Bearing bush thermal elastohydrodynamic lubrication bearing capacity calculation method considering surface coating layer

Abstract

The invention provides a bearing bush thermal elastohydrodynamic lubrication bearing capacity calculation method considering a surface coating layer, which is applied to the field of diesel engine main bearing bush lubrication bearing performance evaluation.The method comprises the steps that structural parameters and basic working condition parameters of a bearing bush-journal system and physical attribute parameters of the surface coating layer are obtained, and a parameter set is obtained; constructing a bearing bush thermal elastohydrodynamic lubrication model coupled with the surface coating layer; on the basis of the bearing bush thermal elastohydrodynamic lubrication model of the coupling surface coating layer and coupling iterative calculation, converged bearing bush lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution are obtained; on the basis of converged bearing bush lubricating interface oil film pressure distribution, rough peak contact pressure and temperature field distribution, integral operation is combined to obtain the bearing bush thermal elastohydrodynamic lubrication total bearing capacity under the consideration of the influence of the surface coating layer, and the lubrication bearing performance of the bearing bush containing the surface coating layer under various working conditions can be accurately evaluated. And the method has good applicability in bearing bush structure design and performance evaluation application scenes.

Description

Technical Field

[0001] This invention relates to the field of evaluating the lubrication load-bearing performance of diesel engine main bearings, and in particular to a method for calculating the thermo-elastohydrodynamic lubrication load-bearing capacity of bearings that takes into account the surface coating layer. Background Technology

[0002] During diesel engine operation, the bearing bushes are subjected to a complex alternating load, including rotational centrifugal force, periodic gas force, and reciprocating inertial force. Furthermore, as diesel engine speeds and power outputs increase, the operating conditions of the crankshaft-bearing friction pair become more demanding. Factors such as high loads, high temperatures and pressures, frequent start-stop cycles, lubricant deterioration, and corrosion can easily lead to bearing bush lubrication failure and frictional heat accumulation, resulting in the peeling of the bearing bush surface coating and insufficient bearing load-bearing capacity. Accurately predicting the bearing bush load-bearing capacity helps assess the health status of diesel engine bearing bushes, improving the engine's efficiency and service life.

[0003] Regarding the calculation method for bearing lubrication load, existing patents include: Taking Chinese invention patent CN120633338A as an example, it discloses a method for evaluating the load-bearing capacity of oil-impregnated bearings based on virtual simulation. This method involves executing a partitioning algorithm on the 3D CAD structural model of the oil-impregnated bearing, establishing a multiphysics sensitive area identification model for each partition, and dynamically adjusting the parameters of the global finite element model and the local high-precision micro-element sub-model using a multiphysics coupling calibration factor. The time-series features of the multiphysics joint simulation results after dynamic parameter adjustment are extracted to obtain the multidimensional parameter sequence related to the typical failure mechanism of the oil-impregnated bearing. However, this virtual simulation method lacks the ability to reproduce the failure mechanism under dynamic conditions of combined loads, and fails to systematically reproduce the real physical field evolution process under the alternating superposition of dynamic loads, impacts, and asymmetric conditions. It cannot achieve a high degree of coupling between the multiphysics fields of bearing lubrication, structure, and heat. Taking Chinese invention patent CN120068534A as an example, a method for calculating the time-domain hybrid lubrication characteristics of sliding bearings under deep-sea high-pressure environments is disclosed. Based on the steady-state Reynolds-averaged equation with coupled interface roughness, it considers the contact effect between the shaft and bearing micro-protrusions. By ensuring the balance between the steady-state hybrid lubrication contact force and the external load, the hybrid lubrication characteristics of the shaft and bearing are calculated. However, these methods neglect the effect of the bearing surface coating during modeling, and they can only obtain lubrication characteristics under deep-sea high-pressure environments, lacking versatility.

[0004] However, the technical solutions disclosed in the aforementioned patent documents cannot be fully applied to the special requirements of diesel engine bearings with surface coatings. When calculating lubrication characteristics, the influence of temperature is not mentioned. Under high-speed or heavy-load conditions, the viscosity and density of the lubricant change with temperature, affecting lubrication performance. Furthermore, the experimental measurement of the thermo-elastohydrodynamic lubrication load-bearing capacity of bearings with coupled surface coatings is quite complex. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a method for calculating the bearing capacity under thermo-elastohydrodynamic lubrication considering surface coatings. This method overcomes the limitations of existing finite element virtual simulation methods, such as insufficient versatility and inability to consider surface coatings, as well as the complexity of experimental methods. It can accurately calculate the bearing capacity under thermo-elastohydrodynamic lubrication, specifically including:

[0006] A method for calculating the bearing capacity of a bearing considering a surface coating layer's thermo-elastohydrodynamic lubrication includes:

[0007] S1. Obtain the structural parameters, basic operating condition parameters, and physical property parameters of the surface coating of the bearing-journal system to obtain the parameter set;

[0008] S2. Based on the parameter set, construct a bearing thermo-elasto-hydrodynamic lubrication model with coupled surface coating layer;

[0009] S3. Based on the bearing thermo-elasto-hydrodynamic lubrication model of the coupled surface coating layer and coupled iterative calculation, the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution are obtained.

[0010] S4. Based on the convergent oil film pressure distribution, rough peak contact pressure and temperature field distribution of the bearing lubrication interface, and combined with integral calculation, the total bearing capacity of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

[0011] Optionally, the parameter set in S1 includes: initial oil film thickness, initial pressure, and initial temperature.

[0012] Optionally, the process in S2 of constructing a bearing thermo-elasto-hydrodynamic lubrication model for the coupled surface coating layer based on the parameter set includes:

[0013] S201. Define the average Reynolds control equation for the bearing lubricating oil film. The average Reynolds control equation for the bearing lubricating oil film is Equation (1):

[0014] (1)

[0015] Where p is the lubricating oil film pressure, η is the dynamic viscosity of the lubricating oil film, ρ is the density of the lubricating oil film, h is the thickness of the lubricating oil film, and φ is the density of the lubricating oil film. x φ is the bearing circumferential pressure flow coefficient. y σ is the axial pressure flow coefficient of the bearing, σ is the surface roughness of the lubricating oil film, and φ is the bearing axial pressure flow coefficient. s φ is the shear coefficient of the lubricating oil film. c U is the contact coefficient of the lubricating oil film, U is the journal speed, and x is the circumferential coordinate of the bearing bush.

[0016] S202. Introducing temperature changes, the relationships between the dynamic viscosity η of the lubricating oil and temperature and pressure, and the relationship between the density ρ of the lubricating oil and temperature and pressure are obtained respectively.

[0017] S203. When considering the coating layer on the bearing surface, a temperature field is introduced to obtain the energy equation of the lubricating oil film, which is formula (6):

[0018] (6)

[0019] Among them, c p denoted as the specific heat at constant pressure of the lubricating oil film, k as the thermal conductivity of the lubricating oil film, u as the circumferential velocity of the lubricating oil film, v as the axial velocity of the lubricating oil film, Φ as the heat dissipation work of the lubricating oil film, and T as the current temperature of the lubricating oil film.

[0020] S204. The coating layer on the bearing surface is in direct contact with the oil film and conducts heat. The heat conduction equation of the coating is defined as formula (7):

[0021] (7)

[0022] Among them, c c ρ is the specific heat capacity of the coating material. c k is the density of the coating material. c Z is the thermal conductivity coefficient of the coating material. c The spatial coordinates of the coating;

[0023] S205. Define the heat conduction equation of the bearing substrate as Equation (8):

[0024] (8)

[0025] Among them, c b ρ is the specific heat capacity of the bearing substrate material. b k is the material density of the bearing substrate. b Z is the thermal conductivity coefficient of the bearing substrate. b These are the spatial coordinates of the bearing substrate.

[0026] Optionally, the expression for the oil film thickness h in step S201 is formula (2):

[0027] (2)

[0028] Where c is the relative clearance of the bearing bush, e is the eccentricity of the bearing bush, and ε is the eccentricity of the bearing bush.

[0029] Optionally, the dynamic viscosity η of the lubricating oil in S202 varies with temperature and pressure as shown in formula (3):

[0030] (3)

[0031] η0 is the viscosity value of the lubricating oil at temperature T0, αl β is the viscosity-temperature index of the lubricating oil film. l T0 is the viscosity-pressure index of the lubricating oil film, and T0 is the initial temperature.

[0032] The relationship between the density ρ of the lubricating oil in S202 and temperature and pressure is given by formula (4):

[0033] (4)

[0034] Among them, C 1= 0.6×10 -9 Pa -1 C2 = 1.7 × 10 -9 Pa -1 C3 = 0.00065K -1 ρ0 is the density of the lubricating oil at temperature T0, and T0 is the initial temperature of the lubricating oil film.

[0035] Optionally, the bearing thermo-elasto-hydrodynamic lubrication model based on the coupled surface coating layer and the coupled iterative calculation in S3, to obtain the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution, includes:

[0036] S301. The expression for oil film thickness h, the relationship between the dynamic viscosity η of lubricating oil and temperature and pressure, and the relationship between the density ρ of lubricating oil and temperature and pressure are incorporated into the average Reynolds control equation of the bearing lubricating oil film to obtain the distribution of oil film pressure p and oil film thickness h, and at the same time, the density ρ and viscosity η of lubricating oil at the current temperature are solved.

[0037] S302. Based on the oil film thickness h, the rough peak contact pressure P is obtained. asp The expression is formula (5):

[0038] (5)

[0039] α is the density of roughness peaks on the contact surface, β is the radius of curvature of the roughness peaks, and E is the equivalent elastic modulus. Let be the probability distribution function of the roughness height;

[0040] S303. Based on the obtained oil film pressure p, lubricating oil density ρ and viscosity η, solve the oil film energy equation and the bearing coating heat conduction equation to obtain the oil film temperature T, and determine whether the temperature field calculation meets the convergence condition.

[0041] If not satisfied, adjust the value of the eccentricity e in formula (2) according to the secant method and return to S301;

[0042] If satisfied, the output will show convergent oil film pressure distribution, oil film thickness distribution, rough peak contact pressure, and temperature field distribution.

[0043] Optionally, in S4, the convergent oil film pressure distribution, rough peak contact pressure, and temperature field distribution at the bearing lubrication interface are combined with integral calculations to obtain the total bearing capacity of the bearing considering the influence of the surface coating layer, including:

[0044] S401. Define oil film bearing capacity based on circumferential oil film bearing capacity and axial oil film bearing capacity;

[0045] S402, Based on rough peak contact pressure P asp The circumferential rough peak contact bearing capacity and the axial rough peak contact bearing capacity are obtained, and the rough peak contact bearing capacity is obtained by combining them.

[0046] S403. Based on the oil film bearing capacity and the rough peak contact bearing capacity, the total bearing capacity of the bearing bush thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

[0047] Optionally, in S401, the oil film bearing capacity is defined based on the circumferential oil film bearing capacity and the axial oil film bearing capacity, including:

[0048] Integrating the oil film pressure p along the circumferential direction φ and the axial direction y yields the oil film bearing capacity F. o The formula for the oil film bearing capacity is formula (9):

[0049] (9)

[0050] Where F0 is the oil film bearing capacity, F 0x For the circumferential oil film bearing capacity, F 0y This refers to the axial oil film bearing capacity.

[0051] in, l is the width of the bearing bush; r is the radius of the bearing bush; θ=x is the axial coordinate of the bearing bush.

[0052] in, .

[0053] Optionally, the rough peak contact pressure P in S402 asp The circumferential roughness peak contact bearing capacity and the axial roughness peak contact bearing capacity are obtained. The combined roughness peak contact bearing capacity includes:

[0054] Rough peak contact bearing capacity F s The formula is formula (10):

[0055] (10)

[0056] Among them, F sxFor the circumferential rough peak contact bearing capacity, F sy This refers to the axial roughness peak contact bearing capacity.

[0057] in, , .

[0058] Optionally, the formula for the total bearing capacity F of the bearing bush under the influence of the surface coating layer is formula (11):

[0059] ;(11)

[0060] The above technical solution has at least the following advantages compared with the existing technology:

[0061] This invention provides a method for calculating the bearing capacity under thermo-elasto-fluidic lubrication considering surface coatings. It takes into account the roughness of the journal-bearing contact surface, the coupling effect of the coating layer and the lubricating oil film, and overcomes the limitations of existing finite element virtual simulation and the complexity of experimental measurement methods. This invention provides accurate calculation results for the bearing capacity under thermo-elasto-fluidic lubrication, providing a foundation for assessing the health status of diesel engine main bearings. This invention can accurately evaluate the lubrication load-bearing performance of bearings with surface coatings under various operating conditions, and has good applicability in bearing structure design and performance evaluation applications. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of the calculation method provided in an embodiment of the present invention;

[0064] Figure 2 This is a schematic diagram of the bearing-journal contact surface structure provided in an embodiment of the present invention;

[0065] Figure 3 A schematic diagram of the heat conduction of the bearing considering the surface coating layer is provided for an embodiment of the present invention;

[0066] Figure 4 The diagram shows the load-bearing capacity calculation results of bearing bushes with different coating materials based on the calculations of the present invention, provided for embodiments of the present invention. Detailed Implementation

[0067] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0068] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” or “including,” and similar terms mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or “connected,” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0069] To address the limitations of existing finite element virtual simulation methods, such as insufficient versatility, inability to account for rough morphology of the journal-bearing contact surface, the coupling effect of surface coatings and lubricating oil, and the complexity of experimental measurement methods, this embodiment provides a method for calculating the bearing capacity under thermo-elastohydrodynamic lubrication of bearings that considers surface coatings. This method can accurately calculate the bearing capacity of coated bearings under thermo-elastohydrodynamic lubrication. Details are as follows:

[0070] A method for calculating the bearing capacity of a bearing considering a surface coating layer's thermo-elastohydrodynamic lubrication includes:

[0071] S1. Obtain the structural parameters, basic operating condition parameters, and physical property parameters of the surface coating of the bearing-journal system to obtain the parameter set;

[0072] S2. Based on the parameter set, construct a bearing thermo-elasto-hydrodynamic lubrication model with coupled surface coating layer;

[0073] S3. Based on the bearing thermo-elasto-hydrodynamic lubrication model of the coupled surface coating layer and coupled iterative calculation, the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution are obtained.

[0074] S4. Based on the convergent oil film pressure distribution, rough peak contact pressure and temperature field distribution of the bearing lubrication interface, and combined with integral calculation, the total bearing capacity of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

[0075] In one specific implementation, S1, the structural parameters, basic operating condition parameters, and physical property parameters of the surface coating layer of the bearing-journal system are obtained to get a parameter set, which specifically includes:

[0076] Obtain the structural parameters, basic operating parameters, and physical property parameters of the surface coating of the bearing-journal system; obtain the initial oil film thickness, pressure, and initial temperature values.

[0077] The parameter set includes: initial oil film thickness, initial pressure, and initial temperature.

[0078] In one specific implementation, S2, based on the parameter set, a bearing thermo-elasto-fluidodynamic lubrication model with coupled surface coating is constructed. The main principle of this step is to construct a bearing thermo-elasto-fluidodynamic lubrication model with coupled surface coating. The model includes the Reynolds equation, film thickness equation, rough peak contact pressure equation, energy equation, lubricating oil viscosity-pressure-viscosity-temperature equation, dense pressure-dense temperature equation, and solid heat conduction equation considering the coating. Specifically, it includes:

[0079] S201. Based on the basic parameters obtained in step S1, considering that after processing the coating, the contact interface between the bearing bush and the shaft has the characteristics of a rough surface, the coating layer, and the lubricating oil film working together, the interface operates in a mixed lubrication state at this time, such as... Figure 2 As shown. The average Reynolds control equation for the bearing lubricating oil film is defined as formula (1):

[0080] (1)

[0081] Where p is the lubricating oil film pressure, η is the dynamic viscosity of the lubricating oil film, ρ is the density of the lubricating oil film, h is the thickness of the lubricating oil film, and φ is the density of the lubricating oil film. x φ is the bearing circumferential pressure flow coefficient. y σ is the axial pressure flow coefficient of the bearing, φ is the surface roughness, and φ is the bearing axial pressure flow coefficient. s φ is the shear coefficient of the lubricating oil film. c U is the lubricating oil film contact coefficient, and U is the journal speed.

[0082] The expression for the oil film thickness h is given by formula (2):

[0083] (2)

[0084] Where c is the relative clearance of the bearing bush, e is the eccentricity of the bearing bush, and ε is the eccentricity of the bearing bush.

[0085] S202. Introducing temperature changes, the relationships between the dynamic viscosity η of the lubricating oil and temperature and pressure, and the relationship between the density ρ of the lubricating oil and temperature and pressure are obtained respectively.

[0086] The relationship between the dynamic viscosity η of lubricating oil and temperature and pressure is given by formula (3):

[0087] (3)

[0088] η0 is the viscosity of the lubricating oil film at temperature T0, α l β is the viscosity-temperature index of the lubricating oil film. l T0 is the viscosity-pressure index of the lubricating oil film, and T0 is the initial temperature.

[0089] The relationship between the density ρ of lubricating oil and temperature and pressure is given by formula (4):

[0090] (4)

[0091] Among them, C 1= 0.6×10 -9 Pa -1 C2 = 1.7 × 10 -9 Pa -1 C3 = 0.00065K -1 ρ0 is the density of the lubricating oil at temperature T0, and T0 is the initial temperature of the lubricating oil film.

[0092] S203. When considering the bearing surface coating, a temperature field needs to be introduced to couple the journal, oil film, coating, and substrate into a whole, such as... Figure 3 As shown. The temperature rise of the oil film and the resulting heat change are conducted between the bearing coatings. Therefore, the temperature of the oil film must first be calculated to obtain the energy equation of the lubricating oil film, which is formula (6):

[0093] (6)

[0094] Among them, c p Φ is the specific heat at constant pressure, k is the thermal conductivity, u is the circumferential velocity of the lubricating oil film, v is the axial velocity of the lubricating oil film, Φ is the heat dissipation work, and T is the current temperature of the lubricating oil film.

[0095] S204. The coating layer on the bearing surface is in direct contact with the oil film and conducts heat. The heat conduction equation of the coating is defined as formula (7):

[0096] (7)

[0097] Among them, c c ρ is the specific heat capacity of the coating material. c k is the density of the coating material. c Z is the thermal conductivity coefficient of the coating material. c The spatial coordinates of the coating;

[0098] S205. Define the heat conduction equation of the bearing substrate as Equation (8):

[0099] (8)

[0100] Among them, c b ρ is the specific heat capacity of the bearing substrate material. b k is the material density of the bearing substrate. b Z is the thermal conductivity coefficient of the bearing substrate. b These are the spatial coordinates of the bearing substrate.

[0101] In one specific implementation, S3, based on the bearing thermo-elasto-fluidic lubrication model of the coupled surface coating layer and coupled iterative calculation, obtains the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure, and temperature field distribution, including:

[0102] S301. The expression for oil film thickness h, the relationship between the dynamic viscosity η of lubricating oil and temperature and pressure, and the relationship between the density ρ of lubricating oil and temperature and pressure are incorporated into the average Reynolds control equation of the bearing lubricating oil film to obtain the distribution of oil film pressure p and oil film thickness h, and at the same time, the density ρ and viscosity η of lubricating oil at the current temperature are solved.

[0103] The specific principle of this step is as follows: Substitute equations (2)-(4) into equation (1), use the finite difference method to perform numerical iterative calculation, divide the bearing oil film into multiple uniform grids, each point in the grid represents the pressure value at that point, approximate the derivative in the Reynolds equation by the pressure value difference quotient of each node, iteratively solve the pressure of each node according to the set pressure boundary conditions, obtain the oil film pressure p and oil film thickness h distribution, and at the same time solve the density ρ and viscosity η of the lubricating oil at the current temperature.

[0104] S302. Based on the oil film thickness h, the rough peak contact pressure P is obtained. asp The expression is formula (5):

[0105] (5)

[0106] α is the density of roughness peaks on the contact surface, β is the radius of curvature of the roughness peaks, and E is the equivalent elastic modulus. Let be the probability distribution function of the roughness height;

[0107] S303. Based on the obtained oil film pressure p, lubricating oil density ρ and viscosity η, solve the oil film energy equation and the bearing coating heat conduction equation to obtain the oil film temperature T, and determine whether the temperature field calculation meets the convergence condition.

[0108] If not satisfied, adjust the value of the eccentricity e in formula (2) according to the secant method and return to S301;

[0109] If satisfied, the output will show convergent oil film pressure distribution, oil film thickness distribution, rough peak contact pressure, and temperature field distribution.

[0110] The specific principle of this step is as follows: Based on the oil film pressure p, lubricating oil density ρ, and viscosity η obtained in S01, solve the oil film energy equation and the bearing coating heat conduction equation simultaneously using equations (6) and (8) to obtain the oil film temperature T. Determine whether the temperature field calculation meets the convergence condition. If it does not meet the condition, repeat step S301. Finally, obtain the converged oil film pressure distribution, oil film thickness distribution, rough peak contact pressure, and temperature field distribution.

[0111] In one specific implementation, S4, based on the convergent oil film pressure distribution at the bearing lubrication interface, the rough peak contact pressure and temperature field distribution, and combined with integral calculations, the total bearing capacity of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained, including:

[0112] S401. Define oil film bearing capacity based on circumferential oil film bearing capacity and axial oil film bearing capacity;

[0113] Integrating the oil film pressure p along the circumferential direction φ and the axial direction y yields the oil film bearing capacity F. o The formula for the oil film bearing capacity is formula (9):

[0114] (9)

[0115] Where F0 is the oil film bearing capacity, F 0x For the circumferential oil film bearing capacity, F 0y This refers to the axial oil film bearing capacity.

[0116] in, l is the width of the bearing bush; r is the radius of the bearing bush; θ=x is the axial coordinate of the bearing bush.

[0117] in, .

[0118] The principle of this step is as follows: considering the coupling effect of the rough surface morphology of the bearing bush and the lubricating oil, the bearing capacity of the bearing bush consists of two parts: the oil film bearing capacity and the rough peak contact bearing capacity. According to step S201, solving equation (1) yields the oil film pressure p. Integrating the oil film pressure p along the circumferential φ and axial y directions yields the oil film bearing capacity F. o ,

[0119] S402, Based on rough peak contact pressure P asp The circumferential rough peak contact bearing capacity and the axial rough peak contact bearing capacity are obtained, and the rough peak contact bearing capacity is obtained by combining them.

[0120] Rough peak contact bearing capacity F s The formula is formula (10):

[0121] (10)

[0122] Among them, F sx For the circumferential rough peak contact bearing capacity, F sy This refers to the axial roughness peak contact bearing capacity.

[0123] in, , .

[0124] The specific principle of this step is as follows: According to the above formula (5), the rough peak contact pressure p can be obtained. asp The rough peak contact pressure p asp The rough peak contact bearing capacity F can be obtained by integrating along the circumferential and axial directions. s .

[0125] S402. Based on the oil film bearing capacity and the rough peak contact bearing capacity, the total bearing capacity of the bearing bush thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

[0126] S403. Based on the oil film bearing capacity and the rough peak contact bearing capacity, the total bearing capacity of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained. The formula for the total bearing capacity F of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is formula (11):

[0127] ;(11)

[0128] Figure 4 The statistical results of bearing capacity are presented, including liquid bearing capacity, solid bearing capacity, total bearing capacity, and the ratio of liquid to solid bearing capacity.

[0129] This invention obtains the basic parameters of the diesel engine main bearing bush-journal and surface coating layer, as well as the initialized oil film pressure, thickness, and temperature; constructs a thermo-elasto-fluidic lubrication analysis model of the bearing bush considering the surface coating layer; derives the oil film pressure distribution, rough peak contact pressure distribution, and temperature field distribution based on the thermo-elasto-fluidic lubrication analysis model of the bearing bush considering the surface coating layer; and calculates the liquid and solid bearing capacities of the bearing bush under specific working conditions based on the bearing bush thermo-elasto-fluidic lubrication model considering the surface coating layer and the obtained three-dimensional oil film pressure field and rough peak contact pressure field, thereby obtaining the total bearing capacity. The bearing bush thermo-elasto-fluidic lubrication bearing capacity calculation method considering the surface coating layer provided by this invention takes into account the rough morphology of the journal-bearing bush contact surface, the coupling effect of the coating layer and the lubricating oil film, and solves the limitations of existing finite element virtual simulation and the complexity of experimental measurement methods. This invention provides accurate bearing capacity calculation results under thermo-elasto-fluidic lubrication of the bearing bush, providing a foundation for the health status assessment of diesel engine main bearing bushes. This invention can accurately evaluate the lubrication bearing performance of bearing bushes with surface coating layers under various working conditions and has good applicability in bearing bush structure design and performance evaluation application scenarios.

[0130] The following points need to be explained:

[0131] (1) The accompanying drawings of the embodiments of the present invention only involve the structures involved in the embodiments of the present invention. Other structures can refer to the general design.

[0132] (2) For clarity, the thickness of layers or regions is enlarged or reduced in the drawings used to describe embodiments of the invention, i.e., these drawings are not drawn to scale. It is understood that when an element such as a layer, film, region or substrate is referred to as being “above” or “below” another element, the element may be “directly” located “above” or “below” the other element or there may be intermediate elements.

[0133] (3) Where there is no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0134] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the bearing capacity of a bearing considering a surface coating layer's thermo-elastohydrodynamic lubrication, characterized in that, include: S1. Obtain the structural parameters, basic operating condition parameters, and physical property parameters of the surface coating of the bearing-journal system to obtain the parameter set; S2. Based on the parameter set, construct a bearing thermo-elasto-hydrodynamic lubrication model with coupled surface coating layer; S3. Based on the bearing thermo-elasto-hydrodynamic lubrication model of the coupled surface coating layer and coupled iterative calculation, the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution are obtained. S4. Based on the convergent oil film pressure distribution, rough peak contact pressure and temperature field distribution of the bearing lubrication interface, and combined with integral calculation, the total bearing capacity of the bearing thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

2. The method for calculating the bearing capacity of a bearing considering surface coating as described in claim 1, characterized in that, The parameter set in S1 includes: initial oil film thickness, initial pressure, and initial temperature.

3. The method for calculating the bearing capacity of a bearing considering surface coating as described in claim 2, characterized in that, The S2 section, which constructs a bearing thermo-elasto-hydro-lubricating model for coupling surface coating based on the parameter set, includes: S201. Define the average Reynolds control equation for the bearing lubricating oil film. The average Reynolds control equation for the bearing lubricating oil film is Equation (1): ；（1） Where p is the lubricating oil film pressure, η is the dynamic viscosity of the lubricating oil film, ρ is the density of the lubricating oil film, h is the thickness of the lubricating oil film, and φ is the density of the lubricating oil film. x φ is the bearing circumferential pressure flow coefficient. y σ is the axial pressure flow coefficient of the bearing, σ is the surface roughness of the lubricating oil film, and φ is the bearing axial pressure flow coefficient. s φ is the shear coefficient of the lubricating oil film. c U is the contact coefficient of the lubricating oil film, U is the journal speed, and x is the circumferential coordinate of the bearing bush. S202. Introducing temperature changes, the relationships between the dynamic viscosity η of the lubricating oil and temperature and pressure, and the relationship between the density ρ of the lubricating oil and temperature and pressure are obtained respectively. S203. When considering the coating layer on the bearing surface, a temperature field is introduced to obtain the energy equation of the lubricating oil film, which is formula (6): ；（6） Among them, c p denoted as the specific heat at constant pressure of the lubricating oil film, k as the thermal conductivity of the lubricating oil film, u as the circumferential velocity of the lubricating oil film, v as the axial velocity of the lubricating oil film, Φ as the heat dissipation work of the lubricating oil film, and T as the current temperature of the lubricating oil film. S204. The coating layer on the bearing surface is in direct contact with the oil film and conducts heat. The heat conduction equation of the coating is defined as formula (7): ；（7） Among them, c c ρ is the specific heat capacity of the coating material. c k is the density of the coating material. c Z is the thermal conductivity coefficient of the coating material. c The spatial coordinates of the coating; S205. Define the heat conduction equation of the bearing substrate as Equation (8): ；（8） Among them, c b ρ is the specific heat capacity of the bearing substrate material. b k is the material density of the bearing substrate. b Z is the thermal conductivity coefficient of the bearing substrate. b These are the spatial coordinates of the bearing substrate.

4. The method for calculating the bearing capacity of a bearing considering surface coating as described in claim 3, characterized in that, The expression for the oil film thickness h in step S201 is formula (2): ；（2） Where c is the relative clearance of the bearing bush, e is the eccentricity of the bearing bush, and ε is the eccentricity of the bearing bush.

5. The method for calculating the bearing capacity of a bearing considering surface coating as described in claim 4, characterized in that, The relationship between the dynamic viscosity η of the lubricating oil in S202 and temperature and pressure is given by formula (3): ； （3） η0 is the viscosity value of the lubricating oil at temperature T0, α l β is the viscosity-temperature index of the lubricating oil film. l T0 is the viscosity-pressure index of the lubricating oil film, and T0 is the initial temperature. The relationship between the density ρ of the lubricating oil in S202 and temperature and pressure is given by formula (4): ；（4） Among them, C 1= 0.6×10 -9 Pa -1 C2 = 1.7 × 10 -9 Pa -1 C3 = 0.00065K -1 ρ0 is the density of the lubricating oil at temperature T0, and T0 is the initial temperature of the lubricating oil film.

6. The method for calculating the bearing capacity of a bearing considering a surface coating layer according to claim 5, characterized in that, The bearing thermo-elasto-hydrodynamic lubrication model based on the coupled surface coating layer and the coupled iterative calculation in S3 yield the converged bearing lubrication interface oil film pressure distribution, rough peak contact pressure, and temperature field distribution, including: S301. The expression for oil film thickness h, the relationship between the dynamic viscosity η of lubricating oil and temperature and pressure, and the relationship between the density ρ of lubricating oil and temperature and pressure are incorporated into the average Reynolds control equation of the bearing lubricating oil film to obtain the distribution of oil film pressure p and oil film thickness h, and at the same time, the density ρ and viscosity η of lubricating oil at the current temperature are solved. S302. Based on the oil film thickness h, the rough peak contact pressure P is obtained. asp The expression is formula (5): ；（5） α is the density of roughness peaks on the contact surface, β is the radius of curvature of the roughness peaks, and E is the equivalent elastic modulus. Let be the probability distribution function of the roughness height; S303. Based on the obtained oil film pressure p, lubricating oil density ρ and viscosity η, solve the oil film energy equation and the bearing coating heat conduction equation to obtain the oil film temperature T, and determine whether the temperature field calculation meets the convergence condition. If not satisfied, adjust the value of the eccentricity e in formula (2) according to the secant method and return to S301; If satisfied, the output will show convergent oil film pressure distribution, oil film thickness distribution, rough peak contact pressure, and temperature field distribution.

7. The method for calculating the bearing capacity of a bearing considering surface coating as described in claim 6, characterized in that, The convergent bearing lubrication interface oil film pressure distribution, rough peak contact pressure and temperature field distribution in S4, combined with integral calculations, yield the total bearing capacity of the bearing considering the influence of the surface coating layer, including: S401. Define oil film bearing capacity based on circumferential oil film bearing capacity and axial oil film bearing capacity; S402, Based on rough peak contact pressure P asp The circumferential rough peak contact bearing capacity and the axial rough peak contact bearing capacity are obtained, and the rough peak contact bearing capacity is obtained by combining them. S403. Based on the oil film bearing capacity and the rough peak contact bearing capacity, the total bearing capacity of the bearing bush thermo-elastohydrodynamic lubrication considering the influence of the surface coating layer is obtained.

8. The method for calculating the bearing capacity considering the surface coating layer of a bearing bush in accordance with claim 7, characterized in that, In S401, based on the circumferential oil film bearing capacity and the axial oil film bearing capacity, the oil film bearing capacity is defined as including: Integrating the oil film pressure p along the circumferential direction φ and the axial direction y yields the oil film bearing capacity F. o The formula for the oil film bearing capacity is formula (9): ；（9） Where F0 is the oil film bearing capacity, F 0x For the circumferential oil film bearing capacity, F 0y This refers to the axial oil film bearing capacity. in, l is the width of the bearing bush; r is the radius of the bearing bush; θ=x is the axial coordinate of the bearing bush. in, .

9. The method for calculating the bearing capacity of a bearing considering a surface coating layer according to claim 8, characterized in that, The rough peak contact pressure P in S402 asp The circumferential roughness peak contact bearing capacity and the axial roughness peak contact bearing capacity are obtained. The combined roughness peak contact bearing capacity includes: Rough peak contact bearing capacity F s The formula is formula (10): ；（10） Among them, F sx For the circumferential rough peak contact bearing capacity, F sy This refers to the axial roughness peak contact bearing capacity. in, , .

10. The method for calculating the bearing capacity of a bearing considering a surface coating layer according to claim 9, characterized in that, The formula for the total bearing capacity F of the bearing bush under the influence of the surface coating layer is formula (11): ；（11）。

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