Experimental apparatus for axial force attenuation of bolts

In this section, a bolt axial force detection system based on ultrasonic surface waves is established. The transmitted signal energy of the surface waves can be used to detect the bolt axial force, and the attenuation of the bolt axial force can be monitored online by using the surface wave energy dissipation method. M20X60 6.8-level 304 stainless steel bolts were used as test objects for the constructed experimental device, which was installed on the test bench according to relevant process requirements, as shown in Figure 2.

The test bench can simulate the process of bolt tightening. The lower end of the tension pressure sensor is fixed on the bottom plate through the double stud, and the bolt of M20 is connected with the upper end of the tension pressure sensor with the interface of M12 through the conversion sleeve. The internal direction of the conversion sleeve is positive rotation, and the bolt and tension sensor can be pulled to the center of the conversion sleeve at the same time by turning the conversion sleeve counterclockwise. The strain gauge in the tension pressure sensor is driven to change, so as to apply axial tension to the bolt. The measured value of axial tension can be displayed in real time on the force value display controller YBB-AH.

Here, ultrasonic pulse generator/receiver 5072PR manufactured by OLYMPUS is used to excite and receive ultrasonic surface wave signals. The probe uses OLYMPUS Piezoceramic surface wave tilt probe (tilt Angle is 70°) manufactured by Panametrics of America (1MHz). The low pass filtering method is used to eliminate the noise, and the surface wave inclined probe is fixed on the bolt plate with transparent tape to prevent it from sliding. The waveform signal is received and displayed by TBS1052B digital oscilloscope produced by TEK⁃ TRONIX with sampling frequency of 50MB/s and gain of 56dB, and the data is stored by oscilloscope.