Method and system for judging the failure mechanism of deep-sea metal pressure hull implosion based on modal displacement

Abstract

The present invention provides a method and system for judging the implosion failure mechanism of a deep-sea metal pressure hull based on modal displacement, comprising: modeling a finite element model of the deep-sea metal pressure hull and numbering the nodes of the finite element model; performing eigenvalue buckling analysis on the finite element model to obtain the first N-order modal displacement results; obtaining the initial geometric defects of a local single modal defect method or a combined modal defect method based on the modal displacement results of each order; scaling the initial geometric defects according to the geometric out-of-roundness requirements of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure-resistant structure; modeling a finite element model of the results of different final geometric defect displacements to obtain a final structural finite element model, and judging the implosion failure form of the deep-sea metal pressure hull by using the obtained final structural finite element model; performing implosion fluid-solid coupling calculation verification on the metal pressure hull in the deep-sea environment, and judging the implosion failure form of the deep-sea metal pressure hull by using the final structural finite element model.

Description

Technical Field

[0001] The present invention relates to the field of deep-sea metal pressure-resistant structure modeling and evaluation, and in particular to a method and system for determining the implosion failure mechanism of a deep-sea metal pressure-resistant hull based on modal displacement. Background Art

[0002] The deep-sea metal pressure hull is an important component of underwater vehicles and manned submersibles. It needs to withstand the external hydrostatic pressure in different water depths and provide an operating environment for the internal non-pressure-resistant components. At present, the judgment of the underwater implosion mechanism of the metal pressure hull is usually directly calculated by the fluid-solid coupling method. This method is based on the interaction between the fluid and structure on the surface of the pressure hull. In the calculation process, the implosion failure mechanism is judged through the transmission of force and displacement.

[0003] However, in actual engineering, it is found that due to the complex structure of deep-sea metal pressure hulls, there are initial geometric and material defects of varying sizes in the design and manufacturing. Therefore, when directly using the fluid-structure coupling algorithm for numerical calculation, on the one hand, powerful computing power is required, which will cause a large computing cost. On the other hand, the structural defects cannot be fully considered, resulting in errors in the numerical simulation results.

[0004] The present invention uses the finite element method to perform modal calculations on deep-sea metal pressure-resistant structures and takes into account the geometric non-circularity requirements of the structure. It can scientifically determine the failure mechanism of deep-sea metal pressure-resistant structures and has important engineering application value for the design and manufacture of deep-sea equipment such as underwater vehicles and manned submersibles. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a method and system for determining the failure mechanism of deep-sea metal pressure hull implosion based on modal displacement.

[0006] A method for determining the failure mechanism of a deep-sea metal pressure hull implosion based on modal displacement according to the present invention comprises:

[0007] Step S1: Modeling a structural finite element model of the deep-sea metal pressure hull to obtain a finite element model, and numbering the nodes of the finite element model;

[0008] Step S2: using the finite element method to perform eigenvalue buckling analysis on the finite element model to obtain the first N-order modal displacement results;

[0009] Step S3: obtaining the initial geometric defect of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode;

[0010] Step S4: scaling the initial geometric defect according to the geometric non-circularity requirement of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure hull;

[0011] Step S5: Modeling a finite element model based on the results of different final geometric defect displacements to obtain a final structural finite element model, and using the obtained final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull;

[0012] Step S6: Perform fluid-solid coupling calculations on the implosion of the metal pressure hull in the deep-sea environment to verify the use of the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull.

[0013] Preferably, the step S3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the defect geometric defect of the combined modal defect method.

[0014] Preferably, the step S4 adopts: taking the geometric out-of-roundness requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain a final geometric defect displacement.

[0015] Preferably, the step S5 adopts: adding the node number m corresponding to the final node defect displacement to the node number n of the structural finite element model i The final structural finite element model is obtained;

[0016] Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are:

[0017] n n，i(x，y) =n i +m i

[0018] Where n n，i(x，y) It represents the position of the unit node number i after the displacement is superimposed based on the first N modes.

[0019] Preferably, the step S6 adopts: using a fluid-structure coupling algorithm to perform implosion fluid-structure coupling calculation on the metal pressure hull in the deep sea environment.

[0020] A deep-sea metal pressure hull implosion failure mechanism judgment system based on modal displacement provided by the present invention comprises:

[0021] Module M1: Model the structural finite element model of the deep-sea metal pressure hull, obtain the finite element model, and number the nodes of the finite element model;

[0022] Module M2: Use the finite element method to perform eigenvalue buckling analysis on the finite element model and obtain the first N-order modal displacement results;

[0023] Module M3: Obtain the initial geometric defects of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode;

[0024] Module M4: Scaling the initial geometric defects according to the geometric non-circularity requirements of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure-resistant structure;

[0025] Module M5: Model the finite element model based on the results of different final geometric defect displacements to obtain the final structural finite element model, and use the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull;

[0026] Module M6: Perform fluid-solid coupling calculations on the implosion of metal pressure hulls in deep-sea environments to verify the use of the final structural finite element model to determine the failure mode of the deep-sea metal pressure hull implosion.

[0027] Preferably, the module M3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the defect geometric defect of the combined modal defect method.

[0028] Preferably, the module M4 adopts: taking the geometric out-of-roundness requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain a final geometric defect displacement.

[0029] Preferably, the module M5 adopts: the node number m corresponding to the final node defect displacement i Add to the structural finite element model node number n i The final structural finite element model is obtained;

[0030] Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are:

[0031] n n，i(x，y) =n i +m i

[0032] Where n n，i(x，y) It represents the position of the unit node number i after the displacement is superimposed based on the first N modes.

[0033] Preferably, the module M6 adopts: using a fluid-solid coupling algorithm to perform implosion fluid-solid coupling calculation on the metal pressure hull in the deep sea environment.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The present invention takes into account the initial defects of the deep-sea metal pressure hull based on the single defect mode method and the overall defect mode method, and can meet the design and construction requirements of underwater submersibles.

[0036] 2. The present invention scales the single modal displacement and the overall modal displacement results based on the out-of-roundness coefficient of the radius, thereby realizing a rapid judgment of the failure form of the deep-sea metal pressure hull implosion.

[0037] 3. The present invention realizes the inverse control of the correlation between underwater implosion and modal displacement by calculating the evolution characteristics of the deep-sea metal pressure hull after implosion failure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0039] Figure 1 The present invention is a flow chart of a method for determining the failure mechanism of deep-sea metal pressure hull implosion based on modal displacement.

[0040] Figure 2 It is a schematic diagram of the finite element model of the deep-sea titanium alloy ring-ribbed cylindrical shell structure.

[0041] Figure 3 It is a schematic diagram of the first 6 modal displacement results of deep-sea titanium alloy ring-ribbed cylindrical shell.

[0042] Figure 4 It is a schematic diagram of the finite element model of the deep-sea titanium alloy ring-ribbed cylindrical shell after the single 1st-order mode and the first 6-order modes are superimposed.

[0043] Figure 5 It is a schematic diagram of the ultimate strength of deep-sea titanium alloy ring-ribbed cylindrical shell.

[0044] Figure 6 Schematic diagram of two types of implosion failure mechanisms of deep-sea titanium alloy ring-ribbed cylindrical shells based on modal displacement. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0046] Aiming at the problem of judging the failure mechanism of the deep-sea metal pressure hull implosion in the deep sea, the purpose of the present invention is to provide a method and system for judging the failure mechanism of the deep-sea metal pressure hull implosion based on modal displacement, which can accurately judge the implosion failure form of the deep-sea metal pressure hull and provide a basis for subsequent evaluation of the structural ultimate strength, structural dynamic response, etc. based on the model, aiming to provide a theoretical basis and practical basis for the design and manufacture of deep-sea underwater vehicles and manned submersibles.

[0047] Example 1

[0048] A method for determining the failure mechanism of a deep-sea metal pressure hull implosion based on modal displacement according to the present invention comprises:

[0049] Step S1: Modeling a structural finite element model of the deep-sea metal pressure hull to obtain a finite element model, and numbering the nodes of the finite element model;

[0050] Step S2: using the finite element method to perform eigenvalue buckling analysis on the finite element model to obtain the first N-order modal displacement results;

[0051] Step S3: obtaining the initial geometric defect of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode;

[0052] Step S4: scaling the initial geometric defect according to the geometric non-circularity requirement of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure hull;

[0053] Step S5: Modeling a finite element model based on the results of different final geometric defect displacements to obtain a final structural finite element model, and using the obtained final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull;

[0054] Step S6: Perform fluid-solid coupling calculations on the implosion of the metal pressure hull in the deep-sea environment to verify the use of the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull.

[0055] Specifically, the step S3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the defect geometric defect of the combined modal defect method.

[0056] Specifically, the step S4 adopts: taking the geometric non-circularity requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain the final geometric defect displacement.

[0057] Specifically, the step S5 adopts: the node number m corresponding to the final node defect displacement is i Add to the structural finite element model node number n i The final structural finite element model is obtained;

[0058] Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are:

[0059] n n，i(x，y) =n i +m i

[0060] Where n n，i(x，y)It represents the position of the unit node number i after the displacement is superimposed based on the first N modes.

[0061] Specifically, the step S6 adopts: using a fluid-solid coupling algorithm to perform implosion fluid-solid coupling calculation on the metal pressure hull in the deep sea environment.

[0062] A deep-sea metal pressure hull implosion failure mechanism judgment system based on modal displacement provided by the present invention comprises:

[0063] Module M1: Model the structural finite element model of the deep-sea metal pressure hull, obtain the finite element model, and number the nodes of the finite element model;

[0064] Module M2: Use the finite element method to perform eigenvalue buckling analysis on the finite element model and obtain the first N-order modal displacement results;

[0065] Module M3: Obtain the initial geometric defects of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode;

[0066] Module M4: Scaling the initial geometric defects according to the geometric non-circularity requirements of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure-resistant structure;

[0067] Module M5: Model the finite element model based on the results of different final geometric defect displacements to obtain the final structural finite element model, and use the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull;

[0068] Module M6: Perform fluid-solid coupling calculations on the implosion of metal pressure hulls in deep-sea environments to verify the use of the final structural finite element model to determine the failure mode of the deep-sea metal pressure hull implosion.

[0069] Specifically, the module M3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the defect geometric defect of the combined modal defect method.

[0070] Specifically, the module M4 adopts: taking the geometric non-circularity requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain the final geometric defect displacement.

[0071] Specifically, the module M5 adopts: the node number m corresponding to the final node defect displacement i Add to the structural finite element model node number n i The final structural finite element model is obtained;

[0072] Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are:

[0073] n n，i(x，y) =n i +m i

[0074] Where n n，i(x，y) It represents the position of the unit node number i after the displacement is superimposed based on the first N modes.

[0075] Specifically, the module M6 adopts: using a fluid-solid coupling algorithm to perform implosion fluid-solid coupling calculations on a metal pressure hull in a deep-sea environment.

[0076] Example 2

[0077] Embodiment 2 is a preferred embodiment of Embodiment 1

[0078] According to a method for determining the failure mechanism of deep-sea metal pressure hull implosion based on modal displacement provided by the present invention, Figure 1 As shown, including:

[0079] Step 1: Build a finite element model of the deep-sea metal pressure hull;

[0080] The structural finite element modeling of deep-sea metal pressure hull is carried out. Since the application object is usually a spherical or cylindrical thin shell structure, shell elements are usually used. The finite element model of the cylindrical titanium alloy pressure hull is as follows: Figure 2 As shown. Let the node number of the finite element model be n i .

[0081] Step 2: Perform eigenvalue buckling analysis on the finite element model to obtain the first N modal displacement results of the structure;

[0082] The finite element method is used to perform eigenvalue buckling analysis on the finite element model, and the displacement results of the first 6 modal modes are obtained, such as Figure 3 As shown. And record the total node numbers corresponding to the modal displacement results respectively as m 1，i 、m 2，i 、m 3，i 、m 4，i 、m 5，i 、m 6，i The subscripts 1 to 6 represent the corresponding modal orders, and the subscript i represents the node number of the finite element model.

[0083] Step 3: Partially or completely superimpose the displacement results of each order mode to obtain the initial geometric defects of the local single mode defect method and the overall combined mode defect method;

[0084] The single mode defect displacement result takes a certain order in the eigenvalue buckling analysis as the initial defect of the structure, while the defect displacement result of the multi-mode superposition combination introduces multiple eigenvalue buckling modal results in one model at the same time, thus forming a finite element structural model with multi-order modal displacement defect forms. Using the python self-compiler, the modal result m of the cylindrical pressure shell corresponding to the finite element node number is converted into 1，i ~m 6，i Perform superposition to obtain the initial geometric imperfection based on the modal displacement results:

[0085] m n，i =m 1，i +m 2，i +...+m N-1，i +m N，i

[0086] In the formula, m n，i It represents the sum of the modal displacements of all nodes of the first N modes.

[0087] Step 4: Scaling the initial geometric defect according to the geometric non-circularity requirements of the pressure hull, and the numerical results are used as the final geometric defect displacement of the deep-sea pressure structure;

[0088] For deep-sea metal pressure hulls, the influence of manufacturing errors needs to be considered. For cylindrical ring-ribbed cylindrical shells, 0.5% is taken as the initial out-of-roundness. The python self-compiled program is used to take the out-of-roundness requirement as the scaling factor to scale the initial geometric defect displacement obtained based on the modal superposition method to obtain the final geometric defect displacement of the deep-sea titanium alloy pressure hull. Let the node number corresponding to the final defect displacement be m i .

[0089] m i =0.5%×m n，i

[0090] In the formula, m i Indicates the unit node number after considering the initial out-of-roundness based on the superposition displacement of the first N modes.

[0091] Step 5: According to the order of calculation, the finite element model is modeled for the results of different final geometric defect displacements to obtain the final finite element model, and the final finite element model is used to determine the implosion failure form of the deep-sea metal pressure hull;

[0092] The Python self-compiled program is used to realize the node number m corresponding to the final node defect displacement of the deep-sea ring-stiffened cylindrical shell i Add them to the structural finite element model node number n one by one i The final ring-stiffened cylindrical shell implosion calculation structure model is obtained. The node position of the deep-sea metal pressure shell based on modal displacement is:

[0093] n n，i(x，y) =n i +m i

[0094] Where n n，i(x，y) It represents the position of the unit node number i after the displacement is superimposed based on the first N modes.

[0095] According to the displacement results of each modal superposition, the structural finite element model considering the initial defects is obtained, as shown in Figure 4 As shown. When the finite element structural model is obtained by taking the first-order buckling mode result as the initial defect of the ring-stiffened cylindrical shell, the ring-stiffened cylindrical shell only has a slight depression at the center surface position, while other positions remain basically unchanged. Therefore, it is predicted that when a deep-sea ring-stiffened cylindrical shell implodes, it will first begin to dent inward at the center position and fail preferentially at the center position. With the evolution of the implosion, the collapse at the center position gradually expands to both ends, eventually leading to the failure of the entire structure. However, it can be foreseen that for the ring-stiffened cylindrical shell that takes the first-order buckling mode displacement as the initial defect, the structure can still remain relatively intact in the final stage.

[0096] When the modal number of the initial geometric defect is 6, the strength near the buckling limit increases, and the surface of the structure shows multi-modal defect displacement characteristics, and a slight depression appears on the surface. Therefore, it can be predicted that in the implosion failure mechanism of the superposition of the first 6 modal displacements, the ring-stiffened cylindrical shell structure will show multi-modal depression characteristics on the surface, and as the implosion progresses, the middle section of the cylindrical shell fails and breaks at almost the same time, and a relatively complete structure is not retained.

[0097] In addition, based on the finite element model considering the structural and geometric initial defects, the arc length method is used to calculate the ultimate load of the model. Figure 5 This proves that the results obtained by using the single modal defect method and the overall modal defect method are different, and verifies the correctness of the modal superposition.

[0098] Step 6: Perform fluid-structure coupling calculations on the metal pressure hull implosion in the deep sea environment to verify the results of the deep sea metal pressure hull implosion structural deformation based on modal displacement

[0099] The fluid-solid coupling algorithm is used to perform numerical simulation of the implosion failure mechanism of the final finite element model in step 5 to verify the correctness of the judgment method of the ring-stiffened cylindrical shell based on the modal displacement results. The implosion failure process based on the displacement of a single mode and the first six superimposed modes is shown in Figure 2. Figure 6 shown.

[0100] As for the result of introducing the first-order buckling mode result as the initial defect into the structural finite element model, the deep-sea ring-stiffened cylindrical shell begins to sink inward at the center position and fails first at the center position. With the evolution of the implosion, the collapse of the center position gradually extends to both ends, eventually leading to the failure of the entire structure. In the implosion failure mechanism of the superposition of the first 6 modal displacements, the ring-stiffened cylindrical shell structure presents multi-modal deformation characteristics at the surface position, and with the development of the implosion, the middle section of the cylindrical shell basically completely fails and breaks. It can be seen that the underwater implosion failure mechanism of the ring-stiffened cylindrical shell is consistent with the single and superposition results based on modal displacement. Therefore, the present invention can quickly obtain the implosion failure mechanism of the deep-sea metal pressure hull based on modal displacement, which has important engineering significance for the design and manufacture of the pressure hull of deep-sea submersibles.

[0101] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0102] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for determining the failure mechanism of deep-sea metal pressure hull implosion based on modal displacement, characterized in that: include: Step S1: Modeling a structural finite element model of the deep-sea metal pressure hull to obtain a finite element model, and numbering the nodes of the finite element model; Step S2: using the finite element method to perform eigenvalue buckling analysis on the finite element model to obtain the first N-order modal displacement results; Step S3: obtaining the initial geometric defect of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode; Step S4: scaling the initial geometric defect according to the geometric non-circularity requirement of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure hull; Step S5: Modeling a finite element model based on the results of different final geometric defect displacements to obtain a final structural finite element model, and using the obtained final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull; Step S6: performing fluid-solid coupling calculation for the implosion of the metal pressure hull in the deep-sea environment, and verifying the use of the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull; The step S2 comprises: using the finite element method to perform eigenvalue buckling analysis on the finite element model, obtaining the first 6 modal displacement results, and recording the total node numbers corresponding to the modal displacement results as m and m respectively. 1,i 、m 2,i 、m 3,i 、m 4,i 、m 5,i 、m 6,i ; Wherein the subscripts 1 to 6 represent the corresponding modal orders, and the subscript i represents the node number of the finite element model; The step S3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the initial geometric defect of the combined modal defect method; The single mode defect displacement result is to use a certain order in the eigenvalue buckling analysis as the initial defect of the structure; the multi-mode superposition combined defect displacement result is to introduce multiple eigenvalue buckling mode results into one model at the same time, thus forming a finite element structural model with multi-order modal displacement defect forms; The step S4 adopts: taking the geometric non-circularity requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain the final geometric defect displacement; The python self-compiled program is used to take the out-of-roundness requirement as the scaling factor to scale the initial geometric defect displacement obtained based on the modal superposition method to obtain the final geometric defect displacement of the deep-sea titanium alloy pressure hull. The step S5 adopts: the node number m corresponding to the final node defect displacement is i Add them to the structural finite element model node number n one by one i The final structural finite element model is obtained; Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are: n n,i(x,y) =n i +m i Where n n,i(x,y) Indicates the position corresponding to the unit node number i after the displacement is superimposed based on the first N modes; The step S6 adopts: using a fluid-solid coupling algorithm to perform an implosion fluid-solid coupling calculation on the metal pressure hull in the deep sea environment; The fluid-solid coupling algorithm is used to numerically simulate the implosion failure mechanism of the final finite element model to verify the correctness of the metal pressure hull judgment method based on the modal displacement results.

2. A deep-sea metal pressure hull implosion failure mechanism judgment system based on modal displacement, characterized in that: include: Module M1: Model the structural finite element model of the deep-sea metal pressure hull, obtain the finite element model, and number the nodes of the finite element model; Module M2: Use the finite element method to perform eigenvalue buckling analysis on the finite element model and obtain the first N-order modal displacement results; Module M3: Obtain the initial geometric defects of the local single mode defect method or the combined mode defect method based on the displacement results of each order mode; Module M4: Scaling the initial geometric defects according to the geometric non-circularity requirements of the pressure hull to obtain the final geometric defect displacement of the deep-sea pressure-resistant structure; Module M5: Model the finite element model based on the results of different final geometric defect displacements to obtain the final structural finite element model, and use the final structural finite element model to determine the implosion failure form of the deep-sea metal pressure hull; Module M6: Perform fluid-solid coupling calculations on the implosion of metal pressure hulls in deep-sea environments, and verify the use of the final structural finite element model to determine the failure form of the implosion of deep-sea metal pressure hulls; The module M2 includes: using the finite element method to perform eigenvalue buckling analysis on the finite element model, obtaining the first 6 modal displacement results, and recording the total node numbers corresponding to the modal displacement results as m 1,i 、m 2,i 、m 3,i 、m 4,i 、m 5,i 、m 6,i ; Wherein the subscripts 1 to 6 represent the corresponding modal orders, and the subscript i represents the node number of the finite element model; The module M3 adopts: obtaining a certain order modal result based on each order modal displacement result to obtain the initial geometric defect of the single modal defect method; or partially or completely superimposing each order modal displacement result to obtain the initial geometric defect of the combined modal defect method; The single mode defect displacement result is to use a certain order in the eigenvalue buckling analysis as the initial defect of the structure; the multi-mode superposition combined defect displacement result is to introduce multiple eigenvalue buckling mode results into one model at the same time, thus forming a finite element structural model with multi-order modal displacement defect forms; The module M4 adopts: taking the geometric non-circularity requirement of the pressure hull as a scaling factor, scaling the initial geometric defect displacement to obtain the final geometric defect displacement; The python self-compiled program is used to take the out-of-roundness requirement as the scaling factor to scale the initial geometric defect displacement obtained based on the modal superposition method to obtain the final geometric defect displacement of the deep-sea titanium alloy pressure hull. The module M5 adopts: the node number m corresponding to the final node defect displacement i Add them to the structural finite element model node number n one by one i The final structural finite element model is obtained; Among them, the node positions of the deep-sea metal pressure hull based on modal displacement are: n n,i(x,y) =n i +m i Where n n,i(x,y) Indicates the position corresponding to the unit node number i after the displacement is superimposed based on the first N modes; The module M6 adopts: using fluid-solid coupling algorithm to perform implosion fluid-solid coupling calculation on the metal pressure hull in the deep sea environment; The fluid-solid coupling algorithm is used to numerically simulate the implosion failure mechanism of the final finite element model to verify the correctness of the metal pressure hull judgment method based on the modal displacement results.

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