Occupied Volume Integrity Testing : Elastic Test Results and Analyses
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2011-09-21
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Abstract:Federal Railroad Administration (FRA) and the Volpe Center have been conducting research into developing an alternative method of demonstrating occupied volume integrity (OVI) through a combination of testing and analysis. Previous works have been published on a series of full-scale, quasi-static tests intended to examine the load path through the occupant volume of passenger cars equipped with crash energy management (CEM) systems. This paper reports on the progress of the testing and analysis programs.
In January, 2011, an 800,000 pound conventional buff strength test was performed on Budd Pioneer 244. This test featured arrays of vertical, lateral, and longitudinal displacement transducers to better distinguish between the deformation modes and rigid body motions of the passenger car. Pre-test car repairs included straightening a dent in one side sill and installing patches over cracks found in the side sills. Additionally, lateral restraints were added to the test frame due to concerns in previous tests associated with lateral shift in the frame. As a part of this testing program, a future test of a passenger car is planned to examine an alternative load path through the occupied volume. In the case of Pioneer 244, this load path shares load between the floor and roof energy absorber support structures. Loading the occupant volume in this manner more closely simulates the loading the car would experience during a collision.
Finite element (FE) analysis was used in conjunction with full-scale testing in this research effort. An FE model of the Pioneer car was constructed and the 800-kip test was analyzed. The 800-kip test results were then compared to the analysis results and the model was adjusted post-test so that satisfactory agreement was reached between the test and the model. In particular, the boundary conditions at the loading and reaction locations required careful attention to appropriately simulate the support conditions in the test. Because the 800-kip load was applied at the line-of-draft, this test results in significant bending as well as axial load on the car. To ensure that both the axial and bending behaviors are captured in the model, the key results that were compared between test and model are the longitudinal force-displacement behavior and the vertical deflections at various points along the car. The post-test model exhibited good agreement with the compared test results. The validated model will be used to examine the behavior of the occupant volume when loaded along the alternative load path.
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