Application Cases

Railway transportation, as an important part of China's strategy to become a strong transportation nation, currently has a total operating mileage of 150,000 kilometers and is still in a period of rapid construction. Rails are the direct carriers for train operation. Due to long-term operation and vibration impacts, various defects and damages can occur inside and on the surface of the rails. If not detected and repaired in time, these issues can directly endanger the safety of trains and passengers. At present, rail ultrasonic damage detection usually employs piezoelectric sensors. However, each sensor requires a power line connection, making it difficult to achieve multipoint detection. In contrast, fiber Bragg gratings (FBG) have unique advantages such as electromagnetic interference resistance, ease of multiplexing, and corrosion resistance, making them very suitable for detecting damage in long-distance structures (such as rails) in harsh environments.

Aigtek's power amplifiers have extensive applications in driving piezoelectric ceramics and in the ultrasonic field. With different models available to match various parameters, they can drive most piezoelectric ceramics and ultrasonic transducers on the market.

Experiment Title: Study of Fiber Bragg Grating Ultrasonic Sensors

Experiment Principle:Mechanical structures or devices are excited by ultrasonic waves. Distributed FBGs measure the stress and strain (field) signals of the structure, which carry damage information, as well as ultrasonic wave signals, to analyze the damage condition of the mechanical structure. Acoustic emission technology is used for real-time online monitoring of rails. When a crack warning is detected, active ultrasonic excitation is used to reinspect the existing crack. The inspection process does not occupy train operation time and can be achieved through long-term fixed sensors on the rails for full-section, all-weather online monitoring of cracks.

Experiment Block Diagram:

Experiment System Real Photo:

Experiment Process:

When the active excitation signal propagates to the crack, it gradually attenuates. Additionally, when it passes through the crack boundary, reflection and transmission occur, further consuming signal energy. This makes it easy for the signal to be masked by the noise of the demodulation system and difficult to distinguish. Therefore, to more clearly observe the attenuated waveform, the signal generator produces an excitation signal that is further enhanced by the ATA-2021B high voltage amplifier. The sensing signal is filtered, and a double-sloped cone FBG ultrasonic sensor is used to detect the pulse signal in the measured structure, while an oscilloscope is used to observe the signal waveform.

Experimental Results:The ability of the double-sloped cone fiber Bragg grating ultrasonic sensor to identify damage was studied through lead break experiments, PZT active excitation steel plate experiments, and COMSOL finite element software. The results show that the sensor can effectively detect the acoustic emission signal emitted by the breaking of a pencil lead and can identify a hole with a radius of 5mm on a steel plate. Additionally, analysis using COMSOL finite element software indicates that increasing the frequency of the ultrasonic signal can detect smaller damage. A 1.5MHz ultrasonic signal can identify a crack of about 2mm. The sensor also has the capability to locate rail damage.

Power Amplifier Recommendation: ATA-2000 Series High Voltage Amplifier

Figure: Specifications of the ATA-2000 Series High Voltage Amplifier

The ATA-2000 series is an ideal high voltage amplifier capable of amplifying both AC and DC signals. It offers a maximum differential output of 1600Vp-p (±800Vp) high voltage, suitable for high-voltage loads. The voltage gain is digitally adjustable, and commonly used settings can be saved with a single button press, providing you with convenient and simple operational choices. Additionally, the dual-channel high voltage amplifier outputs can be adjusted synchronously and can be used in conjunction with mainstream signal generators to amplify signals.

Function of the Power Amplifier:The power amplifier is the core component of the entire experiment. In this experiment, it provides a stable, low-distortion AC signal with an amplitude of 200Vpp to drive the FBG ultrasonic sensor.

Application Scenarios:Rail flaw detection, health monitoring of long-distance structures such as bridges, photoacoustic endoscopic imaging

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