Patent AU-2021101832-A4 (AU)
Title: Ultrasonic testing method of suspension bridge screw axial force based on Gaussian echo envelope model
Inventor: CHEN XIN
IPC: G01H17/00
Filed: 2021-04-09
Granted: 2021-06-03
Abstract: The invention discloses an ultrasonic testing method of screw axial force of suspension bridge 
based on Gaussian echo envelope model, which relates to the technical field of ultrasonic 
nondestructive testing. The method includes: Establishing the calculation formula of screw 
axial force, making suspension bridge cable clamp screw sample, calibrating screw stress 
coefficient and screw temperature coefficient in turn, and substitute them into the screw axial 
force calculation formula. Setting each parameter threshold of the Gaussian echo envelope 
model. Ultrasonic excitation is applied to the end face of the screw to be tested to obtain an 
echo signal of the screw to be tested, and a Gaussian echo envelope model of the screw to be 
tested is established. When the amplitude parameter of Gaussian echo envelope model of screw 
to be tested is larger than the threshold value of amplitude parameter, its scale parameter is 
larger than the minimum threshold value and smaller than the maximum threshold value of 
scale parameter, and its determination coefficient is larger than the threshold value of 
determination coefficient, the time parameter of Gaussian echo envelope model of screw to be 
tested is obtained as the echo sound of screw to be tested, and the axial force of screw to be 
tested is calculated. The method has the advantages of high detection speed, high precision and 
reliable axial force result.
1/3 
FIGURES 
According to the linear relationship between screw axial force and 
longitudinal wave velocity, the calculation formula of screw axial force is Si 
established.  
Make the sample of suspension bridge cable clamp screw, calibrate the 
screw stress coefficient and screw temperature coefficient in turn, and S2 
substitute it into the screw axial force calculation formula.  
According to the calibration process of screw stress coefficient and saew temperature coefficient. the 
threshold values of parameters of Gaussian echo envelope model are set. Each parameter threshold S3 
includes amplitude parameter threshold, scale parameter minimum threshold, scale parameter 
maximum threshold and determination coefficient threshold.  
Ultrasonic excitation is applied to the end face of the screw to be tested to 
obtain the echo signal of the screw to be tested, and then the echo envelope S4 
signal is obtained, and the Gaussian echo envelope model of the screw to be 
tested is established.  
When the amplitude parameter of Gaussian echo envelope model of the screw 
to be tested is larger than the threshold value of amplitude parameter, its scale 
parameter is larger than the minimum threshold value and smaller than the S5 
maximum threshold value of scale parameter, and its determination coefficient 
is larger than the threshold value of determination coefficient, the time 
parameter of Gaussian echo envelope model of the screw to be tested is 
obtained as the echo sound of the screw to be tested, and brought into the 
calculation formula of screw axial force to obtain the screw axial force to be 
tested.  
Fig. 1 The first flow chart of the method for detecting axial force of suspension bridge 
screw provided by an embodiment of the present invention.