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New Mexico State University

New Mexico State University

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NMSU professor seeks to improve monitoring of railroad track safety

NMSU professor seeks to improve monitoring of railroad track safety

In the United States alone, there are tens of thousands of miles of railroad tracks that provide a vital link in the nation's transportation system.

Although these tracks are made of steel, tiny cracks can develop in them that keep growing and growing until they get to the point that they can cause a wheel to come off a rail, resulting in a train derailment.

The cost to industry and private consumers due to the closure of a crucial span of rail for even one day can be on the order of millions of dollars. According to the Federal Railroad Administration, approximately $303 million worth of damage was caused by major forms of rail defects between 1992 and 2002.

John McNamara, an assistant professor of civil engineering at New Mexico State University, is studying new ways to inspect railroad tracks. Techniques he is developing could greatly improve safety on railroads, especially small rail lines in New Mexico.

Currently, McNamara explains, railroad tracks are inspected using wheel-shaped devices mounted on trucks that travel down the rail. These devices house multiple instruments, known as transducers, that send ultrasonic waves out at different angles and listen for their reflections as they bounce back from the bottom of the rails. These systems sound an alarm if an abnormality is detected, and a maintenance person riding on the truck can stop and inspect the area.

Unfortunately, McNamara says, a large number of these alarms turn out to be false alarms. In addition, the current system cannot detect cracks that start at the edge of the rails, which can lead to some of the most dangerous defects.

"If you wait to detect cracks using conventional methods, they can grow a lot bigger, even to the point of rupturing, before they are detected," he says.

McNamara is trying to develop a new system for inspecting rails that would better position the transducers so that they can inspect more of the rail cross-section. The system he has in mind would place an array of transducers on one side of a rail and an array of receivers on the other side. The transducers would send signals through the track to the receiver. Changes in the strength and characteristic properties of the signal would indicate an internal defect.

The key to the system, McNamara explains, is increasing the signal-to-noise ratio so that the receiver will pick up the presence of small cracks. This is where his expertise in applied physics and signal processing is utilized.

McNamara also is investigating a "guided wave" system that could send waves longitudinally down a rail over long distances. This system could be used on its own or in conjunction with current systems to detect possible abnormalities for inspection.

"This type of continuous monitoring 'smart system' would be valuable for homeland security," he says. This system could be left in the field permanently to monitor the condition of the rails continuously. Any changes in the rails could be detected before a train passes over them.

McNamara notes his technique also could be used to test rails as they are manufactured. Currently, only the welds on rails are checked when they are installed in the field.

McNamara plans to talk to the owners of small railroad systems in New Mexico and to the New Mexico Department of Transportation so that he can make a prototype of a system that would be particularly suited to address their needs.

"New Mexico has many short rail lines that may only have one person assigned to rail maintenance and inspection," McNamara says. "I want to come up with something that is affordable enough so that our small rail companies can use it in conjunction with their current maintenance practices to improve their overall track safety."

He says engineers at Holloman Air Force Base in Alamogordo also have expressed interest in using his system to inspect the 10 miles of high-speed rail track they have to test the effect of warheads on a target.

"These rails are pre-tensioned at very high tensions so that they remain perfectly straight. The drawback is that small defects that regular rail lines might be able to live with are a big problem for them because the tracks might pop and pull apart if a small crack is present, due to the existing rail tensions," McNamara says. "We need to develop much more sensitive instrumentation to detect those defects. If we can detect one of their defects, we can definitely detect defects in regular rail