The effect of load on guided wave propagation

Area of Science:

• Structural Health Monitoring
• Wave Mechanics
• Computational Mechanics

Background:

• Load measurement in structural members like cables and rails is crucial.
• Guided waves offer a promising non-destructive method for structural analysis.

Purpose of the Study:

• To develop load measurement techniques using guided wave velocity.
• To model the dispersion characteristics of guided waves in structures under axial load.
• To compare finite element (FE) models with simpler beam models.

Main Methods:

• A finite element technique was employed to model guided wave dispersion.
• Dispersion characteristics were analyzed for waveguides of arbitrary cross-section.
• Results were compared against the Euler-Bernoulli beam model.
• A dimensionless sensitivity measure (fractional velocity change per applied strain) was defined.

Main Results:

• At higher frequency-dimension products (fd > 1 for phase velocity, fd > 5 for group velocity), sensitivity to strain becomes independent of strain.
• In this range, phase velocity increases with tensile load, while group velocity decreases.
• The Euler-Bernoulli beam model is accurate for simple cross-sections but less so for complex ones like rails.
• The Euler-Bernoulli model fails to capture high-frequency mode sensitivities and torsional mode sensitivity in complex structures.

Conclusions:

• The developed FE model provides a robust method for load measurement via guided wave velocity.
• The Euler-Bernoulli beam model has limitations for complex structural geometries and higher frequencies.
• Accurate load sensing requires advanced modeling for complex waveguides, especially at higher frequencies.