Harbin Institute of Technology

Bingquan Wang

Weijia Shi

Jiubin Tan

Bo Zhao

An ultrasonic measurement method for plane stress on the basis of a multi-wafer air-coupled transducer relates to the technical field of ultrasonic testing. The method solves problems that a traditional measurement method for plane stress generally computes the plane stress by changing at least 3 different measurement directions and obtaining information such as an acoustic time difference in the 3 measurement directions by using a pair of contact ultrasonic transducers, which is too complicated in operation, and a coupling agent can influence measurement accuracy of the plane stress. The method includes: emitting, by an excitation signal transmission end, an ultrasonic wave passing a wafer of the multi-wafer air-coupled transducer to a member to be measured; receiving, by an excitation signal reception end, an echo returned from the member to be measured through a corresponding wafer of the multi-wafer air-coupled transducer; obtaining an acoustic time difference of lamb waves through data processing according to the ultrasonic wave and the echo; and obtaining first principal stress, second principal stress and an included angle between the first principal stress and a fiber direction of an orthotropic composite material according to the acoustic time difference of the lamb waves. The method is suitable for the field of plane stress testing.

Ultrasonic measurement method for plane stress on the basis of multi-wafer air-coupled transducer

An air-coupled ultrasonic plane stress detection method for a composite material based on dual-modal sound-time ratios of a Lamb wave includes: S1: assembling a detection device; S2: based on the detection device and the dual-modal sound-time ratios of the Lamb wave in S1, using unidirectionally loaded stress to obtain different stress coefficient relations; S3: based on the stress coefficient relations in S2, solving stress coefficients; S4: based on the stress coefficients in S3, acquiring three sound-time ratios; S5: based on the sound-time ratios in S4, describing a stress state of a detection point; and S6: repeating S4 and S5 till completing detection and scanning. The method improves the accuracy of stress coefficient calibration and air-coupled ultrasonic stress representation of a composite material panel greatly.

Air-coupled ultrasonic plane stress detection method for composite material based on dual-modal sound-time ratios of lamb wave

An ultrasonic phased array transducer device with a two-dimensional hinge array structure belongs to equipment in the technical field of ultrasonic detection. A connecting rod is fixedly connected to a fixed support and a two-dimensional hinge array respectively. Voice coil motors are symmetrically arranged in a shape of the British 'Union Jack' with the connecting rod as a center, and are fixedly connected to the fixed support. Force output rods are respectively connected to voice coil motor coils and the upper surfaces of array units. Piezoelectric array elements are fixedly connected to the lower surfaces of all the array units. The numbers of the voice coil motors and the force output rods are 2N (N=4, 8, 12, 16, 20), the number of the piezoelectric array elements is 2N+1, and different N values are selected according to the sizes of workpieces to be detected. In the disclosure, by adjusting the current of each voice coil motor coil, the corresponding force output rod generates displacement to drive the two-dimensional hinge array unit to generate displacement, so as to push out and retract the hinge array unit and the piezoelectric array element fixedly connected below and drive the two-dimensional hinge array to generate deformation, so that the piezoelectric array elements fully fit with the surface of the workpiece to be detected. The disclosure can be applied to detection of the workpieces to be detected with flat surfaces, curved surfaces or spherical surfaces.

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Harbin, China

Bingquan Wang