Malick Diakhaté

Probabilistic Improvement of Crack Propagation Monitoring by Using Acoustic Emission

In this work, the acoustic emission is used as a measurement technique to detect and locate the progress of the crack tip in a wooden specimen subjected to thermo-hygro-mechanical stresses. Under these stresses, the material response results in the release of energy in the form of transient elastic waves that are recorded by acoustic emission sensors. The post-processing of these acoustic signals is used to detect the position of the crack. There are many parameters that can affect the accuracy of acoustic emission such as noise signals, geometry, wood specie, etc. Consequently, this study combines repetitive tests and probabilistic approaches to characterize uncertainties and improve the acoustic emission protocol. In the experimental program, breaking of graphite mines at various known positions simulated acoustic sources. The differences between the real and detected positions are used to calibrate the tests and to improve the configuration of the sensors.

Acoustic techniques for fatigue cracking mechanisms characterization in hot mix asphalt (HMA)

This article deals with the investigation of the damage process in Asphalt Concrete (AC) using Acoustic Emission technique (AE). The AE response, particularly how it can change as a function of applied stresses, is known to be promising for micro-cracking detection. AE events are correlated with mechanical damage analysis, and allow determining fatigue cracking mechanisms. Nevertheless, the pertinence of AE approaches is closely related to the comprehension of wave propagation phenomenon within the tested material. In fact, wave propagation is affected by attenuation and velocity variation due to the viscoelastic behavior of the AC. For understanding this phenomenon, ultrasonic techniques can be used for determining both the attenuation curves and variation of the propagation velocity.

Cracking and Durability of Composites in a Marine Environment

New renewable marine energy sources are increasingly being pursued as alternatives since they represent an important political and economic challenge for countries. Among these new energy sources, marine tidal turbines are growing considerably. Manufacturers used thick composite material to design most of the tidal turbine blades. To ensure the lifetime of the latter, it is necessary to develop damage models that take into account sea water, and analyse its effects on composite materials.