Insulated Railway Joint Design Methodology Through Parametric Finite Element Based Modeling

The Railroad Industry experiences multiple failures with currently used bonded insulated joint designs. These failures have encouraged an increased effort in strength and fatigue analysis for the joints. This paper presents a program initiated by Virginia Tech and Transportation Technology Center Incorporated (TTCI) to develop, analyze, and test a family of insulated joint designs featuring non-adhesive bolted connections. This program utilizes a hierarchical set of Finite Element (FE) parametric models that explore the problem’s mechanics for a family of rail joint design concepts by refining the analysis with each subsequent model. Currently, there is limited information concerning design criteria for insulated joints in the Railroad industry. Therefore, an initial task in this program is to define design criteria and representative load cases characteristic of typical life cycles for commercial freight rails. Design criteria are either proprietary to the railroad or do not appear to be published in the AREMA handbooks. However, the AREMA handbooks do define an acceptance test for the failure of rail joint. Failure criteria were derived from the AREMA rolling wheel acceptance test with some modifications to the magnitude of the loads. Using these load cases and design criteria, multiple FE models are used to identify the dominant mechanics of the bolted joint and contact problem. Each model features parametric relationships that enable rapid design changes including geometric features and mechanics. The development of hierarchical FE models facilitates the selection of a specific model that embodies the essential mechanics of the problem while maintaining a geometry that allows for parametric tradeoff studies. The design variables and baseline finite element model are used as an analysis tool developed as an Abaqus scripted template for design comparison studies. The hierarchical approach to finite element modeling with a parametric model has been applied to the development of a bolted insulated rail joint design, which has been realized in a new insulated joint prototype. The mechanics explored in the FE models can be verified using various full-scale load frame tests in a controlled environment. Tests are standardized across models using identical boundary conditions and load cases. The results obtained will be used to confirm modeling assumptions and provide necessary information for further prototype development. The prototype of the full 3-D geometry will be tested in track at TTCI for final design verification. The hierarchical parametric finite element modeling approach results in a tool that can be applied to joint design across the rail industry.