Combined nut for double-end bolt and double-end bolt assembly

Abstract

The invention provides a combined nut for a double-end bolt and a double-end bolt assembly, and belongs to the technical field of bolt connection. The combined nut comprises a protection nut embedded in the structure body and a fracture nut connected with the end, extending out of the structure body, of the stud, internal threads of the protection nut and the fracture nut are improved meter threads or MJ threads, or the internal threads of the fracture nut are standard meter threads or MJ threads. The internal thread of the protection nut is an improved metro thread or an MJ thread, the improved thread is that a continuous groove is formed in the tooth bottom of the internal thread, the maximum width of the groove exceeds # imgabs0, the groove side wall of the groove is machined to the tooth side, and therefore the tooth thickness of the internal thread tooth is reduced, the rigidity of the internal thread tooth is reduced, and the service life of the protection nut is prolonged. The rigidity of the internal thread teeth of the protective nut is smaller than that of the internal thread teeth of the broken nut, the stress of the external thread teeth of the stud at the protective nut is reduced, and when the stud is subjected to fatigue fracture, the probability that the fracture position occurs at the broken nut is larger.

Description

Technical Field

[0001] The invention relates to a combined nut for a stud bolt and a stud bolt assembly, belonging to the technical field of bolt connection. Background Art

[0002] The stud bolt assembly is a common bolt fastener with a simple structure, easy to use, and a wide range of application scenarios. For example, the anchor bolts and blade bolt assemblies in the wind power industry are stud bolt connection structures. The blade bolts can refer to the wind turbine blade root structure and blade disclosed in the Chinese utility model patent with authorization announcement number CN202431457U, in which the blade root is pre-embedded with an embedded nut, one end of the stud bolt extends into the blade root and connects with the embedded nut, and the other end extends out of the blade root. It is fixed to the pitch flange by the fastening nut during installation. The embedded nut, fastening nut and stud bolt constitute a stud bolt assembly, and the internal thread pitch of the embedded nut and the fastening nut is equal to the external thread pitch at both ends of the stud bolt.

[0003] During the operation of a wind turbine, as the blades are stressed, the stud bolts at the root of the blades will be subjected to alternating loads such as impact and vibration. Under the action of alternating loads, the stud bolts may break in extreme cases. The fracture position of the stud bolts is random. It may break at the first thread that matches the embedded nut, or it may break at the first thread that matches the fastening nut. At present, it is impossible to accurately predict the fracture position of the stud bolts. If the fracture position of the stud bolt is located at the matching position with the fastening nut, the stud bolt still has a part that overhangs outside the blade. Using this part as the force application position, it is relatively easy to remove the remaining stud bolts from the root of the blade and then replace them with new stud bolts. However, if the fracture position of the stud bolt is located at the matching position with the embedded nut, the broken bolt head is attached to the embedded nut and located inside the blade, making it very difficult to remove, which brings great trouble to the on-site replacement operation. Of course, if the embedded nut is embedded in other structures, such as the concrete foundation under the wind turbine tower, if the embedded part of the stud bolt (also called wind turbine anchor bolt) breaks, the same technical problem exists. Summary of the invention

[0004] The object of the present invention is to provide a combination nut for stud bolts to solve the problem that the fracture position of the existing stud bolts cannot be predicted, resulting in the broken bolt head being located inside the structure when the fracture position of the stud bolt is located at the matching position with the embedded nut, which is very difficult to remove and causes great trouble to on-site replacement operations; the object of the present invention is also to provide a stud bolt assembly to solve the above-mentioned problem.

[0005] To achieve the above purpose, the combined nut for stud bolts in the present invention adopts the following technical solution:

[0006] A combination nut for stud bolts, comprising a protective nut for pre-embedded in a structure and a breaking nut for connecting with one end of the stud bolt extending outside the structure, the internal thread of the breaking nut is a standard metric thread or MJ thread, the pitch of the protective nut is P, the internal thread of the protective nut is an improved metric thread or MJ thread, the internal thread root of the protective nut is provided with a continuous groove, and the internal thread tooth profile comprises a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to a groove wall on one side of the groove, a groove bottom segment corresponding to a groove bottom of the groove, a groove side straight line segment corresponding to a groove wall on the other side of the groove, and a tooth side straight line segment, and the maximum width of the groove is g b ,

[0007] The beneficial effect of the above technical solution is that: the present invention is a pioneering invention, and the proposed combination nut for stud bolts includes a protective nut and a breaking nut. The protective nut is pre-buried in the structure, and the breaking nut is connected to the end of the stud bolt extending outside the structure. Measures are set to ensure that the end of the stud bolt assembly that cooperates with the protective nut will not break when subjected to alternating loads, while the end that cooperates with the breaking nut will break. Specifically, the internal thread of the breaking nut is a standard metric thread or MJ thread, and the internal thread of the protective nut is an improved metric thread or MJ thread. The improvement is that the internal thread bottom of the protective nut is provided with a continuous groove, and the internal thread tooth profile includes a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to the groove wall on one side of the groove, a groove bottom segment corresponding to the groove bottom of the groove, a groove side straight line segment corresponding to the groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and the maximum width of the groove is g. b , in, It is the root width of the standard metric internal thread or MJ internal thread, which means that the groove sidewall has been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread tooth, thus reducing the rigidity of the internal thread tooth. b Less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0008] In summary, in the present invention, the tooth thickness of the internal thread teeth of the protective nut is reduced, the rigidity of the internal thread teeth of the protective nut can be reduced, and the broken nut does not change, so the rigidity of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread tooth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, and the stud bolt can be conveniently removed from the structure, thereby facilitating on-site replacement operations.

[0009] Furthermore, the maximum depth of the groove is h b , where h n It is the tooth height of standard metric internal thread or MJ internal thread.

[0010] To achieve the above purpose, the combined nut for stud bolts in the present invention adopts the following technical solution:

[0011] A combination nut for stud bolts, comprising a protection nut for pre-embedded in a structure and a breaking nut for connecting with one end of the stud bolt extending outside the structure, the internal threads of the protection nut and the breaking nut are both improved metric threads or MJ threads and the pitch is P, the internal thread bottoms of the protection nut and the breaking nut are respectively provided with continuous grooves, and the internal thread tooth profiles include sequentially connected tooth tops, tooth side straight line segments, groove side straight line segments corresponding to one side groove wall of the groove, groove bottom segments corresponding to the groove bottom of the groove, groove side straight line segments corresponding to the other side groove wall of the groove, and tooth side straight line segments, and the maximum width of the groove at the internal thread bottom of the protection nut is g b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b ·h b .

[0012] The beneficial effect of the above technical solution is that: the present invention is a pioneering invention, and the proposed combination nut for stud bolts includes a protective nut and a breaking nut. The protective nut is pre-buried in the structure, and the breaking nut is connected to the end of the stud bolt extending outside the structure. Measures are set to ensure that the end of the stud bolt assembly that cooperates with the protective nut will not break when subjected to alternating loads, while the end that cooperates with the breaking nut will break. Specifically, the internal threads of the protective nut and the breaking nut are both improved metric threads or MJ threads, and the pitch is P. The internal thread bottoms of the protective nut and the breaking nut are respectively provided with continuous grooves, and the internal thread tooth profiles include sequentially connected tooth tops, tooth side straight line segments, groove side straight line segments corresponding to one side groove wall of the groove, groove bottom segments corresponding to the groove bottom of the groove, groove side straight line segments corresponding to the other side groove wall of the groove, and tooth side straight line segments. The maximum width of the groove at the internal thread bottom of the protective nut is g. b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b ·h b .

[0013] Among them, g d and g b Both greater than It is the root width of the standard metric internal thread or MJ internal thread, which means that the groove sidewall has been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread tooth, thus reducing the rigidity of the internal thread tooth. d and g b All less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0014] In summary, in the present invention, the tooth thickness of the internal thread teeth of the protection nut and the broken nut are reduced, the rigidity of the internal thread teeth can be reduced, and at the same time g d ·h d <g b ·h bTherefore, the stiffness of the internal thread teeth of the protective nut will be reduced more, the stiffness of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread teeth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, which makes it easier to remove the stud bolt from the structure and facilitate on-site replacement operations.

[0015] Further, where h n It is the tooth height of standard metric internal thread or MJ internal thread.

[0016] To achieve the above purpose, the stud bolt assembly in the present invention adopts the following technical solution:

[0017] A stud bolt assembly comprises a stud bolt and a combination nut used in conjunction with the stud bolt, wherein the external threads at both ends of the stud bolt are standard metric threads or MJ threads and the design parameters of the external threads at both ends are the same, the combination nut comprises a protective nut used for pre-embedded in a structure and a breaking nut used for connecting with one end of the stud bolt extending outside the structure, the internal thread of the breaking nut is a standard metric thread or MJ thread, the pitch of the protective nut is P, the internal thread of the protective nut is an improved metric thread or MJ thread, a continuous groove is provided at the bottom of the internal thread of the protective nut, and the internal thread tooth profile comprises a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to a groove wall on one side of the groove, a groove bottom segment corresponding to a groove bottom of the groove, a groove side straight line segment corresponding to a groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and the maximum width of the groove is g b ,

[0018] The beneficial effect of the above technical solution is that: the present invention belongs to an improved invention, further limiting that the external threads at both ends of the stud bolt are standard metric threads or MJ threads and the design parameters of the external threads at both ends are the same, and the combined nut includes a protective nut and a breaking nut, the protective nut is pre-buried in the structure, and the breaking nut is connected to the end of the stud bolt extending outside the structure, and measures are set to ensure that the end of the stud bolt assembly that cooperates with the protective nut will not break when subjected to alternating loads, while the end that cooperates with the breaking nut will break. Specifically, the internal thread of the breaking nut is a standard metric thread or MJ thread, and the internal thread of the protective nut is an improved metric thread or MJ thread. The improvement is that the internal thread bottom of the protective nut is provided with a continuous groove and the internal thread tooth profile includes a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to a groove wall on one side of the groove, a groove bottom segment corresponding to the groove bottom of the groove, a groove side straight line segment corresponding to the groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and the maximum width of the groove is g. b , in, It is the root width of the standard metric internal thread or MJ internal thread, which means that the groove sidewall has been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread tooth, thus reducing the rigidity of the internal thread tooth. b Less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0019] In summary, in the present invention, the tooth thickness of the internal thread teeth of the protective nut is reduced, the rigidity of the internal thread teeth of the protective nut can be reduced, and the broken nut does not change, so the rigidity of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread tooth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, and the stud bolt can be conveniently removed from the structure, thereby facilitating on-site replacement operations.

[0020] Furthermore, the maximum depth of the groove is h b , where h n It is the tooth height of standard metric internal thread or MJ internal thread.

[0021] To achieve the above purpose, the stud bolt assembly in the present invention adopts the following technical solution:

[0022] A stud bolt assembly comprises a stud bolt and a combination nut used in conjunction with the stud bolt, wherein the external threads at both ends of the stud bolt are standard metric threads or MJ threads and the design parameters of the external threads at both ends are the same, the combination nut comprises a protection nut used for pre-embedded in a structure and a breaking nut used for connecting with one end of the stud bolt extending outside the structure, the internal threads of the protection nut and the breaking nut are improved metric threads or MJ threads and the pitch is P, the internal thread bottoms of the protection nut and the breaking nut are respectively provided with continuous grooves and the internal thread tooth profiles include a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to a groove wall on one side of the groove, a groove bottom segment corresponding to a groove bottom of the groove, a groove side straight line segment corresponding to a groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and the maximum width of the groove at the internal thread bottom of the protection nut is g b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b ·h b .

[0023] The beneficial effect of the above technical solution is that: the present invention belongs to an improved invention, which further defines that the external threads at both ends of the stud bolt are standard metric threads or MJ threads and the design parameters of the external threads at both ends are the same, and the combined nut includes a protective nut and a breaking nut, the protective nut is pre-buried in the structure, and the breaking nut is connected to the end of the stud bolt extending outside the structure, and measures are set to ensure that the end of the stud bolt assembly that cooperates with the protective nut will not break when subjected to alternating loads, while the end that cooperates with the breaking nut will break. Specifically, the internal threads of the protective nut and the breaking nut are both improved metric threads or MJ threads and the pitch is P, the internal thread bottoms of the protective nut and the breaking nut are respectively provided with continuous grooves, and the internal thread tooth profiles include the tooth top, tooth side straight line segment, groove side straight line segment corresponding to the groove wall on one side of the groove, groove bottom segment corresponding to the groove bottom of the groove, groove side straight line segment corresponding to the groove wall on the other side of the groove, and tooth side straight line segment connected in sequence, and the maximum width of the groove at the internal thread bottom of the protective nut is g b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b·h b .

[0024] Among them, g d and g b Both greater than It is the root width of the standard metric internal thread or MJ internal thread, which means that the groove sidewall has been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread tooth, thus reducing the rigidity of the internal thread tooth. d and g b All less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0025] In summary, in the present invention, the tooth thickness of the internal thread teeth of the protection nut and the broken nut are reduced, the rigidity of the internal thread teeth can be reduced, and at the same time g d ·h d <g b ·h b Therefore, the stiffness of the internal thread teeth of the protective nut will be reduced more, the stiffness of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread teeth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, which makes it easier to remove the stud bolt from the structure and facilitate on-site replacement operations.

[0026] Further, where h n It is the tooth height of standard metric internal thread or MJ internal thread. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of embodiment 1 of the stud bolt assembly of the present invention;

[0028] Figure 2 It is the standard metric thread profile diagram in the prior art;

[0029] Figure 3 The internal thread profile diagram of the protection nut and the broken nut in Embodiment 1 of the stud bolt assembly of the present invention;

[0030] Figure 4 It is a calibration position diagram of the stud bolt in Embodiment 1 of the stud bolt assembly of the present invention;

[0031] Figure 5It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 1 and the comparison bolt under the same alternating load over time in Example 1 of the stud bolt assembly of the present invention;

[0032] Figure 6 It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 2 and the comparison bolt under the same alternating load over time in Example 1 of the stud bolt assembly of the present invention;

[0033] Figure 7 It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 3 and the comparison bolt under the same alternating load over time in Example 1 of the stud bolt assembly of the present invention;

[0034] Figure 8 It is the standard MJ thread profile diagram in the prior art;

[0035] Fig. 9 The internal thread profile diagram of the protection nut and the broken nut in Embodiment 5 of the stud bolt assembly of the present invention;

[0036] Fig.10 It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 4 and the comparison bolt under the same alternating load over time in Example 5 of the stud bolt assembly of the present invention;

[0037] Fig.11 It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 5 and the comparison bolt under the same alternating load over time in Example 5 of the stud bolt assembly of the present invention;

[0038] Fig.12 It is a curve diagram showing the change of the average stress at the calibrated position of the stud bolt 6 and the comparison bolt under the same alternating load over time in Example 5 of the stud bolt assembly of the present invention;

[0039] Fig.13 This is the internal thread profile diagram of the stud bolt assembly embodiment 9 of the present invention. DETAILED DESCRIPTION

[0040] In view of the technical problems existing in the prior art, the basic inventive concept of the present invention is to divide the combination nut used in conjunction with the stud bolt into a protective nut pre-buried in the structure and a breaking nut connected to the end of the stud bolt extending outside the structure, and to design the internal thread parameters of the protective nut and the breaking nut to ensure that the internal thread teeth of the protective nut have smaller stiffness, so that when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby improving the fatigue performance of the external thread of the stud bolt at the protective nut, and making the probability of the stud bolt breaking at the breaking nut greater.

[0041] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0042] Embodiment 1 of the stud bolt assembly of the present invention:

[0043] like Figure 1 As shown, the stud bolt assembly includes a stud bolt 1 and a combination nut used in conjunction with the stud bolt 1, the combination nut includes a protection nut 2 for being embedded in the structure and a breaking nut 3 for being connected to one end of the stud bolt 1 extending out of the structure, the structure may be the root of a wind turbine blade or a concrete foundation under a wind turbine tower. The external threads at both ends of the stud bolt 1 include a protection end external thread 11 for being connected in conjunction with the protection nut 2 and a breaking end external thread 12 for being connected in conjunction with the breaking nut 3.

[0044] In this embodiment, the external thread 11 of the protection end and the external thread 12 of the breaking end are both standard metric threads, and the design parameters of the external threads at both ends are the same. The internal threads of the protection nut 2 and the breaking nut 3 are both improved metric threads, and the internal thread profiles are evolved from the standard metric thread profiles, so the standard metric thread profiles are first introduced below.

[0045] like Figure 2 As shown in the figure, D is the major diameter of the internal thread, d is the major diameter of the external thread, D2 is the middle diameter of the internal thread, d2 is the middle diameter of the external thread, D1 is the minor diameter of the internal thread, d1 is the minor diameter of the external thread, P is the pitch, and H is the height of the original triangle. The crest width of the internal thread is The tooth bottom width is The crest width of the external thread is The tooth bottom width is Since the tooth angle of the internal and external threads is 60°, the tooth height of the internal and external threads can be obtained through geometric calculation. (Right now Figure 2 In ).

[0046] In this embodiment, the internal thread profiles of the protection nut and the broken nut are the same, such as Figure 3 As shown in the figure, the tooth angle α of the internal thread of the protection nut and the broken nut is 60°, the pitch is P, the minor diameter is D1, and the crest width is The standard metric internal thread height is The major diameter is D, the middle diameter is D2, and the tooth bottom width is

[0047] The root of the internal thread of the protection nut and the breaking nut is provided with a continuous groove, so that the tooth profile of the internal thread includes a tooth top 41, a tooth side straight line segment 42, a groove side straight line segment 43 corresponding to one of the groove side walls of the groove, a groove bottom segment 44 corresponding to the groove bottom wall of the groove, a groove side straight line segment 43 corresponding to the other groove side wall of the groove, and a tooth side straight line segment 42, which are connected in sequence, wherein the groove bottom segment 44 is arc-shaped, the two tooth side straight line segments 42 are symmetrical and equal in length, and the angle between the two tooth side straight line segments 42 is the tooth profile angle α. In this embodiment, the two groove side straight line segments 43 are equal in length and are both perpendicular to the axis of the internal thread, and the spacing between the two groove side straight line segments 43 is the groove width of the groove (also the maximum width of the groove), the groove width is g, and the maximum depth is h.

[0048] For easy distinction, the width of the groove at the bottom of the internal thread of the protective nut is defined as g. b , the maximum depth is h b The width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , then g d and g b The range is The slot width g d and g b Both greater than It is the standard metric internal thread root width, which means that the groove sidewalls have been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread teeth, thus reducing the rigidity of the internal thread teeth. d and g b All less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0049] Therefore, the tooth thickness of the internal thread teeth of the protection nut and the broken nut in the present invention is reduced, the rigidity of the internal thread teeth can be reduced, and at the same time g d ·h d <g b ·h b Therefore, the stiffness of the internal thread teeth of the protective nut will be reduced more, the stiffness of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread teeth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, which makes it easier to remove the stud bolt from the structure and facilitate on-site replacement operations.

[0050] Further, because so From the geometric relationship, we know that when When the inner diameter of the deepest groove is just the major diameter D of the standard metric internal thread, the embodiment defines This indicates that the maximum depth of the groove at the bottom of the internal thread of the protective nut has exceeded the major diameter D of the standard metric internal thread, so the actual thread height of the internal thread of the protective nut will be greater than the thread height of the standard metric internal thread, which increases the thread height of the internal thread of the protective nut, further reduces the rigidity of the internal thread of the protective nut, and improves the bending deflection of the internal thread of the protective nut. At the same time, the present invention also defines The tooth height of the entire protective nut internal thread cannot be increased to more than twice the original height to ensure the safe use of the protective nut internal thread.

[0051] at the same time, because so From the geometric relationship, we can know that when When the inner diameter of the deepest groove is just the major diameter D of the standard metric internal thread, the embodiment defines This indicates that the maximum depth of the groove at the bottom of the internal thread of the broken nut has exceeded the major diameter D of the standard metric internal thread, so the actual tooth height of the internal thread of the broken nut will be greater than the tooth height of the standard metric internal thread, which increases the tooth height of the internal thread of the broken nut, further reducing the rigidity of the internal thread of the broken nut and increasing the bending deflection of the internal thread of the broken nut. At the same time, the present invention also defines The tooth height of the entire broken nut internal thread cannot be increased to more than twice the original, ensuring the safety of the broken nut internal thread. d ·h d <g b ·h b , which can ensure that the internal thread tooth stiffness of the protective nut is lower, and ensure that the probability of the fracture position occurring at the broken nut is higher.

[0052] Three groups of comparative tests are provided below. In the first group of comparative tests: the external threads at the protective ends and the external threads at the broken ends of the stud bolt 1 and the comparative bolt are both standard metric threads (for ease of description, the present invention also divides the two ends of the comparative bolt into broken ends and protective ends), the internal threads of the nuts used at both ends of the comparative bolt are both standard metric threads, the nuts used at both ends of the stud bolt 1 are the protective nuts and broken nuts in this embodiment, and the internal threads of the protective nuts and broken nuts are both improved metric threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 1 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external threads and internal threads is 4mm. By calculation, it can be obtained that

[0053] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =0.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0054] Width of groove g at the bottom of the internal thread of the protective nut b =1.5mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b >g d At the same time, we can calculate so And h b >h d , so g d ·h d <g b ·h b .

[0055] The general finite element analysis software is used to perform dynamic analysis on the internal and external threads. That is, a fixed constraint is imposed on the nut, and an alternating load that changes with time is imposed on the bolt. Under the same alternating load, the stud bolt 1 and the comparison bolt are at the calibrated position (the stud bolt 1 and the comparison bolt have calibrated positions at the fracture end and the protection end, and the calibrated position is Figure 4 The red dot in the figure is the first thread position where the bolt's external thread and the nut fit together, which is usually also the position where the stress is most concentrated. The average stress changes with time curve at the red dot in the figure.

[0056] like Figure 5 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 1 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 1 is better. At the same time, since the average stress at the fracture end of the stud bolt 1 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 1 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks first at the fracture end.

[0057] In the second group of comparative tests: the external threads at the protection end and the fracture end of the stud bolt 2 and the comparative bolt are both standard metric threads, the internal threads of the nuts used at both ends of the comparative bolt are both standard metric threads, the nuts used at both ends of the stud bolt 2 are the protection nuts and fracture nuts in this embodiment, and the internal threads of the protection nuts and fracture nuts are both improved metric threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 2 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external and internal threads is 4mm. By calculation, it can be obtained that

[0058] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =0.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0059] Width of groove g at the bottom of the internal thread of the protective nut b =1mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b =g d At the same time, we can calculate so And h b >h d , so g d ·h d <g b ·h b .

[0060] Similarly, the general finite element analysis software is used to perform dynamic analysis on the internal and external threads, and the average stress variation curves of the stud bolt 2 and the comparison bolt at the calibrated position under the same alternating load are obtained. Figure 6 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 2 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 2 is better. At the same time, since the average stress at the fracture end of the stud bolt 2 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 2 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks first at the fracture end.

[0061] In the third group of comparative tests: the external threads at the protection end and the fracture end of the stud bolt 3 and the comparative bolt are both standard metric threads, the internal threads of the nuts used at both ends of the comparative bolt are both standard metric threads, the nuts used at both ends of the stud bolt 3 are the protective nuts and fracture nuts in this embodiment, and the internal threads of the protective nuts and fracture nuts are both improved metric threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 3 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external and internal threads is 4mm. By calculation, it can be obtained that

[0062] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =1.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0063] Width of groove g at the bottom of the inner thread of the protective nut b =1.5mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b >g d At the same time, we can calculate so And h b =h d , so g d ·h d <g b ·h b .

[0064] Similarly, the general finite element analysis software is used to perform dynamic analysis on the internal and external threads, and the average stress variation curves of the stud bolt 3 and the comparison bolt at the calibrated position under the same alternating load are obtained. Figure 7 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 3 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 3 is better. At the same time, since the average stress at the fracture end of the stud bolt 3 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 3 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks preferentially at the fracture end.

[0065] In addition, from Figure 5 , Figure 6 and Figure 7 It can also be seen that the average stress at the guard end of stud 1 and stud 3 is equal and the smallest, because the g of the guard nut used with stud 1 is b ·h b g of the protective nut used with the stud bolt 3 b ·h b is equal to and greater than the g of the protective nut used with the stud bolt 2 b ·h b , of course, it is greater than the g of the broken nut used with stud bolts 1, 2 and 3. d ·h d , so it is verified that g d ·h d <g b ·h b It can not only reduce the average stress at the stud bolt protection end, but also b ·h b The larger it is, the more the mean stress is reduced.

[0066] Embodiment 2 of the stud bolt assembly of the present invention:

[0067] The difference between this embodiment and embodiment 1 is that the internal thread of the broken nut in embodiment 2 is a standard metric thread, that is, the internal thread root of the broken nut is no longer provided with a groove, and only the internal thread of the protection nut is an improved metric thread, the internal thread root of the protection nut is provided with a continuous groove, and the internal thread tooth profile includes a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to the groove wall on one side of the groove, a groove bottom segment corresponding to the groove bottom of the groove, a groove side straight line segment corresponding to the groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and both groove side straight lines are perpendicular to the internal thread axis. The internal thread of the protection nut is the same as that of embodiment 1, with the same pitch of P and the groove width of the groove at the internal thread root of g. b , The maximum depth of the groove protecting the bottom of the internal thread of the nut is h b ,

[0068] It can be seen from the results of the three groups of comparative tests in Example 1 that as long as the root of the internal thread of the protective nut and the broken nut is provided with grooves, the average stress at the broken end and the protective end of the stud bolt will be reduced, and will be less than the average stress at both ends of the comparison bolt (the internal threads of the matching nuts at both ends are standard metric threads, that is, the root of the internal threads of the nuts at both ends are not provided with grooves). Therefore, specifically in this embodiment, the root of the internal thread of the broken nut is not provided with grooves, and the root of the internal thread of the protective nut is provided with grooves, so the average stress at the protective end of the stud bolt will inevitably be less than the average stress at the broken end, and the fatigue performance of the protective end is better than that of the broken end. When fatigue fracture occurs, the bolt breaks preferentially at the broken end.

[0069] Embodiment 3 of the stud bolt assembly of the present invention:

[0070] The difference between this embodiment and embodiment 2 is that in embodiment 3 At this time, the inner diameter of the deepest part of the groove is just the large diameter of the standard metric internal thread, and the tooth height of the internal thread of the protective nut is the same as the tooth height of the standard metric internal thread. At this time due to It is equivalent to only reducing the tooth thickness of the internal thread teeth, which can also reduce the rigidity of the internal thread teeth and increase the bending deflection of the internal thread teeth, so that the internal thread teeth can undergo greater bending deformation to absorb the inertia force generated by the alternating load, thereby reducing the stress of the external thread tooth bottom under the action of the alternating load and improving the fatigue performance of the external thread.

[0071] Embodiment 4 of the stud bolt assembly of the present invention:

[0072] The difference between this embodiment and embodiment 1 is that in embodiment 4 The inner diameter at the deepest part of the groove is the large diameter of the standard metric internal thread. The tooth height of the internal thread of the protection nut and the breaking nut is the same as the tooth height of the standard metric internal thread. At this time due to Both the protective nut and the broken nut only reduce the tooth thickness of the internal thread teeth, and the rigidity of the internal thread teeth can be reduced. d ·h d <g b ·h b , which makes the internal thread tooth stiffness of the protective nut reduce more, ensuring that the probability of the fracture position occurring at the broken nut is higher.

[0073] Embodiment 5 of the stud bolt assembly of the present invention:

[0074] The stud bolt assembly in this embodiment also includes a stud bolt and a combination nut used in conjunction with the stud bolt, the combination nut includes a protection nut used to be embedded in the structure and a breaking nut used to be connected to one end of the stud bolt extending outside the structure, the structure may be the root of a wind turbine blade or a concrete foundation under a wind turbine tower. The external threads at both ends of the stud bolt include a protection end external thread connected in conjunction with the protection nut and a breaking end external thread connected in conjunction with the breaking nut.

[0075] In this embodiment, the external threads of the protection end and the fracture end are both standard MJ threads, and the design parameters of the external threads at both ends are the same. The internal threads of the protection nut and the fracture nut are both improved MJ threads, and the internal thread profiles are evolved from the standard MJ thread profiles, so the standard MJ thread profiles are first introduced below.

[0076] like Figure 8 As shown in the figure, D is the major diameter of the internal thread, d is the major diameter of the external thread, D2 is the middle diameter of the internal thread, d2 is the middle diameter of the external thread, D1 is the minor diameter of the internal thread, d1 is the minor diameter of the external thread, P is the pitch, and H is the height of the original triangle. Unlike metric threads, the crest width of MJ internal threads is The tooth bottom width is The crest width of the MJ external thread is The tooth bottom width is Since the tooth angles of the MJ internal and external threads are both 60°, the tooth heights of the MJ internal and external threads can be obtained through geometric calculations as follows: (Right now Figure 8 In ).

[0077] In this embodiment, the internal thread profiles of the protection nut and the broken nut are the same, such as Fig. 9 As shown in the figure, the tooth angle α of the internal thread of the protection nut and the broken nut is 60°, the pitch is P, the minor diameter is D1, and the crest width is The standard MJ internal thread height is The major diameter is D, the middle diameter is D2, and the tooth bottom width is

[0078] The bottom of the internal thread of the protection nut and the breaking nut is provided with a continuous groove, so that the tooth profile of the internal thread includes a tooth top 41, a tooth side straight line segment 42, a groove side straight line segment 43 corresponding to one of the groove side walls of the groove, a groove bottom segment 44 corresponding to the groove bottom wall of the groove, a groove side straight line segment 43 corresponding to the other groove side wall of the groove, and a tooth side straight line segment 42, which are connected in sequence, wherein the groove bottom segment 44 is arc-shaped, the two tooth side straight line segments 42 are symmetrical and equal in length, and the angle between the two tooth side straight line segments 42 is the tooth profile angle α. In this embodiment, the two groove side straight line segments 43 are equal in length and are both perpendicular to the axis of the internal thread, and the spacing between the two groove side straight line segments 43 is the groove width of the groove (that is, the maximum width of the groove), the groove width is g, and the maximum depth is h.

[0079] For easy distinction, the width of the groove at the bottom of the internal thread of the protective nut is defined as g. b , the maximum depth is h b The width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , then g d and g b The range is The slot width g d and g b Both greater than is the standard MJ internal thread root width, which means that the groove sidewalls have been processed to the tooth side, which is equivalent to reducing the tooth thickness of the internal thread teeth, thus reducing the rigidity of the internal thread teeth. d and g b All less than Avoid the groove being too wide to affect the basic tooth thickness of the internal thread teeth, ensuring safety in use.

[0080] Therefore, the tooth thickness of the internal thread teeth of the protection nut and the broken nut in the present invention is reduced, the rigidity of the internal thread teeth can be reduced, and at the same time g d ·h d <g b ·h b Therefore, the stiffness of the internal thread teeth of the protective nut will be reduced more, the stiffness of the internal thread teeth of the protective nut is less than that of the internal thread teeth of the broken nut, and the bending deflection of the internal thread teeth of the protective nut is larger. Therefore, when the stud bolt assembly is subjected to alternating loads, the internal thread teeth of the protective nut can undergo greater bending deformation to absorb the inertia force generated by the alternating loads, thereby reducing the stress of the external thread teeth bottom of the stud bolt at the protective nut, and improving the fatigue performance of the external thread of the stud bolt at the protective nut. Therefore, when the stud bolt undergoes fatigue fracture, the probability of the fracture occurring at the broken nut is higher, which makes it easier to remove the stud bolt from the structure and facilitate on-site replacement operations.

[0081] Further, because so From the geometric relationship, we know that when When the inner diameter of the deepest groove is just the major diameter D of the standard MJ internal thread, the embodiment defines This indicates that the maximum depth of the groove at the bottom of the internal thread of the protective nut has exceeded the major diameter D of the standard MJ internal thread, so the actual tooth height of the internal thread of the protective nut will be greater than the tooth height of the standard MJ internal thread, which increases the tooth height of the internal thread of the protective nut, further reduces the rigidity of the internal thread of the protective nut, and improves the bending deflection of the internal thread of the protective nut. At the same time, the present invention also defines The tooth height of the entire protective nut internal thread cannot be increased to more than twice the original height to ensure the safe use of the protective nut internal thread.

[0082] at the same time, because so From the geometric relationship, we can know that when When the inner diameter of the deepest groove is just the major diameter D of the standard MJ internal thread, the embodiment defines This indicates that the maximum depth of the groove at the bottom of the internal thread of the broken nut has exceeded the major diameter D of the standard MJ internal thread, so the actual tooth height of the internal thread of the broken nut will be greater than the tooth height of the standard MJ internal thread, which increases the tooth height of the internal thread of the broken nut, further reduces the rigidity of the internal thread of the broken nut, and increases the bending deflection of the internal thread of the broken nut. At the same time, the present invention also defines The tooth height of the entire broken nut internal thread cannot be increased to more than twice the original, ensuring the safety of the broken nut internal thread. d ·h d <g b ·h b , which can ensure that the internal thread tooth stiffness of the protective nut is lower, and ensure that the probability of the fracture position occurring at the broken nut is higher.

[0083] Three more groups of comparative tests are provided below. In the fourth group of comparative tests: the external threads at the protective ends and the external threads at the broken ends of the stud bolt 4 and the comparative bolt are both standard MJ threads (for ease of description, the present invention also divides the two ends of the comparative bolt into broken ends and protective ends), the internal threads of the nuts used at both ends of the comparative bolt are both standard MJ threads, the nuts used at both ends of the stud bolt 4 are the protective nuts and broken nuts in this embodiment, and the internal threads of the protective nuts and broken nuts are both improved MJ threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 4 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external threads and internal threads is 4mm. By calculation, it can be obtained that

[0084] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =0.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0085] Width of groove g at the bottom of the internal thread of the protective nut b =1.5mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b >g d At the same time, we can calculate so And h b >h d , so g d ·hd <g b ·h b .

[0086] The dynamic analysis of the internal and external threads was performed using general finite element analysis software, that is, a fixed constraint was imposed on the nut, and an alternating load that varied with time was imposed on the bolt, and the average stress variation curves of the stud bolt 4 and the comparison bolt at the calibrated position (the calibrated position is the same as that in Example 1) under the same alternating load were obtained. Fig.10 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 4 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 4 is better. At the same time, since the average stress at the fracture end of the stud bolt 4 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 4 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks preferentially at the fracture end.

[0087] In the fifth group of comparative tests: the external threads at the protection end and the fracture end of the stud bolt 5 and the comparative bolt are both standard MJ threads, the internal threads of the nuts used at both ends of the comparative bolt are both standard MJ threads, the nuts used at both ends of the stud bolt 5 are the protective nuts and fracture nuts in this embodiment, and the internal threads of the protective nuts and fracture nuts are both improved MJ threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 5 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external threads and internal threads is 4mm. By calculation, it can be obtained that

[0088] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =0.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0089] Width of groove g at the bottom of the internal thread of the protective nut b =1mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b =g d At the same time, we can calculate so And h b >h d , so g d ·hd <g b ·h b .

[0090] Similarly, the general finite element analysis software is used to perform dynamic analysis on the internal and external threads, and the average stress variation curves of the stud bolt 5 and the comparison bolt at the calibrated position under the same alternating load are obtained. Fig.11 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 5 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 5 is better. At the same time, since the average stress at the fracture end of the stud bolt 5 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 5 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks preferentially at the fracture end.

[0091] In the sixth group of comparative tests: the external threads at the protection end and the fracture end of the stud bolt 6 and the comparative bolt are both standard MJ threads, the internal threads of the nuts used at both ends of the comparative bolt are both standard MJ threads, the nuts used at both ends of the stud bolt 6 are the protection nuts and fracture nuts in this embodiment, and the internal threads of the protection nuts and fracture nuts are both improved MJ threads. The major diameter of the external threads at both ends of the comparative bolt and the stud bolt 6 is 36mm, the major diameter of the internal threads of the nuts used with the comparative bolt is 36mm, and the pitch P of all external and internal threads is 4mm. By calculation, it can be obtained that

[0092] Among them, the groove width g of the bottom of the internal thread of the broken nut d =1mm, maximum depth h d =1.5mm, slot width g d exist In the range, it can be calculated so The tooth thickness of the internal thread of the broken nut is reduced, while the tooth height of the internal thread is increased.

[0093] Width of groove g at the bottom of the inner thread of the protective nut b =1.5mm, maximum depth h b =1.5mm, slot width g b exist Within the range, and g b >g d At the same time, we can calculate so And h b =h d , so g d ·h d <g b ·hb .

[0094] Similarly, the dynamic analysis of the internal and external threads was performed using general finite element analysis software to obtain the average stress variation curves of the stud bolt 6 and the comparison bolt at the calibrated position under the same alternating load. Fig.12 As shown, the average stress at the calibrated position at both ends of the comparison bolt is equal at each moment, and the average stress at the fracture end and the protection end of the stud bolt 6 is less than the average stress at both ends of the comparison bolt, which shows that the fatigue performance of the stud bolt 6 is better. At the same time, since the average stress at the fracture end of the stud bolt 6 is greater than the average stress at the protection end, that is, the fatigue performance of the protection end of the stud bolt 6 is better than that of the fracture end, when fatigue fracture occurs, the bolt breaks preferentially at the fracture end.

[0095] In addition, from Fig.10 , Fig.11 and Fig.12 It can also be seen that the average stress at the guard end of stud bolt 4 and stud bolt 6 is equal and the smallest, because the g of the guard nut used with stud bolt 4 is b ·h b g of the protective nut used with the stud bolt 6 b ·h b is equal to and greater than the g of the protective nut used with the stud bolt 5 b ·h b , of course, greater than the g of the broken nut used with stud bolts 4, 5 and 6. d ·h d , so it is verified that g d ·h d <g b ·h b It can not only reduce the average stress at the stud bolt protection end, but also b ·h b The larger it is, the more the mean stress is reduced.

[0096] Embodiment 6 of the stud bolt assembly of the present invention:

[0097] The only difference between this embodiment and embodiment 5 is that the internal thread of the broken nut in embodiment 6 is a standard MJ thread, that is, the internal thread root of the broken nut is no longer provided with a groove, and only the internal thread of the protection nut is an improved MJ thread, the internal thread root of the protection nut is provided with a continuous groove and the internal thread tooth profile includes a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to the groove wall on one side of the groove, a groove bottom segment corresponding to the groove bottom of the groove, a groove side straight line segment corresponding to the groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence, and both groove side straight lines are perpendicular to the internal thread axis. The internal thread of the protection nut is the same as that of embodiment 5, with the same pitch of P and the groove width of the groove at the internal thread root of g. b , The maximum depth of the groove protecting the bottom of the internal thread of the nut is h b ,

[0098] It can be seen from the results of the three groups of comparative tests in Example 5 that as long as the root of the internal thread of the protective nut and the broken nut is provided with grooves, the average stress of the broken end and the protective end of the stud bolt will be reduced, and will be less than the average stress at both ends of the comparison bolt (the internal threads of the matching nuts at both ends are standard MJ threads, that is, the internal thread roots of the nuts at both ends are not provided with grooves). Therefore, specifically in this embodiment, the root of the internal thread of the broken nut is not provided with grooves, and the root of the internal thread of the protective nut is provided with grooves, so the average stress of the protective end of the stud bolt will inevitably be less than the average stress of the broken end, and the fatigue performance of the protective end is better than that of the broken end. When fatigue fracture occurs, the bolt breaks preferentially at the broken end.

[0099] Embodiment 7 of the stud bolt assembly of the present invention:

[0100] The difference between this embodiment and embodiment 6 is that in embodiment 7 At this time, the inner diameter of the deepest part of the groove is just the large diameter of the standard MJ internal thread, and the tooth height of the internal thread of the protective nut is the same as the tooth height of the standard MJ internal thread. At this time due to It is equivalent to only reducing the tooth thickness of the internal thread teeth, which can also reduce the rigidity of the internal thread teeth and increase the bending deflection of the internal thread teeth, so that the internal thread teeth can undergo greater bending deformation to absorb the inertia force generated by the alternating load, thereby reducing the stress of the external thread tooth bottom under the action of the alternating load and improving the fatigue performance of the external thread.

[0101] Embodiment 8 of the stud bolt assembly of the present invention:

[0102] The difference between this embodiment and embodiment 5 is that in embodiment 8 The inner diameter at the deepest part of the groove is the large diameter of the standard MJ internal thread. The tooth height of the internal thread of the protection nut and the breaking nut is the same as the tooth height of the standard MJ internal thread. At this time due to Both the protective nut and the broken nut only reduce the tooth thickness of the internal thread teeth, and the rigidity of the internal thread teeth can be reduced. d ·h d <g b ·h b , which makes the internal thread tooth stiffness of the protective nut reduce more, ensuring that the probability of the fracture position occurring at the broken nut is higher.

[0103] Embodiment 9 of the stud bolt assembly of the present invention: Fig.13 As shown, this embodiment is different from any of the above embodiments in that, on the nut with a groove at the bottom of the internal thread, the two groove side straight sections 43 of the groove are not perpendicular to the axis of the internal thread, and the two groove side straight sections 43 are still symmetrical but have a certain angle between them, which is smaller than the tooth angle. At this time, the maximum depth of the groove is h, the maximum width is g, and the maximum width position is the position where the groove side straight section 43 intersects with the tooth side straight section 42.

[0104] In other embodiments of the stud bolt assembly of the present invention: Different from any of the above embodiments, on the nut with a groove at the bottom of the internal thread, the bottom section of the groove can be a straight line section, and the groove depth at each location of the groove is the same.

[0105] The embodiment of the combination nut for stud bolts in the present invention is as follows: the specific structure of the combination nut for stud bolts is the same as the combination nut in any embodiment of the stud bolt assembly described above, and will not be repeated here.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A combination nut for a stud bolt, characterized in that: The invention comprises a protective nut for being embedded in a structure and a breaking nut for being connected with one end of a stud bolt extending out of the structure. The internal thread of the breaking nut is a standard metric thread or an MJ thread. The internal thread of the protective nut is an improved metric thread or an MJ thread. The pitch of the protective nut is P. The internal thread bottom of the protective nut is provided with a continuous groove. The internal thread tooth profile line comprises a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to a groove wall on one side of the groove, a groove bottom segment corresponding to a groove bottom of the groove, a groove side straight line segment corresponding to a groove wall on the other side of the groove, and a tooth side straight line segment connected in sequence. The maximum width of the groove is g. b , 2. The combination nut for stud bolts according to claim 1, characterized in that: The maximum depth of the groove is h b , where h n It is the tooth height of standard metric internal thread or MJ internal thread.

3. A combination nut for a stud bolt, characterized in that: It includes a protective nut for pre-embedded in the structure and a breaking nut for connecting with one end of the stud bolt extending outside the structure. The internal threads of the protective nut and the breaking nut are improved metric threads or MJ threads and the pitch is P. The internal thread bottoms of the protective nut and the breaking nut are respectively provided with continuous grooves, and the internal thread tooth profiles include sequentially connected tooth tops, tooth side straight lines, groove side straight lines corresponding to the groove wall on one side of the groove, groove bottom sections corresponding to the groove bottom of the groove, groove side straight lines corresponding to the groove wall on the other side of the groove, and tooth side straight lines. The maximum width of the groove at the internal thread bottom of the protective nut is g b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b ·h b .

4. The combination nut for stud bolts according to claim 3, characterized in that: where h n It is the tooth height of standard metric internal thread or MJ internal thread.

5. A stud bolt assembly, comprising a stud bolt and a combination nut used in conjunction with the stud bolt, characterized in that: The external threads at both ends of the stud bolt are standard metric threads or MJ threads, and the design parameters of the external threads at both ends are the same. The combination nut includes a protective nut for pre-embedded in the structure and a breaking nut for connecting with the end of the stud bolt extending outside the structure. The internal thread of the breaking nut is a standard metric thread or MJ thread. The pitch of the protective nut is P. The internal thread of the protective nut is an improved metric thread or MJ thread. The internal thread bottom of the protective nut is provided with a continuous groove, and the internal thread tooth profile includes a tooth top, a tooth side straight line segment, a groove side straight line segment corresponding to the groove wall on one side of the groove, a groove bottom segment corresponding to the groove bottom of the groove, a groove side straight line segment corresponding to the groove wall on the other side of the groove, and a tooth side straight line segment, and the maximum width of the groove is g b , 6. The stud bolt assembly according to claim 5, characterized in that: The maximum depth of the groove is h b , where h n It is the tooth height of standard metric internal thread or MJ internal thread.

7. A stud bolt assembly, comprising a stud bolt and a combination nut used in conjunction with the stud bolt, characterized in that: The external threads at both ends of the stud bolt are standard metric threads or MJ threads, and the design parameters of the external threads at both ends are the same. The combination nut includes a protective nut for pre-embedded in the structure and a breaking nut for connecting with the end of the stud bolt extending outside the structure. The internal threads of the protective nut and the breaking nut are improved metric threads or MJ threads, and the pitch is P. The internal thread bottoms of the protective nut and the breaking nut are respectively provided with continuous grooves, and the internal thread tooth profiles include sequentially connected tooth tops, tooth side straight line segments, groove side straight line segments corresponding to one side groove wall of the groove, groove bottom segments corresponding to the groove bottom of the groove, groove side straight line segments corresponding to the other side groove wall of the groove, and tooth side straight line segments. The maximum width of the groove at the internal thread bottom of the protective nut is g b , the maximum depth is h b The maximum width of the groove at the bottom of the internal thread of the broken nut is g. d , the maximum depth is h d , g d and g b The range is And g d ·h d <g b ·h b .

8. The stud bolt assembly according to claim 7, characterized in that: where h n It is the tooth height of standard metric internal thread or MJ internal thread.

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