Welded Plate Structures Research Articles

The Multi-Frame Imaging Detection of Ultrasonic Guided Waves in Welded Structural Plates Based on Arc Sparse Array with Left Rank

The imaging detection of ultrasonic guided waves in plates using arc sparse arrays is highly significant for weld scattering conditions. A novel approach for detecting welded plate structures using the left rank of ultrasonic guided waves in arc sparse arrays was proposed. The relationship between the receiving matrix and the left rank was analyzed, along with the connection between the arc sparse array with the left rank and the receiving aperture. The imaging mechanism of the ultrasonic guided waves in arc sparse arrays with left rank under weld scattering conditions was investigated. The results of imaging experiments demonstrated a downward trend in the gray and background gray of the multi-frame images. As the left rank reaches approximately 64% of the full rank, the slope of the image gray and background gray decreases gradually, leading to the appearance of an inflection point. With an increasing signal-to-noise ratio curve, the imaging improved during the multi-frame imaging process of ultrasonic guided waves for the arc sparse arrays with left rank under weld scattering conditions. This research showed that the multi-frame imaging of ultrasonic guided waves in welded structural plates using arc sparse arrays with left rank effectively characterized scattering information with millimeter-scale wavelength size. The experimental results validated the feasibility of the theoretical analysis. This research provides a crucial foundation for the further exploration and application of the multi-frame imaging detection of ultrasonic guided waves using irregular arrays in welded structural plates.

Influence of Repair Welding on Mechanical Property and Residual Stress of Laser-MIG Hybrid Welded 6082 Aluminum Alloy Butt Joint

Aluminium welded plate structures are widely used in industry for the sake of the lightweight design. During welding of aluminium plates, unacceptable weld flaws may be found. A gouging and repair welding is usually an economical solution. However, mechanical property and residual stress changes due to repair welding are not well understood. In this study, the coupled thermo-mechanical welding and repair welding simulations were performed. The welding experiments and residual stress tests were also conducted. Samples were evaluated through metallography, tensile test and hardness. The results showed that, owing to the composite effect of the decreased hardness in heat affected zone and increased porosity of the weld, the tensile strength of the joint decreased as the times of repair welding increasing. Numerical and experimental residual stresses agree well with each other. It was showed that, in the original welded joint, the residual stress concentrates in the weld and surrounding of heat affected zone. In the repaired joint, the maximum longitudinal residual stress located in centre of the heat affected zone next to the weld. While the minimum and maximum transverse residual stress appeared on lower and upper surface of the butt joint, respectively. Both the maximum longitudinal and transverse residual stress increased with repair times.

A numerical analysis of friction stir welded joint using FEA

The present work deals with numerical analysis of welding by the FEM. Attempts have been made to determine temperature distribution, distortion, and residual stresses due to welding by finite element method in welded plate structures. General-purpose finite element software ANSYS was used. The FE analysis is split into two parts. To acquire the global temperature history generated during the welding process, a nonlinear transient thermal analysis is initially performed. The temperatures acquired from the thermal analysis are then used as loading to the stress mode in the stress analysis. Though the numerical model gives a more accurate result always there occurs a difference between the numerical result and the experimental result an error of 10.53% between the experimental and the simulated result was obtained.

FULL-SCALE MEASUREMENTS OF WELDING-INDUCED INITIAL DEFLECTIONS AND RESIDUAL STRESSES IN STEEL-STIFFENED PLATE STRUCTURES

Plated structures such as ships and offshore structures are constructed using welding techniques that attach support members (or stiffeners) to the plating. During this process, initial imperfections develop in the form of initial deformations (deflections or distortions) and residual stresses. These initial imperfections significantly affect the buckling and ultimate strength of these structures. Therefore, to assess the strength of welded plate structures, it is very important to predict the magnitude and pattern of welding-induced initial imperfections and their effects on buckling and ultimate strength. To determine the reliability of the prediction methods, it is desirable to validate the theoretical or numerical predictions of welding-induced initial imperfections through comparison with full-scale actual measurements. However, full-scale measurement databases are lacking, as they are costly to obtain. This study contributes to the development of a full-scale measurement database of welding-induced initial imperfections in steel-stiffened plate structures. The target structures are parts of real (full-scale) deckhouses in very large crude oil carrier class floating, production, storage and offloading unit structures. For parametric study purposes, four test structures by varying plate thickness are measured while the stiffener types and weld bead length are fixed. Modern technologies for measuring initial deformations and residual stresses are applied. The details of the measurement methods are documented for the use of other researchers and practicing engineers who welding-induced initial imperfections.

Statistical analysis of initial deflection of aluminium plating between stiffeners

Initial deflections caused by welding have a considerable effect on the ultimate strength of welded plate structures. Therefore, it is important to know the magnitude and shape of initial deflections. Much research has been conducted on the initial welding distortions of steel structures. However, for aluminium alloys’ structures, the data on fabrication-related initial deflections are minimal. Therefore, in this paper, the initial deflections caused by welding are investigated in aluminium plates used for marine structures. Initial deflections of plating between stiffeners are measured for different panels of four aluminium vessels. Vessels were constructed by the metal inert gas (MIG) welding method. Statistical analysis of measured data is carried out for estimating the maximum value of the initial deflections of aluminium plating between stiffeners. The results of this paper can be applied for the ultimate strength calculations of aluminium marine structures.

Friction Stir Welds Strength under Two-Dimensional Stress State Conditions

The friction stir welding (FSW) is a solid-state joining technique. This process is normally used for different aluminum and magnesium alloys. FSW provides joint mechanical properties superior to arc welding. This properties estimation is a result of uniaxial tension test. In the vast majority of cases the welded plate structures are operated under biaxial stress state. This paper aims at establishing a relationship between biaxial loading conditions and mechanical properties in welding of 5083 type aluminum alloy using friction stir welding. The biaxial stress state was formed due to particularly designed samples. The specimens with different geometry and location of the pairs of raisers stresses are considered. All calculations were performed in ANSYS. The experimental verification of the numerical simulation results is presented.

Full-Scale Measurements of Welding-Induced Initial Deflections and Residual Stresses in Steel-Stiffened Plate Structures

Plated structures such as ships and offshore structures are constructed using welding techniques that attach support members (or stiffeners) to the plating. During this process, initial imperfections develop in the form of initial deformations (deflections or distortions) and residual stresses. These initial imperfections significantly affect the buckling and ultimate strength of these structures. Therefore, to assess the strength of welded plate structures, it is very important to predict the magnitude and pattern of welding-induced initial imperfections and their effects on buckling and ultimate strength. To determine the reliability of the prediction methods, it is desirable to validate the theoretical or numerical predictions of welding-induced initial imperfections through comparison with full-scale actual measurements. However, full-scale measurement databases are lacking, as they are costly to obtain. This study contributes to the development of a full-scale measurement database of welding-induced initial imperfections in steel-stiffened plate structures. The target structures are parts of real (full-scale) deckhouses in very large crude oil carrier class floating, production, storage and offloading unit structures. For parametric study purposes, four test structures by varying plate thickness are measured while the stiffener types and weld bead length are fixed. Modern technologies for measuring initial deformations and residual stresses are applied. The details of the measurement methods are documented for the use of other researchers and practicing engineers who want to validate their computational models for predicting welding-induced initial imperfections.

Solder joint failure localization of welded joint based on acoustic emission beamforming

A localization approach of welded joint damage is proposed based on acoustic emission (AE) beamforming. In this method, a uniform line array is introduced to detect the AE signal of welded joints in specified area. In order to investigate the influence of fillet and crimping commonly existing in a welded plate structure during the AE wave propagation process, the finite element method (FEM) is applied to simulate the behavior of AE wave in the specimen. The simulation localization results indicate that the proposed localization approach can effectively localize AE sources although there exist the fillet and crimping, and it is also validated by the pencil-lead-broken test on rectangular steel tube with welded joints. Finally, the proposed method is adopted to localize the failure of solder joint in operation vibration condition. The proposed method is successful to localize the compact AE source caused by the cracked joint based on wavelet packet transform.

Simulation of Cross Set in Frame Structures

The paper deals with modeling methods of frame structures, used in rocket technology. To estimate their inertia, stiffness and strength properties there is a need to create its calculation model. For this purpose now a finite element method is generally used. These models may use various finite elements and combinations thereof. It is obvious that the calculation has found that parameters of the structure under study depend on the selected calculation model. The paper discusses some issues concerning the idealization of elements of the hypothetical frame structure. To simulate the element properties of a longitudinal set (stringers and longerons) and struts as well is offered idealization of beam, because their crosswise dimensions are substantially smaller than the longitudinal ones. Elements of a crosswise force set (frames) represent a welded plate structure that has arch-curved shape of variable cross-section with holes. Welded tubes of different diameter reinforce holes in plates. In vertical plates there are cutouts to mount stringers. To take in full into consideration these features in the rod idealization of frames is impossible. Therefore it seems more appropriate to use plate finite elements to simulate frames. The paper considers two possible frame models the to show their stiffness properties, namely a rod model and a plate one. It shows the advantages and disadvantages of given design schemes of the frame. Based on the test calculations the paper shows which errors in calculating the stiffness properties of the frame under consideration can be obtained using the rod model. Recommendations for judicious use of possible models of the frame at different designing stages are made. To create the studied frame models and their test calculations and analyze the results of calculation was used a SADAS software package developed at the SM8 Department of BMSTU.

Thermal Wrinkling Analysis of the Platelet Thermal Management Devices

A simplified rectangular plate model is built up with three simply supported sides and one free side for the thermal wrinkling analysis of the platelet thermal management devices. By using the static method and the Galerkin's method, the thermal wrinkling of the structural plates under the uniform and no-uniform thermal stress is analyzed; meanwhile, numerical method for solving the platelets with three simply supported sides and one free side is also tested. The analysis method presents in the article could not only apply to the platelet thermal management devices, but also to the the wall of a rectangular vessel with an open top, and to the distortion of a welded plate structure.

Effects of Welding Residual Stresses on High Tensile Steel Plate Ultimate Strength: Nonlinear Finite Element Method Investigations

The primary objective of the present paper is to examine the effects of welding residual stresses on ultimate strength of high tensile steel plates under axial compression in terms of their magnitude and pattern. The ANSYS nonlinear finite element method is employed for the purpose. The secondary objective of the present paper is to study a nonlinear finite element method modeling technique for welded plate structures with residual stresses. Three levels of residual stresses, namely slight, average, and severe, are considered. As another important parameter of influence on the plate ultimate strength, the plate thickness is also varied in the numerical computations to examine their role and trend. Important insights and conclusions developed from the present study are documented.

Optimizing Tack Welding Fabrication Procedures Using Numerical Finite Element Models

The aim of this study was to investigate the influence of different tack welding fabrication procedures on the final deformations of seam welded plate structures. In this study the length of the tacks, number of tacks, and position of tacks with respect to the final seam weld are altered, and their sensitivity with respect to out-of-plane deformation is established. A parametric study of these three different procedural variations is performed via finite element models to identify which fabrication procedures would lead to minimal out-of-plane distortion.

Crack paths in weld details under combined normal and shear loading

In welded plate structures, fatigue cracks may initiate at the intersections between the flanges of longitudinal stiffeners and the web-stiffener attached to a transverse girder. The weld-toe cracks may initiate and propagate in the flange of the longitudinal stiffener, while in certain cases they may initiate from the root of the fillet weld resulting in the separation of the welded attachment from the flange. In order to distinguish such a morphological change of crack growth behavior, series of fatigue tests have been carried out, and the morphological variation of these fatigue cracks are successfully identified in terms of the normal and shear stress distribution acting along the fillet weld between the flange and the attachment.

Characteristics of welding induced initial deflections in welded aluminum plates

It is well known that welding-induced initial deflections, among other factors, significantly affect the ultimate strength behavior of welded plate structures. This means that it is of vital importance to identify the features of plate initial deflections prior to the plate ultimate strength computations. The aim of the present paper is to investigate the characteristics of initial deflections that occur during welding fabrication of aluminum plates used for marine applications. A total of 78 single and multi-bay stiffened plate prototype aluminum structures which are full scale equivalent to sub-structures of an 80 m long all aluminum high speed vessel are constructed by metal inert gas (MIG) welding. Initial deflections of plating between stiffeners are then measured. A statistical analysis of the measured database is performed to determine mean and coefficient of variation (COV) of the plate initial deflection. The insights developed from the present study will be very useful for reliability analyses and code calibrations of ultimate limit state strength and fabrication quality control for welded aluminum plate structures.

Outer Plate-Thickness-Penetration Condition of Fatigue Crack from Inner Members of Welded Plate Structures

Outer Plate-Thickness-Penetration Condition of Fatigue Crack from Inner Members of Welded Plate Structures

A Second-Order Perturbation Method for the Stress Analysis of Solids with Slightly Wavy or Irregular Surfaces

Actual shapes of welded plate structures slightly deviate from the designed geometry due to imperfections mainly caused by welding. In order to investigate the stress concentration due to weld geometry, a second-order perturbation method is applied to the two-dimensional elastic problem of a semi-infinite plane, whose surface slightly deviates from a straight line. The accuracy of the method is confirmed by solving the problem of a semi-elliptical notch under combined tensile and in-plane bending conditions. The method is applied to the problem of a slightly wavy surface, which is sometimes observed in actual weld beads. Since it is well known that the fatigue strength of weldment cannot be predicted simply by using the peak stress of highly stress-concentrated regions, the stress gradient and the stress distribution in the neighborhood of the peak point are also presented. The present method is found to be effective for the analyses of geometrical imperfections with arbitrary surface shapes, which may be difficult to analyze by conventional numerical analysis procedures.