Development and creation of tank car test plates for non-destructive evaluation assessments

The Federal Railroad Administration (FRA) currently owns a library of tank car defects, developed to better understand the probability of detection by non-destructive evaluation (NDE) techniques. A majority of the FRA’s defect plates were developed from a TC/DOT-111A tank car. The Transportation of Dangerous Goods Regulations required TC/DOT-111 and CPC-1232 tank cars to be phased-out and replaced with TC/DOT-117 enhanced safety tank cars. To broaden future NDE studies, with funding from Transport Canada (TC), the National Research Council of Canada (NRC) has developed a methodology for generating new defect plates to supplement existing ones. The objective was to form a novel defect library and include plates that are representative of a TC/DOT-117 tank car made with 9/16 inch (14.3 mm) thick TC-128 Grade B normalized steel plates. The research was conducted in phases. A methodology was first developed to generate realistic fatigue cracks along the circumferential weld. This was followed by a finite element–based fracture mechanics analysis to quantify stress intensity factors (SIFs) and establish critical crack sizes under representative service loading conditions, namely internal pressure, draft, and compressive loading. The critical crack sizes were used as residual-strength bounding estimates and were not used as probability of detection (POD) target sizes; the actual defect size distribution was selected separately to support NDE detectability studies using smaller, shallow fatigue cracks. Finally, based on the validated results demonstrating controlled crack growth and repeatability, the production phase of multiple tank car defect plates was completed. The defect plate inventory with natural true fatigue cracks may be used by the tank car industry as a reference for the calibration and continued enhancement of NDE to improve tank car safety inspections.