Search

CN-122021476-A - Ship fatigue damage evolution model parameter calculation method under multi-field coupling effect

CN122021476ACN 122021476 ACN122021476 ACN 122021476ACN-122021476-A

Abstract

The invention provides a method for calculating parameters of a ship fatigue damage evolution model under the action of multi-field coupling, which relates to the technical field of marine structure fatigue damage prediction, and the method comprises the steps of collecting environmental foundation fields, discrete phase medium fields and ship motion field historical data of a target sea area to construct a dynamic boundary sequence, establishing a ship-crushed ice-wave coupling model based on a CEL method, and acquiring stress time courses of key parts such as a ship bow, a ship side, a ship bottom and the like in real time; and then, a rain flow counting method is adopted to process the stress time course to generate a multi-stage load spectrum, a corrected S-N curve is obtained by combining with fatigue tests at different temperatures, finally, the load spectrum is substituted into the correction curve in sequence, the residual fatigue life of each key part under the condition of considering the historical accumulated damage and the real-time temperature is calculated, and the accurate prediction of the fatigue damage of the ship structure under the polar navigation environment is realized.

Inventors

  • CHEN LING
  • ZHOU CHENYAN
  • LI XIAOQUAN
  • LIU WEITING
  • YANG FENG
  • YANG JIE
  • GAO YU

Assignees

  • 南通理工学院

Dates

Publication Date
20260512
Application Date
20260414

Claims (9)

  1. 1. A method for calculating parameters of a ship fatigue damage evolution model under the action of multi-field coupling is characterized by comprising the following specific steps: step 1, acquiring historical environment basic field data of a target sea area, discrete phase medium field data and hull motion field data, and constructing a dynamic boundary sequence based on the data, wherein the environment basic field data comprises sea water density and sea water dynamic viscosity, the discrete phase medium field data comprises ice coverage rate, ice layer thickness, elastic modulus of ice, compressive strength and fracture energy, and the hull motion field data comprises the speed, course angle, roll angle and pitch angle of a hull; Step 2, constructing a ship body-crushed ice-wave coupling model based on CEL, applying a dynamic boundary sequence to the coupling model, acquiring stress of key parts of the ship body in real time, and extracting stress time courses of the key parts, wherein the key parts of the ship body comprise a bow, a side and a bottom; Step 3, processing the stress time course of each key part by using a rain flow counting method to obtain stress amplitude and stress average values of the key parts under each stress cycle, and further generating a multi-stage load spectrum of each key part; Step 4, preparing a test piece based on steel used by the ship body, performing fatigue tests on the test piece at different temperature points, obtaining basic S-N functions at the different temperature points, and correcting the basic S-N functions based on historical accumulated damage; And 5, substituting the load spectrums of different key parts into the corrected S-N function in sequence, and calculating the residual fatigue life of each key part when the load spectrums are applied each time.
  2. 2. The method for calculating the parameters of the fatigue damage evolution model of the ship body under the action of multi-field coupling according to claim 1 is characterized in that the principle of constructing the dynamic boundary condition sequence in the step 1 is as follows: the method comprises the steps of collecting environmental basic field data, discrete phase medium field data and hull motion field data of a target sea area in the past year day by day, dividing continuously-changed data into a plurality of discrete states according to each data, determining the probability of converting one state into another state, constructing a state transition probability matrix of each data, and constructing a dynamic boundary sequence through a Markov chain Monte Carlo method.
  3. 3. The method for calculating the parameters of the fatigue damage evolution model of the ship body under the action of multi-field coupling according to claim 2 is characterized in that the principle on which continuously changing data are divided into a plurality of discrete states is as follows: based on the sea water density range and sea water dynamic viscosity range in the history data, equally dividing the sea water density range and the sea water dynamic viscosity range into three sections between a maximum value and a minimum value, wherein each section is set to be in a state; Dividing the ice coverage rate into five states within the range of 0-100%, namely no ice, the ice coverage rate is 0-10%, a small amount of ice, the ice coverage rate is 10-30%, medium ice, the ice coverage rate is 30-60%, multiple ice, the ice coverage rate is 60-90%, and the full coverage is 90-100%; based on the thickness of the ice layer, the elastic modulus, the compressive strength and the breaking energy of the ice in the historical data, acquiring a corresponding range according to each data, and equally dividing 5 sections between the minimum value and the maximum value of the range, wherein each section represents a state; in the range of the navigational speed of the ship body, the ship body is equidistantly divided into three sections, which correspond to three states, namely a low speed, a medium speed and a high speed; Equally dividing the course angle within a range of 0-360 degrees, wherein each angle range corresponds to one state; Based on the roll angle and pitch angle range of the hull in the historical data, the ship hull is equally divided into three sections between the maximum value and the minimum value, and each section corresponds to one state.
  4. 4. The method for calculating the fatigue damage evolution model parameters of the ship under the action of multi-field coupling according to claim 1, wherein the principle of constructing the ship-crushed ice-wave coupling model in the step 2 is as follows: acquiring a three-dimensional geometric model of a ship body, introducing finite element software, discretizing the three-dimensional geometric model of the ship body by using Lagrange grids, acquiring the density, the elastic modulus, the Poisson ratio and the yield strength of a ship body material, introducing the obtained three-dimensional geometric model into the discretized three-dimensional geometric model, and constructing a Lagrange finite element model of a ship body structure; establishing Euler body grids comprising a water area and an ice area around a ship body to construct an Euler domain, wherein the Euler body grids comprise two material components, namely a water material and an ice material, the water material is defined by adopting a Newton fluid constitutive model, and the ice material is defined by adopting Drucker-Prager yield criteria and combining damage evolution criteria; And establishing a plurality of contact pairs between the Lagrangian finite element model surface of the hull structure and the Euler domain, wherein the contact pairs are areas where the hull structure and the Euler domain are contacted with each other, calculating contact force of each contact pair based on a penalty function method, applying the contact force of each contact pair to Lagrangian grid nodes corresponding to the hull structure, causing deformation and movement of the hull structure, realizing coupling between the hull structure and crushed ice and waves through the contact force, and constructing the hull-crushed ice-wave coupling model.
  5. 5. The method for calculating the parameters of the fatigue damage evolution model of the ship body under the action of multi-field coupling according to claim 1, wherein the principle of extracting the stress time interval of each key part in the step 2 is as follows: applying a dynamic boundary sequence to the coupling model, discretizing the total time of the dynamic boundary sequence into a plurality of time points, and recording the stress of each key position at each time point, thereby obtaining the stress time course of the key position.
  6. 6. The method for calculating the parameters of the fatigue damage evolution model of the ship body under the action of multi-field coupling as set forth in claim 5, wherein the principle of generating the multi-stage load spectrum of each key part in the step 3 is as follows: for each key part, the stress time course is processed based on a rain flow counting method to generate a plurality of stress loops, and the specific principle is that for each stress time course, the stress corresponding to three continuous time points is read from the stress time course and respectively recorded as Wherein Representing the stress corresponding to the first point in time, Representing the stress corresponding to the second point in time, Representing the stress corresponding to the third time point, judging whether the three time points can form a stress cycle, wherein the specific judgment principle is that if the stress is satisfied Is between the values of And The stress amplitude and the stress mean value of the stress cycle are calculated, the stress amplitude is half of the absolute value of the difference between the stress of the first two time points of the stress cycle, the stress mean value is half of the sum of the stress of the first two time points of the stress cycle, then the first two time points of the stress cycle are deleted from the time sequence, the third time point is reserved, and whether the stress cycle can be formed or not is continuously judged with other time points according to the same method; The tensile strength of the ship steel is obtained, the stress amplitude of each stress cycle is extracted and corrected to be equivalent stress amplitude, the concrete principle of correction is that for each stress cycle, the ratio of the stress average value to the tensile strength under the stress cycle is calculated, 1 is used as the quotient of the stress average value and the tensile strength, and the result of dividing the stress amplitude of the stress cycle by the quotient is used to obtain the equivalent stress amplitude of the stress cycle; Sequencing the equivalent stress amplitudes of all the stress cycles according to a sequence from large to small, dividing a section between the maximum value and the minimum value of the equivalent stress amplitudes into a plurality of equidistant micro sections, counting the number of the stress cycles in each micro section, merging the stress cycles falling in the same micro section, setting the equivalent stress amplitudes of the micro section as the average value of the equivalent stress amplitudes of all the stress cycles in the micro section, and generating a plurality of simplified data points, wherein the specific form is as follows: , wherein, Represent the first The equivalent stress amplitude of each micro-segment, An index indicating the micro-segment is provided, Represent the first The number of stress cycles between the micro-cells; Dividing by 8-level load spectrum standard, finding the minimum equivalent stress amplitude and the maximum equivalent stress amplitude from the reduced data points, calculating the logarithmic difference between the maximum equivalent stress amplitude and the minimum equivalent stress amplitude, dividing by the number of stages of the load spectrum to obtain a logarithmic interval, sequentially defining the stress logarithmic interval of each stage from the minimum equivalent stress amplitude, calculating the left end point calculation principle of each stress logarithmic interval by multiplying the logarithmic interval after calculating the difference between the number of stages and 1, and adding the obtained product to the minimum equivalent stress amplitude, calculating the product of the number of stages and the logarithmic interval, adding the obtained product to the minimum equivalent stress amplitude, taking the midpoint of each logarithmic interval, converting the midpoint into a linear value as the representative stress amplitude under the number of stages, traversing all the reduced data points until all the reduced data points are distributed in the logarithmic interval of the corresponding number of stages, recording the total stress cycle number of each stage, and generating a plurality of load spectrums, wherein each element in the load spectrum has the form of , wherein, Represent the first Representative stress amplitude of the level load spectrum, An index representing the number of load spectrum stages, Represent the first Total stress cycle times for the stage load spectrum.
  7. 7. The method for calculating the parameters of the fatigue damage evolution model of the ship under the action of multi-field coupling according to claim 6, wherein the principle of obtaining the basic S-N functions at different temperatures in the step 4 is as follows: and selecting a temperature point from-60 ℃ to 20 ℃ at intervals of 10 ℃, performing fatigue test at each temperature point, generating a basic S-N function corresponding to each temperature point, wherein the basic S-N function is a curve which takes the residual fatigue life as a dependent variable, the stress amplitude as an independent variable and the temperature as an influence parameter, fitting a relation between a first material constant and a second material constant and the temperature through a nonlinear least square method, and substituting the relation into the basic S-N function.
  8. 8. The method for calculating the parameters of the model for evolution of fatigue damage of the ship body under the action of multi-field coupling according to claim 7, wherein the principle of correcting the basic S-N function based on the history accumulated damage in the step 4 is as follows: the historical cumulative damage represents a ratio of the fatigue life consumed to the total fatigue life; Processing each test piece on a fatigue testing machine to consume the fatigue life of the test piece, applying different pre-damages to each prepared test piece, wherein the pre-damages represent the historical accumulated damage of the test piece, applying different stress amplitudes to the test piece at the same temperature point, measuring the residual fatigue life of the test piece at the different stress amplitudes, obtaining the S-N function at the temperature point, calculating two damage coupling coefficients based on fatigue test data of a plurality of temperature points, wherein the two damage coupling coefficients comprise an intercept attenuation coefficient and a slope amplification coefficient, the intercept attenuation coefficient is used for describing the attenuation degree of the historical accumulated damage to the intercept of the basic S-N function, the slope amplification coefficient is used for describing the amplification degree of the historical accumulated damage to the slope of the basic S-N function, correcting the first material constant and the second material constant through the intercept attenuation coefficient and the slope amplification coefficient respectively, and further combining the corrected first material constant and the corrected second material constant to obtain the S-N function at the known temperature and the known historical accumulated damage.
  9. 9. The method for calculating parameters of a fatigue damage evolution model of a ship body under the action of multi-field coupling according to claim 8, wherein the principle of calculating the residual fatigue life of the key part when the load spectrum is applied in the step 5 is as follows: For each critical part, apply it to Real-time temperature corresponding to the level load spectrum and the first Substituting the current accumulated damage of the key part before the application of the level load spectrum into the corrected S-N function to obtain the stress amplitude of the material under the current accumulated damage and the real-time temperature Residual fatigue life at that time.

Description

Ship fatigue damage evolution model parameter calculation method under multi-field coupling effect Technical Field The invention relates to the technical field of marine structure fatigue damage prediction, in particular to a ship fatigue damage evolution model parameter calculation method under the action of multi-field coupling. Background In polar region and cold region navigation environment, the hull structure is influenced by wave, broken ice, low temperature and other multi-field coupling effects for a long time, and the fatigue damage evolution process presents high complexity and uncertainty. The traditional ship fatigue evaluation method is generally based on a single load condition or a simplified environment assumption, and is difficult to accurately reflect the influence of the cooperation of multiple physical fields on the fatigue life of a ship structure in actual sea conditions. Especially under the ice area navigation condition, the stress concentration and accumulated damage of key parts are obviously aggravated by the coupling effect of broken ice impact, wave load and ship movement, and the lack of a system modeling and parameter calculation method for the complex process in the prior art leads to insufficient fatigue life prediction precision, so that the actual requirements of polar ship engineering design are difficult to meet. Therefore, there is a need for a method for calculating parameters of a fatigue damage evolution model of a ship body, which can comprehensively consider the multi-field coupling effect, dynamic environment change and material fatigue performance degradation mechanism, so as to realize accurate prediction of the residual fatigue life. In the prior art, publication No. CN118395815A discloses a method for calculating parameters of a fatigue damage evolution model of a marine structure, and obtaining engineering stress of a metal plateEngineering strain curve according to engineering stressCalculating the yield strength, tensile strength and elastic modulus of the metal plate according to the strain curve, and obtaining the stress of the metal plate under different strain amplitude loadingStrain hysteresis curves based on stress under loading of different strain amplitudesCalculating nonlinear isotropy hardening model parameters of the metal plate by using the strain hysteresis curve, and obtaining back strain force of the metal plate under the loading of each strain amplitudeA plastic strain curve according to the back strain force under the loading of each strain amplitudeAnd obtaining the nonlinear follow-up hardening model parameters of the metal plate by using the plastic strain curve. The main problem of the scheme is that the influence of the coupling effect of wave, sea ice, low temperature and other physical fields on the fatigue performance of the material is not considered only based on the material performance test of the metal plate under the condition of normal temperature and single mechanical loading. In actual ocean engineering, a structure is under the condition of combined action of complex load and environment for a long time, a large deviation exists between a prediction result of a fatigue damage evolution model and an actual use scene due to neglect of a multi-field coupling effect, dynamic response of an unbonded structure under actual sea conditions is only dependent on a material-level cyclic loading test, fine modeling of structural local stress response is lacking, fatigue damage evolution of a key part is difficult to evaluate accurately, and although hardening model parameters of a material are extracted, the hardening model parameters are not effectively coupled with a structural fatigue life prediction model, and complete mapping from material performance to structural response is lacking. The above information disclosed in the background section is only for enhancement of understanding of the background of the disclosure and therefore it may include information that does not form the prior art that is already known to a person of ordinary skill in the art. Disclosure of Invention The invention aims to provide a method for calculating parameters of a ship fatigue damage evolution model under the action of multi-field coupling, so as to solve the problems in the background art. In order to achieve the above purpose, the present invention provides the following technical solutions: The method for calculating the parameters of the fatigue damage evolution model of the ship under the action of multi-field coupling comprises the following specific steps: step 1, acquiring historical environment basic field data of a target sea area, discrete phase medium field data and hull motion field data, and constructing a dynamic boundary sequence based on the data, wherein the environment basic field data comprises sea water density and sea water dynamic viscosity, the discrete phase medium field data comprises ice coverage rate, ice layer thickne