Reference-free load-modulated longitudinal rail stress measurement using ultrasonic LCR waves
Inventors
Chen, Xin • Cobb, Adam C. • Earnest, Douglas R. • Bartels, Keith A.
Assignees
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Publication Number
US-12411111-B2
Publication Date
2025-09-09
Expiration Date
Abstract
A method of in situ measurement of an acoustoelastic constant (L) of a railway rail, using an ultrasonic wedge sensor to measure a stress-free (unloaded) time-of-flight (t0) in the vertical direction of the rail. Next, a vertical load of known load value is applied to the rail. While the vertical load is applied, the ultrasonic wedge sensor is used to measure a stressed time-of-flight value. The difference between the stress-free and the stressed time-of-flight is calculated to obtain a time-of-flight difference value (Δt). Based on the load value, the stress-free time-of-flight value, and the time-of-flight difference value, the acoustoelastic constant, L, may be calculated. The wedge sensor may be further used to measure the (stressed) horizontal time of flight, and a time-of-flight difference value in the horizontal direction may be used to measure longitudinal stress.
Core Innovation
The invention relates to in situ measurement of stress in a railway rail using ultrasonic wedge sensor time-of-flight measurements and the acoustoelastic effect. It includes measuring a stress-free (unloaded) time-of-flight in the vertical direction of the rail with an ultrasonic wedge sensor having at least one receiver and one transmitter, and then applying a vertical load of known load value to the rail.
While the vertical load is applied, the ultrasonic wedge sensor measures a stressed time-of-flight value in the vertical direction. The invention derives a time-of-flight difference by calculating the difference between the stress-free and stressed time-of-flight values, and based on the load value, the stress-free time-of-flight value, and the time-of-flight difference value, calculates an acoustoelastic constant, L, for the rail material.
For longitudinal stress measurement, the invention extends ultrasonic wedge sensor operation to measure time-of-flight in the horizontal (longitudinal) direction. Using the stress-free time-of-flight value, the acoustoelastic constant L, and a time-of-flight difference value from the time-of-flight in the horizontal direction, the invention calculates the longitudinal stress.
Claims Coverage
The partial content includes three independent claims. Across these independent claims, the main inventive features concern vertical stress-free and stressed time-of-flight measurements to obtain an acoustoelastic constant L, longitudinal stress calculation using vertical and horizontal time-of-flight differences with L, and a wedge-sensor-based system with a load frame/actuator and control and analysis system.
Vertical time-of-flight to calculate acoustoelastic constant L
using an ultrasonic wedge sensor to measure a stress-free (unloaded) time-of-flight in the vertical direction of the rail, applying a vertical load of known load value to the rail, while the vertical load is applied using the ultrasonic wedge sensor to measure a stressed time-of-flight value, calculating the difference between the stress-free and the stressed time-of-flight to obtain a time-of-flight difference value, and based on the load value, the stress-free time-of-flight value, and the time-of-flight difference value, calculating the acoustoelastic constant, L.
Vertical plus horizontal time-of-flight to calculate longitudinal stress
using an ultrasonic wedge sensor to measure a stress-free (unloaded) time-of-flight in the vertical direction of the rail, applying a vertical load of known load value to the rail, while the vertical load is applied using the ultrasonic wedge sensor to measure a stressed time-of-flight value, calculating the difference between the stress-free time-of-flight value and the stressed time-of-flight value to obtain a time-of-flight difference value, based on the load value, the stress-free time-of-flight value, and the time-of-flight difference value, calculating the acoustoelastic constant, L, using the ultrasonic wedge sensor or another ultrasonic wedge sensor to measure time-of-flight in the horizontal (longitudinal) direction, and based on the stress-free time-of-flight value, the acoustoelastic constant, L, and a time-of-flight difference value from the time-of-flight in the horizontal direction, calculating the longitudinal stress.
Ultrasonic wedge sensor system with load frame and control/analysis for acoustoelastic constant
an ultrasonic wedge sensor having angled transducers that produce the required refraction of an ultrasonic wave for acquiring time-of-flight measurements in a railway rail; a load frame and actuator operable to apply a known load in the vertical direction to the rail; and a control and analysis system operable to provide and receive ultrasonic signals from the wedge sensor, to calculate time-of-flight values in the rail unstressed in the vertical direction and stressed with the load in the vertical direction, and to calculate an acoustoelastic constant of the rail material based on the time-of-flight measurements.
Across the independent claims, the core approach is to measure vertical stress-free and stressed time-of-flight values with an ultrasonic wedge sensor, calculate a time-of-flight difference, and use that information with the known vertical load to determine the acoustoelastic constant L. Longitudinal stress is then calculated by additionally measuring time-of-flight in the horizontal (longitudinal) direction and using L together with the vertical and horizontal time-of-flight difference values. The system claim recites a wedge-sensor-based hardware configuration with a vertical load frame/actuator and a control and analysis system to execute the time-of-flight and acoustoelastic constant calculations.
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