Non-linear ultrasonic testing of concrete for crack detection

Online monitoring of damage appearance in concrete is of the main issues for the operators of civil engineering structures. Visual inspections of the structure or destructive testing performed on samples that are taken from the structure are still the most widely used method. These methods are very costly require skilled manpower and specific equipment while being hardly efficient since they can only be performed on restricted area. An alternative is the use of dynamic testing techniques which can be split in two categories: resonant methods are low frequency methods and consists in analyzing the dynamic signature of the structure that are excited by the first the ambient vibrations (wind, traffic…) [1]. However, since such methods lies on large wavelengths, they are only able to detect large defect in the structures. Ultrasonic methods do not suffer from such limitations but work at much higher frequencies. Classical (linear) ultrasonic testing roughly consists in measuring the evolution of the wave propagation velocity or the coda (backscattered) of the arrival ultrasonic waves [2]. These methods present the main advantage of being fast but do not benefit from the non-linear response of cracks to propagating ultrasonic waves [3]. This effect can only be activated with high amplitude signals, which strongly limits the deployment of the method out of the labs. In the present master thesis, it is suggested to benefit from the large ambient and low frequency vibrations that are able to open and close the potential cracks while detecting them by active ultrasonic measurements.

 References

[1] Tondreau, G., & Deraemaeker, A. (2014). Automated data-based damage localization under ambient vibration using local modal filters and dynamic strain measurements: experimental applications. Journal of sound and vibration, 333(26), 7364-7385. doi:10.1016/j.jsv.2014.08.021

[2] Dumoulin, C., Karaiskos, G., Sener, J.-Y., & Deraemaeker, A. (2014). Online monitoring of cracking in concrete structures using embedded piezoelectric transducers. Smart materials and structures, 23(11), 115016. doi:10.1088/0964-1726/23/11/115016

[3] Ulrich, T. J., Sutin, a. M., Guyer, R. a., & Johnson, P. a. (2008). Time reversal and non-linear elastic wave spectroscopy (TR NEWS) techniques. International Journal of Non-Linear Mechanics, 43(3), 209–216. http://doi.org/10.1016/j.ijnonlinmec.2007.12.017

Objectives of the master thesis

The master thesis consists in developing an experimental setup which would be able to excite the first few vibration modes of a concrete beam in which several embedded ultrasonic transducers have been casted and to interrogate these transducers by a harmonic signal at much higher frequencies. The beam is excited with the help of a dynamic shaker by a signal that mimics ambient vibrations a signal (white noise signal). An ultrasonic transducer is user as emitter and is excited by a high frequency harmonic signal, the other transducers are user as receiver. The goal of the master thesis is to study the wave modulation between both vibrations from which it is possible to extract information relative to the presence of a crack [3].

Arnaud Deraemaeker (aderaema@ulb.ac.be)

Co-Supervisor

Cédric Dumoulin(cedumoul@ulb.ac.be)

English/French

Architectural Engineering/Civil Engineering/Mechanical Engineering

The student must have an interest in Structural Dynamics, Cementitious materials and Concrete behavior , basic programming skills in Matlab and an interest in experimental testing.