A modeling method for a sound vibration prediction model of a composite hull hat-shaped stiffened laminate plate

Abstract

The application discloses a kind of composite hull cap type stiffened laminate panel acoustic vibration prediction model modeling methods, comprising the following steps: obtaining and combing composite hull cap type stiffened laminate panel structure modeling parameter;Laminate panel part is modeled using conventional shell element;Equivalent shell element is used to model large cap profile part;Equivalent beam element is used to model small cap profile part;Cap stiffened laminate panel structure in the transverse and longitudinal cap profile intersection area ignores transition connection;Composite cap stiffened laminate panel structure structural loss factor parameter acquisition;Based on cap stiffened laminate panel equivalent parameter and wave theory, the model is meshed;Acoustic fluid domain grid is established, and acoustic infinite element far field boundary and fluid-structure coupling boundary are defined.The problem that the modeling of cap stiffened laminate panel, a complex composite structure in ship structure, is difficult to effectively solve is solved, the modeling cost is effectively reduced, and the calculation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of vibration reduction and noise reduction technology for composite material ships, specifically to a modeling method for acoustic vibration prediction of composite material ship hull cap-shaped stiffened laminated plates. Background Technology

[0002] Composite materials possess advantages such as light weight, high specific strength, high specific stiffness, good vibration damping and absorption performance, corrosion resistance, excellent electrochemical properties, and the ability to be integrally molded, making them promising candidates for ship lightweighting and vibration and noise reduction. When ships are designed and built using all composite materials, their structural forms differ significantly from steel hulls, resulting in more complex mechanical properties and structural forms. These composite materials include unique structural features found in composite hulls, such as transverse and longitudinal cap-shaped stiffeners, fiber-reinforced composite laminates, PVC core materials, and overlapping connection areas, leading to greater complexity in model creation. Therefore, reasonable simplification of the composite hull structural model is necessary during the vibration and noise performance prediction phase of the design process.

[0003] A search of existing literature revealed that: Literature 1 (CN 115910239 A, 2023.04.04) discloses a modeling method and device for laminates based on composite material layup design, which solves the problems of high complexity and low accuracy in static modeling of composite material structures and effectively improves modeling efficiency; Literature 2 (CN 110837710B, 2023.03.24) discloses a rapid finite element modeling method for composite material structures based on the secondary development function of HyperWorks software, which can automatically create finite element models of composite material structures and improve modeling efficiency; Literature 3 (CN 111898295 A, 2020.11.06) discloses a finite element modeling method for variable stiffness composite material laminates based on Python and Patran.

[0004] Existing publicly available technical literature mainly focuses on finite element modeling methods for simple structures such as composite laminates, but does not cover modeling methods for complex composite structures such as cap-shaped stiffened laminates in the hull structure when establishing vibration and noise prediction models for composite ships. In particular, complex cap-shaped stiffened laminate structures that include transverse and longitudinal cap-shaped stiffeners, fiber-reinforced composite laminates, PVC core materials, and overlapping connection areas are difficult to solve effectively using general modeling methods. Summary of the Invention

[0005] To address the challenge of effectively modeling complex composite material structures like cap-shaped stiffened laminates in ship hulls, a modeling method for acoustic and vibration prediction of cap-shaped stiffened laminates in composite ship hulls is proposed. This method can be used to rapidly establish vibration and noise prediction models for composite ship hulls, effectively reducing modeling costs and enabling the calculation of vibration and noise performance while improving computational efficiency.

[0006] The technical solution of this invention is as follows:

[0007] A modeling method for acoustic vibration prediction of a composite material ship hull cap-shaped stiffened laminate includes the following steps:

[0008] Step 1: Obtain and organize the modeling parameters of the composite material hull cap-shaped stiffened laminated plate structure;

[0009] Step 2: Model the laminate portion of the cap-shaped stiffened laminated slab structure using conventional shell elements;

[0010] Step 3: Model the large cap profile part in the cap-shaped stiffened laminated plate structure using equivalent shell elements. Only consider the cap profile panel and ignore the overlapping areas of the cap edges on both sides. The cap profile and the laminated plate are connected by common nodes. The PVC core material is not directly reflected in the acoustic and vibration prediction model. Its weight is equivalent to that of the cap profile panel.

[0011] Step 4: Model the small cap profile part in the cap-shaped stiffened laminated slab structure using equivalent beam elements. Input the cross-sectional shape of the small cap profile panel into the cross-sectional shape of the beam element, and convert the overall weight and overall tensile modulus of the cap profile into the material density and material elastic modulus of the beam element.

[0012] Step 5: In the cap-shaped reinforced laminated slab structure, the transition connection at the intersection area of ​​the transverse and longitudinal cap profiles is ignored;

[0013] Step 6: The structural loss factor parameters of the composite material cap-shaped stiffened laminated plate structure are obtained based on the impulse response attenuation test, and the acoustic vibration prediction model is further corrected by the loss factor.

[0014] Step 7: Based on the equivalent parameters of the cap-shaped stiffened laminate, perform finite element mesh generation on the composite cap-shaped stiffened laminate structure model according to the requirements of wave theory for element size;

[0015] Step 8: Establish the acoustic fluid domain mesh and define the acoustic infinite element far-field boundary and fluid-structure interaction boundary; this completes the acoustic vibration prediction model of the composite material hull cap-shaped stiffened laminated plate structure.

[0016] Furthermore, step 1 specifically involves:

[0017] Based on the pre-set drawings and mechanical property tests of single-ply specimens, the geometric dimensional parameters and single-ply material parameters of the composite cap-shaped reinforced laminate structure are obtained, including density, anisotropic elastic modulus, Poisson's ratio, and shear modulus.

[0018] 3. The modeling method for acoustic vibration prediction of composite material ship hull cap-shaped stiffened laminated plate according to claim 1, characterized in that step 2 specifically comprises:

[0019] Input the single-ply material parameters described in step 1 into the material manager to create a composite single-ply material model. Then, select a regular shell element in the ply manager and set the ply angle and ply thickness of the single ply according to the laminate ply definition to create a laminate model.

[0020] Furthermore, step 3 specifically involves:

[0021] The panel geometry of the cap profile is modeled using equivalent shell elements, considering only the top and waist portions, ignoring the brim overlap area. The bottom of the waist is connected to the laminated plate using a common-node method. The elastic modulus of the PVC core material in the middle of the cap profile is only about 1% of that of the cap profile panel, having a small impact on the overall stiffness; therefore, the contribution of the PVC core material to the equivalent stiffness of the cap profile is ignored. The density ρ of the equivalent shell element of the cap profile panel after considering the weight of the PVC core material is... s 'Calculate according to formula (1);

[0022]

[0023] Where, ρ s The equivalent density of the laminate is calculated using the following formula:

[0024]

[0025] In the formula, ρ pvc The density of the PVC core material is given. The height of the cap profile section is h, the length of the cap waist is l, the width of the cap brim is a, the cap profile panel is composed of fiber-reinforced laminate, the thickness of the cap profile panel is t, and it contains N layers, where the density of the nth layer is ρ. n The ply thickness is t n The top and bottom widths of the core material are w respectively. t and w b .

[0026] Furthermore, step 4 specifically involves:

[0027] In the composite cap-shaped reinforced laminate structure, the cap profile is modeled using equivalent beam elements. The cross-sectional shape of the cap profile panel is input into the cross-sectional shape of the beam element, and the overall weight and overall tensile modulus of the cap profile are equivalently represented by the material density and elastic modulus of the beam element. The calculation methods for the equivalent density and equivalent elastic parameters of the cap profile equivalent beam element are as follows:

[0028] The equivalent beam element density ρ of the small cap profile after considering the weight of the PVC core material s 'Calculate according to formula (1);

[0029] According to classical laminate theory, the equivalent elastic parameters of composite laminates in a three-dimensional coordinate system are as follows:

[0030]

[0031] υ 12 =-S 12 ·E1 (5)

[0032]

[0033] In the formula, E1 and E2 are the equivalent elastic moduli of the laminate, and υ 12 G is the equivalent Poisson's ratio of the laminate. 12 S is the equivalent shear modulus of the laminate. ij (i,j=1,2,6) is the flexibility matrix of the laminate; the elastic modulus of the PVC core material in the middle of the cap profile is only about 1% of that of the cap profile panel, and has little impact on the overall stiffness. Therefore, the contribution of the PVC core material to the equivalent stiffness of the cap profile is ignored; therefore, the elastic parameters of the small cap profile when simplified modeling with equivalent stiffener elements can be obtained according to equations (1)-(6).

[0034] Furthermore, step 6 specifically involves:

[0035] The loss factor of the composite cap-shaped stiffened laminate structure was obtained based on impulse response decay tests and Hilbert transform. The simplified model was further corrected using the structural loss factor. The loss factor testing procedure is as follows:

[0036] A composite cap-shaped stiffened laminate structure was struck with a hammer, and the acceleration decay signal x(T) on the structure was picked up with an accelerometer. The x(T) was then subjected to a Hilbert transform.

[0037]

[0038] In the formula, H[] represents the Hilbert transform, * represents the convolution symbol, T represents time, and x(T) represents the time-domain decay signal of acceleration measured experimentally. The acceleration signal after Hilbert transform;

[0039] Let x(T) be the real part. Given the imaginary part, construct the analytic signal u(T) of the acceleration response, as follows:

[0040]

[0041] The complex expression for u(T) is:

[0042] u(T)=A(T)e jθT (9)

[0043] In the formula, That is, the envelope of the attenuated signal x(T), with an instantaneous phase of... Therefore, any real function can be re-expressed as x(T) = A(T)cosθ(T); by performing a logarithmic transformation on the envelope of the analytic signal u(t), the decay curve can be obtained. The absolute value of the slope of the attenuation curve is the structural damping η. Dividing it by the frequency ω gives the damping ratio. The damping ratio divided by 2 is the structural loss factor of the tested structure within its frequency band.

[0044] Furthermore, step 7 specifically involves:

[0045] Based on the equivalent parameters of the cap-shaped reinforced laminate, the composite cap-shaped reinforced laminate structural model is meshed according to the analysis frequency requirements.

[0046] The element refinement standard is derived from wave theory. The bending wave wavelength in composite laminate structures is calculated using the following formula:

[0047]

[0048] In the formula, E1, E2, and υ 12 and ρ s The equivalent elastic modulus, equivalent Poisson's ratio, and equivalent density of the laminate are respectively, which can be obtained according to equations (1)-(6). f is the analysis frequency, and δ is the thickness of the laminate. The finite element mesh size of the structure does not exceed 1 / 6 of the minimum bending wave wavelength.

[0049] Furthermore, step 8 specifically involves:

[0050] To ensure the optimal coupling effect between the fluid and the structure, a hemispherical or semi-ellipsoidal fluid domain is established, with a minimum radius R of the fluid domain. f Should meet:

[0051] R f ≥4D (14)

[0052] In the formula, D is the maximum side length of the composite material hull cap-shaped stiffened laminate structure; similarly, when the fluid domain is meshed, its maximum mesh size Δx' should satisfy:

[0053]

[0054] In the formula, c is the speed of sound in water, and f max To analyze the upper limit of frequency;

[0055] Finally, acoustic infinite element boundaries and fluid-structure interaction boundaries are defined at the far-field boundary of the fluid domain and the fluid-structure interaction contact boundary, respectively. This completes all the steps for establishing the finite element model for acoustic and vibration prediction of the composite cap-shaped stiffened laminate structure. After applying the excitation load, subsequent vibration and noise prediction analysis can be performed.

[0056] Furthermore, in step 6, the multi-point loss factors ξ1, ξ2, ..., ξ on the composite cap-shaped stiffened laminate are obtained experimentally. n The average loss factor of the composite cap-shaped stiffened laminate structure can be obtained by taking the arithmetic mean. The calculation formula is:

[0057]

[0058] In the formula, n is the number of acceleration response pick-up points used for loss factor calculation, ξ1, ξ2, ..., ξ n This represents the loss factor at each point.

[0059] Furthermore, if the mesh of the composite hull cap-shaped stiffened laminate structure is a first-order element, then the mesh size Δx should satisfy the following formula:

[0060]

[0061] If the structured mesh is a second-order element, then the structured mesh size Δx should satisfy the following formula:

[0062]

[0063] In the formula, λ min For the minimum bending wave wavelength, f is taken as the upper limit of the analysis frequency. max And δ is taken as the minimum thickness δ in the hat-shaped reinforced laminated slab structure. min .

[0064] The beneficial effects of this invention are as follows:

[0065] This invention proposes a modeling method for acoustic and vibration prediction models of composite material ship hull cap-shaped stiffened laminates, which can be used to quickly establish vibration and noise prediction models of composite material ships, effectively reducing modeling costs, thereby realizing the calculation of vibration and noise performance, and improving calculation efficiency.

[0066] Taking a composite material ship hull plate frame as an example, the typical structural type of this area is a hat-shaped stiffened laminated plate structure. By adopting the sound and vibration prediction model model of the composite material ship hull hat-shaped stiffened laminated plate proposed in this invention, the number of meshes can be reduced by about 60% compared with the full solid fine modeling method, while ensuring the calculation accuracy. The calculation efficiency is greatly improved. Attached Figure Description

[0067] Figure 1 This is a flowchart of a modeling method for acoustic and vibration prediction of a composite material ship hull cap-shaped stiffened laminated plate;

[0068] Figure 2 This is a geometric schematic diagram of a typical composite material cap-shaped reinforced laminate structure in an embodiment of the present invention;

[0069] Figure 3 This is a schematic diagram of a typical cross-section of the cap profile in an embodiment of the present invention;

[0070] Figure 4 This is a schematic diagram of the equivalent reinforcement element modeling of the small cap profile (weak member) in an embodiment of the present invention (showing the cross-sectional shape of the beam element);

[0071] Figure 5 This is a simplified modeling diagram of the cap-shaped reinforced laminate in an embodiment of the present invention;

[0072] Figure 6 This is a schematic diagram of the loss factor test of the cap-shaped reinforced laminate structure in an embodiment of the present invention;

[0073] Figure 7 This is a schematic diagram of the acoustic fluid domain in an embodiment of the present invention;

[0074] Figure 8 This is a comparison chart of vibration calculation results and experimental results for a simplified model of a hat-shaped reinforced laminated plate structure in an embodiment of the present invention.

[0075] Attached image labels:

[0076] 1. Fiber-reinforced composite laminate; 2. Transverse cap profile; 3. Longitudinal cap profile; 4. Longitudinal small cap profile; 5. PVC core material; 6. Intersection area of ​​transverse and longitudinal cap profiles; 7. Overlapping area of ​​cap brim; 8. Cap waist; 9. Cap top; 10. Conventional shell element; 11. Equivalent shell element; 12. Equivalent beam element; 13. Acoustic fluid domain. Detailed Implementation

[0077] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0078] Taking a composite material ship deck frame as an example, the typical structural type in this area is a hat-shaped stiffened laminated plate structure, such as... Figure 2 As shown, the structure includes transverse and longitudinal large cap profiles (strong members), longitudinal small cap profiles (weak members), PVC core material, fiber-reinforced composite laminate, and overlapping connection areas. The cap-shaped stiffened laminate structure was modeled using the general-purpose finite element software ABAQUS.

[0079] Step 1: Obtain and organize the modeling parameters for the composite material hull cap-shaped stiffened laminated plate structure;

[0080] Step 1 specifically involves obtaining the geometric dimensional parameters and single-layer material parameters of the composite material cap-shaped reinforced laminate structure, including density, anisotropic elastic modulus, Poisson's ratio, and shear modulus, based on the preset drawings and mechanical property tests of the single-layer specimens.

[0081] Step 2: Model the laminate portion of the cap-shaped stiffened laminated slab structure using conventional shell elements;

[0082] Specifically, step 2 involves inputting the single-ply material parameters described in step 1 into the Material Manager to create a composite single-ply material model. Then, in the Composite Layup Manager, a conventional shell element is selected, and the ply angle and ply thickness of the single ply are set according to the laminate ply definition to create a laminate model.

[0083] Step 3: Model the large cap profile (strong member) part in the cap-shaped reinforced laminated plate structure using equivalent shell elements. Only consider the cap profile panel, that is, the top and waist of the cap, and ignore the overlapping area of ​​the cap edges on both sides. The cap profile and the laminated plate are connected by common nodes. The PVC core material is not directly reflected in the acoustic and vibration prediction model, and its weight is equivalent to that of the cap profile panel.

[0084] Step 3 specifically involves modeling the panel geometry of the cap profile using equivalent shell elements (corresponding to the general description), considering only the top and waist of the cap, ignoring the overlapping area of ​​the brim, and connecting the bottom of the waist to the laminated plate using a common-node method. The elastic modulus of the PVC core material in the middle of the cap profile is only about 1% of that of the cap profile panel, having a small impact on the overall stiffness; therefore, the contribution of the PVC core material to the equivalent stiffness of the cap profile is ignored. The density ρ of the equivalent shell element of the cap profile panel after considering the weight of the PVC core material is... s 'Calculate according to the following formula.'

[0085]

[0086] Where, ρ s The equivalent density of the laminate is calculated using the following formula:

[0087]

[0088] In the formula, ρ pvc The density of the PVC core material, such as Figure 3 As shown, the hat profile has a cross-sectional height of h, a waist length of l, and a brim width of a. The hat profile panel is composed of fiber-reinforced laminate with a thickness of t. It contains N layers of ply, where the density of the nth ply is ρ. n The ply thickness is t n The top and bottom widths of the core material are w respectively.t and w b .

[0089] Step 4: Model the small cap profile (weak member) part in the cap-shaped reinforced laminated slab structure using equivalent beam elements. Input the cross-sectional shape of the small cap profile panel into the cross-sectional shape of the beam element, and convert the overall weight and overall tensile modulus of the cap profile into the material density and material elastic modulus of the beam element.

[0090] Step 4 specifically involves modeling the small cap profile (weak member) in the composite material cap-shaped reinforced laminate structure using equivalent beam elements. The cross-sectional shape of the small cap profile panel is input into the cross-sectional shape of the beam element, and the overall weight and overall tensile modulus of the cap profile are equivalently represented in the material density and elastic modulus of the beam element. The calculation method for the equivalent density and equivalent elastic parameters of the small cap profile equivalent beam element is as follows:

[0091] The equivalent beam element density ρ of the small cap profile after considering the weight of the PVC core material s 'Calculate as described in step 3;'

[0092] According to classical laminate theory, the equivalent elastic parameters of composite laminates in a three-dimensional coordinate system are as follows:

[0093]

[0094] υ 12 =-S 12 ·E1 (5)

[0095]

[0096] In the formula, E1 and E2 are the equivalent elastic moduli of the laminate, and υ 12 G is the equivalent Poisson's ratio of the laminate. 12 S is the equivalent shear modulus of the laminate. ij (i,j=1,2,6) is the flexibility matrix of the laminate. The elastic modulus of the PVC core material in the middle of the cap profile is only about 1% of that of the cap profile face, and its impact on the overall stiffness is small. Therefore, the contribution of the PVC core material to the equivalent stiffness of the cap profile is ignored. Therefore, the elastic parameters of the small cap profile when simplified modeling using equivalent stiffener elements can be obtained by following steps 3 and 4.

[0097] Step 5: In the composite material cap-shaped reinforced laminate structure, the transition connection at the intersection of the transverse and longitudinal cap profiles is ignored.

[0098] Step 6: The structural loss factor parameters of the composite material cap-shaped stiffened laminated plate structure are obtained based on the impulse response attenuation test, and the acoustic vibration prediction model is further corrected by the loss factor.

[0099] Step 6 specifically involves obtaining the loss factor of the composite cap-shaped stiffened laminate structure based on impulse response decay tests and Hilbert transform, and further refining the simplified model using the structural loss factor. The loss factor testing procedure is as follows:

[0100] A composite cap-shaped stiffened laminate structure was struck with a hammer, and the acceleration decay signal x(T) on the structure was picked up with an accelerometer. The x(T) was then subjected to a Hilbert transform.

[0101]

[0102] In the formula, H[] represents the Hilbert transform, * represents the convolution symbol, T represents time, and x(T) represents the time-domain decay signal of acceleration measured experimentally. This is the acceleration signal after Hilbert transformation.

[0103] Let x(T) be the real part. Given the imaginary part, construct the analytic signal u(T) of the acceleration response, as follows:

[0104]

[0105] The complex expression for u(T) is:

[0106] u(T)=A(T)e jθT (9)

[0107] In the formula, That is, the envelope of the attenuated signal x(T), with an instantaneous phase of... Therefore, any real function can be re-expressed as x(T) = A(T)cosθ(T). By performing a logarithmic transformation on the envelope of the analytic signal u(t), the decay curve can be obtained. The absolute value of the slope of the attenuation curve is the structural damping η. Dividing it by the frequency ω gives the damping ratio. The damping ratio divided by 2 is the structural loss factor of the tested structure within its frequency band. The multi-point loss factor of the composite cap-shaped stiffened laminate is obtained by using the above processing method, and then the average loss factor is obtained by averaging. like Figure 6 As shown, the multi-point loss factors ξ1, ξ2, ..., ξ on the composite cap-shaped stiffened laminate are obtained using the above processing method. n The average loss factor of the composite cap-shaped stiffened laminate structure can be obtained by taking the arithmetic mean. The calculation formula is:

[0108]

[0109] In the formula, n is the number of acceleration response pick-up points used for loss factor calculation, ξ1, ξ2, ..., ξ n This represents the loss factor at each point.

[0110] Step 7: Based on the equivalent parameters of the cap-shaped reinforced laminate, perform finite element mesh generation on the composite cap-shaped reinforced laminate structure model according to the requirements of wave theory for element size.

[0111] Step 7 specifically involves meshing the composite material hat-shaped reinforced laminate structure model according to the analysis frequency requirements, based on the equivalent parameters of the hat-shaped reinforced laminate.

[0112] The element refinement standard is derived from wave theory. The bending wave wavelength in composite laminate structures is calculated using the following formula:

[0113]

[0114] In the formula, E, υ and ρ are the equivalent elastic modulus, equivalent Poisson's ratio and equivalent density of the laminate, respectively, which can be obtained according to steps 3 and 4, f is the analysis frequency and δ is the thickness of the laminate.

[0115] Vibration and noise calculations require that the finite element mesh size of the structure should not exceed 1 / 6 of the bending wave wavelength, when f is taken as the upper limit of the analysis frequency. max And δ is taken as the minimum thickness δ in the hat-shaped reinforced laminated slab structure. min At this time, the wavelength of the bent wave is the smallest, which is λ. min Therefore, the structural grid size Δx of the hat-shaped reinforced laminate should satisfy:

[0116] If the structured mesh is a first-order element, then the structured mesh size Δx should satisfy the following equation:

[0117]

[0118] If the structured mesh is a second-order element, then the structured mesh size Δx should satisfy the following formula:

[0119]

[0120] Step 8: Establish the acoustic fluid domain mesh and define the acoustic infinite element far-field boundary and fluid-structure interaction boundary.

[0121] Step 8 specifically involves establishing a hemispherical or semi-ellipsoidal fluid domain. To fully ensure the coupling effect between the fluid and the structure, the minimum radius R of the fluid domain is... f Should meet:

[0122] R f ≥4D (14)

[0123] In the formula, D is the maximum side length of the composite material hull cap-shaped stiffened laminate structure. Similarly, when meshing the fluid domain, its maximum mesh size Δx' should satisfy:

[0124]

[0125] In the formula, c is the speed of sound in water, and f max To analyze the upper limit of frequency.

[0126] Finally, infinite element boundaries and fluid-structure interaction boundaries are defined at the far-field boundary of the fluid domain and the fluid-structure interaction contact boundary, respectively, as follows: Figure 7 As shown. By applying the excitation load, vibration and noise calculation and analysis can be performed. Figure 8 This is a comparison chart of vibration calculation results and experimental results for a simplified model of a hat-shaped reinforced laminated plate structure in an embodiment of the present invention.

[0127] In summary, the modeling method for acoustic and vibration prediction of composite ship hull cap-shaped stiffened laminated plates proposed in this embodiment of the invention can be used for the rapid establishment of vibration and noise prediction models for composite ship hulls, effectively reducing modeling costs and thereby realizing the calculation of vibration and noise performance while improving computational efficiency. Comparative calculations show that, while ensuring sufficient computational accuracy, the modeling method for acoustic and vibration prediction of composite ship hull cap-shaped stiffened laminated plates proposed in this embodiment of the invention can reduce the number of meshes by approximately 60% compared to the full-solid fine-grained modeling method, resulting in a significant improvement in computational efficiency.

[0128] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A modeling method for acoustic vibration prediction of a composite material ship hull cap-shaped stiffened laminate, characterized in that, The method comprises the following steps: Step 1: Obtain and sort the modeling parameters of the composite hull hat-stiffened panel structure; Step 2: Model the laminate part of the hat-stiffened panel structure by using a conventional shell element; Step 3: Model the large hat section part of the hat-stiffened panel structure by using an equivalent shell element, only consider the hat section panel, ignore the hat edge lap area on both sides, the hat section and the laminate are connected through the node, the PVC core is not directly embodied in the sound and vibration prediction model, and the weight is equivalent to the hat section panel; Step 4: Model the small hat section part of the hat-stiffened panel structure by using an equivalent beam element, input the cross-sectional shape of the small hat section panel into the cross-sectional shape of the beam element, and equivalent the overall weight and overall tensile modulus of the hat section to the material density and material elastic modulus of the beam element; Step 5: Ignore the transition connection in the cross region of the hat-stiffened panel structure; Step 6: Obtain the structural loss factor parameters of the composite hat-stiffened panel structure based on the pulse response decay test, and further correct the sound and vibration prediction model through the loss factor; Step 7: Based on the equivalent parameters of the hat-stiffened panel, the finite element mesh of the composite hat-stiffened panel structure model is divided according to the requirements of the wave theory for the size of the unit; Step 8: Establish the acoustic fluid domain grid, define the acoustic infinite element far field boundary and the fluid-solid coupling boundary; thus the modeling of the sound and vibration prediction model of the composite hull hat-stiffened panel structure is completed.

2. The method of claim 1, wherein, Step 1 is specifically: According to the preset drawing data and the mechanical property test of the single-ply specimen, the geometric size parameters and single-ply material parameters of the composite hat-stiffened panel structure are obtained, including density, anisotropic elastic modulus, Poisson's ratio and shear modulus.

3. The method of claim 1, wherein, Step 2 is specifically: The single-ply material parameters obtained in step 1 are input into the material manager to establish a composite single-ply material model, and then the conventional shell element is selected in the layer manager and the layer angle and layer thickness of the single ply are set according to the layer definition of the laminate to establish a laminate model.

4. The method of claim 1, wherein, Step 3 is specifically: The panel geometry of the large hat profile is modeled using equivalent shell elements, only considering the hat top and hat waist parts, ignoring the hat rim overlap area, and the bottom of the hat waist and the connection part of the laminate are connected in a way of shared nodes; the elastic modulus of the PVC core material in the middle of the hat profile is only about 1% of the hat profile panel, which has little effect on the overall stiffness, so the contribution of the PVC core material to the equivalent stiffness of the hat profile is ignored; the density p of the equivalent shell element of the hat profile panel considering the weight of the PVC core material s calculated according to formula (1); where p s is the equivalent density of the laminate, calculated as follows: where p is the density of the PVC core material, h is the hat section height, l is the hat web length, a is the hat rim width, the hat section panel is comprised of a fiber reinforced laminate, t is the hat section panel thickness, and n is the number of plies, where the density of the nth ply is p n , the ply thickness is t n , and the core top and bottom widths are w t and w b , respectively. pvc n n t b 5. The method of modeling a vibro-acoustic prediction model of a composite hat-stiffened panel of a ship hull of claim 1, wherein, Step 4 is specifically: The small hat section of the composite hat-stiffened panel structure is modeled by using an equivalent beam element, the cross-sectional shape of the small hat section panel is input into the cross-sectional shape of the beam element, and the overall weight and overall tensile modulus of the hat section are equivalent to the material density and material elastic modulus of the beam element; the equivalent density and equivalent elastic parameters of the small hat section equivalent beam element are calculated as follows: Equivalent beam element density p of small cap profile taking into account the weight of PVC core material s Calculated according to formula (1); According to the classical laminate theory, the equivalent elastic parameters of the composite laminate in the three-dimensional coordinate system are as follows: wherein E1, E2 are the equivalent elastic modulus of the laminate, υ 12 υ is the equivalent Poisson's ratio of the laminate, G 12 G is the equivalent shear modulus of the laminate, S ij (i,j = 1,2,6) are the compliance matrix of the laminate; the elastic modulus of the PVC core material in the middle of the hat section is only about 1% of the hat section panel, and has little effect on the overall stiffness, so the contribution of the PVC core material to the equivalent stiffness of the hat section is ignored; therefore, the elastic parameters of the small hat section when simplified modeling with equivalent rib elements can be obtained according to formulas (1)-(6).

6. The method of modeling a vibro-acoustic prediction model of a composite hat-stiffened panel of a ship hull of claim 1, wherein, Step 6 is specifically: The loss factor of the composite hat-stiffened panel structure is obtained based on the pulse response decay test and Hilbert transform, and the simplified model is further corrected through the structural loss factor; the loss factor test process is as follows: The composite hat-stiffened panel structure is struck by a force hammer, and the acceleration decay signal x(T) on the structure is picked up by an accelerometer, and x(T) is subjected to Hilbert transform: where H[] is the Hilbert transform, * is the convolution symbol, T is time, x(T) is the acceleration time-domain decay signal measured by the test, is the Hilbert transformed acceleration signal; with x(T) being the real part, and with y(T) being the imaginary part, the analytic signal u(T) of the acceleration response is constructed, which is expressed as follows: The complex expression of u(T) is as follows: In the formula, That is the envelope of the decay signal x(T), and the instantaneous phase is Therefore, any real function can be represented as x(T) = A(T)cosθ(T); the envelope of the analytical signal u(t) is logarithmically transformed, and the decay curve is obtained The absolute value of the curve slope of the decay curve is the structural damping η, and the damping ratio is obtained by dividing it by the frequency ω The damping ratio divided by 2 is the structural loss factor of the structure in the frequency band 7. The method of modeling a hat-stiffened composite panel acoustic vibration prediction model of claim 1, wherein, Step 7 is specifically: Based on the equivalent parameters of hat-stiffened composite panel, the mesh of hat-stiffened composite panel structure model is divided according to the analysis frequency requirement; The unit refinement criterion is derived according to the wave theory, and the bending wave wavelength in the composite laminate structure is calculated as follows: In the formula, E1, E2, u 12 and p s Equivalent elastic modulus, equivalent Poisson's ratio and equivalent density of the laminate respectively, which can be obtained according to formula (1)-(6), f is the analysis frequency, and d is the thickness of the laminate; the size of the structure finite element grid is not more than 1 / 6 of the minimum bending wave wavelength.

8. The method of modeling a hat-stiffened composite panel acoustic vibration prediction model of claim 1, wherein, Step 8 is specifically: The semi-spherical or semi-elliptical fluid domain is established, and in order to fully ensure the coupling effect of the fluid and the structure, the minimum radius R of the fluid domain should be greater than the maximum radius of the structure f The following conditions should be met: R f ≥4D (14) In the formula, D is the maximum side length of the hat-stiffened composite panel structure of the composite ship body; Similarly, when the fluid domain is divided into grids, the maximum grid size Δx' should satisfy: where c is the speed of sound in water, f max is the upper limit of the analysis frequency; Finally, the acoustic infinite element boundary and the fluid-structure coupling boundary are defined at the far-field boundary and the fluid-structure coupling contact boundary of the fluid domain, respectively, and thus the whole steps of establishing the finite element model for the sound and vibration prediction of the hat-stiffened composite panel structure are completed. Load the excitation load, and then perform subsequent vibration and noise prediction analysis.

9. The method of modeling a vibro-acoustic prediction model of a composite hat-stiffened panel of a ship hull of claim 6, wherein, In step 6, the multi-point loss factors ξ1, ξ2,..., ξn on the hat-stiffened composite panel are obtained by experiments, and the average loss factor of the hat-stiffened composite panel structure can be obtained by taking the arithmetic mean n The calculation formula is as follows: The calculation formula is as follows: In the formula, n is the number of acceleration response pickup points used for the loss factor calculation, ξ1, ξ2,..., ξnare the loss factors of the respective points. n represent the loss factors of the respective points.

10. The method of modeling a vibro-acoustic prediction model of a composite hat-stiffened panel of a ship hull of claim 7, wherein, If the grid of the hat-stiffened composite panel structure of the composite ship body is a first-order unit, the structure grid size Δx should satisfy the following formula: If the structure grid is a second-order unit, the structure grid size Δx should satisfy the following formula: where λ is the minimum bending wave wavelength, f is the upper limit of the analysis frequency, and δ is the minimum thickness of the hat-stiffened laminate structure. min max min where λ is the minimum bending wave wavelength, f is the upper limit of the analysis frequency, and δ is the minimum thickness of the hat-stiffened laminate structure.​​

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