Ultrasonic Hardware Circuit Design and Signal Processing for Measuring Axial Stress of Small‐Sized Bolts

The precise measurement of the axial stress of bolts is of great significance for improving the assembly accuracy and performance stability of high‐end equipment such as aeroengines. In response to the problem of low signal‐to‐noise ratio (SNR) of the echo signal in the measurement of axial stress of small‐sized bolts using the ultrasonic method, this paper optimizes the design of hardware circuits to improve the SNR of the echo signal, thereby achieving accurate measurement of axial stress. The transmission circuit is optimized and designed to reduce clutter interference. To overcome the impact of aliasing between the transmitted signal and the echo signal, the pulse repetition frequency of the ultrasonic transmission circuit is optimized. To suppress the impact of high‐voltage transmitted pulse signals on echo signals, an optocoupler is used to optimize the isolation circuit of ultrasonic transmitted pulses. An experimental system was established based on the axial stress measurement model of small‐sized bolts. The maximum error in axial stress measurement of small‐sized bolts (M6) was 26.50 MPa, with a relative error of 8.8%. The feasibility of the hardware circuit designed in this paper has been verified through measurement experiments. This study provides effective hardware and technical support for precisely measuring the axial stress of small‐sized bolts in high‐end equipment.