WO2015154614A1

WO2015154614A1 - Double-bolt loose proof method

Info

Publication number: WO2015154614A1
Application number: PCT/CN2015/074549
Authority: WO
Inventors: 刘兴邦
Original assignee: 刘兴邦
Priority date: 2014-04-11
Filing date: 2015-03-19
Publication date: 2015-10-15
Also published as: CN105452686B; CN104976210A; CN105452686A

Abstract

A double-bolt loose proof method comprises: machining a screw hole or a drilling hole in a joint, providing a lock bolt and a fastening bolt with different diameters and opposite screwing directions; machining a central hole in the shank of the fastening bolt, passing the lock bolt through the central hole of the fastening bolt and connecting the lock bolt and the fastening bolt with the screw hole and a nut (including a reverse screwing nut) so as to achieve the anti-loose effect of the bolt.

Description

Double bolt anti-loose method

Technical field

The patent relates to a double bolt anti-loose method, the screw hole or the hole is machined on the coupling member, the external thread diameters of the locking bolt and the fastening bolt are different and the rotation direction is opposite, the center hole of the bolt body is fastened, and the bolt is locked Through the center hole of the fastening bolt body, the locking bolt and the fastening bolt and the screw hole or nut, and the "reverse rotation nut" are connected to achieve the bolt loosening effect.

Background technique

Bolt loosening mechanism:

1. Creep of the threaded secondary screw thread. According to the joint sub-relaxation creep test, the bolt pre-tightening force is reduced by nearly 10% within 24 hours after the nut is tightened, and the loss speed is slowed thereafter, and the nut is liable to loosen.

2. Looseness caused by depression of the bearing surface. Due to the large contact stress of the bearing surface of the bolt head or the nut, the surface of the coupling member has a plastic annular indentation. If plastic deformation continues to occur during use (referred to as bearing surface depression), the bolt elongation (generally referred to as the elastic elongation) and the pre-tightening force are reduced, and the nut is easily loosened and rotated.

3. Radial force is the main reason for loose bolting. Some scholars (especially the former West German G. Junker) have done a lot of tests on the bolting joints to apply the radial exciting force and the axial exciting force. The result is that the bolting by the axial force may be loose or not. Loose, but bolted by radial forces will definitely loosen when the radial excitation force reaches a certain level. After the bolting is pre-tightened, the nut will be in a radially expanded state under the radial expansion force of the nut generated by the pre-tightening force. When the external radial force is transmitted to a certain extent, the radial expansion force of the nut will be broken. Self-balancing, causing the nut to sway radially, so that the static friction coefficient of the screw thread in the tangential direction of the spiral decreases or becomes zero, the equivalent friction angle decreases or zero, and the loose torque is close to zero or negative. The nut will loosen and turn.

4. The influence of the gap between the internal thread and the external thread. The standard thread adopts single thread ordinary thread, the thread angle (1°40′～3°30′) is smaller than the equivalent friction angle of the screw pair (6.5°～10.5°), so the joint thread can satisfy the self-locking condition, at a certain Under the pre-tightening force, it is generally not loose. However, the thread pair is usually a clearance fit. Take the M30×2 fine thread as an example: the thread diameter of the bolt is 28.701mm, the thread diameter of the nut is 28.701mm, the average gap value of the thread connection is 0.1315mm, and the maximum gap value is 0.244mm. . Gap fit facilitates thread manufacturing and installation, but affects the anti-loose effect. In addition, the microscopic debris and particles on the surface of the thread are interspersed between the inner and outer nips, similar to the action of solid lubricants. Under the action of vibration, shock and alternating load, the threaded coupling pair inevitably has axial and radial turbulence. The frictional resistance between the inner and outer threads will instantaneously decrease or even disappear. This phenomenon is repeated many times, interacting, and eventually leads to loose coupling.

The current bolt locking methods are as follows:

1. Anti-loose of the top nut (double nut anti-loose structure): After the two nuts are tightened to the top, an additional opposing force is generated between them, and the top force and the pre-tightening force together generate a larger radial expansion of the nut. The force is far from the external radial force, so the nut is not easy to rotate, but it must be noted that this additional top force must be generated between the two nuts to achieve the anti-loose effect.

The force of the double nut anti-loose structure is more suitable for P1=0.2P and P2=0.8P. P1 is the pulling force of the screw to the lock nut (the nut on the non-bearing surface is called the lock nut), and P2 is the pulling force of the screw to the fastening nut (the nut on the working support surface is called the tightening nut), P is the screw Given the pre-tightening force, the tightening nut should be thicker and the lock nut should be thinner.

2, "reverse rotation double nut" (belonging to the top nut): the bolt is composed of two kinds of spirals, left-handed and right-handed, in the same section On the segment, there are both left-handed and right-handed threads. The tightening nut and the lock nut are two differently turned nuts. When using, tighten the tightening nut first, and then tighten the lock nut. In the case of vibration and impact, the tightening nut has a tendency to loosen, but since the loosening direction of the tightening nut is the tightening direction of the lock nut, the tightening of the lock nut prevents the tightening nut from loosening, resulting in tightness. The solid nut cannot be loosened.

3, "Spirit" thread: Schmidt nut and standard nut is different in the thread bottom diameter has a 30 ° cone surface, the external thread of the crest tightly wedges the internal thread root 30 ° cone surface, resulting The large radial locking force gives the nut a strong resistance to lateral vibration, which is the main cause of loose threads.

4, store more elastic deformation can achieve anti-loose: (1) increase the length of the bolt, the elastic elongation after bolt loading is proportional to the pre-tightening force and the bolt length, inversely proportional to the cross-sectional area of the bolt, the elasticity of the bolt The greater the elongation, the better the anti-loose effect; (2) the use of hydraulic locknuts, using the pre-tightening force of the bolt connection to make the high-strength bolt elastically deform in the axial direction and maintain the tensile state, relying on the elastic deformation of the bolt The resulting internal stress compresses the nut for anti-loosening purposes.

Others are spring washers, suspension nuts, self-locking nuts, longitudinal slotted nuts, adhesive anti-loose, punch riveting, etc.

When using ordinary nuts, theoretical analysis and tests have shown that the more the number of turns, the more uneven the distribution of the load. After the 8th to 10th turn, the thread is almost unloaded.

The elastic modulus of the carbon steel material from which the bolt is made is generally 200 to 210 × 10 ³ Mpa.

High-strength bolts refer to bolts with higher strength to reduce or simplify the size and structure of machinery or components. The tensile strength is generally above 700Mpa, and the quality is stable. However, high-strength bolts with a diameter of 30mm or more are not hard to be hardened during quenching. The quality is unstable and the working stress should be reduced during use. When using high-strength bolts, they have the following characteristics:

1. The coupling member is subjected to alternating load to generate vibration. To obtain a small bolt deformation stiffness, the contact surface should be made of high-strength and small-sized bolts, such as 10.9 and 8.8 (10.9 means tensile strength 1000 MPa, The yield strength σs is 90% of the tensile strength).

2. The reason for the excessive alternating stress is that the pre-tightening force is too small and the residual pre-tightening force is large, so the axial pre-tightening force always loads the bolt to the elastic limit of 90%. Or the pre-tightening force of the bolt is less than 80% of the material's yield limit of the bolt, and try to take a higher value. The yield limit is the yield strength σs, which has the same meaning.

3. In the bolt connection, the bolt is made of a material with large deformation, and the material to be connected is made of a relatively rigid material, so that the deformation line of the bolt is relatively flat, and the deformation line of the joint is steep, and the magnitude of the stress is Become smaller. When the strength of the bolt is constant, the magnitude of the force in the bolt can be reduced, which helps to improve the life of the bolt.

The high-strength bolt connection must adopt a large pre-tightening force, and the general pre-tightening force is 70%-81.2% of the yield strength σs of the bolt material. When testing the lateral vibration anti-loose effect on the SPS-Anbiano transverse vibration tester in the UK, it was found that when the axial pre-tightening force of the bolt was increased from 0.25 σs to 0.45 σs, the anti-loose effect was improved by 13.2 times. When the preload force reaches 0.75σs, the anti-loose effect will be greatly improved.

The control methods for bolt preload are:

1. Control the preload by tightening torque. The torque value displayed by the torque wrench controls the pre-tightening force of the coupled member, and the operation is simple and intuitive, and the error is about ±25%.

2. Control the preload by the nut angle. The angle of rotation when the nut (or bolt) is tightened is approximately proportional to the sum of the bolt elongation and the looseness of the tightened member, and thus a method of achieving a predetermined preload force at a predetermined rotation angle can be employed. When initially tightening, first determine the ultimate torque, screw the bolt (nut) all the way to the limit torque, and then turn it through a predetermined angle. The easiest way to measure the nut angle is to engrave a zero line and measure the nut angle by the rotation of the nut. The measurement accuracy of the nut angle can be controlled within 10 ° ~ 15 °. In general, the preload force error is approximately ±15%.

3. Control the preload by the bolt elongation. The pre-tightening force can be controlled by the elongation of the bolt to obtain high control precision, and is widely used as a pre-tightening force control method for bolt flange connection in important occasions. If the measurement is correct, the preload force error is about ± 5%. Bolt elongation calculation example:

Taking the 8.8-level M30×2 threaded joint as an example, when the solid bolt diameter is D=30mm, the effective tensile length of the screw is L=65mm, and the nut is tightened with a torque of 1450Nm. When the bolt pre-tightening force P=269kN, the elongation of the bolt ΔL is :

ΔL=P×L/(E×S)=P×L/[E×3.14×(D/2) ² ]

=269×10 ³ ×65×10 ^-3 /[210×10 ⁹ ×3.14×(30×10 ^-3 /2) ² ]=0.118mm

Where P-solid bolt preload, N

L-screw effective tensile length, m

Elastic modulus of E-bolt material (high strength bolt takes 210×10 ³ Mpa), N/m ²

S-bolt cross-sectional area (ie the cross-sectional area of the bolt body), m ²

The stress σ of the bolt is: σ=P/S=269×10 ³ /[3.14×(30×10 ^-3 /2) ² ]=381Mpa

The yield strength of the 8.8 bolt is σs=800×0.8=640Mpa, and σ/σs=381/640=0.595≈0.6.

If the elastic modulus of the bolt remains the same, only the effective tensile length or stress of the bolt changes, and the elastic elongation will follow a linear change in the effective tensile length or stress (within the elastic limit of the bolt material).

4. Control the pre-tightening force according to the tightening torque and the nut angle. First apply a certain torque to the fastener, then turn the nut through a certain angle to check whether the final torque and the rotation angle are satisfied, so as to avoid insufficient pre-tightening or pre-tightening. The advantage of this control method is that the information given by the tightening torque and the nut angle can precisely control the bolt pre-tightening process and the pre-tightening force, and can find the tightening or over-tightening that may occur during the installation process. This is used alone. Torque control or corner control cannot be achieved.

5. The method of measuring stress by using a resistance strain gauge mainly includes two measuring methods: a force measuring bolt and a ring gasket. The force-measuring bolt is a sensor that directly replaces the existing bolt and can measure the bolt pre-tightening force, which can be accurate to kilograms. The annular gasket is measured by indirectly measuring the pressure at the nut by an annular washer sensor (load cell) added to the head of the bolt to obtain the preload of the bolt. In addition, the strain gauge can be placed on the unthreaded part of the bolt, and the tensile strain can be measured and controlled by the resistance strain gauge. The preload force error can be controlled within ±1%.

Ordinary bolts refer to bolts with low tensile strength, such as 3.6 and 5.6. The preload is affected by the actual conditions. For example, find the higher value of the preload as a reference:

The pre-tightening force of the 3.6-class M16 bolt is generally 20400N, and the stress σ is:

σ=P/S=20.4×10 ³ /[3.14×(16×10 ^-3 /2) ² ]=101.5Mpa

The yield strength of 3.6 bolts is σs=300×0.6=180Mpa, σ/σs=101.5/180=0.564≈0.56.

The preload of the 3.6-class M30 bolt is generally 73500N, and the stress σ is:

σ=P/S=73.5×10 ³ /[3.14×(30×10 ^-3 /2) ² ]=104.0Mpa

σ/σs=104.0/180=0.578≈0.58

The pre-tightening force of the 5.6-class M16 bolt is generally 34000N, and the stress σ is:

σ=P/S=34×10 ³ /[3.14×(16×10 ^-3 /2) ² ]=169.2Mpa

The yield strength of 5.6 bolts is σs=500×0.6=300Mpa, σ/σs=169.2/300=0.564≈0.56.

The preload of the 5.6-class M30 bolt is generally 122000N, and the stress σ is:

σ=P/S=122×10 ³ /[3.14×(30×10 ^-3 /2) ² ]=172.7Mpa

σ/σs=172.7/300=0.576≈0.58

Therefore, the normal pre-tightening force or pre-tightening stress of ordinary bolts generally does not exceed 0.58σs (for the calculation of this specification).

When the pre-tightening force of the ordinary bolt reaches 0.78σs, the groove bottom of the external thread of the bolt begins to break, so 0.78σs can be used as the reference value of the maximum preload or the maximum preload stress.

When the bolt is connected under the impact load, the stress response of the bolt changes with the preload force. When the pre-tightening stress of the shear bolt is about 40% of the yield limit of the material, the strength is maximum; the strength of the tension bolt will follow The pre-tightening force is weakened; at the same time, the bolts subjected to shearing and stretching have the highest strength when the pre-tightening stress is about 40% of the yield limit of the material.

Most of the current bolt failures are caused by the plastic deformation of the thread by excessive external force, which can be considered to be caused by excessive tightening torque (pre-tightening force).

China Patent No. CN1087848 "Method for Manufacturing High-strength Nuts" (promulgated on June 15, 1994), announced a method for manufacturing high-strength nuts. The main technical solution is: the pre-order equipment of the cold heading machine is medium frequency induction. Heating furnace, the production process is: (1) heating; (2) 镦 shape; (3) tapping screw; (4) heat treatment.

The metric thread is divided into coarse teeth (60°) and fine teeth (60°). The pitch of the external thread of the coarse teeth M30 bolt is 3.50mm, the depth of the thread is 1.75mm, and the diameter of the bottom of the thread (ie the diameter of the bottom of the thread, referred to as the bottom diameter) ) is 26.50mm.

China National Standard (GB/T 923-2009) "Hexagonal Cap Nut", suitable for nuts with one side hemispherical sealing structure.

China National Standard (GB/T 6171-2000) "1 type hex nut fine teeth", M30 × 2 hex nut thickness Mmax = 25.6mm, Mmin = 24.3mm.

China National Standard (GB/T 6176-2000) "2 type hex nut fine teeth", M30 × 2 hex nut thickness Mmax = 28.6mm, Mmin = 27.3mm.

China National Standard (GB/T 5785-2000) "Hexagon head bolt fine teeth", M30 × 2 hexagon bolt head nominal height K = 18.7mm.

When bolts are connected, there is a permissible safety factor, which is generally 1.5 to 2.5 times (calculated according to the stress amplitude).

Summary of the invention

In order to overcome the phenomenon that the existing bolts are prone to loosening, the technical solution adopted in the patent solves the problem is to adopt the "double bolt anti-loose method", which is described as follows:

1. The coupling member is machined with two screw holes of different diameters and oppositely rotating threads on the axial center line of the same center, which are called fastening screw holes and locking screw holes, fastening the center hole of the bolt body, fastening bolts And the fastening screw hole is coupled, the locking bolt is coupled through the central hole of the fastening bolt body and the locking screw hole to jointly fasten the coupling member;

2. The hole is made in the coupling member. The diameter of the internal thread of the lock nut and the fastening nut is different and the rotation direction is opposite. The fastening bolt and the fastening nut are coupled, and the locking bolt passes through the center hole of the fastening bolt body and the lock nut. Coupling to jointly fasten the coupling member;

3. The gasket and the lock nut and the fastening nut are welded or integrated into a “reverse rotation nut”. The “reverse rotation nut” is provided with two sets of internal threads with different diameters and opposite directions, fastening bolts and “ The reverse rotation nut is coupled, and the locking bolt is connected through the center hole of the fastening bolt body and the "reverse rotation nut" to jointly fasten the coupling member;

The technical point of the double bolt anti-loose method is that the fastening bolt and the locking bolt are two independent bolts, fastening bolts and locking The diameter of the external thread of the bolt and the direction of rotation are different. The diameter of the internal thread of the lock nut and the fastening nut and the direction of rotation are different. The center hole of the fastening bolt body is used to assemble the locking bolt, and the "reverse rotation nut" appears. The integration of the lock nut and the fastening nut is made possible. In the background art, there are three cases in which the lock nut and the fastening nut are integrated:

1, equivalent to a nut, can not play the role of anti-loose, such as the top nut (the rotation of the two nut threads is the same);

2, can not be disassembled after use and welding, can only be used once, such as "reverse rotation double nut" (the opposite direction of the rotation of the two nut threads);

3. It cannot be used after integration, such as “reverse rotation double nut”.

Locking bolts and fastening bolts can be selected according to the material, processing technology and appropriate pre-tightening force. Since the two sets of reverse-rotating threads have an "interlocking" effect, the nut or bolt cannot be rotated to achieve the anti-loose effect. It is also suitable for occasions where the coupling member is required to be pivoted around the fastening bolt.

The beneficial effect of the patent is that the reliability of the bolt connection can be improved, and the utility model can be used under the condition of lower pre-tightening force to extend the life of the bolt, and some parts can adopt standard parts, which can be applied to various occasions, especially the more important joints. .

DRAWINGS

The patent is further described below in conjunction with the drawings.

Figure 1 is a cross-sectional view showing the structure of a bolt and a coupling. The axial centerline of the same center of the left coupling member is machined with two screw holes of different diameters and opposite directions of rotation. The large diameter screw hole is called a fastening screw hole, and the small diameter screw hole is called a locking screw hole. Holes (drilled or reamed), and the center of the rod body of the bolt (through hole structure). For example, the shape of the head of the fastening bolt is different from the hexagon. The shape of the head of the locking bolt is exemplified by a hexagon. The fastening bolts are fastened to the fastening bolts, and the fastening bolts are fastened through the central hole of the fastening bolt body and the locking screw holes, and the locking bolt heads are pressed against the fastening bolt heads. The effective tensile length of the locking bolt screw is B, and the effective tensile length of the fastening bolt is the thickness of the right coupling. If the thickness of the left coupling member becomes small, it becomes a through-hole structure.

Figure 2 is a right side view of Figure 1 (with the coupling omitted).

Figure 3 is a cross-sectional view showing the first structure of the bolt, the nut and the coupling. Both couplings are drilled, using fastening bolts, locking bolts, fastening nuts, lock nuts and flat washers (one type of gasket) for coupling, fastening bolts and fastening nuts to press the coupling, locking The nut is pressed against the fastening nut by a flat washer. This structure is similar to the "reverse rotation double nut" with a flat pad. The shape of the fastening nut and the lock nut is an example of a hexagon. The rest is the same as in Figure 1.

Figure 4 is a left side view of Figure 3 (with the coupling omitted). The circumscribed circle of the outer nut of the lock nut is equal to the inscribed circle of the outer hexagon of the fastening nut, and the outer diameter of the flat washer is equal to the inscribed circle of the outer hexagon of the fastening nut.

Figure 5 is a cross-sectional view showing the second structure of the bolt, the nut and the coupling. The flat pad and the lock nut and the fastening nut are welded together (to prevent excessive deformation, spot welding along the circumference). The rest is the same as in Figure 3.

Figure 6 is a cross-sectional view showing the third structure of the bolt, the nut and the coupling. After the lock nut and the flat pad are integrated, they are welded with the fastening nut. The tightening nut and the flat washer can also be integrated and welded with the lock nut. The rest is the same as in Figure 3.

The left side view of Fig. 6 is the same as Fig. 4 (the solder joint is removed).

Figure 7 is a cross-sectional view of the "National Cap Nut" of the Chinese National Standard (GB/T 923-2009). G1 is the length of the undercut, and the M24×2 hex cap nut G1max is 10.7 mm in the first series and 7.3 mm in the second series.

If the shape of the outer hexagon becomes circular (for example, it becomes a circumcircle or an inscribed circle of the outer hexagon, but the diameter should be at least not less than The inner circle of the outer hexagon, called the "round nut", can also be changed to other outer polygon angles, so it can be divided into a round cap nut and an outer polygon cover nut (including a hexagonal cap nut). In this specification, they are collectively referred to as "cap nuts."

Figure 8 is a left side view of Figure 7.

Figure 9 is a cross-sectional view showing the structure of the lock nut, the flat washer and the fastening nut, which is referred to as a "reverse rotation nut".

The thread at the lock nut in the "reverse nut" is called the locking thread (left small diameter thread) and the thread at the fastening nut is called the fastening thread (large diameter thread on the right). The inner distance between the locking thread and the fastening thread may take G1max = 10.7 mm as a reference value.

Figure 10 is a cross-sectional view showing the fourth structure of the bolt, the nut and the coupling. The "reverse rotation nut" is coupled with the coupling member and the bolt, and the left side of the "reverse rotation nut" is a through hole structure. The rest is the same as in Figure 3.

Figure 11 is a left side view of Figure 10 (the coupling is omitted). The shape of the lock nut becomes circular (for example, the circumcircle or inscribed circle of the outer nut of the lock nut, but the diameter should be at least not less than the inscribed circle of the outer hexagon), and the diameter is equal to the outer diameter of the lock nut. The outer circle of the outer ring and the shape of the outer hexagon at the fastening nut are called a single outer hexagon "reverse rotation nut".

If the shape of the fastening nut becomes circular, the shape of the outer hexagon at the lock nut does not change, which is also called the single-hexagon "reverse rotation nut", so the single-hexagon "reverse rotation nut" is divided into large Hexagon "reverse rotation nut" and small hexagon "reverse rotation nut". The large hexagonal "reverse rotation nut", that is, the shape of the lock nut is round, the shape of the outer hexagon at the fastening nut is unchanged; the small hexagonal "reverse rotation nut", that is, the shape of the fastening nut is round, the lock The shape of the outer hexagon at the nut is unchanged. If the shape of the fastening nut and the fastening nut are rounded, it is called a circular "reverse rotation nut". If the shape of the outer hexagon at the fastening nut and the fastening nut does not change, it is called double-hexagon "reverse rotation nut", and the left view is the same as FIG.

Figure 12 is a cross-sectional view showing the fifth structure of the bolt, the nut and the coupling. The left side of the "reverse rotation nut" is a hemispherical sealing structure called a "reverse rotation nut". Any such that the nut does not expose the screw hole is collectively referred to as a sealing structure.

Figure 13 is a cross-sectional view showing the sixth structure of the bolt, the nut and the coupling. The lock nut presses the tightening nut through a "bowl-type" gasket (another type of gasket) that is similar in construction to a "reverse-rotating double nut" with a "bowl-type" gasket. The locking bolt head, the lock nut and the fastening nut are hexagonal. The rest is the same as in Figure 3.

"Bowl type" gaskets and flat pads have the same purpose and are collectively referred to as gaskets.

Figure 14 is a cross-sectional view showing the seventh structure of the bolt, the nut and the coupling. The lock nut, the "bowl type" gasket and the fastening nut are integrally formed into a double outer hexagon "reverse rotation nut", and the inner distance between the locking thread and the fastening thread can take G1max=10.7mm as a reference value. The rest is the same as in FIG.

If the plugging type "reverse rotation nut" is used, it is basically the same as FIG.

Figure 15 is a left side view of Figure 14 (without the coupling). The shape of the "reverse rotation nut" lock nut becomes circular and becomes a large hexagonal "reverse rotation nut". If the shape of the fastening nut becomes circular, the shape of the outer hexagon at the lock nut does not change, and it becomes a small hexagonal "reverse rotation nut".

Figure 16 is a cross-sectional view showing the eighth structure of the bolt, the nut and the coupling. The locking bolts and the fastening bolts are stud bolts, and a rigid sleeve is used between the two couplings for limiting. The rest is the same as in FIG.

Figure 1. 1. Left coupling, 2. Right coupling, 3. Fastening bolt, 4. Locking bolt

Figure 3. 5. Lock nut, 6. Flat washer, 7. Fastening nut

Figure 8. 8. Solder joints

Figure 9. Reverse rotation nut

Figure 10. "Bowl type" gasket

Figure 16. The rigid sleeve

detailed description

In the embodiment of Figure 1, after the screw holes of the left coupling (1) and the drilling of the right coupling (2) are aligned, the fastening bolts (3) pass through the drilling and left coupling of the right coupling (2). The fastening screw holes of the piece (1) are connected, and the fastening bolts (3) are tightened to achieve the required pre-tightening force. The locking bolt (4) penetrates into the central hole of the fastening bolt (3), and is coupled with the locking screw hole of the left coupling member (1), and tightens the locking bolt (4) to achieve the required pre-tightening force, and the locking bolt ( 4) The head of the head is pressed against the head of the fastening bolt (3). The length of the rod of the fastening bolt (3) and the locking bolt (4) must be strictly controlled to prevent screwing into the bottom of the screw hole. Since the locking screw hole and the fastening screw hole adopt the reverse rotation thread, the left coupling member (1) cannot be rotated due to the "interlocking" effect, and becomes a double-group thread force compared with the single bolt, and can also be improved. The joint strength of the thread. Description of the principle of anti-loose: The left coupling (1) cannot be rotated due to the "interlocking" action of the reverse rotation thread. In the case of vibration and impact, the fastening bolt (3) tends to loosen, but due to the fastening bolt The retracting direction of (3) is the tightening direction of the locking bolt (4), and the tightening of the locking bolt (4) prevents the fastening bolt (3) from loosening, and the fastening bolt (3) cannot be loosened. As long as the thread of the component meets the requirements, it can be repeatedly disassembled without affecting the coupling performance. If the thickness of the left coupling member (1) becomes small and the round hole or the internal thread is exposed, it becomes a through-hole structure and does not affect the coupling performance.

If the right coupling member (2) is required to be pivoted around the fastening bolt (3), a gap must be provided between the two coupling members or between the right coupling member (2) and the head of the fastening bolt (3). The fixing bolt (3) needs to grasp the depth of screwing into the fastening screw hole, leaving a proper clearance, and then screwing in the locking bolt (4) and pre-tightening, the anti-loose effect is better than using a single bolt.

In the embodiment of Figure 3, after the drilling of the left coupling (1) and the right coupling (2) is aligned, the fastening bolt (3) is coupled through the drilled hole and the fastening nut (7) and pre-tensioned to the coupling. For tightening, tighten the locking bolt (4) into the center hole of the fastening bolt (3), attach the flat washer (6), and connect with the lock nut (5). The lock nut (5) is tightly fastened. The nut (7), the lock nut (5) and the tightening nut (7) can be considered to achieve "interlocking", and the anti-loose principle is the same as the "reverse rotation double nut" in the background art. Tightening bolt (3) The length of the rod body should be strictly controlled to prevent the left end of the rod body from pressing against the lock nut (5), so that the lock nut (5) cannot press the tightening nut (7). The outer dimensions of the lock nut (5) should match the tightening nut (7) and the flat washer (6). The outer diameter of the lock nut (5) can be slightly smaller than the tightening nut (7), preferably the lock nut. (5) The circumcircle of the outer hexagon is equal to the inscribed circle of the outer hexagon of the fastening nut (7). The inner diameter of the flat washer (6) should be slightly larger than the diameter of the fastening bolt (3). The outer diameter can be equal to the inner cut circle of the outer hexagon of the fastening nut (7). The thickness should be larger than the exposed length of the fastening bolt (3) and leave appropriate. The gap, the exposed length is the sum of the length of the fastening bolt (3) and the thickness of the two couplings and the fastening nut (7). The lock nut (5) can be replaced with a nut with a sealing structure, such as a cap nut. The rest are the same as the embodiment of Fig. 1.

If the fastening bolt and the lock bolt use the stud bolt, the structure of the right end of the fastening bolt and the lock bolt is the same as that of the left end nut, and the bolt is used to fasten the joint.

In the embodiment of Fig. 5, the lock nut (5), the flat washer (6) and the fastening nut (7) are welded together (can be welded along the periphery), and the nut cannot be rotated, which is advantageous for preventing looseness and not affecting. Disassembly. The rest are the same as the embodiment of Fig. 3.

In the embodiment of Fig. 6, after the lock nut (5) and the flat washer (6) are integrally formed, the fastening nut (7) is welded, or the fastening nut (7) and the flat washer (6) are integrally formed, and the lock is completed. Tight nut (5) is welded. If the cap nut is used instead of the lock nut (5), the flat pad (6) is made in one piece, welded to the fastening nut (7), or the fastening nut (7) and the flat pad (6) are integrated. After that, welding with the cap nut is beneficial to prevent the nut from loosening and does not affect the disassembly. The rest are the same as the embodiment of Fig. 5.

In the embodiment of Fig. 10, the reverse rotation nut (9) is a double outer hexagon structure, and the fastening bolt (3) and the locking bolt (4) are screwed into the reverse rotation nut (9) to fasten the coupling member. As long as it is not manually disassembled, the reverse rotation nut (9) cannot be loosened. The rest are the same as the embodiment of Fig. 3.

If the coupling is required to be able to rotate about the fastening bolt (3), between the two couplings or between the right coupling (2) and the head of the fastening bolt (3), the left coupling (1) and the opposite A clearance shall be provided between the turning nut (9). The tightening bolt (3) shall have a depth to be screwed into the counter-rotating nut (9), leaving a proper clearance, and the locking bolt (4) is screwed into the counter-rotating nut ( 9) and pre-tightening, the anti-loose effect is better than using a single bolt and a counter-nut.

In the embodiment of Fig. 12, the counter-rotating nut (9) of the hemispherical sealing structure can prevent rain, snow, dust and the like from entering the internal thread, thereby protecting the thread and increasing the service life under more severe natural conditions. The rest are the same as the embodiment of Fig. 10.

In the embodiment of Fig. 13, the lock nut (5) is pressed against the fastening nut (7) by the "bowl type" gasket (10), and the main function of the "bowl type" gasket (10) is to ensure a small outer shape. The lock nut (5) can press the fastening nut (7) with a relatively large outer dimension, and the "bowl type" gasket (10) should have sufficient rigidity, otherwise the joint performance will be affected. A proper clearance should be left between the “bowl” gasket (10) and the left end of the fastening bolt (3) rod to prevent the left end of the fastening bolt (3) against the “bowl” gasket (10). The head and tail of the locking bolt (4) can be used interchangeably, and the head of the fastening bolt (3) can be pressed using the lock nut (5). The rest are the same as the embodiment of Fig. 3.

The lock nut (5), the "bowl type" gasket (10) and the fastening nut (7) can be welded for use in one piece, as in the embodiment of Figure 5; the lock nut (5) and the "bowl type" gasket ( 10) In one piece, welded with the fastening nut (7), or the fastening nut (7) and the "bowl type" gasket (10) are integrated, and the lock nut (5) is welded, and the embodiment of Fig. 6 the same.

In the embodiment of Fig. 14, the lock nut (5), the "bowl type" spacer (10) and the fastening nut (7) are integrally formed as a counter-rotating nut (9), and the rest are the same as in the embodiment of Fig. 13.

If the coupling is required to be pivoted about the fastening bolt (3), the method of use associated with the embodiment of Fig. 10 is the same. If the reverse rotation nut (9) is a closed structure, it is the same as the embodiment of Fig. 12.

In the embodiment of Fig. 16, the rigid couplings (11) are used for limiting between the two coupling members, and the fastening bolts (3) and the locking bolts (4) use stud bolts, the bolt length is increased, and more elastic deformation is stored. Yes, the anti-loose effect will be better. The rest are the same as the embodiment of Fig. 13.

After the tightening bolt (3) is pre-tightened, use the tool to lock the fastening bolt (3) and the fastening nut (7) or the reverse rotation nut (7) when tightening the locking bolt (4) or the lock nut (5). 9) Prevent the pre-tightening force from being lowered due to the reversal of the fastening bolt (3) or the fastening nut (7), which affects the fastening effect.

If the coupling member rotates around the fastening bolt (3), the fastening bolt (3) is subjected to compressive stress after the coupling, the locking bolt (4) is subjected to tensile stress, and the locking bolt (4) should be pre-tightened. Do not withstand excessive stress.

When removing the coupling, first remove the locking bolt (4) or the lock nut (5), and then remove the fastening bolt (3) or the fastening nut (7), the reverse rotation nut (9) and other components.

When removing the round counter-rotating nut (9) or the cap nut, use a tool such as a pipe wrench to lock the round counter-rotating nut (9) or the cap nut, and then remove the locking bolt (4). Then remove the fastening bolt (3) and take out the round reverse rotation nut (9); or remove the dome nut first, remove the locking bolt (4), then remove the fastening nut (7), take out the tight Solid bolt (3).

After the reverse rotation nut (9) is made into a double hex or a small hexagonal shape, it can be locked by using a shallow hexagon socket. Remove the lock bolt (4) and the fastening bolt (3) against the nut (9). In fact, the flat washer (6) or the "bowl type" washer (10) and the lock nut (5) and the fastening nut (7) have become the double-hexagon reverse-rotating nut (9) of the welded structure. Similarly, after the lock nut (5) and the flat washer (6) or the "bowl type" washer (10) are integrated, the welding nut (7) is welded, or the nut (7) and the flat washer are fastened ( 6) Or the "bowl type" gasket (10) is made in one piece, welded with the lock nut (5), and also becomes the double-hexagon reverse-rotating nut (9) of the welded structure. If the lock nut (5) and the flat washer (6) or the "bowl type" washer (10) are made in a circular shape and welded with the fastening nut (7), it becomes a large hexagonal reverse nut of the welded structure. (9); the fastening nut (7) and the flat washer (6) or the "bowl type" washer (10) are all made circular and integrated with the lock nut (5) to become a small hexagonal reverse of the welded structure. Screw the nut (9). If the shape of the fastening nut (7) and the lock nut (5) are round, and the flat pad (6) or the "bowl type" gasket (10) is welded, it becomes a circular reverse nut of the welded structure. (9); If the cap nut is used instead of the lock nut (5), it becomes the plugged reverse nut (9) of the welded structure. Therefore, the reverse rotation nut (9) can be divided into the following types:

1. Welded anti-rotation nut (9)

2, integral reverse rotation nut (9)

3, single hex reverse rotation nut (9)

4, double hex reverse rotation nut (9)

5, round reverse rotation nut (9)

6, through-hole reverse rotation nut (9)

7, sealed reverse rotation nut (9)

Each of the counter-rotating nuts (9) can be divided into different shapes and structures:

Welded anti-rotation nut (9) can be divided into through-hole type, sealed type, large hexagon, small hexagon and round shape, in addition to lock nut (5), flat pad (6) or "bowl type" pad The "3 in 1" structure of the piece (10) and the fastening nut (7) is welded; the lock nut (5) and the pad (6) or the "bowl type" spacer (10) are integrally formed, and the fastening nut is (7) The "2 in 1" structure of the welding, the "2 in 1" structure also includes a fastening nut (7) and a flat pad (6) or a "bowl type" gasket (10), and a lock nut ( 5) The form of welding.

The integral reverse rotation nut (9) can be divided into a through hole type, a sealing type, a large hexagon, a small hexagon and a circular shape.

The single hex reverse rotation nut (9) can be divided into a through hole type, a sealing type, a welded type, an integral type, a large hex and a small hex.

The double hex reverse rotation nut (9) can be divided into a through hole type, a sealing type, a welded type and a unitary type.

The circular counter-rotating nut (9) can be divided into a through-hole type, a sealing type, a welded type and a monolithic type.

Through-hole reverse-rotating nut (9) can be divided into welded, integral, large hexagon, small hexagon and round.

The sealed reverse rotation nut (9) can be divided into welded type, integral type, large hexagon, small hexagon and round shape.

The single hex reverse rotation nut (9) can also be other outer polyhedral angles, collectively referred to as "single outer polyhedral angle" reverse rotation nut (9).

The double hex reverse rotation nut (9) can also be other outer polyhedral angles, collectively referred to as "double outer polygon angle" reverse rotation nut (9).

When the solid bolt becomes the fastening bolt (3) and the locking bolt (4), the locking bolt (4) and the fastening bolt (3) mainly rely on the "interlocking" action of the reverse rotation thread to prevent loosening. Under the double action of "interlocking" and pre-tightening force, it is impossible to loosen the loosening. The main role of the pre-tightening force becomes "joining", which overcomes the shortage of some existing bolts simply relying on increasing the pre-tightening force to prevent loosening. The tightening bolt (4) and the fastening bolt (3) can no longer require too much pre-tightening force; in addition, according to the background art, "the anti-loose effect is increased by 13.2 times when the axial pre-tightening force of the bolt is increased from 0.25 σs to 0.45 σs. ", get "when bolt When the axial pre-tightening force is increased from 0.25 σs to 0.4 σs, the anti-loose effect is increased by about 10 times, so whether it is a high-strength bolt or a normal bolt, if the fastening bolt (3) and the locking bolt (4) are pre-tightened The force is controlled at 0.4σs, which can improve the service life and ensure the maximum strength (when subjected to impact load), and the double function of the anti-rotation thread “interlock” can meet the pre-tightening and anti-loose requirements. In special cases, The pre-tightening force of the fastening bolt (3) or the locking bolt (4) will be lower than 0.4σs, since the total pre-tightening force of the fastening bolt (3) and the locking bolt (4) is equal to the pre-tightening force of the two. And, the total pre-tightening force is equivalent to the pre-tightening force acting on the solid bolt. If the pre-tightening force of the solid bolt is not less than 0.4σs, the pre-tightening and anti-loose requirements can also be met.

The selection of the diameter of the locking bolt (4) and the fastening bolt (3) and the calculation of the preload force distribution:

The first calculation method. According to the background art, "the double nut lock structure is subjected to force P1 = 0.2P, P2 = 0.8P is suitable" to calculate the diameter of the lock bolt (4).

Take the 8.8 grade M30×2 threaded joint as the example in Figure 10, the solid bolt diameter D=30mm, the effective tensile length of the screw L=65mm (equal to the sum of the thickness of the two joints), the nut is tightened at 1450Nm torque, the solid bolt When the pre-tightening force P=269kN, the bolt elastic elongation ΔL=0.118mm, the bolt stress σ=381Mpa, the yield strength σs=640Mpa, σ/σs=0.6 (for the calculation process, see the background technology “Example of calculation of bolt elongation”) . After the solid bolt becomes the fastening bolt (3) and the locking bolt (4), the coupling member is fastened together with the reverse rotation nut (9). The diameter (outer diameter), material, and processing of the fastening bolt (3) The process, modulus of elasticity, thread and effective stretch length are the same as for solid bolts.

The pre-tightening force of the locking bolt (4) F1=P1=0.2P, the pre-tightening force of the fastening bolt (3) F2=P2=0.8P, the total pre-tightening of the fastening bolt (3) and the locking bolt (4) Tight force F = F1 + F2 = 0.2P + 0.8P = P.

The length of the anti-rotation nut (9) fastening thread is 25.6mm (take the type M30 × 2 hex nut thickness Mmax = 25.6mm, other values can also be taken), the inner distance between the locking thread and the fastening thread is 10.7mm (take M24×2 hexagonal cap nut G1max first series value 10.7mm, can also take the second series value 7.3mm or other suitable value), the height of the head of the fastening bolt (3) takes the nominal height K=18.7mm Therefore, the effective tensile length L1 of the locking bolt (4) is 120 mm (L1 = 65 + 25.6 + 10.7 + 18.7 = 120 mm). The effective tensile length L2 of the fastening bolt (3) is L=65 mm.

If the material, processing technique, elastic modulus, stress, etc. of the locking bolt (4) are the same as the solid bolt, only the effective tensile length L1 of the locking bolt (4) is increased to 120 mm compared with the solid bolt, so its elastic elongation The amount ΔL1 should be increased in proportion to 0.218 mm (ΔL1 = ΔL × 120 / L = 0.118 × 120 / 65 = 0.218 mm).

If the pre-tightening force of the locking bolt (4) F1=P1=0.2P=0.2×269=53.8kN, the sectional area S1 of the locking bolt (4) is:

S1=F1×L1/(E×ΔL1)=53.8×10 ³ ×120×10 ^-3 /(210×10 ⁹ ×0.218×10 ^-3 )=141.0mm ²

The diameter d of the locking bolt (4) is:

d=(4×S1/3.14) ^1/2 =(4×141.0/3.14) ^1/2 =13.4mm

Take d=14mm, select 8.8 M14 bolt as the locking bolt (4), and the sectional area S1 of the locking bolt (4) is:

S1=3.14×d ² /4=3.14×14 ² ×10 ^-6 /4=153.9mm ²

The cross-sectional area S of the solid bolt is:

S=3.14×D ² /4=3.14×30 ² ×10 ^-6 /4=706.5mm ²

Since the diameter of the locking bolt (4) and the inner diameter of the central hole of the fastening screw hole (3) are small, the clearance is negligible, so the sectional area S2 of the 8.8-stage fastening bolt (3) is:

S2=S-S1=706.5-153.9=552.6mm ²

The tightening bolt (3) and the locking bolt (4) under the preload force, the elastic elongation is generally not the same, but in the bear The elastic elongation is the same at the working load. The best case is: the fastening bolt (3) and the locking bolt (4) jointly approach or reach the yield strength under the action of the preload force and the maximum working load to reach the maximum load carrying capacity (stretch resistance) against the load, ie "The tightening bolts (3) and the locking bolts (4) are required to have the same amount of elastic elongation when they are loaded from the preload force to the yield strength", which is simply referred to as "the same requirement for the elastic elongation."

Calculate the preload of the locking bolt (4) and the fastening bolt (3) and the maximum load capacity of the bolt:

According to the background art, "the high-strength bolt connection must adopt a large pre-tightening force, and the general pre-tightening force should be 70% to 81.2% of the yield strength of the bolt material", so the high-strength bolt pre-tightening force can take 0.8σs. The error of the pre-tightening force of the reference nut (bolt) rotation angle is about ±15%. Considering the influence of the pre-tightening operation error, the pre-tightening force is prevented from being higher than 0.8σs, so the pre-tightening force is 0.68σs (0.8×0.85=0.68). . If the pre-tightening force reaches the upper limit of 115%, the actual pre-tightening force is 0.78σs (0.68×1.15=0.78<0.8), which is consistent with the background art “the pre-tightening force of the bolt is less than 80% of the yield limit of the bolt material, and try to Take a higher value" requirement.

1.1 If the pre-tightening force F1 of the locking bolt (4) is 0.68σs (that is, the pre-tightening stress σ1=0.68σs), according to the “requirement of the same elastic elongation”, the above-mentioned “using the 8.8 grade M30 of the coupling in Fig. 10 is calculated. × 2 threaded joint as an example" (related to the calculation method of the first type) fastening bolt (3) preload force F2 and bolt maximum load capacity.

When the locking bolt (4) is loaded from zero to the yield strength, the elastic elongation is ΔL1q, and when it is loaded from zero to the pre-tightening force F1, the elastic elongation is ΔL1, and the elastic elongation is from the preload force F1 to the yield strength. The amount is ΔL1z, so ΔL1z = ΔL1q - ΔL1.

The preload force F1 of the locking bolt (4) is:

F1=σ1×S1=0.68×σs×3.14×d ² /4=0.68×640×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4

=66960N≈67KN

The pulling force F1q when the locking bolt (4) is loaded from zero to the yield strength is:

F1q=σs×S1=σs×3.14×d ² /4=640×10 ⁶ ×3.14×14 ² ×10 ^-6 /4=98470N≈98.5KN

When the locking bolt (4) is loaded from zero to the yield strength, the elastic elongation ΔL1q is:

ΔL1q=F1q×L1/(E×S1)=σs×L1/E=640×10 ⁶ ×120×10 ^-3 /(210×10 ⁹ )=0.366mm

When the locking bolt (4) is loaded from zero to the preload force F1, the elastic elongation ΔL1 is:

ΔL1=F1×L1/(E×S1)=σ1×L1/E=0.68×σs×L1/E

=0.68×640×10 ³ ×120×10 ^-3 /(210×10 ⁹ )=0.249mm

When the locking bolt (4) is loaded from the preload force F1 to the yield strength, the elastic elongation ΔL1z is:

ΔL1z=ΔL2z=ΔL1q-ΔL1=0.366-0.249=0.117mm

Determination of the pre-tightening force of the fastening bolt (3):

When the fastening bolt (3) is loaded from zero to the yield strength, the elastic elongation is ΔL2q, and the elastic elongation is ΔL2z from the preload to the yield strength. According to the requirement of the same elastic elongation, ΔL2z= ΔL1z; the elastic elongation of the fastening bolt (3) when loading from zero to the preload is ΔL2, because ΔL2 = ΔL2q - ΔL2z = ΔL2q - ΔL1z, so the pulling force required to load from zero to ΔL2 is the fastening bolt ( 3) Preload force F2.

The tension F2q when the fastening bolt (3) is loaded from zero to the yield strength is:

F2q=σs×S2=σs×(3.14×D ² /4-3.14×d ² /4)

=640×10 ⁶ ×3.14×[(30×10 ^-3 ) ² /4-(14×10 ^-3 ) ² /4]=353689N≈353.7KN

When the fastening bolt (3) is loaded from zero to the yield strength, the elastic elongation ΔL2q is:

ΔL2q=F2q×L2/(E×S2)=σs×L2/E=640×10 ⁶ ×65×10 ^-3 /(210×10 ⁹ )=0.198mm

According to the "requirement of the same elastic elongation", the elastic elongation ΔL2 when the fastening bolt (3) is loaded from zero to the preload force F2 is:

ΔL2=ΔL2q-ΔL1z=0.198-0.117=0.081mm

The tension required to tighten the bolt (3) from zero to ΔL2=0.081mm, ie the preload force F2 is:

F2=ΔL2×E×S2/L2=ΔL2×E×3.14×[(D×10 ^-3 /2) ² -(d×10 ^-3 /2) ² ]/L2

=0.081×10 ^-3 ×210×10 ⁹ ×3.14×[(30×10 ^-3 /2) ² -(14×10 ^-3 /2) ² ]/(65×10 ^-3 )

=144621N≈144.6KN

The stress σ2 (ie, the pre-tightening stress) of the fastening bolt (3) when the pre-tightening force is F2 is:

Σ2=F2/S2=F2/(3.14×D ² /4-3.14×d ² /4)

=144.6×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=262Mpa

Σ2/σs=262/640=0.41>0.4 (in accordance with requirements)

The total preload of the locking bolt (4) and the fastening bolt (3) is F = F1 + F2 = 67 + 144.6 = 211.6 kN.

When the preload force of the 8.8 grade M30×2 solid bolt is P=F=211.6kN, the stress σ is:

σ=P/S=F/(3.14×D ² /4)=211.6×10 ³ /(3.14×30 ² ×10 ^-6 /4)=300Mpa

σ/σs=300/640=0.47>0.4 (in accordance with requirements)

When the pre-tightening force F1 of the locking bolt (4) is 0.68σs, the pre-tightening force F2 of the fastening bolt (3) is 0.41σs, which is equivalent to the pre-tightening force of the 8.8-class M30×2 solid bolt being 0.47σs, which is higher than 0.4σs, can meet the requirements of pre-tightening and anti-loosening.

The maximum load carrying capacity of the locking bolt (4) and the fastening bolt (3) is:

F1q+F2q=98.5+353.7=452.2KN≈450KN

When the pre-tightening force of the locking bolt (4) is 0.68σs, the pre-tightening force of the fastening bolt (3) is 0.41σs, only the theoretical calculation proves that the locking bolt (4) and the fastening bolt (3) are Under the action of the working load, the elastic elongation when the proof reaches the yield strength is 0.117 mm. When the bolts are connected, there is a safety factor. In the selection design, the yield strength is generally not reached, and the bolts are not overloaded.

1.2 Considering the influence of pre-tightening operation error ±15%, if the pre-tightening force of the locking bolt (4) and the fastening bolt (3) takes the upper limit of 115%, according to the relevant calculation result of 1.1, the locking bolt (4) is pre- The tightening force F1 is 0.78σs (0.68×1.15=0.78), that is, the pre-tightening stress σ1=0.78σs; the pre-tightening force F2 of the fastening bolt (3) is 0.47σs (0.41×1.15=0.47), that is, the pre-tightening stress σ2= 0.47σs, calculate the total preload force F and maximum load capacity of the bolt.

The preload force F1 of the locking bolt (4) is:

F1=σ1×S1=0.78×σs×3.14×d ² /4=0.78×640×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4

=76807N≈76.8KN

The preload force F2 of the fastening bolt (3) is:

F2=σ2×S2=0.47×σs×3.14×[(D×10 ^-3 /2) ² -(d×10 ^-3 /2) ² ]

=0.47×640×3.14×[(30×10 ^-3 /2) ² -(14×10 ^-3 /2) ² ]=166234N≈166.2KN

The total preload of the locking bolt (4) and the fastening bolt (3) is F = F1 + F2 = 76.8 + 166.2 = 243 kN.

If the 8.8 grade M30×2 solid bolt pre-tightening force P=F=243kN, the stress σ is:

σ=P/S=F/(3.14×D ² /4)=243×10 ³ /(3.14×30 ² ×10 ^-6 /4)=344Mpa

σ/σs=344/640=0.54>0.4 (in accordance with requirements)

When the pre-tightening force of the locking bolt (4) is 0.78σs and the pre-tightening force of the fastening bolt (3) is 0.47σs, the pre-tightening force of the 8.8-class M30×2 solid bolt is 0.54σs, which is higher than 0.4σs. Meet the anti-loose requirements.

When the locking bolt (4) is loaded from zero to the yield strength, the pulling force F1q=98.5KN:

F1q=σs×S1=98470N≈98.5KN (for the calculation process, see 1.1 Calculation Method)

When the locking bolt (4) is loaded from zero to the yield strength, the elastic elongation ΔL1q=0.366mm:

ΔL1q=F1q×L1/(E×S1)=0.366mm (for the calculation process, see 1.1 Calculation Method)

ΔL1=F1×L1/(E×S1)=σ1×L1/E=0.78×σs×L1/E

=0.78×640×10 ³ ×120×10 ^-3 /(210×10 ⁹ )=0.285mm

ΔL1z=ΔL2z=ΔL1q-ΔL1=0.366-0.285=0.081mm

When the fastening bolt (3) is loaded from zero to the yield strength, the elastic elongation ΔL2q=0.198mm:

ΔL2q=F2q×L2/(E×S2)=0.198mm (for the calculation process, see 1.1 Calculation Method)

When the fastening bolt (3) is loaded from zero to the preload force F2, the elastic elongation ΔL2 is:

ΔL2=F2×L2/(E×S2)=σ2×L2/E=0.47×σs×L2/E

=0.47×640×10 ³ ×65×10 ^-3 /(210×10 ⁹ )=0.093mm

When the fastening bolt (3) is loaded from the preload force F2 to the yield strength, the elastic elongation ΔL2z is:

ΔL2z=ΔL2q-ΔL2=0.198-0.093=0.105mm>ΔL1z=0.081mm

It is indicated that the locking bolt (4) reaches the yield strength ahead of the fastening bolt (3), and the elastic elongation of the two increases synchronously is ΔL1z=0.081mm, and the fastening bolt (3) starts with ΔL2=0.093mm and the locking bolt (4) The required pulling force Fj when synchronizing the increase of ΔL1z=0.081mm is:

Fj=(ΔL2+ΔL1z)×E×S2/L2=(ΔL2+ΔL1z)×E×3.14×[(D×10 ^-3 /2) ² -(d×10 ^-3 /2 ² )]/L2

= (0.093 + 0.081) × 210 × 10 ⁹ × 3.14 × [(30 × 10 ^-3 /2) ² - (14 × 10 ^-3 /2) ² ] / (65 × 10 ^-3 )

=310669N≈310.7KN

When the tightening bolt (3) reaches the tensile force Fj, that is, the elastic elongation is ΔL2+ΔL1z=0.093+0.081=0.174mm (the ΔL2q=0.198mm has not been reached yet), the locking bolt (4) has reached the yield strength (ΔL1q has reached 0.366) Mm).

The locking bolt (4) reaches the maximum load carrying capacity together with the fastening bolt (3) when it reaches the yield strength, and its value is:

F1q+Fj=98.5+310.7=409.2KN≈410KN

1.3 Consider the influence of the pre-tightening operation error ±15%. If the pre-tightening force of the locking bolt (4) and the fastening bolt (3) is 85%, the locking bolt (4) is pre-determined according to the relevant calculation result of 1.1. The tightening force F1 is 0.58σs (0.68×0.85=0.58), that is, the pre-tightening stress σ1=0.58σs; the tightening force of the fastening bolt (3) F2 is 0.35σs (0.41×0.85=0.35), that is, the pre-tightening stress σ2= 0.35σs, calculate the total preload force F and maximum load capacity of the bolt.

The preload force F1 of the locking bolt (4) is:

F1=σ1×S1=0.58×σs×3.14×d ² /4=0.58×640×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4

=57113N≈57.1KN

The preload force F2 of the fastening bolt (3) is:

F2 = σ2 × S2 = 0.35 × σs × 3.14 × [(D × 10 ^-3 /2) ² - (d × 10 ^-3 /2) ² ]

=0.35×640×3.14×[(30×10 ^-3 /2) ² -(14×10 ^-3 /2) ² ]=123791N≈123.8KN

The total preload of the locking bolt (4) and the fastening bolt (3) is F = F1 + F2 = 57.1 + 123.8 = 180.9 kN.

When the preload force of the 8.8 grade M30×2 solid bolt is P=F=180.9kN, the stress σ is:

σ=P/S=F/(3.14×D ² /4)=180.9×10 ³ /(3.14×30 ² ×10 ^-6 /4)=256Mpa

σ/σs=256/640=0.4 (in accordance with requirements)

When the pre-tightening force of the locking bolt (4) is 0.58σs and the pre-tightening force of the fastening bolt (3) is 0.35σs, the pre-tightening force of the 8.8-class M30×2 solid bolt is 0.4σs, which can be used for some requirements to be appropriately reduced. In the case of pre-tightening, the requirements for anti-loosening can be met.

The tension F1q=98.5KN when the locking bolt (4) is loaded from zero to the yield strength:

ΔL1=F1×L1/(E×S1)=σ1×L1/E=0.58×σs×L1/E

=0.58×640×10 ³ ×120×10 ^-3 /(210×10 ⁹ )=0.212mm

ΔL1z=ΔL2z=ΔL1q-ΔL1=0.366-0.212=0.154mm

ΔL2=F2×L2/(E×S2)=σ2×L2/E=0.35×σs×L2/E

=0.35×640×10 ³ ×65×10 ^-3 /(210×10 ⁹ )=0.069mm

ΔL2z=ΔL2q-ΔL2=0.198-0.069=0.129mm<ΔL1z=0.154mm

It is indicated that the fastening bolt (3) reaches the yield strength ahead of the locking bolt (4), and the elastic elongation of the two increases synchronously is ΔL2z=0.129mm, and the locking bolt (4) starts from ΔL1=0.212mm and the fastening bolt (3) The required pulling force Fs when synchronously increasing ΔL2z=0.129mm is:

Fs=(ΔL1+ΔL2z)×E×S1/L1=(ΔL1+ΔL2z)×E×3.14×(d×10 ⁻³ /2) ² /L1

=(0.212+0.129)×210×10 ⁹ ×3.14×(14×10 ^-3 /2) ² /(120×10 ^-3 )

=91816N≈91.8KN

When the tightening bolt (4) reaches the tensile force Fs, that is, the elastic elongation is ΔL1+ΔL2z=0.212+0.129=0.341mm (the ΔL1q=0.366mm has not been reached yet), the tightening bolt (3) has reached the yield strength (ΔL2q has reached 0.198) Mm).

The fastening bolt (3) reaches the maximum load carrying capacity together with the locking bolt (4) when it reaches the yield strength, and its value is:

F2q+Fs=353.7+91.8=445.5KN≈450KN

1.4 If the pre-tightening force F1 of the locking bolt (4) is 0.68σs (that is, the pre-tightening stress σ1=0.68σs), no “elasticity” is adopted. The calculation method of the same elongation requirement, the tightening bolt (3) pre-tightening force F2 directly takes the remaining pre-tightening force of the solid bolt as P-F1, and calculates the maximum bearing capacity of the bolt. This method is called “remaining preloading”. Force" calculation method.

The "residual preload force" calculation method is used to calculate the maximum load capacity of the bolts described above in the example of the joint using the 8.8 grade M30×2 threaded joint in Fig. 10 (related to the first calculation method).

When the pre-tightening force of the locking bolt (4) is 0.68σs, F1=67KN:

F1=σ1×S1=66960N≈67KN (for the calculation process, see 1.1 Calculation Method)

When the locking bolt (4) is loaded from zero to the preload force F1, the elastic elongation ΔL1=0.249mm:

ΔL1=F1×L1/(E×S1)=0.249mm (for the calculation process, see 1.1 Calculation Method)

ΔL1z=ΔL1q-ΔL1=0.366-0.249=0.117mm

The pre-tightening force F2 and the stress σ2 of the fastening bolt (3) are:

F2=P-F1=269-67=202KN

Σ2=F2/S2=F2/(3.14×D ² /4-3.14×d ² /4)

=202×10 ³ /[3.14×(30×10 ^-3 ) ² /4-3.14×(14×10 ^-3 ) ² /4]=366Mpa

Σ2/σs=366/640=0.57>0.4 (in accordance with requirements)

ΔL2=F2×L2/(E×S2)=σ2×L2/E=0.57×σs×L2/E

=0.57×640×10 ³ ×65×10 ^-3 /(210×10 ⁹ )=0.113mm

ΔL2z=ΔL2q-ΔL2=0.198-0.113=0.085mm<ΔL1z=0.117mm

It is indicated that the fastening bolt (3) reaches the yield strength ahead of the locking bolt (4), and the elastic elongation of the two increases synchronously is ΔL2z=0.085mm, and the locking bolt (4) starts from ΔL1=0.249mm and the fastening bolt (3) The required pulling force Fs when synchronizing the increase of ΔL2z=0.085mm is:

Fs=(ΔL1+ΔL2z)×E×S1/L1=(ΔL1+ΔL2z)×E×3.14×(d×10 ⁻³ /2) ² /L1

=(0.249+0.085)×210×10 ⁹ ×3.14×(14×10 ^-3 /2) ² /(120×10 ^-3 )

=89931N≈89.9KN

When the tightening bolt (4) reaches the tensile force Fs, that is, the elastic elongation is ΔL1+ΔL2z=0.249+0.085=0.334mm (the ΔL1q=0.366mm has not been reached yet), the tightening bolt (3) has reached the yield strength (ΔL2q has reached 0.198) Mm).

F2q+Fs=353.7+89.9=443.6KN≈440KN

When using high-strength bolts, consider the effect of ±15% of the pre-tightening operation error, locking bolts (4) and fastening bolts The higher value of preload of (3) may be 0.68σs (0.8×0.85=0.68), and the lower value may be 0.47σs (0.4/0.85=0.471≈0.47). The intermediate value may take the average of lower and lower values. 0.58σs (0.68/2+0.47/2=0.575≈0.58). If the pre-tightening force of the locking bolt (4) and the fastening bolt (3) takes a higher value of 0.68σs, considering the upper limit of the pre-tightening force of 115%, the pre-tightening force is 0.78σs (0.68×1.15=0.78), nor More than 0.8σs; if all take a lower value of 0.47σs, considering the lower limit of pre-tightening force of 85%, the pre-tightening force is 0.4σs (0.47×0.85=0.3995≈0.4), which can also meet the requirements.

Due to the influence of pre-tightening operation error, it is difficult to achieve the same requirement of “elastic elongation” (ie, 1.1 calculation method). 1.1 The calculation method provides reference when needed, so when the physical bolt pre-tightening force is determined, 1.4 can be used. The calculation method calculates the preload of the fastening bolt (3) and the locking bolt (4). The difference between the 1.2 and 1.3 calculation methods is that the locking bolts (4) and the fastening bolts (3) have different order of yield strength.

The second calculation method. According to the background art, "the high-strength bolt connection must adopt a large pre-tightening force, and the general pre-tightening force should be 70%-81.2% of the yield strength of the bolt material", according to the pre-tightening stress σ1=0.8 Σs and preload P1 = 0.2P select the diameter of the locking bolt (4).

As in the first calculation method of the above, "take the joint of the 8.8 grade M30×2 solid bolt connection in the example of Fig. 10 as an example", the yield strength σs of the 8.8 grade bolt is 640 MPa, and the stress σ1 of the lock bolt (4) is:

Σ1=0.8σs=0.8×640=512Mpa

When the pre-tightening force of the locking bolt (4) F1=P1=0.2P=0.2×269=53.8kN, the sectional area S1 of the locking bolt (4) is:

S1=F1/σ1=53.8×10 ³ /(512×10 ⁶ )=105.08mm ²

The diameter d of the locking bolt (4) is:

d=(4×S1/3.14) ^1/2 =(4×105.08/3.14) ^1/2 =11.57mm

The ratio of the diameter d of the locking bolt (4) to the diameter D of the solid bolt is:

d/D=11.57/30=0.39≈0.4

Therefore, when the 8.8-stage locking bolt (4) is σ1/σs=0.8 and the pre-tightening force F1=0.2P, the diameter d of the locking bolt (4) is equal to 0.4 times the diameter D of the solid bolt or the fastening bolt (3). That is, d = 0.4D.

The diameter d=0.4D of the locking bolt (4) can be used as the lower limit because the stress σ1 of the locking bolt (4) has reached the limit, but if the fastening bolt (3) and the locking bolt (4) use different materials, The yield strength of the locking bolt (4) is relatively high, the cross-sectional area of the locking bolt (4) can continue to be smaller, and the diameter of the locking bolt (4) can be further reduced.

If the diameter d of the locking bolt (4) is 12 mm, a 8.8-stage M12 bolt can be selected as the locking bolt (4).

For the calculation of the preload force of the locking bolt (4) and the fastening bolt (3), refer to the relevant content of 1.4 in the first calculation method.

The third calculation method. The diameter of the locking bolt (4) is selected by calculating the cross-sectional area of the fastening bolt (3) and the locking bolt (4).

The cross-sectional area S of the solid bolt is:

S=3.14×(D/2) ² =3.14×D ² /4

After the solid bolt becomes the fastening bolt (3) and the locking bolt (4), the sectional area S1 of the locking bolt (4) is:

S1=3.14×(d/2) ² =3.14×d ² /4

The cross-sectional area S2 of the fastening bolt (3) is:

S2=S-S1=3.14×(D/2) ² -3.14×(d/2) ² =3.14×D ² /4-3.14×d ² /4

If the cross-sectional areas of the locking bolt (4) and the fastening bolt (3) are required to be equal, then:

S1=S2=3.14×D ² /4-3.14×d ² /4=3.14×d ² /4

Calculated: d = (D / 2) ^1/2

d/D=(1/2) ^1/2 =1/1.414=0.707

d=0.707D can be used as the upper limit, the maximum diameter of the locking bolt (4) is 0.707D, and the diameter of the locking bolt (4) can be slightly less than 0.707D. When the bolt material and the machining process are the same, the locking bolt (4) The cross-sectional area cannot be larger than the cross-sectional area of the fastening bolt (3), otherwise the strength of the fastening bolt (3) will be affected. However, if the fastening bolt (3) and the locking bolt (4) use different materials or processing techniques, the tightening bolt (3) has a relatively high yield strength, and the locking bolt (4) has a larger cross-sectional area than the fastening bolt (3). When the cross-sectional area, the bearing capacity of the fastening bolt (3) is still relatively large, the diameter of the locking bolt (4) can be further increased.

For the calculation of the pre-tightening force of the locking bolt (4) and the fastening bolt (3), reference can also be made to the relevant content of 1.4 in the first calculation method.

The fourth calculation method. According to the background art, "the high-strength bolt connection must adopt a large pre-tightening force, and the general pre-tightening force should be 70% to 81.2% of the yield strength of the bolt material" to fasten the bolt (3). The maximum pre-tightening force Fmax is equal to the physical bolt pre-tightening force P to select the diameter of the locking bolt (4), and the fastening bolt (3) pre-tightening force F2 is required to be no more than 0.8σs.

Since the physical bolt pre-tightening force P is equal to the sum of the pre-tightening forces of the fastening bolt (3) and the locking bolt (4), that is, the total pre-tightening force F, but the fastening bolts are tightened after tightening the locking bolts (4) (3) The pre-tightening force F2 will be reduced, and the reduced amplitude is equal to the pre-tightening force F1 of the locking bolt (4). If the fastening bolt (3) is required to tighten the locking bolt (4), it can also achieve the required Pre-tightening force, so the maximum pre-tightening force Fmax should be equal to the physical bolt pre-tightening force P when assembling the fastening bolts (3). The same applies to the first, second and third calculation methods.

As in the first calculation method of the above, "take the 8.8-class M30×2 solid bolt connection in the coupling in Fig. 10 as an example", select the 8.8-class M14 bolt as the locking bolt (4), and the pre-tightening force of the locking bolt (4) For F1=67KN, the pre-tightening force of the fastening bolt (3) is F2=202KN (the result of the calculation method of 1.4). The maximum pre-tightening force of the fastening bolt (3) Fmax=P=F=F1+F2=67+202=269KN, after the locking bolt (4) is loaded with the pre-tightening force (F1=67KN), the fastening bolt (3) The actual pre-tightening force is F2=Fmax-F1=269-67=202KN, but after the locking bolt (4) is removed, the pre-tightening force F2 of the fastening bolt (3) rebounds and returns to Fmax, ie F2=Fmax= 269KN.

The cross-sectional area S of the solid bolt is:

S=3.14×(D/2) ² =3.14×D ² /4

The cross-sectional area S1 of the locking bolt (4) is:

S1=3.14×(d/2) ² =3.14×d ² /4

The cross-sectional area S2 of the fastening bolt (3) is:

S2=S-S1=3.14×(D/2) ² -3.14×(d/2) ² =3.14×(D ² -d ² )/4

The pulling force when the solid bolt reaches the λ times yield strength, that is, the pre-tightening force P is:

P=λ×σs×S=λ×σs×3.14×D ² /4

If the tension of the fastening bolt (3) reaches 0.8σs is equal to Fmax, then:

Fmax=0.8×σs×S2=0.8×σs×3.14×(D ² -d ² )/4

If P=Fmax is required, then:

P=Fmax=λ×σs×3.14×D ² /4=0.8×σs×3.14×(D ² -d ² )/4

Simplified: λ × D ² = 0.8 × (D ^{2 -} d ² )

Calculated: d = [(1 - λ / 0.8)] ^1/2 × D

When λ=0.672: d=[(1-0.672/0.8)] ^1/2 ×D=0.4D

That is, when λ=σ/σs≤0.672, d≥0.4D;

When λ = 0.6: d = [(1 - λ / 0.8)] ^1/2 × D = [(1 - 0.6 / 0.8)] ^1/2 × D = 0.5D

That is, when λ=σ/σs=0.6, d=0.5D;

When d=(D/2) ^1/2 : λ=0.8×(D ² -d ² )/D ² =0.8×(1-d ² /D ² )=0.8(1-1/2)=0.4

That is, when λ = σ / σs ≥ 0.4, d ≤ 0.707D.

Therefore, when 0.4 ≤ λ ≤ 0.672, 0.707D ≥ d ≥ 0.4D, both are closed intervals.

Check the stress σ2 of the fastening bolt (3) with the "tightening bolt (3) maximum pre-tightening force Fmax equal to the solid bolt pre-tightening force P":

Same as the first calculation method "take the coupling of 8.8 grade M30×2 solid bolts in Figure 10 as an example", select the 8.8 grade M14 bolt as the lock bolt (4), when the tightening bolt (3) maximum preload When Fmax=P=269KN, the stress σ2 is:

Σ2=Fmax/S2=P/(3.14×D ² /4-3.14×d ² /4)

=269×10 ³ /[3.14×(30×10 ^-3 ) ² /4-3.14×(14×10 ^-3 ) ² /4)]=487Mpa

Grade 8.8 bolt yield strength σs = 640Mpa, σ2 / σs = 487 / 640 = 0.76 < 0.8 (in accordance with requirements).

Therefore, the selection of the 8.8 grade M14 bolt as the locking bolt (4) meets the requirements. Similarly, when the 8.8 grade M12 bolt is selected as the lock bolt (4), the fastening bolt (3) has a larger cross-sectional area, and σ2/σs is also less than 0.8, so it also meets the requirements.

The fifth calculation method. When the maximum pre-tightening force Fmax of the fastening bolt (3) is equal to the physical bolt pre-tightening force P, consider the influence of the pre-tightening operation error ±15%, if the tightening bolt (3) maximum pre-tightening force Fmax is 0.68σs, and the physical bolt pre-tightening force P is 0.47σs (that is, the pre-tightening stress σ=0.47σs), and the diameter of the locking bolt (4) is calculated.

Taking the 8.8-class M30×2 solid bolt into the locking bolt (4) and the fastening bolt (3) as an example, when the pre-tightening force of the solid bolt is 0.47σs, the pre-tightening force P is:

P = σ × S = 0.47 × σs × 3.14 × D 2 /4=0.47×640×10 6 × 3.14 × (30 × 10 -3) 2/4

=212515N≈212.5KN

The cross-sectional area S of the 8.8-class solid bolt is:

S=3.14×D ² /4=3.14×D ² /4=3.14×30 ² ×10 ^-6 /4=706.5mm ²

If the maximum pre-tightening force Fmax of the 8.8-stage fastening bolt (3) is 0.68σs, which is equal to the physical bolt pre-tightening force P, the cross-sectional area S2 of the fastening bolt (3) is:

S2=Fmax/(0.68×σs)=P/(0.68×σs)=212.5×10 ³ /(0.68×640×10 ⁶ )=488.3 mm ²

The cross-sectional area S1 of the 8.8-stage locking bolt (4) is:

S1=S-S2=706.5-488.3=218.2mm ²

The diameter d of the locking bolt (4) is:

d=(4×S1/3.14) ^1/2 =(4×218.2/3.14) ^1/2 =16.67mm

Therefore, the diameter d of the 8.8-stage locking bolt (4) can be taken as 16 mm.

Refer to the first calculation method 1.4 for the calculation of the preload force of the lock bolt (4) and the fastening bolt (3).

If the solid bolt, the fastening bolt (3) and the locking bolt (4) are high-strength bolts, the following characteristics are obtained when the yield strength is the same:

1. The physical bolt pre-tightening force requires 0.4σs ≤ P ≤ 0.8σs;

2. The tightening bolt (4) pre-tightening force requires 0.4σs ≤ F1 ≤ 0.8σs;

3. Tightening bolt (3) pre-tightening force requirement 0.4σs ≤ F2 ≤ 0.8σs;

4. The tightening bolt (3) when the maximum pre-tightening force Fmax is equal to the physical bolt pre-tightening force P, requires σ2 ≤ 0.8σs;

5. The diameter d of the locking bolt (4) is inversely proportional to the λ = σ / σs of the solid bolt.

The maximum pre-tightening force or maximum pre-tightening stress of the solid bolt in the ordinary threaded joint is 0.78σs. If the influence of the pre-tightening operation error is ±15%, it becomes the locking bolt (4) and the tightening bolt (3). The higher value of the tightening force may be 0.66σs (0.78×0.85=0.663≈0.66), the lower value may be 0.47σs (0.4/0.85=0.471≈0.47), and the intermediate value may take the upper value of the higher value and the lower value of 0.57σs ( 0.663/2+0.471/2=0.567≈0.57). If the pre-tightening force of the locking bolt (4) and the fastening bolt (3) takes a higher value of 0.66σs, considering the upper limit of the pre-tightening force of 115%, the pre-tightening force is 0.76σs (0.66×1.15=0.759≈0.76). It does not exceed 0.78σs; if both lower values are 0.47σs, considering the lower limit of pre-tightening force of 85% and the pre-tightening force of 0.4σs (0.47×0.85=0.3995≈0.4), it can also meet the requirements.

The sixth calculation method. Select the diameter of the locking bolt (4) according to the maximum pre-tightening force and the maximum pre-tightening stress of the fastening bolt (3), and consider the influence of the pre-tightening operation error ±15% to calculate the maximum bearing capacity of the bolt and Fastening bolt (3) pre-tightening force.

Taking the 5.6-stage M30×2 threaded joint of the coupling in Fig. 10 as an example, the solid bolt diameter D=30 mm, the effective tensile length of the screw L=65 mm, the yield strength σs=500×0.6=300 MPa, and the requirement σ/σs=0.58. After the solid bolt becomes the fastening bolt (3) and the locking bolt (4), the coupling member is fastened together with the reverse rotation nut (9).

The fastening bolt (3) has the same diameter (outer diameter), thread, effective tensile length, material and machining process as the solid bolt. The material of the locking bolt (4) and the machining process are the same as the physical bolt. The length of the anti-rotation nut (9) fastening thread is 25.6mm, the inner distance between the locking thread and the fastening thread is 10.7mm, and the height of the head of the fastening bolt (3) is 18.7mm, so the locking The bolt (4) has an effective tensile length L1 of 120 mm (refer to the first calculation method). The fastening bolt (3) has an effective tensile length L2 = L = 65 mm.

The pre-tightening force P of the 5.6-class M30×2 solid bolt is:

P = σ × S = 0.58 × σs × 3.14 × D 2 /4=0.58×300×10 6 × 3.14 × (30 × 10 -3) 2/4

=122931N≈122.9KN

The cross-sectional area S of the 5.6-class M30×2 solid bolt is:

S=3.14×D ² /4=3.14×(30×10 ^-3 ) ² /4=706.5mm ²

When σ/σs=0.78, the maximum preload force Pmax of the 5.6-class M30×2 solid bolt is:

Pmax = σ × S = 0.78 × σs × 3.14 × D 2 /4=0.78×300×10 6 × 3.14 × (30 × 10 -3) 2/4

=165321N≈165.3KN

When the pre-tightening force of the 5.6-class M30×2 solid bolt or fastening bolt (3) reaches Pmax=165.3KN, the bottom of the external thread groove begins to break. When the pre-tightening force is less than Pmax, the external thread should be no problem.

When the maximum pre-tightening force of F-=====================

S2=Fmax/(0.78×σs)=P/(0.78×σs)=122.9×10 ³ /(234×10 ^-6 )=525.2 mm ²

The cross-sectional area S1 of the locking bolt (4) is:

S1=S-S2=706.5-525.2=181.3mm ²

The diameter d of the locking bolt (4) is:

d=(4×S1/3.14) ^1/2 =(4×181.3/3.14) ^1/2 =15.2mm

The diameter d of the locking bolt (4) may be a value not greater than 15.2 mm, and if it is larger than 15.2 mm, the sectional area S2 of the fastening bolt (3) may be insufficient.

If the diameter of the locking bolt (4) is d=14mm, a 5.6-stage M14 bolt can be selected as the locking bolt (4).

When the pre-tightening force F1 of the 5.6-stage M14 locking bolt (4) is 0.66σs (ie, the pre-tightening stress σ1=0.66σs), the tightening bolt (3) pre-tightening force F2 takes the remaining pre-tightening force of the solid bolt as P- When F1, calculate the maximum load capacity of the bolt:

The preload force F1 of the locking bolt (4) is:

F1=σ1×S1=0.66σs×S1=0.66×300×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4=30464N≈30.5KN

The pre-tightening force F2 and the stress σ2 of the fastening bolt (3) are:

F2=P-F1=122.9-30.5=92.4KN

Σ2=F2/S2=F2/(3.14×D ² /4-3.14×d ² /4)

=92.4×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=167Mpa

Because the yield strength of 5.6 bolts is σs=300Mpa, σ2/σs=167/300=0.56<0.78 (in accordance with requirements), that is, the pre-tightening force F2 of the fastening bolts (3) is 0.56σs.

When the tightening bolt (3) maximum preload force Fmax=P=122.9KN, the stress σ2 is:

Σ2=Fmax/S2=P/(3.14×D ² /4-3.14×d ² /4)

=122.9×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=222Mpa

Σ2/σs=222/300=0.74<0.78 (in accordance with requirements)

ΔL1=F1×L1/(E×S1)=σ1×L1/E=0.66×σs×L1/E

=0.66×300×10 ⁶ ×120×10 ^-3 /(200×10 ⁹ )=0.119mm

Since the 5.6-class bolt is an ordinary bolt, the elastic modulus E is 200×10 ³ Mpa.

ΔL1q=F1q×L1/(E×S1)=σs×L1/E=300×10 ⁶ ×120×10 ^-3 /(200×10 ⁹ )=0.180mm

ΔL1z=ΔL1q-ΔL1=0.180-0.119=0.061mm

F2q=σs×S2=σs×(3.14×D ² /4-3.14×d ² /4)

=300×10 ⁶ ×3.14×[(30×10 ^-3 ) ² /4-(14×10 ^-3 ) ² /4]=165792N≈165.8KN

ΔL2=F2×L2/(E×S2)=σ2×L2/E=0.56×σs×L2/E

=0.56×300×10 ⁶ ×65×10 ^-3 /(200×10 ⁹ )=0.055mm

ΔL2q=F2q×L2/(E×S2)=σs×L2/E=300×10 ⁶ ×65×10 ^-3 /(200×10 ⁹ )=0.096mm

ΔL2z=ΔL2q-ΔL2=0.096-0.055=0.041mm<ΔL1z=0.061mm

It is indicated that the fastening bolt (3) reaches the yield strength ahead of the locking bolt (4), and the elastic elongation of the two increases synchronously is ΔL2z=0.041mm, and the locking bolt (4) starts from ΔL1=0.119mm and the fastening bolt (3) The required pulling force Fs when synchronously increasing ΔL2z=0.041mm is:

Fs=(ΔL1+ΔL2z)×E×S1/L1=(ΔL1+ΔL2z)×E×3.14×(d×10 ⁻³ /2) ² /L1

=(0.119+0.041)×200×10 ⁹ ×3.14×(14×10 ^-3 /2) ² /(120×10 ^-3 )=41029N≈41KN

When the tension of the locking bolt (4) is Fs, that is, the elastic elongation reaches ΔL1+ΔL2z=0.119+0.041=0.160mm (not yet reached ΔL1q=0.180mm), the fastening bolt (3) has reached the yield strength (ΔL2q=0.096mm) ).

When the 5.6 grade M30×2 solid bolt reaches the yield strength, the maximum load capacity is:

Σs × S = σs × 3.14 × D ² / 4 = 300 × 10 ⁶ × 3.14 × (30 × 10 ^-3 ) ² / 4 = 211950N ≈ 212KN

When the tightening bolt (3) reaches the yield strength, it can reach the maximum bearing capacity together with the locking bolt (4). The value is:

F2q+Fs=165.8+41=206.8KN≈207KN (slightly less than 212KN)

Considering the influence of the pre-tightening operation error ±15%, the upper limit Fmax1 and the lower limit Fmax2 of the maximum pre-tightening force of the fastening bolt (3) are:

Fmax1=1.15×Fmax=1.15×122.9=141.3KN

Fmax2=0.85×Fmax=0.85×122.9=104.5KN

Considering the influence of the pre-tightening operation error ±15%, the upper limit F11 and the lower limit F12 of the pre-tightening force of the locking bolt (4) are:

F11=1.15×σ1×S1=1.15×0.66×σs×S1=0.76×σs×3.14×d ² /4

=0.76×300×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4=35080N≈35.1KN

F12=0.85×σ1×S1=1.15×0.66×σs×S1=0.56×σs×3.14×d ² /4

=0.56×300×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4=25848N≈25.8KN

When the pre-tightening force of the locking bolt (4) is the upper limit F11=35.1KN or the lower limit F12=25.8KN, the maximum pre-tightening force Fmax and the stress σ2 of the fastening bolt (3) are:

1. When the maximum pre-tightening force of the fastening bolt (3) is the upper limit Fmax1=141.3KN, and the pre-tightening force of the locking bolt (4) is the lower limit F12=25.8KN, the maximum pre-tightening force Fmax of the fastening bolt (3) and The stress σ2 is:

Fmax=Fmax1-F12=141.3-25.8=115.5KN

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=115.5×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=209Mpa

Σ2/σs=209/300≈0.7<0.78 (in accordance with requirements)

2. When the maximum pre-tightening force of the fastening bolt (3) is the lower limit Fmax2=104.5KN, and the pre-tightening force of the locking bolt (4) is the upper limit F11=35.1KN, the maximum pre-tightening force Fmax of the fastening bolt (3) and The stress σ2 is:

Fmax=Fmax2-F11=104.5-35.1=69.4KN

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=69.4×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=126Mpa

Σ2/σs=126/300=0.42>0.4 (in accordance with requirements)

When the maximum pre-tightening force of the fastening bolt (3) is within the upper and lower limits, and the pre-tightening force of the locking bolt (4) is within the lower and upper limits, the pre-tightening force of the fastening bolt (3) is 0.7σs≥F2≥ 0.42σs. Explain that the maximum pre-tightening force of the fastening bolt (3) and the pre-tightening force of the locking bolt (4) are changed between the respective upper and lower limits. The pre-tightening force of the fastening bolt (3) is always between 0.42σs and 0.7σs. In the meantime, it can meet the requirements of pre-tightening and anti-loose.

Considering the maximum pre-tightening force of the fastening bolt (3) and the upper and lower limits of the pre-tightening force of the locking bolt (4), the maximum bearing capacity of the bolt shall be calculated according to the following four conditions (refer to 1.2 or 1.3 in the first calculation method) , using the minimum value to check the safety factor:

1. The pre-tightening force of the locking bolt (4) is the upper limit of 0.76σs, and the pre-tightening force of the fastening bolt (3) is the upper limit of 0.7σs;

2. The pre-tightening force of the locking bolt (4) is the lower limit of 0.56σs, and the pre-tightening force of the fastening bolt (3) is the lower limit of 0.42σs;

3. The pre-tightening force of the locking bolt (4) is the upper limit of 0.76σs, and the pre-tightening force of the fastening bolt (3) is the lower limit of 0.42σs:

4. The pre-tightening force of the locking bolt (4) is the lower limit of 0.56σs, and the pre-tightening force of the fastening bolt (3) is the upper limit of 0.7σs.

When the maximum preload of the fastening bolt (3) is the upper limit Fmax1=141.3KN, the stress σ2 is:

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=141.3×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=256Mpa

Σ2/σs=256/300=0.85

The tightening bolt (3) stress σ2 is 0.85σs, which belongs to “temporary over-standard”. Because the pre-tightening force of the locking bolt (4) is lower than 0.56σs, σ2 is only 0.7σs, which meets the requirements. The maximum pre-tightening force Fmax1 of the fastening bolt (3) is 141.3KN, which is less than Pmax (165.3KN), indicating that the external thread of the fastening bolt (3) should be no problem.

When the solid bolt, the locking bolt (4) or the fastening bolt (3) are ordinary bolts, the pre-tightening force should meet the following requirements when the yield strength is the same:

1. The physical bolt pre-tightening force generally requires 0.4σs ≤ P ≤ 0.58σs;

2. The tightening bolt (4) pre-tightening force requires 0.4σs ≤ F1 ≤ 0.78σs;

3. Tightening bolt (3) pre-tightening force requirement 0.4σs ≤ F2 ≤ 0.78σs;

4. When the maximum pre-tightening force Fmax of the fastening bolt (3) is equal to the physical bolt pre-tightening force P, σ2≤0.78σs is required.

According to the relevant content of the sixth calculation method, "take the 8.8-level M30×2 threaded joint of the coupling in Fig. 10 as an example" (the first calculation method) the stress σ2 of the fastening bolt (3):

Fmax1=1.15×Fmax=1.15×269=309.2KN

Fmax2=0.85×Fmax=0.85×269=228.7KN

F11=1.15×σ1×S1=1.15×0.68×σs×S1=0.78×σs×3.14×d ² /4

=0.78×640×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4=76807N≈76.8KN

F12=0.85×σ1×S1=1.15×0.58×σs×S1=0.58×σs×3.14×d ² /4

=0.58×640×10 ⁶ ×3.14×(14×10 ^-3 ) ² /4=57113N≈57.1KN

When the pre-tightening force of the locking bolt (4) is the upper limit F11=76.8KN or the lower limit F12=57.1KN, the maximum pre-tightening force Fmax and the stress σ2 of the fastening bolt (3) are:

1. When the maximum pre-tightening force of the fastening bolt (3) is the upper limit Fmax1=309.2KN, and the pre-tightening force of the locking bolt (4) is the lower limit F12=57.1KN, the maximum pre-tightening force Fmax and stress of the fastening bolt (3) Σ2 is:

Fmax=Fmax1-F12=309.2-57.1=252.1KN

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=252.1×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=456Mpa

Σ2/σs=456/640=0.71<0.78 (in accordance with requirements)

2. When the maximum pre-tightening force of the fastening bolt (3) is the lower limit Fmax2=228.7KN, and the pre-tightening force of the locking bolt (4) is the upper limit F11=76.8KN, the maximum pre-tightening force Fmax of the fastening bolt (3) and The stress σ2 is:

Fmax=Fmax2-F11=228.7-76.8=151.9KN

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=151.9×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=275Mpa

Σ2/σs=275/640=0.43>0.4 (in accordance with requirements)

When the maximum pre-tightening force of the fastening bolt (3) is within the upper and lower limits, and the pre-tightening force of the locking bolt (4) is within the lower and upper limits, the pre-tightening force of the fastening bolt (3) is 0.71σs≥F2≥ 0.43σs. Explain that the maximum pre-tightening force of the fastening bolt (3) and the pre-tightening force of the locking bolt (4) are changed between the respective upper and lower limits. The pre-tightening force of the fastening bolt (3) is always between 0.43σs and 0.71σs. In the meantime, it can meet the requirements of pre-tightening and anti-loose.

1. The pre-tightening force of the locking bolt (4) is the upper limit of 0.78σs, and the pre-tightening force of the fastening bolt (3) is the upper limit of 0.71σs;

2. The pre-tightening force of the locking bolt (4) is the lower limit of 0.58σs, and the pre-tightening force of the fastening bolt (3) is the lower limit of 0.43σs;

3. The pre-tightening force of the locking bolt (4) is the upper limit of 0.78σs, and the pre-tightening force of the fastening bolt (3) is the lower limit of 0.43σs;

4. The pre-tightening force of the locking bolt (4) is the lower limit of 0.58σs, and the pre-tightening force of the fastening bolt (3) is the upper limit of 0.71σs.

When the maximum pre-tightening force of the fastening bolt (3) is the upper limit Fmax1=309.2KN, the stress σ2 is:

Σ2=Fmax/S2=Fmax/(3.14×D ² /4-3.14×d ² /4)

=309.2×10 ³ /(3.14×30 ² ×10 ^-6 /4-3.14×14 ² ×10 ^-6 /4)=559Mpa

Σ2/σs=559/640=0.87

The stress σ2 of the fastening bolt (3) is 0.87σs, which belongs to “temporary over-standard”. Because the pre-tightening force of the locking bolt (4) is 0.58σs at the lower limit, σ2 is only 0.71σs, which meets the requirements.

When σ/σs=0.8, the maximum pre-tightening force Pmax of the 8.8-class M30×2 solid bolt is:

Pmax = σ × S = 0.8 × σs × 3.14 × D 2 /4=0.8×640×10 6 × 3.14 × (30 × 10 -3) 2/4

=361728N≈361.7KN

The maximum pre-tightening force of the 8.8-class M30×2 solid bolt is Pmax=361.7KN, which is greater than the upper limit of the maximum pre-tightening force Fmax1 (309.2KN) of the fastening bolt (3), indicating that the external thread of the fastening bolt (3) should be no problem.

If the bolted joint is subjected to an impact load, the preload of the locking bolt (4) and the fastening bolt (3) can be taken as 0.4 σs.

The diameter of the fastening bolt (3) and the locking bolt (4) and the preload force calculation selection process:

1. Determine the pre-tightening force P of the solid bolt;

2. The diameter d of the locking bolt (4) is selected by the first, second, third, fourth, fifth or sixth calculation method;

3. Determine the pre-tightening force F1 of the locking bolt (4), generally 0.68σs (high-strength bolt) or 0.66σs (ordinary bolt), and the pre-tightening force F2 of the fastening bolt (3) takes the remaining pre-tightening of the solid bolt The force is P-F1;

4. The maximum pre-tightening force Fmax of the fastening bolt (3) is equal to the physical bolt pre-tightening force P to check the stress σ2 of the fastening bolt (3), and the requirement σ2 is not more than 0.8σs (high-strength bolt) or 0.78σs (ordinary bolt) );

5. Calculate the maximum load capacity of the bolt according to the four conditions of taking the upper limit of the tightening bolt (3) and the locking bolt (4) and taking the upper limit and the upper and lower limits respectively. ;

6. Calculate the upper limit Fmax1 and the lower limit Fmax2 of the maximum pre-tightening force of the fastening bolt (3) according to the pre-tightening operation error ±15%;

7. Calculate the upper limit F11 and the lower limit F12 of the pre-tightening force of the locking bolt (4) according to the pre-tightening operation error ±15%;

8. Calculate the stress σ2 of the tightening bolt (3) by subtracting the upper limit Fmax1 of the maximum pre-tightening force of the tightening bolt (3) from the lower limit of the pre-tightening force F12 of the locking bolt (4), and request that σ2 is not greater than 0.8σs (high-strength bolt) or 0.78σs (ordinary bolt);

9. Calculate the stress σ2 of the tightening bolt (3) by subtracting the lower limit Fmax2 of the maximum pre-tightening force of the tightening bolt (3) from the upper limit of the pre-tightening force F11 of the locking bolt (4), and request that σ2 is not less than 0.4σs (high-strength bolts or ordinary bolts).

If the phenomenon does not meet the requirements in the calculation process, it can be treated by reducing the diameter of the locking bolt (4) or using the high yield strength fastening bolt (3).

The physical bolt and the calculation method of the present invention will be described as a reference in the above calculation.

In the embodiment of Fig. 1, the effective tension length L1 = B of the locking bolt (4), and the effective tensile length of the fastening bolt (3) is the thickness of the left coupling (1). In the embodiment of Fig. 3, the effective tensile length of the locking bolt (4) is the height of the head of the fastening bolt (3) and the sum of the thickness of the fastening nut (7), the flat washer (6) and the two coupling members, and the fastening bolt (3) The effective tensile length is the sum of the thicknesses of the two coupling members. The effective tensile length of the bolts of the embodiment of Figures 5 and 6 is the same as that of the embodiment of Figure 3. The effective tensile length of the bolt of the embodiment of Figure 12 is the same as that of the embodiment of Figure 10. In the embodiment of Fig. 13, the effective tensile length of the locking bolt (4) is the sum of the head height of the fastening bolt (3) and the thickness of the fastening nut (7), the "bowl type" gasket (10) and the two coupling members. The fastening bolt (3) has an effective tensile length which is the sum of the thicknesses of the two coupling members. The bolt effective length of the embodiment of Figure 14 is the same as that of the embodiment of Figure 10. In the embodiment of Figure 16, the effective tension length of the locking bolt (4) is the length of the rigid sleeve (11) plus the fastening nut (7), the "bowl type" gasket (10) and the thickness of the two coupling members, The effective tensile length of the fastening bolt (3) is the length of the rigid sleeve (11) and the sum of the thicknesses of the two coupling members. In the embodiment of Fig. 17, the effective tensile length of the locking bolt (4) is the height of the head of the fastening bolt (3) and the sum of the thickness of the flat pad (6) and the two coupling members, and the effective tensile length of the fastening bolt (3) For the right coupling (2) thickness.

The above calculation method is applicable to the embodiments of FIGS. 1, 3, 5, 6, 10, 12, 13, 14, and 16, if the yielding of the locking bolt (4) or the fastening bolt (3) The strength or effective tensile length changes, and the diameter of the locking bolt (4) or the maximum load capacity of the bolt may also change.

If the tightening bolt (3) or the solid bolt is a coarse thread, consider the influence of the depth of the thread on the cross-sectional area when calculating the cross-sectional area. Therefore, the diameter of the fastening bolt (3) or the solid bolt is calculated by the bottom diameter of the thread. More reasonable. Because the diameter of the locking bolt (4) is relatively small, the depth of the thread is small, and the center of the bolt body is not made of holes, the cross-sectional area does not change, and the nominal diameter can be generally calculated.

The pre-tightening force is controlled by the tightening torque, the error is about ±25%; the pre-tightening force is controlled by the nut (or bolt) angle, and the error is about It is ±15%; the pre-tightening force is controlled according to the tightening torque and the nut rotation angle, which is higher than the method of controlling the pre-tightening force by the tightening torque alone or by the nut (or bolt) rotation angle, and the pre-tightening force error should be less than ±15%. If the fastening bolt (3) is attached with a strain gauge on the inner wall of the center hole (the position is within the effective stretch length of the rod), the resistance strain gauge is used to measure and control the tension of the bolt, that is, the preload force, to reach the desired After the preload, remove the strain gauge and screw into the lock bolt (4). The tightening force of the tightening bolt (3) is less than ±1%. For the locking bolt (4), if the pre-tightening force is checked by measuring the elongation value, the pre-tightening force error is about ± 5%. If the force-measuring bolt is used directly, the pre-tightening force can be accurate to kilogram. If the tightening bolt (3) or the locking bolt (4) uses a ring washer sensor to control the preload, the preload force error should be less than ±15%. If the pre-tightening force error is selected ±15% for calculation and the calculated value meets the requirements, the actual error value of the bolt pre-tightening force can be controlled within ±15%, indicating that the actual pre-tightening force of the bolt definitely meets the requirements.

If the tightening bolt (4) with a small cross-sectional area and a long length has a lower pre-tightening force F1, the tightening bolt with a larger cross-sectional area and a shorter length (3) takes a higher value of the pre-tightening force F2. The maximum preload force Fmax of the fixing bolt (3) is equal to the pretensioning total pulling force P. When the pre-tightening force F1 of the locking bolt (4) is gradually increased from a lower value to a higher value, the pre-tightening force F2 of the fastening bolt (3) is gradually decreased, so the locking bolt (4) can be adjusted according to the actual situation. Adjust the pre-tightening force F2 of the fastening bolt (3) to prevent the fastening bolt (3) from being overloaded, and the locking bolt (4) has a relatively large elastic elongation and is not easily overloaded.

After tightening the center hole of the bolt (3), the problem of poor permeability of the large-diameter high-strength bolt during heat treatment is solved. The bolt is easily hardened during quenching treatment, which improves the heat treatment effect of the bolt and stabilizes the quality. Suitable for mass production, and does not need to reduce working stress when in use. If the locking bolt (4) is made of high-strength bolt with a diameter of 30mm, the wall thickness of the fastening bolt (3) is 30mm, and the inner diameter of the center hole of the fastening bolt (3) is 31mm, then the maximum of the fastening bolt (3) The theoretical diameter (outer diameter) Dmax is 91mm (Dmax=30×2+31=91mm), and it can be hardened during quenching treatment. The quality is stable. It can be used as a high-strength bolt and used with the locking bolt (4). After that, it can meet the high strength requirements and anti-loose requirements of the larger diameter bolts for special occasions. Compared with the use of ordinary bolts, the diameter, volume and weight are relatively small, and the size and structure of the mechanical or component can be reduced or simplified. Have a stronger market competitiveness.

If the head bolt size of the fastening bolt (3) is the same as that of the solid bolt, the material of the fastening bolt (3), the locking bolt (4), and the machining process are the same as those of the solid bolt, and the bolt (3) rod and head are tightened. The shear strength of the joint should meet the requirements. If the material or processing technique of the locking bolt (4) is changed compared with the fastening bolt (3), the yield strength of the locking bolt (4) is increased or the fastening bolt (3) is made of a high-strength bolt of a larger diameter. The thickness and outer diameter of the head of the fastening bolt (3) should be appropriately increased to ensure that the shear strength of the joint between the rod and the head of the fastening bolt (3) is not less than that when the fastening bolt (3) reaches the tensile strength. The shear stress generated, the increase in the outer diameter of the head of the fastening bolt (3) is to control the contact surface contact stress of the head of the fastening bolt (3) and prevent plastic annular indentation on the surface of the coupling.

The shear strength of the anti-rotation nut (9) locking thread and the fastening thread connection shall not be less than the shear stress generated by the fastening bolt (3) reaching the maximum pre-tension upper limit, locking the thread and fastening The compressive strength of the threaded joint shall not be less than the stress generated when the locking bolt (4) reaches the tensile strength.

The thread of the fastening bolt (3) and the locking bolt (4) can be made according to relevant standards. No matter whether it is left-handed or right-handed, the thread has no breaking point and does not damage the strength of the thread, which is beneficial to improve the pre-tightening force and the joint strength.

The above embodiments and calculation methods are only for explaining the technical solutions of the present invention, and are not intended to limit the present invention, and are all protected contents within the scope of the technical solutions of the present invention.

The "double bolt anti-loose method" described in the present invention is a new method for preventing loose bolts, and has a simple structure and convenience. Practical, the manufacturing process of the reverse rotation nut (9) and the active nut is basically the same. The fastening bolt (3) only has one more hole in the center of the rod than the current bolt, and the manufacturing cost is relatively low, and the high-strength bolt is enlarged. Application range (mainly refers to the large-diameter high-strength bolt with stable quality, higher strength than the existing high-strength bolts, can meet the needs of some special occasions), and has application repeatability, so the prospect of industrial applicability is relatively broad.

Claims

The patent relates to a double bolt anti-loose method, relating to a coupling member, a bolt and a nut. The utility model is characterized in that a screw hole or a hole is formed on the coupling member, and the external thread diameters of the locking bolt and the fastening bolt are different and the opposite directions are reversed. The center of the rod body of the fastening bolt is fastened, and the fastening bolt is coupled with the fastening screw hole or the fastening nut. The locking bolt passes through the center hole of the fastening bolt body and the locking screw hole or the lock nut is coupled to the joint member. Fasten the gasket; the gasket and the lock nut, the fastening nut are welded into a "3 in 1" structure, or the gasket and the lock nut are integrally formed and the fastening nut is welded into a "2 in 1" structure, and the pad is also provided. Another "2-in-1" structure in which the piece and the fastening nut are integrally welded with the lock nut. The internal diameters of the lock nut and the fastening nut are different and the opposite directions are reversed. The fastening bolts are coupled to the fastening nut and the lock. The tightening bolts are connected to the lock nut through the center hole of the fastening bolt body to jointly fasten the coupling member; the "reverse rotation nut" is provided with two sets of internal threads having different diameters and opposite directions of rotation, and the fastening bolts are coupled with "reverse rotation" To the nut", lock The coupling bolt through the central bore of the fastening bolt shaft "de-rotation to the nut", common to the coupling member is fastened.
A double bolt anti-loose method according to claim 1, wherein the coupling member is machined with two screw holes having different diameters and oppositely rotating threads on the same center axis of the center of the circle.
A double bolt locking method according to claim 1, wherein the "reverse rotation nut" is a through hole type or a sealed type structure.
A double bolt anti-loose method according to claim 1, wherein the "reverse rotation nut" is a "single outer polygon angle", a "double outer polygon angle" or a circular shape.
A double bolt locking method according to claim 1, wherein the head of the locking bolt or the lock nut presses the head of the fastening bolt.
A double-bolt anti-loose method according to claim 1, wherein the fastening bolt and the locking bolt have the same elastic elongation when the working load is taken.