Nondestructive measurements of elastic constants of thin rods based on guided waves

Thin rods have been widely used in mechanical systems. The elastic constants, such as Young's modulus and Poisson's ratio, are of great interest for evaluating the quality of thin rods. This paper proposes a nondestructive method, utilizing longitudinal guided waves at low frequency and flexural guided waves at high frequency, to approximate bar waves and transverse bulk waves, respectively. According to the approximate velocities of bar waves and transverse bulk waves, the elastic constants can be determined inversely. Both simulation and experiment are conducted on thin aluminum rods with known elastic constants. The measurement errors are less than 2.03%, demonstrating the correctness of proposed method. Then, the proposed method is applied on 20 thin basalt rods and 30 basalt fibers. The incident frequency ranges from 0.3 to 1.8 MHz, and the diameter of thin rods ranges from 0.58 to 1.51 mm. The determined Young's modulus is 4.30% higher than the value from the destructive tensile tests, and the determined Young's moduli increase linearly with the chemical content (Al2O3, MgO, TFe2O3, and TiO2). The proposed method and associated experimental and simulation techniques can be used in the quality control and nondestructive testing of rod-like structures made by homogenous isotropic linear elastic materials.