基于多轴准则的货车车体疲劳寿命分析方法
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摘要
基于变幅应力循环的损伤等效恒幅应力计算方法和形状改变能密度理论,提出承受变幅循环,处于多轴应力状态下的结构的疲劳寿命分析方法。根据几何特征建立焊缝坐标系,计算节点在该坐标系下的应力分量,根据线路实测载荷谱获得节点应力谱;根据应力谱计算节点损伤等效恒幅应力,结合接头抗疲劳设计等级,计算节点材料利用度分量和综合材料利用度,评估结构在指定寿命下的疲劳强度。对敞车车体典型焊缝的疲劳强度进行评估,结果表明所研究焊缝的疲劳强度主要受正应力分量的影响,切应力对结构疲劳强度的影响较小。对比研究不同分析方法下的节点材料利用度特征,结果表明,当考察点具有显著的多轴应力特征时,依据AAR标准提供的方法和依据多轴应力法获得的结构疲劳强度评估结果间存在较大差异;依据多轴应力法进行评估时,所关注节点的材料利用度较采用AAR方法评估的结果小18.5%。采用多轴应力法评估疲劳强度有利于车体结构轻量化设计。
Based on the method of calculating the equivalent constant amplitude stress of the variable amplitude stress cycle and thevon_Mises theory, the fatigue life analysis method of the structure subjected to variable amplitude cycles and under multi-axial stressstate is proposed. The weld coordinate system is established according to geometric features, the stress components of nodes arecalculated in this system. The node's stress spectrum is obtained according to the road environment percent occurrence spectrum andits equivalent constant amplitude stress is also calculated. According to the joint fatigue resistance, the components of degree ofutilization and comprehensive degree of utilization are calculated to evaluate the structural fatigue strength under a specified life. Theevaluation of the fatigue strength of typical welds on gondola carbody shows that the fatigue strength of the studied welds is mainlyaffected by the normal stress component, and the shear stress has little effect on the structural fatigue strength. The comparison of thecharacteristics of node's degree of utilization under different analysis methods have shown that, when the observation points havesignificant multi-axial stress characteristics, there are large differences between the results obtained by the AAR standard and themulti-axial stress method. On the basis of the multi-axial stress method, the node's degree of utilization is 18.5% less than the AARmethod. The use of multi-axial stress method to evaluate the fatigue strength is beneficial to the lightweight design of the carbodystructure.
Based on the method of calculating the equivalent constant amplitude stress of the variable amplitude stress cycle and thevon_Mises theory, the fatigue life analysis method of the structure subjected to variable amplitude cycles and under multi-axial stressstate is proposed. The weld coordinate system is established according to geometric features, the stress components of nodes arecalculated in this system. The node's stress spectrum is obtained according to the road environment percent occurrence spectrum andits equivalent constant amplitude stress is also calculated. According to the joint fatigue resistance, the components of degree ofutilization and comprehensive degree of utilization are calculated to evaluate the structural fatigue strength under a specified life. Theevaluation of the fatigue strength of typical welds on gondola carbody shows that the fatigue strength of the studied welds is mainlyaffected by the normal stress component, and the shear stress has little effect on the structural fatigue strength. The comparison of thecharacteristics of node's degree of utilization under different analysis methods have shown that, when the observation points havesignificant multi-axial stress characteristics, there are large differences between the results obtained by the AAR standard and themulti-axial stress method. On the basis of the multi-axial stress method, the node's degree of utilization is 18.5% less than the AARmethod. The use of multi-axial stress method to evaluate the fatigue strength is beneficial to the lightweight design of the carbodystructure.
引文
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[12]European Committee for Standardization.EN 1993-1-9-2005 Eurocode 3:Design of steel structures-Part 1-9:Fatigue[S].Brussels:European Committee for Standardization,2005.
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[14]Forschungskuratorium Maschinenbau.Analytical strength assessment of components[M].6th ed.Frankfurt am Main:VDMA-Verlag GmbH,2012.
[15]安琪.高速动车组转向架柔性构架动态特性研究[D].成都:西南交通大学,2013.AN Qi.Research on the dynamic behavior of flexible frame on high-speed emu bogie[D].Chengdu:Southwest Jiaotong University,2013.
[16]SONSINO C.Multiaxial fatigue assessment of welded joints-Recommendations for design codes[J].International Journal of Fatigue,2009,31(1):173-187.
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[18]米彩盈.高速动力车承载结构疲劳强度工程方法研究[D].成都:西南交通大学,2006.MI Caiying.A study of project method for load bearing structure fatigue strength in power vehicle[D].Chengdu:Southwest Jiaotong University,2006.
[2]International Union of Railways.UIC 577-2012 Wagon stresses[S].Paris:International Union of Railways,2012.
[3]European Committee for Standardization.EN12663-2-2010 Railway applications-Structural requirements of railway vehicle bodies-Part 2:Freight wagons[S].Brussels:European Committee for Standardization,2010.
[4]Associations of American Railroads.MSRP-C-Ⅱ-2015Design,fabrication,and construction of freight cars[S].Washington D.C.:Associations of American Railroads,2015.
[5]赵方伟.铁路货车车体载荷谱测试及疲劳强度评价研究[D].北京:北京交通大学,2015.ZHAO Fangwei.Study on load spectrum test and fatigue strength evaluation of railway freight car body[D].Beijing:Beijing Jiaotong University,2015.
[6]郑小艳.5000吨编组C70敞车载荷谱测试及车体疲劳强度评价[D].北京:北京交通大学,2007.ZHENG Xiaoyan.5000t Marshalling C70 gondola car load spectrum test and fatigue strength evaluation of carbody[D].Beijing:Beijing Jiaotong University,2007.
[7]闫旭.大秦线20 000吨重载列车纵向载荷谱的编制[D].北京:北京交通大学,2009.YAN Xu.The compile of longitudinal load spectrum for Da-Qin Line 20 000-ton heavy-load train[D].Beijing:Beijing Jiaotong University,2009.
[8]杨大春.大秦线货车摇枕载荷谱编制及应用[D].北京:北京交通大学,2011.YANG Dachun.The compilation and application of the load spectrum of the bolster for freight car on Daqin Railway[D].Beijing:Beijing Jiaotong University,2011.
[9]李浩.C80B敞车扭转和侧滚载荷谱编制与应用[D].北京:北京交通大学,2010.LI Hao.C80B wagon’s lateral and torsional load spectrum’s compilation and application[D].Beijing:Beijing Jiaotong University,2010.
[10]赵方伟,谢基龙.小应力循环对C70E型车体疲劳损伤的影响研究[J].机械工程学报,2014,50(10):121-126.ZHAO Fangwei,XIE Jilong.Influence of small stress cycles on the fatigue damage of C70E car body[J].Journal of Mechanical Engineering,2014,50(10):121-126.
[11]李晓峰.基于虚拟疲劳试验的铁路车辆焊接结构疲劳寿命预测[D].大连:大连交通大学,2008.LI Xiaofeng.Predicting fatigue life of rail vehicle welded structure based on virtual fatigue test[D].Dalian:Dalian Jiaotong University,2008.
[12]European Committee for Standardization.EN 1993-1-9-2005 Eurocode 3:Design of steel structures-Part 1-9:Fatigue[S].Brussels:European Committee for Standardization,2005.
[13]HOBBACHER A.Recommendations for fatigue design of welded joints and components[M].Cham:Springer International Publishing Switzerland,2016.
[14]Forschungskuratorium Maschinenbau.Analytical strength assessment of components[M].6th ed.Frankfurt am Main:VDMA-Verlag GmbH,2012.
[15]安琪.高速动车组转向架柔性构架动态特性研究[D].成都:西南交通大学,2013.AN Qi.Research on the dynamic behavior of flexible frame on high-speed emu bogie[D].Chengdu:Southwest Jiaotong University,2013.
[16]SONSINO C.Multiaxial fatigue assessment of welded joints-Recommendations for design codes[J].International Journal of Fatigue,2009,31(1):173-187.
[17]BCKSTRM M.Multiaxial fatigue life assessment of welds based on nominal and hot spot stresses[D].Lappeenranta:Lappeenranta University of Technology,2003.
[18]米彩盈.高速动力车承载结构疲劳强度工程方法研究[D].成都:西南交通大学,2006.MI Caiying.A study of project method for load bearing structure fatigue strength in power vehicle[D].Chengdu:Southwest Jiaotong University,2006.
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