Ultrasonic guided wave focusing in waveguides with constant irregular cross-sections

Area of Science:

• Structural Health Monitoring
• Acoustic Engineering
• Materials Science

Background:

• Switch rails in high-speed railways are prone to damage under operational stress, necessitating precise online detection.
• Ultrasonic guided waves are suitable for monitoring switch rail integrity but suffer from energy decentralization.
• Existing phased array systems effectively focus waves in regular waveguides but not in irregular ones.

Purpose of the Study:

• To propose and verify a method for focusing ultrasonic guided waves in waveguides with constant irregular cross-sections, specifically for railway switch rails.
• To enhance the detectability and monitoring capabilities of switch rail structural integrity.
• To investigate the influence of various factors on guided wave focusing.

Main Methods:

• Analysis of guided wave characteristics using a semi-analytical finite element method (SAFEM) for partial loadings.
• Development of an algorithm to calculate amplitude weights and time delays for modulating excitation signals.
• Numerical simulations on a switch rail base with a constant irregular cross-section to verify the focusing method.

Main Results:

• Effective steering and focusing of guided acoustic beams to predetermined locations were achieved.
• Enhanced acoustic wave energy was observed at the focal points, improving detectability.
• The study identified optimal parameters, recommending low center frequencies and narrow bandwidths for excitation signals.

Conclusions:

• The proposed method successfully demonstrates ultrasonic guided wave focusing in irregular cross-section waveguides like switch rails.
• This technique significantly improves the potential for precise online detection and structural integrity assessment of railway switch rails.
• Low frequency, narrow bandwidth excitation signals are optimal for achieving the best focusing results in such complex geometries.