Verification method for burst pressure of type IV high-pressure hydrogen storage cylinder

Abstract

The application discloses a verification method for burst pressure of a type IV high-pressure hydrogen storage cylinder, and comprises the following steps: establishing a hydrogen storage cylinder geometric model; obtaining material performance parameters of each structure of the hydrogen storage cylinder; applying a design internal pressure load to the hydrogen storage cylinder geometric model to perform internal pressure static load simulation analysis, and obtaining variation rules of stress values of key positions with the internal pressure load; establishing a strain failure criterion suitable for the hydrogen storage cylinder, performing progressive damage failure simulation analysis on the hydrogen storage cylinder, and obtaining variation rules of axial and ring direction displacements of the hydrogen storage cylinder with the internal pressure; determining the burst pressure of the hydrogen storage cylinder through the internal pressure static load simulation analysis and the progressive damage failure simulation analysis respectively, taking the minimum value of the burst pressures obtained through the two methods as the burst strength; and comparing the determined burst strength with a design burst pressure to verify rationality of the hydrogen storage cylinder design. The burst strength calculated by the method is more accurate, and the safety of the hydrogen storage cylinder in use can be further ensured.

Description

A method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder Technical Field

[0001] This invention relates to the field of hydrogen storage cylinder technology, specifically to a method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder. Background Technology

[0002] Hydrogen energy, with its zero-carbon emission characteristics, is considered the ultimate energy source for fuel cell vehicles. Since fuel cell vehicles also require a sufficient gas supply to provide power, hydrogen storage technology is one of the crucial technologies for the widespread application of hydrogen energy. Currently, commonly used hydrogen storage technologies include high-pressure gaseous hydrogen storage, cryogenic liquid hydrogen storage, and metal hydride hydrogen storage. Among these, liquid hydrogen storage has the highest energy density, but its liquefaction requires approximately 30% of its heat of combustion. Metal hydride hydrogen storage suffers from application problems such as slow hydrogen absorption and desorption rates and poor reversible cycle performance. High-pressure gaseous hydrogen storage, on the other hand, offers advantages such as high-density storage, low weight, and low cost. Therefore, high-pressure gaseous hydrogen storage is clearly the most suitable compared to other hydrogen storage methods, which is beneficial for the demonstration and promotion of hydrogen fuel cell vehicles and related hydrogen energy storage and transportation infrastructure.

[0003] For high-pressure gaseous hydrogen storage, high-pressure hydrogen storage cylinders are currently the primary method for storing and releasing hydrogen. These cylinders are classified into four types: Type I (all-metal cylinders), Type II (metal-lined fiber-wound cylinders), Type III (metal-lined fiber-wound cylinders), and Type IV (non-metal-lined fiber-wound cylinders). Fuel cell vehicles mostly use Type III and Type IV cylinders, with Type IV high-pressure hydrogen storage cylinders gradually becoming a research focus. For high-pressure hydrogen storage cylinders, the burst pressure, or burst strength, is a crucial indicator of cylinder safety. Verifying the burst pressure of the designed hydrogen storage cylinder is a fundamental prerequisite for ensuring its safe use.

[0004] Currently, the structure of a Type IV high-pressure hydrogen storage cylinder mainly consists of three parts: a plastic inner liner, a metal connector, and a carbon fiber winding layer. The plastic inner liner primarily serves to store hydrogen and provide a seal; it does not bear the gas pressure. This pressure is mainly borne by the carbon fiber winding layer (including helical and circumferential winding layers). During a hydrogen storage cylinder explosion, the helical winding layer bears the axial pressure, while the helical and circumferential winding layers bear the circumferential pressure. When theoretically verifying the explosion pressure, both axial and circumferential explosion pressures need to be calculated separately, and the minimum value is selected as the theoretical explosion strength of the cylinder. However, the theoretical explosion pressure calculation is performed using simplified and assumed conditions, neglecting the stress on the plastic inner liner. The calculated results deviate from actual results and are only a theoretical engineering estimate with low accuracy. Therefore, it is necessary to study a method for verifying the explosion pressure of high-pressure hydrogen storage cylinders to ensure their safe use. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder, ensuring the safety of the high-pressure hydrogen storage cylinder during use.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder, comprising the following steps:

[0008] (1) Establish a geometric model of a Type IV high-pressure hydrogen storage cylinder, including the inner liner, metal joints and carbon fiber winding layer;

[0009] (2) Obtain the material performance parameters of the inner liner, metal joint and carbon fiber winding layer of the high-pressure hydrogen storage cylinder;

[0010] (3) Based on the established geometric model of the hydrogen storage cylinder, the internal pressure load is applied to simulate the internal pressure static load, and the static stress and static strain of the hydrogen storage cylinder under the action of internal pressure loading are analyzed.

[0011] (4) Based on the initial design internal pressure load applied in step (3), gradually increase the load, analyze the stress and strain distribution of the inner liner, metal joint and carbon fiber winding layer under different pressures, and obtain the variation law of the maximum stress value of each structural component with the internal pressure load.

[0012] (5) Based on the static load simulation of internal pressure in steps (3) and (4), progressive damage failure simulation analysis is carried out to establish a strain failure criterion applicable to type IV high-pressure hydrogen storage cylinders.

[0013] (6) Based on the strain failure criterion established in step (5), a progressive damage failure simulation analysis was performed on the hydrogen storage cylinder.

[0014] (7) Based on the progressive damage failure simulation analysis in step (6), the loading is continued by continuously increasing the pressure. The variation law of damage to each structural component of the hydrogen storage cylinder with internal pressure, as well as the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure, are analyzed.

[0015] (8) The burst pressure of the hydrogen storage cylinder was determined by two methods: internal pressure static load simulation analysis and progressive damage failure simulation analysis. The minimum burst pressure obtained by the two methods was taken as the burst strength of the hydrogen storage cylinder.

[0016] (9) Compare the burst strength of the hydrogen storage cylinder determined in step (8) with the design burst pressure of the hydrogen storage cylinder to verify the rationality and safety of the hydrogen storage cylinder design.

[0017] Furthermore, step (3) specifically includes:

[0018] (31) First, apply a uniformly distributed load under the design pressure to the surface of the inner liner. Then, apply symmetrical constraint boundary conditions in the corresponding directions to the two axial sections of the inner liner and the carbon fiber winding layer. Apply a completely fixed constraint to one end of the bottle mouth and bind the outer side of the inner liner to the inner side of the carbon fiber winding layer.

[0019] (32) Analyze the overall stress distribution law of the hydrogen storage cylinder under internal pressure static load, clarify the stress distribution of the inner liner, metal joints and carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction, determine the position of the maximum stress of each structural component in each direction, and judge whether the stress value is within the allowable stress range.

[0020] (33) Analyze the overall strain distribution law of hydrogen storage cylinder under static load of internal pressure, clarify the elastic strain and plastic strain distribution of inner liner and metal joint, and the strain distribution of carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction.

[0021] Furthermore, the strain failure criterion established in step (5) for hydrogen storage cylinders is as follows:

[0022] Fiber stretching mode

[0023] Fiber compression mode

[0024] Matrix stretching mode

[0025] Matrix compression mode (ε 22 +ε 33 <0):

[0026]

[0027] In the formula, ε 11 ε 22 ε 33 ε 12 ε 13 ε 23 These represent three normal strains and three shear strains, respectively; X t X c These represent the longitudinal tensile and compressive strengths, respectively; Y t Y c These represent the transverse tensile and compressive strengths, respectively; S 12 S 23 For the shear strength; C 11 C 22 C 33 C 12 C 23 is a parameter in the stiffness matrix; α is a factor reflecting the influence of shear stress on fiber tensile damage; μ is a factor reflecting the influence of appropriate compressive load on improving shear resistance.

[0028] Furthermore, step (6) specifically includes:

[0029] Based on the strain failure criterion established in step (5), a stiffness degradation criterion is introduced, and a user material subroutine UMAT for progressive damage of composite materials is written. A progressive damage failure finite element analysis is performed on the hydrogen storage cylinder under the design pressure. The damage distribution of the entire hydrogen storage cylinder and the carbon fiber winding layer is analyzed. The cracking, fiber breakage and delamination of the carbon fiber winding layer are analyzed in detail. The order of damage at different locations and between different layers is revealed, and the direction of damage propagation is clarified.

[0030] Furthermore, step (7) specifically includes:

[0031] Based on progressive damage failure simulation, a continuously increasing pressure method was adopted for loading. Before the pressure was less than 3 / 4 of the design burst pressure, each increase of 2-3 MPa was set as a load step. After the pressure increased to 3 / 4 of the design burst pressure, each increase of 1 MPa was set as a load step. The load substeps were set to be program-controlled until the finite element analysis no longer converged. The variation law of damage of each structural component of the hydrogen storage cylinder with internal pressure was analyzed, and the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure was obtained.

[0032] Furthermore, step (8) specifically includes:

[0033] The method for determining the burst pressure through static load simulation analysis is as follows: Based on the obtained variation law of the maximum stress value of each structural component with internal pressure, plot the stress-internal pressure variation curve of each structural component, analyze the magnitude of the internal pressure of each structural component material under the allowable stress, and take the minimum internal pressure of each structural component material as the burst pressure of the hydrogen storage cylinder.

[0034] The method for determining the burst pressure through progressive damage simulation analysis is as follows: analyze the maximum displacement position and change law of the hydrogen storage cylinder during the pressurization process. When the finite element analysis stops and the fiber damage expansion area reaches its maximum, the load corresponding to this point is the burst pressure of the hydrogen storage cylinder.

[0035] Furthermore, step (9) specifically includes:

[0036] If the burst strength of the hydrogen storage cylinder determined in step (8) is less than the design burst pressure, it indicates that the design is unreasonable and there is a safety problem, and it needs to be redesigned; if the burst strength of the hydrogen storage cylinder determined in step (8) is greater than or equal to the design burst pressure, it indicates that the design is reasonable and passes the safety verification.

[0037] The beneficial effects of this invention are as follows:

[0038] The present invention provides a method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder. This method not only considers the influence of the stress on the plastic inner liner of the hydrogen storage cylinder on its burst pressure, but also establishes a strain failure criterion applicable to hydrogen storage cylinders to more accurately analyze the failure behavior of the carbon fiber winding layer. This makes the burst pressure calculated by the method of the present invention closer to the actual burst pressure during the use of the hydrogen storage cylinder. At the same time, by combining internal pressure static load simulation analysis with progressive damage simulation, the burst pressure can be obtained more accurately, ensuring the safety of the hydrogen storage cylinder in use. Attached Figure Description

[0039] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 is a flowchart of the present invention;

[0041] Figure 2 shows the curve of maximum stress in the inner liner of the hydrogen storage cylinder of Embodiment 1 of the present invention as a function of internal pressure.

[0042] Figure 3 shows the curve of maximum stress of the metal joint of the hydrogen storage cylinder in Embodiment 1 of the present invention as a function of internal pressure.

[0043] Figure 4 shows the curve of maximum stress of the carbon fiber winding layer of the hydrogen storage cylinder in Embodiment 1 of the present invention as a function of internal pressure.

[0044] Figure 5 shows the curves of axial displacement and circumferential displacement of the hydrogen storage cylinder in Embodiment 1 of the present invention as a function of internal pressure. Detailed Implementation

[0045] This invention provides a method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] The present invention will now be described in detail with reference to the accompanying drawings.

[0047] Referring to Figure 1, this embodiment provides a method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder, including the following steps:

[0048] (1) Using modeling software, establish a geometric model of a Type IV high-pressure hydrogen storage cylinder, including the inner liner, metal joints and carbon fiber winding layer;

[0049] In this step, when establishing the geometric model of the hydrogen storage cylinder, since the cylinder structure is axisymmetric, a 1 / 4 model can be established using a rotational stretching method to improve computational efficiency. Then, the carbon fiber winding layer (helical and circumferential winding layers) of the hydrogen storage cylinder is established using the composite material layer plug-in WCM. While establishing the geometric model of the carbon fiber winding layer, the number of finite element layers is optimized simultaneously, merging multiple layers (10 layers or less) into one layer with a thickness equal to the thickness of the multiple layers stacked together. This reduces the number of meshes in the winding layer and improves computational efficiency. To ensure the accuracy of the calculation results, the optimized winding layer calculation model is compared with the model calculation results of the actual number and thickness of winding layers. It was found that using the optimization method for 10 layers or less (including 10 layers) has little impact on the calculation results, while merging more than 10 layers into one layer leads to increased errors. Therefore, merging 10 layers or less into one layer is preferred.

[0050] (2) Obtain the material performance parameters of the inner liner, metal joint and carbon fiber winding layer of the high-pressure hydrogen storage cylinder;

[0051] In this step, the material properties of the inner liner and metal joints of the Type IV high-pressure hydrogen storage cylinder include elastic modulus, tensile strength, elongation at break, etc.; the material properties of the carbon fiber winding layer include Young's modulus, shear modulus, allowable stress, etc. of the carbon fiber winding layer in three directions.

[0052] (3) Based on the established geometric model of the hydrogen storage cylinder, the internal pressure load is applied to simulate the internal pressure static load, and the static stress and static strain of the hydrogen storage cylinder under the action of internal pressure loading are analyzed.

[0053] The specific steps are as follows:

[0054] (31) First, apply a uniformly distributed load under the design pressure to the surface of the inner liner. Then, apply symmetrical constraint boundary conditions in the corresponding directions to the two axial sections of the inner liner and the carbon fiber winding layer. Apply a completely fixed constraint to one end of the bottle mouth and bind the outer side of the inner liner to the inner side of the carbon fiber winding layer.

[0055] (32) Analyze the overall stress distribution law of the hydrogen storage cylinder under internal pressure static load, clarify the stress distribution of the inner liner, metal joints and carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction, determine the position of the maximum stress of each structural component in each direction, and judge whether the stress value is within the allowable stress range.

[0056] (33) Analyze the overall strain distribution law of hydrogen storage cylinder under static load of internal pressure, clarify the elastic strain and plastic strain distribution of inner liner and metal joint, and the strain distribution of carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction.

[0057] (4) Based on the initial design internal pressure load applied in step (3), gradually increase the load, analyze the stress distribution and strain distribution of the inner liner, metal joint and carbon fiber winding layer under different pressures, and obtain the variation law of the maximum stress value of each structural component with the internal pressure load.

[0058] (5) Based on the static load simulation of internal pressure in steps (3) and (4), progressive damage failure simulation analysis is carried out to establish a strain failure criterion applicable to hydrogen storage cylinders.

[0059] The strain failure criterion established in this step, applicable to hydrogen storage cylinders, is for the carbon fiber winding layer (the material of which is carbon fiber epoxy resin). Its strain failure criterion (failure is determined when the calculation result in the following formula is ≥1) is as follows:

[0060] carbon fiber stretching mode

[0061] carbon fiber compression mode

[0062] Epoxy resin stretching mode

[0063] Epoxy resin compression mode (ε 22 +ε 33 <0):

[0064]

[0065] In the formula, ε 11 ε 22 ε 33 ε 12 ε 13 ε 23These represent three normal strains and three shear strains, respectively; X t X c These represent the longitudinal tensile and compressive strengths, respectively; Y t Y c These represent the transverse tensile and compressive strengths, respectively; S 12 S 23 C is the shear strength; 11 C 22 C 33 C 12 C 23 is a parameter in the stiffness matrix; α is a factor reflecting the influence of shear stress on fiber tensile damage; μ is a factor reflecting the influence of appropriate compressive load on improving shear resistance.

[0066] Based on existing composite material failure modes, the above failure criteria also consider the impact of increased material shear resistance caused by appropriate transverse compression on failure, and consider delamination and slippage failure of the inner liner and carbon fiber winding layer, so as to more accurately analyze the failure behavior of the carbon fiber winding layer.

[0067] (6) Based on the strain failure criterion established in step (5), a progressive damage failure simulation analysis was performed on the hydrogen storage cylinder.

[0068] The specific steps are as follows:

[0069] Based on the strain failure criterion established in step (5), a stiffness degradation criterion is introduced, and a user material subroutine UMAT for progressive damage of composite materials is written. A progressive damage failure finite element analysis is performed on the hydrogen storage cylinder under the design pressure. The damage distribution of the entire hydrogen storage cylinder and the carbon fiber winding layer is analyzed. The cracking, fiber breakage and delamination of the carbon fiber winding layer are analyzed in detail. The order of damage at different locations and between different layers is revealed, and the direction of damage propagation is clarified.

[0070] (7) Based on the progressive damage failure simulation analysis in step (6), the loading is continued by continuously increasing the pressure to analyze the variation law of damage of each structural component with internal pressure and the variation law of axial displacement and circumferential displacement of hydrogen storage cylinder with internal pressure.

[0071] The specific steps are as follows:

[0072] Based on progressive damage failure simulation, a continuously increasing pressure method was adopted for loading. Before the pressure was less than 3 / 4 of the design burst pressure, each increase of 2-3 MPa was set as a load step. When the pressure increased to 3 / 4 of the design burst pressure, each increase of 1 MPa was set as a load step. The load substeps were set to be program-controlled until the finite element analysis no longer converged. The variation law of damage of each structural component of the hydrogen storage cylinder with internal pressure was analyzed, and the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure was obtained.

[0073] (8) The burst pressure of the hydrogen storage cylinder was determined by two methods: internal pressure static load simulation analysis and progressive damage failure simulation analysis. The minimum burst pressure obtained by the two methods was taken as the burst strength of the hydrogen storage cylinder.

[0074] The specific steps are as follows:

[0075] The method for determining the burst pressure through static load simulation analysis is as follows: Based on the obtained maximum stress value of each structural component (inner liner, metal joint, carbon fiber winding layer) and the variation law of internal pressure, the stress-internal pressure variation curve of each structural component is plotted, the internal pressure of each structural component material under allowable stress is analyzed, and the minimum internal pressure of each structural component material is taken as the burst pressure of the hydrogen storage cylinder.

[0076] The method for determining the burst pressure through progressive damage simulation analysis is as follows: analyze the maximum displacement position and change law of the hydrogen storage cylinder during the pressurization process. When the finite element analysis stops and the fiber damage expansion area reaches its maximum, the load corresponding to this point is the burst pressure of the hydrogen storage cylinder.

[0077] (9) Compare the burst strength of the hydrogen storage cylinder determined in step (8) with the design burst pressure of the hydrogen storage cylinder to verify the rationality and safety of the hydrogen storage cylinder design. If the determined burst strength of the hydrogen storage cylinder is less than the design burst pressure, it indicates that the design is unreasonable and there is a safety problem, and it needs to be redesigned. If the determined burst strength of the hydrogen storage cylinder is greater than or equal to the design burst pressure, it indicates that the design is reasonable and passes the safety verification.

[0078] Example 1

[0079] This embodiment provides a Type IV high-pressure hydrogen storage cylinder, and uses the method of the present invention to verify its burst pressure for safety.

[0080] The Type IV high-pressure hydrogen storage cylinder of this embodiment is a plastic-lined, fully wound carbon fiber high-pressure hydrogen storage cylinder. It is manufactured using a plastic inner liner and a fully wound carbon fiber structure. The cylinder has a volume of 100L, a working pressure of 70MPa, and a minimum burst pressure design requirement of 170MPa. The plastic inner liner is made of HDPE material with an elastic modulus of 765MPa, a tensile strength of 26MPa, and an elastic modulus of 765MPa. The metal joint is made of aluminum alloy T6061 with an elastic modulus of 78GPa, a tensile strength of 205MPa, and an elongation at break of 0.16. The carbon fiber winding layer is made of carbon fiber epoxy resin with a longitudinal Young's modulus of 157.5GPa, a transverse Young's modulus of 85.6GPa, a longitudinal shear modulus of 2.99GPa, a transverse shear modulus of 4.39GPa, a maximum allowable stress along the fiber direction of 1674MPa, and a maximum allowable stress perpendicular to the fiber direction of 1440MPa.

[0081] Based on the design requirements for the volume, working pressure, and burst pressure of the hydrogen storage cylinder, the structure of the hydrogen storage cylinder was designed using existing technology. Through theoretical calculations and design, the cylinder body diameter was determined to be 300mm, the cylinder body length to be 1495mm, the plastic inner liner thickness to be 7.5mm, the single-layer carbon fiber strip thickness to be 0.325mm, the number of spiral winding layers and circumferential winding layers to be 33 and 44 respectively, the overall thickness of the spiral winding layers and circumferential winding layers to be 11mm and 14mm respectively, and the spiral winding angle to be 19.5°. During a hydrogen storage cylinder burst, the spiral winding layer primarily bears the axial pressure, while the circumferential winding layer does not bear the axial pressure; the spiral winding layer and the circumferential winding layer bear the circumferential pressure.

[0082] Using existing theoretical burst pressure calculation methods, the burst pressure of the aforementioned hydrogen storage cylinder was calculated. In the calculation process, only the helical winding layer was involved in the axial burst pressure calculation, while both the helical and circumferential winding layers were involved in the circumferential burst pressure calculation. Through theoretical derivation, the axial burst pressure of the hydrogen storage cylinder was found to be 170 MPa, and the circumferential burst pressure was found to be 478 MPa. Therefore, the theoretical minimum burst pressure of this hydrogen storage cylinder was determined to be 170 MPa.

[0083] To ensure the safety of the hydrogen storage cylinder designed above, the method of this invention is used to verify and evaluate the burst pressure of the hydrogen storage cylinder. The specific steps are as follows:

[0084] (1) Using Abaqus modeling software, a geometric model of a Type IV high-pressure hydrogen storage cylinder was established, including the inner liner, metal joints, and carbon fiber winding layers. In this step, when establishing the geometric model of the hydrogen storage cylinder, since the cylinder structure is axisymmetric, a 1 / 4 model can be established by rotational stretching to improve computational efficiency. Then, the carbon fiber winding layers (spiral winding layer and circumferential winding layer) of the hydrogen storage cylinder were established using the composite material layer plugin WCM. When establishing the geometric model of the carbon fiber winding layer, the number of finite element layers of the carbon fiber winding layer was optimized. The spiral winding layer was simplified to 4 layers, and the circumferential winding layer was simplified to 5 layers.

[0085] (2) Obtain the material performance parameters of the inner liner, metal joint, and carbon fiber winding layer of the high-pressure hydrogen storage cylinder; that is, obtain the elastic modulus, tensile strength, and elongation at break of the inner liner and metal joint through tensile tests; obtain the Young's modulus, shear modulus, and allowable stress of the carbon fiber winding layer in three directions through tensile tests. Among them, the plastic inner liner material is HDPE material with an elastic modulus of 765MPa, a tensile strength of 26MPa, and an elongation at break of 0.672; the metal joint is aluminum alloy T6061 with an elastic modulus of 78GPa, a tensile strength of 205MPa, and an elongation at break of 0.16; the carbon fiber winding layer is carbon fiber epoxy resin with a longitudinal Young's modulus of 157.5GPa, a transverse Young's modulus of 85.6GPa, a longitudinal shear modulus of 2.99GPa, a transverse shear modulus of 4.39GPa, a maximum allowable stress along the fiber direction of 1674MPa, and a maximum allowable stress perpendicular to the fiber direction of 1440MPa.

[0086] (3) Based on the established geometric model of the hydrogen storage cylinder, the internal pressure load is applied to simulate the internal pressure static load, and the static stress and static strain of the hydrogen storage cylinder under the action of internal pressure loading are analyzed.

[0087] The specific steps are as follows:

[0088] (31) First, apply a uniformly distributed load of 70MPa under the design pressure to the surface of the inner liner. Then, apply symmetrical constraint boundary conditions in the corresponding directions to the two axial sections of the inner liner and the carbon fiber winding layer respectively. Apply a completely fixed constraint to one end of the bottle mouth and bind the outer side of the inner liner to the inner side of the carbon fiber winding layer.

[0089] (32) Analyze the overall stress distribution law of the hydrogen storage cylinder under internal pressure static load, clarify the stress distribution of the inner liner and metal joint, and determine whether the stress value exceeds the corresponding tensile strength; and clarify the stress distribution of the carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction, determine the position of the maximum stress of each structural component in each direction, and determine whether the stress value is within the allowable stress range. If the maximum stress of each structural component exceeds the tensile strength or allowable stress under this load, it indicates that the design of the hydrogen storage cylinder is unqualified. If the maximum stress of each structural component does not exceed the tensile strength or allowable stress under this load, then continue to step (4).

[0090] (33) Analyze the overall strain distribution law of hydrogen storage cylinder under static load of internal pressure, clarify the elastic strain and plastic strain distribution of inner liner and metal joint, and the strain distribution of carbon fiber winding layer along fiber direction and perpendicular to fiber direction.

[0091] (4) Based on the initial design internal pressure load applied in step (3), gradually increase the load, analyze the stress and strain distribution of the inner liner, metal joint and carbon fiber winding layer under different pressures, and obtain the variation law of the maximum stress value of each structural component in each direction with the internal pressure load.

[0092] (5) Based on the static load simulation of internal pressure in steps (3) and (4), progressive damage failure simulation analysis is carried out to establish a strain failure criterion applicable to hydrogen storage cylinders.

[0093] The strain failure criterion established in this step, applicable to hydrogen storage cylinders, is as follows:

[0094] carbon fiber stretching mode

[0095] carbon fiber compression mode

[0096] Epoxy resin stretching mode

[0097] Epoxy resin compression mode (ε 22 +ε 33 <0):

[0098]

[0099] In the formula, ε 11 ε 22 ε 33 ε 12 ε 13 ε 23 These represent three normal strains and three shear strains, respectively; X t X c These represent longitudinal tensile and compressive strengths, respectively; Y t Y c These are the transverse tensile and compressive strengths, respectively; S 12 S 23 C is the shear strength; 11 C 22 C 33 C 12 C 23 is a parameter in the stiffness matrix; α is a factor reflecting the influence of shear stress on fiber tensile damage; μ is a factor reflecting the influence of appropriate compressive load on improving shear resistance.

[0100] (6) Based on the strain failure criterion established in step (5), a progressive damage failure simulation analysis was performed on the hydrogen storage cylinder.

[0101] The specific steps are as follows:

[0102] Based on the strain failure criterion established in step (5), a stiffness degradation criterion is introduced, and a user material subroutine UMAT for progressive damage of composite materials is written. A progressive damage failure finite element analysis is performed on the hydrogen storage cylinder under the design pressure. The damage distribution of the entire hydrogen storage cylinder and the carbon fiber winding layer is analyzed. The cracking, fiber breakage and delamination of the carbon fiber winding layer are analyzed in detail. The order of damage at different locations and between different layers is revealed, and the direction of damage propagation is clarified.

[0103] (7) Based on the progressive damage failure simulation analysis in step (6), the loading is continued by continuously increasing the pressure to analyze the variation law of damage of each structural component with internal pressure and the variation law of axial displacement and circumferential displacement of hydrogen storage cylinder with internal pressure.

[0104] The specific steps are as follows:

[0105] Based on progressive damage failure simulation, a continuously increasing pressure method was adopted for loading. Before the pressure was less than 3 / 4 of the design burst pressure, each 3 MPa increase was set as a load step. After the pressure increased to 3 / 4 of the design burst pressure, each 1 MPa increase was set as a load step. The load substeps were set to be program-controlled until the finite element analysis no longer converged. The variation law of damage of each structural component of the hydrogen storage cylinder with internal pressure was analyzed, and the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure was obtained.

[0106] (8) The burst pressure of the hydrogen storage cylinder was determined by two methods: internal pressure static load simulation analysis and progressive damage failure simulation analysis. The minimum burst pressure obtained by the two methods was taken as the burst strength of the hydrogen storage cylinder.

[0107] The method for determining the burst pressure through static load simulation analysis is as follows: based on the obtained variation law of the maximum stress value of each structural component with the internal pressure, plot the stress-internal pressure variation curve of each structural component, analyze the internal pressure of each structural component material under the allowable stress, and take the minimum internal pressure of each structural component material as the burst pressure of the hydrogen storage cylinder.

[0108] The method for determining the burst pressure through progressive damage simulation analysis is as follows: analyze the maximum displacement position and change law of the hydrogen storage cylinder during the pressurization process, and stop the finite element analysis. The load corresponding to the maximum fiber damage expansion area is the burst pressure of the hydrogen storage cylinder.

[0109] (9) Compare the burst strength of the hydrogen storage cylinder determined in step (8) with the design burst pressure of the hydrogen storage cylinder to verify the rationality and safety of the hydrogen storage cylinder design. If the determined burst strength of the hydrogen storage cylinder is less than the design burst pressure, it indicates that the design is unreasonable and there is a safety problem, and it needs to be redesigned. If the determined burst strength of the hydrogen storage cylinder is greater than or equal to the design burst pressure, it indicates that the design is reasonable and passes the safety verification.

[0110] In this embodiment, the stress variation law of each structural component of the hydrogen storage cylinder with internal pressure is obtained through the above steps (3) and (4), that is, the variation law of the maximum stress of the inner liner, metal joint and carbon fiber winding layer with internal pressure, as shown in Figures 2, 3 and 4 respectively, and the burst pressure obtained by static load simulation analysis is determined according to the method in step (8). As can be seen from Figure 2, although the maximum stress of the inner liner gradually increases with the internal pressure, the increase is very small. When the internal pressure reaches 172MPa, the maximum stress of the inner liner is only 5.66MPa, which is much less than its tensile strength of 26MPa, indicating that the inner liner does not play a major load-bearing role. As can be seen from Figure 3, the maximum stress of the metal joint also gradually increases with the internal pressure, but the increase is still very small. When the internal pressure reaches 172MPa, the maximum stress of the metal joint is 37.85MPa, which is much less than its tensile strength of 205MPa, indicating that the metal joint does not play a major load-bearing role. The carbon fiber winding layer bears the main load. As shown in Figure 4, the internal pressure increases linearly with increasing internal pressure. The greater the internal pressure, the closer the stress on the carbon fiber winding layer in each direction is to the allowable stress value. When the allowable stress along the fiber direction of the carbon fiber winding layer is 1674 MPa, the corresponding internal pressure is about 172 MPa. When the allowable stress along the perpendicular fiber direction of the carbon fiber winding layer is 1440 MPa, the corresponding internal pressure is greater than 172 MPa. Therefore, the burst pressure of the gas cylinder obtained by static load simulation calculation is determined to be 172 MPa.

[0111] In addition, in actual use, since the inner liner and metal joints do not play a major load-bearing role, only the variation law of the maximum stress of the carbon fiber winding layer with the internal pressure can be obtained. However, in the process of establishing the geometric model of the Type IV high-pressure hydrogen storage cylinder, the inner liner and metal joints still need to be introduced. The influence of the stress on the plastic inner liner layer of the hydrogen storage cylinder on its burst pressure cannot be ignored.

[0112] The axial and circumferential displacement curves of the hydrogen storage cylinder as a function of internal pressure were obtained through steps (5), (6), and (7) above, as shown in Figure 5. The burst pressure obtained through the progressive damage simulation analysis method was then determined according to step (8). Figure 5 shows that when the internal pressure reaches 174 MPa and 175 MPa respectively, the axial and circumferential displacements no longer increase, and the fiber damage expansion area reaches its maximum. Therefore, the burst pressure of the cylinder obtained through progressive damage simulation analysis is determined to be 174 MPa.

[0113] The minimum burst pressure obtained by the two methods described above is taken as the burst strength of the hydrogen storage cylinder, which is 172 MPa. This indicates that the cylinder will burst under an internal pressure of 172 MPa. Furthermore, the burst pressure calculated using the method of this invention is greater than the design burst pressure, indicating that the burst pressure design verification is qualified, the safety verification is passed, and the requirements are met.

[0114] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0115] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder, characterized in that, The steps include: (1) establishing a geometric model of a Type IV high-pressure hydrogen storage cylinder, including the inner liner, metal joint, and carbon fiber winding layer; (2) obtaining the material property parameters of the inner liner, metal joint, and carbon fiber winding layer of the high-pressure hydrogen storage cylinder; (3) based on the established geometric model of the hydrogen storage cylinder, applying the design internal pressure load to perform internal pressure static load simulation, and analyzing the static load stress and static load strain of the hydrogen storage cylinder under the internal pressure loading; (4) based on the initial design internal pressure load applied in step (3), gradually increasing the load, analyzing the stress and strain distribution of the inner liner, metal joint, and carbon fiber winding layer under different pressures, and obtaining the variation law of the maximum stress value of each structural component with the internal pressure load; (5) based on the internal pressure static load simulation in steps (3) and (4), performing progressive damage failure simulation analysis, and establishing a strain failure criterion applicable to Type IV high-pressure hydrogen storage cylinders; 6) Based on the strain failure criterion established in step (5), a progressive damage failure simulation analysis is performed on the hydrogen storage cylinder; (7) Based on the progressive damage failure simulation analysis in step (6), the loading is continued by continuously increasing the pressure, and the variation law of damage of each structural component of the hydrogen storage cylinder with internal pressure and the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure are analyzed; (8) The burst pressure of the hydrogen storage cylinder is determined by two methods: internal pressure static load simulation analysis and progressive damage failure simulation analysis, and the minimum burst pressure obtained by the two methods is taken as the burst strength of the hydrogen storage cylinder; (9) The burst strength of the hydrogen storage cylinder determined in step (8) is compared with the design burst pressure of the hydrogen storage cylinder to verify the rationality and safety of the hydrogen storage cylinder design; The strain failure criterion established in step (5) applicable to the hydrogen storage cylinder is: fiber tension mode ： ; Fiber compression mode ： ; Matrix stretching mode ： Matrix compression mode ： In the formula, 、 、 、 、 、 These represent three normal strains and three shear strains, respectively. 、 These are the longitudinal tensile and compressive strengths, respectively. 、 These are the tensile and compressive strengths in the transverse direction, respectively. 、 Shear strength; 、 、 、 These are parameters in the stiffness matrix; To reflect the influence of shear stress on fiber tensile damage; This is a factor that reflects the effect of appropriate compressive load on increasing shear resistance.

2. The method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The specific steps (3) are as follows: (31) First, apply a uniformly distributed load under the design pressure to the surface of the inner liner, and then apply symmetrical constraint boundary conditions in the corresponding directions to the two axial sections of the inner liner and the carbon fiber winding layer respectively. Apply a completely fixed constraint to one end of the bottle mouth, and bind the outer side of the inner liner to the inner side of the carbon fiber winding layer; (32) Analyze the overall stress distribution law of the hydrogen storage cylinder under the action of internal pressure static load, clarify the stress distribution of the inner liner, the metal joint, and the stress distribution of the carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction, determine the maximum stress value of each structural component in each direction, and judge whether the stress value is within the allowable stress range; (33) Analyze the overall strain distribution law of the hydrogen storage cylinder under the action of internal pressure static load, clarify the elastic strain and plastic strain distribution of the inner liner and the metal joint, and the strain distribution of the carbon fiber winding layer along the fiber direction and perpendicular to the fiber direction.

3. The method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The specific steps (6) are as follows: Based on the strain failure criterion established in step (5), a stiffness degradation criterion is introduced, a user material subroutine for progressive damage of composite materials is written, progressive damage failure finite element analysis is performed on the hydrogen storage cylinder under the design pressure, the damage distribution of the hydrogen storage cylinder as a whole and the carbon fiber winding layer is analyzed, the cracking, fiber breakage and delamination of the carbon fiber winding layer are analyzed in detail, the order of damage at different locations and between different layers is revealed, and the direction of damage propagation is clarified.

4. The method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The specific steps (7) are as follows: Based on the progressive damage failure simulation, the loading is carried out by continuously increasing the pressure. Before the pressure is less than 3 / 4 times the design burst pressure, each increase of 2~3 MPa is set as a load step. When the pressure increases to 3 / 4 times the design burst pressure, each increase of 1 MPa is set as a load step. The load substep is set to be program-controlled until the finite element analysis no longer converges. The variation law of damage of each structural component of the hydrogen storage cylinder with internal pressure is analyzed to obtain the variation law of axial displacement and circumferential displacement of the hydrogen storage cylinder with internal pressure.

5. The method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The specific steps (8) are as follows: The method for determining the burst pressure through static load simulation analysis is as follows: Based on the obtained maximum stress value of each structural component and the variation law of internal pressure, the stress-internal pressure variation curve of each structural component is plotted, the internal pressure of each structural component material under allowable stress is analyzed, and the minimum internal pressure of each structural component material is taken as the burst pressure of the hydrogen storage cylinder; The method for determining the burst pressure through progressive damage simulation analysis is as follows: Analyze the maximum displacement position and variation law of the hydrogen storage cylinder during the pressurization process, and the load corresponding to the fiber damage expansion area reaching its maximum when the finite element analysis no longer continues is the burst pressure of the hydrogen storage cylinder.

6. The method for verifying the burst pressure of a Type IV high-pressure hydrogen storage cylinder according to claim 1, characterized in that, The specific steps (9) are as follows: if the burst strength of the hydrogen storage cylinder determined in step (8) is less than the design burst pressure, it indicates that the design is unreasonable and there is a safety problem, and it needs to be redesigned; if the burst strength of the hydrogen storage cylinder determined in step (8) is greater than or equal to the design burst pressure, it indicates that the design is reasonable and passes the safety verification.

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