	US 12,480,913 B2
	Ultrasonic measurement method for plane stress on the basis of multi-wafer air-coupled transducer
Weijia Shi, Harbin (CN); Bingquan Wang, Harbin (CN); Bo Zhao, Harbin (CN); and Jiubin Tan, Harbin (CN)
Assigned to Harbin Institute of Technology, Harbin (CN)
Filed by Harbin Institute of Technology, Harbin (CN)
Filed on Aug. 9, 2023, as Appl. No. 18/232,330.
Claims priority of application No. 202210980454.4 (CN), filed on Aug. 16, 2022.
Prior Publication US 2024/0060935 A1, Feb. 22, 2024
Int. Cl. G01N 29/04 (2006.01); G01N 29/07 (2006.01)

CPC G01N 29/041 (2013.01) [G01N 29/07 (2013.01); G01N 2291/011 (2013.01)]

6 Claims

1. An ultrasonic measurement method for plane stress on the basis of a multi-wafer air-coupled transducer, wherein the transducer comprises six wafers, dual matching layers and a backing layer; each wafer is fixed to an upper surface of the dual matching layers, and an upper surface of each wafer is attached to the backing layer; the six wafers are uniformly distributed in the transducer in a circumferential direction, any three adjacent wafers are configured to transmit an excitation signal, the other three wafers are configured to receive an echo signal, and every two wafers having a consistent radial direction with a center of the transducer constitute a group of wafers; the transducer further comprises an excitation signal reception end and an excitation signal transmission end; the wafers configured to transmit the excitation signal are connected to the excitation signal transmission end by means of wires, such that the excitation signal transmission end transmits the excitation signal to the wafers; the wafers configured to receive the echo signal are connected to the excitation signal reception end by means of wires, such that the echo signal is converted into an electrical signal, and the electrical signal is output from the excitation signal reception end; the transducer further comprises a housing, and the wafers, the dual matching layers and the backing layer are all fixed in the housing; the excitation signal reception end and the excitation signal transmission end are both fixed to an outer side of the housing; the housing is a cylinder; and the method is implemented on the basis of the transducer, and the method comprises:

transmitting, by the excitation signal transmission end, the excitation signal to the wafer configured to transmit the excitation signal, and converting, by the wafer, the received excitation signal into an ultrasonic signal and transmitting the ultrasonic signal to a member to be measured;

transmitting, by the member to be measured, the echo signal to the wafer configured to receive the echo signal, and converting, by the wafer, the received echo signal into a response signal and transmitting the response signal to the excitation signal reception end;

obtaining an acoustic time difference of lamb waves through data processing according to the ultrasonic signal and the echo signal; and

computing first principal stress σ₁, second principal stress σ₂and an included angle θ between the first principal stress and a fiber direction of an orthotropic composite material according to the acoustic time difference of the lamb waves, wherein

the computing first principal stress σ₁, second principal stress σ₂and an included angle θ between the first principal stress and a fiber direction of an orthotropic composite material according to the acoustic time difference of the lamb waves is specifically as follows:

a first testing direction is 0°, a second testing direction is 60°, and a third testing direction is 120°; and

wherein

A is a first parameter of an intermediate variable; B is a second parameter of an intermediate variable; C is a third parameter of an intermediate variable; T_0° is an acoustic time difference in the first testing direction, T_60° is an acoustic time difference in the second testing direction, T_120° is an acoustic time difference in the third testing direction, and a₁, a₂, a₃and a₄are constants.