Rail-Car Impact Tests With Steel Coil: Car Crush

Abstract

Two grade-crossing impact tests were conducted in June 2002 at the Federal Railroad Administration’s (FRA’s) Transportation Technology Center in Pueblo, Colorado as part of the FRA’s research into passenger equipment crashworthiness. In both of these tests a cab car moving at approximately 14 mph impacted a standing coil of steel supported by a frangible table. The coil was positioned such that the left-side corner post of the cab car sustained the brunt of the impact. The cars were instrumented to measure the accelerations of the carbody, the displacements of the suspensions, the displacements of the corner posts, and the strains in selected structural members. The coil was instrumented to measure its three-dimensional acceleration, including yaw, pitch, and roll. On-board and wayside high-speed film and video cameras were used to record the impact. On June 4, 2002 a cab car compliant with general industry practice circa 1999 was tested and on June 7, 2002 a cab car compliant with current FRA regulations and American Public Transportation Association (APTA) Standards and Recommended Practices for Rail Passenger Equipment was tested. The tests themselves were conducted in response to a recommendation from the APTA Passenger Rail Equipment Safety Standards (PRESS) Committee to measure the crashworthiness performance of alternative cab car end structures. During the test of the 1990’s design, the corner post failed, eliminating the survival space for the operator. During the test of the state-of-the-art design cab car, the corner post remained attached and deformed less than 9 inches, preserving space for the operator. Prior to the test, crush analyses were conducted to determine the force/crush characteristics of the two end structure designs, as well as their modes of deformation. Collision dynamics analyses were also conducted to determine the extent of crush and the gross motion of the car and coil. This paper describes the analysis of the crush behaviors of the two different end structure designs. A companion paper describes the results of the collision dynamics analyses. The crush of the cars was analyzed using detailed finite-element models. The impact end of each car was modeled, including approximately 1/4 of the length of the car. The back end of the cab car model was fixed, and its end structure was impacted by an initially moving cylinder with the same mass and dimensions as the steel coil used in the tests. Prior to the tests, runs were made with the models with and without material failure. This approach allowed calculation of an upper bound and a lower bound on the force/crush characteristics. The pre-test predictions of the analysis of the state-of-the art car including material failure very closely match the results of the test for the force/crush characteristic, strains at the measured locations, the geometry of the deformed structure, and the locations and extent of material failure. The pre-test predictions of the analysis of the 1990’s design also closely match the test measurements, however, the extent of material failure predicted was slightly less than observed in the test; failure of the corner post was predicted to occur at a speed of a 1.6 mph (approximately 10%) greater than the test speed. A more sophisticated implementation of the material failure modeling helped bring the model results into very close agreement with the test measurements.

Review of severe deformation recommended practice through analyses comparison of two cab car end frame designs

“…The same pre-test model was used for the prototype SOA design that is discussed in more detail in [15]. Figure 13 depicts a comparison of the deformation sequence observed in the full-scale grade crossing test with the predictions using the pre-test finite element model.…”

“…The grade crossing tests were designed to address the concern of operator vulnerability to bulk crushing resulting from offset/oblique collisions where the primary load resisting structure is the end frame design. Two grade crossing tests were conducted in June 2002 and in both tests a single cab car retrofitted with an end frame design impacted a steel coil resting on a frangible table at a nominal speed of 14 mph [13,15]. The 40,000 lbf steel coil was situated such that the coil impacted the corner post of the cab car above the end sill.…”

“…The discussion will start with the results from the prototype SOA end frame design. The performance of the corner post behavior to this impact loading condition is described in more detail in [13,15] and was summarized above . Therefore the corner post results will not be discussed further.…”

“…At the point of load application the 0.5 failure strain was used. The failure strain chosen was based upon the results from preand post-test analyses conducted in [13,15]. Excellent agreement was obtained with the locations where material failure was observed and predicted.…”