T-joint Fillet Weld Research Articles

Influence of welding sequences and boundary conditions on residual stress and residual deformation in DH36 steel T-joint fillet welds

This paper aims to investigate the influence of welding sequences and boundary conditions on welding-induced residual stress and residual deformation of DH36 steel T-joint fillet welds through experimental and numerical methods. A series of typical experiments of successive and simultaneous double-sided welding conditions are conducted to explore both the magnitude and distribution of temperature field, residual stress and residual deformation. Meanwhile, thermal elastic-plastic finite element analysis based on a double ellipsoidal heat source model is performed to investigate the heat transfer and deformation mechanism during the welding process. The influencing factors are further explored to determine and quantify the residual stress and residual deformation induced by different welding sequences and boundary conditions. There is generally well agreement between the experimental and numerical results in terms of temperature field, residual stress, residual deformation and molten pool morphology. The results show that the welding sequences have an important influence on the magnitude and distribution of residual stress and residual deformation. Continuous simultaneous double-sided welding can significantly reduce residual stress and residual deformation to obtain better-quality welds. Boundary conditions have a significant effect on the distribution and magnitude of residual deformation and little effects on residual stress. Tightening the ends of the flange plate with bolts during the welding process can significantly reduce the deformation.

A fuzzy finite element model based on the eigenstrain method to evaluate the welding distortion of T-joint fillet welded structures

T-joint fillet welded structure is one of the most commonly welded structures in the assembly of vessels, so it is crucial to accurately predict the welding distortion of T-joint fillet as fast as possible for in-process quality controls in ship building industry. Eigenstrain distribution which forms after welding accounts for the appearance of welding distortion, the results obtained from experiment and thermal elastoplastic finite element (FE) analysis indicate that it is closely related with the formation of heat-affected zone (HAZ), however, a quantitative description needs to be determined based on limited experimental data. To deal with this problem, a fuzzy finite element model (fFEM) is proposed to evaluate welding distortion in T-joint fillet welding using the eigenstrain method. A set of coefficients which determines the eigenstrain distribution is introduced as the optimization parameters in fFEM. The optimized coefficients of eigenstrains can be found by introducing the genetic algorithm (GA) and combining it with the commercial FE software ANSYS. The eigenstrain distribution calculated by the optimized coefficients can predict the welding distortion with high accuracy and efficiency, the same optimized coefficients and corresponding eigenstrain distribution can be applied to various dimensions of T-joint welded structures if the welding parameters remain unchanged.

Isogeometric Analysis and Bayesian Optimization on Efficient Weld Geometry Design for Remarkable Stress Concentration Reduction

Shape optimization combined with Isogeometric Analysis will be an efficient design method since exact Computer Aided Design geometries can be used for numerical analysis thanks to the same basis functions. In this study, authors developed an in-house research software JWRIAN-IGA and applied it to optimize the weld geometries of two models, namely a T-joint fillet weld and an elongated boxing fillet weld to reduce stress concentration. A gradient-free stochastic global optimization algorithm, Bayesian Optimization was used to sought optimal geometry parameters. It was shown that the optimized geometry was efficiently designed and the stress concentration in the welds for both cases was greatly reduced.

Methodological approach of evaluation on prefabrication primers for steel structures

To the date, shipbuilding companies have applied shop primer coating which protects the steel surface from global oxidization in environment. Proper shop primer requires either anti-corrosion ability during construction or anti-porosity ability during welding, and those properties contradict to each other. This report tried to derive an optimizing parameter on these conflicting properties to select a proper shop primer. First, sufficient amounts of the natural salt spray tests were carried out to achieve a series of data for the anti-corrosion ability. Second, lots of T-joint fillet welding test were performed to evaluate the trapped porosity formed in the weld pool. According to the experimental data, we could achieve either the rust-formation rate or the porosity-formation rate, then, each rate was generalized as formulae. Then, we tried to combine these conflicting properties to decide an optimum shop primer.

The effect of process parameters and plate thickness on in-plane inherent deformations in T-joint fillet weld

Purpose The purpose of this paper is to quantitatively investigate the effect of process parameters (including welding current, voltage and speed) and plate thickness on in-plane inherent deformations in typical fillet welded joint; meanwhile, the plastic strains remaining in the weld zone are also analyzed under different influencing factors. Design/methodology/approach To achieve the purpose of this study, a thermal-elastic-plastic finite element (TEP FE) model is developed to analyze the thermal-mechanical behavior of the T-welded joint during the welding process. Experimental measurements have verified the validity of the established TEP FE model. Using the effective model, a series of numerical experiments are performed to obtain the inherent deformations under the conditions of different influencing factors, and then the calculation results are discussed based on the relevant data obtained. Findings Through numerical simulation analysis, it is found that the longitudinal and transverse inherent deformations decrease with the increase of welding speed and plate thickness, whereas as the nominal heat input increases, the inherent deformations increase significantly. The longitudinal shrinkage presents a quasi-linear and nonlinear distribution in the middle and end of the weld, respectively. The plastic strains in the cross section of the T-joint also vary greatly because of the process parameters and plate thickness, but the maximum value always appears near the location of the welding toe, which means that this point faces a relatively large risk of fatigue cracking. The inherent deformations are closely related to the plastic strains remaining in the weld zone and are also affected by many influencing factors such as process parameters and plate thickness. Research limitations/implications In this study, relatively few influencing factors such as welding current, voltage, speed and plate thickness are considered to analyze the inherent deformations in the T-welded joint. Also, these influencing factors are all within a certain range of parameters, which shows that only limited applicability can be provided. In addition, only in-plane inherent deformations are considered in this study, without considering the other two out-of-plane components of inherent deformations. Originality/value This study can help to expand the understanding of the relationship between the inherent deformations and its influencing factors for a specific form of the welded joint, and can also provide basic data to supplement the inherent deformation database, thereby facilitating further researches on welding deformations for stiffened-panel structures in shipbuilding or steel bridges.

Experimental and numerical investigation on welding simulation of long stiffened steel plate specimen

The paper presents the results of metal inert gas T-joint fillet welding tests of small scale rectangular stiffened steel plates longer than the standard test specimen. In the literature the focus is typically on plates with a small aspect ratio and the present work deals with plates of higher aspect ratio, which are the typical ones in marine structures, aiming to determine if there is any significant effect of welding along the longitudinal direction. Nonlinear thermo-elasto-plastic finite element models are adopted to evaluate the temperature distribution, welding induced distortions and residual stress in the stiffened plates of shipbuilding steel. Given the difficulty in data acquisition of temperature-dependent properties of the material, a simplified model of the properties is proposed, based on the values at room temperature. Good agreement is observed between the measured and simulated temperatures, indicating that the current finite element approach is appropriate to simulate the welding process. The proposed simplified material model can be efficiently used in the finite element analysis of welded steel structures. It is concluded that the welding parameters have more significant influence on the structural responses than the dimension of the plate.

Optimization of Gas Metal Arc Welding (GMAW) Parameters for Minimum Distortion of T Welded Joints of A36 Mild Steel by Taguchi Method

In this study, the GMAW parameters for welding of A36 mild steel have been investigated to get the minimum of distortion. The type of welded joint used was square groove T-joint fillet weld with filler wire ER70S-6. The welding current and the welding speed were selected as input parameters while the response used was distortion (longitudinal bending distortion and angular distortion). Taguchi method was used to determine optimal welding parameters which the minimum distortion. Design of experiment was set two factors with three level in each factor and three replication, so the L9 Taguchi’s orthogonal array was applied. The minimum conditions were determined using S/N ratio with a quality character of smaller is better (SB). In addition, to determine the significance of the welding parameters used ANOVA. The results show that the welding current of 170 A and the welding speed of 4.0 mm/s were obtained as the minimum of longitudinal bending distortion and angular distortion. Based on analysis of variance, the welding current was a parameter that greatly affects the longitudinal bending distortion with the percentage contribution of 64.36% while angular distortion was strongly influenced by welding speed parameter with the percentage contribution of 53.38%.

A comparison study of BPN and SVM prediction models for inherent deformations of T-welded joints

The inherent deformation method has a significant advantage in predicting the welding deformations for large and complex welded structures, but the premise of applying this calculation method is to determine the values of inherent deformations in a given welded joint in advance. Therefore, it is a problem worthy of study to provide an accurate and rapid evaluation for the inherent deformations in a specific type of welded joint. In this study, an uncoupled thermo-elastic-plastic finite element (TEP FE) model was first developed to simulate the T-joint fillet welding process, and the welding experiments were performed to verify the accuracy of the developed TEP FE model. Then the numerical experiments were carried out to provide the informative data for the establishment of the BPN and SVM models. The appropriate network of the BPN model and the optimal parameters of the SVM model were obtained by the trial-and-error method and genetic algorithm (GA), respectively. In these two models, the input variables are the welding speed, current, voltage, and plate thickness, and the transverse and longitudinal inherent deformations are considered to be the output variables. The research results demonstrate that both the BPN model and SVM model can give a better prediction for the inherent deformations with acceptable accuracy. However, compared with the BPN model, the SVM model shows a better generalization ability for the data outside the training set and is more suitable for predicting the inherent deformations within a certain range of welding parameters.

A study on the prediction of inherent deformation in fillet-welded joint using support vector machine and genetic optimization algorithm

The inherent deformation method has a significant advantage in evaluating the total welding deformations for large and complex welded structures. The prerequisite for applying this approach is that the inherent deformations of corresponding weld joints should be known beforehand. In this study, an intelligent model based on support vector machine (SVM) and genetic algorithm (GA) was established to predict the inherent deformations of a fillet-welded joint. The training samples were obtained from numerical experiments conducted by the thermal–elastic–plastic finite element analysis. In the developed SVM model, the welding speed, current, voltage and plate thickness were considered as input parameters, and the longitudinal and transverse inherent deformations were corresponding outputs. The correlation coefficients and percentage errors for all the samples were calculated to evaluate the prediction performance of the SVM model. The research results demonstrate that the SVM model optimized by GA can be used to assess the longitudinal and transverse inherent deformations for the T-joint fillet weld with acceptable accuracy.

Numerical Study on the Leakage Magnetic Field of Transverse Defect on T-Joint Fillet Weld

Abstract A 3D finite element method model is established for yoke-magnetization detection of a transverse defect on T-joint fillet weld and solved by the finite element software ANSOFT Maxwell (ANSYS, Canonsburg, PA). The leakage magnetic field around the transverse defect is obtained. The relationship between the width of transverse defect and leakage magnetic field signals is identified. The researchers found that the tangential component of magnetic flux leakage density, BX1, tends to be a parabolic distribution and reaches the maximum value near the center of the defect along the length direction. While BX1 shows a bimodal distribution, featuring two peaks near the edge of the defect and one peak valley at the center along the width direction, the normal component of magnetic flux leakage density, BZ1, is very different than that of BX1 along the width direction, presenting an approximate N-shape as a whole. The leakage magnetic field signals of the transverse defect on the fillet weld of the T joint will decay obviously when the scanning line is perpendicular to the weld surface over 0.5 mm. The results of numerical simulation can provide a theoretical foundation to detect and characterize various defects in the fillet weld.

Effect of Double Pulse MIG Welding on Porosity Formation on Aluminium 5083 Fillet Joint

In this article, parameters of Double-Pulse Metal Inert Gas Welding (DP-MIG) was used for minimising a porosity formation in a T-joint fillet weld. AA5083-H112 aluminium alloy (Non-heat treatable series) with the plate thickness of 10 millimetres is base metal for this study. Welding consumables were filler wire ER5356 with a diameter of 1.2 millimetres and shielded by industrial argon gas. Three majorities parameter of DP-MIG were Delta wire feed (m/min), Frequency (Hz) and Duty cycle (%). Measurable signal current pattern and opened porosity on the fractured surface were couple observed to study their relationships. An appropriate image processing technique was employed to quantitative measuring and calculating a size grouping area of several opened porosities overall weld length, precisely. The result found that the optimal was used a low-level of Delta wire feed of 0.8 m/min, a high-level of a frequency of 5.0 Hz, a mid-level of the duty cycle 30 % and a high travel speed 60 cm/min could minimise the porosity formation with complete penetration.

Numerička analiza zaostalih napona u zavarenim pločama u obliku T-spoja korišćenjem tehnike podmodeliranja

A submodeling technique is applied in the framework of this study on a T-joint fillet weld example in order to check finite element mesh sensitivity as well as to obtain more accurate temperatures, displacements and residual stress fields in the weld and its vicinity where the temperature and stress gradients are very high. The submodeling procedure of the welding process is demonstrated step-by-step. The obtained results of the temperature, residual stress and displacement distributions correspond very well with the experimental measurements and analytical solutions from the literature.

Numerical Analysis of Longitudinal Residual Stresses and Deflections in a T-joint Welded Structure Using a Local Preheating Technique

In this paper a numerical analysis of a T-joint fillet weld is performed to investigate the influences of different preheat temperatures and the interpass time on the longitudinal residual stress fields and structure deflections. In the frame of the numerical investigations, two thermo-mechanical finite element models, denoted M2 and M3, were analyzed and the results obtained were then compared with the model M1, where the preheating technique was not applied. It is concluded that by applying the preheat temperature prior to the start of welding the post-welding deformations of welded structures can be significantly reduced. The increase of the preheat temperature increased the longitudinal residual stress field at the ends of the plates. The influence of the interpass time between two weld passes on the longitudinal residual stress state and plate deflection was investigated on two preheated numerical models, M4 and M5, with an interpass time of 60 s and 120 s, respectively. The results obtained were then compared with the preheated model M3, where there was no time gap between the two weld passes. It can be concluded that with the increase of interpass time, the plate deflections significantly increase, while the influence of the interpass time on the longitudinal residual stress field can be neglected.

Numerical simulation of a welding process using a prescribed temperature approach

This paper presents an efficient finite element procedure for the prediction of welding-induced residual stresses and distortions in large structures. It is based on a prescribed temperature approach using some features of an Abaqus extension called Abaqus Welding Interface to significantly improve the computational efficiency and speed up the normally time-consuming and cumbersome welding analysis setup performed by the user. To validate the temperature and residual stress solutions obtained by the presented method, two numerical examples are analyzed. Comparison is made with the experimental measurements and the results obtained by the heat generation rate approach using the element birth and death technique. The first example is a butt-welding of two plates, while the second is a T-joint fillet welding of two plates. The results obtained by the proposed procedure demonstrate a good agreement in comparison with the heat generation rate approach as well as the experimental measurements. Furthermore, the computational efficiency is remarkably improved compared to the heat generation rate approach as the CPU time is reduced up to ~70% in both examples.

A simplified engineering method for a T-joint welding simulation

In the framework of this study, a hybrid sequential thermo-mechanical finite element analysis of T-joint fillet welding is performed. In the thermal analysis, the element birth and death technique is applied to simulate a weld filler deposition, while a mechanical analysis is performed simultaneously to avoid possible problems due to large displacements induced by large strains. The calculated plate deflections are compared with the experimental measurements while the obtained residual stresses are compared with the analytical solution from the literature. The simulated results demonstrate that the proposed method can be effectively used to predict the residual stresses and distortions induced by the T-joint welding of two plates.

An engineering approach for a T-joint fillet welding simulation using simplified material properties

In the present study, a three-dimensional numerical simulation of a T-joint fillet welding of two plates is performed using simplified material properties. To investigate the influence of the temperature-dependent thermo-mechanical material properties of carbon steel on the transient temperature distributions and weld-induced residual stresses and deformations, two different cases are considered. In the first case, all the material properties, except the yield stress, are taken as constant at room temperature. In the second case, to calculate the temperature-dependent material properties, the polynomials defined by the ASCE manual are used. From the simulation results, it is concluded that, compared with the reference case that uses the true properties of the chosen material S355JR, the first case of simplification is more suitable for the prediction of plate deflections, while the second case is more favorable for the assessment of thermal fields, heat-affected zones, residual stress fields and stress intensity factors.

Modeling the high cycle fatigue behavior of T-joint fillet welds considering weld-induced residual stresses based on continuum damage mechanics

A nonlinear continuum damage mechanics (CDM) model for multiaxial high cycle fatigue which incorporates the cyclic plasticity constitutive equation is developed in the finite element (FE) framework. FE simulation of T-joint fillet welding is first performed to identify welding residual stresses employing sequentially coupled three-dimensional (3-D) thermo-mechanical FE formulation. The high cycle fatigue damage model is then applied to the T-joint fillet welds subjected to cyclic fatigue loading to compute the fatigue life considering the residual stresses. The calculated total fatigue life which includes the fatigue crack initiation and the propagation is compared with the test result. The FE results demonstrate that the high cycle fatigue damage model proposed in this work gives a correct prediction of the fatigue life of the welds, and welding residual stresses cannot be disregarded in an estimation of the fatigue life of the welds.

Residual Deflections and Stresses in a Thick T-Joint Plate Structure

In this paper transient thermo-elastic-plastic problem of a thick rectangular T-joint fillet weld plates is solved numerically in which we need to determine the temperature distribution, thermal deflections and stresses when the boundary conditions are known. At the T-joint section (weld pool area) high constant temperature is considered initially and convection boundary conditions are applied at other three edges as well as top and bottom surface of the plate. T-joint section and vertical plate is fixed (case 1) for plate stability, only T-joint section is fixed (case 2) as a boundary constraint for stress analysis. Numerical technique (Finite element method, Ansys software) is used to obtain the solution of the boundary value problem.

Numerical Analysis of the Influence on High Humidity in a T-Joint Fillet Weld for High Strength Low Alloy Steel

Welding at high humidity is frequently needed for the harbor hoisting machinery of steel structures in the coastal port city. A computational procedure is proposed for analyzing residual stress and temperature distributions induced by the T-joint welding in two types of St52-3 high strength low alloy steel plates both 6 mm in thickness. The relative humidity conditions varied from 75 to 90% at constant pressure. The finite element models are employed to evaluate the transient temperature and the residual stress during welding. According to the analysis results, the higher residual stress and the highest concentration of hydrogen are distributed in and surround the heat affected zone (HAZ), and vary with different humidity.

Effects of Sealing Run Welding with Defocused Laser Beam on the Quality of T-joint Fillet Weld

Abstract Fillet weld is the predominant weld type used for connecting different elements e.g. in shipbuilding, offshore and bridge structures. One of prevalent research questions is the structural integrity of the welded joint. Post weld improvement techniques are being actively researched, as high stress areas like an incomplete penetration on the root side or fluctuations in penetration depth cannot be avoided. Development of laser and laser-arc hybrid welding processes have greatly contributed to increase of production capacity and reduction of heat-induced distortions by producing single pass full penetration welds in thin- and medium thickness structural steel parts. Present study addresses the issue of how to improve the quality of the fillet welds by welding the sealing run on the root side with defocused laser beam. Welds having incomplete or excessive penetration were produced with several beam angles and laser beam spot sizes on surface. As a conclusion, significant decrease or even complete elimination of the seam irregularities, which act as the failure starting points during service, is achieved.