Solid-liquid interface reconstruction for sandwich structure metal plate via laser-ultrasonic techniques

Area of Science:

• Materials Science
• Non-Destructive Testing
• Mechanical Engineering

Background:

• Continuous casting is a crucial process in steel production, but internal defects like liquid cores can compromise product quality.
• Detecting internal structures in moving, inaccessible materials presents significant challenges for quality control.
• Existing non-destructive testing (NDT) methods may have limitations in speed, resolution, or applicability to dynamic industrial processes.

Purpose of the Study:

• To develop and validate a novel laser-ultrasonic testing system for real-time, in-situ liquid core detection in continuous casting slabs.
• To investigate the behavior and reflection characteristics of elastic waves at solid-liquid interfaces within moving materials.
• To establish a reliable method for reconstructing the position and characteristics of internal interfaces using NDT data.

Main Methods:

• A hybrid laser-ultrasonic system was designed and constructed, integrating laser-induced ultrasound generation with ultrasonic wave detection.
• Finite element method (FEM) simulations were employed to model elastic wave propagation and reflection at solid-liquid interfaces.
• Experimental validation was performed on a sandwich structure aluminum plate, simulating the conditions of a continuous casting slab.
• Time-of-flight (TOF) data from reflected ultrasonic waves were analyzed to reconstruct interface positions.
• B-scan imaging techniques were utilized to visualize the detected interfaces.

Main Results:

• The laser-ultrasonic system successfully detected solid-liquid interfaces in a simulated continuous casting environment.
• FEM simulations accurately predicted wave propagation and reflection patterns at different interfaces.
• Preliminary detection and reconstruction of solid-liquid interfaces were achieved using TOF data from a sandwich structure.
• Analysis of multiple ultrasonic echoes revealed distinct reflection and transmission characteristics at interfaces.
• A B-scan map clearly differentiated between echoes from various interfaces, demonstrating system sensitivity.
• Interface positions were calculated with a high degree of accuracy, showing a relative error of no more than 1.3%.

Conclusions:

• The developed laser-ultrasonic system is a viable non-destructive technique for detecting liquid cores in moving continuous casting slabs.
• The study demonstrates the effectiveness of analyzing elastic wave reflections for characterizing solid-liquid interfaces in industrial materials.
• This approach offers a promising solution for real-time quality control and defect detection in high-temperature, inaccessible manufacturing processes.