•A novel 3D thermo-mechanical model of FSW based on the CEL approach is developed.•Prediction of temperature evolution with tool rotation speeds.•Influence of plastic deformation on material flow and ...joint soundness.•Analysis of the mechanisms governing stress evolution in the welded joint.•The model provides unique insight into the effect of welding parameters on the quality of FSW joints.
The interactions among thermal history, plastic deformation and residual stresses in the friction stir welding (FSW) process under different welding parameters have been widely considered a crucial issue and still not fully understood. In the present study, a novel three-dimensional fully coupled thermo-mechanical finite element (FE) model based on Coupled Eulerian-Lagrangian approach (CEL) has been developed to simulate the FSW process of aluminium alloy AA 6082-T6 and to analyse the thermo-mechanical interaction mechanisms under different welding conditions. The numerical model successfully simulates the plunge, dwell, and welding steps in FSW and captures the evolution of temperature, plastic deformation, and residual stresses in the welded joint. The obtained results were validated by experimental testing with observed cross-weld thermal history, optical macrography and residual stress measurement using the neutron diffraction technique. The results reveal that the tool rotation speed governs the temperature evolution; the peak temperature increased from 740 to 850 °K when the tool rotation speed rose from 800 to 1100 rpm. The rotational speed also affected the plastic deformation, material flow, and the volume of material being stirred during the welding process. Higher plastic deformation is formed in the stirring zone by increasing the tool angular velocity. This behaviour led to an increase in the stirring effect of the welding tool, reduction of the tunnel defect size and enhancing the quality of weldments. The distribution of residual stresses in different zones of the FSW joints has been found to have an M-shaped profile. A significant tensile residual stress is characterised in the edge of the nugget zone in both longitudinal and transverse directions, balanced by compressive stresses in the thermo-mechanically affected zone, heat-affected zone and base metal. The presented FE modelling provides a reliable insight into the effects of the welding parameters on the weld quality of FSW joints and process optimisation with minimised experimental trials.
Display omitted
The local weld geometry and its variability can significantly affect the fatigue strength of structures, especially for non-load-carrying welds. Standardised definitions, such as sharp transition ...radii or undercuts, govern stress-raising effects at the weld toe. High-resolution digital tools can nowadays accurately determine these parameters, allowing for studying the impact of geometry variability on fatigue strength. However, real welds rarely exhibit idealised transitions as multiple radii, undercuts, and ripple lines introduce uncertainty in geometry estimations. Numerical simulations of the actual weld geometry, with all its variations, in combination with probabilistic evaluations, have shown great potential for studying the influence of competing notches in the weld. This study compares probabilistic evaluations of 3D scanned welds with analytical relations for stress concentration factors. Results reveal no clear trend between the analytical expressions and the ratio of simulated sectional stress to nominal stress. This highlights the challenge of directly applying existing analytical equations to idealised measurement data from real welds in their as-welded condition for fatigue strength estimations.
•A comprehensive review on several aspects of the laser transmission welding process is presented.•Laser transmission welding parameters and their effects on the performance of the welds are ...discussed.•Laser transmission weld quality attributes used to assess the quality of the welded joints are reviewed.•Process monitoring techniques for the laser transmission welding process are discussed.•Several applications of laser transmission welding in different industrial sectors have been identified.
Laser transmission welding (LTW) is nowadays a well-received polymer joining process. New applications are emerging more and more due to the unique advantages of LTW over conventional joining processes. This paper provides a comprehensive review on various aspects of LTW techniques through a detailed survey of several scholarly publications, industrial studies, scientific reports, etc. This review focuses primarily on five major aspects of LTW, which are (a) welding parameters and their effects, (b) weld quality attributes, (c) process monitoring techniques, (d) material combinations, and (e) industrial applications. After an introduction to the process, the welding parameters, and how they influence the LTW process are described first. This is followed by a description of the quality attributes of LTW, including weld strength, weld pool dimensions, part gap-bridging ability, meltdown, and weld morphology. Several process monitoring techniques applied to LTW are then discussed for pre-, post-, and real-time monitoring of the process. Subsequently, material combinations that are successfully welded using LTW are described, including welding of polymer to polymer, metal, ceramic, glass, wood, etc. Finally, several applications of LTW in different industrial sectors are identified, and the results of the review are concluded.
A review on high-frequency pulsed arc welding Wang, Zhenmin; Jiang, Donghang; Wu, Jianwen ...
Journal of manufacturing processes,
December 2020, 2020-12-00, Letnik:
60
Journal Article
Recenzirano
The modification of welding current waveform according to practical conditions and requirements, is an important way to improve the welding quality of various metals, especially the application of ...high-frequency pulsed current in arc welding. In this paper, the research activities and progress to date in the application of high-frequency (usually more than 5 kHz) pulsed current in arc welding are reviewed in detail, mainly including four significant categories of output current waveforms and their performance characteristics and weld quality: high-frequency pulsed current waveform, high-frequency pulsed variable polarity current waveform, double-pulsed current waveform and inter-pulse GTAW welding adopting SiC-based power devices. In conclusion, in the fusion welding process, the introduction of high-frequency pulsed current is beneficial to the constriction of welding arc, the increase of weld penetration depth, the reduction of weld porosity, the refinement of the microstructure in weld zone and the enhancement of weld mechanical properties. And in the future, the advanced SiC-based power devices is going to replace the present Si-based power devices and bring about a profound change to the welding processes.
Laser beam welding manufacturing (LBW), being a promising joining technology with superior capabilities of high-precision, good-flexibility and deep penetration, has attracted considerable attention ...over the academic and industry circles. To date, the lack of repeatability and stability are still regarded as the critical technological barrier that hinders its broader applications especially for high-value products with demanding requirements. One significant approach to overcome this formidable challenge is in-situ monitoring combined with artificial intelligence (AI) techniques, which has been explored by great research efforts. The main goal of monitoring is to gather essential information on the process and to improve the understanding of the occurring complicated weld phenomena. This review firstly describes ongoing work on the in-situ optical sensing, behavior characterization and process modeling during dynamic LBW process. Then, much emphasis has been placed on the optical radiation techniques, such as multi-spectral photodiode, spectrometer, pyrometer and high-speed camera for observing the laser physical phenomenon including melt pool, keyhole and vapor plume. In particular, the advanced image/signal processing techniques and machine-learning models are addressed, in order to identify the correlations between process parameters, process signatures and product qualities. Finally, the major challenges and potential solutions are discussed to provide an insight on what still needs to be achieved in the field of process monitoring for metal-based LBW processes. This comprehensive review is intended to provide a reference of the state-of-the-art for those seeking to introduce intelligent welding capabilities as they improve and control the welding quality.
•A BIW weld quality inspection method using vibration response signals has been proposed.•The LGHGNN model is designed for intelligent detection of BIW weld quality.•The cluster upgrade graph pooling ...is proposed to elevate node features.•Hierarchical information interaction and collaborative output.•Parallel anomaly detection for multi-label corresponding to multiple regions.
To enhance the assembly quality in Body-in-White (BIW) assembly, this paper proposes an intelligent detection method for the nugget quality of Resistance Spot Weld (RSW) based on weld joint vibration excitation response signals. The method proposes a novel deep learning model, the Local-Global Hierarchical Graph Neural Network (LGHGNN). LGHGNN can automatically construct graph structures and, by introducing a newly designed upgrade pooling operation, extends the traditional flat structure of graph networks into a hierarchical structure within three-dimensional space. Therefore, LGHGNN achieves layered interaction of local-global information, enabling the model to focus on local details while gaining a broader learning perspective. Additionally, this paper proposes a strategy for multi-label unsupervised anomaly detection that involves layered interaction and collaborative decision-making for local and global graphs. The effectiveness of LGHGNN is demonstrated through its application in the BIW right front door assembly, achieving a remarkable 97.5% average accuracy in multi-region parallel anomaly detection.
The fatigue life of welded structures is dependent on the local geometry and imperfections of the welds. Therefore, optimizing the manufacturing processes to improve the local weld geometry and ...remove possible imperfections can considerably affect the fatigue life of the structure. Post-weld treatments such as burr grinding, and High Frequency Mechanical Impact (HFMI) treatment are commonly used techniques to extend the fatigue life of a weld by modifying the local weld toe geometry. However, employing additional manufacturing processes can have an adverse effect on the Life-cycle cost of a welded structure by increasing production costs. On the other hand, extending the fatigue life of a structure can result in lower maintenance and replacement costs. Therefore, a thorough yet predictive life-cycle cost assessment is required to assess the viability of such treatments and design economically efficient weld structures.
This study assesses the life-cycle cost of welded joints. The fatigue life of the weld in this study is analyzed using the effective Notch Stress method (NS). Furthermore, the weld is post-treated with an automated HFMI treatment to prolong its fatigue life. Moreover, the effect of weld quality on the production cost is analyzed. The results show that every phase of the weld's life-cycle has a significant contribution to the life-cycle cost with the use-phase being the more dominant. The results also depict the impact of the changes in weld quality in the overall life-cycle cost.
•This paper presents a systematic review of hybrid laser arc welding process.•Hybrid laser arc welding utilizes synergic effects of laser welding and arc welding.•The hybrid laser arc welding process ...is 50–100% faster than the laser welding.•High welding speed and deep penetration make this process economical than laser welding.•The growing numbers of industrial applications proved the potential of commercial use.
Hybrid laser arc welding simultaneously utilizes the arc welding and the laser welding, in a common interaction zone. The synergic effects of laser beam and eclectic arc in the same weld pool results in an increase of welding speed and penetration depth along with the enhancement of gap bridging capability and process stability. This paper presents the current status of this hybrid technique in terms of research, developments and applications. Effort is made to present a comprehensive technical know-how about this process through a systematic review of research articles, industrial catalogues, technical notes, etc. In the introductory part of the review, an overview of the hybrid laser arc welding is presented, including operation principle, process requirements, historical developments, benefits and drawbacks of the process. This is followed by a detailed discussion on control parameters those govern the performance of hybrid laser arc welding process. Thereafter, a report of improvements of performance and weld qualities achieved by using hybrid welding process is presented based on review of several research papers. The succeeding sections furnish the examples of industrial applications and the concluding remarks.
Display omitted
Heat generation and plastic deformation during Friction Stir Welding (FSW) produce profound changes in the microstructure and structural properties of welded joints. Strengthening ...precipitate, grain size and crystallographic texture evolution are the most important microstructural changes in the case of welding aluminium alloys. An interaction relationship has been developed in this study to understand the evolution of microstructure during FSW of Al-Mg-Si alloy for a wide range of welding temperatures and plastic deformations by controlling two important process parameters (tool rotation and welding speeds). Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) have been used for microstructural characterisation. The mechanical properties were evaluated using microhardness, tensile and low cycle fatigue tests. In all cases, fine recrystallised equiaxed grains with a partial fibre texture was evolved in the nugget zone. Microstructural development was found to be significantly influenced by the weld pitch (welding speed/rotation speed), as it is controlled the heat input, cooling rate, exposure time and plastic deformations. The strength of the FSW joints is improved by increasing the welding speed because of grain refinement, incomplete dissolution or re-precipitate of strengthening precipitates Mg5Si6(β)´´ and the introduction of edge dislocations. The fatigue performance of FSW joints is dependent on grain size with a remarkable improvement in the fatigue life observed for smaller grain sizes.
