METHOD AND SYSTEM OF THERMOGRAPHIC NON-DESTRUCTIVE INSPECTION FOR DETECTING AND MEASURING VOLUMETRIC DEFECTS IN COMPOSITE MATERIAL STRUCTURES

摘要

A thermographic non-destructive inspection method of a structure, comprising the steps of: generating a modulated thermal wave in the direction of the structure; generating a temperature signal identifying a phase shift between the modulated thermal wave and a return thermal wave emitted from the structure; processing the temperature signal to obtain a first sub-signal related to the phase of the first harmonic of the temperature signal; identifying a first dimension of said defect as a function of the phase of the first harmonic of the temperature signal; calculating a first and a second intermediate parameter, ΔΦ1 for the first harmonic and ΔΦ2 for the third harmonic of the temperature signal, by calculating the difference, in degrees, between the phase value inside the zone with a defect and the phase value, absolute or mean of a plurality of points, of the undamaged zone close to the defect; and identifying a second dimension of the defect as a function of the first dimension and of the intermediate parameters ΔΦ1 and ΔΦ2.

主权项

1. A thermographic non-destructive inspection method of a composite material structure (4), including an incidence surface and a bottom surface arranged at a distance from the incidence surface for detecting and measuring at least one volumetric defect that extends from the incidence surface towards the bottom surface, comprising the steps of:
a—supplying a periodic thermal non-sinusoidal wave at the incidence surface; b—generating a temperature signal identifying a phase shift between the modulated thermal wave and a return thermal wave emitted from the structure (4) in response to the modulated thermal wave; c—processing the temperature signal to obtain a first sub-signal related to the phase of the first harmonic of the temperature signal; d—identifying a first dimension (L) of said defect as a function of the phase of the first harmonic of the temperature signal; e—computing a first intermediate parameter (ΔΦ1) by calculating the difference, in degrees, between a minimum value and a maximum value, or between a minimum value and a mean value of a plurality of values in a neighbourhood of the maximum value, of the first sub-signal; characterised by further comprising the steps of: f—processing the temperature signal to obtain a second sub-signal related to the phase of the third harmonic of the temperature signal; g—calculating a second intermediate parameter (ΔΦ2) as the difference, in degrees, between a minimum value and a maximum value, or mean of a plurality of values in a neighbourhood of the maximum value, of the second sub-signal; h—identifying (101) a second dimension of the defect as a function of the first dimension (L), the first intermediate parameter (ΔΦ1) and the second intermediate parameter (ΔΦ2).