对接接头缺口应力集中系数不确定性分析

Uncertainty analysis of notch stress concentration factors for welded butt joints

[目的]以典型对接接头为研究对象进行参数化建模,建立焊缝几何形状存在不确定性的有限元模型,来研究焊缝几何存在不确定性的对接接头焊趾处缺口应力集中系数K_(t),并统计分析其分布规律。[方法]首先,对以往采用的网格尺寸和单元类型进行改进,通过有限元网格敏感性分析,研究不同类型的单元以及网格尺寸对K_(t)的影响;其次,沿对接接头焊缝法向提取节点应力,通过绘制应力分布图,确定焊趾处最大应力集中所在部位;然后,通过引入控制点描述对接焊缝几何形状的变化来真实反映焊缝几何形状的不确定性,结合实际测量的焊缝形状数据的分布规律,随机抽样得到大量的焊缝几何参数数据;最后,基于缺口应力法计算K_(t),并对其进行统计分析,探究对接接头在焊缝几何参数存在不确定性时K_(t)的分布规律。[结果]结果表明,K_(t)的分布满足正态分布。[结论]通过探究焊趾处的应力分布,对于分析疲劳强度和提高疲劳寿命预测精度具有重要意义。

[Objectives]This paper focuses on parametric modeling of a typical butt joint and establishes a finite element model with uncertain geometry of the weld seam,aiming to investigate the stress concentration factor K_(t) at the weld toe of the butt joint with uncertain weld seam geometry and analyze its distribution characteristics.[Methods]Firstly,the mesh size and element type used in the past were improved,and the influence of different types of elements and mesh sizes on K_(t) is studied through finite element mesh sensitivity analysis.Nodal stresses are extracted along the welding direction of the butt joint,and the location of maximum stress concentration at the weld toe is determined by plotting the stress distribution.Then,the uncertainty of the weld seam geometry is accurately reflected by introducing control points to describe the variation of the weld seam geometry.Combined with the distribution pattern of the actual measured weld seam geometry data,a large amount of weld seam geometry parameter data are randomly sampled.Finally,K_(t) is calculated based on the notch stress method and its distribution was statistically analyzed to explore the distribution pattern of K_(t) when there is uncertainty in the weld seam geometry parameters of the butt joint.[Results]The results show that the distribution of K_(t) follows a normal distribution.[Conclusions]Exploring the stress distribution of welding toes has great significance for analyzing fatigue strength and improving the prediction accuracy of fatigue life.