CN111637136A - A single-sided preload control bolt assembly - Google Patents

Abstract

The invention provides a single-sided installation of a pre-tightening control bolt assembly, comprising a pre-tightening control bolt and an indicator washer sleeved on the pre-tightening control bolt. The bolt polished rod, the threaded rod, the broken neck section and the wrench tooth section, the broken neck section is provided with a broken neck groove extending along the circumferential direction, and the indicating washer is made of a stress-induced shape memory alloy. The invention can realize single-sided installation, convenient installation, simple component structure and good manufacturing process, and can control the maximum preload force and the minimum preload force simultaneously through the neck-breaking groove and the indicator washer, so as to realize precise control of the preload force and prevent loosening. The effect is remarkable.

Description

A single-sided preload control bolt assembly

technical field

The invention belongs to the field of fastener design and manufacture, in particular to a single-sided installation of a pre-tightening control bolt assembly.

Background technique

Preload can improve the reliability, anti-loosening ability and thread fatigue strength of the bolted connection, enhance the tightness and rigidity of the connection, and prevent the sliding of the bolted connection under lateral load. Therefore, preload control is required for most threaded connections in engineering.

To ensure that the connection of the threaded parts can overcome various static or dynamic external forces on the connected parts, the tightening requirements for the connection of the threaded parts are designed to generate a certain pre-tightening force on the parts, and the pre-tightening force is the tensile force of the thread pair. 0.3 to 0.8 times the value, depending on the working conditions. There are many tightening control methods to achieve this pre-tightening force, including the simple manual method of wrench tightening, torque method, torque angle method, yield limit control method and bolt pre-extension method, force measuring washer control method, built-in sensor law, etc.

Among these methods, the tightening torque control pre-tightening force and torque angle method are simple to operate, easy to implement, do not require complicated instruments and equipment, and have been widely used in engineering. The bolt elongation method, the force-measuring gasket method, and the built-in sensor method have higher accuracy, but have high measurement costs and limited application scenarios, and are generally used in fields that require precise control.

How to realize the convenience of preload control while meeting the more precise requirements for preload control in engineering is an urgent requirement for fastener design.

Shape memory alloys are materials composed of two or more elements that have a shape memory effect through thermoelasticity and martensitic transformation and their inversion. Broadly speaking, shape memory alloys exist in one of two crystal structures, commonly referred to as martensite (low temperature phase) and austenite (high temperature phase). Shape memory alloys can form a shape when in their high temperature austenite phase. When the shape memory alloy is in its lower temperature martensite, the shape memory alloy device deforms and the device will retain its deformed shape until it is heated back to the austenite phase, whereby it returns to its original shape, which is called for the shape memory effect.

The austenite transformation temperature will vary with the alloy used to form the fastener, for example a nickel-rich nickel-titanium alloy or a nickel-titanium-cobalt-iron alloy with cobalt or iron instead of nickel in the alloy chemical structure will cause the austenite to begin The transition temperature is below room temperature. Therefore, nickel-titanium-cobalt alloys that are sensitive to stress near the working temperature of the fastener can be selected as the stress indicating washer. When the stress is below a certain stress value, the gasket can recover to its original shape.

SUMMARY OF THE INVENTION

In view of this, the present invention aims to provide a single-side installation pre-tightening control bolt assembly, which can realize single-side installation, is convenient to install, and at the same time, the assembly has a simple structure and good manufacturing process, and can control the maximum pre-tightening force at the same time. And the minimum preload force to achieve precise control of the preload force, and the anti-loosening effect is remarkable.

In order to achieve the above object, the technical scheme of the present invention is achieved in this way:

A single-sided installation of a pre-tightening control bolt assembly, comprising a pre-tightening control bolt and an indicator washer sleeved on the pre-tightening control bolt, wherein the pre-tightening control bolt comprises a bolt head, a smooth bolt rod, a thread which are fixedly connected in sequence. A rod, a broken neck section, and a wrench tooth section, the broken neck section is provided with a broken neck groove extending along the circumferential direction, and the indicator washer is made of a stress-induced shape memory alloy.

Further, the indicating washer is made of TiNiFe shape memory alloy or TiNiCoFe shape memory alloy.

Further, the indicator washer is an inner tooth type washer, including an outer ring and upwardly protruding inner teeth, the outer ring is a circular sheet with a central circular hole, and the inner teeth are circumferentially evenly distributed on the outer ring. inside.

Further, the number of teeth of the internal teeth is 10-20 teeth.

Further, the outer diameter of the outer ring is twice the diameter d of the polished rod of the bolt, the inner diameter of the outer ring is the sum of the diameter d of the polished rod of the bolt and the diameter of the fillet under the head, and the thickness of the outer ring is the diameter of the polished rod of the bolt d. 0.1 to 0.3 times the thickness of the inner teeth, and the upward protrusion of the inner teeth is 0.5 to 2 times the thickness of the outer ring.

Further, the preload control bolts are made of high-strength stainless steel.

Further, the surface of the wrenching tooth segment is provided with dodecagonal teeth, spline teeth or five-spline teeth, and the diagonal dimension of the wrenching tooth segment is between the small diameter and the middle diameter of the thread of the threaded rod.

Further, the bolt head is a flat head, a pan head or an oblate head.

Further, the longitudinal section of the broken neck groove is triangular, the transverse section of the broken neck groove is circular, and the inner diameter of the deepest transverse section of the broken neck groove is 0.35-0.7 times the diameter d of the polished rod of the bolt.

Further, the inner diameter of the deepest transverse section of the broken neck groove is 0.55 times the diameter d of the polished rod of the bolt, and the bottom of the broken neck groove is rounded with rounded corners.

Compared with the prior art, the single-sided installation of the preload control bolt assembly of the present invention has the following advantages:

The invention can realize single-sided installation, convenient installation, simple component structure and good manufacturing process, and can control the maximum preload force and the minimum preload force simultaneously through the neck-breaking groove and the indicator washer, so as to realize precise control of the preload force and prevent loosening. The effect is remarkable; based on the dual action design of installation torque control and quick visual inspection, the torque control is different from the wrenching structure in the screw bottom hole in the single-sided installation connection pair high lock bolts widely used in the aerospace field. The external wrench structure composed of the segment and the prefabricated neck groove makes the wrench structure convenient for upsetting extrusion plastic processing and manufacturing, and the process forming is better; the quick visual inspection adopts the pre-tightening indicator washer, which adopts a stress-induced titanium-nickel series shape. Made of memory alloy, the shape is a convex inner tooth circular washer. When the bearing stress exceeds the design value, the indicating washer becomes flat. When the bearing stress is less than the design value, the middle is convex, which is convenient for observation; When twisting the tooth segment, it is not necessary to make holes at the bottom of the high-lock bolt screw to ensure that the bearing capacity of the threaded part is not weakened. Therefore, a shorter threaded rod can be used, thereby reducing the weight of the connection structure.

Description of drawings

The accompanying drawings constituting a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

1 is a structural diagram of the present invention in an initial state;

2 is a three-dimensional structural view of the present invention in an initial state;

Figure 3 is a front view of the indicator washer according to the present invention in an initial state;

Figure 4 is a perspective view of the indicator washer according to the present invention in an initial state;

FIG. 5 is a structural diagram of the present invention in a pressed state;

FIG. 6 is a three-dimensional structural view of the present invention in a pressed state;

FIG. 7 is a top view of the indicator gasket according to the present invention in a pressed state;

FIG. 8 is a perspective view of the indicator gasket according to the present invention in a pressed state;

FIG. 9 is a side view of the indicator gasket according to the present invention in a pressed state.

Description of reference numbers:

1. Pre-tightening control bolt; 11. Bolt head; 12. Bolt polished rod; 13. Threaded rod; 14. Broken neck section; 141. Broken neck groove; ; 22. Internal teeth.

Detailed ways

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

In the description of the present invention, it should be understood that the terms "center", "portrait", "horizontal", "top", "bottom", "front", "rear", "left", "right", " The orientation or positional relationship indicated by vertical, horizontal, top, bottom, inner, outer, etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and The description is simplified rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first", "second", etc. are used for descriptive purposes only, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second", etc., may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Example 1

A single-side-mounted preload control bolt assembly, as shown in Figures 1-9, includes a preload control bolt 1 and an indicator washer 2 sleeved on the preload control bolt 1.

The pre-tightening control bolt 1 includes a bolt head 11, a bolt polished rod 12, a threaded rod 13, a broken neck section 14, and a wrench tooth section 15 that are fixedly connected in sequence. The broken neck section 14 is provided with a circumferentially extending Broken neck groove 141 .

Compared with the conventional male head bolt, the single-sided installation of the pre-tightening control bolt 1 assembly of the present invention does not require the head to undertake the wrenching function, and can realize single-sided installation. Tooth segment 15, a neck-breaking groove 141 is designed for transitional connection between this segment and the threaded part to achieve maximum preload control.

Compared with the high-lock bolt, the single-sided installation of the pre-tightening control bolt 1 component of the present invention adopts an external wrench structure, which can precisely extrude the wrench tooth segment 15 when upsetting and extruding the diameter of the thread blank, and the processing technology is better. it is good. Due to the wrench tooth segment 15, there is no need to make holes at the bottom of the high-lock bolt screw, so as to ensure that the bearing capacity of the threaded part is not weakened. Therefore, a shorter threaded rod 13 can be used, so that the weight of the connection structure can be reduced.

The indicating washer 2 is an inner toothed washer, including an outer ring 21 and upwardly protruding inner teeth 22. The outer ring 21 is a circular sheet with a central hole, and the inner teeth 22 are evenly distributed on the outer ring. Inside of circle 21. In the initial installation state (without pre-tightening), as shown in Figure 1, there is a visible gap with the lower support surface of the bolt head 11. In the working state (pre-tightened), as shown in Figure 5, the indicator washer 2 is in contact with the lower support surface of the bolt head 11. That is to say, when the bearing stress exceeds the design value, the indicating washer 2 becomes flat; when the bearing stress is less than the design value, the middle of the indicating washer 2 is convex, enabling quick visual inspection and minimum preload control.

The outer diameter of the outer ring is 2 times the diameter d of the polished rod of the bolt, the inner diameter of the outer ring is the sum of the diameter d of the polished rod of the bolt and the diameter of the fillet under the head, and the thickness of the outer ring is 0.1～1 of the diameter d of the polished rod of the bolt. 0.3 times. The upward protrusion of the inner teeth is 0.5 to 2 times the thickness of the outer ring, which not only helps the inner teeth to become flat under the action of the bolt pre-tightening force and realizes the control of the minimum pre-tightening force, but also helps when the bolt is pre-tightened. When the tightening force is attenuated to below the minimum preload force due to the combined action of complex alternating loads, vibration shocks, collapse of contact surfaces, surface friction and material creep, the instructing washer 2 will try to restore its original shape due to its memory function. The elastic springback is formed to offset the decrease in the preload force, so that the bolt preload force is maintained at a relatively stable level.

The material of the indicator washer 2 is a stress-induced titanium-nickel-iron (TiNiFe) shape memory alloy, and the pre-tightening control bolt 1 is an A2-70 304 stainless steel bolt with a strength grade of 700MPa. The performance parameters of the indicator washer 2, the size of the broken neck groove 141, the installation torque, the maximum preload force, the minimum preload force, and the length of the threaded rod 13 of the preload control bolt assembly are shown in Table 1.

Table 1 Performance parameter table of embodiment 1

Using method of the present invention:

First, install the indicator washer 2 in the bolt polished rod 12 , insert the assembly into the prefabricated hole of the connected plate together, and screw the corresponding nut on the threaded rod 13 . When the bolt is fixed with a driving tool (the chuck), the driving nut rotates; at the same time, another chuck clamps the wrench tooth segment 15, and uses the reverse torque to break the neck-breaking groove 141. The driver tool exits to complete the component installation. At this time, the preload of the bolt is the upper limit of the preload.

The installation process of the preload bolt assembly is mainly controlled by the torque, so when the assembly is installed, the assembly should ensure good consistency, clean surface and good lubrication.

Example 2

The difference between this embodiment and Embodiment 1 is that the material of the indicator washer 2 is a titanium-nickel-cobalt-iron (TiNiCoFe) alloy, and the pre-tightening control bolt 1 is an A2-80 304 stainless steel bolt with a strength grade of 800MPa. The performance parameters of the indicator washer 2, the size of the broken neck groove 141, the installation torque, the maximum preload force, the minimum preload force, the length of the threaded rod 13 and other performance parameters of the preload control bolt assembly are shown in Table 1.

Table 2 Performance parameter table of embodiment 2

Comparative Example 1

Using traditional 8.8 grade carbon steel bolt products, the product specifications, installation torque, maximum preload force, minimum preload force, length of threaded rod and other performance parameters are shown in Table 3.

Table 3 Performance parameters of traditional 8.8 grade carbon steel bolt products

Product specification d/mm Mounting torque/N m Maximum preload force/KN Minimum preload force/KN Length of threaded rod/mm M6 11.2 17.5 4.6 9 M8 28.0 31.2 24.5 10.3 M10 71.4 48.9 38.3 11.5

It can be seen from Table 1, Table 2 and Table 3 that the length of the threaded rods of Examples 1 and 2 is less than that of Comparative Example 1, and the maximum preload force of Examples 1 and 2 is not much different from the minimum preload force (the difference is not more than 5KN). ), and the difference between the maximum preload force and the minimum preload force of Comparative Example 1 is relatively large (the maximum difference is 12.9KN), which shows that the present invention controls the maximum preload force and the minimum preload force at the same time, and the preload force is controlled more accurately .

To sum up, the single-side-mounted preload control bolt assembly of the present invention is based on the dual-action design of installation torque control and quick visual inspection. The torque control is different from the single-sided installation connection pair widely used in the aerospace field - the inner wrenching structure of the screw bottom hole in the high-lock bolt. structure, so that the wrench structure can be convenient for upsetting extrusion plastic processing and manufacturing, and the process forming is better.

The quick visual inspection uses a pre-tightened indicator washer 2, which is made of stress-induced titanium-nickel-based shape memory alloy, and has an internal tooth-type washer with a raised center. When the bearing stress exceeds the design value, the indicating washer 2 becomes flat; when the bearing stress is less than the design value, the middle thereof is convex.

Based on the special design, when the preload stress level exceeds the lower limit of the preload (for 8.8-grade threaded connections, the guaranteed stress is 600MPa. The lower limit of the preload is 0.9 times the guaranteed stress, which is 540±25MPa ), indicating that the inner teeth of washer 2 will be flat. When the pretightening force reaches the lower limit of the product pretightening force, the outer dimension of the inner tooth washer is determined according to the stiffness design of the inner tooth washer. At this point, the gap between the indicator washer 2 and the bearing surface of the bolt will be greatly reduced to a close fit. Continue to apply the installation torque. At this time, the reverse torque acting simultaneously on the nut and the wrench tooth segment 15 will screw off the prefabricated neck-breaking groove 141. At this time, the pre-tightening force reaches the upper limit of the product pre-tightening force of 600MPa.

During the use of the preload control bolt assembly, when the bolt preload is attenuated to below the minimum preload due to complex alternating loads, vibration shocks, collapse of the contact surface, surface friction and material creep, etc. The indicator washer 2 will try to return to the original shape due to the memory function, forming elastic rebound to offset the decrease in the preload force, so that the bolt preload force is maintained at a relatively stable level.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. A single-sidedly installed pre-tightening control bolt assembly, characterized in that it comprises a pre-tightening control bolt and an indicator washer sleeved on the pre-tightening control bolt, and the pre-tightening control bolt comprises bolts that are fixedly connected in sequence The head, the bolt polished rod, the threaded rod, the broken neck section and the wrench tooth section, the broken neck section is provided with a broken neck groove extending along the circumferential direction, and the indicating washer is made of a stress-induced shape memory alloy. 2 . The pre-tightening control bolt assembly for single-side installation according to claim 1 , wherein the indicator washer is made of titanium-nickel-iron shape memory alloy or titanium-nickel-cobalt iron shape memory alloy. 3 . 3 . The single-sided pre-tightening control bolt assembly according to claim 1 , wherein the indicator washer is an inner toothed washer, comprising an outer ring and an upwardly protruding inner tooth, and the outer ring is a belt. 4 . A circular sheet with a central hole, and the inner teeth are evenly distributed on the inner side of the outer ring in the circumferential direction. 4 . The single-side mounted pre-tightening control bolt assembly according to claim 3 , wherein the number of teeth of the inner teeth is 10-20 teeth. 5 . 5 . The single-sided pre-tightening control bolt assembly according to claim 3 , wherein the outer diameter of the outer ring is twice the diameter d of the polished rod of the bolt, and the inner diameter of the outer ring is the diameter d of the polished rod of the bolt. 6 . The thickness of the outer ring is 0.1-0.3 times the diameter d of the polished rod of the bolt and the sum of the diameter of the fillet under the head, and the upward protrusion of the inner teeth is 0.5-2 times the thickness of the outer ring. 6. The single-side mounted pre-tightening control bolt assembly according to claim 1, wherein the pre-tightening control bolt is made of high-strength stainless steel. 7 . The single-sidedly mounted pre-tightening control bolt assembly according to claim 1 , wherein the surface of the wrenching tooth segment is provided with dodecagonal teeth, spline teeth or five spline teeth, and the wrench The diagonal dimension of the tooth segment is between the minor and pitch diameters of the thread of the threaded rod. 8 . The single-side mounted pre-tightening control bolt assembly according to claim 1 , wherein the bolt head is a flat head, a pan head or an oblate head. 9 . 9 . The single-sidedly installed pre-tightening control bolt assembly according to claim 1 , wherein the longitudinal section of the broken neck groove is triangular, the transverse section of the broken neck groove is circular, and the deepest part of the broken neck groove is in the shape of a circle. 10 . The inner diameter of the transverse section of the bolt is 0.35 to 0.7 times the diameter d of the polished rod of the bolt. 10. The single-sidedly installed pre-tightening control bolt assembly according to claim 9, wherein the inner diameter of the deepest transverse section of the neck-breaking groove is 0.55 times the diameter d of the polished rod of the bolt, and the bottom of the neck-breaking groove is inverted rounded corners.

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