基于均方差应力修匀的大横梁焊缝疲劳损伤评估
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摘要
针对C80E型通用敞车车体大横梁焊缝在运用过程中出现的疲劳裂纹问题,本文提出了一种基于均方差加权应力修匀的疲劳损伤评估方法。根据车体结构对称性,建立了1/4车体模型并进行有限元仿真,采用均方差加权应力修匀法对大横梁焊缝结点应力进行修匀;分别计算修匀后的应力值与结点应力均值、最大值在大秦线实测载荷谱下的疲劳损伤,并与实测线路应力谱对应的疲劳损伤进行对比分析。结果表明:经均方差应力修匀对应的疲劳损伤与实测损伤基本一致;与传统采用的均方差应力修匀方法获取的结点应力方法相比,结点应力均值或最大值精度更高,可提高结构疲劳损伤评估的准确性,且该方法简单,便于应用。
To solve the fatigue crack problem of the weld joint of the cross bearer of a C80E gondola car body,a fatigue damage assessment method based on mean square deviation weighted stress smoothing is proposed in this paper. According to the symmetry of the gondola car body,a 1/4 car body model was established for finite element simulation,and the mean square deviation weighted method was adopted to smoothen the weld joint stress of the cross bearer. Then,the value of fatigue damage of the smoothed stress,the node stress mean value,and the maximum value under the measured load spectrum of Da-Qin line were calculated and then compared and analyzed with the fatigue damage corresponding to the measured line's stress spectrum. The results show that the fatigue damage after mean square deviation weighted stress smoothing was basically consistent with the measured fatigue damage.This indicates that the accuracy of nodal stress obtained by the proposed method is higher than that obtained by the traditional methods of mean stress or maximum stress of the node; thus,the proposed method improves accuracy of structural fatigue damage assessment. Furthermore,this method is simple and easy to apply.
To solve the fatigue crack problem of the weld joint of the cross bearer of a C80E gondola car body,a fatigue damage assessment method based on mean square deviation weighted stress smoothing is proposed in this paper. According to the symmetry of the gondola car body,a 1/4 car body model was established for finite element simulation,and the mean square deviation weighted method was adopted to smoothen the weld joint stress of the cross bearer. Then,the value of fatigue damage of the smoothed stress,the node stress mean value,and the maximum value under the measured load spectrum of Da-Qin line were calculated and then compared and analyzed with the fatigue damage corresponding to the measured line's stress spectrum. The results show that the fatigue damage after mean square deviation weighted stress smoothing was basically consistent with the measured fatigue damage.This indicates that the accuracy of nodal stress obtained by the proposed method is higher than that obtained by the traditional methods of mean stress or maximum stress of the node; thus,the proposed method improves accuracy of structural fatigue damage assessment. Furthermore,this method is simple and easy to apply.
引文
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[15]王勖成.有限单元法[M].北京:清华大学出版社,2003.WANG Xucheng.Finite element method[M].Beijing:Tsinghua University Press,2003.
[2]British Standard Institute.BS 7608:2014+A1:2015,Guide to fatigue design and assessment of steel products[S].London:BSI,2015.
[3]British Standard Institute.BS EN 1993-1-9:2005,Eurocode 3:design of steel structures[S].London:BSI,2005.
[4]YILDIRIM H C.Recent results on fatigue strength improvement of high-strength steel welded joints[J].International journal of fatigue,2017,101:408-420.
[5]LU Yaohui,XIANG Penglin,DONG P,et al.Analysis of the effects of vibration modes on fatigue damage in highspeed train bogie frames[J].Engineering failure analysis,2018,89:222-241.
[6]HAN J W,KIM J D,SONG S Y.Fatigue strength evaluation of a bogie frame for urban maglev train with fatigue test on full-scale test rig[J].Engineering failure analysis,2013,31:412-420.
[7]李凡松,邬平波,曾京,等.构架三种常用疲劳强度校核方法对比研究[J].机械工程学报,2014,50(14):170-176.LI Fansong,WU Pingbo,ZENG Jing,et al.Study on the differences between the three common fatigue strength analysis methods for bogie frame[J].Journal of mechanical engineering,2014,50(14):170-176.
[8]MADYIRA D M,KUMBAA T,KAYMAKCIA A.Influence of manufacturing conditions on fatigue life of welded joints[J].Procedia manufacturing,2017,8:665-672.
[9]朱伯芳.有限单元法原理与应用[M].4版.北京:中国水利水电出版社,2018.ZHU Bofang.Finite element method theory and applications[M].4th ed.Beijing:China Water&Power Press,2018.
[10]李涛,左正兴,廖日东.结构仿真高精度有限元网格划分方法[J].机械工程学报,2009,45(6):304-308.LI Tao,ZUO Zhengxing,LIAO Ridong.Meshing method of high precision fem in structural simulations[J].Chinese journal of mechanical engineering,2009,45(6):304-308.
[11]LAI Yukun,MARTIN R R.Vertex location optimisation for improved remeshing[J].Graphical models,2012,74(4):233-243.
[12]PENG X,KULASEGARAM S,WU S C,et al.An extended finite element method(XFEM)for linear elastic fracture with smooth nodal stress[J].Computers&structures,2017,179:48-63.
[13]IVIRMA L,VERGARA M,PROVENZANO S,et al.Artificial neural networks application for stress smoothing in hexaedrons[J].WSEAS transactions on information science and applications,2009,6(5):872-883.
[14]徐小明,张盛,姚伟岸,等.基于辛弹性力学解析本征函数的有限元应力磨平方法[J].计算力学学报,2012,29(4):511-516.XU Xiaoming,ZHANG Sheng,YAO Weian,et al.Astress recovery method based on the analytical eigenfunctions of symplectic elasticity[J].Chinese journal of computational mechanics,2012,29(4):511-516.
[15]王勖成.有限单元法[M].北京:清华大学出版社,2003.WANG Xucheng.Finite element method[M].Beijing:Tsinghua University Press,2003.