【摘 要】
：
Brittle fracture occurs frequently in rails and thermite welded joints,which intimidates the security and reliability of railway service.Railways in cold region
【机 构】
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Key Labotatory of Civil Engineering Safety and Durability of China Education Ministry,Department of
【基金项目】
：
This work was financially supported by the Research Foundation of the Ministry of Railways and Tsinghua University;国家自然科学基金
论文部分内容阅读
Brittle fracture occurs frequently in rails and thermite welded joints,which intimidates the security and reliability of railway service.Railways in cold regions,such as Qinghai-Tibet Railway,make the problem of brittle fracture ih rails even worse.A series of tests such as uniaxial tensile tests,Charpy impact tests,and three-point bending tests were carried out at low temperature to investigate the mechanical properties and fracture toughness of U71Mn and U75V rail steels and their thermite welds.Fracture micromechanisms were analyzed by scanning electron microscopy (SEM) on the fracture surfaces of the tested specimens.The ductility indices (percentage elongation after fracture and percentage reduction of area) and the toughness indices (Charpy impact energy Ak and plane-strain fracture toughness Kic) of the two kinds of rail steels and the corresponding thermite welds all decrease as the temperature decreases.The thermite welds are more critical to fracture than the rail steel base metals,as indicated by a higher yield-to-ultimate ratio and a much lower Charpy impact energy.U71Mn rail steel is relatively higher in toughness than U75V,as demonstrated by larger Ak and KIC values.Therefore,U71Mn rail steel and the corresponding thermite weld are recommended in railway construction and maintenance in cold regions.
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