CN-116796451-B - Dynamic bearing mixed viscoelastic flow lubricating performance calculation method under inclination of journal

Abstract

The invention discloses a method for calculating the mixed viscoelastic flow lubrication performance of a dynamic bearing under the inclination of a journal, which solves the problem that the mixed lubrication performance of the dynamic bearing is calculated by the traditional method under the inclined working condition of the journal, and the viscoelasticity deformation effect of the bearing is obvious due to the fact that the load is ignored greatly and quickly changed; according to the invention, the oil film cavitation and friction interface surface morphology effect are comprehensively considered, a mass conservation average Reynolds equation is established, then the inclined state of the bearing is represented by adopting two journal inclination angles in the horizontal and vertical directions, the bearing viscoelastic deformation under the action of dynamic load is calculated by utilizing a standard linear solid model, the oil film thickness distribution under the influence of the bearing viscoelastic deformation and the journal inclination is corrected, finally a journal motion equation is established, the journal eccentricity and the eccentric speed are updated by adopting a Newmark method, and the dynamic load bearing mixed viscoelastic flow lubrication performance parameter is calculated iteratively.

Inventors

• XIONG GUOQING
• MAO ZHIWEI
• Feng Zejiang
• WANG HUAILEI
• Lian Shimiao
• ZHANG JINJIE
• JIANG ZHINONG

Assignees

• 北京化工大学

Dates

Publication Date

20260508

Application Date

20230303

Claims (1)

1. 1. The method for calculating the mixed viscoelastic flow lubricating performance of the dynamic bearing under the inclination of the journal is characterized by comprising the following steps of: Firstly, setting initial parameters of a dynamic load sliding bearing system; (1) Determining the radius, length, elastic modulus, poisson ratio and physical parameters of lubricating oil of a journal and a bearing of a dynamic load sliding bearing system; (2) Setting the initial eccentricity and the eccentric speed of the journal, wherein the initial eccentricity selection range of the dynamic load sliding bearing system is 0~c, c is a radial clearance, and the initial eccentric speed of the sliding bearing system is set to be 0 at the initial moment; (3) The inclination of the journal is characterized by adopting inclination angles in the horizontal direction and the vertical direction, and oil inlet pressure is utilized to initialize oil film pressure distribution; Secondly, establishing a lubrication control equation; In order to consider the influence of lubrication oil film cavitation on lubrication characteristics, a mass conservation equation is utilized to introduce a fluid fraction theta, so that a mass conservation average Reynolds equation is established; Wherein p represents oil film pressure, h represents oil film thickness, h T represents average oil film thickness, x represents circumferential coordinates, z represents axial coordinates, phi x and phi z represent pressure flow factors in x direction and z direction, respectively, phi s represents shear flow factor, U represents journal tangential velocity, For the standard deviation of the comprehensive roughness of the surface of the journal of the bearing, sigma j and sigma b are the standard deviations of the roughness of the journal and the surface of the bearing respectively, and t represents time; mu is the dynamic viscosity of the lubricating oil calculated by adopting Barus viscosity-pressure equation, and the equation is as follows: Wherein μ 0 represents the dynamic viscosity of the lubricating oil at normal pressure; discretizing the formula (1) by using a second-order center difference format of a finite difference method, and then solving oil film pressure and fluid fraction by using an ultra-relaxation iteration method: wherein i and j respectively represent the sequence numbers of the circumferential grid nodes and the axial grid nodes, n represents the number of time cycle steps, k represents the number of iteration hesitate to advance further, And (3) with Respectively representing the oil film pressure obtained by the kth and the kth-1 iteration of the node (i, j) at the nth time step number, And (3) with Respectively representing fluid fractions obtained by the kth and the kth-1 iteration of the node (i, j) at the nth time step number, w p represents a super-relaxation parameter of oil film pressure, and w θ represents a super-relaxation parameter of the fluid fraction; To ensure that the oil film pressure and fluid fraction converge in the iterative process, the convergence criterion is: Wherein N 1 and N 2 represent the number of circumferential and axial nodes, respectively, ζ p is the convergence tolerance of oil film pressure, ζ θ is the convergence tolerance of fluid fraction; thirdly, constructing a bearing viscoelasticity deformation equation; the viscoelastic deformation mechanism of the dynamic sliding bearing under load is characterized by adopting a standard linear solid model, and the equation is as follows: wherein delta (x, z, t) represents the actual deformation of the bearing at the current simulation time, delta t (x, z, t) represents the complete elastic deformation of the bearing at the current simulation time, delta l (x, z, t-Deltat) represents the time-lag deformation of the bearing at the last simulation time, The method comprises the steps that the complete time-lag deformation of a bearing under the oil film pressure p at the last simulation moment is represented, τ represents the viscoelasticity relaxation time of a bearing material, q represents the total step number of the simulation time, and Deltat represents the time step; the complete elastic deformation of the sliding bearing is solved by adopting a Winkler method: Wherein v b and E b respectively represent the Poisson's ratio and the elastic modulus of the bearing, and l represents the thickness of the sliding bearing; fourthly, solving the thickness distribution of the oil film; the thickness of the dynamic load sliding bearing oil film considering bearing clearance, eccentricity, journal inclination and bearing viscoelasticity deformation is as follows: h=h 0 +h mis +h v (7) wherein h 0 is an oil film thickness component considering radial clearance between the bearing and the journal and eccentricity of the journal, h mis is an oil film thickness component corrected for inclination of the journal, and h v is an oil film thickness component corrected for viscoelastic deformation of the bearing, i.e., h v =δ (x, z, t); The equation for h 0 is as follows: Wherein c is radial clearance, X is the eccentricity of the center of the shaft neck in the X direction, Y is the eccentricity of the center of the shaft neck in the Y direction, Y is the coordinate of the thickness direction of the oil film, Is the journal offset angle; The journal tilting effect is represented by adopting two tilt angles gamma x and gamma y of a horizontal plane and a vertical plane, and an oil film thickness component equation for correcting the journal tilting is obtained according to the geometric position relationship of the journal in a bearing hole when the journal tilts; Wherein R b is the radius of the bearing, and B is the width of the bearing; As can be seen from equation (9), when γ x ＝γ y =0, h mis =0, at which point equation (7) is shifted to the oil film thickness in the journal non-inclined state; Fifthly, establishing a journal motion equation; The lubrication control equation (1) is to update the eccentricity and the eccentric speed iteratively by using the journal motion equation at a given initial eccentricity and eccentric speed to correct the oil film thickness and the oil film pressure, wherein the journal centroid is assumed to be effective mass particle in the present document, and the motion equation of the journal in the dynamic sliding bearing system is expressed as follows: Wherein m j represents the journal mass, And (3) with The x-and y-direction eccentric accelerations are indicated respectively, And Representing the dynamic loads acting in the x and y directions of the plain bearing system respectively, And The oil film forces in the x and y directions are indicated respectively, And The rough contact forces in the x and y directions are shown, respectively; In the mixed lubrication state, the oil film pressure and the rough contact pressure respectively form the oil film force and the rough contact force of the bearing, and the oil film force and the rough contact force can be obtained by adopting a complex trapezoidal integral to the pressure: wherein p asp represents a rough contact pressure; solving the equation (10) by adopting a Newmark method to iteratively calculate the eccentricity of the minimum difference between the external load and the calculated supporting load, wherein the adopted convergence criterion is as follows: Wherein, X n and X n-1 respectively represent the eccentricities in the X direction calculated under the time steps n and n-1, Y n and Y n-1 respectively represent the eccentricities in the Y direction calculated under the time steps n and n-1, ζ X is the convergence tolerance of X, ζ Y is the convergence tolerance of Y; step six, calculating the mixed lubrication performance parameter; the mixed lubrication performance of the dynamic load sliding bearing in the inclined state of the journal comprises inclination moment, friction power consumption and end leakage flow; for a bearing with inclined shaft neck, the oil film pressure on two sides of the central section of the bearing is asymmetric, and in order to make the bearing work stably, corresponding moment needs to act on the bearing, and the bearing inclination moment components in the x and y directions are as follows: the tilting moment of the combination is as follows: Viscous friction caused by liquid shear of friction F f under mixed lubrication Friction of asperity contact caused by contact with asperity peaks The two parts are composed of the following expressions: Wherein κ=0.02 is the boundary friction coefficient, Φ f is the shear flow factor, Φ fs is the shear stress factor and Φ fp is the friction pressure flow factor; Phi f 、φ fs and phi fp are calculated using the following relationships: Wherein Λ=h/σ represents a film thickness ratio, g=Λ/3 represents a film thickness judgment index, and e represents a natural constant; for friction power consumption, equal to the product of friction and tangential velocity; P f ＝|F f U| (22) Wherein F f is the friction force calculated by the formula (16), and U is the tangential speed of the shaft neck; When the journal is inclined, the end leakage amounts Q 1 and Q 2 of the front end face and the rear end face of the bearing can be calculated as follows: The total end bleed flow is: Q=Q 1 +Q 2 (25)。

Description

Dynamic bearing mixed viscoelastic flow lubricating performance calculation method under inclination of journal Technical Field The invention belongs to the technical field of dynamic load sliding bearing lubrication performance solving, and particularly relates to a dynamic load bearing mixed viscoelastic flow lubrication performance calculation method under the inclination of a journal. Background The coupling system of the shaft and the dynamic load sliding bearing is a key supporting transmission system for ensuring the performance integrity of mechanical equipment and is widely applied to various reciprocating and rotating machines. During actual operation of a dynamic bearing system, the inclination of the journal is unavoidable due to factors such as machining errors, assembly errors, deformation of the shaft under load, etc. The presence of the journal tilt changes the oil film pressure and oil film thickness distribution of the lubricating oil, increases the friction between the bearing and the journal surface, and in severe cases, can exacerbate bearing surface wear and even cause system oscillations. The dynamic load sliding bearing has smaller eccentricity under the heavy load effect, and is in a mixed lubrication state of oil film, boundary and dry friction for a long time. According to the existing hybrid elastic hydrodynamic lubrication theory for analyzing the lubrication performance of the dynamic load sliding bearing, the thickness distribution of an oil film is corrected by the complete elastic deformation of the surface of the bearing under the action of a high-pressure oil film, and the hybrid lubrication performance of the bearing under the dynamic load is calculated. However, metallic materials have proven to be viscoelastic, and the deformation of the bearing surface upon loading exhibits a viscous and elastic mutual coupling, i.e. a viscoelastic deformation effect. The mixed lubrication performance parameters such as oil film pressure, oil film thickness, rough contact pressure, friction power consumption and end leakage flow are key keys of the lubrication problem of the dynamic sliding bearing, the complete elasticity is used as a bearing compression deformation criterion, initial knocking and rough bumping and grinding characteristics of the bearing in a journal tilting state are easily ignored, the lubrication parameters of the dynamic sliding bearing under severe working conditions are difficult to accurately calculate, the lubrication condition of the bearing is difficult to master, and further the structural optimization design improvement and lubrication performance monitoring of the dynamic sliding bearing are influenced. Therefore, aiming at the problems that the dynamic bearing mixed viscoelastic flow lubrication characteristic under the inclination of the journal is unknown and the complex coupling physical field numerical analysis still lacks theoretical basis, the invention provides an accurate and efficient numerical calculation method for solving the dynamic bearing mixed viscoelastic flow lubrication performance under the inclination of the journal. Disclosure of Invention The invention aims to provide a method for calculating the mixed viscoelastic flow lubrication performance of a dynamic bearing under the inclination of a journal aiming at the viscoelastic deformation effect generated by the compression of the surface of the sliding bearing under the inclination working condition of the journal and dynamic load. The aim of the invention is achieved by the following technical scheme: firstly, determining geometric and material parameters of the journal and the bearing and physical parameters of lubricating oil, setting initial eccentricity of the journal, initial eccentric speed, inclination angle of the journal in horizontal direction and vertical direction, and determining oil inlet pressure. Secondly, comprehensively considering the surface morphology effect of the oil film cavitation and friction interface, establishing a mass conservation average Reynolds equation, discretizing the Reynolds equation by using a finite difference method, and solving the oil film pressure by using an ultra-relaxation iterative algorithm. And solving the viscoelastic deformation of the bearing surface under the high-pressure oil film by using a standard linear solid model, and constructing a sliding bearing viscoelastic deformation equation at any moment. And secondly, characterizing the inclination state of the journal by using two journal inclination angles in the horizontal direction and the vertical direction, and establishing the oil film thickness distribution under the correction of the viscoelastic deformation and the journal inclination. And finally, constructing a journal motion equation by combining the dynamic load, the oil film force and the rough contact force of the sliding bearing, updating the eccentricity and the eccentric speed of the journal, and iteratively c