Weld Shrinkage Research Articles

Analytical Study on the Buckling of Cylindrical Shells With Circumferential Thickness Variation Under Varying External Pressure

Abstract In this article, the analytical buckling load coefficient formula for a cylinder with circumferential thickness variation subjected to varying external pressure is established for the first time by developing a quadratic perturbation method. Based on the presented formula, some specific examples that consider either circumferential shell thickness variation or varying lateral pressure are studied and compared with those in the published literature. First, classical cosine thickness variation is analyzed. The computed results of buckling load coefficients indicate that most of differences between the proposed formula and finite element (FE) analyses in previous literature are less than 5%. Second, wind-type pressure load is discussed, and the maximum difference of predicted buckling load coefficients between our formula and results in published article is 2.3%. Third, both circumferential thickness variation and linear liquid pressure are analyzed by the proposed analytical formula and validated by the Galerkin method when both thickness and load variations are small. Therefore, accuracy and reliability of the established formula are validated. For the purpose of engineering application, buckling of a circular shell with local circumferential thickness variation due to weld shrinkage under wind-type pressure is analytically investigated. The effects of thickness variation amplitude, load parameter, half angle of thickness variation, and shell dimensions on buckling load coefficients are studied in detail.

Effects of circumferential weld-induced imperfections on the buckling behavior of fabricated steel toroidal shells

Recently, toroidal shells have increasingly been used in engineering applications owing to their excellent load-resistance characteristics. Weld shrinkage during manufacturing leads to deviations from the ideal shell geometry, which is an inevitable imperfection of fabricated steel toroidal shells. To the best of our knowledge, there are no existing studies on the buckling sensitivity of fabricated steel toroidal shells to circumferential weld-induced imperfections. This study presents a modified technique for modeling circumferential weld-induced imperfections, which is employed in a geometrically and materially nonlinear analysis with imperfections (GMNIA) to investigate the imperfection sensitivity of two steel toroidal shells fabricated using different manufacturing processes. The weld imperfections applied on the finite element models were evaluated by modifying Rotter and Teng's weld depression profiles. The procedures for modeling the weld depressions and solving the critical load using the Riks method in ABAQUS are reviewed in detail herein. The obtained buckling results exhibited good agreement with Blachut's experimental results. Furthermore, parametric studies on the relationship between the buckling knockdown factors and the amplitude-to-shell thickness ratios of the imperfect shells revealed the superiority of the fabricated toroidal shells, which can be very beneficial for engineering applications.

Optimization of Melt and Coolant Temperature on Defects of Injection Molded Toothbrush Handle

The toothbrush handle is an injection molded product that rejects up to 10%. One of the factors that cause defects is the injection molding process settings, namely melting and cooling temperature. The purpose of this optimization is to obtain the optimum value of melt and cooling temperature parameters on product quality (minimum defects) of toothbrush handles using RSM. The methods used include simulation using ANSYS to obtain mold temperature, Autodesk Moldflow to obtain product defects and quality prediction based on input parameters of melt temperature (190o , 200o , and 210o C) and coolant temperature (22o , 24o , and 26o C), and Minitab 19 for RSM optimization. The simulation results that cooling temperature and melt temperature that are too low and high result in high defect values (weld line and shrinkage) in the product, resulting in low quality prediction values. Based on the results of the optimized simulation, the best injection molding setting is at a melt temperature of 200oC and a cooling temperature of 24oC which obtains a toothbrush handle product quality response variable of 78.04% with a minimum weld line value of 0.0277o and a minimum shrinkage depth of 0.009 mm.

Influence on structure and fracture mechanics evaluations of a BWR feedwater nozzle following weld overlay repair

Abstract This present paper summarizes applying weld overlay repair on the feedwater nozzle in a boiling water reactor, and evaluates the influence on the structure and fracture mechanics of the component. The requirements for utilizing a full structural weld overlay, including the weld overlay design, effects of welding residual stresses (WRSs), impacts of weld shrinkage, prediction of potential flaw growth, and influence on ASME Code Section III design evaluations, are further defined in ASME Code Case N-504–2. In order to confirm the effectiveness of the weld overlay design of the nozzle, the WRSs following overlay installation were determined using engineering simulation software. The impacts of weld shrinkage from overlay welding are also addressed. The shrinkage stresses were evaluated via a numerical model of the attached piping system to ensure the design margins of the pipe structure. Since the weld overlay technique is well known to be effective in mitigating crack initiation or cracking to leakage, a fatigue crack growth prediction under ASME Code Section XI must be conducted to address the fatigue qualification of the affected component. The ASME Code Section III construction qualification of the whole nozzle region must consider the applicable thermal transient stresses, structural discontinuities, and bimetallic effects that are caused by the weld overlay. This investigation proves that the current stress analyses of the nozzle and the pipe structure are not significantly affected by the added overlay mass, so the structural integrity of the component can be ensured, meeting the requirements of ASME Code Case N-504–2.

Deformation Evolution Law of Surfacing Welding on Thin Bending Plates Based on the Three-Dimensional Thermal Digital Image Correlation Method

Surfacing on the surface of thin metal bending plates will cause significant deformation, and current numerical simulation and experimental methods cannot fully and truly reflect the deformation state of the bending plate. In this paper, a non-contact detection method based on the three-dimensional (3D) thermal digital image correlation (DIC) method is proposed. The proposed method can be used for the 3D full-field dynamic measurement of metal thin bending plate surfaces. In addition, the evolution law of in-plane and out-of-plane deformation of thin bending plates during surfacing welding and cooling was studied. Moreover, the influence of curvature on the shrinkage deformation of thin bending plate weld was explored, and the correlation between the curvature of thin bending plates and the weld shrinkage was established. Results show that the proposed detection method based on the 3D thermal DIC method can rapidly and accurately detect bending deformation online. The out-of-plane deformation of the surfacing welding of the thin bending plate transits from the disk to the saddle. Furthermore, the curvature of the thin bending plate is inversely proportional to the transverse shrinkage of the weld bead. After the curvature reaches a certain value, it has little effect on the longitudinal shrinkage of the weld bead. This detection method solves the problem of welding deformation simulation verification, truly clarifies the law of welding dynamic deformation, and provides a theoretical basis for welding lightweight manufacturing.

Comparison of Welding Deformation Characteristics by Circumferential Welding for Austenitic and Duplex Stainless Steel Pipe : Experimental Study

During welding of structure, non-uniform thermal distribution is occurred by local heating and conduction in copula. This process causes non-uniform thermal deformation and that occurs thermal stress. Especially, pipe is used in shipbuilding and laying pipe is essential. As well pipe material is applied with STS 316L (Stainless Steel) and STS Duplex(Stainless Steel Duplex) in LNG carrier ship. So welding property of that material is studied in order to predict welding deformation and thermal stress. First of all each material is made a experiment to know thermal distribution and shrinkage deformation. Through this experiment, it was possible to obtain differences in welding shrinkage due to the mechanical and thermal properties of the two materials. As a result, basic data on welding shrinkage for each material were obtained, and it will be used to develop a prediction equation through additional research in the future.

Welding Mode Justification for a T-Joint

The paper proposes a method for calculating the mode of single-pass arc welding depending on the geometric parameters of the T-fillet weld. The authors reveal the dependence of the residual welding stress level on the welding mode, taking into account the stress concentration due to uneven heating and transverse weld shrinkage. Resulting from the comparison of three modes of single-pass arc welding (manual, mechanized, and automatic), the optimal modes that ensure the maximum lifetime of welded structures are determined.

CONTAINER SHIP CELL GUIDE ACCURACY CHECK TECHNOLOGY BASED ON IMPROVED 3D POINT CLOUD INSTANCE SEGMENTATION

Generally, cell guides are installed in the cargo hold of container ships, which improve the loading and unloading efficiency of containers and fix containers when the ship is sailing. However, in actual production, due to the low accuracy of ship loading in sections, and the deviation of welding shrinkage and expansion in relevant sections, errors occur in the loading process of containers, resulting in hidden safety risks or significant economic losses. Given the above situation, it is particularly important to find a high-efficiency cell guide accuracy inspection method for construction monitoring. 3D scanner to obtain three-dimensional data is presented in this paper, based on this paper proposes a new method, this method will be used based on improved instances of 3 d point cloud segmentation model to cell guide the segmentation, and fitting container ship cell guide structure, and then realize the function of container simulation test box, cell guide after the segmentation precision inspection at the same time, for the practicality review, we compared the accuracy data gained from inspection simulation and the measured data. As a result, it was confirmed that both values were within about ±1.5mm. The validity, and reliability of the method are further verified.

Influence of welding sequence on the mechanical properties of a latticed shell formed by orthogonal and oblique members

With the development of economy and the improvement of people’s aesthetic level, large-span latticed shells are increasingly used. Such structures are commonly large in volume and huge in welding. In order to select an optimum welding sequence and avoid correcting complex welding deformation, a latticed shell formed by orthogonal and oblique members was taken as the research object in this paper. The finite element models of single and whole latticed shells were established respectively, and according to the equal deformation principle, the influence of different welding sequence on the deformation and internal force of the structure in each construction stage was quantitatively analyzed. The results show that in the welding and assembling stage of small assembling units in the single latticed shell, welding sequence has the greatest impact on the longitudinal deformation, and the change rate of the longitudinal deformation is up to 83.63%; whereas in the tension, sliding and closure stages of each piece of the latticed shell, the transverse deformation is most affected by welding sequence, and the change rate is 33.05%; in different construction stages, the axial stress of the latticed shell is less vulnerable to welding sequence. Furthermore, it is feasible to control the welding shrinkage deformation by selecting a reasonable welding sequence, and the symmetrical welding sequence from both ends to the middle should be adopted during construction.

Optimization of asymmetric I-beams for minimum welding shrinkage

Abstract A calculation system has been developed to determine the optimum dimensions of asymmetric I-beams for minimum shrinkage. The objective function is the minimum mass; the unknowns are the I-beam dimensions; the constraints are the stress, local buckling, and deflection. Different steel grades have been considered (235, 355, 460 (MPa) yield stress) and other aluminum alloys (90, 155, 230 (MPa) yield stress). The material, the span length, the loading, and the applied heat input have been changed. It is shown, that using optimum design; the welding shrinkage can be reduced with prebending and can save material cost as well.

A novel compliant assembly variation analysis with consideration of initial deviation and welding shrinkage

Welding, as the most common joining technique, causes welding deformations that reduce the geometrical accuracy of hull structures. In conventional variation analysis, welding distortion is not taken into account. In this paper, a compliant assembly variation modeling and analysis method is presented to investigate the impact of local weld-induced shrinkage on the propagation relation from the initial deviation to the final assembly deviation in thin plate assembly. First, welding deformations in the form of inherent strains are incorporated into variation analysis model based on Kirchhoff plate model. Additionally, part deviations are also introduced via equivalent forces in order to consider the effects of geometrical variation on compliant assembly. Then, other variation sources, such as fixture locating errors, are modeled as equality constraints of the mechanical variation model, which are then transformed into boundary conditions with Lagrange multiplier method. With an additional stiffness matrix, we describe concisely the coupling relationship between initial deviations and welding deformations caused by gaps and misalignments. In order to validate the effectiveness of the proposed method, numerical simulations and experimental verifications are carried out for two assembly cases, and the results show that the present method has high prediction accuracy and efficiency. This study provides a potential application for improving assembly dimensions considering the inevitable manufacturing deviations and welding deformations.

Strategy for D-shape assembly of ITER vacuum vessel sector #06 as applying 3D metrology

The first sector of the ITER vacuum vessel (VV) has been delivered to the ITER Organization. One of the critical manufacturing steps is d-shape assembly. The manufactured four poloidal segments (PS 1, 2, 3, 4) are assembled, and then form the d-shape structure with a height of 11.4 m. Each PS is a complex and heavy double-wall structure with an inner shell and outer shell, poloidal and toroidal ribs, and in-wall shielding blocks are filled inside of the double wall as radiation shield. Thus, it is quite difficult to handle for assembly in keeping with the segment final dimensional status, so that it is necessary to set a practical plan. Before conducting actual assembly, the d-shape is virtually fitted using all results of final 3D metrology on each PS. In detail, each inner shell as-built result on four interfaces, plus a margin for welding shrinkage and gap for welding are considered to set the d-shape fit-up reference. To set each PS in the right position as comparing the fit-up reference, the fiducial posts (FPs) on each PS are measured using a 3D metrology system. After done the fit-up on the assembly plate, whole FPs (55 ea.) are checked as verification. As a result, the PS2 and PS4 are shifted Avg 7.4 mm and Avg 7 mm to the poloidal way, respectively. After finished inner shell welding, the whole FPs are also measured. The PS2 and PS4 are still shifted Avg 1.4 mm and Avg 0.8 mm to poloidal way, respectively. Eventually, the as-built dimension on the important part is evaluated with given tolerance as a preliminary prediction of the final d-shape result.

Numerical prediction of deformation in thin-plate welded joints using equivalent thermal strain method

Large welding-induced distortions are inevitably generated in a thin-plate welded joint due to its weak stiffness. In this study, an equivalent thermal strain method based on inherent strain theory is proposed to predict the welding deformation of thin plates. An artificial temperature and an orthotropic thermal expansion coefficient are adopted to directly simulate the welding shrinkage and bending behavior of the cooling phase in all directions. To describe the distribution of transverse inherent strain through thickness more accurately, a composite shell element is employed, which can divide the thickness into multiple layers and set different material properties. A three-dimensional (3D) thermo–elastic–plastic finite element method (TEP-FEM) model is also developed to simulate the welding process of a thin plate and compute the inherent strain. Moreover, an experiment was performed to verify the accuracy of the numerical model. Comparing the results from experimental data, TEP-FEM, and the proposed method, it is discovered that the new method can predict the deformation of a thin-plate welded joint with good computational accuracy.

Manufacturing and welding assembly of the vacuum vessel on JT-60SA

The JT-60SA Vacuum Vessel (VV) was manufactured as the 10 sectors split in the factory and these sectors were weld-assembled as the 360-degree torus with the design offset value of the weld shrinkage. The dimensions as the 10 m scale torus were well controlled regardless of the thin wall thickness of 18 mm and a large amount of welding line due to the double wall structure and 72 port penetrations. The final VV 20-degree sector was installed into the 340-degree sector of the tokamak with the TF coil and the VV Thermal Shield, and the VV was weld-jointed as a torus. This paper reports the design concept to reduce the safety factor and welding amount to achieve the dimension specified, and the result of the VV manufacturing.

Study on High Speed Laser Welding Technology and Numerical Simulation of Driving Line Guide Structure of PWR

The manufacturing accuracy of the guide structure of the PWR control rod drive line (abbreviated as the drive line) is very important to ensure the accurate performance of the function of the drive line. In this paper, the technology of high speed laser welding is studied, and the parameters of low stress and high speed laser welding are obtained. The heat source of laser welding, the shrinkage of laser welding weld and the welding deformation of laser welding are modeled and analyzed. The deformation simulation technology of laser welding of driving line guide structure is established to provide theoretical guidance for the manufacture of laser welding of this part. The specific contents include: laser welding test and thermal cycle test, macroscopic weld forming, residual stress test, heat source model establishment and parameter determination, laser welding weld shrinkage model establishment and welding deformation prediction. Finally, the driving line guide structure welded by high speed laser uses Φ 10.26mm bar drop gauge at the speed of 4 × 5 m / min to pass freely at 0 °, 90 °, 180 °and 270 °, and the friction force is less than 88N. The drop bar gauge of Φ10.26 mm is used to pass freely through the driving line guide structure welded by high speed laser at the speed of 4 ~5 m/min at 0 °, 90°, 180° and 270°, and the friction force is less than 88N.

Avoidance of end crater imperfections at high-power laser beam welding of closed circumferential welds

The present work deals with the development of a strategy for the prevention of end crater defects in high-power laser welding of thick-walled circumferential welds. A series of experiments were performed to understand the influence of the welding parameters on the formation of end crater defects such as pores, cracks, root excess weld metal and shrinkage cavities in the overlap area. An abrupt switch-off of the laser power while closing the circumferential weld leads to a formation of a hole which passes through the whole welded material thickness. A laser power ramp-down causes solidification cracks which are initiated on the transition from full-penetration mode to partial penetration. Defocusing the laser beam led to promising results in terms of avoiding end crater defects. Cracks and pores in the overlap area could be effectively avoided by using defocusing techniques. A strategy for avoiding of end crater imperfections was tested on flat specimens of steel grade S355 J2 with a wall thickness of between 8 and 10 mm and then transferred on the 10 mm thick pipe sections made of high-strength pipeline steel API5L-X100Q.

Effect of Inconel 625 on Microstructure and Mechanical Properties of Gas Tungsten Arc Welded Inconel-713LC Superalloy Joints

This study investigates how the use of Inconel filler metal 625 affects the microstructure and mechanical properties of gas tungsten arc welded joints of an IN-713LC nickel-based superalloy. Due to their difference in composition, obvious weld beads could be found by X-ray detection. In addition, it was found that the γ' strengthening phase was absent and carbide was present between the matrix and the weld bead during gas tungsten arc welding. These carbides are strongly related to the formation of cracking and weld shrinkage during solidification. The absence of the γ' strengthening phase and the presence of weld shrinkage and cracking led to a decrease in the hardness, tensile strength, and elongation of the welded pieces.

Research on welding deformation of CFETR 1/16 vacuum vessel mockup

The 1/16 prototype sector of China Fusion Engineering Test Reactor (CFETR) vacuum vessel is being manufactured by Institute of plasma physics, Chinese academy of sciences (ASIPP). Welding deformation assessment and reduction are the major issues which need to be resolved since they will directly affect the overall contour of the vacuum vessel. In this paper, welding deformation finite element method (FEM) analysis of the 1/16 vacuum vessel was performed with ABAQUS based on the inherent strain theory. The welding shrinkage was compensated by reserving welding allowance, while the angular deformation was decreased by adding the restraints near the welds, as per analysis results. The welding deformation was finally measured by the laser tracker with fixed fiducial points distributed around the 1/16 vacuum vessel. The measurement results met the technical requirements and validated the FEM analysis, which can provide useful engineering instructions and guidelines for series production of vacuum vessel.

Laser dissimilar weldability of cast and rolled CoCrFeMnNi high-entropy alloys for cryogenic applications

This study investigates the effects of welding velocity on weldability of dissimilar cast/rolled high-entropy alloys and the applicability of cryogenic temperatures. Cast HEA side of dissimilar weld metal (WM) indicates a larger dendrite packet and dendrite arm spacing (DAS) than rolled WM. Size difference is associated with epitaxial growth from each base metal (BM). As the welding velocity increases (6–10 m min−1), shrinkage voids and DASs decreases. Dissimilar welds show tensile properties comparable to cast BM, where there are tensile fractures of dissimilar welds. Cryogenic properties of dissimilar welds are superior to those of room-temperature welds, because deformation twins and dislocation densities are significantly formed at 77 K. Therefore, dissimilar welds can be applied to the production of cryogenic products.

Effects of dendrite axis and fusion boundary on stress corrosion cracking of ER 308 L/SS 304L welds in a high-temperature water environment

This study investigated the effects of dendrite axis and fusion boundary (FB) on the stress corrosion cracking (SCC) of 308 L/304 L welds by using an alternating current potential drop (ACPD) technique to measure the SCC growth rates in a simulated boiling water reactor environment. The results show that the ferrite/austenite interfaces are more susceptible to SCC in the SS 308 L welds. Furthermore, the angle between the applied load and the dendrite axis affects the SCC growth rate, and as this angle approached 90°, the SCC crack growth rate increases. The SCC cracks in the heat affected zone (HAZ) are mainly intergranular and some cracks propagate transgranularly. Furthermore, the primary crack in the HAZ propagates along the FB; when reaching FB, some secondary cracks are arrested at the FB. The residual strain caused by weld shrinkage is the crucial factor for the increase in SCC susceptibility in HAZ.