Evaluation of Welded Lap Joints Using Ultrasonic Guided Waves

Area of Science:

• Materials Science and Engineering
• Non-Destructive Testing
• Structural Health Monitoring

Background:

• Welded lap joints are critical in structures like pipelines and ship hulls.
• Defect detection in these joints is essential for structural integrity.
• Current inspection methods often require baseline data, limiting their applicability.

Purpose of the Study:

• To investigate ultrasonic guided wave propagation in steel welded lap joints.
• To develop a baseline-free inspection method for joint defects using Lamb wave mode conversion.
• To analyze the sensitivity of different wave modes to corrosion and disbonding.

Main Methods:

• Finite element method (FEM) simulations of single lap joints with defects.
• Wavenumber-frequency analysis using 2D Fast Fourier Transform (FFT) to identify wave modes.
• Measurement of transmitted mode power loss to quantify damage effects.

Main Results:

• A0 incident showed higher transmission loss (9.5 dB) than S0 incident (2.8 dB) in pristine joints.
• Corrosion reduced transmission losses by over 28%, while disbonding increased S0 loss.
• Mode-converted S0 (MC-S0) and mode-converted A0 (MC-A0) waves exhibited distinct sensitivities to corrosion and disbonding.

Conclusions:

• Lamb wave mode conversion offers a promising baseline-free approach for inspecting welded lap joints.
• Differential interactions of MC-S0, MC-A0, and Lamb modes with defects enable damage identification.
• This method enhances the ability to detect corrosion and disbonding in critical engineering structures.