Friction dynamics analysis method for herringbone micro-groove sliding bearing in starting stage

Abstract

The invention provides a herringbone micro-groove sliding bearing starting stage friction dynamics analysis method. The herringbone micro-groove sliding bearing starting stage friction dynamics analysis method comprises the following steps that bearing initial parameters are input; steady-state input: giving a static load, and determining a balance position; transient input: giving the range of a starting model, starting time, rotor unbalance mass and external impact load; calculating a transient film thickness: calculating a film thickness variation caused by a bearing time-varying gap and a film thickness variation caused by a bearing surface micro-groove; and calculating transient fluid pressure, transient cavitation fraction and transient contact pressure. The method has the beneficial effects that the transient friction dynamic model in the starting stage of the micro-groove sliding bearing is established, so that the friction dynamic behavior calculation is more accurate, and the problems of insufficient precision and high friction work of the transient friction dynamic model are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of friction dynamics of rotating machinery, and in particular relates to a friction dynamics analysis method for a herringbone micro-groove sliding bearing in the starting stage. Background Art

[0002] The starting performance of sliding bearings is generally evaluated based on starting torque, takeoff speed, and takeoff time. In the stationary state, the bearing system relies on metal-to-metal contact for support. As the rotor speed increases, the hydrodynamic pressure effect in the bearing gap increases. Once sufficient rotational torque is achieved to overcome static friction, the bearing is driven. The performance of the bearing system during the starting phase can be divided into three regimes: boundary lubrication, mixed lubrication, and fluid lubrication. Under the boundary lubrication regime, the increase in fluid film thickness in the bearing gap is minimal, and the asperity contact force between the friction pair surfaces is the primary supporting force, making the bearing most likely to experience fatigue wear. Under the mixed lubrication regime, the hydrodynamic pressure effect increases with increasing fluid film thickness, and the fluid and contact forces jointly resist the external load, resulting in reduced wear behavior. Under the fluid lubrication regime, asperity contact between the friction pair surfaces almost disappears, and the fluid force in the bearing gap becomes the primary supporting force, minimizing the likelihood of bearing fatigue wear. Therefore, studying the tribodynamic performance of sliding bearings during the starting phase and exploring effective friction reduction methods are crucial for the safe operation and longevity of bearing systems.

[0003] Research on the performance of textured surface bearings has demonstrated that surface texturing with appropriate parameters can positively impact the friction and lubrication properties of bearings. The most significant advantage of this method is that it does not require significant changes to the original bearing system structure. By laser engraving the friction pair surface to create a microtexture with a specific shape, and utilizing the resulting microdynamic pressure effects, micro-oil storage effects, and abrasive particle capture effects, the tribological performance of the bearing during operation is significantly improved. Therefore, surface texturing provides a new approach for improving the tribological performance of the main bearing during crankshaft starting.

[0004] Currently, some authorized and published patents have investigated the tribological properties of micro-grooved sliding bearings. However, a technical solution for establishing a more accurate transient friction dynamics model of micro-grooved sliding bearings during the startup phase by combining the rotor starting equations with the rotor dynamics equations and incorporating the influence of rotor unbalance mass and external shock loads is unclear. Furthermore, improving the load-bearing capacity and reducing the friction coefficient remain pressing challenges for sliding bearings during operation. Therefore, providing theoretical guidance for the accurate prediction and effective evaluation of bearing lubrication performance during the startup phase is crucial for improving the reliability and durability of mechanical systems. Summary of the Invention

[0005] In view of this, the present invention aims to propose a friction dynamics analysis method for a herringbone micro-groove sliding bearing during the starting phase, so as to solve the problems of insufficient accuracy and high friction work of the transient friction dynamics model.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A friction dynamics analysis method for a herringbone micro-groove sliding bearing during the starting phase comprises the following steps:

[0008] S1. Input the initial parameters of the bearing;

[0009] S2, Steady-state input: Given a static load, determine the equilibrium position;

[0010] S3, transient input: given starting model, starting time, rotor unbalance mass and external shock load range;

[0011] S4. Calculate transient film thickness: Calculate the film thickness variation caused by the time-varying bearing clearance and the film thickness variation caused by micro-grooves on the bearing surface;

[0012] S5. Calculate the transient fluid pressure, transient cavitation fraction, and transient contact pressure: First, discretize the pressure equation using the finite difference method, then accelerate the numerical solution using the super-relaxation method to determine whether the convergence criterion is met. If so, obtain the transient fluid pressure, transient cavitation fraction, and transient contact pressure. Otherwise, continue the iterative calculation.

[0013] S6. Use the Newmark method to solve the rotor motion equation to determine whether the starting time is completed. If so, output the bearing performance parameters, which include the maximum fluid pressure, maximum contact pressure, fluid force, contact force, minimum film thickness, contact loss, and the change curve of the axis trajectory. Otherwise, update the journal center position and return to step S4.

[0014] Furthermore, in step S3, the transient input includes:

[0015] The acceleration conditions during the bearing startup phase directly determine the transition of the lubrication mechanism and the takeoff speed. The expressions for the transient rotor angular displacement, angular velocity, and angular acceleration are as follows:

[0016]

[0017] Where θ s Expressed as the angular displacement of the rotor, ω s Expressed as the angular velocity of the rotor, α s Expressed as the angular acceleration of the rotor;

[0018] The expressions of the five acceleration models are as follows:

[0019] The expression of the linear acceleration model is as follows:

[0020] u max t / t a ,0≤t≤t a ;

[0021] The expression of the cosine acceleration model is as follows:

[0022] u max (1-cos(πt / 2t a )),0≤t≤t a ;

[0023] The expression of the sin-type acceleration model is as follows:

[0024] u max sin(πt / 2t a ),0≤t≤t a ;

[0025] The expression of the S-type acceleration model is as follows:

[0026]

[0027] The expression of the anti-S-shaped acceleration model is as follows:

[0028]

[0029] Where u max and α max Expressed as the maximum value of linear velocity and angular acceleration, t a Expressed as acceleration time;

[0030] The rotor unbalance mass includes horizontal and vertical components, and its expression is as follows:

[0031]

[0032] Where m ub and e b They are expressed as unbalanced mass and unbalanced eccentricity respectively;

[0033] The external impact load includes horizontal and vertical components, which are expressed as follows:

[0034]

[0035] Where A im , and t im are respectively represented as the amplitude, phase and entry time of the impact load.

[0036] Furthermore, in step S4, the transient film thickness is calculated, including:

[0037] The fluid film thickness distribution of the bearing during the starting phase is affected by the time-varying gap and micro-grooves. The local film thickness equation of the lubricating medium is expressed as follows:

[0038] h T =h+δ b +δ j ;

[0039] Where, δ b and δ j They are respectively expressed as the roughness height of the friction pair of the bearing and the journal;

[0040] The nominal film thickness equation of the lubricating medium is expressed as follows:

[0041]

[0042] Where c is the bearing clearance, e is x and e y They are respectively expressed as bearing eccentricity components, is the circumferential coordinate, h g The film thickness variation caused by the micro grooves on the bearing surface;

[0043] The geometric expression of the herringbone micro groove is as follows:

[0044]

[0045] Where c x , c z ,c g and ψ are the length, width, depth and deflection angle of the herringbone microgrooves, respectively.

[0046] Furthermore, in step S5, the transient fluid pressure, transient cavitation fraction, and transient contact pressure are calculated, including:

[0047] The main supporting force of the bearing is generated by the fluid dynamic pressure effect. The expression of the fluid pressure equation of the lubricating medium is as follows:

[0048]

[0049] Where μ and ρ represent the viscosity and density of the fluid respectively, u represents the rotation speed of the shaft, and t represents time;

[0050] The free equations for the local volume flow rate of the control volume in the horizontal and vertical directions are expressed as follows:

[0051]

[0052] Where, v x and v z are the average velocities of the control volume;

[0053] The expression of the mean flow equation is as follows:

[0054]

[0055] Where Δx and Δz represent the length of the control volume, respectively;

[0056] By introducing the pressure flow factor φ x and φ z , shear flow factor φ s , contact factor φ c , the mean flow equation considering the rough surface is expressed as follows:

[0057]

[0058] Where, and σ represent the average pressure and composite roughness, respectively;

[0059] The flow balance equation is expressed as follows:

[0060]

[0061] The expression of the mean flow equation considering the rough surface is as follows:

[0062]

[0063]

[0064] The expression of the transient average Reynolds equation considering the mass conservation cavitation effect is as follows:

[0065]

[0066]

[0067] Where p cav Expressed as cavitation pressure;

[0068] The fluid pressure and cavitation fraction are calculated using the Gauss-Seidel iterative method; the convergence of the numerical solution is accelerated by the super-relaxation method, which is expressed as follows:

[0069]

[0070] Where, Expressed as the initial values ​​of the fluid pressure and cavitation fraction, the updated expressions are as follows:

[0071]

[0072] Where, ω P and ω Θ Expressed as super-relaxation factor;

[0073] The expressions for the convergence criteria of fluid pressure and cavitation fraction are as follows:

[0074]

[0075] Where, ζ p and ζ Θ are respectively expressed as the convergence tolerance of fluid pressure and cavitation fraction;

[0076] The expression of the asperity contact model is as follows:

[0077]

[0078] Where,

[0079] Where,

[0080] Furthermore, in step S6, the bearing performance parameters are output, including:

[0081] According to Newton's second law, the force balance equation considering the rotor unbalance mass and external impact load is expressed as follows:

[0082]

[0083] Where W ex and W ey They are expressed as external load components, Q ubx and Q uby They are respectively expressed as unbalanced force components, Q ex and Q ey They are respectively expressed as impact load components, W hx and W hy They are respectively represented as fluid force components, W ax and W ay They are expressed as contact force components, F fx and F fy Expressed as friction force components, m j Expressed as shaft mass;

[0084] The force balance equation is calculated based on the Newmark method, and its expression is as follows:

[0085]

[0086]

[0087] Where x and y are displacement components, x′ and y′ are velocity components, x″ and y″ are acceleration components, Δt is the time step, and α is the time step. t and β t are expressed as constants of 0.5 and 0.25, respectively;

[0088] The expression of the transient fluid force is as follows:

[0089]

[0090] The expression of the transient contact force is as follows:

[0091]

[0092] The expression of transient friction force is as follows:

[0093]

[0094] Where μ r Expressed as the dry friction coefficient, φ fp ,φ f and φ fs The expressions for shear stress factor, transient friction coefficient and contact loss are as follows:

[0095]

[0096]

[0097] Furthermore, in step S1, the initial bearing parameters are input, including:

[0098] The initial parameters of the bearing are as follows:

[0099] Bearing length, journal radius, bearing clearance, fluid viscosity, rotor mass, elastic model of bearing and its Poisson's ratio, elastic model of journal and its Poisson's ratio, roughness parameters of bearing and roughness parameters of journal.

[0100] Compared with the prior art, the friction dynamics analysis method of the herringbone micro-groove sliding bearing in the starting stage described in the present invention has the following beneficial effects:

[0101] (1) The herringbone micro-grooves arranged on the inner surface of the bearing are designed with optimal parameters through structural optimization;

[0102] (2) Using the finite difference method to discretize the pressure equation;

[0103] (3) In order to improve computational efficiency, the super-relaxation method is used to accelerate iteration in the early numerical solution process. The rotor starting equation and the rotor dynamics equation are combined based on the Newmark method, and the influencing factors of rotor unbalance mass and external impact load are embedded.

[0104] (4) A transient friction dynamics model of the micro-groove sliding bearing in the starting stage is established to make the calculation of friction dynamics behavior more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0106] Figure 1 This is a global schematic diagram of the starting stage of the herringbone micro-groove sliding bearing according to an embodiment of the present invention;

[0107] Figure 2 This is a front view schematic diagram of the herringbone micro-groove sliding bearing in the starting stage according to an embodiment of the present invention;

[0108] Figure 3 This is a front view schematic diagram of a herringbone micro-groove sliding bearing according to an embodiment of the present invention;

[0109] Figure 4 A schematic side view of a herringbone micro-groove sliding bearing according to an embodiment of the present invention;

[0110] Figure 5 This is a schematic diagram of the herringbone micro-groove sliding bearing according to an embodiment of the present invention;

[0111] Figure 6 A partial schematic diagram of a herringbone micro-groove sliding bearing according to an embodiment of the present invention;

[0112] Figure 7 Schematic diagram of film thickness distribution under different herringbone micro-groove angles according to an embodiment of the present invention;

[0113] Figure 8 Schematic diagram of membrane pressure distribution under different herringbone micro-grooves angles according to an embodiment of the present invention;

[0114] Figure 9 This is a schematic diagram of the friction dynamics calculation process of the herringbone micro-groove sliding bearing in the starting stage according to an embodiment of the present invention;

[0115] Figure 10 Schematic diagram of curves showing changes of maximum fluid pressure and maximum contact pressure over time under different impact load amplitudes according to an embodiment of the present invention;

[0116] Figure 11Schematic diagram of a curve showing the change of bearing friction dynamics performance over time under different impact load amplitudes according to an embodiment of the present invention. DETAILED DESCRIPTION

[0117] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0118] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0119] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0120] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0121] like Figures 1 to 11 As shown, a friction dynamics analysis method for a herringbone micro-groove sliding bearing during the starting phase includes the following steps:

[0122] S1. Input the initial parameters of the bearing;

[0123] S2, Steady-state input: Given a static load, determine the equilibrium position;

[0124] S3, transient input: given starting model, starting time, rotor unbalance mass and external shock load range;

[0125] S4. Calculate transient film thickness: Calculate the film thickness variation caused by the time-varying bearing clearance and the film thickness variation caused by micro-grooves on the bearing surface;

[0126] S5. Calculate the transient fluid pressure, transient cavitation fraction, and transient contact pressure: First, discretize the pressure equation using the finite difference method, then accelerate the numerical solution using the super-relaxation method to determine whether the convergence criterion is met. If so, obtain the transient fluid pressure, transient cavitation fraction, and transient contact pressure. Otherwise, continue the iterative calculation.

[0127] S6. Use the Newmark method to solve the rotor motion equation to determine whether the starting time is completed. If so, output the bearing performance parameters, which include the maximum fluid pressure, maximum contact pressure, fluid force, contact force, minimum film thickness, contact loss, and the change curve of the axis trajectory. Otherwise, update the journal center position and return to step S4.

[0128] The specific implementation is as follows:

[0129] Combined with the input parameters of step S1 and step S2, the acceleration condition of the bearing start-up phase in step S3 directly determines the transition of the lubrication mechanism and the take-off speed, such as Figure 1 As shown in the global diagram of the starting phase of the herringbone micro-groove sliding bearing, the expressions of the transient rotor angular displacement, angular velocity and angular acceleration are as follows:

[0130]

[0131] Among them, θ s Expressed as the angular displacement of the rotor, ω s Expressed as the angular velocity of the rotor, α s Expressed as the angular acceleration of the rotor.

[0132] The rotation speed of the bearing increases gradually during the starting phase, e.g. Figure 2 The front view of the herringbone micro-groove sliding bearing during the starting phase is shown. The five starting models used in this study include: linear model, cosine model, sin model, S-type model, and reverse S-type model. The expression of the model is as follows:

[0133] The linear starting model is expressed as follows:

[0134] u max t / t a ,0≤t≤t a ;

[0135] The expression of the cos type starting model is as follows:

[0136] u max (1-cos(πt / 2t a )),0≤t≤t a ;

[0137] The expression of the sin-type starting model is as follows:

[0138] u max sin(πt / 2t a ),0≤t≤t a ;

[0139] The expression of the S-type starting model is as follows:

[0140]

[0141] The expression of the anti-S-type starting model is as follows:

[0142]

[0143] Among them, u max and α max Expressed as linear velocity and angular acceleration and maximum value, t a Expressed as acceleration time.

[0144] The rotor unbalance mass includes horizontal and vertical components, and its expression is as follows:

[0145]

[0146] Among them, m ub and e b They are expressed as unbalanced mass and unbalanced eccentricity respectively.

[0147] The external impact load includes horizontal and vertical components, which are expressed as follows:

[0148]

[0149] Among them, A im , and t im are respectively represented as the amplitude, phase and entry time of the impact load.

[0150] like Figure 3 and Figure 4 As shown in the front and side views of the herringbone micro-groove sliding bearing, the fluid film thickness distribution of the bearing during the starting phase is affected by the time-varying gap and micro-grooves. The local film thickness equation of the lubricating medium is:

[0151] h T =h+δ b +δ j ;

[0152] Among them, δ b and δ j They are represented as the roughness height of the friction pair of the bearing and the journal respectively.

[0153] The nominal film thickness equation of the lubricating medium is:

[0154]

[0155] Where c is the bearing clearance, e x and e y They are respectively expressed as bearing eccentricity components, is the circumferential coordinate, h g The film thickness variation is caused by the micro grooves on the bearing surface.

[0156] like Figure 5 and Figure 6 As shown in the expanded diagram and partial diagram of the herringbone micro-groove sliding bearing, the geometric expression of the herringbone micro-groove is:

[0157]

[0158] Among them, c x , c z ,c g and ψ are the length, width, depth and deflection angle of the herringbone microgrooves, respectively.

[0159] like Figure 7 and Figure 8 The distribution of film thickness and film pressure at different herringbone microgrooves angles is shown, showing the three-dimensional surface morphology after the herringbone microgrooves are introduced into the bearing surface.

[0160] The main supporting force of the bearing is generated by the fluid dynamic pressure effect. The fluid pressure equation of the lubricating medium is:

[0161]

[0162] Where μ and ρ represent the viscosity and density of the fluid, respectively, u represents the rotation speed of the shaft, and t represents time.

[0163] The free equations for the local volume flow of the control volume in the horizontal and vertical directions are:

[0164]

[0165] Among them, v x and v z are the average velocities of the control volume.

[0166] The expression of the mean flow equation is:

[0167]

[0168] where Δx and Δz are the lengths of the control volume, respectively.

[0169] By introducing the pressure flow factor φx and φ z , shear flow factor φ s , contact factor φ c , the mean flow equation considering the rough surface is expressed as:

[0170]

[0171] in, and σ represent the average pressure and composite roughness, respectively.

[0172] The expression of the flow balance equation is:

[0173]

[0174] The mean flow equation considering the rough surface is expressed as:

[0175]

[0176] In this study, the influence of cavitation effect is considered, so a mass conservation cavitation model needs to be established. When the fluid pressure is greater than the cavitation pressure, the cavitation fraction in the full film region is equal to; when the cavitation fraction is between and, the fluid pressure in the cavitation region is equal to the cavitation pressure.

[0177]

[0178] The transient average Reynolds equation considering the mass conservation cavitation effect is expressed as:

[0179]

[0180]

[0181] Among them, p cav Expressed as cavitation pressure.

[0182] The fluid pressure and cavitation fraction are calculated using the Gauss-Seidel iterative method. To improve computational efficiency, the convergence of the numerical solution is accelerated using the over-relaxation method.

[0183]

[0184] in, Expressed as initial values ​​of the fluid pressure and cavitation fraction, they can be updated using the following expressions:

[0185]

[0186] Among them, ω P and ω Θ Expressed as the super-relaxation factor.

[0187] The convergence criteria for fluid pressure and cavitation fraction are:

[0188]

[0189] Among them, p and ζ Θ are expressed as the convergence tolerance of fluid pressure and cavitation fraction, respectively.

[0190] The expression of the asperity contact model is:

[0191]

[0192] in,

[0193] in,

[0194] like Figure 9 The friction dynamics calculation flow chart of the herringbone micro-groove sliding bearing at the starting stage is shown in the figure. According to Newton's second law, the force balance equation considering the rotor unbalance mass and external impact load can be expressed as follows:

[0195]

[0196] Among them, W ex and W ey They are expressed as external load components, Q ubx and Q uby They are respectively expressed as unbalanced force components, Q ex and Q ey They are respectively expressed as impact load components, W hx and W hy They are respectively represented as fluid force components, W ax and W ay They are expressed as contact force components, F fx and F fy Expressed as friction force components, m j Expressed as shaft mass.

[0197] The force balance equation is calculated based on the Newmark method and is expressed as:

[0198]

[0199]

[0200] Among them, x and y represent the displacement components, x′ and y′ represent the velocity components, x″ and y″ represent the acceleration components, Δt represents the time step, α t and β t The constants are expressed as . and . respectively.

[0201] The transient fluid force can be expressed as:

[0202]

[0203] The transient contact force can be expressed as:

[0204]

[0205] The transient friction force can be expressed as:

[0206]

[0207] Among them, μ r Expressed as the dry friction coefficient, φ fp ,φ f and φ fs are expressed as shear stress factors,

[0208] The transient friction coefficient and contact loss can be calculated as follows:

[0209]

[0210]

[0211] Based on the above solution process, an analysis method for the friction dynamics behavior of micro-groove sliding bearings during the starting phase considering external impact loads and rotor unbalanced mass was obtained.

[0212] like Figure 10 and Figure 11 As shown, the time-varying curves of bearing friction dynamics performance such as maximum fluid pressure, maximum contact pressure, fluid force and contact force, vertical and horizontal friction forces, axis trajectory, and contact loss are displayed under different impact load amplitudes.

[0213] The advantages and beneficial effects of the present invention are as follows:

[0214] (1) The herringbone micro-grooves arranged on the inner surface of the bearing are designed with optimal parameters through structural optimization;

[0215] (2) Using the finite difference method to discretize the pressure equation;

[0216] (3) In order to improve computational efficiency, the super-relaxation method is used to accelerate iteration in the early numerical solution process. The rotor starting equation and the rotor dynamics equation are combined based on the Newmark method, and the influencing factors of rotor unbalance mass and external impact load are embedded.

[0217] (4) A transient friction dynamics model of the micro-groove sliding bearing in the starting stage is established to make the calculation of friction dynamics behavior more accurate.

[0218] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A friction dynamics analysis method for a herringbone micro-groove sliding bearing during the startup phase, characterized by: The following steps are involved: S1. Input the initial parameters of the bearing; S2, Steady-state input: Given a static load, determine the equilibrium position; S3, transient input: given starting model, starting time, rotor unbalance mass and external shock load range; S4. Calculate transient film thickness: Calculate the film thickness variation caused by the time-varying bearing clearance and the film thickness variation caused by micro-grooves on the bearing surface; S5. Calculate the transient fluid pressure, transient cavitation fraction, and transient contact pressure: First, discretize the pressure equation using the finite difference method, then accelerate the numerical solution using the super-relaxation method to determine whether the convergence criterion is met. If so, obtain the transient fluid pressure, transient cavitation fraction, and transient contact pressure. Otherwise, continue the iterative calculation. S6. Use the Newmark method to solve the rotor motion equation to determine whether the starting time is completed. If so, output the bearing performance parameters, which include the maximum fluid pressure, maximum contact pressure, fluid force, contact force, minimum film thickness, contact loss, and the change curve of the axis trajectory. Otherwise, update the journal center position and return to step S4.

2. The friction dynamics analysis method for a herringbone micro-groove sliding bearing during the startup phase according to claim 1, characterized in that: In step S3, transient input includes: The acceleration conditions during the bearing startup phase directly determine the transition of the lubrication mechanism and the takeoff speed. The expressions for the transient rotor angular displacement, angular velocity, and angular acceleration are as follows: Where θ s Expressed as the angular displacement of the rotor, ω s Expressed as the angular velocity of the rotor, α s Expressed as the angular acceleration of the rotor; The expressions of the five acceleration models are as follows: The expression of the linear acceleration model is as follows: u max t / t a ,0≤t≤t a ; The expression of the cosine acceleration model is as follows: u max (1-cos(πt / 2t a )),0≤t≤t a ; The expression of the sin-type acceleration model is as follows: u max sin(πt / 2t a ),0≤t≤t a ; The expression of the S-type acceleration model is as follows: The expression of the anti-S-shaped acceleration model is as follows: Where u max and α max Expressed as the maximum value of linear velocity and angular acceleration, t a Expressed as acceleration time; The rotor unbalance mass includes horizontal and vertical components, and its expression is as follows: Where m ub and e b They are expressed as unbalanced mass and unbalanced eccentricity respectively; The external impact load includes horizontal and vertical components, which are expressed as follows: Where A im , and t im are respectively represented as the amplitude, phase and entry time of the impact load.

3. The friction dynamics analysis method for a herringbone micro-groove sliding bearing during the startup phase according to claim 1, characterized in that: In step S4, the transient film thickness is calculated, including: The fluid film thickness distribution of the bearing during the starting phase is affected by the time-varying gap and micro-grooves. The local film thickness equation of the lubricating medium is expressed as follows: h T =h+δ b +d j ; Where, δ b and δ j They are respectively expressed as the roughness height of the friction pair of the bearing and the journal; The nominal film thickness equation of the lubricating medium is expressed as follows: Where c is the bearing clearance, e is x and e y They are respectively expressed as bearing eccentricity components, is the circumferential coordinate, h g The film thickness variation caused by the micro grooves on the bearing surface; The geometric expression of the herringbone micro groove is as follows: Where c x , c z ,c g and ψ are the length, width, depth and deflection angle of the herringbone microgrooves, respectively.

4. The method for analyzing friction dynamics of a herringbone micro-groove sliding bearing during the startup phase according to claim 1, characterized in that: In step S5, the transient fluid pressure, transient cavitation fraction, and transient contact pressure are calculated, including: The main supporting force of the bearing is generated by the fluid dynamic pressure effect. The expression of the fluid pressure equation of the lubricating medium is as follows: Where μ and ρ represent the viscosity and density of the fluid respectively, u represents the rotation speed of the shaft, and t represents time; The free equations for the local volume flow rate of the control volume in the horizontal and vertical directions are expressed as follows: Where, v x and v z are the average velocities of the control volume; The expression of the mean flow equation is as follows: Where Δx and Δz represent the length of the control volume, respectively; By introducing the pressure flow factor φ x and φ z , shear flow factor φ s , contact factor φ c , the mean flow equation considering the rough surface is expressed as follows: Where, and σ represent the average pressure and composite roughness, respectively; The flow balance equation is expressed as follows: The expression of the mean flow equation considering the rough surface is as follows: The expression of the transient average Reynolds equation considering the mass conservation cavitation effect is as follows: Where p cav Expressed as cavitation pressure; The fluid pressure and cavitation fraction are calculated using the Gauss-Seidel iterative method; the convergence of the numerical solution is accelerated by the super-relaxation method, which is expressed as follows: Where, Expressed as the initial values ​​of the fluid pressure and cavitation fraction, the updated expressions are as follows: Where, ω P and ω Θ Expressed as super-relaxation factor; The expressions for the convergence criteria of fluid pressure and cavitation fraction are as follows: Where, ζ p and ζ Θ are respectively expressed as the convergence tolerance of fluid pressure and cavitation fraction; The expression of the asperity contact model is as follows: Where, Where, 5. The friction dynamics analysis method of a herringbone micro-groove sliding bearing during the startup phase according to claim 1, characterized in that: In step S6, the bearing performance parameters are output, including: According to Newton's second law, the force balance equation considering the rotor unbalance mass and external impact load is expressed as follows: Where W ex and W ey They are expressed as external load components, Q ubx and Q uby They are respectively expressed as unbalanced force components, Q ex and Q ey They are respectively expressed as impact load components, W hx and W hy They are respectively represented as fluid force components, W ax and W ay They are expressed as contact force components, F fx and F fy Expressed as friction force components, m j Expressed as shaft mass; The force balance equation is calculated based on the Newmark method, and its expression is as follows: Where x and y are displacement components, x′ and y′ are velocity components, x″ and y″ are acceleration components, Δt is the time step, and α is the time step. t and β t are expressed as constants of 0.5 and 0.25, respectively; The expression of the transient fluid force is as follows: The expression of the transient contact force is as follows: The expression of transient friction force is as follows: Where μ r Expressed as the dry friction coefficient, φ fp ,φ f and φ fs The expressions for shear stress factor, transient friction coefficient and contact loss are as follows:

6. The method for analyzing friction dynamics of a herringbone micro-groove sliding bearing during the startup phase according to claim 1, characterized in that: In step S1, the initial bearing parameters are input, including: The initial parameters of the bearing are as follows: Bearing length, journal radius, bearing clearance, fluid viscosity, rotor mass, elastic model of bearing and its Poisson's ratio, elastic model of journal and its Poisson's ratio, roughness parameters of bearing and roughness parameters of journal.

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