CN112729789B - Method for formulating and evaluating tightening process of plastic region of key bolt of engine - Google Patents
Method for formulating and evaluating tightening process of plastic region of key bolt of engine Download PDFInfo
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- CN112729789B CN112729789B CN202011547126.2A CN202011547126A CN112729789B CN 112729789 B CN112729789 B CN 112729789B CN 202011547126 A CN202011547126 A CN 202011547126A CN 112729789 B CN112729789 B CN 112729789B
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- G01M13/00—Testing of machine parts
Abstract
The invention discloses a method for formulating and evaluating a tightening process of a plastic region of a key bolt of an engine, which comprises the following steps: measuring a bolt plasticity curve; outputting signals of the pretightening force, the torque and the corner to measuring equipment in real time; determining a target pretightening force of the bolt, tightening the bolt to the target pretightening force at a constant speed, and recording the relation change curves of torque-pretightening force and corner-pretightening force in real time; taking the pretightening force of the bolt tightening end point as a target pretightening force as a starting point, and obtaining a starting pretightening force and a starting torque corresponding to the bolt; measuring the permanent deformation/stretching amount of the bolt, determining the deformation length of the bolt, and calculating the bolt tightening residual deformation rate; reselecting a bolt, repeating the steps, recording the residual deformation rate of the bolt, and confirming that the measured data of the bolts are consistent; and if the residual deformation rate of the bolt meets the set conditions, judging that the bolt tightening process is qualified. The accurate control of the bolt axial force is realized, and the reliability of the bolt is ensured through the control and evaluation of the residual elongation of the bolt.
Description
Technical Field
The invention relates to the technical field of engine assembly processes, in particular to a method for establishing and evaluating a tightening process of a plastic region of a key bolt of an engine.
Background
The key bolts of the engine are respectively used for fastening and connecting the main system and the mechanism of the engine and are subjected to larger alternating load. Therefore, enough and proper pretightening force needs to be applied to the bolt coupling system in the bolt assembling stage so as to overcome the serious faults of bolt coupling failure, engine damage and the like caused by the attenuation of clamping force generated by the bolt or the creep of the connected piece after the connected piece is compressed and runs for a long time in the assembling process. Therefore, in the bolt assembling stage, the establishment of a reasonable screwing process is crucial to the reliability of the bolt coupling system.
The existing bolt tightening methods suitable for mass production mainly comprise a torque control method, a torque-corner control method and a yield point control method. The torque method is simple and convenient to implement, low in cost, low in requirement on a tightening tool, easy to control and detect the torque and convenient to recheck after tightening, but the torque is greatly influenced by the friction coefficient deviation, so that the pretightening force variation of the bolt is large, and the accurate control of the pretightening force of the bolt is not facilitated; in order to reduce the risk of the bolt being overstretched, the bolt pre-tightening force is designed to be lower, so that the material utilization rate of the bolt is lower. The yield point control method is characterized in that the slope of the torque/corner of the bolt is monitored in real time in the bolt tightening process, and when the bolt is in elastic deformation, the torque rate is basically kept unchanged; when the yield deformation of the bolt occurs, the torque rate can be obviously reduced, the yield deformation of the bolt is confirmed to be the torque rate value through calibration in the early stage, and when the torque rate of the bolt is lower than the threshold value, the tightening system identifies that the bolt has yield and stops tightening. The yield point control method has high control precision on the pretightening force, the utilization rate of the bolt material is high, and the fatigue of a bolt connection system is good; however, the tightening system is very complex, requires expensive and high-precision measurement and execution equipment, is high in cost, and cannot perform recheck on the tightened bolt pretightening force. For key bolts of an engine, the balance of efficient operation and high-precision control is realized by a current common material torque-angle method. Therefore, it is important to establish a tightening process of the torque-angle method, especially for bolts tightened in a plastic region, to achieve a pre-tightening force design target value and avoid the bolt from being over-lengthened to cause failure. The current torque-angle method mainly depends on empirical calculation or is obtained by actually measuring torque, angles and other test means, has low accuracy, cannot be verified, cannot meet the process requirement of plastic domain tightening, and cannot simultaneously realize that the bolt pretightening force and the deformation simultaneously meet the requirement.
CN109159072B discloses a method for determining a target rotation angle of a cylinder head bolt, which comprises measuring an elasticity curve of the sample bolt; selecting a pre-tightening force corresponding to the intersection point of the elastic curve and the elastic-plastic curve as a first target pre-tightening force F' 1; selecting a pre-tightening force corresponding to 0.2% of residual deformation of the sample bolt as a second target pre-tightening force F' 2; CN109159072B only relates to selecting the pre-tightening force corresponding to 0.2% of residual deformation of the sample bolt as a second target pre-tightening force F' 2; does not involve calculation to determine the residual deformation rate of the bolt during each tightening
And calculating the total residual deformation rate of the bolt after multiple tightening to be less than 2%.
CN107356362A discloses a method for measuring bolt pretightening force and a method for verifying the bolt pretightening force, wherein: the stress-strain relationship is specifically as follows: sigma is the stress of the bolt to be tested, E is the elastic modulus,
taking the strain of the bolt to be detected, wherein L is the first length, and L' is the second length; CN107356362A is only disclosed
And (3) in order to strain the bolt to be tested, the retest pretightening force and the axial force deviation rate when the tightening process is formulated are not involved:
CN104614111B discloses that the calibration device of the invention is used for calibrating a proportionality constant K, which can effectively improve the calibration precision of the proportionality constant K, thereby effectively measuring the pretightening force of the bolt during the subsequent bolt installation and having the characteristic of high measurement precision; although the CN104614111B discloses that the comparison constant K is calibrated, the method does not relate to the situation that the pretightening force exceeds the upper limit of the designed pretightening force range when a bolt connecting system is screwed down, and simultaneously acquires a pretightening force signal and a bolt deformation signal through measuring equipment to form a pretightening force-bolt deformation signal relation curve and form a calibration file to be stored in the equipment.
Disclosure of Invention
The invention aims to solve the technical problem that in order to overcome the defects in the prior art, the invention provides a method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine, so that the accurate control of the axial force of the bolt is realized, and the reliability of the bolt is ensured by controlling and evaluating the residual elongation of the bolt.
The technical scheme adopted by the invention for solving the technical problems is as follows:
a method for formulating and evaluating a tightening process of a plastic region of a key bolt of an engine comprises the following steps:
1) measuring the yield strength of the bolt, and the yield point pre-tightening force and the friction coefficient in a tightening state;
2) keeping the clamping length of the bolt in an actual state, simulating bolt assembly on a bolt tightening machine, tightening a bolt connection system until the pretightening force exceeds the upper limit of the designed pretightening force range, simultaneously acquiring a pretightening force signal and a bolt deformation signal through measuring equipment to form a pretightening force-bolt deformation signal relation curve, and forming a plastic curve calibration file to be stored in the equipment;
3) connecting a measuring device, enabling a special probe to penetrate through a bolt sleeve to be tightly attached to a bolt head signal sensing piece, connecting a bolt sleeve adapter with a torque-corner sensor, and outputting three signals of pre-tightening force, torque and corner to the measuring device in real time by the signal sensing piece and the torque-corner sensor;
4) determining target pretightening force of the bolt according to the yield strength of the bolt, the yield point pretightening force and the friction coefficient in a tightening state which are obtained by early-stage measurement, tightening the bolt to the target pretightening force at a constant speed through tightening equipment, and recording relation change curves of torque-pretightening force and corner-pretightening force in real time;
5) the pretightening force of the bolt tightening end point is taken as a target pretightening force FMTaking the bolt as a starting point, and screwing the bolt by a certain angle theta along the direction of disassembling the bolt by taking the bolt as the starting point to obtain a starting pretightening force F corresponding to the boltbAnd a starting torque M;
6) after the bolt is loosened, according to the measured bolt plastic curve, measuring the permanent deformation/stretching amount L of the bolt caused by plastic deformation1Determining the deformation length L of the bolt according to the structural design characteristics of the bolt, calculating and determining the first tightening residual deformation rate of the bolt, and re-tightening the corresponding bolt;
7) repeating the step 6) n times by using the same bolt according to the screwing process formulated in the step 5), and measuring and calculating to obtain the residual deformation rate delta n of each time;
8) reselecting a bolt, repeating the steps 5) to 7), recording the corresponding residual deformation rate of the bolt until m bolts are tested, and confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt;
9) and if the actual measurement axial force deviation rate and the residual deformation rate of the bolt meet the set conditions, judging that the set bolt tightening process is qualified.
According to the technical scheme, in the step 5), the initial pretightening force FbAnd the starting torque M is obtained by a specific process: generating a composite relation curve by taking the pretightening force as a horizontal coordinate, the torque and the corner as a left vertical coordinate and a right vertical coordinate, wherein the composite relation curve comprises a corner-pretightening force curve and a torque-pretightening force curve, and the target pretightening force F is taken as the corner-pretightening force curveMAs a starting point, the bolt is screwed for a certain angle theta along the direction of disassembling the bolt, and after the angle theta is moved downwards along the vertical coordinate of the corner, the horizontal extension is carried out until the angle theta is intersected on the curve of the corner-pretightening force to obtain an initial pretightening force FbAnd vertically extending to a torque-pretension force curve, and obtaining a torque value which is the initial torque M through intersection.
According to the technical scheme, in the step 7), n is 2, namely the same bolt is repeatedly tightened and disassembled for 3 times according to the tightening process, and the residual deformation rates are respectively delta through 3 times of measurement and calculation1、Δ2And Δ3；
In the step 9), the setting condition is that the total residual deformation rate delta of the bolt after three times of tighteningt＝Δ1+Δ2+Δ3＜2％。
According to the technical scheme, when the bolt belongs to a flywheel bolt, the set conditions are replaced by: and n is 0, and the single-tightening residual deformation rate of the bolt ranges from 0.2% to 1%.
According to the technical scheme, in the step 8), m is more than or equal to 3.
As shown in fig. 4, the bolts are tightened according to the tightening process determined in S6 to tighten the second bolt again, and the residual deformation rate is measured after the bolt pre-tightening force is loosened after the first tightening; and measuring and recording the residual deformation rate of the bolt during the second and third tightening, and confirming the consistency of the measured data and the first bolt. It is recommended that the number of the tightening confirmation bolts is more than or equal to 3.
According to the technical scheme, in the step 8)The specific process of confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt is as follows: the bolt pretightening force is required to be measured when the bolt is tightened for the first time confirmed by the tightening process, and the retested pretightening force and the axial force deviation ratio when the tightening process is formulated are required to be measured:
wherein FMTo target pretension force, FiAnd remeasured pretightening force for different bolts.
According to the technical scheme, in the step 1), the method for measuring the yield strength, the yield point pretightening force and the friction coefficient of the bolt in the tightened state is to sample and measure bolts of the same batch of test samples, and the number of the sampled test samples is more than 5.
According to the technical scheme, before the step 2), the method further comprises the following steps: and (3) modifying the bolt, wherein the specific modification process is to grind the end part of the bolt, so that the parallelism of the end surface of the bolt reaches 0.02, and the surface roughness reaches Ra0.8-1.6 mm.
According to the technical scheme, before the step 2), the method further comprises the following steps: the material and mechanical property, clamping length and surface flatness of the processing accompany type gasket and nut are the same as those of the simulated real object part.
According to the technical scheme, in the step 6), the bolt tightening residual deformation rate is calculated and determined as follows:
wherein L is1The permanent set/elongation of the bolt due to plastic deformation, and L is the bolt deformation length.
The invention has the following beneficial effects:
1. the invention provides a method for formulating and evaluating a tightening process of a key bolt plastic domain of an engine, which is a forward and complete tightening process development method, can realize accurate control of bolt axial force and ensure the reliability of a bolt through the control of the residual elongation of the bolt; the design pretightening force range of the bolts is taken as a target, the tightening process is determined according to the relation among the pretightening force, the corner and the torque measured in real time in the tightening process, the consistency of the tightening process is confirmed through multiple times of tightening through a plurality of bolts, and the method is scientific, precise and high in reliability.
2. The invention provides a reliable data support for establishing a bolt tightening process by dynamically measuring pretightening force, corner and torque in real time in the bolt tightening process and forming axial force-corner and axial force-torsion relation curves.
Drawings
FIG. 1 is a flow chart of a method for formulating and evaluating a tightening process of a plastic region of a key bolt of an engine in an embodiment of the invention;
FIG. 2 is a tightening plasticity curve of a bolt in the embodiment of the invention;
FIG. 3 is a real-time relationship curve of torque, rotation angle and pre-tightening force during the bolt tightening process in the embodiment of the invention;
FIG. 4 is a graph showing the measurement of the residual deformation rate after the bolts are tightened and loosened in the embodiment of the present invention;
in the figure, 1-corner-pretension force curve, 2-torque-pretension force curve.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and examples.
Referring to fig. 1 to 4, in an embodiment of the present invention, a method for establishing and evaluating a plastic region tightening process of a key bolt of an engine includes the following steps:
1) measuring the yield strength of the bolt, and the yield point pre-tightening force and the friction coefficient in a tightening state;
2) keeping the clamping length of the bolt in an actual state, simulating bolt assembly on a bolt tightening machine, tightening a bolt connection system until the pretightening force exceeds the upper limit of the designed pretightening force range, simultaneously acquiring a pretightening force signal and a bolt deformation signal through measuring equipment to form a pretightening force-bolt deformation signal relation curve, and forming a plastic curve calibration file to be stored in the equipment; the calibration file is shown in FIG. 2;
3) connecting a measuring device, namely enabling a special probe to penetrate through a bolt sleeve to be tightly attached to a bolt head signal sensing piece, connecting a bolt sleeve adapter with a torque-corner sensor, respectively connecting the signal sensing piece and the torque-corner sensor with the measuring device, and respectively outputting three signals of pre-tightening force, torque and corner to the measuring device in real time by the signal sensing piece and the torque-corner sensor;
4) determining target pretightening force of the bolt according to the yield strength of the bolt, the yield point pretightening force and the friction coefficient in a tightening state which are obtained by early-stage measurement, tightening the bolt to the target pretightening force at a constant speed through tightening equipment, and recording relation change curves of torque-pretightening force and corner-pretightening force in real time;
5) the pretightening force of the bolt tightening end point is taken as a target pretightening force FMTaking the bolt as a starting point, and screwing the bolt by a certain angle theta along the direction of disassembling the bolt by taking the bolt as the starting point to obtain a starting pretightening force F corresponding to the boltbAnd a starting torque M;
6) after the bolt is loosened, according to the measured bolt plastic curve, measuring the permanent deformation/stretching amount L of the bolt caused by plastic deformation1Determining the deformation length L of the bolt according to the structural design characteristics of the bolt, and calculating and determining the first-time tightening residual deformation rate of the bolt
And re-screwing the corresponding bolt;
7) repeating the step 6) n times by using the same bolt according to the screwing process formulated in the step 5), and measuring and calculating to obtain the residual deformation rate delta n of each time;
8) reselecting a bolt, repeating the steps 5) to 7), recording the corresponding residual deformation rate of the bolt until m bolts are tested, and confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt;
9) and if the actual measurement axial force deviation rate and the residual deformation rate of the bolt meet the set conditions, judging that the set bolt tightening process is qualified.
Further, in the step 5), the initial pretightening force FbAnd the starting torque M is obtained by a specific process: the pretightening force is used as the abscissa, the torque and the corner are used as the left and right ordinates, and the pretightening force is used as the abscissaForming a composite relation curve which comprises a corner-pretightening force curve 1 and a torque-pretightening force curve 2, and on the corner-pretightening force curve 1, using a target pretightening force FMAs a starting point, the state position of the bolt is the screwing terminal point of the bolt, the bolt is screwed for a certain angle theta along the direction of disassembling the bolt, and after the angle vertical coordinate moves down by the angle theta, the bolt is horizontally extended to be crossed on the corner-pretensioning force curve 1 to obtain an initial pretensioning force FbAnd vertically extending the torque to a torque-pretension force curve 2, and obtaining a torque value which is the initial torque M through intersection.
Further, in the step 7), n is 2, that is, the same bolt is repeatedly tightened and loosened 3 times according to the tightening process, and the residual deformation ratios Δ are respectively obtained by measuring and calculating 3 times1、Δ2And Δ3；
In the step 9), the setting condition is that the total residual deformation rate delta of the bolt after three times of tighteningt＝Δ1+Δ2+Δ3＜2％。
Further, when the bolt belongs to a flywheel bolt, the set conditions are replaced by: and n is 0, and the single-tightening residual deformation rate of the bolt ranges from 0.2% to 1%.
Further, in the step 8), m is more than or equal to 3.
As shown in fig. 4, the bolts are tightened according to the tightening process determined in S6 to tighten the second bolt again, and the residual deformation rate is measured after the bolt pre-tightening force is loosened after the first tightening; and measuring and recording the residual deformation rate of the bolt during the second and third tightening, and confirming the consistency of the measured data and the first bolt. The number of the bolts is more than or equal to 3 after the bolts are recommended to be screwed; the consistency of the bolt tightening process is evaluated through retesting of the pretightening force of the bolts, the reliability of bolt tightening is judged through measuring the residual elongation by single and multiple tightening, and reasonable evaluation indexes and standards are provided for realizing a high-precision and safe tightening mode.
Further, in the step 8), a specific process of confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt is as follows: when the bolt confirmed by the tightening process is tightened for the first time, the pretightening force of the bolt needs to be measured and measured againThe measured pre-tightening force and the shaft force deviation rate when the tightening process is formulated are as follows:
wherein FMTo target pretension force, FiAnd remeasured pretightening force for different bolts.
Further, in the step 1), the method for measuring the yield strength, the yield point pretightening force and the friction coefficient of the bolt in the tightened state is to sample and measure bolts of the same batch of test samples, and the number of the sampled test samples is more than 5.
Further, before the step 2), the following steps are also included: and (3) modifying the bolt, wherein the specific modification process is to grind the end part of the bolt, so that the parallelism of the end surface of the bolt reaches 0.02, and the surface roughness reaches Ra0.8-1.6 mm.
Further, before the step 2), the following steps are also included: the material and mechanical property, clamping length and surface flatness of the processing accompany type gasket and nut are the same as those of the simulated real object part.
The working process of the invention is as follows:
s1: preparation of the test: and (3) performing performance test on parts of the same batch of the test sample pieces, measuring the yield strength of the bolt, the yield point pre-tightening force and the friction coefficient in a tightening state, wherein the number of the test sample pieces is more than 5.
S2: preparation of the test: modifying the bolt, grinding the end part of the bolt, and requiring that the parallelism of the end surface is 0.02 and the surface roughness Ra0.8-1.6 mm;
the processing of the accompanying gaskets and nuts requires the same materials, mechanical properties, clamping length, surface flatness and the like as those of the simulated real parts.
S3: calibrating a tightening curve: the actual clamping length of the bolt is maintained, and bolt assembly is simulated on a bolt tightening machine. And tightening the bolt connection system until the pretightening force exceeds the upper limit of the designed pretightening force range, simultaneously acquiring a pretightening force signal and a bolt deformation signal through measuring equipment to form a pretightening force-bolt deformation signal relation curve, and forming a calibration file to be stored in the equipment. The calibration file is shown in FIG. 2:
s4 (tightening process test 1): connecting the measuring equipment, wherein a special probe of the equipment passes through the bolt sleeve and is tightly attached to the bolt head signal induction sheet; and a torque-corner sensor is connected at the position of the bolt sleeve adapter, so that three signals of pre-tightening force, torque and corner are output to measuring equipment in real time.
S5 (tightening process test 2): and determining the target pretightening force of the bolt according to the yield point utilization coefficient and yield point pretightening force model data in the early design calculation process, tightening the bolt to the target pretightening force at a constant speed through tightening equipment, and recording the relation change curves of the torque-pretightening force and the corner-pretightening force in real time.
S6 (tightening process test 3): data processing, using the pre-tightening force as abscissa, the pre-tightening force and the rotation angle as left and right ordinates, generating a compound relation curve as shown in fig. 3, on the curve of rotation angle-pre-tightening force (red curve), using the target pre-tightening force FM(tightening end point) is taken as a starting point, a certain angle theta is preset, and after the preset angle theta is moved downwards on the vertical coordinate of the corner, the horizontal extension is carried out until the preset angle theta is intersected on the curve of the corner-pre-tightening force to obtain the initial pre-tightening force FbAnd vertically extending to a torque-pretightening force (black) curve, and obtaining a torque value which is the initial torque M through intersection.
Remarking: reference principles for setting the starting torque and the turning angle: the initial torque M is about 1/3 of the final torque Ma generally, and the pretightening force F corresponding to the initial torquebAbout target pretension force FMThe angle of rotation theta is typically 30 deg. or a multiple of 45 deg..
S7 (tightening process confirmation 1): after the bolt is loosened, the permanent deformation/stretching amount L of the bolt due to plastic deformation is measured1Determining the deformation length L of the bolt according to the structural design characteristics of the bolt, and calculating and determining the first-time tightening residual deformation rate of the bolt
The bolt is repeatedly tightened and disassembled for 2 times according to the tightening process determined by S6, and the residual deformation rate delta is measured and calculated2And Δ3。
S8 (tightening process confirmation 2): as shown in fig. 4, the bolts are tightened according to the tightening process determined in S6 to tighten the second bolt again, and the residual deformation rate is measured after the bolt pre-tightening force is loosened after the first tightening; and measuring and recording the residual deformation rate of the bolt during the second and third tightening, and confirming the consistency of the measured data and the first bolt. It is recommended that the number of the tightening confirmation bolts is more than or equal to 3.
S9: tightening process evaluation method
a) And (3) evaluating consistency of bolt pretightening force: the bolt pretightening force is required to be measured when the bolt is tightened for the first time confirmed by the tightening process, and the retested pretightening force and the axial force deviation ratio when the tightening process is formulated are required to be measured:
wherein FMTo target pretension force, FiAnd remeasured pretightening force for different bolts.
b) Evaluation of bolt residual elongation: key bolts of the engine are screwed in a plastic domain, and in order to avoid excessive elongation, the use times of the bolts are generally limited to 3 times; accordingly, the bolt is required to have a single-tightening residual deformation rate Δ1In the range of 0.2-0.6%, the total residual deformation rate delta of the bolt after three times of tighteningt＝Δ1+Δ2+Δ3Is less than 2 percent. However, the flywheel bolt is short and the pre-coating glue is coated on the thread part, so that the flywheel bolt is generally limited to be used only once, and the range of the residual deformation rate of the single-time tightening of the flywheel bolt is required to be 0.2% -1%.
Remarking: the length of the section with the smallest stress sectional area of the bolt is the largest after the section is stressed, and according to experience, the deformation of the bolt is mainly concentrated in the section. For bolts with equal rod diameters, the deformation length of the bolts is the part without screwing threads; for a bolt designed with a section of a thin rod (the sectional area of the thin rod is smaller than the sectional area of the thread stress), the deformation length of the bolt is the length of the thin rod.
In conclusion, the invention provides a method for establishing and evaluating a tightening process of a key bolt plastic domain of an engine, a test preparation stage is used for performing performance model and bolt tightening curve calibration on bolts in the same test batch, a preliminary tightening process is confirmed according to the corresponding relation of pre-tightening force, torque and a corner measured in the tightening process test stage, and the possibility of the tightening process is confirmed by measuring the pre-tightening force and the residual deformation rate of the bolts through tightening a plurality of boltsAnd reliability is realized, so that accurate control of bolt pretightening force and residual deformation rate is realized. According to the tightening process formulation method and the measured parameter processing method provided by the invention, the pretightening force, the torque and the corner of the bolt are monitored in real time in the tightening process and are converted into a composite relation curve taking the pretightening force as a horizontal coordinate, the pretightening force and the corner as a left vertical coordinate and a right vertical coordinate, and the target pretightening force F is taken as the target pretightening force on the corner-pretightening force curveM(tightening end point) as a starting point, presetting a certain angle theta, moving down the preset angle on the vertical coordinate of the corner, and horizontally extending to the curve of the corner-pre-tightening force to the initial pre-tightening force FbAnd vertically extending the torque value to a torque-pretightening force curve to obtain a torque value which is the initial torque M, so as to determine the torque-corner tightening process. The invention provides a reference principle formulated by a tightening process, namely that an initial torque M is about 1/3 of a final tightening torque Ma generally, and a pretightening force F corresponding to the initial torquebAbout target pretension force FMThe angle of rotation theta is typically 30 deg. or a multiple of 45 deg.. The invention provides a method for confirming and evaluating a screwing process, which is used for screwing a bolt according to a preset screwing process, measuring and recording the pretightening force and the single residual deformation rate of the bolt, and determining the consistency of the bolt screwing process. And (3) evaluating consistency of bolt pretightening force: the bolt pretightening force is required to be measured when the bolt is tightened for the first time confirmed by the tightening process, and the retested pretightening force and the axial force deviation ratio when the tightening process is formulated are required to be measured:
wherein FMTo target pretension force, FiAnd remeasured pretightening force for different bolts. Evaluation of bolt residual elongation: the key bolts of the engine are all screwed in a plastic domain, and in order to avoid excessive elongation, the number of times of using the bolts is generally limited to 3 times, and correspondingly, the residual deformation rate delta of one-time screwing of the bolts is required1In the range of 0.2-0.6%, the total residual deformation rate delta of the bolt after three times of tighteningt＝Δ1+Δ2+Δ3Is less than 2 percent. The flywheel bolt is short and the pre-coating glue is coated on the thread part, the flywheel bolt is generally limited to be used only once, and the range of the residual deformation rate of single-time tightening of the flywheel bolt is required to be 0.2% -1%. The invention provides a residual deformation rate analysis and meterCalculation method, percent set
For bolts with equal rod diameters, the deformation length of the bolts is the part without screwing threads; for a bolt designed with a section of a thin rod (the sectional area of the thin rod is smaller than the sectional area of the thread stress), the deformation length of the bolt is the length of the thin rod.
The above is only a preferred embodiment of the present invention, and certainly, the scope of the present invention should not be limited thereby, and therefore, the present invention is not limited by the scope of the claims.
Claims (10)
1. A method for formulating and evaluating a tightening process of a plastic region of a key bolt of an engine is characterized by comprising the following steps of:
1) measuring the yield strength of the bolt, and the yield point pre-tightening force and the friction coefficient in a tightening state;
2) keeping the clamping length of the bolt in an actual state, simulating bolt assembly on a bolt tightening machine, tightening a bolt connection system until the pretightening force exceeds the upper limit of the designed pretightening force range, simultaneously acquiring a pretightening force signal and a bolt deformation signal through measuring equipment to form a pretightening force-bolt deformation signal relation curve, and forming a plastic curve calibration file to be stored in the equipment;
3) connecting a measuring device, enabling a special probe to penetrate through a bolt sleeve to be tightly attached to a bolt head signal sensing piece, connecting a bolt sleeve adapter with a torque-corner sensor, and outputting three signals of pre-tightening force, torque and corner to the measuring device in real time by the signal sensing piece and the torque-corner sensor;
4) determining target pretightening force of the bolt according to the yield strength of the bolt, the yield point pretightening force and the friction coefficient in a tightening state which are obtained by early-stage measurement, tightening the bolt to the target pretightening force at a constant speed through tightening equipment, and recording the relation change curves of torque-pretightening force and corner-pretightening force in real time;
5) the pretightening force of the bolt tightening end point is taken as a target pretightening force FMAs a starting point, and screwing the bolt I along the direction of disassembling the bolt by taking the bolt at the starting pointFixing the angle theta to obtain the initial pretightening force F corresponding to the boltbAnd a starting torque M;
6) after the bolt is loosened, according to the measured bolt plastic curve, measuring the permanent deformation/stretching amount L of the bolt caused by plastic deformation1Determining the deformation length L of the bolt according to the structure of the bolt, calculating and determining the tightening residual deformation rate of the bolt, and re-tightening the corresponding bolt;
7) repeating the step 6) n times by using the same bolt according to the screwing process formulated in the step 5), and measuring and calculating to obtain the residual deformation rate delta n of each time;
8) reselecting a bolt, repeating the steps 5) to 7), recording the corresponding residual deformation rate of the bolt until m bolts are tested, and confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt;
9) and if the actual measurement axial force deviation rate and the residual deformation rate of the bolt meet the set conditions, judging that the set bolt tightening process is qualified.
2. The method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine according to claim 1, wherein in the step 5), the initial pre-tightening force F isbAnd the starting torque M is obtained by a specific process: generating a composite relation curve by taking the pretightening force as a horizontal coordinate, the torque and the corner as a left vertical coordinate and a right vertical coordinate, wherein the composite relation curve comprises a corner-pretightening force curve and a torque-pretightening force curve, and the target pretightening force F is taken as the corner-pretightening force curveMAs a starting point, the bolt is screwed for a certain angle theta along the direction of disassembling the bolt, and after the angle theta is moved downwards along the vertical coordinate of the corner, the horizontal extension is carried out until the angle theta is intersected on the curve of the corner-pretightening force to obtain an initial pretightening force FbAnd vertically extending to a torque-pretension force curve, and obtaining a torque value which is the initial torque M through intersection.
3. The method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine according to claim 1, wherein in the step 7), n is 2, i.e. the same bolt is repeatedly tightened and disassembled 3 times according to the tightening process, and the residual bolt is obtained through measurement and calculation for 3 timesResidual deformation ratios are respectively delta1、Δ2And Δ3；
In the step 9), the setting condition is that the total residual deformation rate delta of the bolt after three times of tighteningt＝Δ1+Δ2+Δ3＜2％。
4. The engine key bolt plastic zone tightening process establishing and evaluating method according to claim 3, characterized in that when the bolt belongs to a flywheel bolt, the set conditions are replaced by: and n is 0, and the single-tightening residual deformation rate of the bolt ranges from 0.2% to 1%.
5. The method for establishing and evaluating the tightening process of the plastic zone of the key bolt of the engine according to claim 1, wherein m is more than or equal to 3 in the step 8).
6. The method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine according to claim 1, wherein in the step 8), the concrete process for confirming that the measurement data of each bolt is consistent with the measurement data of the first bolt is as follows: the bolt pretightening force is required to be measured when the bolt is tightened for the first time confirmed by the tightening process, and the retested pretightening force is required to be measured and the axial force deviation rate when the tightening process is formulated
Wherein FMTo target pretension force, FiAnd remeasured pretightening force for different bolts.
7. The method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine according to claim 1, wherein in the step 1), the yield strength, the yield point pre-tightening force and the friction coefficient of the bolt in the tightened state are measured by sampling bolts of the same batch of test samples, and the number of the sampled test samples is more than 5.
8. The engine key bolt plastic zone tightening process establishing and evaluating method according to claim 1, characterized by further comprising the following steps before the step 2): and (3) modifying the bolt, wherein the specific modification process is to grind the end part of the bolt, so that the parallelism of the end surface of the bolt reaches 0.02, and the surface roughness reaches Ra0.8-1.6 mm.
9. The engine key bolt plastic zone tightening process establishing and evaluating method according to claim 1, characterized by further comprising the following steps before the step 2): the material and mechanical property, clamping length and surface flatness of the processing accompany type gasket and nut are the same as those of the simulated real object part.
10. The method for establishing and evaluating the tightening process of the plastic region of the key bolt of the engine according to claim 1, wherein in the step 6), the bolt tightening residual deformation rate is calculated and determined as follows:
wherein L is1The permanent set/elongation of the bolt due to plastic deformation, and L is the bolt deformation length.
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| CN113579716A (en) * | 2021-08-23 | 2021-11-02 | 深圳职业技术学院 | Engine bolt multi-shaft synchronous tightening test bed and control method |
| CN114018463B (en) * | 2021-09-23 | 2023-12-19 | 东风汽车集团股份有限公司 | Ballast type bolt axial force calibration measurement device and calibration method |
| CN114459743A (en) * | 2022-01-14 | 2022-05-10 | 东风柳州汽车有限公司 | Bolt abnormity detection method, device, equipment and storage medium |
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| JP2000326249A (en) * | 1999-05-14 | 2000-11-28 | Quanti Syst Kk | Fastening with bolt elongation control and method for determining work acceptance |
| JP4075852B2 (en) * | 2004-05-20 | 2008-04-16 | 三菱自動車工業株式会社 | Bolt fastening evaluation method |
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