CN110296837B - Sliding bearing load measuring method based on bearing bush deformation - Google Patents

Sliding bearing load measuring method based on bearing bush deformation Download PDF

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CN110296837B
CN110296837B CN201810247637.9A CN201810247637A CN110296837B CN 110296837 B CN110296837 B CN 110296837B CN 201810247637 A CN201810247637 A CN 201810247637A CN 110296837 B CN110296837 B CN 110296837B
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bearing
strain
bearing bush
load
stress
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张世东
王健
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Shanghai Minghua Power Technology Co ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M13/00—Testing of machine parts
    • G01M13/04—Bearings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract

The invention provides a method for measuring bearing load by measuring bearing shell deformation, which calculates the load born by a sliding bearing in an actual installation state by testing the deformation of the bearing shell. Compared with the prior art, the sliding bearing load measuring method based on bearing shell deformation has the advantages that the test result has higher reliability, the measurement result also has higher accuracy, the workload required to be measured is small, the method is suitable for load test of most sliding bearings, and the popularization prospect is higher.

Description

Sliding bearing load measuring method based on bearing bush deformation
Technical Field
The invention relates to a method for measuring bearing load of a shaft, in particular to a method for testing the load of a sliding bearing based on bearing bush deformation, which is used for testing the load borne by various rotating machinery sliding bearings in the actual installation state and provides help for evaluating the centering quality of a shaft system, the installation quality of the bearing bush and the safe operation life.
Background
In modern industry, bearings are important components of various types of rotating machinery, and are important for safe and stable operation of a unit. A great deal of research and practice has shown that the loads to which a bearing is subjected directly affect its operating conditions. The bearing bears too heavy, which can cause the faults of high tile temperature, black gold fragmentation, tile grinding and the like; the bearing is too light, and faults such as oil film whirling and oil film oscillation are easy to occur. The two conditions can cause the vibration of a rotating mechanical shafting to be increased, and the safe operation of the unit is influenced. Therefore, the test calculation of the bearing load is very important.
Currently, there are several common methods for measuring bearing load: (1) a jacking method: and a jack is arranged under the rotating shaft near the bearing to be measured, a dial indicator is arranged above the rotating shaft, and the load of the bearing is calculated through a jacking curve. To be accurate, the method requires that the shaft be lifted a distance, i.e. the bearing is "backed" off. However, since the bearing clearance is usually small, the upper bearing shell is easily touched during jacking, so that an additional counter force from the upper bearing shell is received, and the measurement error is increased. Moreover, the method has the disadvantages of large workload and poor practicability. (2) Oil pressure method: an oil pressure sensor is arranged at the bottom of the bearing, and the load is reversely pushed by actually measured oil film pressure of the bearing. The accuracy of the method depends on the accuracy of a calculation model, the position of an oil film pressure measuring point and the like, a plurality of influence factors and uncertainties are caused, and the test error is large. (3) Force measurement method: and a force sensor is arranged at the bottom of the bearing seat to test the bearing load. The utility model discloses a load cell for 96236141.0, which is specially used in the load test process of tilting pad bearing. The load sensor is required to replace a cushion block between the bearing bush and the bearing seat, so that high requirements are required on the machining precision and the wear resistance of the load sensor. The method is not only limited in application field, but also can bring negative effects on the safe and stable operation of the bearing bush. (4) Strain method: the bearing load was calculated by measuring the bending strain of the cross section. Publication No. CN102323058 discloses a method for identifying bearing loads by measuring strain signals at different cross sections of a rotating shaft. The method needs to arrange a strain measuring point between every two bearings, and simultaneously needs to model a full-shaft system structure. The method has the problems of measurement error accumulation, transmission, divergence and the like, and has high dependence on modeling accuracy. And moreover, a measuring point needs to be arranged in the middle of the high and medium pressure cylinder, so that the workload and the difficulty are increased. Publication number CN 102650556 discloses a method for identifying bearing load by testing strain signals at three sections at both ends of a bearing. The method is limited by the structural space of a field shafting, for example, end cover bearings at two ends of a generator are connected with a stator of the generator into a whole, so that the requirement of three measuring sections at two ends cannot be met.
Disclosure of Invention
The invention aims to provide a measuring method for calculating bearing load by measuring bearing bush deformation, which is suitable for technical application of load calculation born by various rotating machinery sliding bearings in actual installation states and can provide help for evaluating shafting centering quality, bearing bush installation quality and operation life in the technical field.
In order to achieve the above object, the technical solution of the present invention is as follows:
a method for measuring the load of a sliding bearing based on the deformation of a bearing bush, which calculates the load born by the sliding bearing in the actual installation state by testing the deformation of the bearing bush, is characterized by comprising the following steps:
(1) and arranging a strain gauge on an axis right below the outer side surface of the lower bearing bush of the bearing to be measured as a strain measuring point, and performing oil-proof packaging on the strain measuring point. The strain gauge needs to be a strain gauge with a temperature compensation function so as to eliminate measurement errors caused by temperature;
(2) after the bearing bush is installed, the shaft is insertedWhen the neck is not installed, measuring the strain output signal value at the moment and recording as epsilon1；
(3) And when the shaft neck and the bearing seat are completely installed, measuring the value of a strain output signal in the actual installation state at the moment, and recording as epsilon2. Before the test, the rotor is continuously coiled for a plurality of weeks, and after the test is started, the average value in the plurality of weeks is used as a corresponding strain output signal;
(4) calculating the line deformation of the bearing bush in the circumferential direction under the action of external forces such as the gravity of the shaft neck, the installation pretightening force and the like, and recording as epsilonx(0) Then ex(0)＝ε2-ε1；
(5) Establishing a space coordinate system, and listing a bearing bush line strain formula at the installation position of the lower bearing bush strain measuring point according to the generalized hooke's law:
Figure GDA0002776515030000021
Figure GDA0002776515030000022
in the formula, E1、μ1The elastic modulus and the Poisson ratio of the bearing bush material are shown;
(6) the linear strain of the bearing bush at the position where the strain measuring point is arranged in the Y direction is 0, and the linear strain in the X direction is the measured strain epsilonx(0) Namely:
Figure GDA0002776515030000023
Figure GDA0002776515030000024
(7) under the stress state, the contact surface of the bearing bush and the shaft neck is rectangular, the half width of the contact surface is a, and the stress of the contact surface is p (x), wherein:
Figure GDA0002776515030000025
Figure GDA0002776515030000026
Figure GDA0002776515030000027
wherein F is the bearing load to be determined, l is the axial width of the bearing bush, and R is the axial width of the bearing bush1Radius of bearing bush, R2Journal radius, E2、μ2Respectively, the modulus of elasticity and the poisson's ratio of the journal material;
(8) the maximum positive stress borne by the bearing bush is the contact surface stress at the position where x is 0, namely:
Figure GDA0002776515030000031
(9) the stress field generated in the plane when the bearing bush and the shaft neck are contacted under the static state is in a plane strain state, and the distributed stress generated by the contact is as follows:
Figure GDA0002776515030000032
Figure GDA0002776515030000033
in the formula (I), the compound is shown in the specification,
Figure GDA0002776515030000034
and x and z are dimensionless coordinates.
(10) The coordinate of the lower bearing shell surface strain measuring point is x-0, z-delta/a, wherein delta is the thickness of the bearing shell, and then the distributed stress at the lower bearing shell strain measuring point installation position is as follows:
Figure GDA0002776515030000035
will calculate σ in step 10x,σzSubstituting into the linear strain formula in step 6, and the unknowns are the stress sigma in the F and Y directions of the load to be solvedyThe number of equations is also 2, the number of equations is equal to the number of unknowns, and the load F borne by the bearing is calculated.
Compared with the prior art, the sliding bearing load measuring method based on bearing shell deformation provided by the invention has the following technical effects:
1. the method is tested in the actual installation state of the bearing bush, and the test result has higher reliability;
2. the parameters required by the invention are the physical parameters of the shaft neck and the bearing bush, so that various errors such as modeling errors do not exist, and the measurement result has higher accuracy;
3. according to the invention, only a strain measuring point is needed to be arranged on the back surface of the bearing bush during maintenance, so that the workload required to be measured is small; and
4. the method does not change the structural characteristics and the installation characteristics of the bearing seat and the bearing bush, does not change the running characteristics of the bearing seat, is suitable for load tests of most sliding bearings, and has a high popularization prospect;
drawings
Fig. 1 is a schematic structural view of a bearing seat.
Fig. 2 is a schematic diagram of a bearing bush stress analysis coordinate system.
Fig. 3 is a schematic diagram of one embodiment of the present invention.
Fig. 4 is a flow chart of the operation of the present invention.
Wherein: 100-journal 101-bearing shell 102-bearing seat;
103-strain gauge 200-bearing
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
As shown in fig. 1 and 3, the outside surface of the bearing shell 101 is providedAnd a strain gauge is arranged on the axis right below the surface (the surface in contact with the bearing seat 102) to serve as a strain measuring point 103, and the strain measuring point is subjected to oil-proof packaging. The strain gauge needs to be a strain gauge with a temperature compensation function so as to eliminate measurement errors caused by temperature. In this way, the line deformation of the bearing shell in the circumferential direction at the strain measurement point in the actual installed state is measured and recorded as εx(0)；
When the bearing bush is installed but the shaft neck is not installed, a strain measuring unit with temperature self-compensation is used for recording and outputting a strain signal value epsilon1Namely, the bearing bush at the strain measuring point deforms along the initial line in the circumferential direction; when the shaft neck and the bearing seat are installed, the output value of the strain signal is recorded as epsilon2This is the linear deformation of the bearing shell in the circumferential direction at the strain measurement point in the actual mounting state. And (3) continuously coiling the rotor for a plurality of weeks before testing in an actual installation state, and taking the average value in the plurality of weeks as a corresponding strain output signal after the test is started.
Calculating the line deformation of the bearing bush at the strain measurement point along the circumferential direction under the action of external forces such as journal gravity, installation pretightening force and the like through the strain output signals, and recording the line deformation as epsilonx(0) Then ex(0)＝ε2-ε1。
For this purpose, with reference to fig. 4, the central control unit CPU operates by means of the following program:
1) the following physical parameters were collected and input, including the modulus of elasticity and poisson's ratio of the journal material, the modulus of elasticity and poisson's ratio of the bushing material, the journal radius, the bushing width, and the bushing thickness. These parameters can all be measured by conventional means;
2) according to the space coordinate system shown in fig. 2 and according to the generalized hooke's law, the formula for calculating the strain of the bushing line at the installation of the strain measuring point is as follows:
Figure GDA0002776515030000041
Figure GDA0002776515030000042
in the formula, E1、μ1The elastic modulus and the Poisson ratio of the bearing bush material are shown.
3) According to the structure of the bearing housing 102, since the bearing shell 101 is nested in the bearing housing 102 in the embodiment of the present invention, the linear strain in the Y direction is 0, and the linear strain in the X direction is the measured strain ∈x(0) Namely:
Figure GDA0002776515030000051
Figure GDA0002776515030000052
4) in a static state, the journal 100 is in elastic contact with the bearing shell 101, the journal 100 has no deformation, and the load only causes micro deformation of the bearing shell 101. According to the knowledge related to the contact mechanics, the contact surface between the bearing shell 101 and the journal 100 is rectangular, the half width of the contact surface is recorded as a, the contact surface stress is p (x), and p (x) is obtained by the following calculation formula:
Figure GDA0002776515030000053
Figure GDA0002776515030000054
Figure GDA0002776515030000055
wherein F is the load of the bearing to be determined, l is the width of the bearing shell 101, and R is1Radius of bearing shell 101, R2Radius of journal 100, E2、μ2Modulus of elasticity and poise of the material distributed as journal 100The bulk ratio;
5) according to the formula analysis of the contact surface stress, the maximum normal stress applied to the bearing shell 101 is the contact surface stress at x ═ 0, that is:
Figure GDA0002776515030000056
according to Hertz's theory, when the bearing pads 101 and the journal 100 are in static contact, the stress field generated in the plane is in a plane strain state, and the distributed stresses generated by the contact in the x and z directions are respectively obtained by the following calculation formulas:
Figure GDA0002776515030000057
Figure GDA0002776515030000058
in the formula (I), the compound is shown in the specification,
Figure GDA0002776515030000059
and x and z are dimensionless coordinates.
6) The coordinate at the strain measuring point on the surface of the bearing bush 101 is x is 0, z is- δ/a, wherein δ is the thickness of the bearing bush 101, and therefore, the stress distribution at the strain measuring point of the bearing bush 101 is as follows:
Figure GDA00027765150300000510
Figure GDA00027765150300000511
the sigma calculated in the step 6) is addedx,σzSubstituting the linear strain formula in the step (3), wherein the unknowns are the stress sigma in the F and Y directions of the load to be solvedyThe number of equations is also 2, the number of equations equals the number of unknownsThus, the load F to which the bearing is subjected can be derived.
The load F borne by the bearing is output and displayed by a load value output unit.
The load F numerical value obtained by calculation and measurement can be used in the technical application of load calculation born by various rotating machinery sliding bearings in the actual installation state, and can provide help for evaluating the shafting centering quality, the bearing bush installation quality and the service life in the technical field, thereby achieving the following effects:
1. because the test is carried out in the actual mounting state of the bearing bush, the test result has higher reliability;
2. the required parameters are physical parameters of the shaft neck and the bearing bush, various errors such as modeling errors do not exist, and the measurement result has higher accuracy;
3. only a strain measuring point is needed to be arranged on the back surface of the bearing bush during maintenance, and the workload required to be measured is small; and
4. the bearing seat and the bearing bush are not changed in structural characteristics and installation characteristics, and the running characteristics of the bearing seat are not changed, so that the bearing seat is suitable for load tests of most sliding bearings, and has a high popularization prospect.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (1)

1. A sliding bearing load measuring method based on bearing shell deformation is characterized by comprising the following steps:
(1) arranging a strain gauge on an axis right below the outer side surface of the lower bearing bush of the bearing to be measured as a strain measuring point, and performing oil-proof packaging on the strain measuring point; the strain gauge needs to be a strain gauge with a temperature compensation function so as to eliminate measurement errors caused by temperature;
(2) and measuring the strain output signal value when the bearing bush is installed but the shaft neck is not installed, and recording the value as epsilon1；
(3) And when the shaft neck and the bearing seat are completely installed, measuring the value of a strain output signal in the actual installation state at the moment, and recording as epsilon2(ii) a Before the test, the rotor is continuously coiled for a plurality of weeks, and after the test is started, the average value in the plurality of weeks is used as a corresponding strain output signal;
(4) calculating the line deformation of the bearing bush in the circumferential direction under the action of external forces such as the gravity of the shaft neck, the installation pretightening force and the like, and recording as epsilonx(0) Then ex(0)＝ε2-ε1；
(5) Establishing a space coordinate system, and listing a bearing bush line strain formula at the installation position of the lower bearing bush strain measuring point according to the generalized hooke's law:
Figure FDA0002760664580000011
Figure FDA0002760664580000012
in the formula, E1、μ1The elastic modulus and the Poisson ratio of the bearing bush material are shown;
(6) the linear strain of the bearing bush at the position where the strain measuring point is arranged in the Y direction is 0, and the linear strain in the X direction is the measured strain epsilonx(0) Namely:
Figure FDA0002760664580000013
Figure FDA0002760664580000014
(7) under the stress state, the contact surface of the bearing bush and the shaft neck is rectangular, the half width of the contact surface is recorded as a, and the stress of the contact surface is recorded as p (x), wherein:
Figure FDA0002760664580000015
Figure FDA0002760664580000016
Figure FDA0002760664580000017
wherein F is the bearing load to be determined, l is the axial width of the bearing bush, and R is the axial width of the bearing bush1Radius of bearing bush, R2Journal radius, E2、μ2Respectively, the modulus of elasticity and the poisson's ratio of the journal material;
(8) the maximum positive stress borne by the bearing bush is the contact surface stress at the position where x is 0, namely:
Figure FDA0002760664580000021
(9) the stress field generated in the plane when the bearing bush and the shaft neck are contacted under the static state is in a plane strain state, and the distributed stress generated by the contact is as follows:
Figure FDA0002760664580000022
Figure FDA0002760664580000023
in the formula (I), the compound is shown in the specification,
Figure FDA0002760664580000024
x and z are dimensionless coordinates;
(10) the coordinate of the lower bearing shell surface strain measuring point is x-0, z-delta/a, wherein delta is the thickness of the bearing shell, and then the distributed stress at the lower bearing shell strain measuring point installation position is as follows:
Figure FDA0002760664580000025
Figure FDA0002760664580000026
(11) σ calculated in step 10x,σzSubstituting into the linear strain formula in step 6, and the unknowns are the stress sigma in the F and Y directions of the load to be solvedyThe number of equations is also 2, the number of equations is equal to the number of unknowns, and the load F borne by the bearing is calculated.
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