CN113530944B - Bolt pre-tightening method and system - Google Patents
Bolt pre-tightening method and system Download PDFInfo
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- CN113530944B CN113530944B CN202110790895.3A CN202110790895A CN113530944B CN 113530944 B CN113530944 B CN 113530944B CN 202110790895 A CN202110790895 A CN 202110790895A CN 113530944 B CN113530944 B CN 113530944B
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- 230000002238 attenuated effect Effects 0.000 claims description 8
- 230000006641 stabilisation Effects 0.000 claims description 8
- 238000011105 stabilization Methods 0.000 claims description 8
- 230000036316 preload Effects 0.000 claims description 7
- 230000002045 lasting effect Effects 0.000 claims description 3
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000013016 damping Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 2
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16B—DEVICES FOR FASTENING OR SECURING CONSTRUCTIONAL ELEMENTS OR MACHINE PARTS TOGETHER, e.g. NAILS, BOLTS, CIRCLIPS, CLAMPS, CLIPS OR WEDGES; JOINTS OR JOINTING
- F16B35/00—Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/24—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
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Abstract
The application relates to a bolt pre-tightening method and a system, wherein the method comprises the following steps: acquiring measurement parameters of the bolt in the pre-tightening process, and acquiring an attenuation curve of the pre-tightening force of the bolt after loading according to the measurement parameters; obtaining an attenuation proportion R of the pretightening force based on the attenuation curve; obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation proportion R; and pre-tightening the bolt by taking the compensation pre-tightening force Fc as a design load. The attenuation proportion of the pretightening force is obtained according to the attenuation curve, so that when the bolt is locked, the compensation pretightening force can be obtained according to the target pretightening force and the attenuation proportion, and the bolt is preloaded by the compensation pretightening force, so that the actual value of the pretightening force of the bolt after attenuation can be closer to the target pretightening force, and the risk caused by insufficient bolt connection strength due to the deviation between the actual pretightening force of the bolt and the target pretightening force is reduced.
Description
Technical Field
The application relates to the technical field of bolt fastening, in particular to a bolt pre-tightening method and system.
Background
The high-strength bolt is one of the most common connection modes among all large parts of the wind generating set, and has the advantages of simple structure, convenience in maintenance and lower cost. In order to enhance the rigidity, tightness and anti-loosening capability of the bolt threaded connection and prevent the bolt threaded connection from sliding caused by transverse load, the threaded connection needs to be pre-tightened during assembly, and the conventional fastening modes of the high-strength bolt with large specification include the following two modes: a torque method using a hydraulic wrench and a stretching method using a hydraulic stretcher.
In the process of loading and pre-tightening the bolt, the bolt is generally loaded by adopting a designed value of the pre-tightening force, and due to system errors of a hydraulic wrench and a tensioner, torsional resilience and tensile resilience of the pre-tightened bolt, stress release of a clamped piece and other factors, the finally obtained pre-tightening force of the bolt is lower than the designed value, and particularly in some special fields such as wind power generation, the risk of insufficient connection strength among parts of a wind generating set exists.
Disclosure of Invention
In order to reduce the risk caused by insufficient bolt connection strength due to deviation between the actual pretightening force and the target pretightening force of the bolt, the application provides a bolt pretightening method and a bolt pretightening system.
In order to achieve the above object, the present application provides a bolt pretensioning method, which adopts the following technical scheme:
a bolt pre-tightening method comprises the following steps:
acquiring measurement parameters of the bolt in the pre-tightening process, and acquiring an attenuation curve of the pre-tightening force of the bolt after loading according to the measurement parameters;
obtaining an attenuation proportion R of the pretightening force based on the attenuation curve;
obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation proportion R;
and pre-tightening the bolt by taking the compensation pre-tightening force Fc as a design load.
By adopting the technical scheme, before the bolt is loaded, the attenuation curve of the pre-tightening force of the bolt after being loaded is obtained by adopting a mode of verifying the actual working condition, so that the attenuation proportion of the pre-tightening force of the bolt under the actual working condition can be known, the compensation pre-tightening force larger than the target value can be directly applied in the loading stage, the actual pre-tightening force of the bolt after being attenuated is closer to the target value when the bolt reaches a stable state, and the risk caused by insufficient connection strength of the bolt is reduced.
Optionally, the step of obtaining a decay curve of the pre-tightening force of the bolt after loading includes:
acquiring the original length of the bolt and the rod diameter D of the unthreaded part of the bolt before loading;
obtaining a shank cross-sectional area S of the bolt unthreaded portion based on a shank diameter D of the bolt unthreaded portion;
loading the bolt by using a loading tool with the target pretightening force F as a design load to obtain the elongation of the loaded bolt; removing the loading tool, waiting for the pretightening force of the bolt to be attenuated, and acquiring the elongation of the bolt in the attenuation process;
calculating the actual pre-tightening force F1 of the bolt in the loading and attenuation processes based on the elastic modulus E of the bolt, the cross-sectional area S of the rod part of the unthreaded part of the bolt, the elongation of the bolt and the original length L0 of the bolt;
and establishing a coordinate system by taking a time axis as an abscissa and taking the actual pretightening force F1 of the bolt in the loading and attenuation processes as an ordinate to form a pretightening force attenuation curve.
By adopting the technical scheme, the influence of variable factors such as friction coefficient, contact deformation and deformation of a connected piece can be eliminated based on the fact that the elongation of the bolt is only related to the stress of the bolt, so that the actual pretightening force of the bolt can be obtained by adopting the mode of calculating the elongation of the bolt, the inherent physical parameter cross-sectional area, the elastic modulus E and the original length of the bolt.
Optionally, the step of obtaining the attenuation ratio R of the actual pretightening force based on the attenuation curve includes:
acquiring a pretightening force stabilization time Tw based on a pretightening force attenuation curve and a pretightening force stabilization judgment condition, wherein the pretightening force stabilization judgment condition is that the maximum attenuation of the actual pretightening force lasting for 24 hours after Tw is not more than a threshold value;
obtaining the corresponding actual pretightening force Fw when Tw is based on the pretightening force attenuation curve;
calculating and obtaining the attenuation proportion R of the pretightening force according to the relation between the target pretightening force F and the actual pretightening force Fw, wherein:
R＝(F-F W )/F。
by adopting the technical scheme, the pretightening force can be attenuated continuously after the bolt is subjected to pretightening, but multiple times of experimental research show that the attenuation speed of the pretightening force is slower and slower along with the increase of time, the maximum attenuation value tends to be constant after the pretightening force lasts for 24 hours, and the value can be ignored compared with the design load, the threshold value of the maximum attenuation can be obtained based on the experiment, when the maximum attenuation value is less than or equal to the threshold value after the pretightening force lasts for 24 hours, the pretightening force can be considered to reach a stable state basically, the attenuation in a subsequent state is extremely small, continuous measurement is not needed, and on one hand, the working efficiency can be improved; on the other hand, based on the rule, attenuation of the pre-tightening force is obtained, the design load is recalculated according to the attenuation value and the target pre-tightening force, the bolt is loaded according to the recalculated design load, the expected target pre-tightening force can be basically obtained when the bolt tends to be in a stable state, and therefore the risk caused by insufficient connection strength due to deviation between the target pre-tightening force and the actual pre-tightening force is reduced.
Optionally, the step of obtaining the compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation ratio R includes: the relation among the target pretightening force F, the pretightening force attenuation proportion R and the compensation pretightening force Fc satisfies the following formula:
F c ＝F/(1-R)；
by the formula F c And F/(1-R) calculating to obtain the compensation pretightening force Fc.
By adopting the technical scheme, the compensation pretightening force Fc can be obtained through calculation of the formula, the formula is obtained through theoretical analysis, and the incidence relation among the target pretightening force F, the pretightening force attenuation proportion R and the compensation pretightening force Fc is objectively and accurately reflected, so that the real compensation pretightening force Fc can be obtained through the formula, and the calculation accuracy is improved.
Optionally, the step of preloading the bolt with the compensation preload Fc includes: and (3) loading and pre-tightening the bolt in multiple stages, wherein the loading pre-tightening force is increased step by step, and the final stage loading pre-tightening force is Fc.
By adopting the technical scheme, in the process of loading the bolt, the bolt and the clamped piece can generate slight elastic deformation, large stress is generated inside the bolt, and the stress generated by deformation can be released after the external force disappears, so that the pretightening force of the bolt is reduced; the bolts are pre-tightened for multiple times, and after each pre-tightening, the bolts can release part of stress, so that the stress released by the bolts after the pre-tightening force is loaded in the final stage is smaller, and the attenuation of the pre-tightening force is reduced.
Optionally, the step of loading and pre-tightening the bolt in multiple stages, where the loading pre-tightening force is gradually increased, and the step of loading the pre-tightening force in the final stage to Fc includes:
pre-tightening bolts to be pre-tightened which are uniformly arranged in the circumferential direction of a workpiece by a loading tool according to a cross symmetry method by taking the preset percentage of the target pre-tightening force F or the first preset percentage of the compensation pre-tightening force Fc as a design load;
pre-tightening bolts to be pre-tightened which are uniformly arranged in the circumferential direction of the workpiece by a loading tool according to a cross symmetry method by taking a second preset percentage of the target pre-tightening force F or a second preset percentage of the compensation pre-tightening force Fc as a design load; wherein the second preset percentage is greater than the first preset percentage;
and pre-tightening the bolts to be pre-tightened uniformly distributed on the periphery of the workpiece by using a loading tool according to a cross symmetry method by taking 100% of the compensation pre-tightening force Fc as a design load.
By adopting the technical scheme, the device is particularly suitable for the field of wind driven generators, bolts uniformly distributed on the flange plate are preloaded, and on one hand, smaller pretightening force attenuation can be obtained; on the other hand, the pretightening force attenuation curve shows obvious regular change, which is beneficial to improving and improving the connection performance of the bolt based on the change rule.
Optionally, after the step of preloading the bolt with the compensation preload Fc is completed, the method further includes:
loading the bolt after the loading and pre-tightening is completed by using a check value Fy so as to check the pre-tightening force of the bolt after the loading and pre-tightening is completed;
if the bolt does not rotate; then the verification is qualified;
and if the bolt rotates, confirming that the verification is unqualified.
Through adopting above-mentioned technical scheme, the pretightning force check-up can be examined the joint strength of bolt to can in time discover the bolt that actual pretightning force is not up to standard, further reduce the risk that the actual pretightning force of bolt is not enough to lead to.
Optionally, the determining of the check value Fy includes the following steps:
acquiring an actual pretightening force Fz of the bolt when a target pretightening force F is applied to the bolt based on a pretightening force attenuation curve;
calculating a random error deviation R1 according to the target pretightening force F and the actual pretightening force Fz;
acquiring the actual pretightening force Fk of the bolt when the loading tool is removed based on the pretightening force attenuation curve;
calculating a rebound error R2 according to the target pretightening force F, the actual pretightening force Fz of the bolt when the target pretightening force F is applied to the bolt and the actual pretightening force Fk of the bolt when the loading tool is removed;
calculating a check value Fy, F according to the target pretension F, the compensation pretension Fc, the random error deviation R1 and the rebound error R2 y ＝F+F c (R 1 +R 2 )。
By adopting the technical scheme, in the process of loading the bolt, random error deviation R1 exists between the tool output force value and the actual force value of the bolt due to random errors including tool errors, installation errors and personnel operation; after the tool is removed, the thread screwing clearance and the resilience error R2 caused by bolt deformation resilience after the tool is unloaded are realized, and during verification, the deviation caused by R1 and R2 is compensated on the basis of the target pretightening force, so that the load applied to the bolt during verification can be closer to the target pretightening force.
Optionally, an interval time between the step of performing the pre-tightening force verification on the bolt subjected to the loaded pre-tightening and the step of performing the pre-tightening loading on the bolt by compensating the pre-tightening force Fc is T W +T W ×10％T W +T W ×10％。
By adopting the technical scheme, the pre-tightening force of the bolt is attenuated to be basically stable and then verified, so that the actual pre-tightening force can be verified more accurately.
In order to achieve the above object, another aspect of the present application provides a bolt tightening system, which adopts the following technical solutions: a bolt pretensioning system comprising:
the measuring element is used for acquiring measuring parameters of the bolt in the pre-tightening process;
the pretightening force obtaining device is used for obtaining an attenuation curve of the pretightening force of the bolt after loading according to the measurement parameters, obtaining an attenuation proportion R of the pretightening force based on the attenuation curve, and obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation proportion R; and the loading tool is used for loading the bolt by taking the compensation pretightening force Fc as a design load.
By adopting the technical scheme, the measurement parameters in the bolt assembling process under the actual working condition can be obtained through the measurement element, the actual measurement parameters are used as the input of the pretightening force acquisition device, the measurement parameters are processed and calculated through running a program installed in the pretightening force acquisition device, the compensation pretightening force is finally obtained, the compensation pretightening force is used as a design load, the assembling bolt under the actual working condition is loaded through a loading tool, the expected target pretightening force can be finally obtained under a stable state, the deviation between the target pretightening force and the actual pretightening force can be greatly reduced through the scheme, the connection strength of the assembling bolt is improved, and the risk caused by the deviation can be further reduced.
In summary, the present application includes at least one of the following beneficial technical effects:
1. by obtaining a bolt pretightening force attenuation curve and obtaining an attenuation proportion of the pretightening force according to the attenuation curve, when the bolt is locked, a compensation pretightening force can be obtained according to a target pretightening force and the attenuation proportion, and the bolt is preloaded by the compensation pretightening force, so that the actual value of the pretightening force of the bolt after attenuation can be closer to the target pretightening force;
2. after the step of pre-tightening and loading the bolt by the compensation pre-tightening force Fc is completed, the bolt is loaded by the check value Fy to check the pre-tightening force, so that the connection strength of the bolt can be checked, and the bolt with the actual pre-tightening force not reaching the standard can be found in time.
Drawings
FIG. 1 is a schematic structural view of a bolt tightening system according to embodiment 1;
FIG. 2 is a flowchart of a bolt tightening method of example 1;
FIG. 3 is a schematic view of the structure of a bolt in embodiment 1;
fig. 4 is a coordinate system established in example 1 with a time axis as an abscissa and actual pretension of the bolt during the loading and damping processes as an ordinate, and includes two pretension damping curves when Fc and F are respectively loaded.
Detailed Description
The present application is described in further detail below with reference to the attached drawings.
Example 1
Referring to fig. 1, an embodiment of the present application discloses a bolt pretensioning system, which includes a measuring element, a pretensioning force obtaining device, and a loading tool, wherein the measuring element includes an ultrasonic measuring instrument, a diameter measuring sensor and/or a caliper; the pretightening force obtaining device comprises a memory and a processor, the memory stores a pretightening force calculation program and measurement parameters, the processor can adopt a single chip microcomputer, an MCU (microprogrammed control Unit) or a DSP (digital signal processor) and other microprocessors, and the processor can obtain a compensation pretightening force and a detection value when running the pretightening force calculation program; the loading tool can adopt an electric impact wrench, a hydraulic wrench and/or a hydraulic stretcher and the like; the loading tool can pre-load the bolt based on the compensation pre-tightening force or the detection value output by the pre-tightening force acquisition device as a design load.
Example 2
Referring to fig. 2, an embodiment of the present application discloses a bolt pretensioning method, including:
s100, acquiring measurement parameters of the bolt in the pre-tightening process, and acquiring an attenuation curve of the pre-tightening force of the bolt after loading according to the measurement parameters;
through the steps, the pre-tightening process parameters of the assembling bolt under the actual working condition can be measured, the pre-tightening force acquisition device is used for calculating through measurement or collection of the process parameters, the pre-tightening force attenuation curve after the assembling bolt is loaded under the actual working condition can be obtained, and the deviation under the assembling condition of each actual working condition can be met better, so that the attenuation curve which is more in fit with the actual condition is obtained, and the compensation pre-tightening force which is closer to the ideal value is obtained.
The measurement parameters can be measured by the measuring element, and it should be noted that: the measurement parameters comprise a plurality of measurement parameters which can be obtained by respectively measuring through one or more measurement elements, the process parameters need to be measured in one or more continuous time periods in the scheme, the acquisition frequency of the measurement parameters can be set through the pretightening force acquisition device, and the higher the acquisition frequency is, the more accurate the finally obtained attenuation curve is.
S200, obtaining an attenuation proportion R of the pretightening force based on an attenuation curve;
based on the obvious regular change of the attenuation curve obtained in step S100, the attenuation of the pre-tightening force is found to be changed in stages by analyzing the regular change, and the change in each stage is associated with the ratio of the design load applied to the loading tool, so that the attenuation value is expressed by the ratio R of the design load, i.e., the target pre-tightening force, a simpler calculation formula can be obtained, which is beneficial to reducing the calculation complexity and increasing the calculation speed, thereby reducing the requirement on the calculation capability of the chip and reducing the cost of the pre-tightening force acquisition device.
S300, obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation ratio R;
appropriate compensation can be performed on the basis of the target pretightening force F based on the pretightening force attenuation proportion R, so that the final attenuated actual pretightening force is consistent with the target pretightening force, a compensation value can be obtained through various theoretical analysis modes, and finally the sum of the compensation value and the target pretightening force F is used as the final compensation pretightening force Fc to be output.
S400, pre-tightening and loading the bolt by compensating the pre-tightening force Fc;
the bolt is loaded by the loading tool by taking the compensation pretightening force Fc output by the pretightening force acquisition device in the step S300 as a design load, and the bolt can be preloaded in any existing mode in the scheme. Note that the actual conditions of bolt assembly here are the same as those measured in step S100.
S500, pre-tightening force verification is carried out on the bolt subjected to the loading and pre-tightening;
in order to further reduce the risk caused by insufficient bolt connection strength, the bolts are subjected to pretightening force verification after being subjected to pretightening force loading by the compensation pretightening force Fc, and partially omitted loaded bolts caused by human factors in the process of loading a plurality of bolts can be detected, so that the pretightening force of all the bolts on the workpiece can reach the design value.
In the embodiment, before the pretightening force is applied to the bolt on the connecting structure, firstly, an attenuation curve of the pretightening force is obtained through a verification bolt which is the same as the bolt to be pretightened under the working condition, and an attenuation proportion R of the pretightening force of the bolt under the working condition is obtained according to the attenuation curve, then, a compensation pretightening force Fc is obtained according to a target pretightening force F of the bolt to be pretightened and the attenuation proportion R of the pretightening force of the bolt under the working condition, and then, the bolt to be pretightened is loaded with the compensation pretightening force Fc, so that the deviation between the actual pretightening force and the target pretightening force of the bolt to be pretightening force is small after the pretightening force attenuation process.
In other embodiments, when there are a plurality of bolts to be pre-tightened, one bolt to be pre-tightened can be selected as a verification member to obtain a pre-tightening force attenuation curve and a pre-tightening force attenuation ratio R.
The step S100 of obtaining the attenuation curve of the pre-tightening force of the bolt after the bolt is loaded includes:
s110, referring to fig. 3, before loading, the original length L0 of the bolt is obtained by ultrasonic measurement, the diameter D of the shank of the unthreaded part of the bolt is measured by a caliper, and then the area formula S ═ pi (D/2) is determined according to the circle 2- And calculating to obtain the cross section area S of the rod part of the unthreaded part of the bolt.
S120, applying a target pretightening force F to the bolt through a loading tool, performing three rounds in the loading process, firstly loading the bolt with 20% of the target pretightening force F by using an electric impact wrench, then loading the bolt with 80% of the target pretightening force F by using a hydraulic wrench or a hydraulic stretcher, and finally loading the bolt with 100% of the target pretightening force by using the hydraulic wrench or the hydraulic stretcher.
The bolt is elongated during the loading process of the bolt, the actual length of the bolt is measured by an ultrasonic measurement method after the loading process is finished, and the original length L0 is subtracted from the actual length of the bolt to obtain the elongation delta L of the bolt.
S130, removing the loading tool, waiting for the attenuation of the bolt pretightening force, reducing the elongation delta L of the bolt in the natural attenuation process of the bolt pretightening force, monitoring the real-time length of the bolt by an ultrasonic measurement method, and obtaining the elongation delta L of the bolt in the attenuation process;
s140, obtaining the elastic modulus E of the bolt with the pre-tightening force through a table look-up, calculating the actual pre-tightening force F1 of the bolt in the loading and attenuation processes through the elastic modulus E of the bolt, the cross section area S of the rod part of the thread-free part of the bolt, the elongation delta L of the bolt and the original length L0 of the bolt,
F 1 ＝E×S×ΔL/L 0 ，F 1 ＝E×S×ΔL/L 0 。
s150, referring to FIG. 4, a coordinate system is established by taking a time axis as an abscissa and taking the actual pretightening force F1 of the bolt in the loading and attenuation processes as an ordinate, so as to form a pretightening force attenuation curve, wherein the starting point of the abscissa is the moment when the maximum pretightening force is loaded to the bolt.
The step of obtaining the attenuation proportion R of the pretightening force based on the attenuation curve in the step S200 comprises the following steps:
s210, acquiring a pretightening force stabilization time Tw based on the pretightening force attenuation curve, wherein the maximum attenuation of the actual pretightening force lasting for 24H after Tw is not more than a threshold value, which is 0.5% in the embodiment.
S220, obtaining the corresponding actual pretightening force Fw in Tw based on the pretightening force attenuation curve.
S230, calculating to obtain a damping ratio R of the pre-tightening force according to the target pre-tightening force F and the actual pre-tightening force, wherein the damping ratio R is obtained through a formula R (F-F) W ) The calculation of/F was carried out.
In the step S300 of obtaining the compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation ratio R, if F is used c Loading the bolt, wherein the actually obtained pretightening force of the bolt is F c -F c X R, so if the actual pre-tightening force of the bolt is equal to the target pre-tightening force F, the formula F is obtained c -F c Obtaining a calculation formula F of the compensation pretightening force Fc after deformation c ＝F/(1-R)。
The compensation pretightening force Fc is not more than 90% of the yield strength of the bolt, and if the compensation pretightening force Fc is excessively close to the yield strength of the bolt, the bolt is partially subjected to unrecoverable plastic deformation to damage the bolt, so that the range of the compensation pretightening force Fc needs to be limited. When the compensation value is greater than 90% of the bolt yield strength, the bolt should be loaded with 90% of the bolt yield strength.
The step S400 of pre-tightening and loading the bolt with pre-tightening force comprises the following steps:
s410, loading the bolt through a loading tool according to the first preset percentage of the target pretightening force F as a design load, wherein the first preset percentage is 20% in the embodiment;
when being applied to the aerogenerator field specifically, aerogenerator component often connects through the ring flange, and is provided with a plurality of bolts along circumference on the ring flange, all needs to lock. At the moment, bolts and mounting holes of the whole flange connecting surface are numbered by Arabic numerals to prevent partial bolts from being screwed off, and then the bolts to be pre-tightened in the circumferential direction of the workpiece are loaded for the first time by a cross symmetry method, wherein the first loading value is 20% F. The cross symmetry method is adopted to load the bolt, so that the stress of the fixed member is more uniform, and the phenomenon of clamping caused by nonuniform stress of the member is avoided
S420, loading the bolt by using a loading tool according to a second preset percentage of the target pretightening force F as a design load, where the first preset percentage is 80% in this embodiment;
similarly, bolts on the flange connecting surface are subjected to secondary loading on the bolts to be pre-tightened in the circumferential direction of the workpiece by a cross symmetry method, and the secondary loading value is 80% F.
And S430, carrying out third loading and pre-tightening on the bolts to be pre-tightened uniformly distributed on the periphery of the workpiece by using a loading tool according to a cross symmetry method by taking 100% of the compensation pre-tightening force Fc as a design load.
After the step S400 is finished, a certain time interval is set, and after the pretightening force of the bolt is attenuated to be stable, the step S500 is carried out, wherein the time interval is T W +T W ×10％。
The step S500 of performing the preload verification on the bolt subjected to the preload loading includes the following steps:
s510, determining a check value Fy which passes through a formula F y ＝F+F c (R 1 +R 2 ) Is calculated to obtainWherein R1 is the random error deviation and R2 is the rebound error.
Two nodes exist on the attenuation curve of the pretightening force, wherein the moment when the bolt is loaded to the maximum value is a first node T0, the actual pretightening force Fz is smaller than the target pretightening force F, the random error deviation R1 occurs between the tool output force value and the bolt actual force value due to the random errors including tool errors, installation errors and personnel operation, and the random error deviation R1 is calculated according to a formula
R＝(F-F z )/F R＝(F-F z ) the/F is obtained by calculation.
The moment when the loading tool is removed is Tk second node, the actual pretightening force of the bolt is Fk, the pretightening force is rapidly attenuated in the stage of T0-Tk due to thread screwing clearance and bolt deformation rebound release after the tool is unloaded, the deviation generated in the stage is rebound error R2, and R2 is according to a formula
R 2 ＝(F z -F k ) And calculating to obtain the/F.
S520, loading the bolt by using the check value Fy, and if the bolt does not rotate in the loading process; and if the bolt rotates, the bolt is not qualified in verification and needs to be loaded again.
Example 2
The difference between this embodiment and embodiment 1 is that the step S400 of preloading the bolt with the preload Fc includes the following steps:
s410, according to 20% of target pretightening force Fc as a design load, carrying out first loading on the bolt by the design load by adopting a cross symmetry method;
s420, taking 80% of the target pretightening force Fc as a design load, and carrying out secondary loading on the bolt by the design load by adopting a cross symmetry method;
and S430, taking 100% of the target pretightening force Fc as a design load, and carrying out third loading on the bolt by the design load by adopting a cross symmetry method.
In this embodiment, the three loading processes are calculated based on Fc, which is beneficial to reducing the calculation complexity and increasing the calculation speed.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (9)
1. A bolt pre-tightening method is characterized by comprising the following steps:
acquiring measurement parameters of the bolt in the pre-tightening process, and acquiring an attenuation curve of the pre-tightening force of the bolt after loading according to the measurement parameters;
obtaining an attenuation proportion R of the pretightening force based on the attenuation curve;
obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation proportion R;
pre-tightening and loading the bolt by taking the compensation pre-tightening force Fc as a design load;
the step of obtaining the attenuation curve of the pre-tightening force of the bolt after loading comprises the following steps:
obtaining an original length L0 of the bolt and a shank diameter D of the unthreaded portion of the bolt prior to loading;
obtaining a shank cross-sectional area S of the bolt unthreaded portion based on a shank diameter D of the bolt unthreaded portion;
loading the bolt by using a loading tool with the target pretightening force F as a design load to obtain the elongation of the loaded bolt;
removing the loading tool, waiting for the pretightening force of the bolt to be attenuated, and acquiring the elongation of the bolt in the attenuation process;
calculating the actual pre-tightening force F1 of the bolt in the loading and attenuation processes based on the elastic modulus E of the bolt, the cross-sectional area S of the rod part of the unthreaded part of the bolt, the elongation of the bolt and the original length L0 of the bolt;
and establishing a coordinate system by taking a time axis as an abscissa and taking the actual pretightening force F1 of the bolt in the loading and attenuation processes as an ordinate to form a pretightening force attenuation curve.
2. The bolt pretensioning method according to claim 1, wherein the step of obtaining the attenuation ratio R of the actual pretensioning force based on the attenuation curve comprises:
acquiring a pretightening force stabilization time Tw based on a pretightening force attenuation curve and a pretightening force stabilization judgment condition, wherein the pretightening force stabilization judgment condition is that the maximum attenuation of the actual pretightening force lasting for 24 hours after Tw is not more than a threshold value;
obtaining the corresponding actual pretightening force Fw when Tw is based on the pretightening force attenuation curve;
calculating and obtaining the attenuation proportion R of the pretightening force according to the relation between the target pretightening force F and the actual pretightening force Fw, wherein:
R＝(F-F W )/F。
3. the bolt pretensioning method according to claim 1, wherein the step of obtaining the compensation pretension force Fc according to the target pretension force F and the pretension force attenuation ratio R comprises:
the relation among the target pretightening force F, the pretightening force attenuation proportion R and the compensation pretightening force Fc satisfies the following formula: f c ＝F/(1-R)；
By the formula F c And F/(1-R) calculating to obtain the compensation pretightening force Fc.
4. A method of pre-tightening a bolt according to claim 1, wherein the step of pre-tightening the bolt with the compensation pre-tightening force Fc comprises:
and (3) loading and pre-tightening the bolt in multiple stages, wherein the loading pre-tightening force is increased step by step, and the final stage loading pre-tightening force is Fc.
5. The method of claim 4, wherein the step of pre-tightening the bolt in multiple stages with increasing pre-tightening force, and the step of final stage pre-tightening force Fc comprises:
pre-tightening bolts to be pre-tightened which are uniformly arranged on the periphery of a workpiece by a loading tool according to a cross symmetry method by taking a first preset percentage of a target pre-tightening force F or a first preset percentage of a compensation pre-tightening force Fc as a design load;
pre-tightening bolts to be pre-tightened which are uniformly arranged in the circumferential direction of the workpiece by a loading tool according to a cross symmetry method by taking a second preset percentage of the target pre-tightening force F or a second preset percentage of the compensation pre-tightening force Fc as a design load; wherein the second preset percentage is greater than the first preset percentage;
and pre-tightening the bolts to be pre-tightened uniformly distributed on the periphery of the workpiece by using a loading tool according to a cross symmetry method by taking 100% of the compensation pre-tightening force Fc as a design load.
6. A method according to claim 4 or 5, further comprising, after the step of preloading the bolt with the compensation preload Fc:
loading the bolt after the loading and pre-tightening is completed by using a check value Fy so as to check the pre-tightening force of the bolt after the loading and pre-tightening is completed;
if the bolt does not rotate; then the verification is qualified;
and if the bolt rotates, confirming that the verification is unqualified.
7. A bolt pretensioning method according to claim 6, characterised in that the determination of the check value Fy comprises the following steps:
acquiring an actual pretightening force Fz of the bolt when a target pretightening force F is applied to the bolt based on a pretightening force attenuation curve;
calculating a random error deviation R1 according to the target pretightening force F and the actual pretightening force Fz;
acquiring the actual pretightening force Fk of the bolt when the loading tool is removed based on the pretightening force attenuation curve;
calculating a stress release deviation R2 according to the target pretightening force F, the actual pretightening force Fz of the bolt when the target pretightening force F is applied to the bolt and the actual pretightening force Fk of the bolt when the loading tool is removed;
calculating check values Fy and F according to the target pretension F, the compensation pretension Fc, the random error deviation R1 and the stress release deviation R2 y ＝F+F c (R 1 +R 2 )。
8. A method of pretensioning a bolt according to claim 6, characterized in that: the interval time between the step of performing the pre-tightening force verification on the loaded and pre-tightened bolt and the step of performing the pre-tightening load on the bolt by the compensation pre-tightening force Fc is as follows: t is W +T W X 10% and Tw is the pretightening force stabilization time.
9. A bolt pretensioning system for the bolt pretensioning method according to any one of claims 1 to 8, comprising:
the measuring element is used for acquiring measuring parameters of the bolt in the pre-tightening process;
the pretightening force obtaining device is used for obtaining an attenuation curve of the pretightening force of the bolt after loading according to the measurement parameters, obtaining an attenuation proportion R of the pretightening force based on the attenuation curve, and obtaining a compensation pretightening force Fc according to the target pretightening force F and the pretightening force attenuation proportion R;
and the loading tool is used for loading the bolt according to the compensation pretightening force Fc as the design load.
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| CN115076205A (en) * | 2022-06-22 | 2022-09-20 | 东方电气风电股份有限公司 | Novel bolt anti-loosening method applied to oil immersion environment of wind generating set |
| CN116067555B (en) * | 2023-04-06 | 2023-06-23 | 西南交通大学 | Bolt looseness detection system and method for urban rail transit and storage medium |
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