Original Article The role of bending stress on the initiation of reverse transverse defects Soumyajit Mojumder 1,2,3 , Hang Su 3 , Cong Qiu 4 , Peter Mutton 4 , Aparna Singh 2 and Wenyi Yan 3 Abstract This paper investigated the role of longitudinal reverse bending stress on the initiation of reverse transverse defects. The longitudinal reverse bending stress occurs due to the reverse bending of the rail between two-wheel passage leading to the generation of tensile bending stress at the railhead and the lower head areas. The longitudinal bending stress was investigated as part of a parametric study on the rail cant angle, rail stiffness, lateral-to-vertical load ratio, and rail profile. A finite element model was created by using ABAQUS to analyze the extent of reverse bending in rails with respect to the chosen set of parameters. Under different lateral-to-vertical load ratios of 0, 0.3, 0.5, and 0.7, the maximum stress at the rail lower gauge corner was found to vary between 14.57 MPa and 15.47 MPa under the reverse bending condition. Similarly, low values of tensile stress under the reverse bending scenario were observed with changes in the rail cant angle and axle spacing with respect to different coal and iron ore wagons. The results revealed that the magnitude of the bending stress under different conditions of reverse bending was not significant enough to initiate a crack at the lower gauge corner. Keywords Reverse transverse defect, bending stress, finite element analysis, lower gauge corner, fatigue, rail, failure Date received: 25 July 2019; accepted: 3 January 2020 Introduction Railway transportation plays a significant role in global economic development. To meet the growing demands of customers, the rail industry is required to run longer and more frequent trains with higher axle loads, which in turn may affect the structural integrity of the rail. These trends have created additional chal- lenges for the rail operators to ensure safe operations of the railway network. Hence, it is considered neces- sary to understand the development of rail defects, which can be attributed to longitudinal bending stress. 1,2 Additional research suggested that the cyclic bend- ing stresses generated with regular train passage could contribute to crack initiation and propagation of the defects within the rail. 3–5 Jeong and Perlman 6,7 con- cluded that there might be several factors associated with the magnitude and location of the bending stress in the rail, including the rail type, rail support condi- tions, axle loads, etc. Some other studies 3,6,8–11 found transverse defects (TDs), which usually originate at the subsurface of the rail gauge side, as one of the significant factors. One of the most common TDs in continuously welded rails (CWR) is called detail frac- ture. 8,10 It has also been observed that TDs may not require a prior shelling defect for their initiation pro- cess. They are likely to directly initiate from the steel inclusions and grow in a transverse plane. Another crucial factor that has not been exten- sively researched is reverse transverse defects (RTDs), which are defects originating at the lower gauge corner of the railhead in specific high rail worn sections along curved rails. Longitudinal bend- ing stresses seem to have a major influence on the lower rail gauge corner in relation to RTDs. 3 This is exacerbated by the heavy axle loading conditions commonly seen in North American rail systems. 10,12 Such defects have been reported in heavily worn out 1 IITB-Monash Research Academy, IIT Bombay, Mumbai, India 2 Department of Metallurgical Engineering and Materials Science, IIT Bombay, Mumbai, India 3 Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC, Australia 4 Institute of Railway Technology, Monash University, Clayton, VIC, Australia Corresponding author: Wenyi Yan, Department of Mechanical and Aerospace Engineering, Monash University, Clayton, VIC 3800, Australia. Email: wenyi.yan@monash.edu Proc IMechE Part F: J Rail and Rapid Transit 0(0) 1–12 ! IMechE 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0954409720904329 journals.sagepub.com/home/pif