The aim is to produce a welding fixture design simulation that can be adjusted for specific requirements based on expert knowledge without re-iterating the entire composition of the problem. The modularity is demonstrated by modifications of the design problem formulation aimed at altering the exploration spectrum and design proposals of the welding fixture. An early system integration shows a reduction of designer efforts to 30% compared to a manual process, with an increase in overall process time due to software computational times.

Minimizing occupational risk by automation of the special processes - based on occupational risk assessment

Revolution 4.0 and the resulting changes in process management have a very large impact on the meaning and method of safety management. With the beginning of a new industrial era, it is also necessary to introduce changes in occupational risk assessment. It should be taken into account that economy 4.0, in addition to improving production efficiency, also aims to minimize hazardous factors affecting a human. This paper presents the occupational risk assessment in the position of a welder on the basis of defined hazards. The risk assessment analysis was performed comparatively for manual welding operator and for the operator of an automated welding station. The purpose of the occupational risk assessment was also to identify preventive measures that would minimize the occurrence of risk during the manual welding process, as well as to analyse the impact on the risk after introduction of an automated welding process, and thus eliminating the need to expose the operator to numerous hazardous factors. In the paper it has been shown that many of hazardous factors have a much smaller impact on the level of safety at the employee. Some of the dangerous factors have been almost eliminated. And generally, the introduction of process automation significantly reduces the occupational risk while working in certain professions.

Experimental study of the effects of semi-elliptical defects on the API X52 pipeline and its reparation by welding

The aim of the project is to study experimentally the influence of the semi-elliptical defect on the steel of grade API 5L X52 pipeline and its reparation by welding operation to keep the safety of hydrocarbons transport network. The tests have been performed on the specimens with/without semi-elliptical defects by using two ratios a/c and a/t, where the defects issue on the piping systems wall is treated by using the welding operation, which focuses on the filling the defected surface as same thickness of the base wall of the pipeline after removing the defects. The decrease of ultimate stress is mainly evident depending on the size of crack, where they compared to the base metal results. The experimental results showed that the reliability of the welding operation is proved especially in the ratio a/c =1, which is similar to that found in automatically welded. It is proved that the ratio a/t = 0.2 curve exhibits similarity to the base metal curve and their elongation conforms to API standard of steel X52 grade. Clearly, corrosion defects cause degradation of mechanical property in the order of 44% to 50% depending on the ratio of 0 < a/c ≤1 and from 20% to 80% according to the second ration of 0 < a/t ≤0.8. The obtained results proved that the enhanced of mechanical properties by welding reaches to ultimate stress is 559 MPa for the ratio a/t = 0.2 and 531 MPa for the ratio a/t = 0.5. Finally, the experimental results provided that the impact of semi-elliptical defect has effects on the safety of piping systems where welding became as one of among solutions to repair the piping systems.

Residual Stress Measurement Techniques for Metal Joints, Metallic Coatings and Components in the Railway Industry: A Review

Manufacturing and maintenance procedures in the railway industry regularly implement welding and metal deposition operations to produce joints, coatings and repair structures. During these processes, residual stresses arise through the generation of heat affected zones and plastic deformation. This makes accurate measurements of the internal stresses a critical aspect of manufacturing, monitoring, repair and model validation in the develop new metallic coating and joining technologies. Selection of an appropriate residual stress measurement method has many important factors including component size, resolution and the magnitude and location of internal stresses, often resulting in a combination of techniques required to obtain complete assessment of the stress state. This paper offers a review of residual stress measurement techniques for railway components including rail joints and coatings through comparison of destructive and non-destructive approaches, their measurement capabilities, benefits and limitations. A comprehensive discussion of different applications is provided with a summary of facilities available to both research and industry.

Hand-Held Laser Welding of AISI301LN for components with aesthetic requirements: Toward the integration of machine and human intelligence

The use of Hand-Held Laser Welding (HHLW) systems in the industry has been rapidly growing in recent years as an alternative solution to conventional manual arc-based welding systems. The decreasing cost of fiber laser sources and optics has been a driving factor in enabling a wider use of HHLW systems, beyond the established advantages of laser technology with respect to arc-based systems. While the industrial use of HHLW increases, the subject matter has been studied sparingly in the scientific literature. Due to the intrinsic flexibility of the technology, HHLW systems are highly appealing for joining relatively low thickness metals (≤2 mm) in autogenous configuration in sectors where production lots present low batch and high variability. However, a critical aspect of HHLW is correlated to the operator skill, where welding velocities can vary within and between the welds affecting both their aesthetic and mechanical properties. Hence, the development of combined digital and physical approaches to support manual operations may be highly beneficial. The current study presents an open laboratory HHLW system designed for process development purposes. Beyond conventional manual welding operations, the welding torch could be arranged in different configurations. The system could be combined with a linear axis (enabling welding with stable velocity and inclination) or manually with the aid of a newly developed roller device designed to provide constant speed and inclination. First, the process was benchmarked by joining in butt weld configuration 2 mm thick AISI301LN stainless steel sheets with the linear axis. Successively, four operators with different levels of training (rookie and professional) realized welds with the system in hand-held configuration and with the mechanical roller. The weld width variability was assessed as a direct indicator for aesthetic compliance while tensile tests were allowed to determine the mechanical properties of the joint obtained with different configurations.