摘要
在面外变形或高应力幅下,传统止裂孔修复钢结构疲劳裂纹易出现裂纹穿孔发展(即裂纹二次萌生),导致疲劳加固效果不佳。提出了一种钢结构疲劳裂纹的冷扩止裂孔修复技术,其原理是通过芯棒对止裂孔进行冷扩以产生孔周残余压应力,降低孔周疲劳应力水平,达到延长疲劳寿命的目的。开展了冷扩止裂孔修复含Ⅰ型裂纹钢板的冷扩试验和疲劳试验,获得了止裂孔冷扩后孔周残余应变的分布规律,明晰了疲劳荷载作用下冷扩止裂孔孔周残余应变的演化规律,研究了冷扩率(0%、1%、2%)以及孔尖距(0、5、10 mm)对含Ⅰ型裂纹钢板疲劳性能的影响,揭示了冷扩止裂孔修复含Ⅰ型裂纹钢板的增寿机理。研究结果表明:同一孔尖距下,冷扩率越大,疲劳寿命提升幅度越大;提高冷扩率(不超过2%),可以扩大孔周残余压应力分布范围,提升残余压应力水平;增大孔尖距会削弱冷扩止裂孔修复效果;冷扩率为2%、孔尖距为0 mm时具有最大疲劳寿命,相较于孔尖距为0 mm的常规止裂孔试件,试件疲劳总寿命提升了50.82%。若继续增大冷扩率,其疲劳寿命将有望提高更多,提高幅度有待进一步研究。最后,提出了基于名义S-N曲线和疲劳缺口系数的冷扩止裂孔孔周疲劳裂纹萌生寿命预测方法。分析表明:在双对数坐标系下预测值与试验值吻合较好,孔尖距为0 mm时,误差在±5%以内;孔尖距为5 mm和10 mm时,误差在±20%以内。
Under out-of-plane deformation or high fatigue stresses,conventional crack-stop hole repair of fatigue cracks in steel structures is susceptible to crack perforation(i.e.,secondary crack initiation),thereby resulting in unsatisfactory fatigue strengthening.This study proposes cold-expanded crack-stop hole technology for repairing fatigue cracks in steel structures.This principle involves a cold-expanded crack-stop hole using a mandrel to induce residual compressive stress around the hole,thereby reducing the fatigue stress level and extending the fatigue life.Cold expansion tests of crack-stop holes and fatigue tests were conducted on steel plates with typeⅠcracks.The distributions of residual strain around the hole after cold expansion were obtained,and the evolution of the residual strains during fatigue loading was clarified.The effects of cold expansion rates(0%,1%,and 2%)and hole-to-crack tip distances(0,5,and 10 mm)on the fatigue performance of steel plates with typeⅠcracks were investigated,and the life-extending mechanisms for the cold-expanded crack-stop holes were revealed.The results indicate that,for a specified hole-to-crack tip distance,increasing the cold expansion rate can enhance the fatigue life.Increasing the cold expansion rate(not exceeding 2%)can extend the distribution range and value of residual compressive stress around the cold-expanded crack-stop holes.Increasing the hole-to-crack tip distance reduces the improvement of fatigue life by cold-expanded crack-stop holes.The maximum fatigue life can be obtained when the cold expansion rate and the hole-to-crack tip distance are 2%and 0 mm,respectively;Compared with the case of conventional crack-stop hole specimens with a hole-to-crack tip distance of 0 mm,the total fatigue life of the specimens increased by 50.82%.Further increasing the cold expansion rate may potentially enhance the fatigue life,which needs more studies.Finally,a model for predicting the initiation life of fatigue cracks around cold expanded crack-stop holes based on n
作者
柯璐
李友林
李传习
陈正
陈爱龙
冯鹏
KE Lu;LI You-lin;LI Chuan-xi;CHEN Zheng;CHEN Ai-long;FENG Peng(College of Civil Engineering and Architecture,Guangxi University,Nanning 530004,Guangxi,China;State Key Laboratory of Featured Metal Materials and Life-cycle Safety for Composite Structures,Guangxi University,Nanning 530004,Guangxi,China;Department of Civil Engineering,Tsinghua University,Beijing 100084,China)
出处
《中国公路学报》
EI
CAS
CSCD
北大核心
2024年第11期76-88,共13页
China Journal of Highway and Transport
基金
国家重点研发计划项目(2021YFB2600900)
广西科技重大专项(桂科AA23073017)。
关键词
桥梁工程
钢结构
疲劳性能试验
冷扩止裂孔
残余应力
疲劳加固
bridge engineering
steel structures
fatigue performance test
cold-expanded crack-stop hole
residual stress
fatigue strengthening
