Defect identification method for polyethylene inner container of high-capacity IV-type tube bundle type gas cylinder

Abstract

The invention belongs to the technical field of high-pressure hydrogen storage containers, and discloses a high-capacity IV-type tube bundle gas cylinder polyethylene liner defect identification method, which comprises the following four steps: visual inspection, digital image correlation (DIC) technology detection, Bragg grating (FBG)-based optical fiber sensing technology detection and finite element analysis (FEA). The defects of the polyethylene inner container can be comprehensively and accurately detected, and the safety and reliability of the hydrogen storage container are improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-pressure hydrogen storage containers, and in particular to a defect identification method for a polyethylene liner of a large-capacity IV-type tube bundle gas cylinder. Background Art

[0002] With the widespread application of hydrogen energy, the demand for large-capacity high-pressure hydrogen storage containers is growing. As an important component of Type IV tube-bundle gas cylinders, the quality of polyethylene liner directly affects the safety and service life of the gas cylinder. However, during the production process, polyethylene liner may have defects such as pores, inclusions, and cracks, which will seriously affect the performance and safety of hydrogen storage containers. Therefore, it is of great significance to develop an effective method for identifying defects in polyethylene liner. Summary of the invention

[0003] The present invention overcomes the shortcomings of the prior art and provides a method for identifying defects in the polyethylene liner of a large-capacity IV-type tube bundle gas cylinder. The method can accurately and quickly detect defects in the liner and improve the safety and reliability of the hydrogen storage container.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: to use visual inspection to preliminarily identify defects in high-density polyethylene liner. A CMOS camera equipped with a macro lens and a high-brightness annular multi-spectral light source is used to perform light inspection and image acquisition on the high-density polyethylene liner, and the pores and inclusion defects in the image are automatically detected by image processing technology. This method is suitable for quality control in the production stage.

[0005] The fiber optic sensing technology based on Bragg grating (FBG) is used to measure the local strain of high-density polyethylene liner. This technology is suitable for monitoring the liner in the production and R&D stages. The fiber optic Bragg grating (FBG) sensor is integrated into the polyethylene liner, and its high sensitivity to strain and temperature changes is used to monitor the local deformation of the liner under pressure changes.

[0006] A digital image correlation measurement system (3DDIC measurement system) was used to perform comprehensive full-field deformation measurement of high-density polyethylene liner to identify the deformation area of ​​the liner wall. The 3DDIC measurement system was used to measure the deformation field of the polyethylene liner surface sprayed with speckles, and the displacement and deformation of the speckle pattern were analyzed to identify the geometric shape and wall thickness non-uniformity of the liner.

[0007] Finite element analysis (FEA) was used to verify the strain field measured by the FBG sensor and the 3DDIC measurement system to ensure the accuracy of the measurement results. A finite element model of the high-density polyethylene liner was established, and the accuracy of the measurement results of the FBG sensor and the 3DDIC measurement system was verified by numerical simulation, and the stress distribution and deformation of the liner under different pressures were analyzed.

[0008] The beneficial effects of the present invention are as follows: the method provided by the present invention is carried out one by one through multiple steps to check various defects of the high-density polyethylene liner, and can effectively identify and evaluate the defects of the high-density polyethylene liner, such as pores, inclusions, uneven wall thickness and defects in the liner / flange connection. Through the use of the 3DDIC measurement system and the FBG sensor, high-precision measurement of the liner deformation can be achieved, providing important data support for the design and optimization of hydrogen storage containers. The application of finite element analysis helps to deeply understand the mechanical behavior of the liner under actual working conditions and provides a theoretical basis for improving the safety and durability of the container. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic diagram of the first viewing angle distribution of the FBG sensor of the present invention on the periphery of the container;

[0010] Figure 2 This is a schematic diagram of the second viewing angle distribution of the FBG sensor of the present invention on the periphery of the container. DETAILED DESCRIPTION

[0011] The following is a detailed description of the steps and methods for detecting the PE liner using the above optical detection technology in conjunction with the embodiments, including the setting of visual inspection, the experimental layout of DIC measurement, the arrangement of FBG sensors and the establishment of FEA model. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] Visual inspection implementation steps, marking vents or inclusion defects: Prepare a CMOS camera equipped with a macro lens and a high-brightness annular multi-spectral light source. Evenly illuminate the polyethylene liner and use the camera to capture images of the liner surface. Use image processing software to analyze the captured images and automatically detect and mark defects such as vents and inclusions.

[0013] Implementation steps of the digital image correlation measurement system (3DDIC measurement system) to determine the deformation field and wall thickness unevenness defects of the liner: Spray a random spot pattern on the surface of the polyethylene liner. Use the 3DDIC measurement system to photograph the surface of the liner with the sprayed spots and record the displacement and deformation of the spots under different pressures. Analyze the data of the 3DDIC measurement system to determine the deformation field and wall thickness unevenness of the liner.

[0014] Implementation steps of fiber optic sensing technology based on Bragg grating (FBG) to determine the local deformation of the liner under pressure: Attach FBG sensors to key locations of the polyethylene liner. Record the strain and temperature change data of the sensor under different pressures through an optical modem. Analyze the data to evaluate the local deformation of the liner under pressure. Specifically, Figure 1 and Figure 2 As shown, the FBG sensors are divided into four groups, including a first FBG sensor 10, a second FBG sensor 20, a third FBG sensor 30 and a fourth FBG sensor 40, wherein the first FBG sensor 10 is evenly distributed along the inner circumferential wall of the container, and there are multiple groups distributed along the axial direction of the container, the second FBG sensor 20 is distributed on the inner wall of the container along the axial direction of the container, the third FBG sensor 30 is arranged at the head of the container, evenly distributed along the inner circumferential wall of the head, and there are multiple groups distributed along its radial direction, and the fourth FBG sensor 40 is arranged at the head of the container, and is arranged on the radial virtual line from the center of the inner wall of the head to its edge.

[0015] Finite element analysis implementation steps, data simulation analysis, and determine whether the 3DDIC measurement system data and FBG sensor data are correct: According to the actual size and material properties of the polyethylene liner, a finite element model is established. Boundary conditions and loads are applied to perform numerical simulation analysis.

[0016] The measurement results of the 3DDIC measurement system and FBG sensor were compared with the finite element analysis results to verify the accuracy of the measurement data.

[0017] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for identifying defects in polyethylene liners of large-capacity IV-type tube-bundle gas cylinders, characterized in that: The method comprises the following steps: Visual inspection, using a CMOS camera equipped with a macro lens and a high-brightness annular multi-spectral light source to illuminate and capture images of the polyethylene liner, and automatically detect impurities and missing defects in the image through image processing technology; Fiber Bragg grating (FBG)-based optical fiber sensing technology detection integrates FBG sensors into polyethylene liner to monitor the local deformation of the liner under pressure changes; Digital image correlation measurement system (3DDIC measurement system) detection, using the 3DDIC measurement system to measure the deformation field of the polyethylene liner surface sprayed with a spot pattern to identify the geometric shape and wall thickness non-uniformity of the liner; Finite element analysis (FEA) was used to establish a finite element model of the polyethylene liner. The accuracy of the measurement results of the 3DDIC measurement system and FBG sensor was verified through numerical simulation, and the stress distribution and deformation of the liner under different pressures were analyzed.

2. A method for identifying defects in polyethylene liners of large-capacity IV-type tube-bundle gas cylinders according to claim 1, characterized in that: During the visual inspection step, image processing software is used to analyze the acquired images and automatically detect and mark pores and inclusions in the liner structure.

3. A method for identifying defects in polyethylene liners of large-capacity IV-type tube-bundle gas cylinders according to claim 1, characterized in that: In the detection step of optical fiber sensing technology based on Bragg grating (FBG), the high sensitivity of FBG sensor to strain and temperature changes is used to monitor the local deformation of the inner tank under pressure.

4. A method for identifying defects in polyethylene liners of large-capacity IV-type tube-bundle gas cylinders according to claim 1, characterized in that: In the detection step of the digital image correlation measurement system (3DDIC measurement system), the deformation field and wall thickness non-uniformity of the liner are identified by analyzing the displacement and deformation of the spot pattern.

5. The method for identifying defects in polyethylene liners of large-capacity IV-type tube-bundle gas cylinders according to claim 1, characterized in that: In the finite element analysis (FEA) step, boundary conditions and loads are applied to perform numerical simulation analysis.

Images