Hull corrosion ultimate strength evaluation method based on corrosion real-time monitoring data

Abstract

The invention belongs to the field of hull ultimate strength evaluation, and particularly relates to a hull corrosion ultimate strength evaluation method based on corrosion real-time monitoring data, which comprises the following steps: S1, acquiring thickness data of a hull component plate; s2, calculating profile characteristics of the hull member plate before and after corrosion; s3, calculating the ultimate bending moment and the material yield stress of the hull member plate; s4, evaluating the real-time ultimate strength of the hull component plate under corrosion; according to the method, under the condition that the corrosion influence is considered, real-time dynamic monitoring and evaluation can be carried out on the ultimate strength of the hull structure under the corrosion influence, scientific and reliable data support can be provided through accurate profile reduction and gradual approximate calculation modes, making of a more effective maintenance and repair strategy is helped, and the maintenance and repair efficiency is improved. And the safety and reliability of the hull structure are ensured.

Description

Technical Field

[0001] The present invention belongs to the field of hull ultimate strength assessment, and particularly relates to a method for assessing the corrosion ultimate strength of a hull based on real-time corrosion monitoring data. Background Art

[0002] In a marine environment, the hull structure is long-term exposed to seawater and is vulnerable to the influence of corrosion. Corrosion can lead to the thinning of the plate thickness in the hull structure, thus seriously affecting the structural strength and safety of the hull. The corrosion problem not only threatens the normal navigation of the ship but also may cause major safety accidents. Therefore, it is crucial to monitor the corrosion condition of the hull in real time and dynamically evaluate the ultimate strength of its structure to ensure the safety of ship navigation.

[0003] Traditional hull corrosion monitoring methods mainly rely on regular manual inspections and maintenance. These methods require a large amount of cost and time, and are prone to problems such as data lag, incompleteness, and insufficient accuracy. These defects make it difficult for traditional methods to achieve real-time monitoring of the hull corrosion condition and also unable to dynamically evaluate the influence of corrosion on the hull structural strength, thus restricting the efficiency and scientific nature of ship safety management.

[0004] Existing corrosion monitoring methods based on sensing technology and data analysis can collect the hull plate thickness and corrosion-related data in real time through sensors, and combine data processing and analysis technologies to monitor the corrosion condition of the hull in real time. However, these methods still have deficiencies in terms of systematicness and efficiency. Usually, it is difficult to combine corrosion data with the assessment of hull ultimate strength, and it is also unable to accurately provide scientific maintenance and repair strategies, thus limiting their actual application effects.

[0005] Due to the existence of the above problems, there is an urgent need for a technical method that can achieve real-time monitoring of corrosion data and dynamically evaluate the ultimate strength of the hull structure, so as to improve the safety and reliability of the hull structure, and at the same time provide data support for scientific maintenance and repair decisions. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for assessing the corrosion ultimate strength of a hull based on real-time corrosion monitoring data, dynamically checking and updating the ultimate strength assessment model to ensure more accurate and reliable strength assessment of the hull under corrosion conditions.

[0007] The present invention provides a method for assessing the corrosion ultimate strength of a hull based on real-time corrosion monitoring data, including the following steps:

[0008] S1. Collect the thickness data of the hull component plates:

[0009] Use an ultrasonic thickness gauge to measure the thickness of the hull component plates in real time;

[0010] S2. Calculate the sectional properties of the hull structural plate before and after corrosion:

[0011] According to the thickness data of the hull structural plate before corrosion measured in step S1, calculate the sectional area, static moment, and sectional moment of inertia of the hull structural plate in its initial state;

[0012] According to the thickness data of the hull structural plate after corrosion measured in step S1, calculate the real-time sectional area, static moment, and sectional moment of inertia of the hull structural plate after corrosion;

[0013] S3. Calculate the ultimate bending moment and material yield stress of the hull structural plate:

[0014] According to the compression or tension condition of the hull structural plate, calculate the ultimate bending moment M u ;

[0015] S4. Real-time ultimate strength assessment of the hull structural plate under corrosion;

[0016] Based on the real-time sectional properties after corrosion obtained in step S2, under hogging or sagging conditions, satisfying

[0017]

[0018] it is considered that the ultimate strength of the hull structural plate under this sectional property meets the requirements;

[0019] where M u is the ultimate bending moment obtained in step S3;

[0020] M s is the hydrostatic bending moment;

[0021] M w is the wave added bending moment, calculated by the following formula

[0022] M W = 0.5h·K b ·U1·U2·D·L 2 ·10 -2

[0023] In the formula, h represents the calculated wave height, L represents the design waterline length at normal displacement, D represents the waterline width at the ship's midsection at normal displacement, U1 is the influence coefficient considering the ship speed and hydrostatic bending moment, U2 is the dynamic water pressure correction coefficient, and K b represents the coefficient considering the hull form influence;

[0024] M d is the slamming bending moment, calculated by the following formula

[0025] M d = 0.5h·K·BW 2 ·L·10 -2

[0026] In the formula, h represents the calculated wave height, with the unit of m, K is a coefficient, which is calculated by K = 0.1338·(L / T) 0.5 -0.4486, where B w is the waterline width at the midship of the ship under normal displacement.

[0027] This technical solution realizes that under the consideration of the corrosion effect, it can not only monitor and evaluate the ultimate strength of the hull structure under the corrosion effect in real time and dynamically, but also provide scientific and reliable data support through accurate section reduction and step-by-step approximation calculation methods, helping to formulate more effective maintenance and repair strategies to ensure the safety and reliability of the hull structure.

[0028] In some of these embodiments, in step S2, the cross-sectional area A of the initial state of the hull member plate is:[[]]

[0029] A = ∑A i (1)

[0030] where A i is the area of the i-th small region into which the initial cross-section of the hull member plate is divided;

[0031] The static moment B of the initial state of the hull member plate is:[[]]

[0032] B = ∑A i ·Z i (2)

[0033] where Z i represents the distance from the centroid position of the i-th small region into which the initial cross-section of the hull member plate is divided to the reference axis.

[0034] In some of these embodiments, the moment of inertia I of the initial state of the hull member plate is:[[]]

[0035] I = C - ε 2 ·A

[0036] where C is the moment of inertia of the reference axis of the initial state of the hull member plate, which is calculated according to C = ∑A i ·Z i 2 + i0, A i is the area of the i-th small region into which the initial cross-section of the hull member plate is divided, Z i represents the distance from the centroid position of the i-th small region into which the initial cross-section of the hull member plate is divided to the reference axis, and i0 is an influence factor, which is a fixed value;

[0037] ε is the distance between the neutral axis of the hull structural plate and the reference axis, calculated according to ε = B / A, where B is the static moment B of the hull structural plate in the initial state, calculated from formula (2); A is the sectional area of the hull structural plate in the initial state, calculated from formula (1).

[0038] In some embodiments, in step S2, before calculating the sectional properties of the hull structural plate after corrosion, it is necessary to calculate the area reduction coefficient φ of the hull structural plate i ,

[0039] φ i = σ e / σ i

[0040] where σ e is the Euler stress, obtained from σ e = 80(100t / b) 2 , where t is the thickness of the hull structural plate and b is the longitudinal frame spacing;

[0041] σ i is the working stress, calculated from σ i = M / I·Z i , where M is the bending moment of the hull structural plate, obtained from M = M s + M w + M d , Ms is the hydrostatic bending moment of the hull structural plate, M w is the wave-induced additional bending moment acting on the hull structural plate, calculated from the formula M W = 0.5hvK b ·U1·U2·D·L 2 ·10 -2 , where h is the calculated wave height, L is the design waterline length at normal displacement, D is the waterline width at the midship at normal displacement, U1 is the influence coefficient considering the ship speed and hydrostatic bending moment, U2 is the dynamic water pressure correction coefficient, and Kb represents the coefficient considering the hull form influence; Md is the slamming bending moment of the hull structural plate, calculated from the formula M d = 0.5h·K·W 2 ·L·10 -2 , where K is a coefficient, calculated from K = 0.1338·(L / T) 0.5 - 0.4486, L is the design waterline length at normal displacement, and T is the draft at the midship at normal displacement.

[0042] In some embodiments, in step S2, the sectional area A' of the hull structural plate in real time after corrosion is:

[0043] A' = A + ΔA = A + ∑A i ·(φ i - 1)

[0044] Wherein, A is the cross - sectional area of the hull member plate in the initial state, A i is the area of the i - th small region into which the initial cross - section of the hull member plate is divided, and φ i is the area reduction coefficient of the hull member plate;

[0045] The static moment of the hull member plate after corrosion is B':

[0046] B' = B + ΔB = B + ∑A i ·(φ i - 1)·Z i

[0047] Wherein, B is the static moment of the hull member plate in the initial state, A i is the area of the i - th small region into which the initial cross - section of the hull member plate is divided, φ i is the area reduction coefficient of the hull member plate, and Z i represents the distance from the centroid position of the i - th small region into which the initial cross - section of the hull member plate is divided to the reference axis;

[0048] In some embodiments, the moment of inertia of the cross - section of the hull member plate after corrosion is I':

[0049]

[0050] Wherein, C' is the moment of inertia about the reference axis of the hull member plate after corrosion, C is the moment of inertia about the reference axis of the hull member plate in the initial state, A i is the area of the i - th small region into which the initial cross - section of the hull member plate is divided, and Z i represents the distance from the centroid position of the i - th small region into which the initial cross - section of the hull member plate is divided to the reference axis;

[0051] ε' is the distance from the neutral axis of the hull member plate after corrosion to the reference axis, calculated according to ε' = B' / A', B' is the static moment of the hull member plate after corrosion, and A' is the cross - sectional area of the hull member plate after corrosion.

[0052] In some embodiments, in step S3, when the deck is under compression, the ultimate moment Mu of the hull member plate is the product of the buckling critical stress of the deck and the section modulus of the deck, but not greater than the product of the section modulus of the bottom hull girder and the material yield stress of the bottom hull girder;

[0053] When the deck is under tension, the ultimate bending moment Mu of the hull structural plate is the product of the material yield stress of the deck and the section modulus of the deck, but not greater than the product of the section modulus of the bottom plate girder and the buckling critical stress of the bottom plate girder;

[0054] Among them, the buckling critical stress of the deck, the material yield stress of the bottom plate girder, the material yield stress of the deck, and the buckling critical stress of the bottom plate girder are all known quantities;

[0055] The section modulus of the deck and the section modulus of the bottom plate girder can both be calculated through the formula

[0056] W = I' / l

[0057] where W represents the section modulus after the corrosion area of the deck or the bottom plate girder is reduced, I’ is the section moment of inertia of the hull structural plate after corrosion, and l is the perpendicular distance from the neutral axis to the farthest point of the corresponding hull structural plate section.

[0058] In some embodiments, the mechanical properties of the complex hull structure are equivalent to an overall equivalent beam model. When calculating the ultimate bending moment Mu of the hull structural plate in step S3, the equivalent beam section moduli of the deck and the bottom plate girder are used and obtained by step-by-step approximation calculation. If the difference in the longitudinal normal stress between the latter approximation and the former approximation does not exceed 0.05, the data of the latter approximation is used as the final calculated value; if the final calculated value is less than 0.8 of the equivalent beam section coefficient obtained from the first approximation calculation, measures are taken to improve the stability of the main components of the equivalent beam.

[0059] 1. Based on the above technical solutions, the present invention realizes real-time dynamic monitoring and evaluation of the ultimate strength of the hull structure under the influence of corrosion, and can also provide scientific and reliable data support through accurate section reduction and step-by-step approximation calculation methods, helping to formulate more effective maintenance and repair strategies to ensure the safety and reliability of the hull structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The drawings described herein are used to provide a further understanding of the present invention and form a part of this application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0061] Figure 1 is a flowchart of an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0062] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be described and explained below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments provided in the present application without creative efforts fall within the scope of protection of the present application.

[0063] Obviously, the accompanying drawings in the following description are only some examples or embodiments of the present application. For those of ordinary skill in the art, without creative efforts, the present application can also be applied to other similar scenarios based on these drawings. In addition, it can also be understood that although the efforts made in such a development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some design, manufacturing or production changes based on the technical content disclosed in the present application are only conventional technical means and should not be understood as the content disclosed in the present application being insufficient.

[0064] Referring to "embodiments" in the present application means that the specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those of ordinary skill in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments without conflict.

[0065] This embodiment takes the midship section of a certain in-service dock ship as an example to monitor the corrosion situation of the in-service dock ship in real time, and carry out research work on the assessment of the corrosion limit strength under the hogging and sagging states of the hull based on the service environment, that is, different corrosion years of 10 years, 15 years, 20 years, and 25 years. The specific steps are as follows:

[0066] S1. Collect the thickness data of the hull structural plates:

[0067] Use an ultrasonic thickness gauge to measure the thickness of the hull structural plates in real time, and record the thickness data of the hull structural plates before corrosion and the thickness data of the hull structural plates after corrosion;

[0068] S2. Calculate the sectional properties of the hull structural plates before and after corrosion:

[0069] According to the thickness data of the hull structural plates before corrosion measured in step S1, calculate the sectional area, static moment and sectional moment of inertia of the initial state of the hull structural plates; specifically:

[0070] The sectional area A of the hull structural plates in the initial state is:

[0071] A = ∑A i (1)

[0072] where A i is the area of the i-th small region into which the initial cross-section of the hull structural plate is divided;

[0073] The static moment B of the hull structural plate in the initial state is:

[0074] B = ∑A i ·Z i (2)

[0075] where Z i represents the distance from the centroid position of the i-th small region into which the initial cross-section of the hull structural plate is divided to the reference axis;

[0076] The moment of inertia I of the hull structural plate in the initial state is:

[0077] I = C - ε 2 ·A

[0078] where C is the moment of inertia of the reference axis of the hull structural plate in the initial state, calculated according to C = ∑A i ·Z i 2 + i0, A i is the area of the i-th small region into which the initial cross-section of the hull structural plate is divided, Z i represents the distance from the centroid position of the i-th small region into which the initial cross-section of the hull structural plate is divided to the reference axis, and i0 is the influence factor, which is a fixed value;

[0079] ε is the distance from the neutral axis of the hull structural plate to the reference axis, calculated according to ε = B / A, B is the static moment B of the hull structural plate in the initial state, calculated from formula (2); A is the cross-sectional area of the hull structural plate in the initial state, calculated from formula (1);

[0080] Before calculating the cross-sectional properties of the hull structural plate after corrosion based on the thickness data of the hull structural plate measured in step S1, it is necessary to calculate the area reduction coefficient φ i ,

[0081] φ i = σ e / σ i

[0082] where σ e is the Euler stress, obtained from σ e = 80(100t / b) 2 where t is the thickness of the hull structural plate and b is the longitudinal frame spacing;

[0083] σi is the working stress, calculated by σ i = M / I·Z i where M is the bending moment of the hull structural plate, calculated by M = M s + M w + M d Ms is the hydrostatic bending moment of the hull structural plate, taking hogging as positive,

[0084] M w is the additional wave bending moment on the hull structural plate, calculated by the formula

[0085] M W = 0.5h·K b ·U1·U2·D·L 2 ·10 -2

[0086] where h is the calculated wave height, L is the designed waterline length at normal displacement, D is the waterline width at the midship at normal displacement, U1 is the influence coefficient considering the ship speed and hydrostatic bending moment, U2 is the dynamic water pressure correction coefficient, and Kb represents the coefficient considering the hull form influence; Md is the slamming bending moment of the hull structural plate, calculated by the formula M d = 0.5h·K·W 2 ·L·10 -2 where K is a coefficient, calculated by K = 0.1338·(L / T) 0.5 - 0.4486, L is the designed waterline length at normal displacement, and T is the draft at the midship at normal displacement;

[0087] Calculate the real-time sectional area, static moment, and sectional moment of inertia of the hull structural plate after corrosion, specifically:

[0088] The real-time sectional area A' of the hull structural plate after corrosion is:

[0089] A' = A + ΔA = A + ∑A i ·(φ i - 1)

[0090] where A is the sectional area of the hull structural plate in the initial state, A i is the area of the i-th small area divided by the initial section of the hull structural plate, and φ i is the area reduction coefficient of the hull structural plate;

[0091] The static moment of the hull structural plate after corrosion is B':

[0092] B' = B + ΔB = B + ∑A i ·(φ i - 1)·Z i

[0093] Wherein, B is the static moment of the hull structural plate in the initial state, and A i is the area of the i-th small area into which the initial cross-section of the hull structural plate is divided, and φ i is the area reduction coefficient of the hull structural plate, and Z i represents the distance from the centroid position of the i-th small area into which the initial cross-section of the hull structural plate is divided to the reference axis;

[0094] The moment of inertia of the hull structural plate after corrosion is I':

[0095]

[0096] Wherein, C' is the moment of inertia of the reference axis of the hull structural plate after corrosion, C is the moment of inertia of the reference axis of the hull structural plate in the initial state, and A i is the area of the i-th small area into which the initial cross-section of the hull structural plate is divided, and Z i represents the distance from the centroid position of the i-th small area into which the initial cross-section of the hull structural plate is divided to the reference axis;

[0097] ε' is the distance from the neutral axis of the hull structural plate after corrosion to the reference axis, calculated according to ε' = B' / A', where B' is the static moment of the hull structural plate after corrosion, and A' is the cross-sectional area of the hull structural plate after corrosion;

[0098] S3. Calculate the ultimate moment and material yield stress of the hull structural plate:

[0099] Calculate the ultimate moment M of the hull structural plate according to whether the hull structural plate is under compression or tension u ;

[0100] When the deck is under compression, the ultimate moment Mu of the hull structural plate is the product of the buckling critical stress of the deck and the section modulus of the deck, but not greater than the product of the section modulus of the bottom hull girder and the material yield stress of the bottom hull girder;

[0101] When the deck is under tension, the ultimate moment Mu of the hull structural plate is the product of the material yield stress of the deck and the section modulus of the deck, but not greater than the product of the section modulus of the bottom hull girder and the buckling critical stress of the bottom hull girder;

[0102] Wherein, the buckling critical stress of the deck, the material yield stress of the bottom hull girder, the material yield stress of the deck, and the buckling critical stress of the bottom hull girder are all known data;

[0103] The section modulus of the deck and the section modulus of the bottom hull girder can both be obtained through the formula

[0104] W = I' / l

[0105] It is calculated that, where W represents the section modulus after the reduction of the corrosion area of the deck or the bottom frame plate, I’ is the moment of inertia of the hull member plate after corrosion calculated in step S2, and l is the perpendicular distance from the neutral axis to the farthest point of the section of the hull member plate.

[0106] According to the calculated section modulus of the deck and the section modulus of the bottom plate frame of the ship, the ultimate bending moment M of the hull member plate can be calculated. u ;

[0107] When calculating the ultimate bending moment M of the hull member plate u In this implementation, the equivalent beam method is adopted. Due to the complexity of the hull plate structure, including plates, skeletons and other components, it is difficult to directly solve during analysis. To simplify the analysis, the mechanical properties of these complex components are equivalent to an overall "equivalent beam" model. The equivalent beam can more accurately reflect the overall strength and stiffness characteristics of the hull under the action of bending moment by comprehensively considering the section characteristics of longitudinal members, transverse members and plates; when performing the section reduction analysis of the hull plate structure under corrosion, during the first approximate calculation of the equivalent beam elements, that is, when calculating the section characteristics before the area reduction caused by corrosion in step S2, the section areas of the longitudinal members are all included, and in the second and subsequent calculations of the equivalent beam elements, the plates with a width of 0.25 times the longitudinal frame spacing on both sides of the rigid longitudinal skeleton are not reduced.

[0108] When calculating the ultimate bending moment M u The section modulus of the equivalent beam used is obtained by step-by-step approximate calculation. If the difference in the longitudinal normal stress between the latter approximation and the previous approximation does not exceed 0.05, the data of the latter approximation is used as the final calculated value; if the final calculated value is less than 0.8 of the section coefficient of the equivalent beam obtained from the first approximate calculation, measures are taken to improve the stability of the main components of the equivalent beam.

[0109] S4. Real-time ultimate strength assessment of the hull member plate under corrosion;

[0110] Based on the real-time section characteristics after corrosion obtained in step S2, under the hogging or sagging conditions, satisfying

[0111]

[0112] It is considered that the ultimate strength of the hull member plate under this section characteristic meets the requirements;

[0113] Among them, M u is the ultimate bending moment obtained in step S3;

[0114] M s is the hydrostatic bending moment;

[0115] M w is the wave added bending moment, which is calculated by the following formula

[0116] M W = 0.5h·K b ·U1·U2·D·L 2 ·10 -2

[0117] where h represents the calculated wave height in m, L represents the designed waterline length at normal displacement, D represents the waterline width at the ship's midsection at normal displacement, U1 is the influence coefficient considering the ship speed and still water bending moment, U2 is the dynamic water pressure correction coefficient, and K b represents the coefficient considering the hull form influence;

[0118] M d is the slamming bending moment, calculated by the following formula

[0119] M d = 0.5h·K·B W 2 ·L·10 -2

[0120] where h represents the calculated wave height in m, K is a coefficient calculated by K = 0.1338·(L / T) 0.5 - 0.4486 using the designed waterline length L at normal displacement and the draft at the midsection T at normal displacement, and B W is the waterline width at the ship's midsection at normal displacement.

[0121] By sorting out the actual monitoring data, based on the numerical values of sectional area, static moment, moment of inertia, etc. under the corrosion influence of different time periods, 10 years, 15 years, 20 years, and 25 years obtained from the monitoring, the ultimate strength of the hull structure is dynamically calculated and checked. The working conditions during the check include two conditions of hogging and sagging. The ultimate strength check results are shown in Tables 1 to 4:

[0122] Table 1 Check results of sectional elements and ultimate strength under the 10-year ultimate condition

[0123]

[0124] Table 2 Check results of sectional elements and ultimate strength under the 15-year ultimate condition

[0125]

[0126]

[0127] Table 3 Check results of sectional elements and ultimate strength under the 20-year ultimate condition

[0128]

[0129] Table 4 Check results of sectional elements and ultimate strength under extreme conditions for 25 years

[0130]

[0131] The above results show that the ratios of the ultimate bending moments in the hogging and sagging conditions of the midship section to the sum of the hydrostatic bending moment, wave - induced additional bending moment, and slamming bending moment are greater than 1.5, that is, the ultimate strength of the ship meets the code requirements during 25 years of service.

[0132] This technical solution realizes the real - time dynamic monitoring and evaluation of the ultimate strength of the hull structure under the influence of corrosion, and can also provide scientific and reliable data support through accurate sectional reduction and step - by - step approximation calculation methods, helping to formulate more effective maintenance and repair strategies to ensure the safety and reliability of the hull structure.

[0133] Finally, it should be noted that the embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.

[0134] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that: modifications can still be made to the specific implementation manners of the present invention or equivalent replacements can be made to some technical features; without departing from the spirit of the technical solutions of the present invention, they should all be covered within the scope of the technical solutions claimed by the present invention.

Claims

1. A method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data, characterized in that: The steps include: S1. Collect thickness data of hull component plates: Use ultrasonic thickness gauge to measure the thickness of hull structure plates in real time; S2. Calculate the cross-sectional characteristics of the hull plate before and after corrosion: Calculate the cross-sectional area, static moment and cross-sectional moment of inertia of the hull component plate in the initial state according to the thickness data of the hull component plate before corrosion measured in step S1; According to the thickness data of the hull component plate after corrosion measured in step S1, the real-time cross-sectional area, static moment and cross-sectional moment of inertia of the hull component plate after corrosion are calculated; S3. Calculate the ultimate bending moment and material yield stress of the hull component plate: According to the compression or tension of the hull component plate, the ultimate bending moment M of the hull component plate is calculated. u ; S4. Real-time ultimate strength assessment of hull plate under corrosion: Based on the real-time cross-section characteristics after corrosion obtained in step S2, under the condition of mid-hogging or mid-sagging, the following conditions are satisfied: That is, it is considered that the ultimate strength of the hull component plate under the section characteristics meets the requirements; Among them, M u is the limit bending moment obtained in step S3; M s is the still water bending moment; M w is the additional wave bending moment, which is calculated by the following formula M W =0.5h·K b ·U1·U2·D·L 2 ·10 -2 Where h represents the calculated wave height, L represents the design waterline length at normal displacement, D represents the waterline width at the swell of the ship at normal displacement, U1 is the coefficient taking into account the influence of speed and hydrostatic bending moment, U2 is the correction coefficient for dynamic water pressure, and K is b Represents the coefficient taking into account the linear shadow; M d is the impact bending moment, which is calculated by the following formula M d =0.5h·K·B W 2 ·L·10 -2 Where h represents the calculated wave height, K is the coefficient, which is obtained by the design waterline length L at normal displacement and the midship draft T at normal displacement through K = 0.1338 (L / T) 0.5 -0.4486 is calculated, B w The waterline width at midships at normal displacement.

2. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 1 is characterized in that: In step S2, the cross-sectional area A of the hull component plate in the initial state is: A=∑A i (1) Among them, A i is the area of ​​the i-th small region into which the initial section of the hull component plate is divided; The static moment B of the initial state of the hull component plate is: B=∑A i ·Z i (2) Among them, Z i It represents the distance from the reference axis to the center of gravity of the ith small area into which the initial section of the hull component plate is divided.

3. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 2 is characterized in that: The section moment of inertia I of the hull component plate in the initial state is: I=C-e 2 ·A Wherein, C is the reference axis inertia moment of the hull component plate in the initial state, according to C = ∑A i ·Z i 2 +i0 calculated, A i is the area of ​​the ith small region into which the initial section of the hull component plate is divided, Z i It represents the distance from the reference axis to the center of gravity of the ith small area into which the initial section of the hull component plate is divided, i0 is the influencing factor, which is a fixed value; ε is the distance between the neutral axis of the hull component plate and the reference axis, which is calculated according to ε=B / A; B is the static moment B of the hull component plate in the initial state, which is calculated by formula (2); A is the cross-sectional area of ​​the hull component plate in the initial state, which is calculated by formula (1).

4. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 1 is characterized in that: In step S2, before calculating the cross-sectional characteristics of the hull component plate after corrosion, it is necessary to calculate the area reduction coefficient φ of the hull component plate i , f i =s e / s i Among them, σ e is the Euler stress, from σ e =80(100t / b) 2 Calculate, t is the thickness of the hull component plate, b is the longitudinal bone spacing; σ i is the working stress, and σ i =M / I·Z i Calculated, where M is the bending moment of the hull member plate, M = M s +M w +M d Calculated, Ms is the still water bending moment of the hull component plate, M w is the additional wave bending moment on the hull member plate, which is given by the formula M W =0.5h·K b ·U1·U2·D·L 2 10 -2 Calculated, where h is the calculated wave height, L is the design waterline length at normal displacement, D is the waterline width at the swell at normal displacement, U1 is the influence coefficient of speed and static water bending moment, U2 is the correction coefficient of dynamic water pressure, Kb represents the coefficient of linear shadow; Md is the slamming bending moment of the hull component plate, which can be obtained by the formula M d =0.5h·K·W 2 ·L·10 -2 Calculate, where K is the coefficient, K = 0.1338 (L / T) 0.5 -0.4486, L is the design waterline length at normal displacement, T is the midship draft at normal displacement.

5. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 4 is characterized in that: In step S2, the real-time cross-sectional area A' of the hull component plate after corrosion is: A'=A+ΔA=A+∑A i ·(φ i -1) Wherein, A is the cross-sectional area of ​​the hull component plate in the initial state, A i is the area of ​​the i-th small area into which the initial section of the hull component plate is divided, φ i is the area reduction factor of the hull component plate; The static moment of the hull component plate after corrosion is B': B'=B+ΔB=B+∑A i ·(φ i -1)·Z i Wherein, B is the static moment of the initial state of the hull component plate, A i is the area of ​​the i-th small area into which the initial section of the hull component plate is divided, φ i is the area reduction factor of the hull component plate, Z i It represents the distance from the reference axis to the center of gravity of the ith small area into which the initial section of the hull component plate is divided.

6. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 5 is characterized in that: The section moment of inertia of the hull component plate after corrosion is I': I'=C'-ε' 2 ·A'=(C+ΔC)-ε' 2 ·A'=C+∑A i ·(φ i -1)·Z i 2 -ε' 2 ·A' Wherein, C' is the reference axis inertia moment of the hull component plate after corrosion, C is the reference axis inertia moment of the hull component plate in the initial state, A i is the area of ​​the ith small region into which the initial section of the hull component plate is divided, Z i Indicates the distance from the reference axis to the center of gravity of the ith small area into which the initial section of the hull component plate is divided; ε' is the distance of the neutral axis from the reference axis after the corrosion of the hull component plate, which is calculated according to ε'=B' / A', B' is the static moment of the hull component plate after corrosion, and A' is the cross-sectional area of ​​the hull component plate after corrosion.

7. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 6 is characterized in that: In step S3, when the deck is compressed, the ultimate bending moment Mu of the hull component plate is the product of the critical buckling stress of the deck and the section modulus of the deck, but is not greater than the product of the section modulus of the bottom plate frame and the material yield stress of the bottom plate frame; When the deck is stretched, the ultimate bending moment Mu of the hull component plate is the product of the material yield stress of the deck and the section modulus of the deck, but is not greater than the product of the section modulus of the bottom plate frame and the critical stress of buckling of the bottom plate frame; The critical buckling stress of the deck, the material yield stress of the bottom frame, the material yield stress of the deck, and the critical buckling stress of the bottom frame are all known quantities; The section modulus of the deck and the section modulus of the bottom frame can be calculated by the formula W=I' / l It is calculated that, where W represents the section modulus of the deck or bottom frame plate after the corrosion area is reduced, I' is the section moment of inertia of the hull component plate after corrosion, and l is the perpendicular distance from the neutral axis to the farthest point of the corresponding hull component plate section.

8. The method for evaluating the ultimate strength of hull corrosion based on real-time corrosion monitoring data according to claim 7 is characterized in that: The mechanical properties of the complex hull structure are equivalent to an overall equivalent beam model. When calculating the ultimate bending moment Mu of the hull component plate in step S3, the equivalent beam section modulus of the deck and the bottom plate frame is used, and is obtained by stepwise approximate calculation. If the difference between the total longitudinal normal stress in the latter approximation and the previous approximation does not exceed 0.05, the latter data is used as the final calculated value; if the final calculated value is less than 0.8 of the equivalent beam section coefficient obtained by the first approximate calculation, measures are taken to improve the stability of the main components of the equivalent beam.

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