考虑短裂纹阶段的焊接结构疲劳寿命分析
|
摘要
针对焊接结构可能存在的短裂纹问题,基于断裂力学原理提出一种改进的疲劳寿命预测方法。该方法结合Kitagawa-Takahashi图建立裂纹扩展门槛值ΔKth与裂纹特征尺寸a的函数关系,并在传统Paris模型的基础上考虑了该门槛值对裂纹扩展的影响。参照某起重机走行梁的疲劳试验数据进行对比研究,结果表明,本文提出的模型相较于传统的Paris模型具有更高的预测精度,而且它在一定程度上可以解释材料微观晶粒尺寸不同导致的焊接结构疲劳寿命的分散性;短裂纹阶段在试件梁疲劳总寿命中占比约为22%,0.25mm可作为短裂纹和长裂纹的合理分界点。
With the possible short cracks in welded structures considered,an improved fatigue life prediction method based on fracture mechanics was developed.Kitagawa-Takahashi diagram was used to construct the functional relationship between crack propagation thresholdΔKthand crack characteristic size a,which was then introduced into traditional Paris model to describe the influence ofΔKthon crack propagation.According to the fatigue testing results of crane girders from another research paper,comparative studies were carried out.The results show that the proposed model has better accuracy than Paris model and it can help to explain the fatigue life dispersion of welded structures due to the difference of material microscopic grain size.In addition,the life of short cracks accounts for about 22% of the total fatigue life of the specimens,and 0.25 mm is the reasonable critical point between short and long cracks.
With the possible short cracks in welded structures considered,an improved fatigue life prediction method based on fracture mechanics was developed.Kitagawa-Takahashi diagram was used to construct the functional relationship between crack propagation thresholdΔKthand crack characteristic size a,which was then introduced into traditional Paris model to describe the influence ofΔKthon crack propagation.According to the fatigue testing results of crane girders from another research paper,comparative studies were carried out.The results show that the proposed model has better accuracy than Paris model and it can help to explain the fatigue life dispersion of welded structures due to the difference of material microscopic grain size.In addition,the life of short cracks accounts for about 22% of the total fatigue life of the specimens,and 0.25 mm is the reasonable critical point between short and long cracks.
引文
[1]Bruder T,St9rzel K,Baumgartner J,et al.Evaluation of nominal and local stress based approaches for the fatigue assessment of seam welds[J].International Journal of Fatigue,2012,34(1):86-102.
[2]Zerbst U,Ainsworth R A,Beier H Th,et al.Review on fracture and crack propagation in weldments:a fracture mechanics perspective[J].Engineering Fracture Mechanics,2014,132(2):200-276.
[3]Baik B,Yamada K,Ishikawa T.Fatigue crack propagation analysis for welded joint subjected to bending[J].International Journal of Fatigue,2011,33(5):746-758.
[4]徐格宁,范小宁,陆凤仪,等.起重机焊接箱形梁疲劳可靠度及初始裂纹的蒙特卡罗仿真[J].机械工程学报,2011,47(20):41-44.
[5]Zhang Y H,Maddox S J.Fatigue life prediction for toe ground welded joints[J].International Journal of Fatigue,2009,31(7):1124-1136.
[6]Ngoula D T,Beier H Th,Vormwald M.Fatigue crack growth in cruciform welded joints:influence of residual stresses and of the weld toe geometry[J].International Journal of Fatigue,2017,101:253-262.
[7]魏国前,岳旭东,党章,等.结合S-N曲线和断裂力学的焊接结构疲劳寿命分析[J].焊接学报,2017,38(2):23-27.
[8]Geathers J,Torbet C J,Jones J W,et al.Investigating environmental effects on small fatigue crack growth in Ti-6242Susing combined ultrasonic fatigue and scanning electron microscopy[J].International Journal of Fatigue,2015,70:154-162.
[9]Lorenzino P,Navarro A.Growth of very long“short cracks”initiated at holes[J].International Journal of Fatigue,2015,71:64-74.
[10]Alfredsson B,berg M,Lai J.Propagation of physically short cracks in a bainitic high strength bearing steel due to fatigue load[J].International Journal of Fatigue,2016,90:166-180.
[11]Chapetti M D.Prediction of the fatigue limit of blunt-notched components[J].International Journal of Fatigue,2001,23(1):S171-S176.
[12]Luk P,Klesnil M.Transient effects in fatigue crack propagation[J].Engineering Fracture Mechanics,1976,8(4):621-629.
[13]Bowness D,Lee M M K.Prediction of weld toe magnification factors for semi-elliptical cracks in T-butt joints[J].International Journal of Fatigue,2000,22(5):369-387.
[14]Tong X L,Tuan C Y,Yang J P,et al.Fatigue strength of end-coped crane runway girders[J].Journal of Structural Engineering,2007,133(12):1783-1791.
[2]Zerbst U,Ainsworth R A,Beier H Th,et al.Review on fracture and crack propagation in weldments:a fracture mechanics perspective[J].Engineering Fracture Mechanics,2014,132(2):200-276.
[3]Baik B,Yamada K,Ishikawa T.Fatigue crack propagation analysis for welded joint subjected to bending[J].International Journal of Fatigue,2011,33(5):746-758.
[4]徐格宁,范小宁,陆凤仪,等.起重机焊接箱形梁疲劳可靠度及初始裂纹的蒙特卡罗仿真[J].机械工程学报,2011,47(20):41-44.
[5]Zhang Y H,Maddox S J.Fatigue life prediction for toe ground welded joints[J].International Journal of Fatigue,2009,31(7):1124-1136.
[6]Ngoula D T,Beier H Th,Vormwald M.Fatigue crack growth in cruciform welded joints:influence of residual stresses and of the weld toe geometry[J].International Journal of Fatigue,2017,101:253-262.
[7]魏国前,岳旭东,党章,等.结合S-N曲线和断裂力学的焊接结构疲劳寿命分析[J].焊接学报,2017,38(2):23-27.
[8]Geathers J,Torbet C J,Jones J W,et al.Investigating environmental effects on small fatigue crack growth in Ti-6242Susing combined ultrasonic fatigue and scanning electron microscopy[J].International Journal of Fatigue,2015,70:154-162.
[9]Lorenzino P,Navarro A.Growth of very long“short cracks”initiated at holes[J].International Journal of Fatigue,2015,71:64-74.
[10]Alfredsson B,berg M,Lai J.Propagation of physically short cracks in a bainitic high strength bearing steel due to fatigue load[J].International Journal of Fatigue,2016,90:166-180.
[11]Chapetti M D.Prediction of the fatigue limit of blunt-notched components[J].International Journal of Fatigue,2001,23(1):S171-S176.
[12]Luk P,Klesnil M.Transient effects in fatigue crack propagation[J].Engineering Fracture Mechanics,1976,8(4):621-629.
[13]Bowness D,Lee M M K.Prediction of weld toe magnification factors for semi-elliptical cracks in T-butt joints[J].International Journal of Fatigue,2000,22(5):369-387.
[14]Tong X L,Tuan C Y,Yang J P,et al.Fatigue strength of end-coped crane runway girders[J].Journal of Structural Engineering,2007,133(12):1783-1791.