METHOD AND SYSTEM FOR CONTROLLING THE INTEGRATED HEALTH OF A MECHANICAL STRUCTURE BY DIFFUSE ELASTIC WAVES

• US 20190317056A1
• Filed: 12/15/2017
• Published: 10/17/2019
• Est. Priority Date: 12/15/2016
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Original Assignee: Commissariat a L'Energie Atomique (AES Corporation)
• Inventors: DRUET, Tom, CHAPUIS, Bastien, MOULIN, Emmanuel
• Granted Patent: US 11,460,450 B2
• Time in Patent Office: Days
• CPC Class Codes: G01H 11/08 using piezoelectric devices
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125
• CPC Class Codes: G01M 11/083 by using an optical fiber in contact with the device under test [DUT]
• CPC Class Codes: G01M 5/00 Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings G01M9/00 takes precedence
• CPC Class Codes: G01M 5/0008 of bridges
• CPC Class Codes: G01M 5/0016 of aircraft wings or blades
• CPC Class Codes: G01M 5/0025 of elongated objects, e.g. pipes, masts, towers or railways G01M5/0058 takes precedence
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 5/0091 by using electromagnetic excitation or detection
• CPC Class Codes: G01N 2291/0231 Composite or layered materials
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/0425 Parallel to the surface, e.g. creep waves
• CPC Class Codes: G01N 2291/269 Various geometry objects
• CPC Class Codes: G01N 2291/2694 Wings or other aircraft parts
• CPC Class Codes: G01N 29/14 using acoustic emission techniques echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00
• CPC Class Codes: G01N 29/50 using auto-correlation techniques or cross-correlation techniques

Abstract

A method for monitoring the structural health of a structure that supports guided propagation modes of elastic waves, includes the following steps:

• a) acquiring an ambient noise propagating through the structure by means of at least one pair of non-collocated elastic-wave sensors; b) estimating a function representative of an impulse response of the structure for elastic propagation between the constituent sensors of said pair; c) extracting at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of this function representative of an impulse response; and d) estimating at least one parameter indicative of a mechanical property of a constituent material of the structure from the dispersion curve obtained in step c). A system for implementing such a method is also provided.

Claims

1. A method for monitoring the structural health of a structure that supports guided propagation modes of elastic waves, comprising the following steps:

a) acquiring an ambient noise propagating through the structure by means of at least one pair of non-collocated elastic-wave sensors;

b) estimating, from the ambient noise acquired in step a), a function representative of an impulse response of the structure for elastic propagation between the constituent sensors of said pair;

c) extracting at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of the function representative of an impulse response obtained in step b); and

d) estimating at least one parameter indicative of a mechanical property of a constituent material of the structure from the dispersion curve obtained in step c).

2. The method as claimed in claim 1, wherein the elastic noise is acquired over a duration at least equal to the mixing time of the structure.

3. The method as claimed in claim 1, wherein said step b) is implemented using a method chosen from:

calculation of the correlation of the elastic noise acquired by the sensors of the pair;

the passive-inverse-filter method; and

correlation of the coda of correlations.

4. The method as claimed in claim 1, wherein said step c) comprises calculating the time-of-flight, between the sensors of the pair, of a plurality of elastic wave packets having different central frequencies.

5. The method as claimed in claim 1, wherein said step d) is implemented using a method chosen from regression with respect to an analytical model of the dispersion curve and inversion of a numerical model.

6. The method as claimed in claim 1, wherein step d) comprises estimating at least one modulus of elasticity of a constituent material of the structure, or a function of at least one such modulus.

7. The method as claimed in claim 1, wherein step d) is implemented using an iterative method initialized with a value of said parameter at the start of the life of the structure.

8. The method as claimed in claim 1, wherein steps a) to d) are implemented a plurality of times in the course of a period of use of the structure, the method also comprising the following steps:

e) tracking the temporal variation in the parameter estimated in step d); and

f) triggering an alarm when the tracking carried out in step e) indicates an ageing of the structure approaching a critical level.

9. The method as claimed in claim 1, wherein steps a) to d) are implemented a plurality of times using respective pairs of non-collocated sensors, each pair of sensors having a different orientation.

10. The method as claimed in claim 1, also comprising a measurement of the temperature of the structure and the use of the result of this measurement in the implementation of step d).

11. The method as claimed in claim 1, said method being implemented passively.

12. The method as claimed in claim 1, wherein the ambient noise acquired in step a) is recorded and transferred to a data-processing device that is remote from the structure, the following steps of the method being implemented in non-real time by said data-processing device.

13. The method as claimed in claim 1, wherein said structure is of beam, tube, plate or shell type.

14. A system for monitoring the structural health of a structure of plate or shell type, comprising:

at least one pair of non-collocated elastic-wave sensors allowing an ambient noise propagating through the structure to be acquired; and

a data-processing device configured to;

receive, from said sensors, a signal representative of the acquired ambient noise;

estimate, from the ambient noise acquired in step a), a function representative of an impulse response of the structure for the elastic propagation between the constituent sensors of said pair;

extract at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of said function representative of an impulse response; and

estimate at least one parameter indicative of a mechanical property of a constituent material of the structure from said dispersion curve.

15. The system as claimed in claim 14, wherein said elastic-wave sensors are chosen from fiber-optic Bragg-grating sensors, microelectromechanical accelerometers and piezoelectric sensors.

16. The system as claimed in claim 14, also comprising a temperature sensor and wherein said data-processing device is also configured to use a measurement of the temperature of the structure acquired by said sensor to estimate said parameter indicative of a mechanical property of a constituent material of the structure.