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Updated: May 31, 2026
Ultrasound Velocity Measurement in a Liquid Metal Electrode
Published on: August 5, 2015
Non-contact ultrasonic measurement of the layer thickness for multi-layer CuAl clad sheet using electromagnetic
Yi Zhang1, Zhuoting Liu1, Yingjie Shi1
1Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing, China.
Abstract:
Accurate online measurement of each layer thickness of CuAl clad sheets during the rolling process is vital for real-time process monitoring and ensuring consistent product quality. This study proposes an electromagnetic acoustic transducer (EMAT)-based resonance frequency method for non-destructive thickness determination of Cu and Al layers in both two-layer (Cu/Al) and three-layer (Cu/Al/Cu) clad sheets. The resonance frequency theory for multilayer structures was validated through EMAT sweep-frequency experiments and subsequently applied to inversely determine the Cu and Al layer thicknesses. However, the transcendental resonance frequency equations, which involve density, ultrasonic velocity, and layer thickness, can yield multiple solutions for the Cu layer thickness determination. To address this issue, a Cu-thickness determination algorithm was proposed to derive the unique solution. Experimental validation demonstrated high Cu layer thickness accuracy: (1) For a total thickness of 6.257 mm in a two-layer Cu/Al clad sheet, the Cu thickness measurement error was 0.038 mm (relative error-1.7%); (2) for a 7.345 mm two-layer Cu/Al sheet, 0.014 mm (0.94%); and (3) for a 3.082 mm three-layer Cu/Al/Cu sheet, 0.006 mm (1.2%). Moreover, an online EMAT-based thickness measurement system was established, capable of determining total and layer thickness within 1 s, highlighting its potential for real-time implementation in CuAl or other multi-layer metal material manufacturing processes. Finally, Cu thickness measurement sensitivity analysis revealed that density variations in Cu and Al have a minor effect on Cu-layer thickness measurement, whereas acoustic velocity variations in Cu and Al, as well as total-thickness measurement errors, have a significant impact. Consequently, reliable layer-thickness determination requires ultrasonic velocity calibration errors to be within ±3% and total-thickness measurement errors within ±1%.
