Technical Reports

Extended NUCARS Safety Assessment

  • 01
  • Jun
  • 1992
AUTHOR: Nicholas G. Wilson
SUBJECT: Safety Performance Measures
KEYWORDS: Vehicle Dynamics, Lightweight Cars, AAR Chapter XI Tests, Turnouts, Safety Performance
ABSTRACT: The Federal Railroad Administration (FRA) and Association of American Railroads (AAR) sponsored research to evaluate the ability of the NUCARS vehicle dynamics simulation program to extrapolate results from Chapter XI tests to permit definition of the safe operating limits of car performance up to the point of derailment and to simulate test regimes in addition to the requirements of Chapter XI. The program involved subjecting a lightweight aluminum coal gondola to on-track tests, and simulation of tests using a computer model for new regimes beyond those required by Chapter XI. Five new test regimes are evaluated using on-track tests and computer simulations. These include combined lateral and cross level perturbations, a single lateral perturbation, limiting spiral, No. 10 turnout and a crossover. The test results and model predictions show that Chapter XI safety criteria were exceeded in several of the test regimes. Predictions extend the test results up to the point of derailment for several of the test regimes. The same computer model and test vehicle were used as in the joint FRA-AAR "Safety Aspects of New Trucks and Lightweight Cars, Car 2” research program. Following the recommendations of that test program, small improvements were made to the computer simulations. Good correlation between test and model predictions is shown only for the loaded car. The instrumented wheel sets used during the track tests were found to be too inaccurate for testing the empty car. Similar problems were encountered in the Car 2 project. The Car 2 project recommended improving the simulation of the friction damping of the car’s suspension. This is reiterated here.