Slotted bolt box with low bolt leverage effect

Abstract

The invention discloses a slotted bolt box with a low bolt leverage effect. The slotted bolt box comprises a left wall plate, a right wall plate, a rear wall plate, a bottom plate and a top plate, wherein the left wall plate, the right wall plate, the rear wall plate, the bottom plate and the top plate enclose a box body with an opening; a bolt mounting hole is formed in the center of the bottom plate; the root of the box body is provided with a gap to reduce the lever effect of the bolt. According to the slotted bolt box, the lever effect can be greatly reduced, the bolt force is reduced by 18%, the local tensile strength of the end frames of the two parties is effectively improved, and the slotted bolt box can be applied to connection of transverse butt joint face bolts in point type connection in a rocket body structure.

Description

Technical Field

[0001] This invention belongs to the field of bolt box design technology, and particularly relates to a slotted bolt box with low bolt leverage effect. Background Technology

[0002] In rocket body structures, transverse docking frames requiring separation are typically connected using a small number (e.g., 8, 12, etc.) of low-impact separation bolts. Figure 1 As shown, this connection method is called a point connection. Point connections often suffer from uneven bolt stress, and excessive stress on individual bolts may lead to strength failure. Increasing the number of low-impact bolts can reduce the bolt load, but it also introduces new problems, such as significantly increasing structural weight and reducing separation reliability. Therefore, bolt load reduction is usually achieved by performing stress analysis on the bolts and optimizing the local bolt box structure.

[0003] Ideally, the force on a single bolt is the cross-sectional tensile load divided by the number of bolts. However, the actual bolt force is usually 2 to 3 times the ideal value. This load amplification is due to the lever effect generated during the deformation of the bolt box structure, which increases the bolt force. The mechanism of the lever effect in traditional bolt boxes is as follows: Figure 2 As shown, the bolt box bears a tensile load F. 拉力 During operation, the root of the bolt box is pulled open, and the front end of the upper bolt box presses against the lower bolt box. The force exerted by the pressing point on the upper bolt box is F. 杠杆 Force analysis of the upper bolt box shows that F 拉力 +F 杠杆 -F 螺栓 =0, that is, F 螺栓 =F 拉力 +F 杠杆 Therefore, in F 拉力 If the external load cannot be reduced, the bolt force F should be reduced. 螺栓 The only way is to reduce F as much as possible. 杠杆 accomplish.

[0004] The following are some commonly used traditional bolt box designs:

[0005] 1) Patent application number CN201610529056.5 discloses a novel high-efficiency lightweight aerospace explosive bolt box, which improves the stress situation of the bolt box and the back plate connector by optimizing the force transmission path and reduces the weight of the bolt box. Its main problem is that it does not improve the stress situation of the point connection bolts.

[0006] 2) Patent application CN202311636784.2 discloses a solid-propellant fairing resistant to pulsating pressure at large cone angles. It addresses the load reduction technology of a combination of a separation bolt box and a docking frame under pulsating pressure at large cone angles. Through a combined design, it changes the pitch circle of the separation surface, reducing the lever effect of the separation surface and thus improving load-bearing capacity. Its main problem is that implementing this solution requires changing the pitch circle of the docking bolt position and cannot guarantee the integrity of the bolt box mounting shell end frame. Summary of the Invention

[0007] The technical problem solved by the present invention is to overcome the shortcomings of the prior art and provide a slotted bolt box with low bolt leverage effect, which can greatly reduce the leverage effect, reduce the bolt force by 18%, effectively improve the local tensile strength of both end frames, and can be applied to the connection of transverse butt bolts in the midpoint connection of the arrow body structure.

[0008] To address the aforementioned technical problems, this invention discloses a slotted bolt box with low bolt leverage effect, comprising: a left wall panel, a right wall panel, a rear wall panel, a bottom plate, and a top plate; wherein, the left wall panel, right wall panel, rear wall panel, bottom plate, and top plate form an open box; a bolt mounting hole is provided in the center of the bottom plate; and a slot is provided at the base of the box to reduce the bolt leverage effect.

[0009] In the aforementioned slotted bolt box with low bolt leverage effect, the slot is opened on the rear wall panel, on the side near the bottom plate.

[0010] In the aforementioned slotted bolt box with low bolt leverage effect, the length of the slot is equal to the vertical distance between the left and right wall panels, ensuring that the rear wall panel does not participate in the load-bearing under bolt tension.

[0011] In the aforementioned slotted bolt box with low bolt leverage effect, the slot is opened on the bottom plate, near the rear wall plate.

[0012] In the aforementioned slotted bolt box with low bolt leverage effect, the length of the slot is equal to the vertical distance between the left and right wall panels, ensuring that the base plate does not participate in the load-bearing under bolt tension.

[0013] In the aforementioned slotted bolt box with low bolt leverage effect, the slot width W satisfies: 0 < W ≤ W max Among them, W max This indicates the maximum width without affecting the structural strength and stiffness of the bolt box.

[0014] In the aforementioned slotted bolt box with low bolt leverage effect, the width W of the slot is 5–20 mm.

[0015] In the aforementioned slotted bolt box with low bolt leverage effect, the edges of the slot are chamfered to avoid stress concentration caused by the slot affecting the load-bearing capacity.

[0016] In the aforementioned slotted bolt box with low bolt leverage effect, several slotted bolt boxes are arranged in pairs and in an up-down layout on the transverse docking frame of the rocket body structure where separation is required.

[0017] In the aforementioned slotted bolt box with low bolt leverage effect, the left and right wall panels of the slotted bolt box are integrally formed with the transverse docking frame; at the same time, the skin on the outside of the transverse docking frame is set according to the spatial position of the docking holes of the upper and lower slotted bolt boxes to ensure that no additional leverage effect occurs when the bolt connection force is transmitted from the left and right wall panels to the skin.

[0018] The present invention has the following advantages:

[0019] This invention discloses a slotted bolt box with low bolt leverage effect, which can greatly reduce the leverage effect, reduce bolt force by 18%, effectively improve the local tensile strength of both end frames, and can be applied to the connection of transverse butt bolts in the midpoint connection of the rocket body structure. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a point-type connection in an embodiment of the present invention;

[0021] Figure 2 This is a stress analysis diagram of a bolt box according to an embodiment of the present invention; wherein, 10-connection frame, 20-bolt box, 30-connection bolt;

[0022] Figure 3 This is a perspective view of a slotted bolt box with low bolt leverage effect according to an embodiment of the present invention;

[0023] Figure 4 This is a front view of a slotted bolt box with low bolt leverage effect according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram (front view) of the integrated molding of a slotted bolt box with low bolt leverage effect and a transverse docking frame in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram (back side) of the integrated molding of a slotted bolt box with low bolt leverage effect and a transverse mating frame in an embodiment of the present invention;

[0026] Figure 7 This is a front view of a slotted bolt box with low bolt leverage effect according to an embodiment of the present invention.

[0027] Figure 8 This is a side view of a slotted bolt box with low bolt leverage effect according to an embodiment of the present invention.

[0028] Figure 9This is a schematic diagram of a finite element model of a bolt box according to an embodiment of the present invention;

[0029] Figure 10 This is a schematic diagram of an applied load and boundary conditions in an embodiment of the present invention;

[0030] Figure 11 This is a composite deformation diagram of a slotted bolt box according to an embodiment of the present invention;

[0031] Figure 12 This is a composite deformation diagram of a conventional bolt box in an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed in the present invention will be described in further detail below with reference to the accompanying drawings.

[0033] To address the problem of bolt force amplification due to leverage effect in transversely separated point-connected bolts, this invention proposes a slotted bolt box with low bolt leverage effect. By creating a slot at the root, the bolt leverage effect is reduced, thereby significantly lowering the bolt load. For example... Figures 3-4 As shown, the slotted bolt box with low bolt leverage effect includes: a left wall plate 1, a right wall plate 2, a rear wall plate 3, a bottom plate 4, and a top plate 5. The left wall plate 1, right wall plate 2, rear wall plate 3, bottom plate 4, and top plate 5 form an open box; a bolt mounting hole 6 is formed in the center of the bottom plate 4; and a slot 7 is formed at the base of the box to reduce the bolt leverage effect.

[0034] In this embodiment, there are two ways to open the slit at the base of the box: 1) the slit 7 is opened on the rear wall panel 3, on the side close to the bottom plate 4; 2) the slit 7 is opened on the bottom plate 4, on the side close to the rear wall panel 3.

[0035] In this embodiment, the design requirements for the length L and width W of the gap 7 are as follows:

[0036] Length L = vertical distance between left wall panel 1 and right wall panel 2, to ensure that rear wall panel 3 or bottom plate 4 does not participate in the load-bearing under bolt tension.

[0037] The width W satisfies: 0 < W ≤ W max Among them, W max This indicates the maximum width without affecting the structural strength and rigidity of the bolt box. In other words, the width of gap 7 only needs to be sufficient to maintain the structural strength and rigidity of the bolt box, while also considering manufacturability. Furthermore, since this bolt box is often used for separating point-to-point bolt connections, the gap should not be too large to prevent the separated material from entering the rocket body structure through gap 7. For example, in a specific application scenario, the width W of gap 7 is 5–20 mm, ensuring the gap is open while also considering manufacturability.

[0038] In this embodiment, the edges of the gap 7 are chamfered to avoid stress concentration caused by the gap affecting the load-bearing capacity.

[0039] In this embodiment, several slotted bolt boxes are arranged in pairs, vertically, on the transverse docking frame of the arrow body structure where separation is required. The left wall plate 1 and right wall plate 2 of the slotted bolt box are integrally formed with the transverse docking frame, as shown below. Figures 5-6 As shown; at the same time, the outer skin of the transverse docking frame is set according to the spatial position of the docking holes of the upper and lower slotted bolt boxes to ensure that no additional lever effect occurs when the bolt connection force is transmitted from the left wall plate 1 and the right wall plate 2 to the skin.

[0040] In this embodiment, when an axial tensile load is applied to the slotted bolt box with low bolt leverage effect, the deformation of the slotted bolt box with low bolt leverage effect is as follows: Figures 7-8 As shown, comparison Figure 2 It can be seen that after adopting the slotted design, the deformation trend of the bolt box being pulled apart at the rear and squeezed at the front is significantly improved.

[0041] Based on the above embodiments, the load reduction effect of the slotted bolt box described in this invention will be compared and verified by finite element analysis:

[0042] Abaqus 2020 was used for pre- and post-processing, and the analysis was performed using the Static General module, considering material, geometric, and contact nonlinearities. Specifically:

[0043] Finite element model diagram as follows Figure 9 As shown, the bolt boxes and bolts in the model are simulated using solid elements, while the skin structure is simulated using shell elements. The bolts and bolt boxes are connected by contact, and the mating surfaces of the two bolt boxes are also connected by contact. The remaining connected parts of the model are joined by adhesive bonding. To improve computational efficiency, a local model including a single bolt is extracted for analysis.

[0044] The bottom joint of the model is fixed, and symmetrical boundary conditions are applied to both sides. All degrees of freedom except the axial direction are fixed at the loading point. A 13.2t axial tensile load is applied to the top of the model through a rigid surface. Figure 10 As shown.

[0045] The composite deformation diagram of the slotted bolt box described in this invention is as follows: Figure 11 As shown; the composite deformation diagram of the traditional bolt box is as follows. Figure 12 As shown in Table 1 below, the bolt force calculation results are as follows:

[0046] plan Axial force (N) Load reduction rate Traditional bolt box 162300 —— Slotted Bolt Box 132300 18％

[0047] Table 1. Schematic diagram of bolt force calculation results

[0048] The above comparative analysis shows that the open bolt box of the present invention significantly improves the phenomenon of root pulling and front end squeezing, and reduces bolt force by 18%.

[0049] Based on a thorough understanding of the lever generation principle, this invention differs from the traditional design method of strengthening the structure to increase load-bearing capacity. It improves load-bearing capacity by reducing structural materials and eliminating the force transmission path of the rear wall / bottom plate, so that the bolt connection force is transmitted from the left and right wall plates, fundamentally improving the lever effect of the bolt box connection.

[0050] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0051] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A slotted bolt box with low bolt leverage effect, characterized in that, include: Left wall panel (1), right wall panel (2), rear wall panel (3), bottom plate (4) and top plate (5); wherein, the left wall panel (1), right wall panel (2), rear wall panel (3), bottom plate (4) and top plate (5) form an open box; the bottom plate (4) has a bolt mounting hole (6) in the center; and a gap (7) is opened at the root of the box to reduce the bolt leverage effect.

2. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, The gap (7) is located on the back panel (3) on the side near the bottom panel (4).

3. The slotted bolt box with low bolt leverage effect according to claim 2, characterized in that, The length of the gap (7) is equal to the vertical distance between the left wall panel (1) and the right wall panel (2), ensuring that the rear wall panel (3) does not participate in the load under the action of bolt tension.

4. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, The gap (7) is opened on the bottom plate (4) and on the side near the back wall plate (3).

5. The slotted bolt box with low bolt leverage effect according to claim 4, characterized in that, The length of the gap (7) is equal to the vertical distance between the left wall panel (1) and the right wall panel (2), ensuring that the bottom plate (4) does not participate in the load under the action of bolt tension.

6. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, The width W of the gap (7) satisfies: 0 < W ≤ W max Among them, W max This indicates the maximum width without affecting the structural strength and stiffness of the bolt box.

7. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, The width W of the gap (7) is 5 to 20 mm.

8. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, The edges of the gap (7) are chamfered to avoid stress concentration caused by the gap affecting the load-bearing capacity.

9. The slotted bolt box with low bolt leverage effect according to claim 1, characterized in that, Several slotted bolt boxes are arranged in pairs, in an up-down layout, on the horizontal docking frame of the rocket body structure where separation is required.

10. The slotted bolt box with low bolt leverage effect according to claim 9, characterized in that, The left wall panel (1) and right wall panel (2) of the slotted bolt box are integrally formed with the transverse docking frame; at the same time, the outer skin of the transverse docking frame is set according to the spatial position of the docking holes of the upper and lower slotted bolt boxes to ensure that no additional lever effect occurs when the bolt connection force is transmitted from the left wall panel (1) and right wall panel (2) to the skin.

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