Measurement method of bolt axial stress based on ultrasonic guided waves
Wind turbine blade is the core component of wind turbines.The blade bolt is not only the part that bears complex stress,but also the part that bears the highest load.In order to avoid potential hazard and economic loss caused by bolt breakage,an axial stress measurement system for in-service bolts based on ultrasonic guided waves is designed,which can achieve accurate measurement of axial stress for various types of bolts.Firstly,the group velocity dispersion curve of ultrasonic guided wave was obtained through numerical calculation,and a linear mathematical model of bolt axial stress and ultrasonic guided wave acoustic time was established based on the Hooke's law and acoustic elasticity effect.The effectiveness of ultrasonic guided wave stress measurement by single longitudinal wave transducer was verified by simulation in COMSOL software.Then,in view of the modal aliasing of ultrasonic guided wave echo signals and the interference of noise on the measured results of ultrasonic guided wave acoustic time in actual measurement,the denoising algorithm based on echo compensation was used to denoise the actual measurement signal.The empirical wavelet transform algorithm was used to decompose the modal of ultrasonic guided wave echo signal,and the cross-correlation method was used to obtain the accurate acoustic time of ultrasonic guided wave modal.Finally,the precise measurement of axial stress for 18 types of bolts within the 30%-90%yield strength was completed through experimental tests,and the relative measurement error was less than 2%.The research results are helpful to improve the bolt assembly process and standardize the worker's operation process.
国家科技期刊平台
NSTL
万方数据
