A method for fabricating a non-magnetic space grid shell structure composed of carbon fiber sheets

Abstract

This invention discloses a method for fabricating a non-magnetic spatial reticulated shell structure composed of carbon fiber sheets. The load-bearing components of this reticulated shell structure are made of non-magnetic carbon fiber, while the connecting nodes are made of non-magnetic titanium alloy. A magnetic shielding layer is arranged in the roof system above the structural layer, creating a non-magnetic space with a magnetic field strength below 1 nT inside the reticulated shell. Specifically, the load-bearing components are made of carbon fiber sheets, fixed by two carbon fiber limb plates in an interlimb connection to form a hollow rectangular composite section. The connecting nodes consist of titanium alloy node plates, titanium alloy bolt groups, and carbon fiber limb plates. The magnetic shielding layer of the roof system consists of a shielding layer pad, a shielding layer, a shielding layer pressure plate, a buffer layer, a permalloy plate, and pressure strips. This invention features lightweight, high strength, and non-magnetic properties, creating a near-zero residual magnetism space through the roof magnetic shielding layer. It can be applied to various functional buildings with high magnetic field shielding requirements, as well as to general construction engineering.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spatial structure, and particularly relates to a method for manufacturing a non-magnetic spatial reticulated shell structure composed of carbon fiber sheets. BACKGROUND

[0002] In a special type of building structure, for example, an experimental center that needs to create a non-magnetic field environment, not only a large space inside is needed, but also the magnetic field strength in the space needs to be almost zero. The existence of the geomagnetic field leads to the existence of a certain strength of the magnetic field in most natural or artificial places on earth, which cannot guarantee the smooth progress of the non-magnetic experiment. Covering the building skin with magnetic shielding materials can weaken the magnetic field strength in the internal space to a certain extent, but the metal materials (such as steel, reinforced concrete) used in the traditional structure system have certain magnetism, and thus are not suitable for being used as the main material of the structure in the non-magnetic field environment. Although bamboo and wood are non-magnetic materials, they are not suitable for being widely used in important building structures due to their poor fire resistance and corrosion resistance.

[0003] Carbon fiber material has the characteristics of light weight, high strength, corrosion resistance and non-magnetic, and is particularly suitable for the functional requirements of the above building structure. The traditional reticulated shell structure generally adopts round, square or I-shaped section profiles, but the processing technology of carbon fiber material makes it difficult to process profiled members with the above-mentioned cross sections, and more carbon fiber plates are used. At present, there is an invention practice of using metal sheets as the main force members of the free-form reticulated shell structure, which has the following advantages: 1) the sheet material can be processed into any curved profile through laser cutting technology, and the processing efficiency and precision are high, which is suitable for factory prefabrication; 2) the sheet members can be efficiently stacked, saving a lot of space in storage and transportation; 3) the cross section of the sheet member is a regular rectangle, and the node structure is simple, which is suitable for prefabricated structures. Therefore, using carbon fiber plates as the main members of the reticulated shell structure also has certain application prospects, and under the premise of considering reasonable economic cost, a reticulated shell structure with a span of more than 30m can be built.

[0004] According to the superior light weight, high strength and non-magnetic properties of the new building material carbon fiber plate, combined with the application practice of sheet members in building structures, the present application provides a method for manufacturing a non-magnetic spatial reticulated shell structure composed of carbon fiber sheets, which can effectively solve the building problem of creating a non-magnetic field environment and provide a new form of spatial structure. SUMMARY

[0005] The present application aims at the deficiencies of the prior art, and provides a method for manufacturing a non-magnetic spatial reticulated shell structure composed of carbon fiber sheets,

[0006] The objective of this invention is achieved through the following technical solution: a method for manufacturing a non-magnetic space shell structure composed of carbon fiber sheets, wherein the load-bearing components of the shell structure are made of non-magnetic carbon fiber material, the connecting nodes are made of non-magnetic titanium alloy material, a magnetic shielding layer is arranged on the roof system above the structural layer, and a non-magnetic space with a magnetic field strength of less than 1nT is formed inside the shell.

[0007] Furthermore, the space reticulated shell structure uses carbon fiber double-limb plate members as the main load-bearing components, which are fabricated as follows: two carbon fiber limb plates with length l, thickness t, and width b are placed parallel to each other at a distance h, and the carbon fiber limb plates are fixed by interlimb connections at intervals of distance d, thereby forming a hollow rectangular section composite member. The equivalent slenderness ratio formula used for its internal force verification is as follows:

[0008] Slenderness ratio of weak axis:

[0009] Strong axis slenderness ratio:

[0010] Where, α g The reduction factor related to the geometry of the carbon fiber split plate needs to be determined based on the axial compression test of the double-limb spliced ​​carbon fiber plate; α t The reduction factor related to the interlaminar shear strength of carbon fiber split plates needs to be determined based on the axial compression test of double-limb spliced ​​carbon fiber plates.

[0011] Furthermore, the connection node consists of a cross-shaped titanium alloy plate, a group of titanium alloy bolts, and a carbon fiber branch plate. It is fabricated as follows: the carbon fiber branch plate is fixed to the cross-shaped titanium alloy node plate using a friction-type connection with the group of titanium alloy bolts to form the titanium alloy node. The failure process of the titanium alloy node under bending moment load exhibits four stages: bond-slip-strengthening-failure. The node rotational stiffness is relatively weak in the slip and failure stages. The design calculation formulas for the node rotational stiffness K1 in the bond stage and K3 in the strengthening stage are as follows:

[0012]

[0013]

[0014]

[0015]

[0016] Where E is the elastic modulus of the titanium alloy; t j b is the thickness of the gusset plate; j The width of the node plate; l j d is the effective length of the gusset plate. bt is the diameter of the titanium alloy bolt; t is the thickness of the carbon fiber split plate; t m I represents the thickness of the carbon fiber segmented plate. b GA represents the moment of inertia of the bolt. b The cross-sectional shear stiffness of the titanium alloy bolt; E is the sum of the squares of the distances from each bolt in the bolt group to its center; c β is the elastic modulus of carbon fiber; b and β t f is a coefficient value related to the bolt hole. u e represents the ultimate tensile strength of the titanium alloy plate. b p is the minimum distance from the center of the bolt hole to the edge of the node plate. b This refers to the bolt hole spacing.

[0017] Furthermore, the magnetic shielding layer of the roofing system is made of permalloy and is manufactured by sequentially installing a shielding pad, a shielding layer, a shielding pressure plate, a buffer layer, a permalloy plate, and a pressure strip on the carbon fiber double-limb plate component, and fixing them with titanium alloy bolts or screws.

[0018] Furthermore, the economically reasonable span of the space grid shell structure reaches over 30m.

[0019] Furthermore, the contact surfaces of the cross-shaped titanium alloy node plate and the carbon fiber branch plate are both sandblasted to improve the friction between the carbon fiber branch plate and the cross-shaped titanium alloy node plate.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention innovatively uses a combined double-limb carbon fiber plate component as the main component of a space grid shell structure, giving full play to the advantages of carbon fiber plates being lightweight, high-strength, and non-magnetic.

[0022] 2. The carbon fiber sheet components of the present invention can be prefabricated in a factory with small manufacturing errors; they are easy to store and transport; the joint structure is simple, construction is convenient, and installation errors are small.

[0023] 3. The titanium alloy node and bolt connection structure of the present invention has the characteristics of low magnetism and high strength, and it fits well with carbon fiber plate components, resulting in a reasonable stress distribution structure.

[0024] 4. The permalloy plate magnetic shielding roof structure of the present invention has the characteristics of simple structure, simple installation and reliable strength.

[0025] 5. The non-magnetic mesh shell structure of the present invention can be applied to various functional buildings with high requirements for magnetic field shielding, as well as to ordinary building engineering fields, as a new type of spatial structure. Attached Figure Description

[0026] To more 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 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.

[0027] Figure 1 This is a schematic diagram of the space reticulated shell structure used in the present invention for a ribbed annular mesh spherical reticulated shell.

[0028] Figure 2 This is a diagram showing the structure and geometric dimensions of a carbon fiber sheet component.

[0029] Figure 3 This is a schematic diagram of the load-displacement curves of the connecting nodes.

[0030] Figure 4 This is a schematic diagram of the construction of the connecting nodes.

[0031] Figure 5 This is a schematic diagram of the construction of the magnetic shielding layer of the roof system.

[0032] Figure 6 This is a schematic diagram of the overall reticulated shell structure and its basic components. Detailed Implementation

[0033] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention. The specific implementation process for fabricating the non-magnetic space grid shell structure is as follows:

[0034] (1) Design the structural geometry according to the requirements of the actual building. This implementation process takes a spherical reticulated shell structure as an example, and divides the ribbed ring grid (e.g. Figure 1 (As shown). The reticulated shell structure uses two parallel carbon fiber limb plates connected by interlimb joints to form a carbon fiber double-limb plate component as the load-bearing member. The interlimb joint is formed by fixing the two parallel carbon fiber limb plates together with several equally spaced fixed limb plates, and then connecting them with titanium alloy nodes and titanium alloy bolts. The titanium alloy node consists of a cross-shaped titanium alloy node plate, a group of titanium alloy bolts, and a carbon fiber limb plate. The carbon fiber limb plate and the cross-shaped titanium alloy node plate are fixed by the group of titanium alloy bolts using a friction-type connection. The contact surfaces of the cross-shaped titanium alloy node plate and the carbon fiber limb plate are all sandblasted to increase the friction between the carbon fiber limb plate and the cross-shaped titanium alloy node plate.

[0035] (2) Establish a numerical model based on the mesh structure, and set the initial cross-sectional dimensions of the carbon fiber double-limb plate component and the initial dimensions of the double-limb connection structure (e.g., Figure 2As shown), set the relevant component and node material properties, and preliminarily set the moment-rotation curve of the node rotational stiffness according to engineering requirements (e.g., Figure 3 (As shown).

[0036] (3) Perform static linear elastic calculations on the structure based on the known load conditions and support conditions to obtain the deflection and displacement of the structure. Compare the building requirements and relevant design codes to check whether they meet the requirements. If they do not meet the requirements, reset the component size or node rotation stiffness in step (2) and repeat the above steps.

[0037] (4) Based on the known load conditions and support conditions, perform double nonlinear elastoplastic static calculations on the structure to obtain the ultimate bearing capacity of the structure. Compare the building requirements and relevant design codes to check whether they meet the requirements. If they do not meet the requirements, reset the component size or node rotation stiffness in step (2) and repeat the above steps.

[0038] (5) Extract the end load information of the component from the static calculation results, and verify the strength and stability according to the equivalent slenderness ratio formula of the component as follows. Compare the building requirements and relevant design specifications to check whether they meet the requirements. If they do not meet the requirements, reset the component size in step (2) and repeat the above steps.

[0039] Slenderness ratio of weak axis:

[0040] Strong axis slenderness ratio: Where l is the length of the carbon fiber segmented plate, t is the thickness of the carbon fiber segmented plate, b is the width of the carbon fiber segmented plate, h is the distance between two parallel carbon fiber segmented plates, d is the fixed distance between the segmented plates, and α g The reduction factor related to the geometry of the carbon fiber split plate needs to be determined based on the axial compression test of the two-limb spliced ​​carbon fiber plate. α t The reduction factor related to the interlaminar shear strength of carbon fiber split plates needs to be determined based on the axial compression test of double-limb spliced ​​carbon fiber plates.

[0041] (6) Based on the moment-rotation curve of the node rotation stiffness in step (2), the node dimensions and bolt arrangement are calculated using the following formula (e.g., Figure 4 As shown), the failure process of titanium alloy nodes under bending moment load presents four stages: bonding, slippage, strengthening, and failure. Among them, the node rotation stiffness is relatively weak in the slippage and failure stages. According to the actual node construction situation and the construction requirements of relevant specifications, check whether the node is feasible. If it does not meet the requirements, reset the bending moment-rotation curve of the node stiffness in step (2) and repeat the above steps.

[0042]

[0043]

[0044]

[0045]

[0046] Where E is the elastic modulus of the titanium alloy; t j b is the thickness of the gusset plate; j The width of the node plate; l j d is the effective length of the gusset plate. b t is the diameter of the titanium alloy bolt; t is the thickness of the carbon fiber split plate; t m I represents the thickness of the carbon fiber segmented plate. b GA represents the moment of inertia of the bolt. b The cross-sectional shear stiffness of the titanium alloy bolt; E is the sum of the squares of the distances from each bolt in the bolt group to its center; c β is the elastic modulus of carbon fiber; b and β t f is a coefficient value related to the bolt hole. u e represents the ultimate tensile strength of the titanium alloy plate. b p is the minimum distance from the center of the bolt hole to the edge of the node plate. b This refers to the bolt hole spacing.

[0047] (7) Based on the above design parameters, arrange the magnetically shielded roof system. Install the shielding layer pad, shielding layer, shielding layer pressure plate, buffer layer, permalloy plate, and pressure strip sequentially on the carbon fiber sheet components to form the roof system (e.g., ...). Figure 5 (As shown). The roof system above the structural layer is densely covered with permalloy plates with magnetic shielding properties, forming a space with a magnetic field strength of less than 1 nT inside the mesh shell, and the space inside the mesh shell has the characteristic of near-zero remanence.

[0048] (8) A specific embodiment of the method for fabricating a non-magnetic space grid shell structure is finally obtained (e.g.) Figure 6 (As shown).

[0049] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a non-magnetic space lattice shell structure composed of carbon fiber sheets, characterized by, The stressed member of the net shell structure adopts non-magnetic carbon fiber material, the connecting node adopts non-magnetic titanium alloy material, a magnetic shielding layer is arranged on the roof system above the structural layer, and a non-magnetic space with a magnetic field strength lower than 1 nT is formed inside the net shell. The spatial net shell structure adopts carbon fiber double-limb plate members as the main stressed members, and is manufactured by the following manner: two carbon fiber double-limb plates with a length of l, a thickness of t and a width of b are placed in parallel at a distance of h, the carbon fiber double-limb plates are fixed in a form that the inter-limb connections are arranged at a distance of d, so as to form a hollow rectangular cross-section combined member, and an equivalent slenderness ratio formula used for internal force checking is as follows: wherein, is the reduction factor related to the geometric size of the carbon fiber split plate, which needs to be determined according to the axial compression test of the double-limb split carbon fiber plate; is the reduction factor related to the interlaminar shear strength of the carbon fiber split plate, which needs to be determined according to the axial compression test of the double-limb split carbon fiber plate.

2. The method of claim 1, wherein the method further comprises: The connecting node is composed of a cross-shaped titanium alloy plate, a titanium alloy bolt group and a carbon fiber sub-limb plate, and is made by fixing the carbon fiber sub-limb plate and the cross-shaped titanium alloy node plate in a friction type connecting mode by the titanium alloy bolt group to form a titanium alloy node, and the failure process of the titanium alloy node when bearing a bending moment load presents four stages of bonding-slippage-strengthening-failure, wherein the node rotation stiffness in the slippage and failure stages is relatively weak, the node rotation stiffness in the bonding stage and the node rotation stiffness in the strengthening stage The design calculation formulas are as follows respectively. ​ wherein, E is the modulus of elasticity for the titanium alloy; t is the thickness of the gusset plate; b is the width of the gusset plate; L is the effective length of the gusset plate; d is the diameter of the titanium alloy bolt; t is the thickness of the carbon fiber sub-panel; t is the thickness of the carbon fiber sub-panel; I is the moment of inertia of the bolt; G is the shear stiffness of the titanium alloy bolt cross-section; S is the sum of the square of the distance from each bolt to the center of the bolt group; E is the modulus of elasticity for the carbon fiber; and C is a coefficient value associated with the bolt hole; σ is the ultimate tensile strength of the titanium alloy plate; D is the minimum distance from the center of the bolt hole to the edge of the gusset plate; P is the bolt hole spacing.

3. The method of claim 1, wherein the method further comprises: The magnetic shielding layer of the roof system adopts permalloy, and the magnetic shielding layer is manufactured by the following manner: a shielding layer pad, a shielding layer, a shielding layer pressing plate, a buffer layer, a permalloy plate and a pressing strip are sequentially installed on the carbon fiber double-limb plate member, and are fixed by titanium alloy bolts or screws. ​ 4. The method of claim 1, wherein the method further comprises: The economic and reasonable span of the spatial net shell structure reaches more than 30 m. ​ 5. The method of claim 2, wherein the method further comprises: The contact surfaces of the cross-shaped titanium alloy node plate and the carbon fiber double-limb plate are all subjected to sand blasting treatment, so as to improve the friction between the carbon fiber double-limb plate and the cross-shaped titanium alloy node plate. ​

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