Application Cases

Experiment Name: Interface Damage Detection Technology for Steel-Concrete Composite Structures

Research Direction: Nondestructive Testing

Test Objective:
A systematic theoretical analysis, experimental study, and parameter analysis were conducted on the interface damage detection method using the MASW (Multichannel Analysis of Surface Waves) approach, and a complete testing procedure was proposed. The research  findings  can further  improve  the nondestructive testing technology for steel-concrete composite structures and can be used to guide the practical engineering application of the MASW method.

Testing Equipment: ATA-2041 High-Voltage Amplifier, Data Acquisition Card, Oscilloscope, Arbitrary Function Waveform Generator.

Experimental Procedure:

Figure: MASW Test Detection System

An MASW detection system was constructed. The hardware  core  of the MASW detection system consists of two parts: the excitation source and the sensors. The main objective is to excite surface waves with rich frequency components, which are then collected by the sensor array. The selection criteria are determined based on theoretical analysis results, while other hardware components are chosen the excitation source and sensors. The software part of the detection system includes signal acquisition/storage and data processing. Signal acquisition needs to be specifically tailored according to the  actual  equipment.

For piezoelectric ceramic excitation, an arbitrary function waveform generator is needed to generate the excitation signal during the initial selection and comparison of excitation signals. Additionally, because the signal generator voltage is relatively low, a voltage amplifier is required to amplify the signal. This study uses an arbitrary function waveform generator and an ATA-2041 voltage amplifier. Together, they can generate arbitrary signals with frequencies up to 500 kHz and voltages up to 200 V.

Multiple groups of experiments were designed based on different simulation methods for interface debonding defects. Three factors – steel plate thickness, plane size of the interface debonding defect, and depth – were used as research variables. An impact hammer (automatic impact hammer) and piezoelectric ceramics were used as excitation sources, while piezoelectric ceramics, ultrasonic probes, and high-frequency acceleration sensors served as vibration sensors. Systematic experimental research was conducted.

Figure: Comparison of Dispersion Curves in Defect Area

Experimental Results:

1. In terms of theoretical research, two main factors influencing the dispersion characteristics of steel-concrete composite structures were summarized: steel plate thickness and the elastic modulus of concrete. Through parameter analysis, the differences in dispersion characteristics between bonded areas and debonded areas were compared. The research results indicate that the bonded area exhibits a platform segment reflecting the Rayleigh wave velocity of concrete in the low-frequency range. The overall wave velocity in the debonded area decreases as frequency  decreases , and the wave velocity in the bonded area is generally higher than that in the debonded area, with the most significant difference observed particularly in the platform segment of the bonded area. Referring to research  findings  on the application of the MASW method in the exploration field, the basis for determining the array layout length and array spacing for applying this method to interface debonding detection in steel-concrete composite structures was established.

2. Regarding equipment selection, this study built a multi-channel high-frequency data synchronous acquisition system, providing a hardware foundation for subsequent experimental research based on the MASW method. In addition,  supporting  data acquisition and analysis systems were developed, and systematic software debugging was carried out. Based on this, further optimization and selection experiments for excitation sources and sensors were conducted. The optimal excitation scheme  and sensor models were determined, providing  testing methods for subsequent experimental research to meet detection requirements under different conditions.

3. In experimental research, multiple groups of test components were designed to investigate the influence of factors such as defect length, depth, defect simulation method, and steel plate thickness on detection results. The impact of defect boundary  localization  and array length/spacing on the results was systematically analyzed. A complete set of detection procedures was summarized as follows:

   (1) Determine the array length based on the theoretically range of velocity difference, the relationship between frequency and wavelength in the bonded area, and the minimum resolution of the target defect. It is recommended to ensure the array length is less than half of the maximum wavelength corresponding to the platform segment of the theoretical dispersion curve for the bonded area, while choosing a length 2-4 times the minimum resolution of the target defect.
   (2) Determine the number of channels based on equipment capabilities, preferably using more than 3 channels. When signal quality is poor,  many sensors should be deployed.
   (3) Conduct preliminary tests and adjust parameters. Verify the effectiveness and  accuracy  of the testing system through calibration tests to obtain standard dispersion curves for defect-free and defective areas.
   (4) Begin detection and constantly monitor changes in the dispersion curve. Compare with the standard dispersion curves to determine the presence of defects. Move the array to determine  the defect boundaries.
   (5) After measurement, complete the analysis of the dispersion characteristics of the test data to determine  the extent of the defect area.

   
   

Figure: ATA-2041 High-Voltage Amplifier Specifications and Parameters