More about the programme
Ultrasonic waves interact with interface boundaries, grain interstices, pores, inclusions, cracks, etc. and gather substantial information about the details of the geometry and physical properties of the insonified medium.
In the field of micro-damage diagnostics, nonlinear acoustics has experienced a rapid growth in recent years. In fact, whenever mesoscopic features (i.e. mechanical inhomogeneities, whose characteristic spatial scale is very small with respect to the acoustic wavelength, but far exceeds interatomic spacing) are present, acoustic nonlinearity may be up to four orders of magnitude higher than in a perfect monocrystal. Correspondingly, nonlinear parameters are much more sensitive to the properties of micro-inhomogeneities and, in particular, of micro-damages.
Nonlinear dynamic response may manifest itself in a variety of manners, including nonlinear attenuation, harmonic generation, resonant frequency shift, frequency modulation interaction and slow dynamics, all of which are interrelated. Nonlinear behaviour is observed early on in a degradation process, long before linear parameters start to show damage dependent effects. Any increase in the values of nonlinear parameters is univocally related to an increase in micro-structural features in the material considered.
Scientific objectives
Besides the intrinsic scientific interest of the topic, a basic goal of the programme will be the implementation of nonlinear acoustic NDE techniques for micro-damage diagnostics in materials, such as (smart) composites, concrete, rocks, with a wide span of applications in industry, conservation, art, etc. Furthermore, the nonlinear response due to shear dislocations in metals may be exploited for the purpose of quantitative NDE and basic research.
One of the most interesting applications of the programme concerns the repair and conservation of European historical monuments and stone buildings. Our current knowledge of the rate of stone decay is sketchy, and precise predictions of weathering rates in a given environment are still far off. Yet, conservators of our ancient monuments, in order to repair and preserve them, urgently need to be able to measure nondestructively the physical and mechanical properties of the stones and the degree of damage induced by weathering. i.e., they need a tool to enable them to "see" behind the exposed surface and quantify stone quality.
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Workshop support
The NATEMIS Steering Committee considered applications to organise workshops or other science meetings within the remit of the Programme, on the basis of an open call for applications. This call is now closed.
Information on meetings supported by NATEMIS can be found on the NATEMIS Programme website go to website
Short scientific visits
The NATEMIS Programme supported individual short scientific visits of up to one week between research groups in different European countries.
