Enhanced analysis of H62 brass thin plates using integrated LIBS and laser ultrasonic Lamb wave for composition and flaw detection

Abstract

The concentration of compositions and the presence of defects can dominate the properties and behavior of brass thin plates. Therefore, it is crucial to simultaneously detect their compositions and defects, particularly during the manufacturing process. In this work, we propose an integrated system using Laser-Induced Breakdown Spectroscopy (LIBS) and laser ultrasonic Lamb wave (LW) systems to identify elemental concentrations and locate flaws in H62 brass thin plates. The first weaker pulse (1.5 GW/mm²) is utilized for determining main elemental compositions by calibration-free (CF)-LIBS. The second stronger pulse (14 GW/mm²) is employed to qualitatively detect trace elements and generates strong laser ultrasonic LW. An all-fiber laser heterodyne interferometer is applied for measuring ultrasonic signals, enhancing the system’s flexibility and efficiency. A triple-point receiver has been implemented to determine the location of defects. Additionally, a continuous wavelet transform is applied to analyze the ultrasonic wave at a center frequency of 370 kHz for flaw echo detection. The results demonstrate an error of 3.03 % in the determination of major composition concentrations (Cu, Zn, Fe, Pb), and observe the trace elements (Sn, Ni, Na, Al, Ca) with concentrations lower than 0.01 %. The flaw position is determined by using the four-point arc method, with a relative error of 1.2 % for a circular flaw with a diameter of 2 mm. Therefore, this non-contact measurement technique offers a promising approach for the simultaneous online detection of elemental concentrations and flaws in brass thin plates during manufacturing processes.