Hazard Assessment of Damaged Tank Cars

A concern for salvage operations following a derailment is the safety of pressure tank cars that have been damaged. Established guidelines are used in salvage operations to ensure safe practice for unloading, moving, and/or clearing damaged tank cars. These guidelines consider a variety of damage modes such as cracks, dents, scores, or gouges.

SRI has been working in support of the Federal Railroad Administration (FRA) to validate and formalize the guidelines for salvage of damage tank cars. SRI performed experiments and analyses on tank cars and tank car steels to establish safe loading conditions for various types and levels of damage.

As part of this program SRI developed a finite element model of a pressure tank car as shown in Figure 1 . The model was created to evaluate the stresses in the tank car from various pressure and lifting conditions as shown in Figure 2 . The model was developed for the DYNA3D finite element code such that damage resulting from various impact loads could also be evaluated.

A cleavage fracture model was developed for tank car steel and incorporated into DYNA3D. Calibration of the model was performed using smooth and notched tensile specimens as shown in Figure 3 . The Cleavage model predicts the probability of cleavage rupture based on the geometry and loading conditions of the various specimens. Comparison of measured and predicted response for notched round bar tests with the cumulative rupture probabilities are shown in Figure 4 .

The final step of the research program was to apply the cleavage model and perform additional laboratory tests to analyze various types of damage. For example, bend bars and gouge specimens were tested to evaluate the safety of dents and gouges respectively. Figure 5 shows a simulation of the bend bar test to evaluate potential for cleavage fracture around dents.

Figure 1 Tank Car Safety Finite Element Model of a Pressure Tank Car.

Figure 2 Tank Car Safety Tank Car Loading Stress Profiles

Figure 3 Tank Car Safety Tank Car Steel Material Characterization Specimens

Figure 4 Tank Car Safety Tank Car Steel Cleavage Analyses

Figure 5 Tank Car Safety Tank Car Steel Damage Analyses

Contact Us
Don Shockey
Director, Center for Fracture Physics
Phone: 650-859-2587
Email: donald.shockey@sri.com