NUMERICAL-ANALYSIS OF A RAILROAD BOLT HOLE FRACTURE PROBLEM

A finite element beam model was used to study the effects of joint bar looseness, rail height mismatch and train speed on the crack driving force for a crack emanating from a bolt hole in the web of a railroad rail. The model accounts for looseness by simulating gaps of varying sizes between rail and joint bars, while the effects of height mismatch were simulated by imposing an impulse to the end of one rail and using modal analysis to determine rail forces. The analysis shows that the crack driving force increases by about 25% as the joint loosens, primarily due to the increase in dynamic wheel load. The results also indicate that a rail height mismatch of 0.25 in. could cause fracture at train speeds as low as 10 mph, if the toughness of the rail steel is low.