Structural Health Monitoring of Railroad Wheels Using Wheel Impact Load Detectors
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Structural Health Monitoring of Railroad Wheels Using Wheel Impact Load Detectors Brant Stratman Æ Yongming Liu Æ Sankaran Mahadevan
Submitted: 6 March 2007 / Published online: 3 July 2007 ASM International 2007
Abstract This paper proposes two quantitative criteria for removing railroad wheels from service, based on realtime structural health monitoring trends that are developed using data collected from trains while in service. The data is collected using wheel impact load detectors (WILDs). These impact load trends are able to distinguish wheels with a high probability of failure from high-impact wheels with a low probability of failure. The trends indicate the critical wheels that actually need to be removed, while at the same time allowing wheels that aren’t critical to remain in service. As a result, the safety of the railroad will be much improved by being able to identify and remove wheels that have high likelihood of causing catastrophic failures. Keywords Catastrophic failure Crack growth rate Data interpretation Failure analysis Nondestructive testing Structural health monitoring
Introduction Traditional inspection techniques used in the railroad industry, such as drive-by inspections where all of the wheels on the train are glanced at while an inspection vehicle drives by, are not as accurate and reliable as more rigorous and quantitative inspection methods. Many damaged wheels are not found, while many useable wheels are removed when they could remain in service. By using wheel impact load detectors (WILDs), structural health monitoring trends can be developed based on the wheel B. Stratman Y. Liu S. Mahadevan (&) Vanderbilt University, Nashville, TN 37235, USA e-mail: [email protected]
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impact data that indicates the actual condition of the wheels. The trends can indicate the critical wheels that actually need to be removed, while at the same time allowing wheels that are not critical to remain in service. The WILD system is composed of a series of strain gages welded to the rail. The strain gages quantify the force applied to the rail through a mathematical relationship between the applied load and the deflection of the foot of the rail. These impact forces are used to monitor locomotive and rail car wheel health to ensure safe train operations. The use of WILDs by railroads has resulted in the removal of high-impact wheels that damage bearings, lading, rail, other mechanical components, and the wheels themselves. Although wheels with extremely high impacts are rare on a percentage basis, small percentages do not equate to small effects. For example, high-impact wheels have been observed to increase the surface crack growth rate on a rail by a factor of nearly 100 times that under non-impact loading conditions [1]. Also, it has been shown in a numerical study that dynamic impacts have a detrimental effect on concrete sleeper health by increasing the risk of crack initiation [2]. High-impact wheels
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