Integrated inspection method for implanting optical fiber into fiber-wound gas cylinder

Abstract

The invention discloses an integrated inspection method for implanting an optical fiber into a fiber-wound gas cylinder, and particularly relates to the technical field of composite material pressure vessel quality inspection, which comprises the following steps: step 1, initial state inspection; step 2, carrying out graded pressurization synchronous testing; step 3, capturing failure critical point data; step 4, integrated qualification judgment: judging that the gas cylinder is qualified when meeting the following two conditions at the same time, otherwise, judging that the gas cylinder is unqualified: a) structural strength conditions: the bursting pressure Pb is greater than or equal to rated design bursting pressure or the fatigue cycle index Nb is greater than or equal to rated design fatigue cycle index; b) sensing function conditions: before the pressure reaches 0.9Pb or the cycle index reaches 0.9 Nb, the reflection intensity attenuation delta I / I of all sensing channels is less than or equal to 50% and the data is not interrupted; 5, generating a digital twinborn report; the curve family of the method reflects the continuous distribution rule in the axial direction and the annular direction of the bottle body, and visual recognition of the consistency of the local yield and the overall loading of the structure is achieved.

Description

Technical Field

[0001] This invention belongs to the field of composite material pressure vessel quality inspection technology, specifically relating to an integrated inspection method for fiber-wound gas cylinders with embedded optical fibers. Background Technology

[0002] The Type IV hydrogen storage cylinder, thanks to the high specific strength of carbon fiber composite materials, has become a core carrier for high-pressure hydrogen storage scenarios. However, the complex interlayer structure formed by its multi-axis winding process makes internal damage evolution highly concealed. Traditional factory inspection of composite gas cylinders relies on sampling several cylinders from the same batch for hydrostatic burst tests and fatigue cycle tests. The burst pressure value or fatigue cycle number of the sampled cylinders is used to determine whether the batch of cylinders meets the qualification standards. However, for smart cylinders with integrated fiber optic grating sensors, this traditional method has significant drawbacks: First, the process is fragmented. Existing methods usually separate fiber optic network continuity testing from burst tests, which cannot effectively assess the performance of the sensor network throughout the entire process of the cylinder under pressure until failure. Second, information is missing. Burst tests only obtain the final pressure data, wasting the massive amount of strain and temperature information collected by the fiber optic sensors in real time throughout the loading process. Third, the criteria are singular. Only the absence of structural fracture is used as a criterion, which cannot identify potential problems such as signal attenuation, performance degradation, or premature failure of the sensor network under high pressure, leading to doubts about the reliability of its long-term health monitoring. Summary of the Invention

[0003] To address the aforementioned issues, this invention provides an integrated, efficient, and information-rich factory inspection method, which aims to simultaneously verify the structural integrity of gas cylinders and the functionality of sensor networks, and acquire performance data throughout their entire lifecycle.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] An integrated inspection method for fiber-wound gas cylinders with embedded optical fibers includes the following steps:

[0006] Step 1, Initial state inspection: Read the initial center wavelength λ0 of all fiber optic gratings using an optical fiber demodulator and perform a full-channel continuity test to ensure the optical path is intact. At least 10 sets of center wavelengths of the reflection spectrum should be collected for each grating point and the average value should be taken as the initial value of the center wavelength of that point.

[0007] Step 2, Staged pressurization synchronous test: Place the gas cylinder in the water pressure burst system or fatigue cycle test system, and connect the fiber optic demodulator.

[0008] Step 3: Failure Critical Point Data Acquisition: Continuously pressurize or fatigue cycle until the gas cylinder explodes, and record the explosion pressure P. b Or the number of fatigue cycles N bCapture and store the last stage effective pressure P before cylinder structural failure. f and all corresponding raster data (λ) f I f );

[0009] Step 4, Integrated Qualification Judgment: A gas cylinder is considered qualified if it meets both of the following conditions; otherwise, it is considered unqualified:

[0010] a) Structural strength condition: Burst pressure P b ≥ Rated design burst pressure or fatigue cycle count N b ≥ Rated design fatigue cycle count;

[0011] b) Sensing function conditions: when the pressure reaches 0.9P b Or the number of cycles reaches 0.9N b Previously, the reflection intensity attenuation of all sensing channels was ΔI / I0≤50% and the data was uninterrupted;

[0012] Step 5: Generate a digital twin report: Based on all the data from Steps 1 to 4, generate a family of "pressure-strain" relationship curves with pressure as the independent variable, and attach key criterion data to form a unique digital inspection report for the gas cylinder, thereby assisting in the diagnosis of whether the gas cylinder is qualified.

[0013] As a preferred embodiment of the present invention, the full-channel continuity test in step one is any one or more of the following tests:

[0014] a) Red light pen test: After passing the light through, observe whether the light path at the beginning and end is clear.

[0015] b) Optical power test: Inject optical signal into the optical fiber channel under test using a broadband light source, and measure the output optical power using an optical power meter at the end of the optical fiber. Determine if ΔI / I0≤50% and the data is uninterrupted.

[0016] c) Optical time domain reflectance test: The OTDR emits an optical pulse into the optical fiber and generates a curve of attenuation as a function of distance. The curve is judged to be smooth and has a clear peak at the end before falling into the noise zone.

[0017] As a preferred embodiment of the present invention, in step three, the pressure is increased in stages according to a preset pressure gradient ΔP, with each stage holding for the same time. During the holding period of each pressure plateau, the real-time center wavelength λ of all gratings is simultaneously acquired and recorded. i and reflection intensity I i The pressure gradient ΔP shall not exceed 5% of the rated design burst pressure.

[0018] As a preferred embodiment of the present invention, in the sensing function conditions described in step four, I0 represents the intensity of the grating reflection peak in the initial state.f Let ΔI be the peak intensity of reflection during a certain loading stage. f – I0, I0 and I f Both are obtained by integrating the spectral data acquired by the fiber optic demodulator. The demodulator automatically calculates the amplitude of the reflection peak as the pressure increases from 0 to 0.8P. b During the process, the wavelength shift Δλ of all gratings exhibits a continuous and monotonic correspondence with the pressure value, where Δλ = λ f – λ0.

[0019] As a preferred embodiment of the present invention, in step five, the family of "pressure-strain" relationship curves is obtained by converting the change in wavelength Δλ of each grating center into strain ε, and then plotting it in conjunction with synchronous pressure data. ε = Δλ / (k·λ0), where k is the strain sensitivity coefficient of the fiber optic grating, and Δλ = λ f – λ0.

[0020] As a preferred embodiment of the present invention, the key criterion data in step five includes: the actual burst pressure P of the gas cylinder. b Or the number of fatigue cycles N b Explosion location mode, light intensity attenuation rate ΔI / I0 of each channel, channel failure pressure point, maximum strain value and location, and strain-time drift curve of the entire process.

[0021] As a preferred embodiment of the present invention, the digital twin report mentioned in step five includes a strain field distribution cloud map of the gas cylinder under burst pressure. This cloud map is generated by the last effective pressure P at each grating measuring point before the gas cylinder fails. f Next, the strain values ​​ε of all gratings were collected. i and its spatial position in the bottle coordinate system (x i ,y i It is obtained through two-dimensional interpolation, and its mathematical expression is:

[0022] (1)

[0023] In the formula, For interpolated strain at arbitrary locations; The measured strain is the i-th grating measurement point; Let be the interpolation weight function, satisfying .

[0024] As a preferred technical solution of the present invention Using Green's weighted function:

[0025] (2)

[0026] In the formula, Z is the strain matrix;

[0027]

[0028] .

[0029] As a preferred technical solution of the present invention Using a Gaussian weighting function:

[0030] (3)

[0031] In the formula, σ is the smoothing coefficient, which is determined based on the grating spacing and the size of the gas cylinder.

[0032] As a preferred embodiment of the present invention, the gas cylinder includes a PA11 inner liner 23, a carbon fiber spiral winding layer 22, a carbon fiber circumferential winding layer 24, and a glass fiber winding layer 21. The carbon fiber spiral winding layer 22 and the carbon fiber circumferential winding layer 24 are arranged in multiple overlapping layers. The fiber tilt angle of the carbon fiber spiral winding layer 22 is 10° to 60°, and the fiber tilt angle of the carbon fiber circumferential winding layer 24 is 90°. The circumferentially wound optical fiber 11 and the spirally wound optical fiber 13 are embedded in the gas cylinder body along the winding direction of the carbon fiber circumferential winding layer 24 and the carbon fiber spiral winding layer 22, respectively.

[0033] The beneficial effects of this invention are as follows:

[0034] I. Through integrated pressure-optical synchronous excitation detection, the dual verification of the ultimate performance of the gas cylinder structure and the full life cycle function of the sensor network can be completed simultaneously in a single burst test, which greatly improves the depth of inspection and product reliability.

[0035] Second, this process transforms destructive testing into high-value data assets, generating a digital twin report containing the entire "pressure-strain" relationship and failure field distribution. Through cluster analysis of curves from different distributed grating channels, the non-uniformity of stress and interlayer slip trend in different regions of the bottle can be identified. Compared with traditional single-point strain gauges, the family of curves in this method reflects the continuous distribution pattern along the axial and circumferential directions of the bottle, realizing the visual identification of local yielding and overall loading consistency of the structure.

[0036] Third, the strain field distribution cloud map can accurately locate the failure pressure point and the location of sensor performance degradation, providing precise feedback for production process optimization and product quality traceability, forming a closed-loop quality improvement system of "inspection-analysis-improvement". Attached Figure Description

[0037] Figure 1 This is a flowchart of the integrated inspection process for fiber-wound gas cylinders with embedded optical fibers, according to an embodiment of the present invention.

[0038] Figure 2This is a schematic diagram of the optical fiber layout of the 62L type-four fiber-wound hydrogen storage cylinder according to an embodiment of the present invention.

[0039] Figure 3 This is a cross-sectional schematic diagram of the interlayer of a 62L type IV fiber-wound hydrogen storage cylinder according to an embodiment of the present invention;

[0040] Figure 4 The image shows the single fiber optic grating sensor spectrum of a 62L type IV fiber-wound hydrogen storage cylinder as tested in Embodiment 62 of the present invention.

[0041] Figure 5 This is a diagram of a 62L type IV fiber-wound hydrogen storage spiral layer gas cylinder, obtained from a burst test in an embodiment of the present invention.

[0042] Figure 6 This embodiment of the invention demonstrates the generation of strain contour maps based on Green's function interpolation of a single-layer optical fiber.

[0043] List of identifiers in attached diagrams:

[0044] 1. Optical fiber; 11. Circumferentially wound optical fiber; 12. Circumferentially wound optical fiber grating; 13. Spirally wound optical fiber; 14. Spirally wound optical fiber grating;

[0045] 2. Hydrogen storage cylinder; 21. Fiberglass winding layer; 22. Carbon fiber spiral winding layer; 23. PA11 inner liner; 24. Carbon fiber circumferential winding layer. Detailed Implementation

[0046] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0047] Please see Figure 1-6 This invention provides an integrated inspection method for fiber-wound gas cylinders with embedded optical fibers.

[0048] like Figure 1 As shown, the integrated inspection process for gas cylinders provided by this invention includes:

[0049] Step 1, Initial state test: Under normal temperature and pressure conditions (20°C / standard atmospheric pressure 0.1MPa), read the initial center wavelength λ0 of all fiber optic gratings using an optical fiber demodulator, and perform a full-channel continuity test to ensure the optical path is intact. At least 10 sets of reflection spectrum center wavelengths are collected for each grating point, and the average value is taken as the initial value of the center wavelength of that point.

[0050] Step 2, Staged pressurization synchronous test: Place the gas cylinder in the water pressure burst system or fatigue cycle test system, and connect the fiber optic demodulator.

[0051] Step 3: Failure Critical Point Data Acquisition: Continuously pressurize or fatigue cycle until the gas cylinder explodes, and record the explosion pressure P.b Or the number of fatigue cycles N b Capture and store the last stage effective pressure P before cylinder structural failure. f and all corresponding raster data (λ) f I f );

[0052] Step 4, Integrated Qualification Judgment: A gas cylinder is considered qualified if it meets both of the following conditions; otherwise, it is considered unqualified:

[0053] a) Structural strength condition: Burst pressure P b ≥ Rated design burst pressure or fatigue cycle count N b ≥ Rated design fatigue cycle count;

[0054] b) Sensing function conditions: when the pressure reaches 0.9P b Or the number of cycles reaches 0.9N b Previously, the reflection intensity attenuation of all sensing channels was ΔI / I0≤50% and the data was uninterrupted;

[0055] Step 5: Generate a digital twin report: Based on all the data from Steps 1 to 4, generate a family of "pressure-strain" relationship curves with pressure as the independent variable, and attach key criterion data to form a unique digital inspection report for the gas cylinder, thereby assisting in the diagnosis of whether the gas cylinder is qualified.

[0056] Steps one through three involve destructive testing to collect data from gas cylinders of the same model. Steps four and five involve inspecting each produced gas cylinder to determine if it is up to standard.

[0057] The full-channel continuity test in step one can be any one or more of the following tests:

[0058] a) Red light pen test: After passing the light through, observe whether the light path at the beginning and end is clear.

[0059] b) Optical power test: Inject optical signal into the optical fiber channel under test using a broadband light source, and measure the output optical power using an optical power meter at the end of the optical fiber. Determine if ΔI / I0≤50% and the data is uninterrupted.

[0060] c) Optical time domain reflectance test: The OTDR emits an optical pulse into the optical fiber and generates a curve of attenuation as a function of distance. The curve is judged to be smooth and has a clear peak at the end before falling into the noise zone.

[0061] The specific procedures for the water pressure burst or fatigue cycle test described in step two comply with the relevant requirements for gas cylinder type testing in GB / T 9251-2022 "Water Pressure Test Method for Gas Cylinders" and GB / T 42612-2023 "Compressed Hydrogen Plastic Liner Carbon Fiber Fully Wound Gas Cylinders for Vehicles".

[0062] Effective pressure P in step three f The last stable pressure plateau before structural failure of the gas cylinder, corresponding to a fiber Bragg grating signal that is still continuously solvable; burst pressure P b P represents the maximum pressure value at which the gas cylinder experiences a macroscopic rupture or instantaneous pressure release. f P is determined by the pressure point before the optical signal becomes unstable. b The peak values ​​sampled by the pressure sensor are used together to define the limiting states of the structure and sensing system.

[0063] The number of fatigue cycles N in step three b The fatigue cycle count N is recorded by a cycle counter of a fatigue cycle testing system, and is automatically incremented by one after each round-trip loading cycle between the set minimum and maximum pressures; b This refers to the cumulative number of cycles required for the gas cylinder structure to fail or to reach the designed fatigue cycle count.

[0064] In step three, the pressure is increased in stages according to a preset pressure gradient ΔP, with the same holding time for each stage. During the holding time of each pressure plateau, the real-time center wavelength λ of all gratings is simultaneously acquired and recorded. i and reflection intensity I i The pressure gradient ΔP shall not exceed 5% of the rated design burst pressure.

[0065] In step four, the fatigue cycle test gas cylinder is installed in the fatigue cycle loading system. This system consists of a high-pressure servo pump, a high-frequency solenoid valve, and a pressure closed-loop controller, which can automatically cycle between the set minimum and maximum pressures. The system has a built-in cycle counter that can record the number of complete cycles of the loading-unloading process in real time.

[0066] In step four, the sensing function conditions, I0 represents the intensity of the grating reflection peak in the initial state. f Let ΔI be the peak intensity of reflection during a certain loading stage. f –I0. I0 and I f Both values ​​are obtained by integrating the spectral data acquired by the fiber optic demodulator, which automatically calculates the amplitude of the reflection peak. This is achieved as the pressure increases from 0 to 0.8 P. b During the process, the wavelength shift Δλ of all gratings exhibits a continuous and monotonic correspondence with the pressure value, where Δλ = λ f – λ0 proves that the sensing sensitivity is linear and the sensing function is stable.

[0067] In step five, the family of "pressure-strain" relationship curves is obtained by converting the change in wavelength Δλ at the center of each grating into strain ε, and then plotting it in conjunction with synchronous pressure data. According to the formula ε = Δλ / (k·λ0), k is the strain sensitivity coefficient of the fiber optic grating, where Δλ = λ f– λ0. By analyzing the curve clusters of grating channels with different distributions, the non-uniformity of stress and interlayer slip trend in different regions of the bottle can be identified. Compared with traditional single-point strain gauges, the curve family of this method reflects the continuous distribution law along the axial and circumferential directions of the bottle, realizing the visual identification of local yielding and overall loading consistency.

[0068] The key criterion data in step five includes the actual burst pressure P of the gas cylinder. b Or the number of fatigue cycles N b Explosion location mode, light intensity attenuation rate ΔI / I0 of each channel, channel failure pressure point, maximum strain value and location, and strain-time drift curve of the entire process.

[0069] (1) Bursting pressure P b The maximum pressure value, collected in real time by a high-precision strain gauge pressure sensor, reflects the ultimate load-bearing capacity of the gas cylinder's overall structure.

[0070] (2) Number of fatigue cycles N b The number of cyclic loading cycles recorded by the control system represents the durability of the gas cylinder under high-pressure cycling.

[0071] (3) Explosion location mode: The location of sudden changes in the test video and sensor signal can be determined to reflect the weak area of ​​the structure and the failure mode between layers.

[0072] (4) Light intensity attenuation rate ΔI / I0 of each channel: The ratio of the change in spectral reflection intensity output in real time by the demodulator, which measures the signal stability of the sensor network and the bonding state of the fiber-substrate interface.

[0073] (5) Channel failure pressure point: determined by the pressure corresponding to the interruption of optical signal or the disappearance of reflection peak, reflecting the critical load of local damage or delamination of optical fiber.

[0074] (6) Maximum strain value and location: The peak strain ε calculated from the wavelength drift Δλ max The corresponding grating position reveals the area where the gas cylinder experiences the most concentrated force.

[0075] (7) Full-process strain-time drift curve: generated by synchronous sampling of λ(t) and pressure p(t), reflecting the dynamic strain response law of the gas cylinder during the entire process of loading, pressure holding and failure.

[0076] Step five, the digital twin report, includes a strain field distribution cloud map of the gas cylinder under burst pressure. This cloud map is generated by the last effective pressure P at each grating measuring point before the gas cylinder fails. f Next, the strain values ​​ε of all gratings were collected. i and its spatial position in the bottle coordinate system (x i ,y iIt is obtained through two-dimensional interpolation, and its mathematical expression is:

[0077] (1)

[0078] In the formula:

[0079] · For interpolated strain at arbitrary locations;

[0080] · The measured strain is the i-th grating measurement point;

[0081] · Let be the interpolation weight function, satisfying ;

[0082] · Green's weighted function is commonly used:

[0083] (2)

[0084] In the formula,

[0085] Z is the strain matrix;

[0086]

[0087]

[0088] ·or Using a Gaussian weighting function:

[0089] (3)

[0090] In the formula, σ is the smoothing coefficient, which is determined based on the grating spacing and the size of the gas cylinder.

[0091] This interpolation method maps discrete fiber optic measurement data to a continuous strain field, generating strain cloud maps of the bottle surface to identify local strain concentration areas and potential failure sources.

[0092] like Figure 2 , 3As shown, the gas cylinder of this invention is a typical Type IV composite high-pressure gas cylinder. The Type IV hydrogen storage cylinder includes a PA11 inner liner 23, a carbon fiber spiral winding layer 22, a carbon fiber circumferential winding layer 24, and a glass fiber winding layer 21. Furthermore, the Type IV hydrogen storage cylinder has a designed volume of 62L. The inner liner is made of high-density polyethylene (HDPE) or polyamide material, the middle layer is formed by wet winding of T700 grade carbon fiber / epoxy resin composite material, and the outermost layer is formed by decorative glass fiber / epoxy resin winding. The carbon fiber spiral winding layer 22 and the carbon fiber circumferential winding layer 24 are arranged in multiple overlapping layers. The carbon fiber winding method includes circumferential (fiber tilt angle 90°) and spiral (fiber tilt angle 10°~60°). The circumferentially wound optical fiber 11 and the spirally wound optical fiber 13 are embedded in the gas cylinder body along the winding direction of the carbon fiber circumferential winding layer 24 and the carbon fiber spiral winding layer 22, respectively. A grating array, namely the circumferentially wound optical fiber grating point 12 and the spirally wound optical fiber grating point 14, is arranged in the middle and shoulder of the cylinder body, with typical spacing of 10 mm, 50 mm and 100 mm, to capture the principal strain distribution and local instability response.

[0093] like Figure 4 As shown, during the hydrostatic rupture of a 62L type IV fiber-wound hydrogen storage cylinder in this invention, a fiber optic grating demodulator was used to perform initial benchmark tests and continuity checks on the fiber optic grating. The six-point grating spectrum of the helical layer embedded in the fiber channel, with wavelengths set to 1530nm-1560nm, showed reflectivity greater than 0.8. The spectra showed clear reflection peaks in each channel without crosstalk, indicating good consistency in grating fabrication and packaging, no sudden increase in optical loss after embedding, and intact optical path connection. As the pressure gradually increased, the spectral peaks shifted towards longer wavelengths, indicating that the cylinder pressure caused strain and stretching of the grating, and the wavelength shift was linearly related to the applied pressure. This result verifies that the embedded fiber in the winding layer has a sensitive and highly repeatable strain response, providing a reliable foundation for establishing a family of pressure-strain curves.

[0094] like Figure 5 As shown, the strain-time drift curve of the 62L type IV fiber-wound hydrogen storage cylinder in this invention under complete hydraulic pressure explosion is displayed. The vertical axis represents the micro-strain (με), which is the post-strain ε in the conversion unit. As can be seen from the figure, the strain curve rises in a stepwise manner, corresponding well to the graded pressure increase plateau during the loading process, indicating excellent synchronization between the dynamic response of the fiber optic sensing system and the hydraulic pressure control. The measuring points almost overlap in the initial stage (0–3000 με), indicating that the axial and circumferential strain distribution of the cylinder is uniform, and the structure is in the elastic stage.

[0095] As the pressure gradually increases, the curve shows slight residual strain accumulation after each plateau, indicating that microplastic slip occurs between the composite layers, especially at 0.8 P. b The residual strain then increases significantly. Near the blast stage (pressure > 0.95 P) bThe curves at high-strain monitoring points H25 and H26 rose rapidly and then plummeted, indicating interlayer delamination or fiber breakage in that area. Meanwhile, the low-strain monitoring points H21 and H22 remained stable, suggesting that the failure progressed from the middle of the spiral layer to the transition zone of the end cap (the strain monitoring points are the fiber optic grating points). At the moment of rupture, all channel signals simultaneously returned to zero, verifying the instantaneous overall rupture of the gas cylinder and the complete breakage of the fiber optic network.

[0096] Comprehensive analysis shows that the strain-time curve can intuitively reflect the elastic-plastic transformation, local damage initiation and final failure process of the gas cylinder during the entire process of being compressed, providing a reliable basis for identifying weak areas in the gas cylinder structure and verifying the rationality of the winding stress distribution.

[0097] like Figure 6 As shown in the figure, the strain field distribution cloud map generated by single-layer circumferentially wound optical fiber demonstration data in this embodiment of the invention is based on Green's function interpolation. It can be used to assist in diagnosing whether the gas cylinder in use is qualified. By finding the maximum strain point, it can help determine the location of the failure pressure point; and by judging the failure of the sensing grating point, it can determine the location of sensor performance degradation. The strain field distribution cloud map generated by interpolation not only quantitatively reflects the strain gradient characteristics of the gas cylinder under pressure, but also verifies the spatial calculation capability of the embedded fiber grating sensing array.

[0098] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. An integrated inspection method for fiber-wound gas cylinders with embedded optical fibers, characterized in that, Includes the following steps: Step 1, Initial state inspection: Read the initial center wavelength λ0 of all fiber optic gratings using an optical fiber demodulator and perform a full-channel continuity test to ensure the optical path is intact. At least 10 sets of center wavelengths of the reflection spectrum should be collected for each grating point and the average value should be taken as the initial value of the center wavelength of that point. Step 2, Staged pressurization synchronous test: Place the gas cylinder in the water pressure burst system or fatigue cycle test system, and connect the fiber optic demodulator. Step 3: Failure Critical Point Data Acquisition: Continuously pressurize or fatigue cycle until the gas cylinder explodes, and record the explosion pressure P. b Or the number of fatigue cycles N b Capture and store the last stage effective pressure P before cylinder structural failure. f and all corresponding raster data (λ) f I f ); Step 4, Integrated Qualification Judgment: A gas cylinder is considered qualified if it meets both of the following conditions; otherwise, it is considered unqualified: a) Structural strength condition: Burst pressure P b ≥ Rated design burst pressure or fatigue cycle count N b ≥ Rated design fatigue cycle count; b) Sensing function conditions: when the pressure reaches 0.9P b Or the number of cycles reaches 0.9N b Previously, the reflection intensity attenuation of all sensing channels was ΔI / I0≤50% and the data was uninterrupted; Step 5: Generate a digital twin report: Based on all the data from Steps 1 to 4, generate a family of "pressure-strain" relationship curves with pressure as the independent variable, and attach key criterion data to form a unique digital inspection report for the gas cylinder, thereby assisting in the diagnosis of whether the gas cylinder is qualified.

2. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, The full-channel continuity test mentioned in step one can be any one or more of the following tests: a) Red light pen test: After passing the light through, observe whether the light path at the beginning and end is clear. b) Optical power test: Inject optical signal into the optical fiber channel under test using a broadband light source, and measure the output optical power using an optical power meter at the end of the optical fiber. Determine if ΔI / I0≤50% and the data is uninterrupted. c) Optical time domain reflectance test: The OTDR emits an optical pulse into the optical fiber and generates a curve of attenuation as a function of distance. The curve is judged to be smooth and has a clear peak at the end before falling into the noise zone.

3. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, In step three, the pressure is increased in stages according to a preset pressure gradient ΔP, with the same holding time for each stage. During the holding time of each pressure plateau, the real-time center wavelength λ of all gratings is simultaneously acquired and recorded. i and reflection intensity I i The pressure gradient ΔP shall not exceed 5% of the rated design burst pressure.

4. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, In the sensing function conditions described in step four, I0 is the intensity of the grating reflection peak in the initial state, I f Let ΔI be the peak intensity of reflection during a certain loading stage. f – I0, I0 and I f Both are obtained by integrating the spectral data acquired by the fiber optic demodulator. The demodulator automatically calculates the amplitude of the reflection peak as the pressure increases from 0 to 0.8P. b During the process, the wavelength shift Δλ of all gratings exhibits a continuous and monotonic correspondence with the pressure value, where Δλ = λ f – λ0.

5. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, In step five, the family of "pressure-strain" relationship curves is obtained by converting the change in wavelength Δλ at the center of each grating into strain ε, and then plotting it in pairs with synchronous pressure data. ε = Δλ / (k·λ0), where k is the strain sensitivity coefficient of the fiber optic grating, and Δλ = λ f – λ0.

6. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, The key criterion data mentioned in step five includes: the actual burst pressure P of the gas cylinder. b Or the number of fatigue cycles N b Explosion location mode, light intensity attenuation rate ΔI / I0 of each channel, channel failure pressure point, maximum strain value and location, and strain-time drift curve of the entire process.

7. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, The digital twin report mentioned in step five includes a strain field distribution cloud map of the gas cylinder under burst pressure. This cloud map is generated by the last effective pressure P at each grating measuring point before the gas cylinder fails. f Next, the strain values ​​ε of all gratings were collected. i and its spatial position in the bottle coordinate system (x i ,y i It is obtained through two-dimensional interpolation, and its mathematical expression is: （1） In the formula, For interpolated strain at arbitrary locations; The measured strain is the i-th grating measurement point; Let be the interpolation weight function, satisfying .

8. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 7, characterized in that, Using Green's weighted function: （2） In the formula, Z is the strain matrix; 。 9. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 7, characterized in that, Using a Gaussian weighting function: （3） In the formula, σ is the smoothing coefficient, which is determined based on the grating spacing and the size of the gas cylinder.

10. The integrated inspection method for fiber-wound gas cylinders with embedded optical fibers according to claim 1, characterized in that, The gas cylinder includes a PA11 inner liner 23, a carbon fiber spiral winding layer 22, a carbon fiber circumferential winding layer 24, and a glass fiber winding layer 21. The carbon fiber spiral winding layer 22 and the carbon fiber circumferential winding layer 24 are arranged in multiple overlapping layers. The fiber tilt angle of the carbon fiber spiral winding layer 22 is 10° to 60°, and the fiber tilt angle of the carbon fiber circumferential winding layer 24 is 90°. The circumferentially wound optical fiber 11 and the spirally wound optical fiber 13 are embedded in the gas cylinder body along the winding direction of the carbon fiber circumferential winding layer 24 and the carbon fiber spiral winding layer 22, respectively.

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