薄壁金属直缝圆焊管残余应力超声检测

为了研究小口径的薄壁金属直缝圆焊管焊接区域残余应力的大小,利用临界折射纵波对焊管焊接区域进行残余应力检测。结合静载拉伸实验标定了焊管的声弹性系数。结果表明,残余应力随着拉伸距离的增加而变大;拉伸距离相同时残余应力随着焊管直径的增大而增大;声弹性系数与焊管直径无关。通过与盲孔法检测实验的对比,结果表明了临界折射纵波检测残余应力是可靠的。     

薄壁铝合金结构焊接应力变形数值模拟

实际结构焊接过程的三维数值模拟因为计算量大而往往难以进行。为了采用三维热弹塑性有限元方法对薄 壁铝合金结构的焊接过程进行数值模拟,提出了粘贴单元和混和单元两种网格划分技术相结合的单元划分方案进 行有限元建模,通过薄板对接模型试验验证了此方案的可行性,并研究了不同建模方案对计算效率的影响。将这 种单元划分方案应用到实际薄壁筒体结构焊接过程的数值模拟中,对焊接过程产生的残余应力和变形进行了成功 地预测。结果表明:对于薄壁构件,采用粘贴单元和混合单元相结合的单元划分方案可以在保证一定精度的前提 下,可大大减少有限元网格划分工作量,同时可降低计算规模,提高计算效率。     

薄钢板激光焊接实验研究

通过对汽车用冷轧薄钢板的激光拼焊的实验研究表明,虽然激光焊接接头的塑性有所下降,但其焊接强度与母材相近,且其焊接影响区小,对汽车覆盖件和地板等零件的焊接具有较好的效果。     

残余应力作用下的航空整体结构件加工变形仿真

铝合金预拉伸板在成型过程中会产生较大的残余应力,在切削过程中毛坯的初始残余应力的释放对整体结构件的宏观变形有重要的影响。在弹塑性力学的基础上,综合运用Hypermesh和ABAQUS建立残余应力单因素作用下的三维铣削仿真加工变形场的有限元模型,利用生死单元技术模拟了材料的去除,分析了铝合金板材材料去除过程中残余应力释放引起的加工变形规律。并且运用Hypermesh提高了有限元前处理的速度,解决了复杂模型的残余应力加载困难与单元去除困难的问题。     

Numerical modelling of welding distortion redistribution due to the change of self-constraint in a T-joint welded structure

Finite element method (FEM) is a powerful tool for analysing the potential deformation during a material removal process. After the removal of material, re-establishment of equilibrium within the remaining part of the structure causes distortion due to the relief of residual stress in the removed materials. In this study, commercial FEM software (MSC.Marc) was used to simulate material removal, and the accuracy was evaluated by comparison with results from machining experiments. The effect of cutting height on the distortion redistribution and the kerf width in a T-joint welded structure is discussed, and the distortion differences at the centre line of the bottom were compared between the calculated and experimental results. The results demonstrate that the developed model is useful and efficient for simulating the redistribution of welding distortion due to material removal.

     

Investigations on welding residual stress and distortion in a cylinder assembly by means of a 3D finite element method and experiments

In the present work, both experimental and numerical simulation methods are used to investigate the characteristics of welding distortion and residual stress distribution. A 3D thermo-mechanical Finite Element Analysis (FEA) method is used to predict the welding distortion and residual stress of cylinder-shaped multi-pass layer weldments. Each weld pass is performed using a quarter-circle balanced welding procedure. To investigate the influence of deposition sequence and welding heat input on the welding distortion and residual stress, a continuous welding procedure is also calculated. The corresponding FEA models considered a moving heat source, the deposition sequence, and temperature-dependent thermal and mechanical properties. The results predicted by 3D FEA model are generally in good agreement with the measurements. Finally, the numerical and experimental results suggest that both deposition sequence and heat input affect welding distortion and residual stress distribution. Furthermore, the 3D thermal-mechanical FEA method can predict cylinder-type welding distortion.     

夹具拘束距离对Hastelloy C-276薄板脉冲激光焊接变形的影响

为了揭示夹具拘束距离对0.5mm厚Hastelloy C-276薄板脉冲激光焊接变形的影响,基于有限元软件ANSYS建立了三维热力耦合有限元模型。采用位移约束假设代替实际夹具的拘束作用,研究了夹具拘束距离对Hastelloy C-276薄板焊接纵向挠曲变形及横向收缩变形的影响规律。实验测量了焊接热循环曲线和残余变形,验证了所建立有限元模型的可靠性。模拟结果表明,随着夹具拘束距离从8mm增加到20mm,焊接纵向挠曲变形及横向收缩变形均表现为近似线性增大的趋势,特别是焊接横向收缩变形增加了将近3.6倍,而减小夹具拘束距离可以控制焊接残余变形。该模型较准确地模拟了薄板脉冲激光焊接温度场及残余变形,为抑制薄板焊接变形提供了理论和实验依据。     

Prediction of welding distortion in multipass girth-butt welded pipes of different wall thickness

For a full welded body ball valve, because the last working procedure is the weld, prior to welding, the welding distortion must be accurately predicted to provide preference for welded structure fabrication at the design stage in order to assure spool rotation, valve seal, and non-deformability in active service. Therefore, it is important to select an accurate and efficient method to predict welding distortion. In this study, the finite-element method based on the inherent strain theory was presented to simulate welding distortion in multipass girth-butt welded pipes of different wall thicknesses. For multipass welding, two weld passes at the same layer were combined. The axial distortion of each weld layer was calculated respectively and the radial distortion was calculated for one time. For multipass girth-butt welded pipes of different wall thicknesses, two methods were proposed to predict the axial distortion. The results calculated were compared and better method was confirmed.     

Experimental and finite element analysis of residual stress and distortion in GTA welding of modified 9Cr-1Mo steel

Journal of Mechanical Science and Technology - In this paper, investigation of residual stress and distortion induced in 3 mm thick Modified 9Cr-1Mo steel plates during GTA welding is carried out....     

焊接顺序对中厚板对接焊残余应力的影响

针对同种材料,但几何结构不同的中厚板结构件之间的对接焊,运用有限元软件进行模拟,分析多层多道焊各层焊缝的焊接顺序对焊缝区域横、纵向残余应力的影响。采用内生热的加载方式模拟热源,采用生死单元法模拟多层多道焊缝的焊接过程。模拟结果表明,从几何尺寸小的一边向几何尺寸大的一边焊,沿焊缝底部和顶部中心线方向产生的横纵向残余应力峰值最小;底层的几道焊缝的焊接顺序对焊缝底部和顶部中心线方向所产生的横纵向残余应力的影响不大。     

残余应力重分布引起的结构件铣削变形研究

航空铝合金结构件毛坯在成形过程中产生很大的残余应力,使得其在后续机械加工过程中极易发生翘曲变形,这已经成为国防武器快速开发和高效加工的瓶颈.采用有限元数值模拟技术,建立了航空铝合金板材残余应力释放引起加工变形的力学模型,分析了在7050T7451铝合金板材材料去除过程中残余应力释放引起的加工变形规律,并针对7050T7451隔框零件进行铣削加工变形实验研究,并与有限元模拟结果进行比较,验证了数值模拟结果具有较高的精确度.     

Fracture analysis of a welded front axle tube structure from a mini-truck

Journal of Mechanical Science and Technology - The failure (fracture) mechanism of a welded front axle tube structure made of C45E4 steel from a mini truck was analyzed. The fracture occurred on...     

Development of a welding residual stress predictor using a function-replacing hybrid system

Welding is a reliable and efficient metal-joining process widely used in industries. Residual stresses are inherent and detrimental in welded structures. Researchers have developed many direct measuring techniques for welding residual stress. Intelligent techniques have been developed to predict residual stresses to meet the demands of advanced manufacturing planning. The existing tools are limited in application and need attention. This research paper details the development and use of a function-replacing hybrid for predicting the residual stress in butt-welding.     

论焊接件变形的结构和工艺分析

焊接在制造业中的应用正在迅速发展,但焊接变形的不同程度制约着焊接产品的质量.论述在焊接生产中,如何防止和减少焊接变形,并在焊缝长短、焊缝大小、焊接形式、焊接面大小、焊接方法方面加以探索.     

焊接接头残余应力的计算机模拟

应用有限元方法，采用有限元分析软件ANSYS，用计算机模拟了焊接接头残余应力的大小和分布，模拟结果和实验结果比较吻合，证明了这种方法具有重要的实用价值。     

Characteristics of the residual stress distribution in welded tubular T-joints

Tubular T-joints are structural discontinuities that can be easily involved with stress concentrations. It is therefore necessary to estimate an internal stress distribution of T-joints. However, the complicated residual stresses are unavoidably produced adjacent to the joints by welding. In this paper, the residual stress distributions in welded tubular T-joints were analyzed by using a three-dimensional non-steady heat conduction analysis and a three-dimensional thermal elastic-plastic analysis. Characteristics of the residual stress distribution in welded tubular T-joints are investigated by the thermal-mechanical analysis results.     

Predicting residual stresses and distortion during multisequence welding of large size structures using FEM

A three-dimensional thermomechanical finite element (FE) analysis is carried out to model and predict the influence of welding sequence on the generation of distortions and residual stresses in large size T-joints. To simulate industrial welding conditions, the influence of nine welding sequences on the magnitude of distortion in both the plate and the stiffener was investigated. The addition of new material during welding was simulated using an element “birth and death” technique, while the moving welding arc was considered as a volumetric heat source with a double ellipsoidal distribution. The investigated material is a structural steel used for fabrication of large size structures in the hydroelectric industry. To calibrate the model and validate the simulation results, welding-induced distortion for one sequence was initially modeled and the results were compared with experimental measurements. The optimum welding sequences for the base plate and the reinforcement plate were determined. The results indicated also that the predicted distortions obtained from three-dimensional FE analysis are in reasonable agreement with experimental measurements.     

The calculation of welding residual stresses in thin steel plates

The welding stresses in a free plate are determined theoretically by treating the problem as one of two-dimensional elastoplastic thermal stress analysis. The governing equation of the problem is solved using a finite difference technique and plasticity effects are allowed for using the method of successive elastic solutions. The relationship between the weld shrinkage force and the heat input is studied and the effect of coincident two-pass welds is examined.     

3D finite element simulation of temperature distribution,residual stress and distortion on 304 stainless steel plates using GTA welding

In the present study, the distortion induced in rectangular plate of AISI 304 SS during autogenous GTA welding process is measured experimentally and further validated using Finite element (FE) analysis. The thermal histories are measured at fixed locations over the surface of the plate and the results are compared with FE analysis. The Gaussian surface and Volumetric heat source models are simulated and transient heat transfer analysis is performed. The heat source models have been tested with two different speeds. The effectiveness of change in thermal histories of the heat sources have been studied and reported. In FE analysis, the sequentially coupled thermomechanical analysis is performed using the thermal histories as input and the distortion of the plates are predicted and compared with experimental measurements. The large and small displacement theories are employed for the above purpose and the effectiveness of the theories are reported. The edge deformation of the plates have been measured and validated for both the theories. The residual stress and distortion at the mid span are predicted and discussed. The results predicted using large displacement theory is in good agreement with measured values.     

The effect of temperature alternating load on residual stresses for Al-Li alloy T-joints welded by dual laser beam bilateral synchronous welding

The International Journal of Advanced Manufacturing Technology - The finite element (FE) simulation is employed to predict the residual stresses, which is induced by the welding and the temperature...