A calculation method for damage deformation of ship density characteristic structure

Abstract

A method for calculating the damage and deformation of a ship's tightness characteristic structure belongs to the field of ship protection technology and solves the problems of low accuracy and large amount of calculation in the damage calculation of existing watertight characteristic components. The method of the invention comprises: establishing a numerical sub-model including a watertight characteristic structure and its artificial boundary, simulating the deformation characteristics of watertight doors and watertight hatch covers under actual working conditions by applying impact acceleration under real-scale working conditions; the impact acceleration is derived from a scaled model test, which can ensure the correctness, credibility and accuracy of the calculation results; comparing the sub-model numerical simulation results with the proposed tightness damage criterion to obtain the tightness structure damage results. The present invention is suitable for calculating the damage and deformation of a ship's tightness characteristic structure under near-field underwater explosion loads.

Description

Technical Field

[0001] The present application relates to the field of ship protection technology, and in particular to the damage and protection of ship structures under near-field underwater explosion loads. Background Art

[0002] In actual naval battles, ships are attacked by enemy underwater weapons and local breaches occur, causing water to enter, which greatly threatens their anti-sinking and vitality. Since the 20th century, researchers from various countries have conducted a series of studies on the causes of the sinking of war-damaged ships, and found that the scope of water inflow into their internal compartments depends on the damage scope of the structural boundary and the damage scope of the tightness characteristic structure (watertight doors, watertight hatch covers).

[0003] Structural tightness damage requires that local areas of the structure reach a cracking state, which can usually be observed with the naked eye; characteristic structural damage to tightness usually means that the deformation of the structure around the seal exceeds the design threshold, causing leakage in the structure. The range of tightness damage to watertight doors and watertight hatch covers is usually much larger than the range of physical damage to structural tightness.

[0004] There are usually two common methods to examine the damage characteristics of watertight characteristic components: test methods and simulation methods. Conventional scaled model test methods cannot consider the local characteristics of watertight characteristic components. Numerical simulation methods usually require hundreds of millions of grids to simulate the watertight characteristic structure inside the compartment. The existing computing resources and computing time cannot meet the requirements. Therefore, establishing a calculation method for the damage deformation of ship tightness characteristic structures is of great significance for the evaluation of the tightness damage range. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of low accuracy and large amount of calculation in the damage calculation of existing watertight characteristic components, and to provide a method for calculating the damage deformation of ship watertight characteristic structures.

[0006] The present invention is implemented by the following technical solutions. On the one hand, the present invention provides a method for calculating the damage deformation of a ship's tightness characteristic structure, the method comprising:

[0007] Step 1: Design an underwater explosion scale model test, obtain the actual thickness, size, charge radius, and explosion distance of the test model according to the underwater explosion scale similarity relationship, and determine the test conditions;

[0008] Step 2: Determine the size and specifications of the watertight characteristic structures to be verified according to the locations and models of the watertight characteristic structures of the large ship, wherein the watertight characteristic structures include watertight doors and watertight hatch covers;

[0009] Step 3, arranging an acceleration sensor below the equivalent coaming of the watertight characteristic structure;

[0010] Step 4: Conduct an underwater explosion scaled model test, and obtain the test impact acceleration time history curve at the watertight door coaming and watertight hatch cover coaming positions of the scaled model through an acceleration sensor;

[0011] Step 5: Establish a simplified numerical simulation sub-model of the watertight door and watertight hatch cover, including:

[0012] Determine the structural features and classify them as equivalent according to their ability to resist deformation, the structural features include coamings, door panels, cover panels, stiffeners, hinges, linkage clips, wing clips, butterfly clips and rubber gaskets, among which the wing clips in the watertight doors and the butterfly clips in the watertight hatch covers are mainly composed of bolts, nuts, pressure plates and bottom pins;

[0013] An artificial boundary of a sub-model is established, wherein the structural boundary of the sub-model is selected as the smallest unit cell surrounded by the longitudinal wall and the reinforcement ribs near the watertight characteristic structure on the deck;

[0014] The strength of the internal and external pressures of the structure are checked according to the sub-model tightness design values;

[0015] Step 6: convert the impact acceleration measured by the scaled model test in step 4 according to the underwater explosion scaled similarity relationship to obtain the impact acceleration time history curve at the real scale, load the converted impact acceleration onto the bottom boundary of the sub-model coaming, calculate the deformation response of the watertight door and watertight hatch cover model under the action of the local impact load through nonlinear finite element numerical simulation software, and obtain the deformation result;

[0016] Step 7: Based on the comparison between the deformation result and the watertight characteristic structure damage judgment basis, it is judged whether the watertight doors and watertight hatch covers of the large ship are damaged in tightness under the action of the explosion impact load.

[0017] Furthermore, in step 1, the test model and the prototype satisfy the following relationship:

[0018]

[0019] Among them, L is the main scale of the model, t is the thickness of the cabin plate, r is the radius of the charge, d is the explosion distance, λ is the scale ratio, subscript p represents the prototype, and subscript m represents the test model;

[0020] In step 6, the acceleration history curve and the prototype satisfy the following conversion relationship:

[0021]

[0022] Where a is acceleration, t is action time, λ is scale ratio, subscript p represents prototype, and subscript m represents test model.

[0023] Furthermore, step 2 also includes: based on the position and model of the watertight door and the watertight hatch cover, the watertight characteristic structure cover and the coaming are mass equivalent, and the ratio of the mass after the equivalent to the mass before the equivalent is λ 3 .

[0024] Further, the acceleration sensor of the watertight door is arranged at the junction of the equivalent surrounding wall and the longitudinal wall of the watertight door;

[0025] The acceleration sensor of the watertight hatch cover is arranged at the junction of the hatch cover equivalent wall and the deck.

[0026] Furthermore, the equivalent blind plate of the watertight door is connected to the longitudinal wall through the equivalent surrounding wall in the middle, and the equivalent blind plate of the hatch cover is connected to the deck through the equivalent surrounding wall in the middle; the connection method between the equivalent blind plate, equivalent surrounding wall and longitudinal wall of the watertight door is welding; the connection method between the equivalent blind plate, equivalent surrounding wall and deck of the watertight hatch cover is welding.

[0027] Furthermore, the simplified numerical simulation sub-model of the watertight door and the watertight hatch cover established in step 5 needs to be simplified according to the structural deformation resistance capability, including:

[0028] The spring clips, spring handles and spring brackets on the watertight doors are secondary load-bearing structures in structural deformation and are equivalent to the watertight door panels by the method of mass equivalence;

[0029] The handles, gas struts, stoppers and grounding devices on the watertight hatch covers are secondary load-bearing structures in structural deformation and are equivalent to the watertight hatch cover door panels by the method of mass equivalence;

[0030] The hinges and wing clips on the watertight doors, as well as the hinges and butterfly clips on the watertight hatch covers, are the main load-bearing structures in structural deformation, so their basic shape features are retained and three-dimensional solid modeling is performed;

[0031] For the watertight door linkage clip, it is the main load-bearing structure in structural deformation, while the clip linkage mechanism is a secondary load-bearing structure, which is equivalent to the watertight door panel in a mass equivalent manner;

[0032] For the rubber gasket, modeling is performed according to its structural form, taking into account the bonding relationship between the rubber gasket and the cover plate, and the contact relationship between the rubber gasket and the enclosure.

[0033] Furthermore, in step 5, the engagement state of the bolt and nut is ignored, and an integrated modeling technology is used to calculate the forces between the bolt and the pressure plate, and between the bolt and the bottom pin through a penalty force contact algorithm.

[0034] Furthermore, in step 5, a bolt pre-tightening force is applied in the clips around the cover plate, and the pre-tightening force is transmitted to the rubber gasket through the pressure plate and the cover plate, and the sub-model achieves a watertight effect after the rubber gasket is squeezed.

[0035] Furthermore, in step 5, the internal pressure and external pressure of the sub-model are checked respectively according to the sub-model tightness design value, specifically including: applying a constant pressure load to the sub-model cover plate, the pressure amplitude adopts the pressure design value corresponding to the structure, and the bottom node of the enclosure adopts a rigid constraint; if the calculation results show no leakage and permanent deformation, it proves that the structural modeling is accurate and the sub-model is established.

[0036] Furthermore, the watertight characteristic structural damage in step 7 is judged based on the relative position of the rubber gasket and the coaming, including:

[0037] If during the deformation of the tightness structure, the rubber gasket and the bottom enclosure are separated transiently, but the final relative position is close, it is judged that the structure is leaking;

[0038] If there is partial separation between the final relative position of the rubber gasket and the bottom enclosure, the structure is judged to be leakproof.

[0039] Beneficial effects of the present invention:

[0040] The present invention provides a method for calculating the damage deformation of watertight doors and watertight hatch covers under near-field underwater explosion loads based on a combination of scaled model test-similarity relationship conversion-tightness characteristic structure sub-model numerical simulation.

[0041] The damage deformation calculation method of the watertight characteristic structure based on the scaled model test of the near-field underwater explosion of the ship structure of the present invention has a reasonable process, establishes a numerical sub-model including the watertight characteristic structure and the bulkhead where it is located, and simulates the impact environment characteristics of the watertight door and the watertight hatch cover under actual working conditions by applying impact acceleration. Based on the scaled model test, the correctness, credibility and accuracy of the calculation results can be guaranteed.

[0042] The present invention proposes an equivalent verification method for watertight doors and watertight hatch covers based on scaled model tests. The method has a reasonable calculation process, performs refined modeling of the watertight pre-tightening structure, and can reflect the deformation response characteristics of the watertight door structure under the complex environment of underwater explosion.

[0043] The invention is applicable to the calculation of damage deformation of ship tightness characteristic structures (watertight doors, watertight hatch covers) under near-field underwater explosion loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the embodiments are briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0045] Figure 1 This application discloses an equivalent verification method for watertight doors and watertight hatch covers based on a scaled model test;

[0046] Figure 2 This is a schematic diagram of the equivalent structure of the test model watertight door of this application;

[0047] Figure 3 This is a schematic diagram of the overall equivalent structure of the test model watertight hatch cover of this application;

[0048] Figure 4 In the figure, a is a schematic diagram of the arrangement of the acceleration measuring points of the watertight door of the test model of the present application, and b is a schematic diagram of the arrangement of the acceleration measuring points of the watertight hatch cover of the test model of the present application;

[0049] Figure 5 In the figure, a is a schematic diagram of a watertight door structure sub-model of the present application, and b is a schematic diagram of a watertight hatch cover structure sub-model of the present application.

[0050] Figure 6 In the figure, a is the damage calculation result of the watertight door structure sub-model of the present application, and b is the damage calculation result of the watertight hatch cover structure sub-model of the present application.

[0051] In the figure:

[0052] 1 is the longitudinal wall, 2 is the watertight door equivalent blind plate, 3 is the watertight door equivalent surrounding wall, 4 is the deck, 5 is the watertight hatch cover equivalent blind plate, 6 is the watertight hatch cover equivalent surrounding wall, and 7 is the test model acceleration measurement point. DETAILED DESCRIPTION

[0053] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0054] Embodiment 1: A method for calculating damage deformation of a ship's density characteristic structure, the method comprising:

[0055] Step 1: Conduct an underwater explosion reduction model test, obtain the actual thickness, size, charge radius, and explosion distance of the test model based on the underwater explosion reduction similarity relationship, and determine the test conditions;

[0056] Step 2: Determine the size and specifications of the watertight characteristic structures to be verified according to the locations and models of the watertight characteristic structures of the large ship, wherein the watertight characteristic structures include watertight doors and watertight hatch covers;

[0057] Step 3, arranging acceleration sensors under the two side panels of the watertight characteristic structure;

[0058] Step 4: Conduct an underwater explosion scaled model test, obtain the impact acceleration at the scaled model watertight door coaming and watertight hatch cover coaming positions through an acceleration sensor, and convert the input impact acceleration of the full-scale watertight door and watertight hatch cover through the underwater explosion similarity relationship;

[0059] Step 5: Establish sub-models of watertight doors and watertight hatch covers, including:

[0060] Determine structural features, wherein the structural features include coamings, door panels, cover panels, stiffeners, hinges, linkage clips, wing clips, butterfly clips and rubber gaskets, wherein the wing clips in the watertight door and the butterfly clips in the watertight hatch cover are mainly composed of bolts, nuts, pressure plates and bottom pins;

[0061] Establishing an artificial boundary of a sub-model, wherein the artificial boundary of the sub-model is selected as the smallest unit cell surrounded by the longitudinal wall and the reinforcement ribs near the watertight characteristic structure on the deck;

[0062] Step 6: Load the input impact acceleration of the full-scale watertight door and the watertight hatch cover onto the artificial boundary of the sub-model, and perform deformation response of the watertight door and the watertight hatch cover model under the action of local impact load by nonlinear finite element numerical simulation software to obtain deformation results;

[0063] Step 7: Based on the comparison between the deformation result and the watertight door tightness characteristic damage judgment basis, it is judged whether the watertight doors and watertight hatch covers of large ships are damaged under the action of the explosion impact load.

[0064] It should be noted that the hatch cover is on the deck and the watertight door is located on the longitudinal wall. Its structural boundary can be regarded as a plate surrounded by the deck, the watertight hatch cover on the longitudinal wall, and the reinforcement ribs near the watertight door.

[0065] This embodiment provides a method for calculating the damage deformation of the watertight characteristic structure based on a scaled model test of a near-field underwater explosion of a ship structure. The process is reasonable, and a numerical sub-model including the watertight characteristic structure and the deck and longitudinal wall on which it is located is established. The impact environment characteristics of the watertight doors and watertight hatch covers under actual working conditions are simulated by applying impact acceleration. Based on the scaled model test, the credibility and accuracy of the results can be guaranteed.

[0066] Embodiment 2: This embodiment further defines the method for calculating damage and deformation of a ship tightness characteristic structure described in Embodiment 1. In this embodiment, the relationship between the test model and the prototype in step 1, and the conversion relationship between the acceleration history curve and the prototype in step 6 are further defined, specifically including:

[0067] In step 1, the test model and the prototype satisfy the following relationship:

[0068]

[0069] Among them, L is the main scale of the model, t is the thickness of the cabin plate, r is the radius of the charge, d is the explosion distance, λ is the scale ratio, subscript p represents the prototype, and subscript m represents the test model;

[0070] In step 6, the acceleration history curve and the prototype satisfy the following conversion relationship:

[0071]

[0072] Where a is acceleration, t is action time, λ is scale ratio, subscript p represents prototype, and subscript m represents test model.

[0073] In this embodiment, by establishing a scaled model and conducting a scaled model test, it is possible to save manpower and material costs while ensuring the accuracy of the test results.

[0074] Implementation method 3: This implementation method further limits the method for calculating damage and deformation of a ship's tightness characteristic structure described in implementation method 1. In this implementation method, step 2 is further limited, specifically including:

[0075] Step 2 also includes: based on the position and model of the watertight door and the watertight hatch cover, the watertight characteristic structure is equivalent to a plate of a certain thickness through mass equivalence, and the coamings on both sides of the watertight characteristic structure are also mass equivalent, and the ratio of the mass after equivalence to the mass before equivalence is λ 3 .

[0076] In this embodiment, the watertight characteristic structure cover plate and the coaming plate are subjected to mass equivalence, and the ratio of the mass after equivalence to the mass before equivalence is λ 3 The thickness of the equivalent rear plate is determined based on the mass and size of the original watertight characteristic structure.

[0077] The benefit of making the watertight characteristic structure and the coamings on both sides of the watertight characteristic structure equivalent in mass is to simplify the actually complex watertight characteristic structure, facilitate the construction of the watertight door and watertight hatch cover structure in the test model, and also do not affect the measurement of the test impact acceleration input load.

[0078] Embodiment 4: This embodiment further limits the method for calculating the damage and deformation of a ship's tightness characteristic structure described in Embodiment 3. In this embodiment, the arrangement of the acceleration sensor in step 3 is further limited, specifically including:

[0079] The acceleration sensor of the watertight door is arranged at the junction of the equivalent surrounding wall and the longitudinal wall of the watertight door;

[0080] The acceleration sensor of the watertight hatch cover is arranged at the junction of the hatch cover equivalent wall and the deck.

[0081] The advantage of arranging the sensors at the two junctions in this embodiment is that the impact load input of the watertight door and the watertight hatch cover can be accurately obtained.

[0082] Embodiment 5: This embodiment further defines the method for calculating damage deformation of a ship tightness characteristic structure described in Embodiment 4. In this embodiment, step 4, the connection method of the watertight door, hatch cover, deck, and bulkhead in the scaled test model is further defined, specifically including:

[0083] The watertight door equivalent blind plate 2 is connected to the longitudinal wall 1 through the middle equivalent enclosure 3, and the hatch cover equivalent blind plate 5 is connected to the deck 4 through the middle equivalent enclosure 6; the connection methods between the equivalent blind plate 2, the equivalent enclosure 3 and the longitudinal wall 1 of the watertight door are all welding; the connection methods between the equivalent blind plate 5, the equivalent enclosure 6 and the deck 4 of the watertight hatch cover are all welding.

[0084] In this embodiment, the advantage of welding the watertight doors, hatch covers, decks and longitudinal walls in the test model together through the intermediate equivalent enclosure is that the impact load input of the watertight doors and hatch covers can be accurately obtained.

[0085] Embodiment 6: This embodiment further limits the calculation method for damage deformation of a ship tightness characteristic structure described in embodiment 1. In this embodiment, the simplified numerical simulation sub-model for establishing a watertight door and a watertight hatch cover described in step 5 is further limited, specifically including:

[0086] The simplified numerical simulation sub-model of the watertight door and watertight hatch cover established in step 5 needs to be simplified according to the structural deformation resistance, including:

[0087] The spring clips, spring handles and spring brackets on the watertight doors are secondary load-bearing structures in structural deformation and are equivalent to the watertight door panels by the method of mass equivalence;

[0088] The handles, gas struts, stoppers and grounding devices on the watertight hatch covers are secondary load-bearing structures in structural deformation and are equivalent to the watertight hatch cover door panels by the method of mass equivalence;

[0089] The hinges and wing clips on the watertight doors, as well as the hinges and butterfly clips on the watertight hatch covers, are the main load-bearing structures in structural deformation, so their basic shape features are retained and three-dimensional solid modeling is performed;

[0090] For the watertight door linkage clip, it is the main load-bearing structure in structural deformation, while the clip linkage mechanism is a secondary load-bearing structure, which is equivalent to the watertight door panel in a mass equivalent manner;

[0091] For the rubber gasket, modeling is performed according to its structural form, taking into account the bonding relationship between the rubber gasket and the cover plate, and the contact relationship between the rubber gasket and the enclosure.

[0092] In this embodiment, through this connection method, the relative position between the watertight door and the longitudinal wall in the original large ship can be well simulated.

[0093] Embodiment 7: This embodiment further defines the method for calculating damage deformation of a ship tightness characteristic structure described in Embodiment 1. In this embodiment, the bolts and nuts in step 5 are further defined, specifically including:

[0094] In step 5, the engagement state of the bolt and nut is ignored, and an integrated modeling technology is used to consider the forces between the bolt and the pressure plate, and between the bolt and the bottom pin by adding contact pairs.

[0095] In this embodiment, this connection method can well simulate the relative position between the watertight hatch cover and the deck in the original large ship. The forces between the bolt and the pressure plate, and between the bolt and the bottom pin can be calculated by the penalty force contact algorithm.

[0096] Embodiment 8: This embodiment further limits the calculation method for damage deformation of a ship tightness characteristic structure described in Embodiment 1. In this embodiment, the initial state of the watertight door and hatch cover is further limited, specifically including:

[0097] In step 5, a bolt preload is applied to the clips around the cover plate, and the preload is transferred to the rubber gasket through the pressure plate and the cover plate. After the rubber gasket is squeezed, the sub-model achieves a watertight effect.

[0098] The watertightness of the structure must be ensured during the welding process in this embodiment.

[0099] Embodiment 9: This embodiment further limits the method for calculating the damage and deformation of a ship's tightness characteristic structure described in Embodiment 1. In this embodiment, the verification method of the sub-model is further limited, specifically including:

[0100] Step 5, check the internal and external pressures of the sub-model according to the sub-model tightness design value, including: applying a constant pressure load to the sub-model cover, the pressure amplitude adopts the pressure design value corresponding to the structure, and the bottom node of the enclosure adopts a rigid constraint; if the calculation results show no leakage and permanent deformation, it proves that the structural modeling is accurate and the sub-model is established.

[0101] In this embodiment, based on the relationship between the acceleration of the scaled model and the prototype obtained by similarity theory, the acceleration information measured in the test can be converted to obtain the acceleration information of the prototype watertight door and the watertight hatch cover.

[0102] Embodiment 10: This embodiment further limits the calculation method for damage and deformation of a ship tightness characteristic structure described in Embodiment 1. In this embodiment, the basis for judging the damage of the watertight characteristic structure described in step 7 is further limited, specifically including:

[0103] The judgment basis of the watertight characteristic structure damage in step 7 is based on the relative position of the rubber gasket and the coaming, including:

[0104] If during the deformation of the tightness structure, the rubber gasket and the bottom enclosure are separated transiently, but the final relative position is close, it is judged that the structure is leaking;

[0105] If there is partial separation between the final relative position of the rubber gasket and the bottom enclosure, the structure is judged to be leakproof.

[0106] In this embodiment, during the modeling process of the watertight characteristic structure sub-model, due to its complex structure and large number of parts, its structure is simplified to a certain extent in order to facilitate the subsequent meshing and simulation calculation of the sub-model.

[0107] Embodiment eleven, this embodiment is based on an example of a method for calculating damage and deformation of a ship's tightness characteristic structure as described above. Figure 1 As shown, specifically including:

[0108] Based on the actual assessment conditions, the underwater explosion reduction model test is designed. According to the underwater explosion reduction similarity relationship, the actual thickness, size, charge radius, explosion distance and other information of the test model are obtained to determine the test conditions. The model and prototype should meet the following relationship: Where: L is the main scale of the model, t is the thickness of the cabin plate, r is the radius of the charge, d is the explosion distance, λ is the scale ratio, subscript p represents the prototype, and subscript m represents the model.

[0109] For the actual arrangement of watertight characteristic structures of large ships, the positions and models of watertight doors and watertight hatch covers can be determined, thereby determining the size and specifications of the watertight characteristic structures that need to be verified (i.e., watertight doors and watertight hatch covers on actual ships);

[0110] Furthermore, based on the position and model of the watertight door and watertight hatch cover, the watertight characteristic structure cover and its auxiliary structure are equivalent to a plate with equivalent thickness through mass equivalence during the model test. At the same time, the coamings on both sides of the watertight characteristic structure are also equivalent in mass. The ratio of the mass after equivalence to the mass before equivalence is λ 3 , the actual layout position refers to the original model,

[0111] Furthermore, an acceleration sensor is arranged below the enclosure of the tightness characteristic structure;

[0112] Furthermore, an underwater explosion scaled model test was carried out, and the impact acceleration of the scaled model watertight door and watertight hatch cover coaming position was obtained by the acceleration sensor. The input impact acceleration of the full-scale watertight door and watertight hatch cover was converted by the underwater explosion structural response similarity theory; the acceleration of the test model and the prototype satisfied the following relationship:

[0113] Furthermore, a sub-model is established according to the actual structural form and size of the watertight door and watertight hatch cover. In the modeling process, structural features such as door frames, door panels, reinforcement ribs, hinges, linkage clips, wing clips, spring handles, rubber gaskets, etc. are considered; the minimum cell surrounded by reinforcement ribs around the sub-model is established as an artificial boundary;

[0114] Furthermore, the acceleration information measured by the scaled test is converted by similarity relationship and loaded onto the artificial boundary of the sub-model deck. The deformation response of the watertight door and watertight hatch cover model under the action of local impact load is carried out by nonlinear finite element numerical simulation software. The main process of numerical simulation is as follows:

[0115] In the process of modeling the watertight characteristic structure sub-model, due to its complex structure and many parts, in order to facilitate the subsequent meshing and simulation calculation of the sub-model, its structure is simplified to a certain extent. For components such as spring handles that have little effect on the strength of the watertight characteristic structure, their structural form is not considered, and they are equivalent to the door panel in a mass equivalent manner; for components such as hinges and wing-shaped clips, the main structural features are retained and simplified for modeling; for linkage clips, only the clips that support the internal walls when the watertight characteristic structure is in a closed state are considered, and their external linkage devices are not considered, and they are still equivalent to the door panel in a mass equivalent manner; for rubber gaskets, they mainly play a sealing role and are vulnerable components, so they need to be modeled, and the initial sealing of the model is controlled by the bolt preload.

[0116] When conducting numerical simulation, it is first necessary to apply a certain preload to the watertight characteristic structure to simulate the closed state of the actual ship's watertight characteristic structure. The preload size is taken as 0.6 times the yield strength of the bolt material according to the "Mechanical Design Manual" (5th edition); the minimum unit cell surrounded by the reinforcement ribs around the sub-model is taken as the artificial boundary of the structure; finally, the measurement point information with the largest acceleration among the measurement points at the bottom of the equivalent sub-model in the test is selected as the benchmark. After similar conversion, the impact acceleration information is applied to the surrounding connection positions of the watertight characteristic structure and the longitudinal wall, and the deformation response of the hull watertight door and watertight hatch cover under the impact load of the near-field underwater explosion can be obtained.

[0117] The impact resistance assessment process of watertight characteristic structures is shown in 1. According to the actual arrangement of watertight doors, the positions and models of watertight doors and watertight hatch covers on large ships are determined, so as to determine the structural form and size of the watertight doors that need to be verified; according to the obtained structural form and size of the watertight doors and watertight hatch covers, their structures are simplified, and the watertight doors, watertight hatch covers and main components are equivalent to a plate with equivalent thickness on the hull structure through mass equivalence. At the same time, the two side panels and attached structures of the watertight doors and watertight hatch covers are also mass equivalent. The size and thickness of the door panels and coamings of the equivalent post-tightness characteristic components (watertight doors and watertight hatch covers) are obtained; then, the impact acceleration measuring points are arranged under the coamings of the tightness structure, and the impact acceleration at the measuring point positions is obtained by conducting underwater explosion tests; a sub-model of the tightness characteristic structure is established, and the impact acceleration obtained from the test measurement is loaded onto the sub-model after similarity conversion, and the deformation response of the watertight door or watertight hatch cover is obtained through numerical simulation calculation, and the structural deformation result is compared with the tightness damage criterion of the watertight door and watertight hatch cover to determine whether the structural tightness is damaged. Figure 2 The overall schematic diagram of the equivalent structure of the test model watertight door of the present application is given in the figure, wherein the watertight door equivalent blind plate 2 is obtained after the mass equivalence of the main part of the watertight door, and the watertight door equivalent surrounding wall 3 is obtained after the mass equivalence of the surrounding plates and attached components on both sides of the watertight door. The watertight door equivalent blind plate 2 is connected to the longitudinal wall 1 through the intermediate equivalent surrounding wall 3, which can well simulate the relative position between the watertight door and the longitudinal wall in the original large ship. P is the equivalent structure of the watertight door of the test model.

[0118] Figure 3 The overall schematic diagram of the equivalent structure of the test model watertight hatch cover of the present application is given in the figure, wherein the equivalent blind plate 5 of the watertight hatch cover is obtained after the mass equivalence of the main part of the watertight hatch cover, and the equivalent surrounding wall 6 of the watertight hatch cover is obtained after the mass equivalence of the surrounding plates and attached components on both sides of the watertight hatch cover. The hatch cover equivalent blind plate 5 is connected to the deck 4 through the intermediate equivalent surrounding wall 6, which can well simulate the relative position between the watertight hatch cover and the deck in the original large ship. Q is the equivalent structure of the watertight hatch cover of the test model.

[0119] The equivalent blind plates of watertight doors and watertight hatch covers, the equivalent enclosures and their connections with longitudinal walls and decks are all welded, and the watertight performance of the structure must be ensured during the welding process.

[0120] Determine the positions of the watertight doors and hatch covers of large ships for scaled model test according to the actual arrangement of the watertight doors and hatch covers. Arrange the watertight door panels and surrounding walls, watertight hatch cover panels and surrounding walls after mass equivalence in the form of blind plates on the test model according to the test scale ratio, and arrange acceleration measurement points at the junction of the equivalent surrounding walls, longitudinal walls and decks;

[0121] Figure 4 A schematic diagram of the arrangement positions of the watertight door acceleration measurement points in the model test of the present application is given, wherein the watertight door acceleration measurement points are mainly arranged at the junction of the watertight door equivalent surrounding wall 3 and the longitudinal wall 1; the watertight hatch cover acceleration measurement points are mainly arranged at the junction of the hatch cover equivalent surrounding wall 6 and the deck 4.

[0122] Figure 5 The overall structural schematic diagram of the structural sub-model of the watertight characteristic components (watertight doors, watertight hatch covers) of the present application is given, which takes into account components related to watertight performance such as bolts, clips, rubber, etc.

[0123] Figure 6 The schematic diagram of the structural response of the structural sub-model of the watertight characteristic components (watertight doors and watertight hatch covers) of this application after numerical calculation is given in the figure. The external clip of the watertight door breaks under the impact load, so it is determined to be a tightness failure; the bolt root of the watertight hatch cover structure is significantly twisted under the impact load, and the watertight cover plate is lifted, so it is also determined to be a tightness failure.

[0124] According to the watertight door models actually arranged on large ships, a sub-model of watertight doors and watertight hatch covers is established. The acceleration measured by the scaled model test is converted and loaded onto the established sub-model through similarity relationship. The deformation response of the watertight door and watertight hatch cover model is obtained by numerical calculation. By comparing the deformation result with the damage judgment basis of the watertight door tightness characteristics, it can be calculated whether the watertight doors and watertight hatch covers of large ships are damaged under the action of explosion impact load.

[0125] The present application proposes a method for equivalent verification of watertight doors and watertight hatch covers based on scaled model tests. The process is reasonable and fully considers the deformation response characteristics of the watertight door structure under the complex environment of underwater explosions. At the same time, based on the scaled model test, the correctness and accuracy of the calculation results are guaranteed. This method can enrich the calculation means for evaluating the scope of water ingress of ships and effectively improve the accuracy of ship vitality assessment.

[0126] The present application proposes a damage deformation method for watertight doors and watertight hatch covers based on a scaled model test, which is used to provide a technical means for studying the scope of tightness damage.

[0127] The above are all specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope described in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for calculating damage and deformation of ship tightness characteristic structure, characterized in that: The method comprises: Step 1: Design an underwater explosion scale model test, obtain the actual thickness, size, charge radius, and explosion distance of the test model according to the underwater explosion scale similarity relationship, and determine the test conditions; Step 2: Determine the size and specifications of the watertight characteristic structures to be verified according to the locations and models of the watertight characteristic structures of the large ship, wherein the watertight characteristic structures include watertight doors and watertight hatch covers; Step 3, arranging an acceleration sensor below the equivalent coaming of the watertight characteristic structure; Step 4: Conduct an underwater explosion scaled model test, and obtain the test impact acceleration time history curve at the watertight door coaming and watertight hatch cover coaming positions of the scaled model through an acceleration sensor; Step 5: Establish a simplified numerical simulation sub-model of the watertight door and watertight hatch cover, including: Determine the structural features and classify them as equivalent according to their ability to resist deformation, the structural features include coamings, door panels, cover panels, stiffeners, hinges, linkage clips, wing clips, butterfly clips and rubber gaskets, among which the wing clips in the watertight doors and the butterfly clips in the watertight hatch covers are mainly composed of bolts, nuts, pressure plates and bottom pins; An artificial boundary of a sub-model is established, wherein the structural boundary of the sub-model is selected as the smallest unit cell surrounded by the longitudinal wall and the reinforcement ribs near the watertight characteristic structure on the deck; The strength of the internal and external pressures of the structure are checked according to the sub-model tightness design values; Step 6: convert the impact acceleration measured by the scaled model test in step 4 according to the underwater explosion scaled similarity relationship to obtain the impact acceleration time history curve at the real scale, load the converted impact acceleration onto the bottom boundary of the sub-model coaming, calculate the deformation response of the watertight door and watertight hatch cover model under the action of the local impact load through nonlinear finite element numerical simulation software, and obtain the deformation result; Step 7: judging whether the watertight doors and watertight hatch covers of large ships are damaged in tightness under the impact load of explosion according to the comparison between the deformation result and the watertight characteristic structure damage judgment basis; The simplified numerical simulation sub-model of the watertight door and watertight hatch cover established in step 5 needs to be simplified according to the structural deformation resistance, including: The spring clips, spring handles and spring brackets on the watertight doors are secondary load-bearing structures in structural deformation and are equivalent to the watertight door panels by the method of mass equivalence; The handles, gas struts, stoppers and grounding devices on the watertight hatch covers are secondary load-bearing structures in structural deformation and are equivalent to the watertight hatch cover door panels by the method of mass equivalence; The hinges and wing clips on the watertight doors, as well as the hinges and butterfly clips on the watertight hatch covers, are the main load-bearing structures in structural deformation, so their basic shape features are retained and three-dimensional solid modeling is performed; For the watertight door linkage clip, it is the main load-bearing structure in structural deformation, while the clip linkage mechanism is a secondary load-bearing structure, which is equivalent to the watertight door panel in a mass equivalent manner; For the rubber gasket, modeling is performed according to its structural form, taking into account the bonding relationship between the rubber gasket and the cover plate, and the contact relationship between the rubber gasket and the enclosure.

2. A method for calculating damage deformation of ship tightness characteristic structure according to claim 1, characterized in that: In step 1, the test model and the prototype satisfy the following relationship: in, is the main scale of the model, is the compartment plate thickness, is the radius of the drug package, For the explosion distance, is the scale ratio, subscript p Represents the prototype, subscript m Representative experimental model; In step 6, the acceleration history curve and the prototype satisfy the following conversion relationship: ， in, is the acceleration, is the action time, is the scale ratio, subscript p Represents the prototype, subscript m Represents the experimental model.

3. A method for calculating damage deformation of ship tightness characteristic structure according to claim 1, characterized in that: Step 2 also includes: based on the position and model of the watertight door and the watertight hatch cover, the watertight characteristic structure cover and the coaming are mass equivalent, and the ratio of the mass after the equivalent to the mass before the equivalent is .

4. A method for calculating damage deformation of ship tightness characteristic structure according to claim 3, characterized in that: The acceleration sensor of the watertight door is arranged at the junction of the equivalent surrounding wall and the longitudinal wall of the watertight door; The acceleration sensor of the watertight hatch cover is arranged at the junction of the hatch cover equivalent wall and the deck.

5. A method for calculating damage deformation of ship tightness characteristic structure according to claim 4, characterized in that: The equivalent blind plate of the watertight door is connected to the longitudinal wall through the equivalent enclosure in the middle, and the equivalent blind plate of the hatch cover is connected to the deck through the equivalent enclosure in the middle; the connection method between the equivalent blind plate, equivalent enclosure and longitudinal wall of the watertight door is welding; the connection method between the equivalent blind plate, equivalent enclosure and deck of the watertight hatch cover is welding.

6. A method for calculating damage deformation of ship tightness characteristic structure according to claim 1, characterized in that: In step 5, the engagement state of the bolt and nut is ignored, and an integrated modeling technology is used. The forces between the bolt and the pressure plate, and between the bolt and the bottom pin are calculated through a penalty force contact algorithm.

7. A method for calculating damage and deformation of ship tightness characteristic structure according to claim 1, characterized in that: In step 5, a bolt preload is applied to the clips around the cover plate, and the preload is transferred to the rubber gasket through the pressure plate and the cover plate. After the rubber gasket is squeezed, the sub-model achieves a watertight effect.

8. A method for calculating damage and deformation of ship tightness characteristic structure according to claim 1, characterized in that: Step 5, check the internal and external pressures of the sub-model according to the sub-model tightness design value, including: applying a constant pressure load to the sub-model cover, the pressure amplitude adopts the pressure design value corresponding to the structure, and the bottom node of the enclosure adopts a rigid constraint; if the calculation results show no leakage and permanent deformation, it proves that the structural modeling is accurate and the sub-model is established.

9. A method for calculating damage deformation of ship tightness characteristic structure according to claim 1, characterized in that: The watertight characteristic structural damage described in step 7 is judged based on the relative position of the rubber gasket and the coaming, including: If during the deformation of the tightness structure, the rubber gasket and the bottom enclosure are separated transiently, but the final relative position is close, it is judged that the structure is leaking; If there is partial separation between the final relative position of the rubber gasket and the bottom enclosure, the structure is judged to be leakproof.

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