Open Access

ARTICLE

A Real-time Monitoring Technique for Local Plasticity in Metals Based on Lamb Waves and a Directional Actuator/Sensor Set

Y. L. Liu¹, N. Hu², H. Xu³, H. Ning¹, L. K. Wu¹

1 Department of Mechanical Engineering, Chiba University, Chiba, Japan.
2 College of Aerospace Engineering, Chongqing University, Chongqing, China.
3 Mechanical and Electrical Engineering Institute, Beijing University of Chemical Technology, Beijing 100029, China.

Computers, Materials & Continua 2014, 40(1), 1-20. https://doi.org/10.3970/cmc.2014.040.001

Abstract

A real-time monitoring technique for local plasticity using Lamb waves was developed. Tensile test of a thin aluminum plate with a circular hole where high stress concentration was induced was conducted to verify this technique. During the tensile test, a series of wave signals passing through the local plastic region were collected using a directional actuator/sensor set to monitor plasticity evolution. A pulse compression technique was used to process the wave signals. With the increase of tensile stress in the specimen, the amplitude changes of S₀ and A₀ modes were obtained and the difference of Lamb wave signals was further evaluated using a proposed signal index I calculated by wavelet analysis. Combined with the numerical stress analysis of the tensile specimen, the influence of the plasticity on the amplitudes of S₀ and A₀ wave modes was analyzed. As the plastic zone grows gradually, the wave amplitudes and I of S₀ and A₀ wave modes show their different change tendencies compared with those in elastic stage. The amplitude change is more sensitive to mild plasticity than that of I, while the change of I caused by severe plasticity is more obvious than the amplitude change.

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Keywords

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