Application Cases

Air-coupled ultrasonic technology, as an efficient and non-destructive testing method, has received widespread attention in the industrial field in recent years. Its uniqueness lies in the use of air as the coupling medium, allowing for high-precision detection and imaging without direct contact with the object being tested. It can detect defects in in-service CFRP plates to ensure their safe application. However, traditional air-coupled ultrasonic methods typically rely on linear defect indices, which are ineffective in characterizing small-sized defects. Moreover, the scanning step size completely limits their imaging spatial resolution, leading to a contradiction between imaging spatial resolution and detection efficiency.

To address the above issues, a research team from the School of Instrument Science and Technology at Harbin Institute of Technology has proposed a nonlinear defect index and an adaptive weighted imaging algorithm. This research achievement has been published in the well-known international journal of mechanical engineering research, Mechanical Systems and Signal Processing. Today, Aigtek will share this in depth.

Experiment Name:

The Application of the ATA-2041 High-Voltage Amplifier in Air-Coupled Ultrasonic In-Situ Measurement of Delamination Defects in CFRP Plates

Experiment Direction:

Non-destructive testing of composite materials

Experimental Equipment:

ATA-2041 high-voltage amplifier, function signal generator, piezoelectric ceramic, data acquisition card, oscilloscope, PC, etc.

Experiment Content:

In the air-coupled ultrasonic technology with nonlinear defect index and adaptive weighted imaging algorithm, the nonlinear defect index uses the relative nonlinear coefficient of Lamb waves to enhance the ability to detect small-sized defects. Considering the beam width, the adaptive weighted imaging algorithm constructs the relationship between any imaging point and all imaging points along the scanning path. At this point, the imaging spatial resolution can be set arbitrarily, eliminating the dependence on scanning step size.

Experiment Process:

The function signal generator produces a sine pulse signal with a center frequency of 200 kHz modulated by a Hanning window. Subsequently, a voltage power amplifier is used to increase the excitation signal voltage to 400 Vpp to ensure that the air-coupled transducer generates sufficient acoustic energy. The XZ adjustment platform adjusts the horizontal distance between the two air-coupled ultrasonic transducers and the vertical distance between the air-coupled ultrasonic sensor and the CFRP plate.

The angle adjuster adjusts the incident and receiving angles θ of the air-coupled ultrasonic transducer to ensure that the air-coupled ultrasonic transducer generates Lamb waves in the CFRP plate and eliminates the interference of the direct wave. The XY motion platform realizes step scanning in the 0° fiber direction and the 90° fiber direction. Due to the significant signal attenuation in the air, a preamplifier amplifies the received signal from the air-coupled ultrasonic transducer. A high-speed acquisition card collects the echo signal and uploads it to the upper computer for processing and imaging.

Experiment Results:

The experimental results show that the proposed nonlinear defect index can characterize small-sized defects more accurately than the linear defect index. When the scanning step size is increased to improve detection efficiency, the adaptive weighted imaging algorithm can achieve better imaging spatial resolution, improving the traditional probability of detection imaging algorithm.

For small defects with a diameter of 10 mm, the area detection error of the proposed method is only 7.8%, while the traditional method has an error of 22.4%.

Specifications of the ATA-2041 high-voltage amplifier used in the experiment: