Technical Reports

Freight Car Fatigue Test on FAST

  • 01
  • Jul
  • 1980
AUTHOR: G. J. Moyar, J. E. Burns
OFFICE: RPD
REPORT NUMBER: FRA/TTC-80/04
SUBJECT: Facilities & Test Equipment, Evaluation
KEYWORDS: Fatigue Analysis Test, Stress Analysis, Structural Fixes, Freight Car Dynamics, Center Plates
ABSTRACT: As a result of observed cracks in the fabricated center sills of many freight cars in the FAST consist, a special Fatigue Analysis Test (FAT) was conducted on the FAST Track during August and September of 1978. This report provides an analysis of the static and dynamic strain data from a base case "uncracked" car, a "cracked" car, and four cars with various structural "fixes" at the critical lower body bolster/center sill region. Vertical strain ranges were found to be critically high in the relatively thin section fabricated center sill with corresponding maximum stress ranges exceeding 30,000 psi during some periods of FAST operation. The prediction of the base case freight car mileage to crack initiation based on measured strain is reasonably conservative relative to the minimum FAST mileage to the first crack detection. A ranking of the merit of the "fixes" based on an application of the Fatigue Life Analysis Program is given. The report concludes that the observed cracks were caused by many cycle's of critically high strain in the fabricated center sill section, and that a doubler plate appears to be the best fix. Also, the Fatigue Design Guidelines are reasonably conservative in predicting fatigue cracks. Recommendations are included to explore some residual uncertainties from the test and also structural analysis difficulties.

####