169 results about "Stress intensity factor" patented technology

The invention discloses an engine additive component service life prediction method based on modal polycondensation and expansion, and the method specifically comprises the steps: firstly, achieving the grid discretization of an initial defect structure based on a finite element method, and carrying out the local refinement of a defect region; performing modal polycondensation on the overall model to obtain a low-dimensional system model, and performing rapid calculation under the low-dimensional model to obtain modal response; establishing a conversion relation between a displacement vibration mode and a stress vibration mode, and obtaining full-field stress by utilizing modal response and based on modal extension; and solving a stress intensity factor-time history of the crack tip by adopting a stress extrapolation method, obtaining a delta K-R-n three-variable rain flow matrix by utilizing a rain flow counting method, and finally carrying out residual life evaluation through an iLAPS model. According to the method, system dynamics, fracture mechanics and modal order reduction technologies are fused, a new efficient and accurate fatigue life prediction path adapting to complex working conditions is provided for additive manufacturing components with defects, and the method has remarkable engineering application value and popularization potential.

The invention provides a cable bending fatigue life prediction method and system based on reinforcement learning, and relates to the technical field of cable life prediction, and the method comprises the steps: collecting cable test sample data, calculating a stress distribution field and a strain distribution field, constructing a stress intensity factor calculation module, and calculating a crack propagation track and rate. A damage evolution tensor is constructed as a state feature, a network is trained based on a deep Q learning algorithm, uncertainty is quantified by adopting a Markov chain Monte Carlo method, and a credible interval and an early warning threshold are established.

The invention discloses a method and device for predicting the fatigue life of a high-temperature alloy vacuum electron beam welding structure, and belongs to the technical field of aero-engines. The method comprises the following steps: acquiring fatigue experiment data of a target high-temperature alloy standard sample; extracting the maximum area of an initial defect, a defect shape factor and crack source position information; obtaining a stress intensity factor range considering defect morphological characteristics and a fatigue crack propagation threshold value of a material structure containing initial defects, and correcting a damage tolerance theoretical formula to obtain simulation data; fatigue test data and simulation data are fused to form an initial data set, a fatigue limit is calculated and expanded to the data set, the expanded data set serves as input, training is conducted through a support vector regression method, hyper-parameters are determined through Bayesian optimization, and a fatigue life prediction result of the high-temperature alloy vacuum electron beam welding structure is output. The method provided by the invention can well consider the influence of different morphology defects on the fatigue performance of the welded joint.

The invention relates to the technical field of structural engineering, and provides a surface crack fatigue propagation morphology and life prediction method based on machine learning, which comprises the following steps: establishing a finite element simulation model containing a surface crack, calculating a stress intensity factor of the front edge of the surface crack, and generating a finite element simulation data set; performing dimensionless processing on parameters in the simulation data set to generate a machine learning data set; optimizing the back propagation neural network through a hybrid optimization algorithm, and constructing a surface crack stress intensity factor prediction model; the surface crack stress intensity factor prediction model is combined with a fatigue crack growth rate formula to cyclically predict the surface crack growth morphology and the service life of the load bearing structure; establishing a visual interaction interface of parameter input and output and image output based on the surface crack stress intensity factor prediction model and the fatigue crack growth rate formula; a user can quickly predict the propagation morphology of the surface crack and calculate the service life without mathematical analysis and code writing.

The invention discloses an active learning and physical loss-based fatigue crack growth rate prediction method, which comprises the following steps of: splicing and fusing a preprocessed stress intensity factor, a stress ratio, pre-strain and stress amplitude, and taking the fused characteristics as the input of a model; embedding the Jones model into a loss function of the neural network, constructing a physical information time sequence model based on the Jones model, setting a parameter set, selecting a most valuable training sample from a training set by using active learning, retraining the model by using the selected most valuable training sample, selecting an optimal model, and evaluating the optimal model by using a test set; fusing the actually measured stress intensity factor, stress ratio, pre-strain and stress amplitude of the to-be-predicted material, and inputting into the obtained prediction model to obtain a predicted value of the fatigue crack growth rate. By adopting the technical scheme of the invention, the fatigue crack growth rate of the material in the whole life period can be efficiently and accurately predicted at low cost.

The invention belongs to the technical field of aircraft strength experiments, and particularly relates to a hybrid-driven metal multi-fatigue crack propagation fusion prediction method. The method comprises the following steps: establishing a stress intensity factor expression under multiple fatigue cracks; initial distribution of material parameters in the Paris physical model is obtained, and posterior distribution of the material parameters is adjusted; based on the stress intensity factor expression under the multi-fatigue crack and the posterior distribution of the material parameters, obtaining an improved Paris physical model for describing the multi-fatigue crack propagation process; a depth encoder network model is established, and a network bottleneck layer is utilized to extract guided wave deep features with strong correlation with the fatigue crack length; establishing a guided wave data driven multi-fatigue crack length online monitoring model; and building a particle filter fusion framework, and correcting and improving a distribution interval of uncertain material parameters in the Paris physical model according to guided wave monitoring data to realize dynamic tracking and prediction of metal multi-fatigue crack propagation.

The invention discloses a PSO-SVR-based FSW joint fatigue crack propagation life prediction method and electronic equipment, and the method comprises the steps: simulating a crack propagation process of an FSW joint through a finite element simulation technology, obtaining a crack tip stress intensity factor, a corresponding loading load size and a crack length of the FSW joint in the process as a group of data, and constructing a data set; performing standardization processing on the constructed data set, and then dividing the data set into a training set and a test set; and training a machine learning model by using the training set, evaluating the trained model by using the test set, and performing hyper-parameter optimization on the model until an optimal crack tip stress intensity factor prediction model is obtained. According to the PSO-SVR-based FSW joint fatigue crack propagation life prediction method and the electronic equipment provided by the embodiment of the invention, finite element simulation data and test data are fused, so that the time cost and expense for constructing the fatigue crack propagation life model are effectively reduced, and the method and the electronic equipment have the advantages of high calculation efficiency, high prediction precision and the like.

The invention discloses a test-based crystal plasticity and cohesion model coupling hydrogen induced cracking simulation method, which comprises the following steps: carrying out a hydrogen filling mechanical property test on a metal material to obtain a true stress-true strain curve of the metal material in a hydrogen environment; carrying out a hydrogen-filled fracture toughness test on the metal material to obtain a stress intensity factor of the metal material in a hydrogen environment; constructing a cohesion constitutive model; a metal material electron back scattering diffraction microscopic characterization test is carried out, microstructure characteristics are obtained, and a polycrystalline model is constructed; constructing a crystal plastic constitutive model; coupling crystal plasticity constitutive and cohesion constitutive, and calibrating crystal plasticity to-be-determined parameters by adopting a trial-and-error method; and carrying out finite element simulation analysis on hydrogen-induced cracking behaviors with different microstructure characteristics in a hydrogen environment to obtain stress-strain data and crack data of the hydrogen-induced cracking behaviors. According to the invention, high-precision simulation of the hydrogen-induced cracking micromechanism of the metal material in the hydrogen environment is realized.

The invention discloses a design method of a periodically-arranged porous thin-wall combustion chamber flame tube characteristic simulation piece, which comprises the following steps: carrying out fluid-thermal-solid coupling analysis in a real structure service environment, obtaining the temperature field distribution of a combustion chamber flame tube and the size and direction of a first principal stress, and determining a part with the maximum first principal stress as a dangerous part; inserting an initial crack into a dangerous part of a real component, carrying out crack propagation numerical simulation, and extracting a stress intensity factor change rule on a crack propagation path; on the basis of keeping key geometric characteristics of a periodically arranged porous structure, a simulation piece is configured and designed into a biaxial flat plate stretching piece, and stress gradient distribution of a real component is matched through porous array parameter optimization; a biaxial tensile testing machine is adopted to apply a multi-axial load to the simulation part, and it is ensured that the stress intensity factor amplitude under different crack lengths is kept consistent with that of a real component. The method has important engineering value for damage tolerance evaluation and life prediction of the aero-engine combustion chamber.

The invention provides a method and system for evaluating fatigue crack life of a welding structure under a random load, and relates to the technical field of rail transit, and the method comprises the steps: recognizing a load peak value and a load valley value through a point-by-point extreme value extraction method, and generating an equivalent variable-amplitude load data set; initial crack propagation rate parameters C and m and stress intensity factor distribution are calculated, and then a deterministic crack propagation increment result is output; a hierarchical Bayesian framework is combined with an MCMC sampling method, and global parameter distribution considering material heterogeneity and observation noise is generated through a posterior distribution formula; predicting crack depth evolution curves under different confidence coefficients, and outputting fatigue life probability distribution and confidence intervals; and finally generating a fatigue life reliability evaluation report of the welding structure under the random load. The method has the beneficial effects that the problem of fatigue crack propagation of the railway vehicle welding structure under the action of the complex random load can be better solved, and more accurate and reasonable technical support is provided for reliability evaluation of the welding structure.

The application discloses a brake interface wear and fatigue crack prediction method based on complete thermal-mechanical coupling, comprising the following steps: S1, establishing a finite element model, and discretizing total analysis time into multiple time periods; S2, starting finite element analysis, and calculating interface node contact pressure and node slip rate; S3, performing transient thermal-mechanical coupling analysis; S4, calculating node wear depth and wear direction, and updating grid information by using ALE technology; S5, judging whether the interface contact state is stable convergence; S6, ending analysis, unloading brake load, and obtaining brake disc residual stress; and S7, presetting a crack at the maximum residual stress, simulating crack propagation behavior, calculating stress intensity factor and brake disc fatigue life. The application can simulate tribological behaviors such as contact stress, temperature and wear, and realizes brake disc fatigue life prediction by taking residual stress after the thermal-mechanical coupling process as load input.

The invention discloses a method for evaluating rock mass fracture freeze-thaw fracture damage risk based on surface temperature, which comprises the following steps: S1, carrying out data acquisition on a target area based on a multi-source sensor carried by an unmanned aerial vehicle platform, and obtaining fracture geometric parameters, daily surface minimum temperature, daily surface maximum temperature, daily temperature difference and fracture moisture conditions; s2, on the basis of the geometric parameters of the crack, constructing a crack frost heaving force analytical model; obtaining a quantitative relation between the stress intensity factor and the environment temperature; s3, the I-type fracture toughness of the target rock mass is measured, and the critical crack initiation temperature of the rock mass is determined; determining the number of critical freezing and thawing cycles; s4, on the basis of the daily earth surface minimum temperature, the daily temperature difference, the fracture moisture condition and the critical crack initiation temperature, the annual accumulated effective freezing and thawing cycle number is obtained; and calculating a freeze-thaw damage ratio, and carrying out risk quantification and grading. According to the invention, the problem of inaccurate evaluation caused by limitation to local monitoring and lack of an environment factor and material parameter integrated evaluation framework in the prior art is solved.

The invention discloses a method for predicting the service behavior of an oil and gas pipeline under a stress corrosion cracking condition, and belongs to the field of material performance analysis and prediction. Firstly, based on a convection diffusion equation, a real stress intensity factor of an oil and gas pipeline crack tip is used as an unknown quantity to obtain a stress distribution condition; then, applying boundary conditions and a crack propagation criterion in fracture mechanics, and performing preliminary calculation to obtain crack propagation behavior characteristics of the one-dimensional semi-analytical model; and finally, calibrating and calculating the diffusion coefficient of the material parameter in the one-dimensional semi-analytical model to obtain real full-life service time information of the oil and gas pipeline material. According to the method, the full-life behavior information of stress corrosion cracking can be quickly obtained, and a partial differential equation does not need to be solved; on the basis of fracture mechanics, the mechanism of repeated fracture and reconstruction of the passivation layer in the fracture process can be reproduced; the full-life service time of the oil and gas pipeline can be effectively predicted, and the parameter calibration method can be applied to other conditions and is wide in application range.

The invention belongs to the technical field of tunnel water inrush monitoring, and particularly relates to a tunnel water inrush monitoring and early warning method under a water-rock coupling effect, which comprises the following steps: S1, obtaining tunnel data and rainfall data of a historical time sequence, carrying out data processing, and training a preset logistic regression model; s2, acquiring a position cross-section diagram of the water-containing fracture of the tunnel by using a high-density electrical method; s3, selecting the maximum K water-containing fractures based on the position cross-section diagram in the S2, respectively calculating effective method corresponding force sigma'n and shear stress tau'n, and then calculating a stress intensity factor K II; corresponding cracking early warning judgment is carried out; s4, current tunnel data and rainfall data are obtained and processed, and the trained logistic regression model is used for predicting the current water inrush risk probability; and corresponding water inrush early warning judgment is carried out. According to the method, multi-source data can be fused, a water-rock coupling action mechanism is considered, and tunnel water inrush monitoring and early warning are efficiently carried out in real time.

The invention relates to a method for evaluating the crack initiation probability of an RPV surface crack under a transient working condition, and belongs to the field of safety analysis of nuclear pressure-bearing equipment. The method comprises the following steps: sampling a random variable and determining a sampled multivariate sample; calculating a stress intensity factor of the crack evaluation point caused by multiple loads under the transient condition; calculating a stress intensity factor of the crack evaluation point after the influence of the crack tip plastic zone is brought into the transient condition; calculating the reference temperature of the crack evaluation point after neutron irradiation embrittlement is considered under the transient condition; constructing a fracture toughness probability distribution model of the crack evaluation points under the transient condition; calculating the crack initiation probability of the crack at the current moment under the transient condition; judging whether the current moment is the last moment of the transient working condition, if so, ending the calculation process of the crack initiation probability under the transient working condition, and otherwise, updating the transient moment; and evaluating the crack initiation probability of the RPV surface cracks under all samples. According to the method, the crack initiation probability of the RPV surface crack under the transient working condition can be efficiently and accurately evaluated.

The invention relates to the technical field of structural engineering, and provides a surface crack stress intensity factor prediction method and device based on machine learning, and the method comprises the steps: building a finite element simulation model containing a surface crack, calculating the stress intensity factor of the front edge of the surface crack, verifying through an empirical formula, and generating a finite element simulation data set; performing dimensionless processing on the size of the surface crack, the size of the load bearing structure and the stress intensity factor of the front edge of the surface crack in the finite element simulation data set to generate a machine learning data set; optimizing the back propagation neural network through a hybrid optimization algorithm, and constructing a stress intensity factor prediction model based on machine learning; adjusting hyper-parameters of the neural network, and verifying a fitting effect of the stress intensity factor prediction model based on machine learning; based on the stress intensity factor prediction model, establishing a visual interaction interface for related parameter input, image output, prediction result output and comparison result output; while the calculation efficiency is maintained, the calculation precision and the application range are improved.

A risk assessment and control method for radial cracking and crack propagation and transfixion of cement sheath in fracturing wells is provided. Based on the thermo-solid coupling theoretical model of casing-cement sheath-formation combination and thick-walled cylinder theory, the tangential stress distribution of crack-free cement sheath when fracturing is obtained, the maximum tensile stress criterion is used to judge whether the cement sheath has radial initial cracking when fracturing and calculate the initial cracking length, based on the weight function method, the stress intensity factor of the tip of the radial initial cracking of the cement sheath when fracturing is calculated, the fracture mechanics criterion is used to judge whether the radial crack propagation and transfixion will occur in the cement sheath, and the performance parameters of the cement sheath are controlled by the double standards of preventing the radial cracking of the cement sheath and controlling the crack propagation.

The invention discloses a data processing method for segmented fitting of a fatigue crack propagation rate curve, which belongs to the technical field of metal material fatigue crack propagation rate tests, and comprises the following steps: obtaining a data curve to be fitted, determining the amplitude of a stress intensity factor, and setting the range interval of segmented fitting. Fitting data points in the range interval subjected to piecewise fitting to obtain a linear equation, converting the obtained linear equation into a power function form of a Paris formula, and substituting the stress intensity factor amplitude into the power function form of the Paris formula to calculate the corresponding fatigue crack growth rate. According to the method, the calculated fatigue crack growth rate under the specified stress intensity factor amplitude is closer to a real test value, and the fatigue crack growth rate serving as a material engineering application basis is more reliable.

The invention relates to a fatigue crack propagation simulation and life prediction method considering a crack closing effect. The method comprises the following steps: constructing a finite element model; assembling crack sizes in the finite element model according to user requirements, refining regional grids of the cracks, expanding the cracks in the finite element model, extracting a displacement field of the regional grids at the tips of the cracks, performing nonlinear calculation considering a crack closing effect on the basis of the displacement field, and calculating the crack closing effect. Obtaining an I-type stress intensity factor and an II-type stress intensity factor at the tip of the crack; calculating a crack propagation angle based on the I type stress intensity factor and the II type stress intensity factor and based on a maximum circumferential stress criterion, and calculating a new crack tip coordinate based on the crack tip coordinate, the crack propagation angle and a user-defined crack propagation increment; and updating historical crack tip coordinates based on the new crack tip coordinates to update the cracks, and assembling the finite element model until the I-type stress intensity factor is greater than the fracture toughness, and outputting a result in a table form.

A method for predicting ultra-high cycle fatigue life considering the orientation characteristics of crack initiation location. By obtaining a failed specimen, using a scanning electron microscope to scan the fatigue fracture surface of the failed specimen. When there is a fatigue crack initiation source in the fine-grained area of the fatigue fracture surface, repeat the steps; obtain the crack initiation area parameters of the fatigue crack initiation source in the fine-grained area, and the crack initiation area parameters include the projected area of the initiation area and the inclination angle of the initiation area; determine the true area of the initiation area according to the projected area of the initiation area and the inclination angle of the initiation area; obtain the stress intensity factor on the inclined surface of the initiation area of the fatigue crack initiation source in the fine-grained area; establish a fatigue life model according to the true area of the initiation area and the stress intensity factor; predict the fatigue life of the failed specimen according to the fatigue life model to obtain a more accurate life prediction model and improve the accuracy of fatigue life prediction.

The invention provides a stiffened wallboard life prediction method based on a data enhanced physical information neural network, which comprises the following steps: determining influence parameters of crack propagation fatigue life of a stiffened wallboard and a discourse domain of the influence parameters, obtaining sample points through sampling, calculating a stress intensity factor and fatigue life based on a finite element model, and constructing a training set; a double-layer physical information neural network is established, a first sub-model predicts a stress intensity factor by taking an influence parameter as input, a second sub-model combines the influence parameter and a stress intensity factor prediction value, a physical loss function based on a Paris crack propagation law is introduced, training is performed in combination with a data loss function, and fatigue life prediction is realized; and representing the influence parameters as fuzzy variables, obtaining a multi-level-cut set, and predicting the fuzzy response of the fatigue life by using the trained neural network. According to the method, a physical mechanism and data driving can be effectively fused, and efficient prediction of the crack propagation fatigue life of the stiffened wall plate under the uncertain condition is achieved.

The invention relates to the technical field of mechanical structure strength evaluation and structural design, and provides a safety evaluation and design method for a ship longitudinal welding structure, which comprises the following steps: determining a damaged key part; detecting the size of the minimum detectable crack in the ship longitudinal welding structure by adopting a nondestructive detection method; carrying out regularization and normalization processing on the crack obtained by detection; calculating a stress intensity factor amplitude corresponding to the current crack; judging whether the crack is expanded or not by combining a fatigue crack expansion threshold value predicted by a Zhu-Xuan model; based on a nondestructive testing result and a three-dimensional crack propagation analysis model, establishing a crack propagation digital twinborn body; and according to crack propagation prediction results and residual life evaluation results of the crack propagation digital twin under different structure schemes, safety and reliability of different welding structure forms, size parameters and process schemes are compared, and optimal design of the ship longitudinal welding structure is achieved.

The invention provides a fatigue crack propagation life prediction method and system for a mechanical structure, and relates to the technical field of structural fatigue reliability, and the method comprises the steps: solving a stress intensity factor of a crack-containing structure; measuring associated data of the stress intensity factor amplitude delta K and the crack growth rate da / dN under different stress ratios; solving first equivalent crack surface traction force distribution corresponding to the external load and second equivalent crack surface traction force distribution corresponding to the residual stress field; calculating crack propagation effective driving force under variable amplitude load based on a strip yield model; the crack length and the cycle number are updated until the crack expands to the termination length af; calibrating parameters of a fatigue crack growth rate model based on delta KCPD; and superposing the variable-amplitude load spectrum and the equivalent crack surface traction force distribution to the two-dimensional substitute crack body, and generating a fatigue crack propagation life curve of the mechanical structure by a strip yield model. According to the method, quantitative prediction of the fatigue crack propagation life of the mechanical structure is realized, and the method has relatively high solving precision and applicability.

The invention provides an LNG flexible pipeline water hammer-thermal shock coupling fatigue life evaluation method. The method comprises the following steps that an LNG flexible pipeline three-dimensional thermal-mechanical coupling model is established; transient fluid pressure fluctuation and temperature shock in the valve switching process are simulated, and a time-varying temperature field, a stress field and a crack tip stress intensity factor of the pipeline under the water hammer-thermal shock coupling effect are solved; a low-temperature test system is constructed, simulation results and experimental data are compared, and boundary condition parameters in the LNG flexible pipeline three-dimensional thermal-mechanical coupling model are corrected; cyclic load characteristics in the corrected stress response spectrum are extracted based on a rain flow counting method, and in combination with a corrected EPRG empirical model or an SES model, the accumulated fatigue damage amount of the crack-containing pipeline under the water hammer-thermal shock coupling cyclic load is calculated; and predicting the residual fatigue life of the pipeline. According to the method, the prediction precision of the fatigue life of the LNG flexible pipeline under the complex coupling action of the water hammer and the thermal shock is improved.

The application relates to a state evaluation method and device of an object, computer equipment and a system. The method comprises the following steps: acquiring a first crack image of an object to be evaluated; using a regression model to perform prediction based on a first crack parameter in the first crack image, so as to obtain a first stress intensity factor of the object to be evaluated; the regression model is a model for predicting the stress intensity factor, and the regression model is obtained by training a second crack parameter and a second stress intensity factor in a second crack image of a target object, and the second stress intensity factor is simulated based on the second crack parameter; and the state of the object to be evaluated is evaluated based on the first stress intensity factor, so as to obtain a state evaluation result of the object to be evaluated. The method can be used for state evaluation in multiple scenes.

The application discloses a method for determining the allowable damage scale of concrete based on a fracture extremum theory, which comprises the following steps: S1, carrying out a fracture test to obtain a peak load; S2, calculating a stress intensity factor generated by an external load and cohesive force according to a stress intensity factor manual; S3, establishing a crack tip stress intensity factor balance equation according to a crack propagation criterion, and then deducing an expression of the external load; S4, determining a critical effective crack length of the concrete according to the fracture extremum theory; and S5, calculating the allowable damage scale according to the critical effective crack length. The method for determining the allowable damage scale of concrete based on the fracture extremum theory is adopted, the fracture extremum characteristics of the concrete are fully considered, the peak load of the fracture test needs to be measured only when the method is applied to analyze the crack propagation of the concrete, the test operation is simple, the calculation result is high in accuracy, and the method is suitable for test pieces of different sizes and types.

The invention provides an LNG (Liquefied Natural Gas) conveying flexible pipeline crack initiation and extension prediction method, which comprises the following steps of: constructing a multilayer composite structure geometric model, and defining thermal parameters and mechanical parameters of each layer of material in the model; presetting an initial crack in the model, and establishing a thermal-mechanical coupling control equation containing an interface thermal resistance effect; applying an internal ultralow temperature boundary condition, an external environment temperature boundary condition and a mechanical load boundary condition; solving the thermal-mechanical coupling control equation to obtain temperature field distribution of the section of the pipeline, applying a temperature field as a body load to the multilayer composite structure geometric model, and calculating to obtain a stress field and a stress intensity factor of a crack tip; constructing a crack propagation criterion considering the interface thermal resistance effect; and comparing the stress intensity factor obtained by calculation with a crack propagation criterion, and judging whether the crack is propagated or not. According to the method, the physical authenticity and calculation precision of crack initiation and propagation prediction of the LNG flexible pipeline in the ultralow temperature environment are improved.

The invention relates to a nuclear power plant main pipeline damage tolerance establishment method. The method comprises the following steps: S1, determining the critical crack size of the main pipeline of the nuclear power plant at the end of the life; and S2, performing finite element calculation based on the established finite element model of the crack-free structure of the main pipeline so as to obtain stress distribution of the crack-free structure under each load working condition. S3, according to the initial crack size and the finite element calculation result, stress intensity factor calculation, transient pairing, elastic-plastic correction and fatigue crack propagation calculation are conducted in sequence, and the life end crack size of the main pipeline is obtained. And S4, when it is judged that the life end crack size of the main pipeline is smaller than the critical crack size, the step S3 is executed again to conduct iterative calculation on the initial crack size. And when the final crack size of the service life of the main pipeline is judged to be greater than the critical crack size, taking the initial crack size updated by the last iteration as the structural damage tolerance. The nuclear power pipeline defect evaluation period can be shortened, and the evaluation efficiency is improved.

The application discloses a kind of crack propagation prediction method and system of water turbine runner under transient hydraulic excitation, belong to the technical field of water conservancy and hydropower engineering, to solve the technical problem that existing prediction method cannot simulate crack propagation under transient hydraulic excitation.The application is by constructing finite element grid and level set field, encryption grid, identify enhanced node and solve runner time sequence displacement field, then calculate the stress intensity factor and energy release rate of crack front node, and calculate crack propagation direction and rate based on this, thereby update and correct level set field, to obtain the crack after expansion, to realize the accurate simulation of crack propagation under transient hydraulic excitation, provide reliable basis for runner crack monitoring, expansion trend prediction and fracture life assessment.Further, the application can track the crack propagation process from the current small condition to the penetration by multiple iterations, and accurately predict the fracture life of the runner according to the propagation law.

The present invention provides a method and system for predicting the fatigue crack growth life of a mechanical structure, which relates to the technical field of structural fatigue reliability, and includes solving the stress intensity factor of a cracked structure; measuring the correlation data between the stress intensity factor amplitude ΔK and the crack growth rate da / dN under different stress ratios; solving the first equivalent crack surface traction distribution corresponding to the external load and the second equivalent crack surface traction distribution corresponding to the residual stress field; calculating the effective driving force for crack growth under variable amplitude loading based on the strip yield model; updating the crack length and the number of cycles until the crack grows to the termination length a f ; calibrating the fatigue crack growth rate model parameters based on ΔK CPD ; superimposing the variable amplitude load spectrum and the equivalent crack surface traction distribution onto a two-dimensional surrogate cracked body, and generating a fatigue crack growth life curve of the mechanical structure by the strip yield model. The present invention realizes the quantitative prediction of the fatigue crack growth life of the mechanical structure, and has high solution accuracy and applicability.