Centre National De La Recherche Scientifique

Université Pierre Et Marie Curie (paris 6)

Université Pierre Et Marie Curie

Jean-Paul Roger

Albert Claude Boccara

Gilles Tessier

Christian Bergaud

Marie-Claude Potier

Christine Boue

Mihaela Streza

The invention relates to a method for assessing the depth of a crack near the surface of a material, characterized in that said method includes the following steps: heating an area located near the crack using of a heat source () that is periodically modulatable into a heat flow at a controllable frequency, a so-called 'modulation frequency', varying the frequency so as to vary the heat diffusion length between an initial value, less than the distance between the heated area and the crack, and a final value that is greater than the distance between the heated area and the crack; determining the variation, depending on the heat diffusion length, in a function on the basis of at least one derivative, relative to a space variable, of the amplitude of the sinusoidal component of the temperature, on the surface of the material and at the modulation frequency, at each point of a set of points of the crack so as to cause a first area of variation in the function to appear, wherein said function increases at a first nonzero slope, followed by a second variation area, wherein said function increases at a second slope, different from the first slope; and assessing the depth of the crack on the basis of the value of the heat diffusion length at the intersection of the first variation area and the second variation area, the so-called 'intersection length'.

Method for assessing the depth of a crack

The invention concerns an apparatus for parallel detection of the behaviour of mechanical micro-oscillators interacting with the sample (). The amplitude and the phase of resonance of micro-oscillators () are measured with optical means. The invention is characterised in that a source () is active during a fraction 1/n of the period (n being an integer) and of variable phase p/n of the period (p being an integer). Interferences are produced between light beams generated by reflection of incident light beams () and () on the micro-oscillators (). Periodically the micro-oscillators () are displaced by means. The value of the parameter p (p being an integer) is varied and N elementary measurements are integrated to obtain a measurement representing each of the values of p. The phase and amplitude of each micro-oscillator () are calculated on the basis of the representative data obtained for each value of p and this for a large number of accumulations. The invention is applicable in the field of nanotechnologies.

Apparatus for parallel detection of the behaviour of mechanical micro-oscillators

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Cachan, France

Jean-Paul Roger