Servo valve core and valve sleeve multi-scale wear fatigue joint simulation method and system

Abstract

The invention discloses a multi-scale wear fatigue joint simulation method and system for a valve element and a valve sleeve of a servo valve, and relates to the technical field of hydraulic control. A geometric model is designed according to structural parameters of a valve structure, and the geometric model is divided into multiple assemblies; defining material parameters of each component, and correspondingly associating the material parameters with each component; defining a wear model of the contact surface of the valve core and the valve sleeve; defining a nonlinear mechanism of the fatigue model; defining a coupling model of a coupling relationship between the wear model and the fatigue model; performing grid division on the geometric model by adopting a dynamic grid updating model, and taking all grid units as simulation analysis objects; performing simulation analysis on the coupling model; according to the simulation result, the wear fatigue coupling failure behavior of the valve element and the valve sleeve is predicted, and the design of the valve element and the valve sleeve is optimized. According to the method, the submicron wear depth prediction precision can be realized, the service life prediction error is reduced compared with that of a traditional method, and a quantitative basis is provided for reliability design and condition-based maintenance of a high-precision servo valve.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic control technology, and in particular to a multi-scale wear and fatigue joint simulation method and system for a servo valve spool and a valve sleeve. Background Art

[0002] In modern servo valve structural design, product fatigue resistance is a key characteristic. New product development requires not only excellent structural reliability and durability, but also minimal weight reduction to enhance load-bearing capacity and product competitiveness. With increasingly competitive markets and significantly shortened product development cycles, lightweight and durable design are receiving increasing attention. Structural fatigue reliability is particularly crucial for the safe operation of servo valve structures, but this often conflicts with lightweight design. Therefore, structural fatigue reliability has become a key focus and development trend in current modern servo valve structural design research.

[0003] Servo valves are widely used in industrial automation, aerospace, and other fields. However, the contact surface between the valve core and the valve sleeve is susceptible to wear and fatigue damage due to long-term impact from high-pressure, high-speed fluids and frequent movement. This not only affects valve performance but can also lead to serious safety accidents. Existing simulation methods often only consider wear or fatigue in isolation, lacking a comprehensive analysis of the coupled effects of the two, making it impossible to accurately predict the actual service life and service quality of servo valves. Summary of the Invention

[0004] The main purpose of this invention is to propose a multi-scale wear and fatigue joint simulation method and system for the servo valve spool and valve sleeve, aiming to solve the simulation problem of the wear and fatigue behavior under complex working conditions that is difficult to accurately simulate.

[0005] To achieve the above objectives, the present invention proposes a multi-scale wear and fatigue joint simulation method and system for a servo valve core and valve sleeve, comprising designing a geometric model according to structural parameters of the valve structure, and dividing the geometric model into multiple components;

[0006] defining material parameters of each of the components, and associating the material parameters with each of the components;

[0007] Define the wear model of the contact surface between the valve core and the valve sleeve;

[0008] Define the nonlinear mechanisms of fatigue models;

[0009] A coupling model that defines the coupling relationship between the wear model and the fatigue model;

[0010] Using a dynamic mesh updating model to mesh the geometric model to form mesh units, and using all mesh units as simulation analysis objects;

[0011] Importing the coupling model into the simulation model software to perform simulation analysis;

[0012] Based on the simulation results, the wear-fatigue coupled failure behavior of the valve core and valve sleeve is predicted, and the design of the valve core and valve sleeve is optimized.

[0013] In one embodiment, the wear model includes:

[0014] Archard wear model, used to describe the relationship between contact surface wear, contact pressure, and sliding distance;

[0015] Adhesive wear model, used to describe the material transfer and shedding caused by adhesion on the contact surface;

[0016] The Archard wear model and the adhesive wear model are linearly superimposed, and temperature correction factors, speed correction factors, pressure correction factors and time correction factors are introduced;

[0017] In one embodiment, the nonlinear mechanism of the fatigue model is as follows:

[0018]

[0019] The number of cycles under each stress is n i , the number of cycles N when the corresponding material undergoes fatigue failure i , the fatigue damage caused by each level of stress is D i .

[0020] In one embodiment, the dynamic grid update model includes the following steps:

[0021] S1: Initial meshing, generating an initial mesh before wear simulation, wherein the initial mesh is divided into denser meshes in the contact area and stress concentration area;

[0022] S2: Node displacement calculation, based on the wear volume of the current time step, calculate the movement distance of each grid node along the surface normal direction;

[0023] S3: Coordinates are updated in real time. The coordinates of each node are adjusted based on the movement distance obtained in step S2 to generate an updated mesh reflecting the wear deformation.

[0024] S4: Periodic mesh reconstruction, which re-meshes the worn area within a preset number of iterations to eliminate deformed elements and maintain mesh density.

[0025] In one embodiment, the coupling model includes the following steps:

[0026] S1: Continuous damage discretization processing, dividing the continuous damage process of wear and fatigue into no less than five discrete stages, each stage corresponding to a different wear depth increment;

[0027] S2: Dynamic stress state calculation, according to the wear depth changes at each stage, the corresponding multi-level equivalent stress is calculated, where the equivalent stress is determined by the bending load, the arm length, the minimum diameter of the specimen, the comprehensive influence coefficient of the normal contact stress and the friction shear stress, and the average stress equivalent conversion coefficient;

[0028] S3: Multi-level damage accumulation modeling, which performs nonlinear superposition of the damage values ​​of each discrete stage to obtain the total damage value;

[0029] S4: Remaining life determination: when the total damage value reaches the preset critical threshold, the component is determined to be failed.

[0030] In one embodiment, the speed correction factor is constructed based on the ratio of the sliding speed to the reference speed. The speed correction factor is in the form of a power function. The speed correction factor is multiplied by the reference wear coefficient to obtain the speed-corrected wear coefficient.

[0031] In one embodiment, a pressure correction factor is constructed based on the ratio of the normal load to the initial normal stress, and the pressure correction factor is in the form of a power function; the pressure correction factor is multiplied by the reference abrasive wear coefficient and the adhesive wear coefficient to obtain the pressure-corrected wear coefficient.

[0032] In one embodiment, a micro-macro cross-scale collaborative modeling method is used to establish a three-dimensional model, and molecular dynamics simulation is used for micro-scale modeling: an interaction model between lubricant molecules and valve core materials is constructed to calculate the critical shear stress threshold for oil film rupture under boundary lubrication conditions; macro-scale modeling is performed through fluid-structure coupling analysis: the shear force distribution of non-Newtonian fluid in the valve core gap is solved by computational fluid dynamics; the fluid load is mapped to a finite element model to calculate the contact stress field of the valve core-valve sleeve.

[0033] In one embodiment, the wear-fatigue coupled failure behavior of the valve core and valve sleeve is predicted by analyzing the nonlinear relationship between the wear morphology evolution and the flow characteristic deviation through an LSTM (long short-term memory) network, and the probability distribution and confidence interval of the remaining useful life (RUL) of the valve core are predicted.

[0034] To achieve the above objectives, the present application also provides a multi-scale wear and fatigue joint simulation system for a servo valve core and valve sleeve, comprising:

[0035] a three-dimensional modeling module configured to establish a three-dimensional geometric model according to structural parameters of the valve structure and divide the model into multiple components;

[0036] The material parameter definition module is connected to the 3D modeling module and is used to define and associate corresponding material parameters for each component;

[0037] The contact surface modeling module is integrated into the 3D modeling module and is used to define the wear model of the contact surface between the valve core and the valve sleeve;

[0038] Nonlinear mechanism definition module, used to establish the nonlinear mechanism of fatigue model;

[0039] The coupling model generation module connects the contact surface modeling module and the nonlinear mechanism definition module, and is used to define the coupling relationship between the wear model and the fatigue model;

[0040] A dynamic meshing module configured to mesh the geometric model using a dynamic mesh updating technique to generate a set of mesh cells required for simulation analysis;

[0041] Simulation analysis module, loads the coupling model and performs simulation analysis;

[0042] The failure prediction and optimization module predicts the wear-fatigue coupled failure behavior of the valve core and valve sleeve based on simulation results and outputs a design optimization solution.

[0043] The technical solution of this invention combines a dynamic mesh update model (mesh encryption and periodic reconstruction in the contact area) with a multi-correction factor wear model (temperature, velocity, pressure, and time corrections) to achieve a coupled wear and fatigue simulation that is closer to actual operating conditions. Dynamic mesh reconstruction solves the stress calculation distortion caused by traditional mesh distortion, while the correction factor model significantly improves the prediction accuracy of contact pressure and wear depth by dynamically compensating for changes in material properties (such as the attenuation effect of temperature changes on hardness and the nonlinear influence of sliding velocity on wear).

[0044] A nonlinear fatigue accumulation model based on a logarithmic function is proposed. By amplifying the damage rate under high-cycle loading, it compensates for the underestimation of long-term service damage by traditional linear methods. This model, combined with multi-level equivalent stress calculations (combining parameters such as bending load and friction shear stress), enables real-time coupled feedback between stress state and wear depth.

[0045] This application solves the problem of insufficient accuracy of traditional simulation methods under complex dynamic working conditions, realizes the coordinated optimization of high-precision prediction, lightweight design and cost control, and provides an efficient technical means for the reliability design of servo valves. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0047] Figure 1 This is a multi-scale simulation flow chart of the servo valve core and valve sleeve;

[0048] Figure 2 This is a multi-scale simulation architecture diagram of the servo valve core and valve sleeve;

[0049] Figure 3 Multi-scale modeling layer diagram for servo valve spool and valve sleeve;

[0050] Figure 4 Health prediction layer diagram for servo valve spool and valve sleeve;

[0051] Figure 5 It is the structural line diagram of the servo valve core and valve sleeve;

[0052] Figure 6 The grid diagram of the servo valve core and valve sleeve;

[0053] Figure 7 for Figure 6 A schematic diagram of the enlarged grid of part A;

[0054] Figure 8 The damage distribution diagram of the servo valve core and valve sleeve under different cycle times;

[0055] Figure 9 This is the distribution diagram of the multi-pressure damage curve of the servo valve core and valve sleeve;

[0056] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0058] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly. Unless otherwise clearly specified and limited, the terms "install", "connect", and "connect" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be a connection between the two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0059] In addition, if there are descriptions of "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" or "second" can explicitly or implicitly include at least one of the features. Moreover, the terms "comprise", "include" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Without further restrictions, an element defined by the sentence "comprises a..." does not exclude the presence of other identical elements in the process, method, article or device including the elements. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0060] Main technical features:

[0061] 1. Multi-scale modeling: A combination of micro- and macro-scale methods is used to model the microscopic morphology and overall structure of the valve core-sleeve contact surface.

[0062] 2. Joint simulation algorithm: A joint simulation algorithm that can simultaneously consider wear and fatigue effects has been developed, and the dynamic behavior of the valve core-sleeve system under different working conditions is simulated through finite element analysis (FEA) and computational fluid dynamics (CFD) technology.

[0063] 3. Health status prediction system: Based on historical data and real-time monitoring information, a health status prediction model is constructed using machine learning algorithms to accurately predict the remaining service life of the servo valve.

[0064] Point 1: Multi-scale modeling:

[0065] 1. Using the micro-macro cross-scale collaborative modeling method, high-precision wear fatigue simulation of the servo valve spool-sleeve contact interface is achieved through the following steps:

[0066] (1) Microscale modeling:

[0067] Molecular dynamics (MD) simulation: Build an interaction model between lubricant molecules (such as hydraulic oil) and valve core materials (such as mold steel) to calculate the critical shear stress threshold for oil film rupture under boundary lubrication conditions;

[0068] Steps: Molecular dynamics (MD) simulation calculation, the material is H13 mold steel (Fe-Cr-Mo-V lattice) / phosphate ester hydraulic oil molecules (tritolyl phosphate), and the boundary lubrication failure is simulated using the ReaxFF force field. The simulation conditions are temperature 80℃, pressure 10MPa, and shear rate 10 9 s -1 Output result: critical shear stress τ for membrane rupture c , critical threshold: the simulated critical shear stress threshold is about 18MPa (oil film rupture criterion: rupture of the phosphate molecule adsorption layer);

[0069] (2) Macroscale modeling

[0070] Fluid-Structure Coupling Analysis: Computational Fluid Dynamics (CFD) is used to determine the shear force distribution of the non-Newtonian fluid within the valve core gap (using the k-omega SST turbulence model). The fluid loads are mapped to a finite element model (FEM) to calculate the contact stress field between the valve core and the valve sleeve.

[0071] Step 1: Non-Newtonian fluid CFD modeling

[0072] Establish a three-dimensional fluid domain model of the valve core-sleeve annular gap, with a mesh size that meets the wall resolution requirement of y+<1;

[0073] Define the constitutive relations of the fluid material:

[0074] The Cross-WLF viscosity model is used to characterize the shear thinning properties of aviation hydraulic oil:

[0075]

[0076] in:

[0077] η0(T) is the temperature-dependent zero shear viscosity;

[0078] λ is the relaxation time (typical value for phosphate ester oil is 0.02-0.05s)

[0079] n is the power law exponent (0.6-0.8)

[0080] Activate the k-omega SST turbulence model and set the inlet turbulence intensity to 5%-10% (corresponding to the typical throttling condition of the servo valve).

[0081] Step 2: Fluid-Structure Interaction Load Transfer

[0082] Using a two-way implicit coupling algorithm:

[0083] 1.CFD calculation to obtain fluid shear stress distribution τ ω and the pressure field P;

[0084] 2. Map the fluid loads to the FEM mesh nodes using conservative interpolation:

[0085] Shear force: F τ =∫ s τ ω ds;

[0086] Pressure: F P =∫ s P·nds

[0087] 3. Apply dynamic load boundary conditions in FEM to consider the time-varying effect of the flow field caused by the valve core movement.

[0088] Step 3: Contact stress field solution

[0089] Create the valve core-sleeve contact pair in ANSYS Mechanical:

[0090] Definition of asymmetric contact: the valve sleeve surface is the rigid target surface, and the valve core is the flexible contact surface;

[0091] The contact pressure is solved using the Augmented Lagrange algorithm, and the friction coefficient μ = 0.05-0.12 (lubricated state);

[0092] Output key parameters: Maximum contact pressure P max and its coordinate position; micro-slip amplitude δ (used for subsequent wear calculation).

[0093] Technical effect: Can capture flow rate mutations caused by micron-level gap changes.

[0094] Example: Oil supply pressure 21MPa, valve core oscillation frequency 250Hz; CFD output maximum shear stress τ max=1.8MPa (located at the throttling side of the valve sleeve); FEM calculated contact pressure P max =150MPa.

[0095] Point 2: Joint simulation algorithm: the formula derivation has been given.

[0096] (1) Cross-scale data interaction

[0097] Wear morphology transfer: When the wear depth Δh calculated by FEM is ≥ 1 μm, local MD mesh reconstruction is triggered;

[0098] Fatigue crack growth: Fatigue accumulation.

[0099] Point 3: Health status prediction system:

[0100] The health status prediction method of the present invention realizes accurate prediction of the remaining useful life (RUL) of the valve core through an LSTM (Long Short-Term Memory) network.

[0101] 1. Input parameter preprocessing:

[0102] Input features: including physical parameters such as wear rate and fatigue damage accumulation output from simulation;

[0103] Feature fusion formula:

[0104]

[0105] X t is the fusion feature vector at time t;

[0106] Δh t is the wear depth increment at time t, μm;

[0107] Δt is the time step, h;

[0108] is the fatigue crack growth rate;

[0109] σ max,t is the maximum contact stress at time t, MPa;

[0110] σ yield is the yield strength of the valve core material, MPa;

[0111] ΔC p,t is the change in oil particle concentration at time t.

[0112] 2. LSTM inference model construction

[0113] (1) Select LSTM architecture: adopt physical-data dual-driven architecture;

[0114] (2) Input layer design: sequence length 100, feature dimension 4

[0115] The input feature vectors are arranged by time step:

[0116]

[0117]

[0118] (3) Hidden layer configuration: 2-layer bidirectional LSTM; number of hidden units: 64 (per layer); Dropout rate: 0.2 (retained during inference to achieve uncertainty quantification).

[0119] (3) Output layer design: Regression output (remaining useful life prediction): The fully connected layer maps the 64-dimensional features into RUL values ​​(unit: hours); Auxiliary output (health status level): Use the softmax function.

[0120] 3. RUL prediction output

[0121] Define the model prediction confidence metric:

[0122]

[0123] σ RUL is the Monte Carlo Dropout standard deviation, μ RUL Monte Carlo Dropout average, when C < 0.8, triggers the manual review process.

[0124] Numerical regression: directly output RUL hours;

[0125] Confidence interval: Generate 95% confidence interval through Monte Carlo Dropout;

[0126] Failure criterion: When the predicted RUL is less than the threshold, a level 3 alarm is triggered.

[0127] Health status classification:

[0128] grade Judgment conditions Maintenance Instructions 0 RUL ≥ 300h and confidence level ≥ 0.9 Normal monitoring 1 100h≤RUL<300h or 0.7≤Confidence<0.9 Planned maintenance 2 RUL<100h or confidence level<0.7 Shut down immediately

[0129] A geometric model is designed based on the structural parameters of the valve structure, and the geometric model is divided into multiple components; the multiple components are divided based on the various combination relationships or functional relationships of the valve structure; the valve structures involved in the embodiments of the present application include various types, including both mechanical valves and electric valves, mechanical valves such as ball valves, butterfly valves, check valves, etc., electric valves such as solenoid valves, servo valves, etc., servo valves include electro-hydraulic, pneumatic or hydraulic types, electro-hydraulic types such as proportional valves, jet tube valves, etc. The geometric model of the valve structure is preliminarily designed based on the performance requirements, such as dimensional requirements, material requirements, various physical parameter requirements, etc. Physical parameters such as vibration performance, high and low temperature, acceleration, etc. are determined according to the product application scenario requirements, and load specifications and design specifications must also be considered.

[0130] Define the material parameters of each component and associate the material parameters with each component. This allows you to associate the material parameters with different structures in the geometric model of the valve structure. For example, if the valve core uses carbide and the valve sleeve uses stainless steel, it also includes material parameters such as hardness and elastic modulus. Each component is associated with the material parameters. This ensures that the designed geometric model meets the design requirements and can also be used to evaluate the performance of the materials of each component in complex environments.

[0131] Define the wear model of the contact surface between the valve core and the valve sleeve; describe the mathematical expression of the surface material loss caused by friction, impact, fatigue and other factors during the relative motion between the two.

[0132] The nonlinear mechanism that defines fatigue models refers to the fact that the accumulation of fatigue damage under cyclic loading is not a simple linear superposition, but a complex dynamic process influenced by multiple factors, including the load sequence, stress amplitude, mean stress, and changes in the material's microstructure. Its core characteristic is the nonlinear relationship between damage rate and loading conditions.

[0133] A coupling model is defined to define the coupling relationship between the wear model and the fatigue model; boundary conditions and initial conditions are set; the influence of different environmental information on the valve structure is introduced. By establishing the above coupling model, important parameters affecting the valve structure can be taken into account, the coupling model of multiple physical fields can be established, and an accurate simulation model of the valve structure can be obtained more comprehensively; through boundary conditions and initial conditions, the constraints of the coupling model can be determined to ensure the uniqueness and stability of the solution and simulate the stress and deformation conditions in the actual engineering environment.

[0134] A dynamic mesh update model is used to mesh the geometric model to form mesh units, and all mesh units are used as simulation analysis objects; mesh division is a common method in existing simulation analysis, and this embodiment also adopts a conventional mesh division method. Through mesh division, complex geometric shapes can be divided into multiple simple units, thereby achieving approximate solutions to complex geometric shapes.

[0135] Import the coupling model into the simulation model software for simulation analysis; different physical fields have their own control equations, and these physical fields are interconnected. By importing the coupling model into the simulation model software, the physical fields and geometric models can be linked. This process is a conventional simulation method. With the help of the powerful computing function of the simulation model software, the distribution and relationship of each physical field can be quickly calculated, thereby providing a basis for design. The finite element simulation model software can use conventional analysis software such as ANSYS, SolidWorks, etc.

[0136] Based on the simulation results, the wear-fatigue coupled failure behavior of the valve core and valve sleeve is predicted. Wear-fatigue coupled failure refers to the comprehensive failure phenomenon caused by the interaction of wear (material surface loss) and fatigue damage (crack propagation caused by cyclic load) between the valve core and valve sleeve under dynamic working conditions. The specific manifestations are:

[0137] Wear-accelerated fatigue: Surface wear causes stress concentration, which promotes the initiation and propagation of fatigue cracks.

[0138] Fatigue exacerbates wear: Fatigue cracks reduce the local strength of the material and increase the wear rate.

[0139] Optimize the design parameters of the valve core and valve sleeve, such as the fit clearance, surface roughness and material hardness; the fit clearance refers to the radial clearance between the contact surfaces of the valve core and the valve sleeve, which directly affects the leakage, friction resistance and wear distribution; the surface roughness refers to the microscopic geometric unevenness of the contact surface (Ra value), which affects the friction coefficient, sealing and fatigue resistance; the material's ability to resist plastic deformation is positively correlated with wear resistance and fatigue resistance.

[0140] 1. Construct a wear-fatigue coupling simulation model: Based on the finite element method, a simulation model of mechanical components is established that takes into account the wear and fatigue coupling effects, including:

[0141] Wear model: The improved Archard wear model is adopted. The Archard wear model is mainly applicable to abrasive wear and fatigue wear, while the adhesive wear theory is applicable to material transfer and shedding caused by adhesion on the contact surface. Combining the two theories can more comprehensively predict the amount of material wear.

[0142] Both wear models are based on macroscopic wear and therefore require modification to be suitable for finite element simulation. The finite element method divides a macroscopic object into a finite number of elements, each composed of nodes, and then simulates and analyzes the macroscopic object using the finite element method. Each node represents a local location. Extending the applicability of the two wear models from macroscopic objects to local locations allows for scientific control of local node coordinates, thereby characterizing material wear and achieving quantitative wear simulation, taking into account the effects of factors such as contact pressure, sliding velocity, and material properties on wear volume.

[0143] Fatigue model: Fatigue model considers the influence of stress assignment, average stress, material properties and other factors on fatigue life. While the valve core and valve sleeve of the servo valve are subjected to bending stress or contact stress, their surfaces are also subjected to sliding friction wear, resulting in coupled damage failure of wear damage and fatigue damage.

[0144] Coupling mechanism: Establish the coupling relationship between wear and fatigue, the influence of surface topography changes caused by wear on contact stress and fatigue crack initiation, and the influence of fatigue crack propagation on contact area and wear amount.

[0145] Wear models include:

[0146] The Archard wear model is used to describe the relationship between contact surface wear, contact pressure, and sliding distance; it considers the effects of contact pressure, sliding speed, material properties, and other factors on wear.

[0147] Archard wear model:

[0148]

[0149] V is the wear volume; S is the sliding distance; P is the normal pressure; H is the hardness of the material; K a Archard is the wear coefficient.

[0150] Adhesive wear model, used to describe the material transfer and shedding caused by adhesion on the contact surface;

[0151] Adhesive wear model:

[0152]

[0153] K b is the adhesive wear coefficient;

[0154] σ y is the yield strength of the material;

[0155] Linear superposition of Archard wear model and adhesive wear model;

[0156]

[0157] (1) In order to improve the applicability of the model, factors such as temperature, speed and pressure are introduced for correction:

[0158] Temperature effect: The hardness (H) of a material changes with temperature (T);

[0159] The temperature correction factor is introduced into the material hardness model to compensate for the influence of temperature changes on the wear resistance of the material.

[0160] Introducing a temperature correction factor f T ,

[0161] f T =e -aT

[0162] H=H0f T =H0e -aT

[0163] H0 is the initial hardness (Pa);

[0164] a is the temperature sensitivity coefficient (K -1 );

[0165] (2) Speed ​​sensitivity: the change of wear coefficient (K) with sliding speed (V);

[0166] The speed correction factor is constructed based on the ratio of the sliding speed to the reference speed. The speed correction factor is in the form of a power function. The speed correction factor is multiplied by the reference wear coefficient to obtain the speed-corrected wear coefficient.

[0167] Introduce a speed correction factor f T ,

[0168]

[0169] m, m1, and m2 are velocity indices (dimensionless, usually positive);

[0170] v is the sliding velocity (m / s);

[0171] v0 is the reference speed (m / s);

[0172] k a0 、k b0 is the base wear coefficient (dimensionless)

[0173] k a (v), k b (v) is the wear coefficient after speed correction.

[0174] (3) Pressure dependence: the effect of normal load (N) on the wear coefficient (K);

[0175] Normal load (N) may affect the wear coefficient (K), especially under high pressure conditions, the wear mechanism may change.

[0176] A pressure correction factor is constructed based on the ratio of the normal load to the initial normal stress. The pressure correction factor is in the form of a power function. The pressure correction factor is multiplied by the benchmark abrasive wear coefficient and the adhesive wear coefficient to obtain the pressure-corrected wear coefficient.

[0177] Introduce a pressure correction factor f N ,

[0178]

[0179] n1 and n2 are pressure indices (dimensionless);

[0180] A is the contact area;

[0181] σ0 is the initial normal stress (Pa);

[0182] K a (N), K b (N) is the wear coefficient after pressure correction.

[0183] (4) Through spatial discretization, the wear behavior of different areas on the contact surface can be described more accurately.

[0184] During finite element simulation analysis, in order to simulate the change of contact surface profile with the number of wear times, it is necessary to obtain the wear depth dh at each unit node, and let dh(x) be the wear depth at the node position x.

[0185] For an infinitesimal contact area dA, assuming that when the relative sliding distance of the contact surface is dS, the wear depth of the area is dh. Dividing both sides of the equation by dA gives:

[0186]

[0187] Where dV / dA=dh is the local wear depth, dP / dA is the local contact pressure at position x, p(x).

[0188] The expression for the wear depth at position x is:

[0189] dh(x)=K l P(x)ds(x)

[0190] K l is the wear coefficient, (MPa) -1 ,K l =K / H.

[0191] (5) Calculation of wear considering time effect:

[0192] Wear is a dynamic process. Over time, the increase in wear causes changes in the geometry of the contact surface, which in turn causes changes in the contact pressure distribution. This interaction further affects the subsequent wear behavior. To more accurately describe this complex phenomenon, we need to introduce the time effect and establish a dynamic wear model. The specific expression is

[0193] Δh(x,t)=K l P(x,t)δ(x,t)

[0194] The relative slip distribution δ(x,t) is defined as the change in surface wear depth at a specific time t and contact surface position x. The time t is discretized into time steps t n , where n is the index of the time step. The time step is Δt, and the expression is:

[0195]

[0196] Combining all correction terms, we get the final corrected Archard wear model:

[0197]

[0198] 2 Establishing fatigue damage model

[0199] (1) Wear damage

[0200] Assuming that wear failure occurs when the wear depth reaches [h], the wear damage D in each stage is wi for

[0201]

[0202] Assuming that the wear damage is linear, wear failure occurs when the cumulative wear damage at each stage reaches 1.

[0203]

[0204] (2) Fatigue damage

[0205] Although the linear fatigue damage accumulation theory is still used in many practical engineering problems, Miner's theory ignores the effects of load sequence and interaction between loads in practical applications, which is inconsistent with actual engineering. The reason is that Miner's theory believes that stresses below the fatigue limit cannot cause fatigue damage and can be ignored in calculations. In fact, stresses below the fatigue limit can still cause crack propagation and aggravate fatigue damage.

[0206] Miner linear theory (basic formula): Assume that the stress levels in the load spectrum are σ i , the number of cycles under each stress is n i , the number of cycles N when the corresponding material undergoes fatigue failure i , the fatigue damage caused by each level of stress is D i When the total damage D caused by each level of stress, that is, the accumulated fatigue damage reaches the critical damage value 1, the material undergoes fatigue failure, that is,

[0207]

[0208] However, in practical applications, the simple linear accumulation assumption often cannot accurately reflect the actual situation. Therefore, fatigue damage evolution is expressed as a nonlinear equation as shown below.

[0209] The nonlinear mechanism of the fatigue model is as follows:

[0210]

[0211] The number of cycles under each stress is n i , the number of cycles N when the corresponding material undergoes fatigue failure i , the fatigue damage caused by each level of stress is D i .

[0212] According to the equivalence of damage, the damage caused by the first-level stress σ1 acting n1 times can be equivalent to the damage caused by the second-level stress σ2 acting n2′ times. Considering the interaction between loads, we have

[0213]

[0214] roll out:

[0215]

[0216] Then the total number of times the second-level stress acts can be equivalent to n2′+n2, and the total damage caused by the two-level stress action is:

[0217]

[0218] The total lifespan is:

[0219]

[0220] Remaining life of level i:

[0221]

[0222] Total life under multi-level stress:

[0223]

[0224] 3. Coupling model of wear damage and fatigue damage

[0225] Since both types of damage are continuous, it is necessary to discretize the continuous damage during the study and divide the total damage stage into several stages. At the same time, the wear damage will also be discretized into several stages. The change in wear depth between each stage will cause the stress state to change, and the stress level will be transformed from the initial single-stage stress to multi-stage stress.

[0226] The equivalent stress of each level can be expressed as

[0227]

[0228] F is the applied bending load, N;

[0229] L is the force arm when F acts, mm;

[0230] d2 is the minimum diameter of the cylindrical specimen, mm;

[0231] σ y is the influence of normal contact stress and friction shear stress on equivalent stress at each damage stage, MPa;

[0232] ψ is the equivalent coefficient that converts the average stress into stress amplitude.

[0233] The total damage under multi-level loads is

[0234]

[0235] The remaining life of level i is

[0236]

[0237] Total life under multi-level stress:

[0238]

[0239] 3. The dynamic grid update model includes the following steps:

[0240] S1: Initial meshing: Generate the initial mesh before wear simulation. The initial mesh is refined in the contact area and stress concentration area.

[0241] S2: Node displacement calculation, based on the wear volume of the current time step, calculate the movement distance d of each grid node along the surface normal direction node ,

[0242] d node =h(x) i

[0243] S3: Coordinates are updated in real time. The coordinates of each node are adjusted based on the movement distance obtained in step S2 to generate an updated mesh reflecting the wear deformation.

[0244] S4: Periodic mesh reconstruction, which re-meshes the worn area within a preset number of iterations to eliminate deformed elements and maintain mesh density.

[0245] 4. The coupling model includes the following steps:

[0246] S1: Continuous damage discretization processing, dividing the continuous damage process of wear and fatigue into no less than five discrete stages, each stage corresponding to a different wear depth increment;

[0247] S2: Dynamic stress state calculation, according to the wear depth changes at each stage, the corresponding multi-level equivalent stress is calculated, where the equivalent stress is determined by the bending load, arm length, minimum specimen diameter, the combined influence coefficient of normal contact stress and friction shear stress, and the average stress equivalent conversion coefficient;

[0248] S3: Multi-level damage accumulation modeling, which performs nonlinear superposition of the damage values ​​of each discrete stage to obtain the total damage value;

[0249] S4: Remaining life determination: when the total damage value reaches the preset critical threshold, the component is determined to be failed.

[0250] Based on the same inventive concept as the aforementioned embodiment, this embodiment further provides a multi-scale wear and fatigue joint simulation system for a servo valve core and a valve sleeve, comprising: a three-dimensional modeling module configured to establish a three-dimensional geometric model according to structural parameters of the valve structure and divide the model into multiple components;

[0251] The material parameter definition module is connected to the 3D modeling module and is used to define and associate corresponding material parameters for each component;

[0252] The contact surface modeling module is integrated into the 3D modeling module and is used to define the wear model of the contact surface between the valve core and the valve sleeve;

[0253] Nonlinear mechanism definition module, used to establish the nonlinear mechanism of fatigue model;

[0254] The coupling model generation module connects the contact surface modeling module and the nonlinear mechanism definition module, and is used to define the coupling relationship between the wear model and the fatigue model;

[0255] A dynamic meshing module configured to mesh the geometric model using a dynamic mesh updating technique to generate a set of mesh cells required for simulation analysis;

[0256] Simulation analysis module, loads the coupling model and performs simulation analysis;

[0257] The failure prediction and optimization module predicts the wear-fatigue coupled failure behavior of the valve core and valve sleeve based on simulation results and outputs a design optimization solution.

[0258] The relevant explanations and examples of each module in the device of this embodiment can refer to the methods of the aforementioned embodiments, and will not be repeated here.

[0259] In addition, the present invention has the following explanation:

[0260] This patent utilizes the method of operating the software in a command stream manner provided by ANSYS software, namely the ANSYS Parameter Design Language (APDL). APDL can define scalar parameters, array parameters, call various expressions, functions, custom macro commands, etc. By writing APDL command streams and calling custom macro commands, contact fatigue analysis of valve cores and valve sleeves can be efficiently completed.

[0261] Conservative interpolation: This method is used to maintain the global integral of physical quantities during data mapping or mesh conversion. Its core goal is to ensure that the total amount of physical quantities (such as mass, energy, and momentum) within the target region is strictly conserved before and after interpolation, thus avoiding the accumulation of computational errors caused by mesh differences.

[0262] K-omega SST model: The K-omega SST model achieves a balance between accuracy and efficiency in engineering turbulence simulations through mixing functions and shear stress correction, making it the preferred model for complex flows (such as separated flows and rotating flows).

[0263] Cross-WLF Model: The Cross-WLF model is a viscosity constitutive model widely used in non-Newtonian fluid flow analysis. Its name derives from the combination of the shear rate-dependent Cross model and the temperature / pressure-dependent WLF equations (Williams-Landel-Ferry equations). This model, through multi-physics coupling, accurately describes the shear thinning, temperature sensitivity, and high-pressure effects of fluids such as polymers and hydraulic fluids. It exhibits significant advantages in scenarios with high shear rates, low temperatures, or high pressures.

[0264] Valve sleeve throttling edge: The valve sleeve throttling edge is a fixed geometric boundary formed by the edge of the valve body annular groove in a hydraulic valve (such as a slide valve, a servo valve), and cooperates with the movable throttling edge on the valve core to form a variable throttling port.

[0265] RUL: Remaining Useful Life (RUL) refers to the expected time or number of uses a device can expect to operate normally before failure. It is a core metric for predictive maintenance. It analyzes the device's current status, historical data, and environmental parameters to predict future health decline trends.

[0266] ANSYS Mechanical: Developed by ANSYS, ANSYS Mechanical is a high-end, general-purpose finite element analysis (FEA) software primarily used for structural mechanics, thermodynamics, and multi-physics coupled simulation analysis. As a core module of the ANSYS Workbench platform, its capabilities cover the entire process from basic linear static analysis to complex nonlinear dynamics solutions.

[0267] The present invention adopts molecular dynamics-finite element cross-scale modeling technology to analyze the nanoscale oil film rupture behavior through the boundary lubrication failure threshold at the microscale, and couples computational fluid dynamics (CFD) and contact mechanics simulation at the macroscale to establish a joint damage model that takes into account micro-wear, particle erosion and high-frequency fatigue accumulation; innovatively proposes a dynamic load spectrum mapping algorithm to convert the servo valve control signal (including the flutter component) into a time-varying mechanical load on the contact interface in real time; further integrates a machine learning module to analyze the nonlinear relationship between the wear morphology evolution and the flow characteristic offset through the long short-term memory network (LSTM), and outputs the remaining useful life (RUL) probability distribution and confidence interval. The present invention can achieve sub-micron wear depth prediction accuracy, reducing the life prediction error by more than 40% compared to traditional methods, providing a quantitative basis for the reliability design and condition-based maintenance of high-precision servo valves.

[0268] It should be understood that the references to "one embodiment" or "one example" throughout the specification mean that the specific features, structures, or characteristics associated with the example are included in at least one example of the present invention. Therefore, the phrases "in one embodiment" or "in one example" appearing throughout the specification do not necessarily refer to the same example. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more examples. Those skilled in the art should also be aware that the examples described in the specification are all optional examples, and the actions and modules involved are not necessarily required for the present invention.

[0269] In various embodiments of the present invention, it should be understood that the size of the serial numbers of the above-mentioned processes does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0270] The flow charts and block diagrams in the accompanying drawings of the present invention illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, program segment or a part of code, and the module, program segment or a part of code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementation schemes, the functions marked in the box can also occur in a different order than those marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which is determined based on the functions involved. It should be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented by a dedicated hardware-based system that performs the specified function or operation, or can be implemented by a combination of dedicated hardware and computer instructions.

[0271] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformation made by utilizing the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A multi-scale wear fatigue joint simulation method for a servo valve core and valve sleeve, characterized in that: Establishing a three-dimensional model according to structural parameters of the valve structure, and dividing the geometric model into multiple components; defining material parameters of each of the components, and associating the material parameters with each of the components; Define the wear model of the contact surface between the valve core and the valve sleeve; Define the nonlinear mechanisms of fatigue models; A coupling model that defines the coupling relationship between the wear model and the fatigue model; Using a dynamic mesh updating model to mesh the geometric model to form mesh units, and using all mesh units as simulation analysis objects; Importing the coupling model into the simulation model software to perform simulation analysis; Based on the simulation results, the wear-fatigue coupled failure behavior of the valve core and valve sleeve is predicted, and the design of the valve core and valve sleeve is optimized.

2. A multi-scale wear fatigue joint simulation method for a servo valve core and a valve sleeve according to claim 1, characterized in that: The wear model includes: Archard wear model, used to describe the relationship between contact surface wear, contact pressure, and sliding distance; Adhesive wear model, used to describe the material transfer and shedding caused by adhesion on the contact surface; The Archard wear model and the adhesive wear model are linearly superimposed, and temperature correction factors, speed correction factors, pressure correction factors and time correction factors are introduced.

3. The multi-scale wear fatigue joint simulation method of a servo valve core and valve sleeve according to claim 1, characterized in that: The nonlinear mechanism of the fatigue model is as follows: The number of cycles under each stress is n i , the number of cycles N when the corresponding material undergoes fatigue failure i , the fatigue damage caused by each level of stress is D i .

4. The multi-scale wear fatigue joint simulation method of a servo valve core and valve sleeve according to claim 1, characterized in that: The dynamic grid update model includes the following steps: S1: Initial meshing, generating an initial mesh before wear simulation, wherein the initial mesh is divided into denser meshes in the contact area and stress concentration area; S2: Node displacement calculation, based on the wear volume of the current time step, calculate the movement distance of each grid node along the surface normal direction; S3: Coordinates are updated in real time. The coordinates of each node are adjusted based on the movement distance obtained in step S2 to generate an updated mesh reflecting the wear deformation. S4: Periodic mesh reconstruction, which re-meshes the worn area within a preset number of iterations to eliminate deformed elements and maintain mesh density.

5. The multi-scale wear fatigue joint simulation method of a servo valve core and valve sleeve according to claim 1, characterized in that: The coupling model includes the following steps: S1: Continuous damage discretization processing, dividing the continuous damage process of wear and fatigue into no less than five discrete stages, each stage corresponding to a different wear depth increment; S2: Dynamic stress state calculation, according to the wear depth changes at each stage, the corresponding multi-level equivalent stress is calculated, where the equivalent stress is determined by the bending load, the arm length, the minimum diameter of the specimen, the comprehensive influence coefficient of the normal contact stress and the friction shear stress, and the average stress equivalent conversion coefficient; S3: Multi-level damage accumulation modeling, which performs nonlinear superposition of the damage values ​​of each discrete stage to obtain the total damage value; S4: Remaining life determination: when the total damage value reaches the preset critical threshold, the component is determined to be failed.

6. A multi-scale wear fatigue joint simulation method for a servo valve core and a valve sleeve according to claim 2, characterized in that: The speed correction factor is constructed based on the ratio of the sliding speed to the reference speed. The speed correction factor is in the form of a power function. The speed correction factor is multiplied by the reference wear coefficient to obtain the speed-corrected wear coefficient.

7. The multi-scale wear fatigue joint simulation method of a servo valve core and valve sleeve according to claim 2, characterized in that: A pressure correction factor is constructed based on the ratio of the normal load to the initial normal stress, wherein the pressure correction factor is in the form of a power function; the pressure correction factor is multiplied by the reference abrasive wear coefficient and the adhesive wear coefficient to obtain the pressure-corrected wear coefficient.

8. The multi-scale wear fatigue joint simulation method of a servo valve core and valve sleeve according to claim 1, characterized in that: The three-dimensional model is established using a micro-macro cross-scale collaborative modeling method. Molecular dynamics simulation is used for micro-scale modeling: an interaction model between lubricant molecules and valve core materials is constructed to calculate the critical shear stress threshold for oil film rupture under boundary lubrication conditions; macro-scale modeling is performed through fluid-structure coupling analysis: computational fluid dynamics is used to solve the shear force distribution of non-Newtonian fluids in the valve core gap; the fluid load is mapped to the finite element model to calculate the contact stress field between the valve core and the valve sleeve.

9. The multi-scale wear fatigue joint simulation method of a servo valve core and a valve sleeve according to claim 1, characterized in that: The wear-fatigue coupled failure behavior of the valve core and valve sleeve is predicted by analyzing the nonlinear relationship between the wear morphology evolution and the flow characteristic deviation through the LSTM (long short-term memory) network, and predicting the probability distribution and confidence interval of the remaining useful life (RUL) of the valve core.

10. A multi-scale wear and fatigue joint simulation system for a servo valve core and valve sleeve, characterized in that: include: a three-dimensional modeling module configured to establish a three-dimensional geometric model according to structural parameters of the valve structure and divide the model into multiple components; The material parameter definition module is connected to the 3D modeling module and is used to define and associate corresponding material parameters for each component; The contact surface modeling module is integrated into the 3D modeling module and is used to define the wear model of the contact surface between the valve core and the valve sleeve; Nonlinear mechanism definition module, used to establish the nonlinear mechanism of fatigue model; The coupling model generation module connects the contact surface modeling module and the nonlinear mechanism definition module, and is used to define the coupling relationship between the wear model and the fatigue model; A dynamic meshing module configured to mesh the geometric model using a dynamic mesh updating technique to generate a set of mesh cells required for simulation analysis; Simulation analysis module, loads the coupling model and performs simulation analysis; The failure prediction and optimization module predicts the wear-fatigue coupled failure behavior of the valve core and valve sleeve based on simulation results and outputs a design optimization solution.

Images