Optimal design of the fillet weld fastening the wind turbine column

This paper deals with the optimal design of the fillet weld of wind turbine column subjected to bending moment.Under the premise of determined the force acting on the column,in order to further optimize the fillet weld,the minimum volume of corner seam was determined in the case of non-linear design constraints.The constraints relate to the maximal stresses and fatigue of welding seam.A numerical solution to this problem is given by genetic optimization algorithm.The optimisation calculation result indicated that the active condition(constraint)was the stress from the static load.Useful and meaningful information is provided for the engineering field.

Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints

The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.

Effect of welding current on morphology and microstructure of Al alloy T-joint in double-pulsed MIG welding

The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas（DP-MIG） welding process was investigated by simulation and experiment.A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions.The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment.The results show that the best condition is at an average current of 90 A and current difference of 40 A,when the maximum temperature is 200 °C higher than the fusion points,with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base.Under these conditions,Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure.Furthermore,the thermal curves and stress distribution in the experiment are consistent with those in the simulation,verifying the precision of the welding simulation.

Formation, microstructure and mechanical properties of double-sided laser beam welded Ti-6Al-4V T-joint

The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as the correlations of each other were investigated. The results indicate that the quality of weld seams is good without defects such as discontinuity, beading, visible cracks or porosity, which is linked to the steady molten pool behavior and droplet transition. The morphologies of the heat affected zone (HAZ) located on the skin and stringer are disparate. The microstructure of the HAZ and fusion zone (FZ) is mainly comprised of acicular martensiticα′ phases. The microhardness of the HAZ and FZ is higher than that of the base metal (BM) and reaches a maximum value at the HAZ near FZ on the stringer. The tensile specimens along the skin and stringer fractured at the BM with ductile fracture surfaces.

Numerical simulation of temperature fields for T-joint during TIG welding of titanium alloy

Three-dimensional finite element model was established to simulate temperature fields of T-joint titanium sheets during TIG welding with finite element method （FEM） software. Temperature dependent material properties and the effect of latent heat were considered. A technique of element birth and death was used to simulate the process of welded metal filling. Dynamic variation process of temperature fields during T1G welding was achieved. The simulated results agreed well with the measured results.

Numerical simulation of asymmetric fillet weld pool based on temperature field and flow field coupling

The temperature field and flow field were analyzed to solve the problems of unstable penetration and poor forming quality,which always happen in asymmetric fillet welding. In order to explore the effect of the welding parameters on welding and improve the quality of forming,a three-dimensional mathematical model of asymmetric fillet welding was established by using the finite element software COMSOL and the coupling equation. The model was considered about the surface tension gradient,the electromagnetic force,gravity and the effect of temperature,radiation and convection heat on physical properties of the material. The flow field and the growth pattern of the weld pool were analyzed,and the weld pool geometry under different welding currents was compared. The results show that,the thin metal was preferentially penetrated,and with the welding process the weld width expanded until the weld beam was fullpenetration. The heat affected zone was got from weld experiments,its shape and size agreed well with the simulation results,which verifies the validity of the theoretical analysis.

Numerical study of fillet weld leg height of sleeve repair welding for in-service pipeline

This paper presents a mechanical calculation and numerical simulation of the fillet weld of sleeve repair.The mechanical analysis based on the yield criteria is performed to obtain the minimum value of the fillet weld leg height to ensure the strength and loadbearing capacity of the weld. Within the framework of numerical simulation,the parameters of double ellipsoid heat source are determined by fitting method and the simulated molten pool morphology agrees well with the practical weld. Finite element models with various weld leg height are performed to predict the distribution and magnitude of the deformation and stress. The simulation takes into account thermal,metallurgical and mechanical factors,and the maximum value of the fillet weld leg height is obtained based on the magnitude of the deformation and stress.The mechanical calculation and numerical simulation results show that 1.2-2 times wall thickness is an optimal range of fillet weld leg height. And reasonable parameters of sleeve repair for in-service welding are provided for engineering field,which can improve the service life of the weld and production efficiency.

Polarities effect on arc interference in triple-electrode CO2 fillet welding

The occurrence of arc interference between the adjacent arcs becomes an important problem in triple-electrode high speed CO2 fillet welding. To clarify this problem, polarities effects on arc interference were investigated. The experimental results and theoretical analysis showed that the reverse magnetic field generated by the middle wire （ DCEN or DCEP ） decreased the arc deflection due to arc interference. The average arc voltage fluctuations induced by DCEP/DECN/DCEP and DCEN/DCEP/DCEN were smaller than those induced by the other polarities.

Evaluation model for arc fluctuations of triple-electrode high speed fillet welding

To improve the welding efficiency of conventional arc welding, triple-electrode fillet welding was proposed and developed. Stability of triple-electrode fillet welding process is the assurance for ideal joint. The evaluation model for arc fluctuations of triple-electrode fillet welding was established based on the characteristic parameters and their variation coefficients. This model indicated that variation coefficients could reflect arc voltage flnctuations of welding process, and its analysis result was consistent with the actual welding process.

Experimental study on the shear strength of side fillet weld of Q235B steel post high temperatures

In order to learn the variation laws of shear strength of side fillet weld post high temperatures, the tension tests were conducted after the double-strapped side fillet welded joints which were cooled down from different high temperatures with different cooling patterns. The tests indicate that specimens appear brittle fracture at the side fillet weld during the tension tests after cooling down. The fracture su（face is located in the welding throat. The maximum temperatures undergone and the cooling pattern are major factors influencing shear strength of side fillet welded joint post high temperatures. The shear strength reduces by 24% at most within 900 ~C. Based on the experimental results, the calculation formulas of shear strength of side fillet weld post high temperatures were proposed. Conclusions supply references for evaluation damage and reinforcement of steel structure post fire.

Experimental and Finite Element Analysis of a T-Joint Welding

This paper presents the Finite Element （FE） modeling of a two-seam welding process for a T-joint with a V chamfer preparation： The aim of the model is to predict the deformations, distortions and residual stresses resulting from the welding of the plates and experiments have been carried out in order to compare to the FE model. The ＂birth and death＂ method is used in ANSYS to simulate the filler metal deposition and the heat generation and weld pool simulation are conducted accordingly with the double ellipsoid configuration as proposed by Goldak et al. The model takes into consideration the temperature dependent non-linear material properties and uses a new formulation to compute the temperature dependent combined coefficient of heat loss. Improvements in the calculation are achieved by combining two types of meshing. The FE simulation is divided into two consecutive parts： the thermal simulation followed by the structural simulation. The results of the numerical model are compared to experiments.

THE EXACT SOLUTION OF STRESS DISTRIBUTION IN FILLET WELDS

The exact solution of stress distribution in fillet welds under the action of bending moment M is presented in this paper. Together with the exact solution of stress distribution in fillet welds under the action of concentrated force P given in an earlier paper([1]), designers of weldments can improve their work on the foundation of exact analytical solutions.

Reduction of Undercuts in Fillet Welded Joints Using Taguchi Optimization Method

This project work focuses on the reduction of weld undercuts using the Taguchi method. The phenomenon of weld undercuts constitutes a major problem for the welding industry. When undercuts occur, and particularly when such cuts are deep, it has a negative impact on the weld as it lowers the integrity and quality of the weldment. Therefore, efforts are made globally to reduce the depth of such weld undercuts to the barest minimum. Several optimization methods have been adopted;however, in this study, the Taguchi method is applied. “The smaller the better components” of the Taguchi method is applied. From the results obtained from applying this Taguchi method, the optimum process parameters obtained are A2-B1-C2, which are a voltage of 20 V, a current of 180 A, and a welding speed of 130 mm/s, required to form an undercut of 0.03 mm. Whereas the existing process parameters used by the company are A1-B3-C, which make an undercut to a depth of 0.09 mm. It is concluded that the use of Taguchi method has been able to reduce the depth of undercut as shown in this study. A step-by-step approach is presented in the study.

Numerical analysis of temperature profile and weld dimensions in laser ＋ GMAW hybrid welding of aluminum alloy T-joint

The temperature fields in the transient state and weld dimensions in laser ＋ gas metal arc welding （GMAW） hybrid welding of aluminum alloy T-joint for different welding conditions were calculated using the developed heat source model, and the effect of welding speed on them was analyzed. The results show that the temperature field for the first weld pass only shows the feature of GMAW and the one for the second weld pass has the characteristics of both laser welding and GMAW. Welding speed can affect greatly weld dimensions and temperature distribution. When welding speed reaches 3.5 m/min, the fusion zones of two weld passes are separated and the maximum peak temperature of thermal cycle on the workpiece surface decreases largely.

Calculation of the Strengths of Jointswith Fillet Welds in Welded Structure

In the paper, the finite element method (FEM) , engineering calculationmethod (ECM) and empirical fromular method (EFM) were used to calculatethe strengths of fillet joints in an Al-alloy vehicle. The results obtained withdifferent calculation methods were analysed, and then each method wasreviewed and assessed. FEM is accurate, but complicated, and its results haveno strength reserve; ECM and EFM are simple and convenient, butconservative.

熔盐罐罐底角焊缝疲劳可靠性评估方法及应用

为了准确评估熔盐罐罐底角焊缝服役过程中的疲劳可靠性,将应力影响因素和疲劳模型参数随机化,提出了一种基于应力-强度干涉理论的角焊缝疲劳可靠性评估方法。通过雨流计数法获得典型的熔盐液位变化幅值并统计其出现频率;建立了真实尺寸的角焊缝数值模型并获得其应力分布;基于角焊缝尺寸、载荷等应力影响因素的正态分布模型,应用拉丁超立方抽样方法对其抽样统计,从而获得角焊缝焊趾处等效结构应力的分布模型;对ASME BPVC.Ⅷ.2—2023标准中疲劳寿命模型的主应力-寿命曲线参数进行随机化,基于应力-强度干涉理论,建立了角焊缝疲劳可靠性评估模型;对某光热装置低温熔盐罐罐底角焊缝的疲劳可靠性进行实例分析。结果表明:一个季度内熔盐罐液位变化主要有6种典型工况,最大液位波动为1.55~12.39 m;角焊缝最大应力位于其内侧焊趾处,为301.5 MPa;多载荷下角焊缝的疲劳寿命均值为46 a,服役3 a后角焊缝的疲劳失效概率为0.040 6,服役30 a后的失效概率为0.335 9。

焊接方钢管T型节点的初始刚度分析

节点的初始转动刚度对构件之间的内力分布影响显著,然而现有计算角焊缝焊接方钢管T型节点初始转动刚度的组件法并未考虑角焊缝的影响,造成对初始转动刚度的低估。本文基于原始组件法,提出修正组件法来计算该类节点的初始转动刚度,重点考虑角焊缝尺寸的影响,并将修正组件法与原始组件法和试验进行对比以验证其可靠性。结果表明:本研究提出的修正组件法计算得到的节点初始转动刚度与试验中节点初始转动刚度之比的平均值为0.997,协方差为0.013;对于原始组件法,节点初始转动刚度的计算值与试验值之比的平均值为0.679,协方差为0.016。本文提出的修正组件法比较精确,且与原始组件法相比具有更佳的预测性能。

6063/6082铝合金焊接裂纹分析及其填丝焊改善

以6063/6082铝合金板为母材,采用环形光斑激光设备进行激光对接焊接,研究了焊接功率、焊接速度对6063/6082铝合金焊接裂纹的影响,采用填丝焊工艺对焊接裂纹进行了改善。结果表明:对于激光自熔焊,随着焊接功率的增加,焊接裂纹呈先减少后增加的特点,焊接功率>4800W后,熔合区、焊缝中心区均出现了大量河流状裂纹;随着焊接速度的增加,焊接裂纹明显增加,且尺寸变大,裂纹主要分布在熔合区及热影响区。当焊接功率为4400W、焊接速度为50mm/s时,焊缝裂纹相对较少,但无法完全消除。填丝焊工艺对6063/6082铝合金焊接裂纹起到了很好的抑制作用,同时提高了焊缝力学性能。添加ER5183焊丝的焊缝成形优异,未发现明显裂纹存在,焊缝剪切力达11260N,较自熔焊焊缝剪切力(8560N)提高了31.5%。填丝焊工艺抑制焊接裂纹形成的主要机制为降低焊缝冷却速度、调控焊缝Mg、Si元素含量、改善焊缝共晶组织的形态及分布。

大直径钢管加劲环角焊缝高效焊接技术

珠江三角洲水资源配置工程A2、A3标段DN4800内衬钢管制造安装工程量约7万t,内衬钢管外壁每间隔1.2 m设两道加劲环,加劲环与钢管对接焊缝采双面满焊,焊接工程量大,依托目前采用的单丝埋弧焊焊接工艺为比较对象,结合大直径钢管加劲环的结构分布、焊缝要求开展研究,通过设备的集成化、自动化,使单个焊接人员能实现双面及两道加劲环同时焊接,在满足焊角尺寸及质量的情况下,每12 m标准管段加劲环角焊缝焊接完成时间不超过8 h,达到高效焊接的目的。

基于Sysweld的焊接接头热源模型二次开发

焊接接头的结构形式和尺寸精度直接影响热源模型计算结果的准确性,工程实际应用的焊接接头形式多样、结构复杂, Sysweld内置的焊接接头远不能满足实际需求。基于Hypermesh, Sysweld软件平台开发了大坡口角焊缝和双侧多层角焊缝热源模型,首先利用Hypermesh建立有限元模型生成可执行的内嵌文件,利用Sysweld的HSF工具反复调整双椭球热源高斯参数,并将校核结果与试验结果进行比对,得到了应用于工程实际的自定义焊接接头热源模型。文中丰富了Sysweld软件的热源模型数据库,为不同接头形式热源模型的开发提供了技术支持。