Typical Welding Research Articles

High Magnetic Property and Toxicity of Particulate Matter Generated during Welding and Cutting Processes.

Magnetic particulate matter (PM) has raised increasing concern due to its abundant presence in ambient air and negative health impact. However, there is still a lack of comprehensive understanding of their emission sources and toxicities. We here report the observation of high magnetic property and toxicity of PM generated during typical welding and cutting processes. Magnetite, formed during high-temperature operation with less oxygen pressure, was revealed to be the major magnetic contributor. The averaged saturation magnetization and magnetic susceptibility values of fine PM (PM2.5) from welding processes are 1.4-4.2 times greater than those of PM emitted from other unintended emission sources, including iron and steel plants and brake wear, while they are 2.0-5.7 times greater for the cutting processes. Furthermore, PM2.5 from welding and cutting processes are nearly 3.5-4.5 times more neurovirulent and 2.1-7.0 times more likely to induce oxidative stress than those from other magnetic sources in the nerve cells lines. Moreover, all of these magnetic PM2.5 exhibit greater negative health effects than typical atmospheric PM2.5 collected in Shanghai urban regions. These new findings suggest that appropriate occupational protection measures should be implemented for the welding and cutting process to reduce adverse health impacts.

A dual-robot cooperative arc welding path planning algorithm based on multi-objective cross-entropy optimization

In this paper a novel discrete multi-objective cross-entropy optimization (CrMOCEO) algorithm is proposed to solve the path planning problem of dual-robot cooperative arc welding. We strive to find a low-cost, fast and more efficient solution for robotic welding of large complex components. Firstly, an optimization model of dual-robot welding path planning is established by considering various variables and constraints in the actual welding process. Then, three strategies are introduced to improve the multi-objective cross-entropy optimization (MOCEO) algorithm to better solve the discrete path planning problem. Finally, in order to verify feasibility and effectiveness of the proposed algorithm, it is used to solve the 2-, 3-, 5- and 7-objective WFG2–9 problems and plan some typical welding seams of a large complex component, the MOCEO, NSGA-Ⅱ, MOPSO and MOGWO are used for comparison. The simulation demonstrates that the CrMOCEO can obtain better solutions for multiple objectives than the other four algorithms, and the path solved by the CrMOCEO is tested in the Gazebo physical model and workshop site, the results further verified the effectiveness of the CrMOCEO algorithm. Particularly, a series of experiments provide more solutions for actual production.

Development of a novel nonrigid support friction stir welding repair robot for aluminum alloy train

PurposeThis paper aims to develop a specific type of mobile nonrigid support friction stir welding (FSW) robot, which can adapt to aluminum alloy trucks for rapid online repair.Design/methodology/approachThe friction stir welding robot is designed to complete online repair according to the surface damage of large aluminum alloy trucks. A rotatable telescopic arm unit and a structure for a cutting board in the shape of a petal that was optimized by finite element analysis are designed to give enough top forging force for welding to address the issues of inadequate support and significant deformation in the repair process.FindingsThe experimental results indicate that the welding robot is capable of performing online surface repairs for large aluminum alloy trucks without rigid support on the backside, and the welding joint exhibits satisfactory performance.Practical implicationsCompared with other heavy-duty robotic arms and gantry-type friction stir welding robots, this robot can achieve online welding without disassembling the vehicle body, and it requires less axial force. This lays the foundation for the future promotion of lightweight equipment.Originality/valueThe designed friction stir welding robot is capable of performing online repairs without dismantling the aluminum alloy truck body, even in situations where sufficient upset force is unavailable. It ensures welding quality and exhibits high efficiency. This approach is considered novel in the field of lightweight online welding repairs, both domestically and internationally.

A Real-Time Monitoring Method for Droplet Transfer Frequency in Wire-Filled GTAW Based on Arc Sensing.

Droplet transfer frequency is a decisive factor in welding quality and efficiency in gas tungsten arc welding (GTAW). However, there still needs to be a monitoring method for droplet transfer frequency with high precision and good real-time performance. Therefore, a real-time monitoring method for droplet transfer frequency in wire-filled GTAW using arc sensing is proposed in this paper. An arc signal acquisition system is developed, and the wavelet filtering method filters out noise from the arc signal. An arc signal segmentation method-based on the OTSU algorithm and a feature extraction method for droplet transition based on density-based spatial clustering of applications with noise (DBSCAN)-is proposed to extract the feature signal of the droplet transition. A new conception of droplet transition uniformity is proposed, and it can be used to monitor the weld bead width uniformity. Numerous experiments for monitoring droplet transfer frequency in real time are conducted with typical welding parameters. This method enables the real-time observation of droplet transfer frequency, and the result shows that the average monitoring error is less than 0.05 Hz.

Analysis of the Causes of Crooked Sugarcane Crepe Shafts in Sugar Factories

Practical work is a form of education and vocational implementation that is followed by students so that students can work directly in the business world as well as industry or fabrication. Practical work aims to prepare students to become productive human beings and can immediately work in accordance with their respective fields, students can also feel the atmosphere of production and can help deal with some problems- problems experienced by Engineering professionals inside the factory. Therefore, in welding, knowledge must accompany practice, in more detail it can be said that the design of building construction and machines with welded joints, must also be planned about welding methods. This method of inspection, welding material, and type of weld to be used, based on the function of the building parts or machines designed. Based on the definition of DIN (Deutch Industrie Normen) Galvanized Welded Broken Products is the best way to assemble or connect constructions and products made from iron. This welding method is specifically performed for galvanized materials. The iron welding process requires special preparation and skills. Based on the results of fieldwork practices that have been carried out in CV. Sumber Agung Widodo, The process of making panel tables is carried out into several stages, namely the hollow iron cutting, 45- degree galvanized angle cutting, iron plate cutting, elbow iron cutting, splicing by welding, frame painting, and mounting a series of panels to the finished panel table. The materials used are hollow iron, iron plate, elbow iron, iron paint, wheels. The tools used are ac current welding machines, grinders and elbow rulers. Stage Highlights : Practical work enhances students' readiness for the industrial environment. Welding methods must align with building construction and machine design. Fieldwork at CV. ABC involves various stages, including cutting, welding, painting, and assembly. Keywords : Practical work, Welding methods, Galvanized Welded Products, CV. ABC, Iron welding process

Analysis of Weld Joint Strength on Galvanized Material Using Rb-26 Electrode

Practical work is a form of education and vocational implementation that is followed by students so that students can work directly in the business world as well as industry or fabrication. Practical work aims to prepare students to become productive human beings and can immediately work in accordance with their respective fields, students can also feel the atmosphere of production and can help deal with some problems- problems experienced by Engineering professionals inside the factory. Therefore, in welding, knowledge must accompany practice, in more detail it can be said that the design of building construction and machines with welded joints, must also be planned about welding methods. This method of inspection, welding material, and type of weld to be used, based on the function of the building parts or machines designed. Based on the definition of DIN (Deutch Industrie Normen) Galvanized Welded Broken Products is the best way to assemble or connect constructions and products made from iron. This welding method is specifically performed for galvanized materials. The iron welding process requires special preparation and skills. Based on the results of fieldwork practices that have been carried out in CV. Sumber Agung Widodo, The process of making panel tables is carried out into several stages, namely the hollow iron cutting, 45-degree galvanized angle cutting, iron plate cutting, elbow iron cutting, splicing by welding, frame painting, and mounting a series of panels to the finished panel table. The materials used are hollow iron, iron plate, elbow iron, iron paint, wheels. The tools used are ac current welding machines, grinders and elbow rulers. Stage

Numerical simulations and mathematical models in laser welding: a review based on physics and heat source models

The dominant phenomenon in laser welding processes is heat transfer by conduction, making it crucial to gain insights into energy distribution within the heat-affected region, including the melt pool. Thermal analysis enables the description of thermo-mechanical, metallurgical aspects, and also addresses studies related to fluid flow and energy transfer. As research in welding processes has advanced, these models have evolved. This is why it is now efficient to use computational modeling techniques as it allows us to analyze the behavior of laser welding during the process. This underlines the importance of this work which has carried out an exhaustive theoretical literature review with the objective of classifying and describing the numerical simulations of laser welding based on the physics involved. In that sense, the mathematical models and strategies used in laser welding are explored in a general way. Therefore, two types of laser welding by conduction and deep penetration are defined from this point and they are categorized according to the phenomena involved in Model Heat Conduction and Model Integral Multiphysics. This comprehensive review article serves as a valuable resource for higher education students by providing a structured and detailed exploration of laser welding and its mathematical modeling. By classifying and describing numerical simulations based on the physics involved, it offers a framework for students to understand the complexities of this field. Additionally, this innovative approach to organizing and presenting research contributes to educational innovation by facilitating a more efficient and effective learning experience, helping students acquire the knowledge and research skills necessary for advancements in the laser welding domain.

Analysis of the influence of groove welds of oxy-acetylene welding joints on tensile strength and microstructure on steel ST 37

In this study, the authors conducted a study on the analysis of the effect of oxy-acetylene welding joints on tensile strength and microstructure in the HAZ and weld metal areas on st 37 steel plates. The results of this study indicate that the average value of the highest tensile strength value is at V groove weld with the average strength of the welded joint is 4.796 kgf/mm2. While the lowest tensile stress is on the I groove weld of 4.674 kgf/mm2. Meanwhile, from the microstructure test, it can be seen that in the HAZ area each groove. Microstructure in the HAZ area shows that the double V groove weld types are fine ferrite, coarse pearlite and martensite. In type V groove weld the structures formed are ferrite, coarse pearlite and martensite. In type I groove weld the structures formed are ferrite, grain boundary ferrite and fine pearlite. Whereas in the weld metal area, and the results of the microstructure test of the weld area on the V seam, it shows a dense microstructure arrangement, the arrangement is identical to pearlite (dark color) so that the specimen is harder.

Stress relief simulation for post-weld heat treatment process of pressure equipment: Creep constitutive equation considering temperature and stress variations

Due to the limited testing methods and high costs, researches on the evolution law of residual stress in the post-weld heat treatment (PWHT) process of pressure equipment are mainly by numerical simulation, in which the selection of a reasonable and reliable creep constitutive model is crucial to ensure the accuracy of numerical predictions. It is worth noting that the temperature changes and residual stress variation during the heat treatment process result in the following creep characteristics: the creep occurs under different temperatures during the heat treatment processes of heating, holding, and cooling; the creep occurs under different residual stress level where the residual stress varies during the heat treatment stages. Thus, to accurately simulate the stress release behavior during the PWHT process, the proper creep constitutive model must involve the influences of the temperature and the stress state. Meanwhile, current heat treatment simulation usually adopts simplified qualitative approaches, and the creep constitutive models often ignore the physical mechanisms and characteristics of actual creep processes, such as the Norton, the Norton-Bailey, and the Omega models. As a result, the accuracy of heat treatment simulation is limited. In this paper, a new creep constitutive relation under varying temperature and stress is proposed. The hyperbolic-sinusoidal function is used to represent the complete three stages of creep, which compensate the inaccuracy prediction at the first and the third creep stages. Moreover, the Arrhenius function is introduced to characterize the creep response under varying temperature conditions, which enables the prediction of residual stress evolution throughout the entire heating-holding-cooling process of heat treatment. Then, a typical pressure vessel cylindrical circumferential weld is simulated. The stress release during the heat treatment is calculated, and the efficacy of the proposed model is validated through surface residual stress testing. It is found that the creep behavior is a crucial factor in numerical simulation of heat treatment, and the creep constitutive relation can significantly affect the accuracy of heat treatment simulation. The simulation utilizing the hyperbolic-sinusoidal temperature-dependent creep model is much more accurate compared to the classical simulation. The simulation results are much more consistent to the experimental results. Specifically, the traditional model often underestimates the stress state, the residual stress drops abruptly during the heating stage. The residual stress evolution mechanism is simulated using the new model: The majority of residual stress are released during the heating process which primarily relies on the creep strain transformation (contributes up to 85%). The stress state does not change during the holding stage and slight higher at the cooling stage.

Microstructure and Mechanical Properties of Ti-6Al-4V Welds Produced with Different Processes.

The effect of defects and microstructure on the mechanical properties of Ti-6Al-4V welds produced by tungsten inert gas welding; plasma arc welding; electron beam welding; and laser beam welding was studied in the present work. The mechanical properties of different weld types were evaluated with respect to micro hardness; yield strength; ultimate tensile strength; ductility; and fatigue at room temperature and at elevated temperatures (200 °C and 250 °C). Metallographic investigation was carried out to characterize the microstructures of different weld types, and fractographic investigation was conducted to relate the effect of defects on fatigue performance. Electron and laser beam welding produced welds with finer microstructure, higher tensile ductility, and better fatigue performance than tungsten inert gas welding and plasma arc welding. Large pores, and pores located close to the specimen surface, were found to be most detrimental to fatigue life.

A NEW TYPE OF PLUG-IN FRICTION-STIR LAP WELDING BASED ON THE 6061-T6 ALUMINUM ALLOY

In this study a new type of plug-in friction-stir lap welding (PFSLW) is proposed to prepare welded joints based on 4-mm-thick 6061-T6 aluminum alloy sheet. The differences in the cross-sectional morphology, microstructure, cross-sectional hardness and shear properties between the PFSLW joint and the normal friction-stir lap-welding (FSLW) joint are discussed. The results show that the cross-sectional morphology of the PFSLW joint has undergone changes. The PFSLW joint has a mechanical interlocking structure on the advancing side that is beneficial to the connection strength of the joint. The grain structure differs at the boundary between the thermo-mechanically affected zone (TMAZ) and the heat-affected zone (HAZ), and the PFSLW joints show a more pronounced bending deformation of the grain organization near the boundary. The microhardness of PFSLW joints was increased in the TMAZ and HAZ areas, and the lowest hardness is further away from the center of the weld. The failure load of the PFSLW joint has been improved, the microcracks part of the PFSLW joint has a ridge-like structure. In addition, the actual welding width of PFSLW joints was improved.

APPLICATION OF FRICTION WELDING FOR PUMP DESIGN AND MANUFACTURING: A COMPREHENSIVE REVIEW

The discussion regarding the balance between economical and performance for the pump design and manufacturing has been increasing in recent years. Of many intelligent innovations, the use of less costly materials for pump shaft is an interesting solution for the pump design. This solution can also be achieved by selecting less costly materials made from metal. Then, the less costly metal connected to electrical motor is joined with a more costly metal connected to the pump. Since both metals can be difference ones, an advance welding process to join both metals is then required. The friction welding process is expected to fulfill this requirement. In the friction welding, heat is generated during friction between these two dissimilar metals. The generated heat should achieve particular temperatures so that the two dissimilar metals can be joined. There are three types of friction welding, e.g. the stir friction welding, the linear friction welding and the continuous drive friction welding, which can be selected to join these two dissimilar metals. This paper is based on the authors’ experience and literature review to discuss the application of friction welding for the pump design and manufacturing.

Risk of bladder, kidney and prostate cancer from occupational exposure to welding fumes: a systematic review and meta-analysis.

Our aimed to conduct a meta-analysis of cohort studies on risk of genitourinary (GU) cancers in workers exposed to welding fumes (WF). We performed a systematic review of studies published on Pubmed, Scopus and Embase following PRISMA criteria. Two researchers selected cohort studies on WF exposure. From 2582 articles, 7 non-overlapping studies were included. Quality of studies was scored according to CASP. We run a random effects meta-analysis to calculate the relative risk (RR) and 95% confidence intervals (CI) of GU cancer, overall and stratified by cancer, country, and quality score. We included seven studies reporting results on GU cancers, including prostate, bladder and kidney cancer (PC, BC, and KC). The RR was 1.19 (95% CI = 1.07-1.32, 16 risk estimates) for GU cancer; 1.13 (95% CI = 0.90-1.42, 4 risk estimates) for PC; 1.26 (95% CI = 0.98-1.60, 7 risk estimates) for BC and 1.28 (95% CI = 1.12-1.47, 5 risk estimates) for KC. Heterogeneity was present in all meta-analyses (p < 0.001). The increased risk was more pronounced in North American than in European studies (respectively, OR = 1.35, 95% CI = 1.18-1.55; OR = 1.13, 95% CI = 1.01-1.27 p heterogeneity = 0.03). There was no heterogeneity according to quality score (p = 0.4). Data were insufficient to investigate associations by industry or welding type. Publication bias for each cancer was excluded. This meta-analysis suggests increased risk of KC and BC, but not of PC, in workers exposed to WF. Confounding by other occupational and non-occupational risk factors could not be excluded. Data were not adequate to address the risk of specific exposure circumstances.

Heat transfer modeling during thermite welding of rails

Thermite welding of rails is the only technology that allows connecting rails in hard-to-reach places such as turnouts and bridges. Experience in operating thermite welded joints shows that this type of welding is characterized mainly by casting defects. It is known that casting defects depend on the thermal processes occurring during rail welding. This article presents the results of modeling the heat transfer process of thermite welding of rails. The simulation was carried out using the LVMFlow software product. 3D heat transfer models of the “casting mold – weld – rail” system have been developed, considering phase transitions. Based on the proposed models, thermograms of the distribution of temperature fields are presented both over the cross section of the welded joint and along the length of the welded joint.

Technological features of fusion welding of Al – Mg system alloys rationally alloyed with scandium

The results of the formation of macro- and microstructure of welded joints of aluminum alloy sheets of the Al– Mg–Sc system obtained by automatic argon-arc and electron-beam welding are presented. The mechanical characteristics of welded joints and weld metal under the types of welding used are given. Satisfactory weldability of the studied alloy by fusion welding methods is established with the provision of strength properties of welded joints at the level of 0.8...0.85 of temporary resistance of the base metal. The effect of the welding direction in relation to the rolling direction of the sheets on the mechanical properties of welded joints is studied. The destruction of welded joints during the tests occurred in the metal and fusion zone. The fractures are of a macro viscous nature with a viscous pit micro mechanism of destruction. The strength factor of welded joints of aluminum V-1579 alloy is at the level of 0.89 for automatic argon arc welding and 0.79 for electron beam welding.

Сравнительный анализ химического состава и механических свойств различных участков сварного соединения дюралюмина, полученного сваркой трением с перемешиванием

Friction stir welding is an advanced method of joining various metals and alloys in the aircraft and mechanical engineering industries. This type of welding is used to join materials that are difficult to weld or not weldable by conventional methods. The high-strength D16 aluminum alloy is difficult to weld by fusion, which is associated with the formation of a dendritic structure in the fusion zone leading to a decrease in the mechanical strength of the joint. In the work, the microstructure and microhardness of a welded seam of the D16 aluminum alloy produced by friction stir welding was studied. Using scanning electron microscopy and optical metallography, the authors identified the presence of three zones: the weld core, the thermomechanical impact zone, and the heat effected zone. In the central part of the welded joint (in the core), a laminated onion ring structure was discovered. A change in the chemical composition of the aluminum solid solution was identified in different areas of the weld zones, as well as the presence of a concentration gradient within each zone. In the upper part of the welded seam, the solid solution is silicon-enriched and depleted in copper. Due to the solid solution depletion in alloying elements, the aluminum content in the solid solution in the zone of the welded joint is higher compared to the initial state. The microhardness values in different areas of the welded joint correlate with changes in the chemical composition. In the welded joint zone, a significant decrease in microhardness was found compared to the initial state, and a change in microhardness associated with the chemical composition gradient within each zone was also observed.

МЕТОДИКА ПРОВЕДЕНИЯ ИСПЫТАНИЙ АВТОМОБИЛЬНЫХ КУЗОВНЫХ МАТЕРИАЛОВ, СОЕДИНЕННЫХ РАЗЛИЧНЫМИ ВИДАМИ СВАРОК

Methods for determining the strength of welded joints are considered. The welded joints are made by different types of welding and tested in laboratory conditions. Methods of inspection of welded joints are described. The method of destructive testing – tests for shear (rupture), separation and impact strength is selected. The test procedure is described. A laboratory experiment was conducted. The diagrams of destruction are given, the results of laboratory tests are compared with the permissible strength of welded points. The strength of the samples obtained with the help of electric rivets and with the help of contact spot welding exceeded the minimum permissible strength of the welded points of the joints. The considered method of determining the strength of welded joints makes it possible to make an optimal choice of the type of welding for car body repair.

Investigation on estimation of fracture resistance of SS 316 LN welds subjected to various aging conditions and test temperatures

In this study, estimation of fracture resistance (K1c) was carried out for SS 316 LN welds subjected to various aging conditions. The welds were aged at 370, 475 and 550 °C and for 1000-20,000 h durations and were tested at room temperature (RT), 380 and 550 °C. Tensile properties and J-R curves were established for SS 316 LN welds after aging treatments at all test temperatures. Decrease in total elongation was observed after 20,000 h aging durations for all aging temperatures and all test temperatures, compared to as weld condition. From J-R curves, J1c values and equivalent Kj1c values were determined. Decrease in J1c was observed after 20,000 h aging durations for all aging temperatures at all test temperatures. Based on previously proposed model, an attempt was made to estimate fracture resistance (K1c) from tensile properties. Estimation of K1c was carried out for aged welds, including as weld condition at three temperatures. Estimated K1c values were within 1-30 % of the determined fracture toughness values. K1c estimation was also applied for similar type of austenitic stainless steel welds. It is summarized that previous methodology of K1c estimation is applicable for austenitic stainless steel welds.

Numerical and Experimental Analyses of Developed Friction Stir Spot Welding (DFSSW) Based on Systematic Design Process Approach.

This research paper presents a developed technique for Friction Stir Spot Welding (FSSW) to join similar aluminum sheets (6061), and then this technique was analyzed critically based on numerical simulation and experimental work. The objective of this Developed Friction Stir Spot Welding (DFSSW) is to avoid or at least reduce the keyhole defects by optimizing the design parameters of the process. The coupling problem (thermomechanical) was solved numerically using the finite element method to find the variations of temperatures and stress distributions in addition to the applied forces by the tool. Different parameters were considered in the numerical analysis, such as rotational speed and plunge depth. The experimental results proved the success of the developed technique by comparing the available results of tensile shear force with the results of other researchers that applied the traditional FSSW. It was obtained the highest tensile shear force (2388 N) under the optimal working and design conditions, when the rotational speed, plunging depth, height, and diameter of the sliced disc were 2100 rpm, 0.3 mm, 3.5 mm, and 12 mm, respectively. It was found that both the diameter and height of the sliced disc are significant parameters that ensure the success of this new technique when selecting the suitable values for these parameters. Otherwise, selecting unsuitable values of these parameters leads to appearing defects (e.g., flash) or the sample will fail under a low level of tensile shear force. The other essential advantage outcome point of this new technique was reducing the defect of the keyhole significantly compared with the results of typical Friction Stir Spot Welding. According to the results of the promising developed welding procedure that can be automated, it can be used widely in the industrial sectors.

A simplified fracture mechanics method for fatigue life analysis of weld roots

Volvo CE currently uses the effective notch stress method for assessing fatigue life in welded structures. For large structures such as frames, a sub modelling technique with a very fine mesh is necessary using millions of DOF. Stress tensors from unit load cases, estimated with FEA, are combined with time history loading from Multi Body Simulations of the complete machine operating on customer representative digitized test tracks. A critical plane approach (the Modified Wöhler Curve Method) is used to estimate the fatigue life. The usage of the effective notch method implies a very time-consuming design process. An LEFM approach for weld roots would be even more time-consuming but would be a more natural approach since the weld root consists of crack like defects. To overcome the drawbacks with the current design process that involves usage of the effective notch method, a hybrid method is defined using pre-calculated geometry factors for different crack sizes and weld geometries. The geometry factors as a function of crack size, and the weld geometry, are stored in a database. From the unit load cases the structural stress using a coarse mesh in the weld is extracted. Together with the geometry factors, the stress intensity factors may be estimated and used with Paris law to calculate the fatigue life of welds. A comparison between the effective notch method, LEFM and the new hybrid method is carried out for typical fillet welds is presented in this paper.