A composite corrugated cylinder pressure hull

Abstract

The present invention relates to a composite corrugated cylinder-section pressure hull having a cylindrical structure, a smooth outer surface without corrugations, and an inner surface provided with composite corrugations formed by interlacing circumferential corrugations and longitudinal corrugations. The present invention combines the buckling characteristics of circumferential corrugations and longitudinal corrugations, and can withstand relatively high uniformly distributed external pressure loads. Its characteristics are that, compared with a single circumferential corrugation, the thickness of the composite corrugated pressure hull undergoes periodic variations in both the circumferential and longitudinal directions. In addition, the composite corrugated pressure hull has a significant improvement in withstanding uniformly distributed pressure and axial pressure, and has a wider range of applications, and is particularly suitable for large-diameter thin-shell structures.

Description

Technical Field

[0001] The present invention relates to the technical field of cylindrical pressure hulls, in particular to a composite corrugated cylinder-segment pressure hull. Background Art

[0002] In recent years, corrugated reinforced cylindrical pressure hulls have become widely popular, with circumferential corrugations and longitudinal corrugations appearing. The advantage of circumferential corrugations and longitudinal corrugations is that they can cope with uniformly distributed external pressure loads, but they do not achieve the expected bearing capacity for more complex load forms. For example, the circumferential corrugated pressure hull under axial pressure has poor buckling performance. When the closed large-diameter cylinder section pressure hull is subjected to hydrostatic pressure, the pressure at both ends of the cylinder section cannot be ignored.

[0003] Considering the wide range of application backgrounds, the pressure hull will face more complex working loads, including not only uniformly distributed external pressure, but also axial pressure and various local stress states. Therefore, it is urgent to develop a composite corrugated cylinder pressure hull to better adapt to complex load forms. Summary of the Invention

[0004] In response to the above problems, the purpose of the present invention is to provide a composite corrugated cylinder-segment pressure hull, aiming to improve the ultimate bearing capacity of the cylindrical thin-walled pressure hull, form a more systematic design concept of the composite corrugated cylinder-segment pressure hull, and verify the buckling critical values ​​of different corrugated structures under various load conditions through finite element simulation.

[0005] The technical solution adopted in the present invention is as follows:

[0006] The composite corrugated cylinder-segment pressure hull proposed in the present invention has a cylindrical structure, a smooth outer surface without corrugations, and an inner surface provided with composite corrugations formed by interlacing circumferential corrugations and longitudinal corrugations.

[0007] Furthermore, the circumferential corrugation morphology conforms to the cosine function:

[0008]

[0009] Where: a is the amplitude of the cosine function; T is the period of the cosine function; b is the displacement of the cosine function on the x-axis.

[0010] Furthermore, the contour of the longitudinal corrugation is connected by several smooth curves into a closed loop, and the corrugation morphology is determined by the function Determine and correspond to the Fourier series in polar coordinates:

[0011]

[0012] Where:

[0013]

[0014] N is the number of segments of the ripple curve in the interval [0, 2π], which is usually an odd number;

[0015] The longitudinal corrugation profile curve is symmetrical about the center of the circle, and the Fourier series The expansion contains only cosine terms and converges to [-π, π]. In polar coordinates, the arc differential of the curve is:

[0016]

[0017] in The radius of curvature of any point on the curve is R1, then the curvature of the point is:

[0018]

[0019] Furthermore, the circumferential corrugation profile curve is used as the profile, the longitudinal corrugation profile curve is used as the path, and the profile is scanned along the path to form the geometric inner surface of the composite corrugated cylinder segment pressure hull. The composite corrugated pressure hull has periodic thickness changes in both the circumferential and longitudinal directions.

[0020] Furthermore, the thickness of any point of the composite corrugated shell pressure hull structure can be expressed as:

[0021]

[0022] R1 is the radius of curvature of any point on the longitudinal corrugation profile curve; when R1 is minimum, R1 = r2; when R1 is maximum, R1 = r1; the thickness of the composite corrugated shell at the peak is t max =r0-r2+2a, the thickness of the corrugation intersection is t min = r0-r1;

[0023] Where: r0 is the outer diameter of the composite corrugated shell; r1 is the base circle radius of the trough of the longitudinal corrugation profile curve; r2 is the base circle radius of the peak of the longitudinal corrugation profile curve.

[0024] Furthermore, the circumferential corrugations and the longitudinal corrugations are interlaced with each other and the corrugations are equidistantly distributed.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. It has better buckling performance under uniformly distributed external pressure. The composite corrugated pressure hull has the characteristic of equalizing pressure, which can evenly distribute the external load at the trough position, which is conducive to bearing higher loads.

[0027] 2. Compared with ordinary cylindrical shells and circumferential corrugated pressure shells, the post-buckling of composite corrugated pressure shells only causes one depression and has little impact on other intact parts, and is less sensitive to initial defects.

[0028] 3. In addition to uniformly distributed external pressure, the buckling performance of the composite corrugated pressure hull under axial pressure is also outstanding. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the three-dimensional structure of the composite corrugated cylinder segment pressure hull of the present invention;

[0030] Figure 2 This is a top view of the composite corrugated forming of the present invention;

[0031] Figure 3 This is a front view of the composite corrugated forming of the present invention;

[0032] Figure 4 It is the “displacement-load” line graph under uniform external pressure load;

[0033] Figure 5 It is the “displacement-load” line graph under axial pressure load;

[0034] Figure 6 The critical and post-buckling displacement cloud diagrams of composite corrugated cylindrical shells;

[0035] Figure 7 Post-buckling stress cloud diagram of composite corrugated cylindrical shell and circumferential corrugated cylindrical shell. DETAILED DESCRIPTION

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] It should be noted that in the description of the present invention, it should be noted that the terms "up", "down", "top", "bottom", "one side", "the other side", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0038] The present invention proposes a composite corrugated shell, such as Figure 1As shown, the overall structure is cylindrical. The outer surface of the cylindrical shell is smooth and has no corrugations. The inner surface of the cylindrical shell is provided with both circumferential corrugations and longitudinal corrugations. The circumferential corrugations and longitudinal corrugations are interlaced to form composite corrugations, and the corrugations are equidistantly distributed. The circumferential corrugation profile curve is used as the outline, and the longitudinal corrugation profile curve is used as the path. The outline is scanned along the path to form the geometric inner surface of the composite corrugated cylinder segment pressure hull. The top view and front view of the composite corrugation forming are shown in the figure. Figure 2 and Figure 3 shown.

[0039] Among them, the circumferential corrugation morphology conforms to the cosine function:

[0040]

[0041] Where: a represents the amplitude of the cosine function (the amplitude of the circumferential ripple is twice the amplitude of the cosine function, that is, 2a), T represents the period of the cosine function, and b represents the displacement of the cosine function on the x-axis.

[0042] The longitudinal corrugation morphology can be expressed by the function Determine and correspond to the Fourier series in polar coordinates:

[0043]

[0044] Where: N represents the number of segments of the ripple curve in the interval [0, 2π], which is generally an odd number.

[0045] The longitudinal corrugation profile curve is symmetrical about the center of the circle, and the Fourier series The expansion contains only cosine terms and converges to [-π, π]. In polar coordinates, the arc differential of the curve is:

[0046]

[0047] in The radius of curvature of any point on the curve is R1, then the curvature of the point is:

[0048]

[0049] like Figure 2 As shown in the figure, r0 represents the outer diameter of the composite corrugated shell, r1 and r2 are the radii of the base circle of the trough and peak of the longitudinal corrugation profile, S represents the corrugation width (N·S=2πr2), and R1 represents the radius of curvature of any point on the longitudinal corrugation profile curve. The composite corrugated shell has periodic thickness variations in both the circumferential and longitudinal directions. The thickness at any point can be expressed as:

[0050]

[0051] When R1 is the smallest, R1 = r2; when R1 is the largest, R1 = r1, the thickness of the composite corrugated shell at the crest is t max =r0-r2+2a, the thickness of the corrugation intersection is t min =r0-r1.

[0052] The effects of the present invention are further described below by means of specific examples and comparative examples:

[0053] Example 1

[0054] Example 1 is a composite corrugated shell section pressure hull proposed by the present invention, and the composite corrugated morphology and structural parameters are:

[0055] r0=100mm, r1=99mm, r2=97mm, V=596cm 3 , L = 240 mm, N = 23;

[0056]

[0057] First, a model was built using 3D modeling software, and then imported into finite element analysis software for calculation, and simulation was performed under the action of two loads: uniform external pressure and axial pressure. The material used was TC4 titanium alloy, with elastic modulus E = 108Gpa, Poisson's ratio μ = 0.3, and yield strength σ s =830Mpa, density ρ = 4.43g / cm 3 .

[0058] When analyzing uniform external pressure, the shell is supported at three points, and six displacement components are constrained. The boundary conditions are set symmetrically, that is, two nodes are taken at the centers of the two ends of the cylinder, denoted as node 1 and node 2, and their U x =U y =0; take the midpoint of the busbar outside the shell as node 3, its U x =U z = 0. In axial pressure analysis, the lower end node of the cylinder section is completely fixed, and the upper end node of the cylinder section constrains the freedom of movement in the x and y directions.

[0059] Comparative Example 1

[0060] Comparative Example 1 is a common cylindrical shell, which is compared with the composite corrugated pressure shell of Example 1 for buckling value under uniform external pressure load. The structural parameters of the common cylindrical shell are: r0 = 100 mm, r1 = 96 mm, L = 240 mm, V = 591 cm 3 The material selection, boundary conditions and constraints are exactly the same as those in Example 1. The comparison of finite element calculation results is shown in Table 1. The nonlinear buckling "displacement-load" is shown in Figure 4 shown.

[0061] Table 1 Finite element calculation of composite corrugated pressure hull and ordinary cylindrical shell (uniformly distributed external pressure, unit MPa)

[0062]

[0063] After applying a uniformly distributed external pressure load, the composite corrugated pressure hull exhibited a higher ultimate bearing capacity, approximately 16% higher than that of a conventional cylindrical shell, and exhibited slightly smaller displacements at the critical load. Buckling in a conventional cylindrical shell occurs primarily in the center, with the stress concentration area concave inward, resulting in four circumferential instability waves. The maximum displacement at the concave area is 3.82 mm at critical buckling and 12.42 mm at postbuckling.

[0064] The stress of the composite corrugated cylinder pressure hull is evenly distributed on the longitudinal trough of the inner surface of the shell and the entire outer surface. There are four circumferential instability waves at the critical point. The final post-buckling depression is concentrated in one place, and other parts are less affected. The critical and post-buckling displacement cloud diagrams of the composite corrugated cylinder pressure hull are shown in Figure 2. Figure 6 As shown in Figure 2, the maximum displacement of the concave area is 1.8 mm when critical buckling is reached, and 6.96 mm when postbuckling is reached. Based on the buckling modal analysis of the two structures, the composite corrugation is more suitable for withstanding hydrostatic pressure.

[0065] Comparative Example 2

[0066] Comparative Example 2 is a circumferential corrugated cylindrical shell, which is compared with the composite corrugated cylinder pressure shell of Example 1 in terms of buckling value under axial pressure load. The structural parameters of the circumferential corrugated cylindrical shell are: r0 = 100mm, r1 = 98mm, r2 = 94mm, L = 240mm, V = 590cm 3 The material selection, boundary conditions and constraints are exactly the same as those in Example 1. The comparison of finite element calculation results is shown in Table 2. The nonlinear buckling "displacement-load" is shown in Figure 5 shown.

[0067] Table 2 Finite element calculation of composite corrugated pressure hull and circumferential corrugated cylindrical shell (axial pressure, unit: KN)

[0068]

[0069] When axial pressure is applied, the composite corrugated cylindrical pressure hull exhibits a greater ultimate load-bearing capacity, demonstrating a strengthening effect. Comparing the two loads, the composite corrugations significantly increase the local radius of curvature of the cylindrical pressure hull, resulting in a higher local curvature than that of an ordinary cylindrical shell. From flat to curved surfaces, the higher the curvature of the shell, the higher the load-bearing capacity.

[0070] The circumferential corrugated cylindrical shell reaches the post-buckling state, and 4 slight depressions are generated near the fixed end. The stress is mainly concentrated at the fixed end and the circumferential trough. The composite corrugated shell reaches the post-buckling state. The stress distribution of the inner and outer layers of the shell is different. The outer layer is mainly concentrated in the middle and around the circumference, and is symmetrically distributed from the middle to the two ends; the inner layer is mainly concentrated in the circumferential corrugation trough. The post-buckling stress distribution of the two corrugated cylindrical shells is as follows Figure 7 If the corrugation amplitude is further reduced and the thickness is reduced, the compressive strength of the composite corrugated shell will be more obvious.

[0071] Matters not described in detail in this invention are all known technologies.

[0072] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A composite corrugated shell, characterized by: The cylinder section pressure hull is cylindrical in structure, and the outer surface is smooth and without corrugation, while the inner surface is provided with composite corrugations formed by interlacing circumferential corrugations and longitudinal corrugations; The morphology of the circumferential corrugation conforms to the cosine function: Where: a is the amplitude of the cosine function; T is the period of the cosine function; b is the displacement of the cosine function on the x-axis; The contour of the longitudinal corrugation is connected by several smooth curves into a closed loop, and the corrugation morphology is determined by the function Determine and correspond to the Fourier series in polar coordinates: Where: ; ； N is The number of segments of the ripple curve within the interval; The contour curve of the longitudinal corrugation is symmetrical about the center of the circle, and the Fourier series The expansion contains only cosine terms and converges to ; In polar coordinates, the arc differential of the curve is: in , the radius of curvature of any point on the curve is R1, then the curvature of the point is: ； The thickness of any point of the shell structure of the composite corrugated shell can be expressed as: R1 is the radius of curvature of any point on the longitudinal corrugation profile curve; when R1 is minimum, R1=r2; when R1 is maximum, R1=r1; the thickness of the composite corrugated shell at the peak is The thickness of the corrugation intersection is ; Where: r0 is the outer diameter of the composite corrugated shell; r1 is the base circle radius of the trough of the longitudinal corrugation profile curve; r2 is the base circle radius of the peak of the longitudinal corrugation profile curve.

2. The composite corrugated shell pressure hull according to claim 1, characterized in that: The circumferential corrugation profile curve is used as the profile, the longitudinal corrugation profile curve is used as the path, and the profile is scanned along the path to form the geometric inner surface of the composite corrugated cylinder pressure hull. The composite corrugated pressure hull has periodic thickness changes in both the circumferential and longitudinal directions.

3. The composite corrugated shell pressure hull according to claim 1, characterized in that: The circumferential corrugations and the longitudinal corrugations are staggered with each other and the corrugations are distributed at equal intervals.

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