CTLGroup was contracted to conduct qualification tests on truck bolsters for freight car applications in the North American market. Bolster were tested in accordance to the Association of American Railroads specifications (AAR) Manual of Standard and Recommended Standards (MSRP) M-202 “Truck Bolsters, Cast or Structural – Design and Testing”.
The objectives of the tests were to evaluate the structural strength and durability of the truck bolsters manufacturing quality and design. Castings were subjected to static loads and fatigue loads in accordance to the AAR standards. Typically, three bolsters are subjected to fatigue loads and two are subjected to static loads per the AAR standard.
Each bolster was subjected to three fatigue block load cycles which consist of side bearing rock, center bowl edge bounce, and center bowl vertical bounce. The block load cycles represent elevated in service loads. The block loads for the first three fatigue scenarios sum to a total of 100,000 cycles. The fatigue block loads cycles were repeated until bolsters accumulate 700,000. The bolsters were periodically visually inspected for crack indications throughout the duration of the fatigue testing.
Bolsters were also subjected to transverse and vertical static tests. The static tests load cases represent overload scenarios to ensure castings do not have an excess of permanent deflection and can sustain an ultimate load.