Railroad Freight Equipment Load Environment Testing

Freight equipment in interchange service on the North American Continent is called upon to tolerate extremes of operating conditions throughout a service life that can span four decades. Consequently, freight car design must consider not only short-term structural requirements, but also long-term fatigue behavior. The classical design approach has been to increase structural member size to decrease stresses, thereby avoiding both short-term and long-term failure. However, with the continued increase in freight car payload, with a corresponding limit on maximum permissible gross wheel load, has come the realization that more efficient design and more detailed analysis are required. Thus the addition of fatigue analysis to the freight car design procedure gives the industry a powerful and valuable tool. Proper utilization of this tool permits more efficient design of freight cars, as well as better and more realistic "fixes" for existing cars encountering premature failure problems. Recently the Mechanical Division of the Association of American Railroads adopted a fatigue analysis methodology for the calculation of expected fatigue life for freight cars and their components (1). This technique considers the anticipated load environment that the freight car is expected to experience as well as the material and structural properties of the components under investigation. This load environment must be representative of that experienced by a freight car operating in unlimited interchange service during the period of its full service life, which can be 1,000,000 miles (1) or 40 years (2). It is the purpose of this paper to describe the procedure for acquisition and analysis of the rail service environmental load data for use as the input for freight car fatigue design.
Freight Equipment, Car design, Fatigue analysis
Darien, N. J., & Zarembski, A. M., “Railroad Freight Equipment Load Environment Testing”, 25th International Instrumentation Symposium, Anaheim, CA, May 1979.