气动冲击作用下钢桥疲劳裂纹闭合深度影响因素研究

Research on Influencing Factors of Steel Bridge Fatigue Crack Closure Depth under Pneumatic Impact

针对气动冲击作用下钢桥裂纹闭合开展试验研究,以带人工裂纹平板试件为研究对象,考虑不同冲击方式、冲击参数、材料强度等因素下对裂纹闭合深度的影响.建立拉伸荷载作用下带扁平椭圆裂纹的扩展有限元模型,从应力强度因子的角度分析了不同裂纹闭合深度对裂纹扩展速率的影响.结果表明:三次冲击作用下,裂纹闭合表面较为平整且闭合深度更深.当裂纹宽度较小时,采用合理的冲击参数可获得较大的裂纹闭合深度,本次试验中,裂纹最大闭合深度可达2.0 mm.有限元结果显示,随着裂纹闭合深度增大,裂纹尖端应力强度因子大幅度下降,但增幅逐渐趋于平缓,从应力强度因子的角度表明了气动冲击作用对延缓裂纹扩展具有积极作用.

An experimental study was carried out on crack closure of steel bridges under pneumatic impact.A plate specimen with artificial crack was taken as the research object,and the effects of different impact modes,impact parameters,material strength and other factors on crack closure depth were considered.The finite element model of crack propagation with flat ellipse under tensile load was established,and the influence of different crack closure depth on crack propagation rate was analyzed based on stress intensity factor.The results show that the crack closure surface is relatively flat and the closure depth is deeper under three impacts.When the crack width is small,a larger crack closure depth can be obtained by adopting reasonable impact parameters,and the maximum crack closure depth in this test can reach 2.0 mm.The finite element results show that as the crack closure depth increases,the stress intensity factor at the crack tip decreases significantly,but the increase gradually tends to be flat.From the point of view of the stress intensity factor,it shows that the pneumatic impact has a positive effect on delaying the crack growth.