# US 2019/0170698 A1 · Distributed sensing fiber acoustic emission fusion sensing system and running method

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- Number: US 2019/0170698 A1
- Document ID: US20190170698A1
- Status: Published application
- Kind: A1
- Application number: 15/831,485
- Filed: 2017-12-05
- Published: 2019-06-06
- Earliest claimed: 2017-12-05
- Assignees: Hohai University
- Applicants: Hohai University
- Inventors: Huaizhi Su; Meng Yang; Chongshi Gu
- Web page: https://patentgrep.com/patent/US20190170698A1

## CPC

- G01N 29/14: using acoustic emission techniques {(echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00)}
- G01N 29/2418: {using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics (photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046)}
- G01N 29/326: {compensating for temperature variations}
- G02B 6/022: {using mechanical stress, e.g. tuning by compression or elongation, special geometrical shapes such as "dog-bone" or taper (G02B6/02204 takes precedence; optical modulation using photo-elastic effect G02F1/0131)}
- G01N 2291/0258: Structural degradation, e.g. fatigue of composites, ageing of oils
- G02B 6/4415: {Cables for special applications (G02B6/4429, G02B6/4439, G02B6/4479 take precedence)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

A distributed sensing fiber acoustic emission fusion sensing system includes a sensing fiber temperature-sensitive compensation device and a sensing fiber acoustic emission demodulation device. A sensing fiber in the sensing fiber temperature-sensitive compensation device after being compensated enters the sensing fiber acoustic emission demodulation device.

## Claims

### Claim 1

A Distributed Sensing Fiber Acoustic Emission Fusion sensing system, comprising a sensing fiber temperature-sensitive compensation device and a sensing fiber acoustic emission demodulation device, wherein a sensing fiber starts from the sensing fiber acoustic emission demodulation device, passes through the sensing fiber temperature-sensitive compensation device, and finally returns to the sensing fiber acoustic emission demodulation device, and a head and a tail of the sensing fiber in the sensing fiber temperature-sensitive compensation device need to be connected with the sensing fiber acoustic emission demodulation device;
the sensing fiber temperature-sensitive compensation device comprises a fiber-carrying guide module and a temperature-sensitive compensation module, a first sensing fiber, a second sensing fiber and a third sensing fiber pass through the fiber-carrying guide module, the fiber-carrying guide module is provided with built-in fiber-fixing modules for fixing the first sensing fiber and the third sensing fiber, the first sensing fiber and the third sensing fiber are fixed by the built-in fiber-fixing modules and then disposed in parallel with the second sensing fiber; the first sensing fiber and the third sensing fiber are arranged on an upper surface of a circular arc-shaped housing, the second sensing fiber passes through the temperature compensation device and then is fixed on another fiber-carrying guide module, and the first sensing fiber the third sensing fiber are fixed on the fiber-carrying guide module through another pair of built-in fiber-fixing modules; and
the sensing fiber acoustic emission demodulation device comprises a driving power source, a mode-locked laser, a femtosecond laser optical frequency comb, a pulse modulator, a wavelength division multiplexer, an optical path coupler, an amplifier, a receiver, a detector, a controller, a concrete structure safety behavior evaluation system, an acoustic emission signal, a Reyleigh optical receiver, a Brilliouin optical receiver, and an optical splitter; the output end of the driving power source is connected with the input end of the mode-locked laser, the input end of the driving power source is connected with the output end of the controller, the mode-locked laser is connected with the femtosecond laser optical frequency comb, the pulse modulator and the wavelength division multiplexer in sequence, the output end of the wavelength division multiplexer is respectively connected with the input end of the optical splitter and the input end of the optical path coupler, the output end of the optical splitter is respectively connected with the input end of the Reyleigh optical receiver and the input end of the Brilliouin optical receiver, the output end of the Reyleigh optical receiver and the output end of the Brilliouin optical receiver are connected with the input end of the controller, the output end of the optical path coupler is connected with the input end of the amplifier and the input end of the receiver, the output end of the receiver is connected with the input end of the detector, the output end of the detector is connected with the input end of the controller, the output end of the amplifier is connected with a fiber acoustic emission sensing device, and the output end of the controller is connected with the concrete structure safety behavior evaluation system.

### Claim 2 (depends on 1)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 1, wherein the fiber acoustic emission sensing device comprises a base plate, and a first side plate and a second side plate fixedly connected with two sides of the base plate, the top portion of the first side plate is connected with the top portion of the second side plate through an arc-shaped fiber-carrying channel, and a main common cavity is formed by the base plate, the first side plate, the second side plate and the arc-shaped fiber-carrying channel; the top portions of the first side plate and the second side plate are respectively hinged with a first arc-shaped cover and a second arc-shaped cover, the lower end surface of the first arc-shaped cover is fixedly connected with a first arc-shaped pressing body, the lower end surface of the second arc-shaped cover is fixedly provided with a second arc-shaped pressing body, a fourth sensing fiber in the arc-shaped fiber-carrying channel is arranged under the first arc-shaped pressing body, a fifth sensing fiber is arranged under the second arc-shaped pressing body, and the first arc-shaped cover is connected with the second arc-shaped cover through a locking device; after the first arc-shaped cover and the second arc-shaped cover are rotated to tightly press the fourth sensing fiber and the fifth sensing fiber through the first arc-shaped pressing body and the second arc-shaped pressing body, the first arc-shaped cover and the second arc-shaped cover are locked through the locking device.

### Claim 3 (depends on 2)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 2, wherein a plurality of first through holes are arranged on the first side plate along the axis direction of the first sensing fiber, and a plurality of second through holes are arranged on the second side plate along the axis direction of the second sensing fiber.

### Claim 4 (depends on 3)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 3, wherein the first through hole is a common cavity circular hole, the section of the common cavity circular hole is a circular hole, the second through hole is a common cavity hexagonal hole, the section of the common cavity hexagonal hole is a hexagonal hole, and both the first through hole and the second through hole are in an odd number.

### Claim 5 (depends on 1)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 1, wherein the fiber-carrying guide module comprises a fiber holding-carrying table, an upper fiber-holding groove, a middle fiber-holding groove, a lower fiber-holding groove, a transition holding table section, an upper wedge-shaped holding table section and a lower wedge-shaped holding table section, wherein the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove are arranged in the fiber holding-carrying table from top to bottom in sequence, the first sensing fiber, the second sensing fiber and the third sensing fiber are fixed in the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove in sequence, and the fiber holding-carrying table is connected with the upper wedge-shaped holding table section and the lower wedge-shaped holding table section through the transition holding table section.

### Claim 6 (depends on 5)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 5, wherein the built-in fiber-fixing module comprises an upper arc end fastener, a lower arc end fastener, a fiber-locking thread column, an upper horizontal thread control column, a lower horizontal thread control column, a boss and a pair of sliding blocks; the boss is arranged on the upper wedge-shaped holding table section and the lower wedge-shaped holding table section, the boss is removably connected with the upper horizontal thread control column and the lower horizontal thread control column, the upper horizontal thread control column and the lower horizontal thread control column are in threaded connection with the pair of sliding blocks respectively, the fiber-locking thread column is in threaded connection with one of the sliding blocks, and the lower arc end fastener is fixedly connected with the other sliding block.

### Claim 7 (depends on 6)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 6, wherein the circular arc-shaped housing comprises three layers, an outermost layer is a special composite material layer, a middle layer is a metal compartment layer, and an innermost layer is an inner composite material layer.

### Claim 8 (depends on 7)

The distributed sensing fiber acoustic emission fusion sensing system according to claim 7, wherein the temperature-sensitive compensation module comprises a pair of ellipsoids made of arc-shaped composite material, the two ellipsoids are arranged at the two ends of the circular arc-shaped housing, the ellipsoid is internally provided with a first fiber-feeding pipe for the second sensing fiber to pass through, a lageniform hoist body made of composite material is arranged between the two ellipsoids, the hoist body is internally provided with a second fiber-feeding pipe, the second sensing fiber passes through the first fiber-feeding pipe, the second fiber-feeding pipe and another first fiber-feeding pipe in sequence, and both the ellipsoids and the hoist body are supported in the circular arc-shaped housing through support columns.

### Claim 9 (depends on 1)

A running method of the distributed sensing fiber acoustic emission fusion sensing system according to claim 1, comprising:
first step: equipping three pieces of sensing fibers to be monitored as the first sensing fiber, the second sensing fiber and the third sensing fiber, preparing the circular arc-shaped housing, equipping the special composite material and the ellipsoids, and requiring the first sensing fiber and the third sensing fiber to pass through the special composite material-layer, respectively passing the first sensing fiber, the second sensing fiber and the third sensing fiber through the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove on the fiber holding-carrying table at the initial end of the sensing fiber temperature-sensitive compensation packaging device, and respectively injecting glue into the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove, fixing the initial ends of the three pieces of sensing fibers penetrated into the sensing fiber temperature-sensitive compensation packaging device, then transiting the first sensing fiber and the third sensing fiber to the transition holding table section by a certain radian, and packaging the first fiber-feeding pipe and the second fiber-feeding pipe;
second step: transiting the first sensing fiber to the boss by a 60-degree included angle with a horizontal plane, and injecting glue in the boss to fix the first sensing fiber again, driving the upper arc end fastener to move by the fiber-locking thread columns distributed at the head and tail ends, extending and fixing the first sensing fiber under a pre-tensioning stress, and injecting glue in the circular arc-shaped housing to lay the first sensing fiber into the special composite material layer contacted therewith, laying the second sensing fiber and the third sensing fiber in the same way, passing the first sensing fiber, the second sensing fiber and the third sensing fiber through the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove on the fiber holding-carrying table at the tail end of the sensing fiber temperature-sensitive compensation packaging device, and injecting glue in the upper fiber-holding groove, the middle fiber-holding groove and the lower fiber-holding groove, so as to complete a sensing fiber temperature-desensitized operation and embed the device to finally lay a sensing device;
third step: opening each member of the sensing fiber acoustic emission demodulation device and controlling the controller to start the driving power source, thus exciting the mode-locked laser to generate the femtosecond laser optical frequency comb, and then modulating the femtosecond laser optical frequency comb through the pulse modulator, the wavelength division multiplexer and the optical splitter;
fourth step: in order to remove the temperature interference more accurately, averaging strain values of the first sensing fiber and the third sensing fiber processed by an upper special composite material and a lower special composite material as the relatively accurate strain value of the sensing fiber acquired for the first time, then using the strain value of the second sensing fiber to amend the average value of the strain values of the first sensing fiber and the third sensing fiber as the final strain value monitored by the sensing fiber without the temperature interference; and
fifth step: an acoustic emission signal being generated when some part of the structure to be monitored is damaged, the acoustic emission signal being transduced into the common cavity circular hole, the common cavity hexagonal hole and the main common cavity, and Rayleigh scattering light information and Brillouin scattering light information in the sensing fiber being affected, receiving and detecting the femtosecond laser optical frequency comb of the changed Rayleigh scattering light information and the changed Brillouin scattering light information through the Rayleigh optical receiver, the Brillouin optical receiver and the receiver, then collecting the information into the concrete structure safety behavior evaluation system through the controller for analysis and research, and evaluating and analyzing the information like the damaged position and degree of the structure.