CN110457797B - Tightening torque distribution method for bending moment bearing bolt for test - Google Patents
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Abstract
The application belongs to the field of structural static force and fatigue test, and particularly relates to a method for distributing tightening torque of a bending moment bearing bolt for test, which comprises the following steps: determining the distance from a fulcrum to the nearest adjacent bolt along the bottom surface of the bearing structure in the force loading direction and the distance between two adjacent bolts; wherein, a row of bolts in the vertical force loading direction is regarded as a bolt body; according to the moment load borne by the bearing structure and a moment balance equation, the load borne by each bolt body when the bolt body bears the maximum load is obtained; wherein, the load born by each bolt body is uniform and the same; calculating the tightening torque of each bolt body when the bolt body bears the maximum load; the tightening torque of each bolt is obtained. The tightening torque distribution method for the bending moment bearing bolts for the test is simple and feasible, implementation and operation in the test are facilitated, all bolts of the fixed stand column can be uniformly borne, and the bearing capacity of the whole structure is improved.
Description
Technical Field
The application belongs to the field of structural static force and fatigue test, and particularly relates to a method for distributing tightening torque of a bending moment bearing bolt for a test.
Background
General purpose columns are often used in structural static and fatigue tests as load bearing devices to balance the forces of the loading actuators. The bolts are used as connecting pieces for fixing the upright posts, and are locked by the same tightening torque, so that the upright posts are fixedly restrained, and all loads are borne. The column has high rigidity, so that compared with the bolt, the column can be considered as a rigid body, and the bearing structure consisting of the bolt and the column has the defects that the weak points are mainly concentrated on the bolt, and particularly when the column bears bending moment, the bearing force among the bolts is not uniform, so that some bolts bear main load, and the bearing capacity of the bearing structure as a whole is weakened.
Because the stand column is strong in rigidity, the stand column is often used for carrying out a bearing structure of transverse load, the stand column is fixed to a test platform through a bolt, and a test piece is loaded through a loading system. When the vertical column bears a transverse load, a large bending moment is generated on a structure consisting of the vertical column and the bolts, and the strength and the rigidity of the vertical column are usually enough, so that the weak part is mainly concentrated on the connecting bolts. Several bolts need to bear bending moment load generated by transverse load, the load distributed to each bolt is different, uniform pretightening force (locking torque) is generally adopted at present, no problem exists for small load, but in the case of large load, the unevenness of the bolts is obvious, and individual bolts bear main load to generate damage, so that the structure bearing capacity and the test safety are influenced.
Disclosure of Invention
In order to solve at least one of the technical problems, the application provides a tightening torque distribution method for a bending moment bearing bolt for a test.
The application discloses a tightening torque distribution method for a bending moment bearing bolt for a test, which comprises the following steps:
the method comprises the following steps that firstly, according to the arrangement mode of a preset number of bolts on a bearing structure, the distance from a bottom fulcrum of the bearing structure to an adjacent nearest bolt and the distance between two adjacent bolts in the force loading direction are determined; wherein, a row of bolts in the vertical force loading direction is regarded as a bolt body;
step two, obtaining the load born by each bolt body when the bolt body bears the maximum load according to the moment load borne by the bearing structure and a moment balance equation; wherein, the load born by each bolt body is uniform and the same;
and step three, calculating the tightening torque of each bolt body when the bolt body bears the maximum load.
And step four, dividing the obtained numerical value of the tightening torque of each bolt body by the number of the bolts in the row corresponding to the bolt body to obtain the tightening torque of each bolt.
According to at least one embodiment of the application, in the first step, the preset number of 6,6 bolts are arranged on the bearing structure in 3 rows, and the position points are A, B and C respectively, wherein the distance a from a fulcrum O to a bolt body A along the bottom surface of the bearing structure, the distance between the bolt body A and a bolt body B is B, and the distance between the bolt body B and a bolt body C is C;
in the second step, the bending moment load borne by the bearing structure is M, and a force moment balance equation is combined and obtained through the following formula (1):
F A a+F B (a+b)+F C (a+b+c)＝M (1)；
wherein, F A 、F B 、F C The bolt body is respectively the pulling force applied to the bolt body at the A, B and C positions.
According to at least one embodiment of the present application, in the second step, let F A ＝F B ＝F C ＝F 0 And obtaining the load formula (12) borne by each bolt body when the bolt body bears the maximum load as follows:
F 0 ＝M/(3a+2b+c) (12)。
according to at least one embodiment of the present application, in the third step, the bolt body tightening torques a, B and C T are obtained by the following equations (9), (10) and (11) 1A 、T 1B And T 1c ：
T 1C ＝0 (11)；
Reissue of order T 0 ＝KdF 0 And finally, when the bolt body bears the maximum load, the tightening torque of each bolt body is respectively as follows:
T 1C ＝0；
wherein K is a tightening torque coefficient; d is the bolt diameter.
According to at least one embodiment of the application, in the first step, the bearing structure is a rigid body, the deformation of the bearing structure is rigid body deformation, and the rigidity of the bearing structure at the mounting edge connected with the bolt is greater than the rigidity of the bolt.
According to at least one embodiment of the present application, in the first step, the bolt is an elastic body, and the rigidity of the elastic body is smaller than that of the load bearing structure.
According to at least one embodiment of the application, in the first step, when the bearing structure bears bending moment load, the deformation of the bottom surface of the bearing structure linearly increases along with the distance from the fulcrum.
The application has at least the following beneficial technical effects:
the tightening torque distribution method for the bending moment bearing bolt for the test is simple and easy to implement, is convenient to implement and operate in the test, enables all bolts of the fixed stand column to be uniformly loaded, and increases the bearing capacity of the whole structure.
Drawings
FIG. 1 is a front view of a bolt load bearing in one embodiment of a method of distributing torque for tightening a bending moment bearing bolt for testing of the present application;
FIG. 2 is a top view of a bolt load bearing in one embodiment of the present test bending moment bearing bolt tightening torque distribution method;
FIG. 3 is a schematic view of an embodiment of a method of distributing tightening torque for a bending moment bearing bolt according to the present application;
FIG. 4 is a schematic illustration of bolt deformation in an embodiment of the present test method for distributing tightening torque for a bending moment bearing bolt.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described are some, but not all embodiments of the disclosure. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present application and should not be construed as limiting the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
In the description of the present application, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present application and for simplifying the description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore should not be construed as limiting the scope of the present application.
The method for distributing the tightening torque of the bending moment bearing bolt for the test of the present application will be described in further detail with reference to fig. 1 to 4.
According to the tightening torque distribution method for the bending moment bearing bolt for the test, firstly, the actual conditions of the bolt and the upright post (namely, a bearing structure) need to be considered, and the following assumptions are made:
1) Assuming that the upright posts are rigid bodies, the deformation of the upright posts is rigid body deformation, and particularly, the rigidity of the upright posts at the mounting edge connected with the bolt is obviously far greater than that of the bolt;
2) Assuming that the bolts are much less than the column stiffness, it is considered as an elastomer to perform a line elasticity analysis;
3) Assuming that the bottom surface of the upright post takes the point O as a fulcrum, when the bottom surface bears the bending moment load, the deformation of the bottom surface linearly increases along with the increase of the distance from the point O;
4) Assuming that the bolts are loaded uniformly at maximum load, the bolts are loaded equally, and the total deformation (including that caused by bolt pretension) is the same.
Further, in one embodiment, the connecting structure commonly used in structural static force and fatigue tests is shown in fig. 1 and 2, and the bolts 4 fix the upright posts 3 on the test platform 5. The loading system is connected to the test piece 1 and the bearing upright post. The test piece is loaded through a loading system, and a loading structure consisting of the upright posts 3 and the bolts 4 balances the loaded load. A schematic view of the load bearing structure of the upright and the bolt for bearing bending moment load is shown in FIG. 3. The schematic diagram of the initial bolt pretension, the deformation after loading and the total deformation is shown in fig. 4.
Further, the tightening torque distribution method of the bending moment bearing bolt for the test comprises the following steps:
determining the distance from a fulcrum to the nearest adjacent bolt along the bottom surface of the bearing structure and the distance between two adjacent bolts in the force loading direction according to the arrangement mode of a preset number of bolts in the bearing structure; here, a row of bolts in the direction of vertical force loading is considered as a bolt body. For example, as shown in fig. 1 and 2, 6 bolts are arranged in 3 rows on the bearing structure, and two bolts are regarded as one bolt body.
Step two, obtaining the load born by each bolt body when the bolt body bears the maximum load according to the moment load borne by the bearing structure and a moment balance equation; wherein, the load born by each bolt body is uniform and the same.
Step three, calculating the tightening torque of each bolt body when the bolt body bears the maximum load;
and dividing the obtained numerical value of the tightening torque of each bolt body by the number of the bolts in the row corresponding to the bolt body to obtain the tightening torque of each bolt.
Specifically, in this embodiment, as shown in fig. 1 and fig. 2, the predetermined number of bolts is preferably 6,6, which are arranged in 3 rows on the bearing structure, and the positions are a, B, and C, respectively, where a distance a from a fulcrum O to a bolt body a along the bottom surface of the bearing structure, a distance B from the bolt body a to a bolt body B, and a distance C from the bolt body B to the bolt body C are provided.
Finally, when the bolt body bears the maximum load, the tightening torque of each bolt body can be obtained according to the following calculation formula:
from the moment balance equation:
F A a+F B (a+b)+F C (a+b+c)＝M (1)；
wherein, F A 、F B 、F C The tension of the bolt body at the positions A, B and C.
In order to ensure uniform distribution of bolt body load, the bolt body is made
F A ＝F B ＝F C ＝F 0 (2)；
From the deformation coordination equation:
ΔL 1A +ΔL 2A ＝ΔL 1B +ΔL 2B ＝ΔL 1C +ΔL 2C ＝ΔL 0 (3)；
from the stress strain equation:
F 0 ＝S 0 EΔL 0 /L 0 (4)；
the tightening torque formula yields:
T＝KF d d (5)；
from the previous assumptions and the deformation of the bolt body in fig. 4 under pretension, it is possible to obtain:
ΔL 1C ＝0 (8)；
setting the tightening torque of the bolt bodies A, B and C as T 1A 、T 1B And T 1C From equations (4) and (5), we can derive:
T 1C ＝0 (11)；
in addition, from equations (1) and (2) can be derived:
F 0 ＝M/(3a+2b+c) (12)；
let T 0 ＝KdF 0 Finally obtaining the tightening torque of the bolt body as T 1A 、T 1B And T 1C Are respectively as
T 1C ＝0；
Wherein, the letter meaning in the above formulas is as follows:
t-bolt body tightening torque;
k is the tightening torque coefficient, and the general processing surface and the lubrication-free time are 0.18-0.21;
d-bolt diameter;
F d -pre-tightening of the bolt body;
F 0 when the bolt body bears the maximum load, the load borne by each bolt body (the load borne by each bolt body is assumed to be uniform and the same);
m is the bending moment load borne by the bearing structure, and M = Fh;
ΔL 0 the deformation of the bolt when subjected to the maximum load;
L 0 -the length of the force-bearing part of the bolt;
h is the height from the tension loading point to the upper surface of the bearing structure.
It should be noted that the analysis of fig. 3 and 4 has been calculated by combining two bolts into 1 bolt body as shown in fig. 1 and 2, so that the calculated tightening torque is two bolts in the bolt distribution of fig. 1 and 2, the single bolt tightening torque should be half of the calculated tightening torque, and the like.
In summary, the simple calculation process (formula) of the method for distributing the tightening torque of the bending moment bearing bolt for the test of the application is as follows:
M＝Fh→；
T 0 ＝KdF 0 →；
for other bolt tightening torques using a plurality of bolts (an even number greater than 6), the calculation method of the tightening torque is also obtained by the above method.
In summary, the tightening torque distribution method for the bending moment bearing bolt for the test is simple and easy to implement, is convenient to implement and operate in the test, enables all bolts of the fixed stand column to be uniformly loaded, and increases the bearing capacity of the whole structure.
Further, in combination with the above method, the application also discloses a simple operation method for applying bolt pretightening force, which comprises the following steps:
the use of torqued wrenches to ensure tightening torque for each bolt is sometimes harsh in a laboratory environment. Usually, the spanner with the extension bar is used more frequently, and according to the characteristic that the tightening torque is proportional to the distribution distance of the bolts, only one maximum tightening torque needs to be known, and the tightening torques of other nuts can be applied in proportion. For example, a graduated extension bar wrench may be used, and after the maximum torque bolt is determined and tightened, the same force may be applied to the other bolts, but the position where the extension bar is held by hand is placed on the next scale. This is a simple and practical way of fixing.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (2)
1. The tightening torque distribution method of the bending moment bearing bolt for the test is characterized by comprising the following steps of:
determining the distance from a fulcrum to the nearest adjacent bolt along the bottom surface of the bearing structure and the distance between two adjacent bolts in the force loading direction according to the arrangement mode of a preset number of bolts in the bearing structure; wherein, a row of bolts in the vertical force loading direction is regarded as a bolt body;
step two, obtaining the load born by each bolt body when the bolt body bears the maximum load according to the moment load borne by the bearing structure and a moment balance equation; wherein, the loads born by the bolt bodies are uniform and the same;
step three, calculating the tightening torque of each bolt body when the bolt body bears the maximum load;
dividing the obtained numerical value of the tightening torque of each bolt body by the number of the bolts in the row corresponding to the bolt body to obtain the tightening torque of each bolt;
in the first step, 6,6 bolts are arranged on the bearing structure in 3 rows, and the position points are respectively A, B and C, wherein the distance a from a bolt body A to a bolt body B is B, and the distance C from the bolt body B to the bolt body C is C along the distance a from a fulcrum O on the bottom surface of the bearing structure to the bolt body A;
in the second step, the bending moment load borne by the bearing structure is M, and a force moment balance equation is combined and obtained through the following formula (1):
F A a+F B (a+b)+F C (a+b+c)＝M (1)；
wherein, F A 、F B 、F C The bolt body is respectively stressed by the tension of the A, B and C positions;
in order to ensure the uniform load distribution of the bolt body, the bolt body is made
F A ＝F B ＝F C ＝F 0 (2)；
From the deformation coordination equation:
ΔL 1A +ΔL 2A ＝ΔL 1B +ΔL 2B ＝ΔL 1C +ΔL 2C ＝ΔL 0 (3)；
from the stress strain equation:
F 0 ＝S 0 EΔL 0 /L 0 (4)；
the tightening torque formula yields:
T＝KF d d (5)；
the deformation generated by the pretightening force of the bolt body can obtain that:
ΔL 1C ＝0 (8)；
setting the tightening torque of A, B and C bolt bodies as T 1A 、T 1B And T 1C From equations (4) and (5), we can derive:
T 1C ＝0 (11)；
wherein K is a tightening torque coefficient; d is the bolt diameter, F d Pre-tightening the bolt body; Δ L 0 Deformation of the bolt when bearing the maximum load; l is 0 The length of the force bearing part of the bolt; h is the height from the tension loading point to the upper surface of the bearing structure;
in the second step, let F A ＝F B ＝F C ＝F 0 Obtaining the load formula (12) born by each bolt body when the bolt body bears the maximum load as follows:
F 0 ＝M/(3a+2b+c) (12)；
in the first step, the bearing structure is a rigid body, the deformation of the bearing structure is rigid body deformation, the rigidity of the mounting edge where the bearing structure is connected with the bolt is higher than the rigidity of the bolt, and the bolt is an elastic body and the rigidity of the bolt is lower than the rigidity of the bearing structure.
2. The tightening torque distribution method for the bending moment bearing bolt for the test according to claim 1, wherein in the first step, when the bearing structure bears the bending moment load, the deformation of the bottom surface of the bearing structure linearly increases as the distance between the bolt and the fulcrum increases.
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|---|---|---|---|---|
| CN103593542A (en) * | 2013-12-03 | 2014-02-19 | 北京航空航天大学 | Composite bolt connection structure pin load distribution determination method in consideration of intervals and tightening torque |
| JP2019105574A (en) * | 2017-12-13 | 2019-06-27 | 清水建設株式会社 | Load withstand performance testing machine and load withstand performance testing method |
| CN109977441A (en) * | 2017-12-28 | 2019-07-05 | 北京金风科创风电设备有限公司 | Method and device for determining stress of bearing bolt hole of wind generating set |
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| JP3835374B2 (en) * | 2002-08-09 | 2006-10-18 | マツダ株式会社 | Bolt fastening method and apparatus |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103593542A (en) * | 2013-12-03 | 2014-02-19 | 北京航空航天大学 | Composite bolt connection structure pin load distribution determination method in consideration of intervals and tightening torque |
| JP2019105574A (en) * | 2017-12-13 | 2019-06-27 | 清水建設株式会社 | Load withstand performance testing machine and load withstand performance testing method |
| CN109977441A (en) * | 2017-12-28 | 2019-07-05 | 北京金风科创风电设备有限公司 | Method and device for determining stress of bearing bolt hole of wind generating set |
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