Methodology for Mapping the Residual Stress Field in Serviced Rails Using L_CR Waves.

Area of Science:

• Materials Science
• Non-Destructive Evaluation
• Acoustics

Background:

• Ultrasonic testing relies on the acoustoelastic modulus, linking material stress to sound wave velocity.
• Critically refracted longitudinal (LCR) waves are ideal for stress measurement due to significant travel time changes with stress.
• Frequency-dependent penetration depth of LCR waves allows for through-thickness stress distribution analysis.

Purpose of the Study:

• To visualize internal and residual stress distribution through the thickness of railroad rails.
• To apply LCR wave technology for accurate residual stress measurement in rails.

Main Methods:

• Designed and manufactured LCR probes with varying center frequencies.
• Collected ultrasonic signals from unused and used railroad rails.
• Mapped residual stress distributions through the rail thickness using received signals.

Main Results:

• Successfully calculated depth-dependent residual stress values in railroad rails.
• Visualized and analyzed differences in residual stress generation and distribution.
• Demonstrated distinct stress patterns based on rail usage and operational conditions.

Conclusions:

• Non-destructive evaluation using LCR waves effectively detects variations in rail residual stress.
• This technique provides accurate measurement of residual stress in rails.
• LCR wave analysis offers insights into stress characteristics influenced by train-rail interaction.