Mechanical & Materials Engineering, Department of


Date of this Version



A dissertation presented to the faculty of the graduate college at the University of Nebraska in partial fulfillment of requirements for the degree of Doctor of Philosophy. Major: Engineering (Mechanical Engineering). Under the Supervision of Professor Shane M. Farritor. Lincoln, Nebraska: December, 2008. Copyright © 2008 Sheng Lu.


Track quality is a major factor in railroad safety, and one accepted indicator of track quality is the vertical track deflection. Measuring track deflection from a moving railcar is difficult because there is no stable reference for the measurements. A system developed by researchers at the University of Nebraska to measure track deflection from a moving railcar in real-time is described in detail. The system consists of a loaded hopper with a camera/laser sensor system to detect the vertical deflection of the rail relative to the wheel/rail contact point. Modeling and simulation of the system is also presented along with the mathematical models which can be used to estimate track modulus. The measurement system has been used to conduct revenue service tests over three thousand miles of track. A special validation test was also performed. The results from these tests have shown that the system’s measurement is repeatable and accurate; the system has notable ability to indicate track support problems.