Evaluation of surface cracks of bending concrete using a fully non-contact air-coupled nonlinear ultrasonic technique
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In this paper, a fully non-contact second harmonic generation (SHG) technique using a pair of air-coupled ultrasonic transducers is developed and the feasibility of the technique is investigated through the evaluation of surface cracks of concrete beams subjected to the bending load. The reliability of developed technique is subsequently validated by comparing the non-contact nonlinear ultrasonic measurements with measurement results based on contact-type sensors, where the coefficient of variation of non-contact measurements is averagely about 46% of the contact measurements. The defined nonlinear parameter is found to have a monotonically increasing trend with the growth of concrete crack, and the nonlinear parameter corresponding to the largest crack increases about 7 times from its initial value corresponding to the sample in intact state. In contrast, the increase of linear parameter namely the time-of-flight of surface wave is only about 40%. The difference as high as one order of magnitude verifies the high sensitivity of developed air-coupled SHG technique. With consideration of the easily removable characteristic of air-coupled ultrasonic measurements, the developed SHG technique could be promising for the large scale quality control of concrete structures in engineering practice.
KeywordsNonlinear ultrasonic Air-coupled transducer Rayleigh waves Second harmonic generation Concrete crack
The authors gratefully acknowledge the support from National Natural Science Foundation of China (Grant Nos. 51308020 and 51578032), Major Fundamental Research of China (973 Program, Grant No. 2014CB047003) and Beijing Natural Science Foundation (Grant No. 8162027). The effort made by Mr. Qingdong Wang in part of the experimental work is appreciated.
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Conflict of interest
All authors declare that they have no conflict of interest.
- 19.Maier S (2017) Noncontact nonlinear resonance ultrasound spectroscopy for small metallic samples. Master Thesis, Georgia Institute of TechnologyGoogle Scholar