Application Cases

Experiment Title: Research on the Principle and System of Nonlinear Ultrasonic Testing for Duct Grouting

Research Directions:
Selecting applicable principles and methods for nonlinear ultrasonic testing, determining signal processing approaches to extract effective harmonic features, establishing a nonlinear ultrasonic testing system, and optimizing key testing parameters to ensure detection effectiveness.

Experimental Objectives:
To develop a nonlinear ultrasonic testing technical system tailored for the detection of micro-defects in prestressed concrete beam duct grouting, and to provide theoretical support, equipment, and parameter standards for subsequent micro-defect identification under different working conditions (e.g., insufficient grout, inadequate stabilization time).

Testing Equipment:
Signal generator, ATA-2082 high-voltage amplifier, ultrasonic transmitting transducer, receiving transducer, concrete specimen, oscilloscope, PC.

Experimental Procedure:
During testing, the electrical signal generated by the signal generator, due to its low energy, must be amplified by a power amplifier to enhance the amplitude of each ultrasonic harmonic order and improve testing effectiveness. The amplified electrical signal is then transmitted to the transmitting ultrasonic transducer, which converts it into an acoustic signal that propagates through the concrete specimen. The acoustic signal, carrying information about internal damage within the specimen, is received by the receiving transducer, which converts it back into an electrical signal. This signal is then acquired by an oscilloscope. Given the limited data processing accuracy and inconvenient storage of the oscilloscope, it is typically connected directly to a computer for real-time operation and processing, or the signal data is stored via an external USB drive and processed uniformly on a computer after testing.

Figure 1: Experimental Setup of the Vibration Modulation Method

Figure 2: Schematic Diagram of the Nonlinear Ultrasonic Testing System

Experimental Results:

1. By solving the one-dimensional wave equation for longitudinal ultrasonic wave propagation in solid media, a method for calculating the nonlinear coefficient was derived. This method involves linear fitting using the amplitudes of the first and second harmonic waves. After comparing three testing approaches, the finite amplitude method was selected for subsequent experimental research.

2. Based on实测 data from cubic specimens (200×200×200 mm³) prepared with the same mix proportion, the incident ultrasonic frequency for nonlinear ultrasonic testing of prestressed concrete beam specimens was determined to be 45 kHz, with a sinusoidal waveform selected as the excitation signal.

3. The method of obtaining the relative nonlinear coefficient by incrementally increasing the gain voltage, acquiring the corresponding first and second harmonic amplitudes, and then fitting these values using the least squares method was proven feasible, with a linear correlation coefficient exceeding 0.9.

   
   

Figure 3: Variation of Harmonic Amplitudes under Different Gain Voltages

Product Recommendation: ATA-2082 High-Voltage Amplifier

Figure: ATA-2082 High-Voltage Amplifier Specifications and Parameters

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