Welding Sequence Research Articles

A Multi-Case-Based Assembly Management Method for the Shipbuilding Industry

Abstract This article describes a method for planning the assembly of ship hulls that focuses on a welding sequence, takes into account subassembly processes and makes use of a previously built database of structures. Different degrees of similarity between structures are taken into account. The described research led to the development of an intelligent hybrid sequencing method for structure assembly that uses fuzzy clustering, case-based reasoning and evolutionary optimization. The method is called ‘Multi-case-Based Assembly Planning (MBAP)’. The method is developed to provide satisfactory solutions with low user effort. The analyses carried out show that the calculations are highly time-efficient. The developed evolutionary algorithm converges on sub-optimal solutions. The MBAP method can be directly implemented by any shipbuilder that assembles hulls. Apart from this, fuzzy clustering integrated with case-based reasoning can be applied in practice. The integration of fuzzy clustering and case-based reasoning has been taken to a level higher than previously described in the literature.

Recent Advances in the Prediction of Weld Residual Stress and Distortion - Part 2

Weld residual stress can contribute to the reduction of structure lifetime and accelerate the formation of fatigue cracks, brittle fractures, or stress corrosion cracking. Distortion can have a significant impact on the dimensional ac-curacy of assembly, structure strength, and fabrication cost. In the past two decades, there have been many significant and exciting developments in the prediction and mitigation of weld residual stress and distortion. This paper reviews the recent advances in mitigation techniques that have been applied in the structure design, manufacturing, and postweld stages. The techniques used in the structure design stage include selecting the type of weld joint and weld groove, using balanced welding, determining appropriate plate thickness and stiffener spacing, and considering distortion compensation. Mitigation techniques used in the manufacturing stage include welding sequence optimization, reducing welding heating input, selecting low-transformation-temperature filler metals, prebending, precambering, constraints, trailing and stationary cooling, in-processing rolling, transient thermal tensioning, and additional heat sources. Postweld mitigation techniques include postweld heating and mechanical treatment. Finally, the remaining challenges and new development needs were discussed to guide future development in the field of mitigating weld residual stress and distortion.

Effect of welding sequence and welding current on distortion, mechanical properties and metallurgical observations of orbital pipe welding on SS 316L

Orbital pipe welding was often used to manufacture piping systems. In orbital pipe welding, a major challenge is the welding torch’s position during the welding process, so that additional methods are needed to overcome these challenges. This paper discusses the influence of welding sequence and welding current on distortion, mechanical properties and metallurgical observations in orbital pipe welding with SS 316L pipe square butt joints. The variation of the orbital pipe welding parameters used is welding current and welding sequence. The welding current used is 100 A, 110 A, and 120 A, while the welding sequence used is one sequence, two sequences, three sequences, and four sequences. The welding results will be analyzed from distortion measurement, mechanical properties test and metallurgical observations. Distortion measurements are made on the pipe before welding and after welding. Testing of mechanical properties includes tensile tests and microhardness tests, while metallurgical observations include macrostructure and microstructural observations. The results show that maximum axial distortion, transverse distortion, ovality, and taper occurred at a welding current of 120 A with four sequences of 445 µm, 300 µm, 195 µm, and 275 µm, respectively. The decrease in ultimate tensile strength is 51 % compared to the base metal’s ultimate tensile strength. Horizontal and vertical microhardness tests show that welding with one sequence produces the greatest microhardness value, but there is a decrease in the microhardness value using welding with two to four sequences. Orbital pipe welding results in different depths of penetration at each pipe position. The largest and smallest depth of penetration was 4.11 mm and 1.60 mm, respectively

Contemporary Progresses in Ultrasonic Welding of Aluminum Metal Matrix Composites

Graphical AbstractA Brief Review of the Ultrasonic welding process flow and sequence for joining aluminium metal matrix composite.

Influence of welding sequence on residual stress distribution and deformation in Q345 steel H-section butt-welded joint

Abstract Based on Marc. MSC software, this paper developed a thermo-elastic-plastic finite element method (FEM) to simulate the welding residual stresses and deformation in the low alloy high strength steel joints. The welding residual stresses and deformation in the Q345 Steel H-section butt-welded joints were calculated using this method. An H-section butt-welded joint was fabricated and the welding residual stresses were measured. Based on the simulation and experiment, the influence of welding sequence on the residual stress distribution and deformation in the Q345 steel H-section butt-welded joint was investigated. The results indicate that the welding sequence has a relatively small effect on the residual stress distribution in the flanges of the H-section joints, but a significant influence on that in the web. Under three different welding sequences, the welding deformations in the joints were similar. In the view of controlling welding residual stress, welding the web first is recommended in the fabrication of the H-section butt-welded joint.

Influence of welding sequence on residual stress evolution in Incoloy825/X52 bimetallic clad plate butt-welded joints

Residual stress controlling is crucial for the service security of weldments. In this work, experimental measurements and finite element method were integrated to study the influence of welding sequence imposed on residual stress distribution of Incoloy825/X52 bimetallic clad plate joints. And the residual stress evolution law inside bimetallic clad plate joints during multi-layer and multi-pass welding was clarified. Results showed that the highest residual stress concentration was always generated in the translation layer and its surrounding region once the base, transition and flyer seam layer were all finished welding no matter what sequence was adopted. Welding sequence did have a significant influence on peak value and areas of both internal and surficial high-stress region of bimetallic clad plate joint.

Numerical modeling of the electron beam welding for port stub of CFETR vacuum vessel

The port stubs are larger welding parts of stainless steel plate, featuring with complicated structure and big overall dimensions contain complex local flanging shape and demand high forming quality. It is very important to forecast the welding stress and control the welding residual deformation exactly to ensure the safe reliability of the structure. In this paper, the welding distortions of port stub were predicted by inherent strain method and the welding sequence and clamping design were optimized. Three possible welding constraints and three welding sequence schemes of the port stub were provided within the actual processing condition, weld distortions were studied. Finally, the smallest welding deformation was under welding constraints 3, welding sequence 1, and the maximum welding deformation was 2.968 mm. The simulations were used to guide the manufacture of the final sequence and clamping design of the port stubs.

Multi-Robot Task Sequencing & Automatic Path Planning for Cycle Time Optimization: Application for Car Production Line

Industrial robots are programmed to repeat a sequence of well-defined tasks, e.g. deburring, cutting and welding. The production cycle time is directly influenced by the task order as well as the way trajectories linking this tasks are generated. In this letter, we present an optimization approach that minimizes the production time as well as the overall movements duration of the robots. We propose a fast algorithm that generates a sequenced near-optimal solution for Multi-Robotic Task Sequencing Problem. We model the problem in the form of a new min (sum-max) Multiple Generalized Traveling Salesman Problem ‘min(sum-max) MGTSP’ model. Near-optimal solutions are obtained to automatically minimize cycle time in collision-free path. The originality of our method lies in its flexibility and ability to be integrated into industrial processes. In this study, we perform a double optimization in both the task and configuration space. Also, the proposed algorithm is able to automatically plan a collision-free trajectory between two robots’ configurations by generating relevant via points which minimizes movements duration. Comparing to other approaches, experiment reveal positive results in terms of efficiency and demonstrate the ability of this method to be integrated into existing industrial software.

Effect of Welding Sequence and the Transverse Geometry of the Weld Overlay on the Distribution of Residual Stress in the Weld Overlay Repair of T23 Tubes

Water-wall tubes are important components in power plants and are used to absorb the heat from the boilers, and they often fail prematurely due to corrosion, erosion, and fatigue during service. To repair the defects, weld overlay repair is often adopted by forming a compressive stress area around the susceptible area to prevent the cracks from propagating. In order to obtain reasonable process parameters of weld overlay repair, a study combining experiments and numerical simulations was performed to investigate the welding residual stress distribution on the repaired area with different welding repair methods. The results reveal that a compressive stress area is generated on the repaired area after the repair, and a center-to-outside welding sequence is better than either a right-to-left welding sequence or an outside-to-center welding sequence when overlaying a one-layer weld; with an increase in the number of weld layers, the compressive stress area of the repaired area is expanded, and the stress level is increased, which results from the upward movement of the compressive stress area of the subsequent-overlaying layer and the superposition of the compression areas of the subsequent-overlaying layer and previous-overlaying layer, respectively. In addition, the number of the weld passes of each layer should be not less than four with the center-to-outside welding sequence.

Computational weld-mechanics assessment of welding distortions in a large beam structure

Unwanted distortions are typically observed in components after the welding process. Physical trial tests and extra post-treatments are being widely utilized in industries to minimize and correct the out of tolerance distortions. These methods are time-consuming and costly. There has been growing interest in digital tools which have great potential to minimize the physical test loops and corrections. In this study welding distortions analysis has been carried out on a large beam structure experimentally and numerically using computational welding mechanics (CWM) techniques such as the inherent strain (local–global) method and the shrinkage method, together with the lumping approach. The estimated distortions from the shrinkage together with lumping approaches were in good agreement with the experimental measurements and the computational time affordable. The inherent strain (local–global) method captured the trend of distortion with an underestimation of distortions. The accuracy of the estimated residuals stresses from the inherent strain (local–global) approach is higher than the one from shrinkage together with lumping approaches. Moreover, the effects of various welding process parameters (i.e. welding sequence, fixture, and weld pool size) on welding distortions were investigated. It is found that following the proper welding sequence could minimize the welding distortion of the beam structure. Increasing the constraints of fixtures can prevent welding distortion effectively and reducing weld pool size results in less welding distortions of the beam structure.

A simplified non-linear numerical method for the assessment of welding induced deformations

Welding numerical simulation has always been a formidable challenge because of the involved complex phenomena to be modelled. The task is increasingly challenging when multi-runs welding or welding of ships is needed to be modelled. In these cases, the computational effort is so high that solving the problem via computational welding mechanics is impossible so far. Alternatively, different simplified numerical strategies were developed to overcome this issue such as those based on the inherent strain. Unfortunately, such numerical models are rarely able to capture the effects induced by a variation of the welding sequence or clamping conditions since they are solved in the elastic filed; most of them are therefore not useful to the design optimization of a welded assembly. In this scenario, a new approach is proposed to quantify the welding induced deformations that uses virtual elements to model the weld bead in the elastic-plastic filed and auxiliary elements to apply equivalent loads determined by experiments on a single welded joint. A specific inverse analysis algorithm has been developed to use the method. The model was applied to a real welded assembly in which both the welding sequence and clamping condition were varied. In addition, for the numerical validation, a novel registration algorithm has been developed to move from solid geometries to middle plane representations. Numerical results were found in good agreement with those obtained by experiments even when the welding sequence and clamping conditions are changed.

Prediction and mitigation of out-of-plane welding distortion of a typical block in fabrication of a semi-submersible lifting and disassembly platform

Out-of-plane welding distortions of block structures during fabrication of offshore structure will significantly influence its dimensional accuracy and production schedule. Taking a B514 block of a semi-submersible lifting and disassembly platform as research object, typical welded joints and their welding conditions were summarized based on actual welding procedure specification (WPS). Effective thermal elastic plastic (TEP) finite element (FE) analysis with parallel computation technology was carried out to examine thermal-mechanical response. Welding inherent deformations, which are considered as the elementary cause of welding distortion, were then evaluated. With welding inherent deformations as mechanical loading, elastic finite element (FE) analysis was then employed to predict dimensional accuracy of examined B514 block, which has a good agreement with measurement data. In order to ensure the fabrication accuracy with less out-of-plane welding distortion, inverse deformation approach was applied to reduce the out-of-plane welding distortion, and influence of welding sequence on out-of-plane welding distortion was also examined. Both mitigation practices have obvious effect on dimensional accuracy of examined B514 block, while corresponding mechanical mechanisms were also clarified.

Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation

Abstract Geometrical variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometrical variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components, can be achieved using the method of influence coefficients (MICs), based on the finite element method (FEM). The sequence with which the spot welding operation is performed influences the final geometrical deformations of the assembly. Finding the optimal sequence that results in the minimum geometrical deformation is a combinatorial problem that is experimentally and computationally expensive. Traditionally, spot welding sequence optimization strategies have been to simulate the geometrical variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, a method is proposed where the springback calculation in the inspection fixture is bypassed during the sequence evaluation. The results show a significant correlation between the proposed method of weld relative displacements evaluation in the assembly fixture and the assembly deformation in the inspection fixture. Evaluating the relative weld displacement makes each assembly simulation less time-consuming, and thereby, sequence optimization time can be reduced by up to 30%, compared to the traditional approach.

Fabrication technologies implemented for the European test blanket modules: Status for HCPB and WCLL

Abstract Within the framework of the European fusion strategy, two tritium Breeder Blankets concepts are developed to be tested in ITER as Test Blanket Modules (TBM): the Water-Cooled Lithium-Lead (WCLL) which uses the liquid Pb-16Li as a breeder, neutron multiplier and tritium carrier, and the Helium-Cooled Pebble-Bed (HCPB) with lithiated ceramic and beryllium pebbles as breeder and neutron multiplier, respectively, and helium purge gas as tritium carrier. Both concepts consider as structural material reduced activation ferritic martensitic steel, the EUROFER97 (X10CrWVTa9-1). Pressurized water (15.5 MPa, 295−328 °C for WCLL) and pressurized helium (8 MPa, 300−500 °C for HCPB) are foreseen for heat removal. The TBM is constituted of a BOX (side caps, first wall), stiffened by stiffening plates (SP) and closed on its back, in the manifold area, with back plates with passing-through elements, like stiffening/tie rods, SP nozzles and inlet/outlet water/He pipes. Internally, breeder units, delimited by SP, are cooled-down by cooling plates for the HCPB and double-wall tubes for the WCLL. This paper describes manufacturing technologies for the TBM and deals with the definition of the preliminary Welding Procedure Specifications (pWPS) and feasibility mock-ups for the manifold area and TBM BOX assembly. The transfer and validation of the pWPS developed for the TBM, from P91 to EUROFER97 steel, is demonstrated. Consolidation of the pWPS for the TBM BOX assembly made with HIP process and development for the HCPB TBM manifold area elements, based on GTAW technique, are discussed. Manufacturing tests are performed using the EUROFER97 steel (RCC-MRx, AFCEN Code rules [ 1 ]). As part of the WCLL conceptual design development activities, an assembly and manufacturing welding sequence is detailed, focusing on design changes and the impact on the selection of manufacturing technologies. The article will present as well the future fabrication developments and the associated design proposals envisaged on TBM.

Digital twin technology for smart manufacturing and industry 4.0: A bibliometric analysis of the intellectual structure of the research discourse

The Digital Twin (DT) concept is gaining increasing attention with the rapid growth of cyber-physical systems and smart manufacturing. DT comprises the digital reflection, replica or identity of physical systems, objects or assets, which, for example, can be used for industrial health monitoring or process optimization and tracking. This study provides an overview of the intellectual discourses of DT research. The 23,419 references of 647 publications on the topic of DT are empirically analyzed using bibliometric methods to identify underlying connections and research streams. Using explorative factor analysis, seven strands of research are objectively identified. These comprise i) DT as paradigm for the virtual representation of real systems, ii) DT for manufacturing processes and human-robot collaboration, iii) cyber-physical systems for coordination between physical and computational elements, iv) Industry 4.0 for the automation of manufacturing and industrial practice, v) relationship extraction and matching in a social manufacturing context, vi) advances in computing and communication technologies and vii) optimization of geometrical variation in spot welding sequences. An objective overview of the DT discourse, its underlying themes and high-impact publications is presented.

Experimental and numerical investigation of hybrid laser arc welding process and the influence of welding sequence on the manufacture of stiffened flat panels

Hybrid laser arc welding (HLAW) has gained growing attention from both industry and academic laboratories for its high efficiency and weld quality. The objective of the present paper is to develop a nonlinear finite element method for predicting the weld-induced deflection and residual stress of semi-industrial scale stiffened panel, using a novel heat source model. The novel hybrid heat source consists of a Goldak's double-ellipsoid mathematical model representing the arc source, combined with a truncated cone Gaussian mathematical model to simulate the laser source. For this purpose, three-dimensional coupled thermo-elastic-plastic finite element model has been developed with ABAQUS using an additional numerical subroutine of DFLUX written in the Fortran programming language to simulate the volumetric heat flux distributions of the HLAW process. The finite element method (FEM) is verified by comparison with experimental measurements of T-joint small-scale naval EH36 steel specimens, welded in horizontal position with full penetration using hybrid laser-arc welding process (HLAW). A good agreement is observed between the numerical results and the experimental measurements, confirming that the model developed in the present paper can be used effectively to predict the deformation behaviour of the stiffened plate structures during shipbuilding. The effect of changing welding sequence on the semi-industrial scale stiffened panel has been also studied. It is concluded that the welding sequence plays an important role in the deformation of the structures. A change of direction in the middle section, in combination with alternation of the welding paths between two consecutive reinforcements welding, leads to a significant decrease of distortion.

INFLUENCE OF TACK WELDS DISTRIBUTION AND WELDING SEQUENCE ON THE ANGULAR DISTORTION OF TIG WELDED JOINT

In this paper the influence of tack welds distribution and welding sequence on angular distortion of the Tungsten Inert Gas (TIG) welded joint was tested. Additionally, the effect of welding current on angular distortion was assessed. For research X2CrTiNb18 (AISI 441) stainless steel (2.5 mm thick) was chosen. During research specimens were prepared with different distributions of tack welds. Then they were welded by different welding sequences with the use of different welding current values. After welding the angular distortion of each specimen was measured by using the coordinate measuring machine. In the next step specimens were cut. Cross-sections were polished and the metallographic macroscopic testing was conducted to check the geometry of performed welds. Performed experiments allowed determining the optimal tack weld sequence and welding parameters for welding thin stainless steel sheets.

Ultrasonic welding of ultrafine grained nickel

Solid state joints were obtained for the first time by ultrasonic welding (USW) of ultrafine-grained (UFG) thin disks of Ni processed by high pressure torsion (HPT). Samples of two types were studied: the ones for lap shear mechanical tests were prepared by joining two disks superimposed on each other under static loads of 4.5 and 6.0 kN, and the other type samples for structural characterization were obtained by sequential welding (consolidation) of four disks. The welding time for both type samples was equal to 1 s. The structure of consolidated samples was studied in their cross section by SEM, EBSD analysis, and also their Vickers microhardness was measured.

EFFECTS OF WELDING CURRENT AND SPEED ON RESIDUAL STRESS AND DISTORTION OF JOINING ST52 ROLLED PLATE IN DIFFERENT WELDING SEQUENCES

Welding is a process of permanent joining parts by different welding methods. Residual stress and distortion are the most common phenomena of this process. Reduction of the residual stresses, distortion and improving the quality of welding are the important subjects of this field. Determining and analyzing the residual stresses and distortion is the main step for these purposes. Welding sequences, speed and current are the most effective parameters of this process. In this study, effects of welding parameters such as welding speed and current, in order to reduce residual stress and distortion of welding ST52 rolled plate in different welding sequences have been studied with three-dimensional thermo-mechanical finite element model by means of ANSYS APDL. By comparing different considered situations, the most efficient welding methods with the least residual stress and distortion by considering different welding sequences have been suggested. It obtains that welding the ST52 rolled plate from edge to edge with higher current and lower speed is the best option in fatigue and load-bearing situations, and welding from the center to both sides simultaneously with lower current and higher speed is the best option for assembly problems.

Effect of welding sequence on residual stress and deformation of Mg alloy fillet welds

In order to investigate the effect of welding sequence on stress distribution and deformation of Mg alloy fillet welds, DE-GMAW modified Gaussian heat source model established by MSC. Marc software was applied to the numerical simulation analysis of welding temperature field and stress field and proved by measurement of residual stress by blind hole method. The results indicated that the deformation and residual stress were lowest according to the sequence of welding fillet welds from the head of cylinder to the end on one side first and then welding in the opposite on the other side. The trend of residual stress measurement results was consistent with numerical simulation analysis results with 10% error, which provided theoretical support for stress distribution and deformation control of Mg alloy fillet welds.