A low-temperature working condition static seal structure design method and system, and a static seal structure

Abstract

The application relates to the technical field of industrial sealing, in particular to a low-temperature working condition static sealing structure design method and system. The method is aimed at the failure mechanism of material performance attenuation of a static sealing element under low temperature, is based on a low-temperature-resistant rubber material (according to GB / T 7759.2-2014 test, the compression permanent deformation of the rubber material is 8.7% under the condition of-40 DEG C), and realizes the best matching of optimized static sealing element structure parameters and high-performance low-temperature-resistant sealing materials through systematic structure parameter design optimization, so as to solve the problem that the existing static sealing structure is easy to fail under low temperature, guarantee the reliable operation of GIS equipment under outdoor extreme low-temperature working conditions, and guarantee the sealing reliability of the low-pressure static sealing element within the service life. The application realizes the best matching of the static sealing structure and the high-performance low-temperature-resistant sealing material, and guarantees the sealing reliability of the static sealing element within the service life under the-40 DEG C extreme low-temperature working condition.

Description

Technical Field

[0001] This invention relates to the field of industrial sealing technology, and in particular to a method, system and static sealing structure design for static sealing under low temperature conditions. Background Technology

[0002] As power equipment develops towards higher voltage, higher reliability, and longer lifespan, the requirements for sealing systems in GIS equipment are becoming increasingly stringent. As a core component ensuring stable operation of equipment, the selection and application of seals directly affect the operational safety and service life of the equipment. Moreover, the cross-sectional structure design of seals directly affects the sealing performance, installation portability, and service life of the equipment. Seals with different cross-sectional structures have their own characteristics in terms of applicable scenarios and performance. The cross-sectional structure of the seal is matched with different grooves to complete the seal. Different cross-sectional structures of seals will have significant differences in stress state, contact area between the seal and the groove, and sealing performance in different groove designs.

[0003] Currently, static seals are the primary sealing structure in GIS equipment, and these structures place extremely high demands on the stability, reliability, and service life of the sealing components. In static sealing scenarios, the most widely used sealing component types include O-rings, rectangular rings, and X-rings. For example, EPDM rubber O-rings, due to their excellent weather resistance, aging resistance, and corrosion resistance, can withstand the harsh environments of long-term outdoor operation of GIS equipment and are commonly used in high-pressure static seals. Rectangular rings, with their strong structural stability and excellent extrusion resistance, are also widely used in critical sealing areas of transformers and GIS equipment, such as large flange seals, high-pressure bushing connections, and areas subject to vibration or temperature fluctuations. The unique interface design of X-rings has also been specifically applied in special sealing areas of transformers and GIS equipment.

[0004] Patent document (CN108050324A) discloses a GIS flange sealing assembly, which improves the structure of static seals suitable for room temperature conditions. It uses a pipe thread connection structure to directly achieve relatively high coaxiality, thereby ensuring the effectiveness of the seal and sealing structure. Patent document (CN121118434A) discloses a multi-objective optimization method and device for a multi-layer composite material D-type sealing strip. This method establishes a polynomial approximation model to fit the linear or nonlinear relationship between the influence shadow and the response target, exploring the interaction between the components of the composite material and the influence of the sealing strip cross-sectional structure on sealing performance. However, in extremely cold regions such as Xinjiang where winter temperatures can reach below -40℃, conventional rubber seals are prone to low-temperature hardening and significantly increased compression set, leading to seal failure and SF6 gas leakage, causing power equipment failure and potential safety hazards to the power grid. Existing room-temperature and high-temperature sealing structures are difficult to adapt to low-temperature conditions similar to those below -40℃, resulting in sealing performance failure at low temperatures. Therefore, a highly reliable static sealing system that can adapt to low-temperature conditions in extremely cold environments is urgently needed. Summary of the Invention

[0005] Therefore, it is necessary to provide a design method for static sealing structures under low-temperature conditions to address the above-mentioned problems. This method targets the failure mechanism of "material performance degradation of static seals at low temperatures." Based on the developed low-temperature resistant rubber material (tested according to GB / T 7759.2-2014, the compression set of this rubber material is 8.7% at -40℃), the method achieves optimal matching between the optimized static seal structure parameters and the high-performance low-temperature resistant sealing material through systematic structural parameter optimization. This solves the problem of easy failure of existing static sealing structures at low temperatures, ensures the reliable operation of GIS equipment under extreme outdoor low-temperature conditions, and guarantees the sealing reliability of low-pressure static seals throughout their lifespan.

[0006] In one embodiment, this embodiment provides a method for designing a static sealing structure under low-temperature operating conditions, including: S10 uses equivalent stress, strain distribution, and contact stress as evaluation criteria to determine the optimal sealing ring type for low-pressure static seals through simulation calculations; among them, the optimal sealing ring type is the O-ring. S20, determine the groove size corresponding to the O-ring during the simulation process, and use the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects to establish a simulation analysis model to determine the strain energy density function corresponding to the O-ring under the current low temperature conditions; S30, with the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, an orthogonal experimental design was carried out under low temperature conditions. Based on the orthogonal experimental results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring was established. S40, based on the comparison results of the equivalent stress and maximum contact stress obtained from the strain energy density function and the equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model, determine the fitted quadratic polynomial regression model of the equivalent stress and maximum contact stress. S50. Based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, a 3D response surface plot of the interaction effect of each factor is drawn, and the optimal size parameters of the static seal under the current low temperature condition are determined based on the 3D response surface plot of the interaction effect of each factor.

[0007] Furthermore, S10 includes: S101. Based on the preset cross-sectional compression ratio, volume filling ratio and contact surface roughness of each sealing ring type, the sealing ring type with the smallest maximum equivalent stress is determined by simulation. S102, extract the contact stress diagrams corresponding to each type of sealing ring to determine the type of sealing ring with uniform contact stress distribution during the simulation process; S103, the sealing ring with the smallest maximum equivalent stress, the most reasonable equivalent stress distribution, and the uniform contact stress distribution during the simulation process is determined to be the sealing ring type with the best performance corresponding to the low-pressure static sealing component structure.

[0008] Furthermore, during the simulation analysis in S101, the preset cross-sectional compression rate for each type of sealing ring is 20%, the volume filling rate is 88.5%, and the surface roughness of the contact surface between the seal and the groove is 1.6μm.

[0009] Furthermore, the sealing material of the O-ring is low-temperature shrinkage TR. 10 Rubber materials with a temperature of ≤ -60℃.

[0010] Furthermore, S20 includes: S201, preset the cross-sectional compression ratio and cross-sectional center radius of different O-rings, and the groove size of the O-rings during the simulation process, and keep the preset groove size unchanged. Taking the cross-sectional compression ratio and cross-sectional center radius of the sealing ring as the optimization object, the compression stress simulation test of the sealing material of the O-ring under the current low temperature condition is carried out to obtain the corresponding stress-strain curve. S202, the stress-strain curve is fitted to the corresponding strain energy density function using a two-parameter MR constitutive model; wherein, the obtained strain energy density function is expressed as follows: Where W is the strain energy density function; I1 and I2 are the first and second Green's strain invariants, respectively; C 10 and C 01 These are material constants.

[0011] Furthermore, in S201, the preset cross-sectional compression rates of different O-rings during the simulation are 15%, 18.75%, and 22.5%, respectively, and the center radii of the O-ring cross-section are 35.7 mm, 36.3 mm, and 37 mm. The preset groove dimensions corresponding to the O-rings are: the roughness of the groove contact surface is 1.6 μm, the roughness of the non-sealing surface is 3.2 μm, and the gap between the groove and the baffle is 0.1 mm.

[0012] Furthermore, S30 includes: S301, using the Box-Behnken response surface methodology, with cross-sectional compressibility, cross-sectional center radius and friction coefficient as factors, and maximum equivalent stress and maximum contact stress as response variables, an orthogonal experiment was conducted to obtain the orthogonal experimental results; S302. Based on the orthogonal experimental results, a quadratic polynomial regression analysis was performed using the response surface methodology to fit a quadratic polynomial regression model of the equivalent stress and the maximum contact stress.

[0013] Furthermore, in S302, the quadratic polynomial regression model for the fitted equivalent stress and maximum contact stress is expressed as follows: Where Y1 is the equivalent stress; Y2 is the maximum contact stress; A is the cross-sectional compressibility; B is the center radius of the cross-section; and C is the coefficient of friction.

[0014] In one embodiment, the present invention also provides a static sealing structure design system for low-temperature operating conditions, comprising: The type determination module is used to determine the optimal sealing ring type for low-pressure static seals through simulation calculations, based on equivalent stress, strain distribution, and contact stress as evaluation criteria; among them, the optimal sealing ring type is the O-ring. The simulation calculation module is used to determine the groove size corresponding to the O-ring during the simulation process. Taking the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, a simulation analysis model is established to determine the strain energy density function corresponding to the O-ring under the current low temperature conditions. The orthogonal experiment module is used to design orthogonal experiments under low-temperature conditions, with the cross-sectional compression ratio and volume fill ratio of the O-ring as the optimization objects. Based on the orthogonal experiment results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring is established. The regression model determination module is used to determine the fitted quadratic polynomial regression model of equivalent stress and maximum contact stress based on the comparison results of equivalent stress and maximum contact stress obtained from the strain energy density function and equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model. The parameter determination module is used to draw a 3D response surface plot of the interaction effect of each factor based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, and to determine the optimal size parameters of the static seal under the current low temperature condition based on the drawn 3D response surface plot of the interaction effect of each factor.

[0015] In one embodiment, the present invention also provides a static sealing structure obtained based on the design method described above. The static sealing structure includes an O-ring and a groove that matches the O-ring. The O-ring has a cross-sectional compression ratio of 22.5%, a cross-sectional center radius of 35.7 mm, a wire diameter of 6.2 mm, and a friction coefficient of 0.14. The groove has a volume filling rate of 93.2%, a contact surface roughness of 1.6 μm, a non-sealing surface roughness of 3.2 μm, a depth of 4.7 mm, a width of 6.8 mm, and a groove inlet chamfer of 0.5.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The static sealing structure design method for low-temperature operating conditions provided by this invention adopts a combination of finite element simulation, orthogonal experiment, and response surface optimization. Simulation data replaces empirical selection to determine the O-ring as the optimal cross-sectional structure type for GIS static sealing under low-temperature conditions. A validated "material-structure parameter" matching database of optimal cross-sectional compression ratio and volume fill rate for static sealing components suitable for specific materials and low-temperature conditions is established in an extreme outdoor low-temperature environment of -40℃, minimizing sealing failure caused by temperature changes. This method is applicable to low-pressure static sealing parts such as flanges, air chambers, and end caps of GIS equipment, achieving stable sealing with low leakage rate, low stress concentration, and long service life, meeting the airtightness requirements of GIS. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Furthermore, the accompanying drawings are not drawn to a 1:1 scale, and the relative dimensions of the various components are shown in the drawings only as examples and not necessarily to actual scale.

[0020] Figure 1This is a flowchart illustrating a static sealing structure design method for low-temperature operating conditions provided by the present invention. Figure 2 Schematic diagrams of the static sealing structure types: O-rings, X-rings, and rectangular rings; Figure 3 The equivalent stress contour plot and strain distribution plot are shown for each type of sealing ring during the simulation. Figure 4 The maximum equivalent stress diagrams for each type of sealing ring during the simulation process are shown. Figure 5 The simulation results show the contact stress diagrams for each type of sealing ring. Figure 6 This is a schematic diagram of the structural dimensions corresponding to the preset trench; Figure 7 This is a schematic diagram showing the location of the center radius R1 of the cross-section in the O-ring; Figure 8 The stress-strain curve of the O-ring sealing material at -40℃ is shown. Figure 9 The image shows the fitting effect of the strain-stress curve of the MR model and the O-ring. Figure 10 This is a 3D response surface plot of the interaction effects of various factors. Detailed Implementation

[0021] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] See Figure 1 , Figure 1 This diagram illustrates a flow chart of a static sealing structure design method for low-temperature operating conditions according to an embodiment of the present invention, including: S10 uses equivalent stress, strain distribution, and contact stress as evaluation criteria to determine the optimal sealing ring type for low-pressure static seals through simulation calculations; among them, the optimal sealing ring type is the O-ring. Specifically, although low-pressure static seals withstand relatively low pressure, the high-reliability rubber materials used in them will harden in outdoor environments as cold as -40°C. This causes significant changes in the mechanical properties of the low-pressure static seal material, resulting in an increase in its elastic modulus and a decrease in its elastic recovery ability, thereby further leading to a substantial reduction in the sealing performance of the low-pressure static seal. Therefore, in this embodiment, the optimization target is a low-pressure static seal structure made of a high-reliability, low-temperature resistant rubber material suitable for low-temperature environments. Furthermore, simulation analysis is conducted on the types of sealing rings (O-rings, X-rings, rectangular rings) made using high-reliability rubber materials suitable for low-temperature environments to determine a low-pressure static seal structure that meets the sealing requirements. Preferably, the high-reliability, low-temperature resistant rubber material uses low-temperature shrinkage TR... 10 For rubber materials with a temperature ≤ -60℃, according to GB / T 7759.2-2014, the compression set of this rubber material at -40℃ is 8.7%. Specifically, O-rings, X-rings, and rectangular rings were professionally modeled and analyzed using Abaqus finite element simulation software. During the simulation analysis, equivalent stress, strain distribution, and contact stress were used as evaluation criteria. Scientific simulation calculations were used to compare the mechanical properties and sealing performance of the three types of sealing rings. The structural schematic diagrams of the O-rings, X-rings, and rectangular rings are shown below. Figure 2 As shown.

[0023] Specifically, S10 includes: S101. Based on the preset cross-sectional compression ratio, volume filling ratio and contact surface roughness of each sealing ring type, the sealing ring type with the smallest maximum equivalent stress is determined by simulation. Understandably, in the process of establishing a finite element model using the finite element software Abaqus, the following assumptions are made: (1) the rubber material used in the seal is perfectly elastic and isotropic; (2) the stress relaxation and creep characteristics of the rubber material are ignored; and (3) the influence of temperature and time on the performance of the rubber material is ignored. In this embodiment, when performing simulation analysis, the structural parameters of the seal ring are preset according to the actual working conditions: the cross-sectional compression ratio of the O-ring, X-ring, and rectangular ring is 20%, the volume filling rate is 88.5%, and the surface roughness of the seal and the groove is 1.6 μm. In the simulation modeling analysis, when simulating the O-ring, X-ring, and rectangular ring respectively, the preset cross-sectional compression ratio, volume filling rate, and surface roughness of the seal and the groove are first input, and then the equivalent stress cloud diagram and strain distribution diagram corresponding to each type of seal ring are obtained after simulation calculation, as shown in the figure. Figure 3 As shown. By Figure 3It can be seen that the equivalent stress of the O-ring is mainly concentrated in the central region of the structure, and its equivalent stress and strain distribution tend to be consistent, concentrated in the central region of the seal. The maximum equivalent stress of the rectangular ring is mainly concentrated at the right edge of the seal, and the stress is greater than that of the other two structures. The stress concentration of the X-ring occurs at the arc positions on the left and right sides of the seal. In actual working conditions, this indicates that tearing is likely to occur at this location, and the strain concentration area is also mainly at the arc positions on the left and right sides of the seal, which is not conducive to practical use. In summary, among these three structures, the equivalent stress and strain cloud diagrams of the O-ring are concentrated and reasonable, indicating that the O-ring has a longer service life and is more suitable for practical applications compared to the other three structures. Further... Figure 4 As shown, the maximum equivalent stress diagrams for three structures are presented. Figure 4 It can be seen that the maximum equivalent stress of the three structures, from largest to smallest, is: rectangular ring, X-shaped ring, and O-shaped ring. In summary, the O-shaped ring exhibits the smallest maximum equivalent stress in the simulation analysis, and its equivalent stress contour plot and strain diagram distribution are reasonable, making it more suitable for practical applications.

[0024] S102, extract the contact stress diagrams corresponding to each type of sealing ring to determine the type of sealing ring with uniform contact stress distribution during the simulation process; Specifically, contact stress diagrams of the three types of sealing rings are extracted during the simulation process, such as... Figure 5 As shown. By Figure 5 It can be seen that the contact stress distribution of the rectangular ring exhibits a distinct bimodal structure, with a high peak stress. The contact stress reaches its maximum at the beginning and end of the contact unit, while the stress in the middle is relatively low. The contact stress distribution of the X-ring also shows a bimodal structure, but the peak stress is slightly lower than that of the rectangular ring, and there is no contact pressure in the middle part. This indicates that the concave part in the middle of the X-ring fails to contact the sealing cap, which may lead to unstable sealing performance, especially under varying load conditions. The contact stress distribution of the O-ring is relatively smooth, with the curve showing a single-peak structure. The peak stress is moderate and relatively evenly distributed. Therefore, it can be seen that the stress distribution of the O-ring in the contact area is more uniform, providing a more stable sealing effect.

[0025] S103, the sealing ring with the smallest maximum equivalent stress, the most reasonable equivalent stress distribution, and the uniform contact stress distribution during the simulation process is determined to be the sealing ring type with the best performance corresponding to the low-pressure static sealing component structure.

[0026] Specifically, considering the requirements of low-pressure static sealing structures in GIS equipment, this embodiment uses finite element simulation analysis to analyze three typical static sealing structures: O-rings, rectangular rings, and X-rings. A comprehensive evaluation based on three core performance indicators—equivalent stress, strain distribution, and contact pressure—concludes that the O-ring exhibits the most reasonable equivalent stress distribution and the lowest maximum equivalent stress, effectively preventing fatigue damage caused by stress concentration. Its uniform contact stress distribution forms a stable sealing band, ensuring stable and reliable sealing performance. Furthermore, the O-ring offers advantages such as simple structure, convenient installation, and low cost, resulting in a longer service life in practical applications. Therefore, the O-ring is selected as the optimal sealing ring type for low-pressure static sealing structures in GIS equipment.

[0027] S20, determine the groove size corresponding to the O-ring during the simulation process, and use the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects to establish a simulation analysis model to determine the strain energy density function corresponding to the O-ring; Understandably, the sealing ring and its corresponding groove match to form an integral sealing component for static sealing. The cross-sectional compression ratio of the sealing ring is a crucial factor directly affecting its performance and lifespan (e.g., O-rings). Too low a cross-sectional compression ratio results in poor sealing performance and potential leakage; too high a ratio increases compressive stress, frictional resistance, and the risk of torsional failure, shortening lifespan and even causing assembly difficulties. Therefore, when determining the cross-sectional compression ratio of the sealing ring, sufficient sealing surface contact pressure and minimal friction are considered. Under the premise of ensuring a tight seal, compression deformation should be minimized to avoid permanent deformation. The volumetric fill factor of the sealing component should also not be too high or too low. Excessive fill factor can lead to permanent plastic deformation, while insufficient fill factor can cause distortion, affecting its service life. Therefore, to ensure the long-term reliable operation of GIS equipment in extreme outdoor low-temperature environments such as -40℃, simulation design of the cross-sectional compression ratio and volumetric fill factor of the sealing component is necessary to obtain reasonable values ​​and determine the optimal parameters that balance sealing performance and structural lifespan.

[0028] In this embodiment, after determining that the optimal sealing ring type for the low-pressure static sealing structure of the GIS equipment is an O-ring, the groove form and structural dimensions corresponding to the O-ring must first be specified. Based on the determined groove form and structural dimensions, simulation analysis and design optimization of the key structures of the sealing component (e.g., cross-sectional compression ratio and volumetric filling rate) at -40℃ are carried out. In this embodiment, considering the cost of subsequent experiments and from the perspective of actual production applications, the groove form and structural dimensions corresponding to the O-ring are determined while keeping the set groove structural dimensions unchanged. The groove contact surface roughness is preset to 1.6μm, the non-sealing surface roughness to 3.2μm, the groove depth to 4.7mm, the groove width to 6.8mm, the groove inlet chamfer to 0.5, and the gap between the groove and the baffle to 0.1mm. The dimensions of the groove are as follows: Figure 6 As shown.

[0029] As is well known, under static sealing conditions, the cross-sectional compression ratio of the O-ring is generally between 15% and 30%. However, when the cross-sectional compression ratio is 22.5%, the wire diameter of the O-ring is 6.2 mm, and the area of ​​the sealing ring is 30.2 mm². 2 The cross-sectional area of ​​the trench is 31.96 mm². 2 At this point, the area of ​​the sealing ring is slightly smaller than the cross-sectional area of ​​the groove, so O-rings with a compression rate of 22.5% or higher are not considered. Therefore, in this embodiment, values ​​are taken within the range of 15%-22.5%, and simulation experiments are conducted using three O-rings with different parameters as samples. The cross-sectional compression rates of the three O-rings are pre-set to be 15%, 18.75%, and 22.5%, respectively, and the corresponding wire diameters of the three O-rings are 5.65mm, 5.91mm, and 6.2mm, respectively.

[0030] like Figure 7 As shown, a schematic diagram of the location of the center radius of the O-ring cross-section is given. Figure 7 The innermost circle is the inner diameter d1 of the O-ring. The O-ring can be considered a solid of revolution; therefore, its volume is... Where S is the cross-sectional area, C is the circumference of the cross-section center point rotating around the center of rotation, and because Therefore, the volume of the O-ring rotating body can be expressed as: Understandably, the volumetric fill rate of the seal = volume of the O-ring rotating body / volume of the groove. Therefore, with the groove dimensions remaining constant, the volume fill rate can be adjusted by changing the center radius of the O-ring's cross-section, thereby establishing a reasonable volume fill rate. Specifically, in this embodiment, the center radii of the three O-rings selected are 35.7 mm, 36.3 mm, and 37 mm.

[0031] Therefore, in this embodiment, the above two structural parameters (section compression ratio A and section center radius B) are selected as experimental factors to carry out a 2-factor 3-level orthogonal experimental design, and the parameter levels are shown in Table 1.

[0032] Table 1 Factors and Levels Specifically, S20 includes: S201, preset the cross-sectional compression ratio and cross-sectional center radius of different O-rings during the simulation process, and the groove size of the O-rings, while keeping the preset groove size unchanged. Taking the cross-sectional compression ratio and cross-sectional center radius of the sealing ring as the optimization object, the compression stress test of the sealing material of the O-ring under low temperature conditions is carried out to obtain the corresponding stress-strain curve. Understandably, in extreme low-temperature environments in cold regions, the mechanical properties of low-pressure static seals used in outdoor power equipment undergo significant changes. Rubber materials exhibit hardening and reduced elastic recovery, placing special demands on the structural parameters of the seals. To accurately simulate the performance of sealing materials under extreme low-temperature conditions, this embodiment conducts simulation optimization at a low-temperature condition of -40℃ to determine the optimal dimensional parameters of the low-pressure static seal that best matches the high-reliability rubber sealing material under extreme low-temperature conditions. First, after simulation determined that the O-ring was the best-performing seal, compressive stress tests were performed on the sealing materials of three O-ring samples prepared using high-reliability rubber sealing materials according to GB / T 7757-2009 "Determination of Compressive Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber". The stress-strain curves of different samples are shown below. Figure 8 As shown.

[0033] S202, the stress-strain curve is fitted to the corresponding strain energy density function using a two-parameter MR constitutive model; Understandably, Abaqus simulation software can fit parameters of MR constitutive models of different orders. While a higher order MR constitutive model results in more parameters and more accurate simulation results, increasing the order not only increases the computational load but also makes convergence more difficult. Therefore, it is necessary to select a suitable constitutive model that accurately describes the mechanical properties of the sealing material while minimizing its order. Figure 9 As shown, the two-parameter MR model fits the obtained stress-strain curve well. Therefore, in this embodiment, a two-parameter MR model is used to fit the stress-strain curve to the corresponding strain energy density function. Through the strain energy density function, the finite element method can simulate and calculate the corresponding equivalent stress and contact stress. The obtained strain energy density function is expressed as follows: Where W is the strain energy density function; I1 and I2 are the first and second Green's strain invariants, respectively; C 10 and C 01 These are material constants.

[0034] In this embodiment, during the simulation, compressive stress tests were performed on O-rings with different cross-sectional compression ratios and center radii to obtain stress-strain curves. Then, using a two-parameter MR constitutive model in the simulation software, the stress-strain curves were fitted to the corresponding strain energy density function, allowing direct determination of the material constant C of the low-temperature sealing material used in the O-ring. 10 =1.539MPa, C 01 = -0.137MPa. Understandably, during the simulation, the two-parameter MR constitutive model requires the input of the incompressibility parameter D, and the simulation assumes the material is completely incompressible (D=0).

[0035] S30, with the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, an orthogonal experimental design was carried out under low temperature conditions. Based on the orthogonal experimental results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring was established. Specifically, S30 includes: S301, using the Box-Behnken response surface methodology, with cross-sectional compressibility, cross-sectional center radius and friction coefficient as factors, and maximum equivalent stress and maximum contact stress as response variables, an orthogonal experiment was conducted to obtain the orthogonal experimental results; Specifically, after determining the strain energy density function of the O-ring rubber material at a low temperature of -40℃ through simulation, the maximum contact stress and maximum equivalent stress were used as response variables. Two selected key parameters (section compression ratio and volumetric fill ratio) were considered as random variables. Using Design-Expert 12 analysis software, the Box-Behnken experimental design method was employed to construct and analyze the response surface, further exploring the influence of these key parameters on sealing performance. The experimental scheme was designed using Design-Expert 12 software, and the experimental factors and levels are shown in Table 2. A row for the friction coefficient was added to eliminate error interference.

[0036] Table 2. Factors and Levels in the Box-Behnken Experiment Based on the Box-Behnken experimental factors and levels table, a Box-Behnken experimental scheme was designed, and a simulation experiment was conducted according to the orthogonal rotation experimental design. The values ​​of each influencing factor were taken as independent variables, and the equivalent stress and contact stress were used as evaluation indicators. The orthogonal experimental results are shown in Table 3.

[0037] Table 3. Results of Orthogonal Experiments S302. Based on the orthogonal experimental results, a quadratic polynomial regression analysis was performed using the response surface methodology to fit a quadratic polynomial regression model of the equivalent stress and the maximum contact stress.

[0038] Specifically, in this embodiment, following the established requirements of the Box-Behnken experimental scheme, the maximum and minimum values ​​of key factor parameters (section compression ratio, section center radius) are input. Equivalent stress and maximum contact stress are used as response values. Using the built-in analysis function of Design-Expert 12 software, a significance analysis is conducted on the first-order and second-order terms of structural dimensional factors, as well as the interaction terms between these factors. The fitting results of equivalent stress and maximum contact stress obtained through response surface analysis are detailed in Tables 4 and 5 below.

[0039] Table 4. Variance Table of Equivalent Stress Quadratic Polynomial Model Table 5. Variance Table of the Quadratic Polynomial Model for Maximum Contact Stress Specifically, based on the above analysis of variance table, the quadratic polynomial regression model of the equivalent stress and maximum contact stress obtained from the simulation fitting is expressed by the following formula: Where Y1 is the equivalent stress; Y2 is the maximum contact stress; A is the cross-sectional compressibility; B is the center radius of the cross-section; and C is the coefficient of friction.

[0040] Understandably, the P-value is an indicator of model reliability. A P-value < 0.05 indicates the model is significant, while a P-value > 0.1 indicates the model is not significant. As shown in Tables 4 and 5 (ANOVA tables), the P-values ​​of the quadratic polynomial regression models constructed in this embodiment are all less than 0.05, indicating that the model is significant. In the ANOVA table, the F-value is the ratio of the factor mean square to the error mean square, used to measure the significance of a factor's influence on the response index. The larger the F-value, the more significant the factor's influence on the result, and the higher its contribution to the result. Therefore, the order of influence of factors can be determined based on the magnitude of the F-value. In the above ANOVA table, by comparing the F-values ​​of each factor, it can be concluded that the order of F-values ​​for the influence on equivalent stress and maximum contact stress is compression ratio A, cross-sectional center radius B, and friction coefficient C. Therefore, the order of influence is compression ratio A > cross-sectional center radius B > friction coefficient C.

[0041] S40, based on the comparison results of the equivalent stress and maximum contact stress obtained from the strain energy density function and the equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model, determine the fitted quadratic polynomial regression model of the equivalent stress and maximum contact stress. In this embodiment, during the simulation process, the Abaqus simulation software can directly obtain the equivalent stress and maximum contact stress data through the aforementioned strain energy density function. During the orthogonal experiment, the 17 sets of data from the orthogonal experiment results were input into the Design-Expert 12 software. The software used the Box-Behnken response surface methodology to perform quadratic polynomial regression, which fitted the quadratic polynomial regression model formulas corresponding to the equivalent stress and maximum contact stress. These model formulas can directly calculate the equivalent stress and maximum contact stress. Furthermore, the data values ​​calculated using the regression model formula in the orthogonal experiment are approximately equal to the data values ​​obtained through the strain energy density function in the simulation software. Moreover, the variance analysis results show that the F-values ​​of the regression models for equivalent stress and maximum contact stress are 38.36 and 87.78, respectively, and the P-values ​​are both less than 0.0001, indicating that the fitted quadratic polynomial regression models are highly significant and have a good fit.

[0042] Understandably, the coefficients of the quadratic polynomial regression model formulas corresponding to equivalent stress and maximum contact stress are automatically calculated by the software. They can also be expressed as follows through the regression model formulas: Therefore, we can also obtain: A (section compression ratio) > B (radius of the section center) > C (friction coefficient), consistent with the conclusion of the analysis of variance. This indicates that the quadratic polynomial regression model corresponding to the fitted equivalent stress and maximum contact stress is highly significant and can accurately predict the stress distribution of the seal. The software can automatically calculate the equivalent stress and maximum contact stress directly from the fitted regression model.

[0043] S50. Based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, a 3D response surface plot of the interaction effect of each factor is drawn, and the optimal size parameters of the seal under the current temperature condition are determined based on the 3D response surface plot of the interaction effect of each factor.

[0044] Specifically, after fitting the quadratic polynomial regression model of equivalent stress and maximum contact stress, a 3D response surface plot of the interaction effects of various factors can be drawn based on the analysis results of the regression model, such as... Figure 10 As shown. Based on the 3D response surface plot, with the goal of reducing equivalent stress and increasing maximum contact stress, the optimal dimensional parameters of the seal under the current temperature condition of -40℃ were obtained using the Box-Behnken experimental design table. In this embodiment, the optimal solution obtained is a cross-sectional compression ratio A = 22.5%, a cross-sectional center radius B = 35.7 mm, an O-ring wire diameter of 6.2 mm, a volume fill rate of 93.2%, and a friction coefficient of 0.14.

[0045] In one embodiment, the present invention also provides a static sealing structure design system for low-temperature operating conditions, comprising: The type determination module is used to determine the optimal sealing ring type for low-pressure static seals through simulation calculations, based on equivalent stress, strain distribution, and contact stress as evaluation criteria; among them, the optimal sealing ring type is the O-ring. The simulation calculation module is used to determine the groove size corresponding to the O-ring during the simulation process. Taking the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, a simulation analysis model is established to determine the strain energy density function corresponding to the O-ring under the current low temperature conditions. The orthogonal experiment module is used to design orthogonal experiments under low-temperature conditions, with the cross-sectional compression ratio and volume fill ratio of the O-ring as the optimization objects. Based on the orthogonal experiment results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring is established. The regression model determination module is used to determine the fitted quadratic polynomial regression model of equivalent stress and maximum contact stress based on the comparison results of equivalent stress and maximum contact stress obtained from the strain energy density function and equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model. The parameter determination module is used to draw a 3D response surface plot of the interaction effect of each factor based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, and to determine the optimal size parameters of the static seal under the current low temperature condition based on the drawn 3D response surface plot of the interaction effect of each factor.

[0046] The low-temperature static sealing structure design method provided by this invention adopts a combination of finite element simulation, orthogonal experiment, and response surface optimization. Simulation data replaces empirical selection to determine the O-ring as the optimal cross-sectional structure type for GIS static sealing under low-temperature conditions. A validated "material-structure parameter" matching database of optimal cross-sectional compression ratio and volume fill rate for low-pressure static sealing components of GIS equipment under extreme outdoor low-temperature conditions of -40℃ is established, minimizing sealing failure caused by temperature changes. This method is applicable to low-pressure static sealing parts such as flanges, air chambers, and end caps of GIS equipment, achieving stable sealing with low leakage rate, low stress concentration, and long service life, meeting the airtightness requirements of GIS.

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for designing a static sealing structure under low-temperature operating conditions, characterized in that, include: S10 uses equivalent stress, strain distribution, and contact stress as evaluation criteria to determine the optimal sealing ring type for low-pressure static seals through simulation calculations; among them, the optimal sealing ring type is the O-ring. S20, determine the groove size corresponding to the O-ring during the simulation process, and use the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects to establish a simulation analysis model to determine the strain energy density function corresponding to the O-ring under the current low temperature conditions; S30, with the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, an orthogonal experimental design was carried out under low temperature conditions. Based on the orthogonal experimental results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring was established. S40, based on the comparison results of the equivalent stress and maximum contact stress obtained from the strain energy density function and the equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model, determine the fitted quadratic polynomial regression model of the equivalent stress and maximum contact stress. S50. Based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, a 3D response surface plot of the interaction effect of each factor is drawn, and the optimal size parameters of the static seal under the current low temperature condition are determined based on the 3D response surface plot of the interaction effect of each factor.

2. The method for designing a static sealing structure under low-temperature operating conditions according to claim 1, characterized in that, S10 includes: S101. Based on the preset cross-sectional compression ratio, volume filling ratio and contact surface roughness of each sealing ring type, the sealing ring type with the smallest maximum equivalent stress is determined by simulation. S102, extract the contact stress diagrams corresponding to each type of sealing ring to determine the type of sealing ring with uniform contact stress distribution during the simulation process; S103, the sealing ring with the smallest maximum equivalent stress, the most reasonable equivalent stress distribution, and the uniform contact stress distribution during the simulation process is determined to be the sealing ring type with the best performance corresponding to the low-pressure static sealing component structure.

3. The method for designing a static sealing structure under low-temperature operating conditions according to claim 2, characterized in that, When performing simulation analysis in S101, the preset cross-sectional compression rate for each type of sealing ring is 20%, the volume filling rate is 88.5%, and the surface roughness of the contact surface between the seal and the groove is 1.6μm.

4. The method for designing a static sealing structure under low-temperature operating conditions according to claim 2, characterized in that, The sealing material of the O-ring is low-temperature shrinkage TR. 10 Rubber materials with a temperature of ≤ -60℃.

5. The method for designing a static sealing structure under low-temperature operating conditions according to claim 4, characterized in that, S20 includes: S201, preset the cross-sectional compression ratio and cross-sectional center radius of different O-rings, and the groove size of the O-rings during the simulation process, and keep the preset groove size unchanged. Taking the cross-sectional compression ratio and cross-sectional center radius of the sealing ring as the optimization object, the compression stress simulation test of the sealing material of the O-ring under the current low temperature condition is carried out to obtain the corresponding stress-strain curve. S202, the stress-strain curve is fitted to the corresponding strain energy density function using a two-parameter MR constitutive model; wherein, the obtained strain energy density function is expressed as follows: Where W is the strain energy density function; I1 and I2 are the first and second Green's strain invariants, respectively; C 10 and C 01 These are material constants.

6. The method for designing a static sealing structure under low-temperature operating conditions according to claim 5, characterized in that, In S201, the preset cross-sectional compression rates of different O-rings during the simulation were 15%, 18.75%, and 22.5%, respectively, and the center radii of the O-ring cross-sections were 35.7 mm, 36.3 mm, and 37 mm. The preset groove dimensions corresponding to the O-rings were: the roughness of the groove contact surface was 1.6 μm, the roughness of the non-sealing surface was 3.2 μm, and the gap between the groove and the baffle was 0.1 mm.

7. The method for designing a static sealing structure under low-temperature operating conditions according to claim 5, characterized in that, S30 includes: S301, using the Box-Behnken response surface methodology, with cross-sectional compressibility, cross-sectional center radius and friction coefficient as factors, and maximum equivalent stress and maximum contact stress as response variables, an orthogonal experiment was conducted to obtain the orthogonal experimental results; S302. Based on the orthogonal experimental results, a quadratic polynomial regression analysis was performed using the response surface methodology to fit a quadratic polynomial regression model of the equivalent stress and the maximum contact stress.

8. The method for designing a static sealing structure under low-temperature operating conditions according to claim 7, characterized in that, In S302, the fitted equivalent stress and maximum contact stress quadratic polynomial regression model are expressed as follows: Where Y1 is the equivalent stress; Y2 is the maximum contact stress; A is the cross-sectional compressibility; B is the center radius of the cross-section; and C is the coefficient of friction.

9. A static sealing structure design system for low-temperature operating conditions, characterized in that, include: The type determination module is used to determine the optimal sealing ring type for low-pressure static seals through simulation calculations, based on equivalent stress, strain distribution, and contact stress as evaluation criteria; among them, the optimal sealing ring type is the O-ring. The simulation calculation module is used to determine the groove size corresponding to the O-ring during the simulation process. Taking the cross-sectional compression ratio and volume filling ratio of the O-ring as the optimization objects, a simulation analysis model is established to determine the strain energy density function corresponding to the O-ring under the current low temperature conditions. The orthogonal experiment module is used to design orthogonal experiments under low-temperature conditions, with the cross-sectional compression ratio and volume fill ratio of the O-ring as the optimization objects. Based on the orthogonal experiment results, a quadratic polynomial regression model of the equivalent stress and maximum contact stress of the O-ring is established. The regression model determination module is used to determine the fitted quadratic polynomial regression model of equivalent stress and maximum contact stress based on the comparison results of equivalent stress and maximum contact stress obtained from the strain energy density function and equivalent stress and maximum contact stress calculated from the quadratic polynomial regression model. The parameter determination module is used to draw a 3D response surface plot of the interaction effect of each factor based on the determined quadratic polynomial regression model of equivalent stress and maximum contact stress, and to determine the optimal size parameters of the static seal under the current low temperature condition based on the drawn 3D response surface plot of the interaction effect of each factor.

10. A static sealing structure obtained based on the design method according to any one of claims 1-8, characterized in that, The static sealing structure includes an O-ring and a groove that matches the O-ring. The O-ring has a cross-sectional compression rate of 22.5%, a cross-sectional center radius of 35.7 mm, a wire diameter of 6.2 mm, and a friction coefficient of 0.

14. The groove has a volume filling rate of 93.2%, a contact surface roughness of 1.6 μm, a non-sealing surface roughness of 3.2 μm, a depth of 4.7 mm, a width of 6.8 mm, and a groove inlet chamfer of 0.5.

Images