CALIBRATION OF RAILWAY TRACK FOR DYNAMIC LOADS. TRACK STRUCTURE RESEARCH II, TASK 2

This paper reports the findings of Task 2 of a rail fracture resistance research program which attempts to define rail critical dynamic fracture load as a function of rail defect size, location and orientation, rail size and metallurgy, ambient temperature and track stiffness. This was achieved through fracture resistance testing of 18 foot (5.5 m) long defective rails removed from service. The rails were placed in a 25 foot (7.6 m) half track bed located in a cold chamber. The dynamic loads were simultaneously measured using shear gauges located on the rail web and a 200 kip (889.6 kN) impact force transducer. The results show that dynamic calibration of web shear gauge circuits mounted on rail is necessary when they are used in monitoring dynamic loads. Higher wheel/rail impact force was produced by concrete tie track compared to wood tie track although the fastening system mitigated the rail head negative bending stress. The rail size was also important, as was the size of the hammer used in the testing. Axial force in rail due to thermal stresses did not change the track stiffness.