A composite structure embedded part for solid buoyancy materials and its design method

Abstract

This invention discloses a composite structure embedded part for solid buoyancy materials and its design method. The composite structure embedded part is composed of a metal part and a non-metal part. The non-metal part is cylindrical, with an axial blind hole machined at one end and an internal thread within the axial blind hole. The other end of the non-metal part has a frustum-shaped or frustum-shaped protrusion. The metal part is a sleeve with internal and external threads, connected to the axial blind hole of the non-metal part via threads. The buoyancy material has mounting holes for installing the composite structure embedded part, with the bottom of the mounting holes being either spherical or frustum-shaped. The composite structure embedded part is fixed to the mounting holes of the buoyancy material using adhesive, and a fixing adhesive layer fills the space between the frustum-shaped or frustum-shaped protrusion of the composite structure embedded part and the spherical or frustum-shaped bottom hole of the mounting hole. This invention can solve the problem of cracking of the buoyancy material around the embedded part due to differences in the elastic modulus of the materials.

Description

Technical Field

[0001] This invention belongs to the field of manufacturing and design technology of solid buoyancy material components, specifically relating to a composite structure embedded part for solid buoyancy materials and its design method. Background Technology

[0002] Solid buoyancy components are essential parts of various underwater vehicles, underwater robots, and other underwater equipment, providing the necessary positive buoyancy. Solid buoyancy materials are composite materials made of glass microspheres and resin, widely used underwater, providing buoyancy to underwater equipment and ensuring its safety. Connections between underwater equipment and buoyancy materials are required. To ensure a secure installation, high-strength metal materials are typically pre-embedded with the buoyancy material using adhesive bonding, followed by mechanical connection to the equipment. Alternatively, the buoyancy material may require hoisting during assembly and use. Currently, my country's Jiaolong, Yongshi, and Fentianzhe submersibles all use pre-embedded components made of pure titanium alloy as the connection and hoisting interface for buoyancy components. Figure 1 , 2 As shown.

[0003] According to investigations, the buoyancy materials around the embedded parts of the buoyancy components of the Jiaolong, Yongshi, and Fendouzhe submersibles all showed varying degrees of cracking. Due to the Fendouzhe submersible's deeper dives (up to 10,000 meters) and water pressure reaching 110 MPa, the cracks in the buoyancy materials around the embedded parts were more severe. The Fendouzhe manned submersible underwent multiple sea trials at depths of 10,000 meters. Post-trial inspections showed that, apart from cracks around the embedded parts of some components, its overall performance was intact. Our unit conducted a disassembly and inspection of the Fendouzhe, and found varying degrees of damage to the buoyancy materials around the embedded parts, manifested as ring-shaped cracks around the embedded parts (e.g., Figure 3 (as shown) and radial cracks (such as) Figure 4 (As shown).

[0004] Although the metal embedded parts of the buoyancy material components of the "Striver" are mainly used for lifting, cracks in the buoyancy material around the embedded parts have caused them to be unable to withstand the original lifting force, which has a great impact on the disassembly and assembly of the components. If the components fall during lifting due to cracks, it will cause significant economic losses. Summary of the Invention

[0005] In view of this, the present invention provides a composite structure embedded part for solid buoyancy materials and its design method, which can solve the problem of cracking of buoyancy material around the embedded part of buoyancy material component caused by the difference in elastic modulus of materials.

[0006] This invention is achieved through the following technical solution:

[0007] A composite structure embedded part for solid buoyancy materials, wherein the composite structure embedded part is composed of metal parts and non-metal parts;

[0008] The non-metallic part has a cylindrical structure. One end of the non-metallic part is machined with an axial blind hole and an internal thread is machined in the axial blind hole. The other end of the non-metallic part is provided with a frustum-shaped protrusion or a frustum-shaped protrusion.

[0009] The metal part is a sleeve with internal and external threads. The metal part is connected to the axial blind hole of the non-metallic part by threads to form the composite structure embedded part; the internal thread of the metal part is used for threaded connection with the application object.

[0010] The peripheral equipment is a buoyancy material; the buoyancy material is machined with mounting holes for installing composite structure embedded parts, and the bottom of the mounting holes is a spherical bottom hole or a frustum-shaped bottom hole; the composite structure embedded parts are fixed in the mounting holes of the buoyancy material by adhesive, and the frustum-shaped protrusions or spherical protrusions of the composite structure embedded parts are filled with a fixing adhesive layer between them and the spherical bottom hole or frustum-shaped bottom hole of the mounting holes.

[0011] Furthermore, the metal parts are made of TC4 titanium alloy, and the non-metal parts are made of PEEK material.

[0012] Furthermore, two or more circumferentially distributed overflow venting grooves are machined on the outer circumferential surface of the non-metallic part, and each overflow venting groove is arranged along the length direction of the non-metallic part.

[0013] Furthermore, the outer circumferential surface of the non-metallic part is machined with fine threads or knurling.

[0014] Furthermore, the top of the metal part is provided with two oppositely arranged or four circumferentially distributed mounting slots. The two oppositely arranged mounting slots form a straight groove, and the four circumferentially distributed mounting slots form a cross-shaped groove.

[0015] A design method for embedded components of composite structures using solid buoyancy materials, the steps of which are as follows:

[0016] Step 1: Measure the density ρ of the materials for the proposed non-metallic and metallic parts. 非 and ρ 金 Bulk modulus E 非 and E 金 Performance testing; ρ 非 ρ is the density of the non-metallic part. 金 E is the density of the metal part. 非 E represents the bulk modulus of elasticity of a non-metallic component. 金 The bulk modulus of elasticity of the metal part;

[0017] The water absorption rate (a) of the proposed non-metallic parts will also be measured.非 Tensile strength Rm 非 Water pressure resistance P 水非 The test was conducted to determine the pressure resistance of the non-metallic parts, i.e., the actual operating pressure P. 实 P 实 ×(1.2~1.5)≤P 水非 After holding under actual water pressure for 24 hours, the water absorption rate 'a' of non-metallic parts... 非 ≤1%, the water pressure resistance P of non-metallic parts 水非 Greater than 200 MPa; tensile strength

[0018] Step 2: Based on the structure of the application object of the composite structure embedded part, design the interface form between the metal part and the application object and the size of the metal part: the metal part adopts the structure form of a sleeve with internal and external threads. The internal thread of the metal part is a right-hand thread with specification Md, the external thread of the metal part is a left-hand thread with specification Md1, and the axial length of the metal part is h.

[0019] Step 3: Design the structural form and dimensions of the non-metallic parts in the composite structure embedded parts: The non-metallic parts adopt a cylindrical structure with an axial blind hole machined at the top. The outer diameter of the non-metallic parts is (2~3)×d1. The internal thread of the axial blind hole is a left-hand thread with a specification of Md1. The axial length of the axial blind hole is h+5mm. The bottom of the non-metallic parts is provided with a frustum-shaped protrusion or a frustum-shaped protrusion. The total axial length H of the non-metallic parts is H=h+5mm+(1.5~2.5)×d1.

[0020] Step 4: Design the structure and dimensions of the mounting holes on the buoyancy material for bonding the embedded parts of the composite structure: the bottom of the mounting hole is a spherical bottom hole or a frustum-shaped bottom hole, and the total axial length of the mounting hole is designed to be H+2mm.

[0021] Step 5: Determine the connection method between metal and non-metal parts in the embedded parts of the composite structure: the metal and non-metal parts adopt a connection method that combines threading and bonding, that is, apply adhesive to the external thread of the metal part before screwing the metal part into the non-metal part.

[0022] Step Six: Simulate and verify the strength of the composite structure embedded parts and buoyancy material: Establish a three-dimensional model of the assembled composite structure embedded parts and buoyancy material, and perform simulation calculations on 1 / 4 of the model. If the simulation results show that the maximum stress on the three-dimensional model is less than the tensile strength of the buoyancy material, it can be guaranteed that the buoyancy material will not crack, and proceed to Step Seven; if the simulation results show that the maximum stress on the three-dimensional model is greater than or equal to the tensile strength of the buoyancy material, it is necessary to return to Step One and redesign the composite structure embedded parts.

[0023] Step 7: Process the sample of the composite structure embedded part. The size of the buoyancy material should be no less than 3 to 5 times the size of the composite structure embedded part. Adhere the sample of the composite structure embedded part into the mounting hole of the buoyancy material. Conduct no less than 10 impact tests on the assembled buoyancy material and the sample of the composite structure embedded part under the maximum working external water pressure. If no cracking occurs, it proves that the composite structure embedded part is reasonable and feasible.

[0024] Furthermore, the top of the metal part is provided with two oppositely arranged or four circumferentially distributed mounting slots. The two oppositely arranged mounting slots form a straight groove, and the four circumferentially distributed mounting slots form a cross-shaped groove.

[0025] Furthermore, the bottom of the axial blind hole of the non-metallic part is a conical hole, and the height of the conical hole is h+5mm+(1~2)×d1.

[0026] Furthermore, the outer circumferential surface of the non-metallic part is machined with 2 to 4 circumferentially distributed overflow venting grooves; each overflow venting groove is arranged along the length direction of the non-metallic part, and the size of each overflow venting groove is 2mm×2mm×H; the outer circumferential surface of the non-metallic part is machined with fine thread or knurling.

[0027] Beneficial effects:

[0028] (1) The present invention provides a composite structure embedded part for solid buoyancy materials. The embedded part improves the difference in elastic modulus between metal materials and buoyancy materials by combining non-metallic and metal parts, while taking into account the high strength and durability of the metal material threads. This solves the problem of cracking of brittle solid buoyancy materials caused by the use of metal embedded parts under high water pressure conditions.

[0029] (2) Two or more circumferentially distributed overflow venting grooves are machined on the outer circumferential surface of the non-metallic part of the present invention. After the pre-embedded part of the composite structure is gradually embedded into the mounting hole of the buoyancy material filled with adhesive, the excess adhesive in the mounting hole is discharged through the overflow venting grooves on the outer circumferential surface of the non-metallic part, thereby realizing the removal of excess adhesive and gas when the non-metallic part is bonded to the buoyancy material.

[0030] (3) The outer circumferential surface of the non-metallic part of the present invention is machined with fine thread or knurling, which can increase the roughness of the non-metallic part and increase the bonding reliability between the non-metallic part and the buoyancy material when the non-metallic part is installed in the mounting hole of the buoyancy material.

[0031] (4) The top of the metal part of the present invention is provided with a slotted groove or a cross-shaped groove, which makes it easy to tighten the metal part into the non-metal part with a slotted screwdriver or a cross-shaped screwdriver, thereby improving the convenience of operation.

[0032] (5) This invention provides a design method for a composite structure embedded part for solid buoyancy material. The composite structure embedded part and its buoyancy material obtained by this design method will no longer crack without reducing the pull-out torsional strength and wear resistance of the embedded part. The product qualification rate is significantly improved to 100%, which solves the problem of easy cracking of the solid buoyancy material component of the bonded embedded part under high water pressure, especially under full ocean depth conditions, and provides a solid guarantee for the reliability of deep-sea exploration equipment installation. Attached Figure Description

[0033] Figure 1 Here is a structural diagram of titanium alloy embedded parts in the background art;

[0034] Figure 2 This is a schematic diagram of the bonding between the embedded part and the buoyancy material in the background art.

[0035] Figure 3 This is a damage diagram of annular cracks occurring in the floating material surrounding the embedded part in the background art.

[0036] Figure 4 This is a damage diagram showing radial cracks in the floating material surrounding the embedded part in the background art.

[0037] Figure 5 This is a structural composition diagram of the composite structure embedded part of the present invention;

[0038] Figure 6 This is a structural diagram of the non-metallic component of the present invention;

[0039] Figure 7 This is a structural diagram of the metal part of the present invention;

[0040] Figure 8 This is a schematic diagram of the bonding between the composite structure embedded part and the buoyancy material of the present invention;

[0041] Figure 9 This is a simulation calculation diagram of the composite structure embedded part of the present invention;

[0042] Figure 10-11 The test results diagram shows the sample of the embedded part of the composite structure;

[0043] Among them, 1-metal part, 2-non-metal part, 3-mounting slot, 4-overflow venting groove, 5-buoyancy material, 6-adhesive layer. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0045] Example 1:

[0046] This embodiment provides a composite structure embedded part for solid buoyancy materials. See attached document. Figure 5 The composite structure embedded part is composed of a metal part 1 and a non-metal part 2. The metal part 1 is made of TC4 titanium alloy and the non-metal part 2 is made of PEEK material.

[0047] See appendix Figure 6 The non-metallic part 2 has a cylindrical structure. One end of the non-metallic part 2 is machined with an axial blind hole, and an internal thread is machined inside the axial blind hole. The bottom of the axial blind hole is a conical hole with a cone angle of 120°. The other end of the non-metallic part 2 is provided with a frustum-shaped protrusion or a truncated cone-shaped protrusion. If it is a frustum-shaped protrusion, the diameter of the large end of the frustum-shaped protrusion is equal to the outer diameter of the non-metallic part 2, the diameter of the small end of the frustum-shaped protrusion is 5mm, and the cone angle of the frustum-shaped protrusion is also 120°. Two or more circumferentially distributed overflow venting grooves 4 are machined on the outer circumferential surface of the non-metallic part 2. Each overflow venting groove 4 is arranged along the length direction of the non-metallic part 2. In this embodiment, four overflow venting grooves 4 are used. The outer circumferential surface of the non-metallic part 2 is machined with fine threads or knurling to increase the roughness of the non-metallic part 2.

[0048] See appendix Figure 7 The metal part 1 is a sleeve with internal and external threads, wherein the axial length of the internal thread is less than the axial length of the sleeve, and the axial length of the external thread is equal to the axial length of the sleeve. The end of the sleeve wall at the end where the internal thread is located is provided with two oppositely arranged or four circumferentially distributed mounting grooves 3. The two oppositely arranged mounting grooves 3 form a straight groove, and the four circumferentially distributed mounting grooves 3 form a cross-shaped groove. The metal part 1 is threaded into the axial blind hole of the non-metallic part 2 to form the composite structure embedded part. The straight groove or cross-shaped groove facilitates tightening the metal part 1 into the non-metallic part 2.

[0049] See appendix Figure 8 The buoyancy material 5 is machined with mounting holes for installing the composite structure embedded parts. The bottom of the mounting holes is either spherical or frustum-shaped. The composite structure embedded parts are fixed in the mounting holes of the buoyancy material 5 with adhesive. The frustum-shaped or spherical protrusions of the composite structure embedded parts are filled with a fixing adhesive layer between them and the spherical or frustum-shaped bottom holes of the mounting holes. The process of fixing the composite structure embedded parts in the mounting holes of the buoyancy material 5 is as follows: first, adhesive is filled into the mounting holes of the buoyancy material 5; then, the composite structure embedded parts are gradually embedded into the mounting holes filled with adhesive; finally, the excess adhesive in the mounting holes is discharged through the overflow venting groove 4 on the outer circumference of the non-metallic part 2.

[0050] Example 2:

[0051] Based on Example 1, this embodiment provides a design method for a composite structure embedded part for solid buoyancy materials. The steps of this design method are as follows:

[0052] Step 1: Measure the density ρ of the materials of the proposed non-metallic part 2 and the metallic part 1. 非 and ρ 金 Bulk modulus E 非 and E 金 Performance testing; among them, the material of non-metallic part 2 should be selected to be anti-aging and have a long service life; the material of metallic part 1 should preferably be a corrosion-resistant material, such as titanium alloy or stainless steel; ρ 非 Let ρ be the density of non-metallic component 2. 金 Let E be the density of metal part 1. 非 E is the bulk modulus of elasticity of non-metallic part 2. 金 Let be the bulk modulus of elasticity of metal part 1;

[0053] The water absorption rate (a) of the proposed non-metallic component 2 will also be measured. 非 Tensile strength Rm 非 Water pressure resistance P 水非 The test was conducted to determine the pressure resistance of non-metallic component 2, i.e., the actual operating pressure P. 实 P 实 ×(1.2~1.5)≤P 水非 After holding under actual water pressure for 24 hours, the water absorption rate a of non-metallic part 2 is... 非 ≤1%, the water pressure resistance P of non-metallic part 2 水非 Generally greater than 200 MPa; tensile strength

[0054] Step 2: Based on the structure of the application object of the composite structure embedded part, design the interface form (generally threaded) between the metal part 1 and the application object, as well as the dimensions of the metal part 1 (thread specification M and length h): In this embodiment, the application object is a screw rod. Therefore, the metal part 1 adopts a sleeve structure with internal and external threads. The internal thread of the metal part 1 is a right-hand thread with specification Md, and the external thread of the metal part 1 is a left-hand thread with specification Md1. Md1 is generally one specification larger than Md, but a larger specification can be selected according to actual needs. The internal and external threads of the metal part 1 have different directions of rotation to avoid the two threads from unscrewing. The axial length of the metal part 1 is h. The top of the metal part 1 is machined with a slotted groove or a cross-shaped groove to facilitate the installation of the metal part 1 into the non-metallic part 2.

[0055] Step 3: Design the structural form and dimensions of the non-metallic component 2 in the composite structure embedded parts: The structural form and dimensions of the non-metallic component 2 are key to solving the cracking problem of the buoyancy material 5. The non-metallic component 2 adopts a cylindrical structure with an axial blind hole machined at the top. The outer diameter of the non-metallic component 2 is (2~3)×d1. The internal thread of the axial blind hole is a left-hand thread with a specification of Md1. The axial length of the axial blind hole (excluding the conical hole at the bottom) is h+5mm. The bottom depth of the axial blind hole (i.e., the height of the conical hole) is h+5mm+(1~2)×d1. The bottom of the non-metallic component 2 is provided with a circular... Frustum-shaped or frustum-shaped protrusions are used to reduce the structural stress of the embedded parts in the composite structure; the total axial length H of the non-metallic part 2 is h + 5mm + (1.5~2.5)×d1 (the total axial length includes the height of the frustum-shaped or frustum-shaped protrusions); the outer circumferential surface of the non-metallic part 2 is machined with fine threads or knurling to increase the roughness of the non-metallic part 2, and 2 to 4 circumferentially distributed overflow venting grooves 4 are machined on the outer circumferential surface of the non-metallic part 2 to remove excess adhesive and gas when the non-metallic part 2 is bonded to the buoyancy material 5; the dimensions of each overflow venting groove 4 are 2mm×2mm×H;

[0056] Step 4: Design the structure and dimensions of the mounting holes on the buoyancy material 5 for bonding the embedded parts of the composite structure: the bottom of the mounting hole is a spherical bottom hole or a frustum-shaped bottom hole, and the total axial length of the mounting hole is designed to be H+2mm; the diameter of the mounting hole is slightly larger than the outer diameter of the non-metallic part 2.

[0057] Step 5: Determine the connection method between metal part 1 and non-metal part 2 in the embedded parts of the composite structure: metal part 1 and non-metal part 2 adopt a connection method that combines threading and bonding, that is, apply adhesive to the external thread of metal part 1 before screwing metal part 1 into non-metal part 2.

[0058] Step Six: Simulate and verify the strength of the composite structure embedded parts and buoyancy material 5: Establish a three-dimensional model of the assembled composite structure embedded parts and buoyancy material 5, and perform simulation calculations on 1 / 4 of the model. If the simulation results show that the maximum stress on the three-dimensional model is less than the tensile strength of the buoyancy material 5, it can be guaranteed that the buoyancy material 5 will not crack, and proceed to Step Seven; if the simulation results show that the maximum stress on the three-dimensional model is greater than or equal to the tensile strength of the buoyancy material 5, then it is necessary to return to Step One and redesign the composite structure embedded parts; the simulation results of this embodiment are as follows. Figure 9 As shown, the buoyancy material 5 is subjected to compressive stress but not tensile stress, and will not crack due to tensile stress.

[0059] Step 7: Process a sample of the composite structure embedded part. The size of the buoyancy material 5 should be no less than 3 to 5 times the size of the composite structure embedded part. Adhere the sample of the composite structure embedded part into the mounting hole of the buoyancy material 5. Perform at least 10 impact tests on the assembled buoyancy material 5 and the sample of the composite structure embedded part under the maximum working external water pressure. If no cracking occurs, the composite structure embedded part is deemed reasonable and feasible. In this embodiment, the assembled buoyancy material 5 and the sample of the composite structure embedded part are subjected to 10 impact tests under the maximum working external water pressure (120 MPa) to further verify the reasonableness and feasibility of the composite structure embedded part. No cracking occurs. Figure 10-11 As shown.

[0060] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite structural insert for solid buoyancy material, characterized by, The composite structure embedded part is composed of a metal part and a non-metal part; The non-metal part is in a cylindrical structure, one end of the non-metal part is provided with an axial blind hole, the axial blind hole is provided with an internal thread, and the other end of the non-metal part is provided with a circular truncated cone-shaped protrusion or a spherical truncated cone-shaped protrusion; The metal part is a sleeve provided with an internal thread and an external thread, the metal part is connected in the axial blind hole of the non-metal part through the threads, and the metal part and the non-metal part form the composite structure embedded part; the internal thread of the metal part is used for thread connection with an application object; The peripheral device is a buoyancy material, the buoyancy material is provided with a mounting hole for mounting the composite structure embedded part, the bottom of the mounting hole is a spherical bottom hole or a circular truncated cone-shaped bottom hole, the composite structure embedded part is fixed in the mounting hole of the buoyancy material through a glue, and the circular truncated cone-shaped protrusion or the spherical truncated cone-shaped protrusion of the composite structure embedded part is filled with a glue layer for fixing between the spherical bottom hole or the circular truncated cone-shaped bottom hole of the mounting hole.

2. A composite structural insert for solid buoyancy material as defined in claim 1, wherein The metal part is made of TC4 titanium alloy material, and the non-metal part is made of PEEK material.

3. A composite structural insert for solid buoyancy material as defined in claim 1, wherein The outer circumferential surface of the non-metal part is provided with two or more than two circumferentially distributed glue overflow exhaust grooves, and each glue overflow exhaust groove is arranged along the length direction of the non-metal part.

4. A composite structural insert for solid buoyancy material according to any one of claims 1 to 3, wherein The outer circumferential surface of the non-metal part is provided with fine thread or knurling.

5. A composite structural insert for solid buoyancy material according to any one of claims 1 to 3, wherein The top of the metal part is provided with two oppositely arranged mounting clamping grooves or four circumferentially distributed mounting clamping grooves, the two oppositely arranged mounting clamping grooves form a linear slot, and the four circumferentially distributed mounting clamping grooves form a cross-shaped slot.

6. A method for designing a composite structural insert for solid buoyancy material, based on the composite structural insert according to any one of claims 1 to 5, characterized in that The steps of the design method are as follows: Step 1. The densities p of the material of the non-metallic part and the material of the metallic part to be used are measured 非 and p 金 , the volume elastic modulus E 非 and E 金 performance are tested; p 非 is the density of the non-metallic part, p 金 is the density of the metallic part, E 非 is the volume elastic modulus of the non-metallic part, E 金 is the volume elastic modulus of the metallic part; The non-metallic piece to be used is also subjected to a test of water absorption a 非 , tensile strength Rm 非 , water pressure resistance P 水非 , and the pressure resistance of the non-metallic piece, i.e. the actual use pressure resistance P 实 , is determined, P 实 ×(1.2-1.5)≤P 水非 ; after maintaining the pressure for 24 hours at the actual use water pressure, the water absorption a 非 of the non-metallic piece is ≤1%, and the water pressure resistance P 水非 of the non-metallic piece is greater than 200 MPa; the tensile strength In step two, according to the structure of the application object of the composite structure embedded part, the interface form of the metal part and the application object and the size of the metal part are designed: the metal part adopts the structure form of a sleeve provided with an internal thread and an external thread, the internal thread of the metal part is a right-handed thread with a specification of Md, the external thread of the metal part is a left-handed thread with a specification of Md1, and the axial length of the metal part is h; In step three, the structure form and size of the non-metal part in the composite structure embedded part are designed: the non-metal part adopts a cylindrical structure provided with an axial blind hole at the top, the outer diameter of the non-metal part is (2-3)×d1, the internal thread of the axial blind hole is a left-handed thread with a specification of Md1, the axial length of the axial blind hole is h+5mm, the bottom of the non-metal part is provided with a circular truncated cone-shaped protrusion or a spherical truncated cone-shaped protrusion, and the total axial length H of the non-metal part is h+5mm+(1.5-2.5)×d1; In step four, the structure and size of the mounting hole for bonding the composite structure embedded part on the buoyancy material are designed: the bottom of the mounting hole is a spherical bottom hole or a circular truncated cone-shaped bottom hole, and the total axial length of the mounting hole is designed as H+2mm; In step five, the connection mode of the metal part and the non-metal part in the composite structure embedded part is determined: the metal part and the non-metal part adopt a connection mode of thread connection and bonding, that is, the metal part is coated with glue on the external thread before being screwed into the non-metal part. Step six, the composite structure embedded part and the buoyancy material strength are simulated and verified: the three-dimensional model of the assembled composite structure embedded part and the buoyancy material is established, and the 1 / 4 model is simulated and calculated, if the simulation result shows that the maximum stress of the three-dimensional model is less than the tensile strength of the buoyancy material, the cracking phenomenon of the buoyancy material can be prevented, and step seven is executed; if the simulation result shows that the maximum stress of the three-dimensional model is greater than or equal to the tensile strength of the buoyancy material, the composite structure embedded part needs to be redesigned in step one; Step seven, the sample of the composite structure embedded part is processed, the size of the buoyancy material is not less than 3-5 times the size of the composite structure embedded part, the sample of the composite structure embedded part is bonded in the mounting hole of the buoyancy material, and the assembled buoyancy material and the sample of the composite structure embedded part are subjected to not less than 10 impact tests under the maximum working external water pressure, if no cracking phenomenon occurs, it is proved that the composite structure embedded part is reasonable and feasible.

7. A method of designing a composite structural insert for a solid buoyancy material according to claim 6, wherein, The top of the metal part is provided with two oppositely arranged or four circumferentially distributed mounting clamping grooves, the two oppositely arranged mounting clamping grooves form a linear slot, and the four circumferentially distributed mounting clamping grooves form a cross-shaped slot.

8. A method of designing a composite structural insert for a solid buoyancy material according to claim 6, wherein The bottom of the axial blind hole of the non-metal part is a conical hole, and the height of the conical hole is h+5mm+(1-2)×d1.

9. A method of designing a composite structural insert for a solid buoyancy material according to any one of claims 6 to 8, wherein, The outer circumferential surface of the non-metal part is provided with 2-4 circumferentially distributed glue overflow exhaust grooves; each glue overflow exhaust groove is arranged along the length direction of the non-metal part, and the size of each glue overflow exhaust groove is 2mm×2mm×H; the outer circumferential surface of the non-metal part is provided with fine thread or knurling. The top of the metal part is provided with two oppositely arranged or four circumferentially distributed mounting clamping grooves, the two oppositely arranged mounting clamping grooves form a linear slot, and the four circumferentially distributed mounting clamping grooves form a cross-shaped slot.

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