A stress relief groove structure on the end face of a male thread and a drill rod

Abstract

The present invention belongs to the technical field of drilling equipment, and specifically discloses a male thread end face stress release groove structure and a drill rod, comprising: a first connecting rod, one end of which is connected to a drill bit; the first connecting rod has a through hole extending along its axial direction; the inner wall of the through hole is formed with a first conical surface, and the first conical surface corresponds to the other end of the first connecting rod; a second connecting rod, the end of which is provided with a second conical surface; the second conical surface is connected to the first conical surface by threads; along the radial direction of the through hole, a positioning surface connected to the circumferential direction of the second conical surface is formed on the second connecting rod; a stress groove is provided on the side of the positioning surface close to the second conical surface; the inner wall of the stress groove is used to connect the positioning surface and the second conical surface; it has the following advantages: the end face stress release groove and the square groove and shoulder structure optimize the stress distribution of the drill rod joint, enhance its resistance to extreme loads, and improve durability and safety. Filling the lubricant inside reduces friction, prevents adhesion, simplifies operation, and improves drilling efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of drilling equipment, and in particular to a stress release groove structure on an end face of a male thread and a drill rod. Background Art

[0002] In raise drilling operations, drill bit joints are prone to failure due to complex forces, especially in deep wells and high-intensity drilling. The current joint design uses a back-off process to form a stress relief groove to reduce stress concentration, but there are still shortcomings. The single shoulder structure is prone to failure under high torque. Although the double shoulder reduces stress concentration, it is easy to cause deformation of the contact surface when the torque is large, and it may be stuck when the buckle is removed. This leads to the limitations of the existing design under extreme conditions.

[0003] Therefore, a stress release groove structure of a male thread end face and a drill rod are proposed to solve the above-mentioned problems. Summary of the invention

[0004] The present invention aims to provide a pin thread end face stress relief groove structure and a drill rod to solve or improve at least one of the above-mentioned technical problems.

[0005] In view of this, a first aspect of the present invention is to provide a pin thread end surface stress relief groove structure and a drill rod.

[0006] A second aspect of the present invention is to provide a drill rod.

[0007] A first aspect of the present invention provides a male thread end face stress release groove structure and a drill rod, comprising: a first connecting rod, one end of which is connected to a drill bit; the first connecting rod has a through hole along its axial direction; the inner wall of the through hole is formed with a first tapered surface, the first tapered surface corresponds to the other end of the first connecting rod;

[0008] A second connecting rod, having a second conical surface at the end thereof; the second conical surface is connected to the first conical surface by a thread; a positioning surface connected to the circumferential direction of the second conical surface is formed on the second connecting rod along the radial direction of the through hole; a stress groove is formed on a side of the positioning surface close to the second conical surface; an inner wall of the stress groove is used to connect the positioning surface and the second conical surface to reduce the degree of transition of the stress streamline between the positioning surface and the second conical surface;

[0009] The stress groove corresponds to the larger diameter end of the second conical surface, and when the first conical surface transmits force to the second conical surface, the opening of the stress groove shrinks or expands.

[0010] In any of the above technical solutions, the opening direction of the stress groove is the same as the axial direction of the first connecting rod; when the second connecting rod abuts against the end face of the first connecting rod through the positioning surface, the end face of the first connecting rod covers the stress groove.

[0011] In any of the above technical solutions, the stress groove is located outside the through hole.

[0012] In any of the above technical solutions, a first tool retreat groove is formed at the large diameter end of the first tapered surface, and a second tool retreat groove is formed at the large diameter end of the second tapered surface;

[0013] When the positioning surface abuts against the end surface of the first connecting rod, the first tool relief groove corresponds to the second tapered surface along the radial direction of the first connecting rod, and / or the second tool relief groove is staggered with the second tapered surface along the radial direction of the first connecting rod.

[0014] In any of the above technical solutions, the stress groove is connected to the second tool-recessed groove;

[0015] When the positioning surface abuts against the end surface of the first connecting rod, the inner wall of the stress groove, the inner wall of the second tool relief groove and the surface of the first tapered surface form a deformation cavity.

[0016] In any of the above technical solutions, the stress groove is filled with lubricating liquid, and the deformation cavity is respectively connected to the abutment between the positioning surface and the end surface of the first connecting rod and the threaded connection between the second conical surface and the first conical surface.

[0017] In any of the above technical solutions, the stress groove is a circumferential ring; along the radial direction of the first connecting rod, the outer edge of the stress groove is provided with a rounded corner.

[0018] In any of the above technical solutions, a plurality of spaced-apart square grooves are provided on the side wall of the second connecting rod along the axial direction of the first connecting rod, and at least one shoulder is formed on the side wall of the second connecting rod;

[0019] Wherein, the positioning surface is located on the shoulder close to the second tapered surface.

[0020] In any of the above technical solutions, along the axial direction of the first connecting rod, the stress groove and the square groove are staggered.

[0021] A second aspect of the present invention provides a drill rod, comprising the stress relief groove structure on the end face of the male thread of any of the above technical solutions.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The stress relief groove on the end face effectively reduces the stress concentration at the threaded connection. By optimizing the stress path and distribution, the strength and stability of the connection are enhanced, the risk of fatigue damage under high load conditions is reduced, and the overall durability of the drill pipe is improved.

[0024] Through the end face stress relief groove and staggered square groove and shoulder structure, this design improves the performance of the drill pipe joint when facing extreme loads such as high torque and axial pressure. This ensures the reliability and safety of drilling operations under the most demanding conditions.

[0025] The lubricating fluid filled in the stress groove further optimizes the performance of the threaded connection, reduces the difficulty of operation, and prevents the adhesion between threads, ensuring smooth unloading of the rod. Quickly and easily connecting and disassembling the drill rod greatly improves the efficiency of the drilling operation.

[0026] Additional aspects and advantages of embodiments according to the present invention will become apparent in the following description or may be learned through practice of embodiments according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0028] Figure 1 It is a schematic diagram of assembling the first connecting rod and the second connecting rod of the present invention;

[0029] Figure 2 It is a schematic diagram of the second connecting rod structure of the present invention.

[0030] in, Figure 1-Figure 2 The corresponding relationship between the reference numerals and the component names is as follows:

[0031] 1 first connecting rod, 101 through hole, 102 first tapered surface, 103 first undercut groove, 2 second connecting rod, 201 stress groove, 202 second tapered surface, 203 second undercut groove, 204 square groove, 205 shoulder. DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0034] See also Figure 1-Figure 2 , the following describes a stress relief groove structure of a male thread end face and a drill rod according to some embodiments of the present invention.

[0035] As described in the background technology, during the drilling process of the shaft drilling rig, the working condition of the drill tool is very bad and the stress condition is very complicated. The joint is the weakest link in the drill tool, which is very easy to fail during the drilling process and may be stuck. With the continuous deepening of mineral resource development, the drilling of complex strata and deep strata has become the current direction of drilling development. Deep wells, ultra-deep wells and high-intensity drilling have put forward higher requirements for drill tool joints. At present, whether it is a double-shoulder drill pipe thread or a single-shoulder drill pipe thread, only the male and female thread are backed off to release stress.

[0036] There are two types of conventional joint structures commonly used. One is a single shoulder with a stress relief groove. This type of joint structure is very easy to fail under the action of strong torque, which can easily cause underground sticking, expansion or disengagement accidents; the other is a double shoulder with a stress relief groove. Although it avoids the increase in local deformation and stress concentration caused by the insufficient height of the end buckle when the connection is rotated to this point, and reduces the risk of cracking and fracture at this point, when the torque is too large and exceeds the allowable stress of the material, the contact surface deforms, and the main and auxiliary shoulders can simultaneously withstand the component forces under the action of the torque. At the same time, when the buckle is removed, the main and auxiliary shoulders will also be subject to friction resistance at the same time, resulting in biting and inability to remove.

[0037] In view of the above-mentioned technical problems, the embodiment of the first aspect of the present invention proposes a stress relief groove structure on the end face of a male thread. In some embodiments of the present invention, Figure 1-Figure 2 As shown, the stress relief groove structure of the male thread end face includes:

[0038] The first connecting rod has one end connected to the drill bit; the first connecting rod has a through hole along its axial direction; the inner wall of the through hole forms a first conical surface, the first conical surface corresponds to the other end of the first connecting rod, and the thread opened on the surface of the first conical surface is a female thread.

[0039] The second connecting rod is provided with a second conical surface at the end, and the thread opened on the surface of the second conical surface is a male thread; the second conical surface is connected to the first conical surface by a thread, and the part of the second connecting rod corresponding to the second conical surface can move in the through hole to avoid mutual jamming, which solves the problem that when the torque is too large and exceeds the allowable stress of the material, the contact surface is deformed, the main and auxiliary shoulders can simultaneously withstand the component force under the action of the torque, and at the same time, the main and auxiliary shoulders will also be subjected to friction resistance at the same time when the buckle is removed, resulting in jamming and inability to remove.

[0040] A positioning surface circumferentially connected to the second conical surface is formed on the second connecting rod along the radial direction of the through hole, and the positioning surface can abut against the end surface of the first connecting rod to avoid movement of the first connecting rod and the second connecting rod in the absence of an applied force; a stress groove is provided on the side of the positioning surface close to the second conical surface; the inner wall of the stress groove is used to connect the positioning surface and the second conical surface to reduce the degree of transition of stress streamlines between the positioning surface and the second conical surface. Stress streamlines are virtual lines that represent the transmission path of internal forces of the material to avoid the area being subjected to higher stress when these lines gather in a small area.

[0041] Among them, the stress groove corresponds to the large diameter end of the second conical surface. When the first conical surface transfers the force to the second conical surface, the opening of the stress groove shrinks or expands. The generation of corners or sharp points is eliminated. The stress streamlines need to bypass these geometric features, resulting in stress redistribution in these areas. Due to the change in stress path, the material at the corner needs to bear more load, resulting in stress concentration. Due to geometric constraints, the deformation space of the material is limited, resulting in larger or more complex deformations in these areas than in other areas. Uneven deformation further causes stress concentration in local areas.

[0042] The present invention provides a stress release groove structure of a male thread end face, wherein one end of a first connecting rod is connected to a drill bit, indicating that the connecting rod is directly involved in the drilling operation and is responsible for transmitting the rotation and propulsion force of the drilling rig to the drill bit. The connecting rod has a through hole extending along its axial direction, which is usually used to transmit drilling fluid. The functions of the drilling fluid include cooling the drill bit, removing drill cuttings, and maintaining the stability of the well wall. A first conical surface is formed on the inner wall of the through hole, and this design is conducive to the effective transmission and distribution of force. The conical surface provides a connection method that can be self-centering and withstand a large load. The design of the first conical surface allows the connecting rod to be connected to another part having a corresponding conical surface (usually a corresponding male conical surface). This conical connection can provide good force transmission efficiency and self-locking function due to the large contact area, and reduce the possibility of loosening of the connection under high load. The female thread opened on the surface of the first conical surface allows the corresponding male thread to cooperate with the corresponding male thread to achieve a tight and reliable mechanical connection. In addition to transmitting torque, the threaded connection is also easy to assemble and disassemble, which improves the flexibility and maintenance efficiency of the entire drilling system. The through hole acts as a fluid channel to ensure that the drilling fluid can be transferred from the inside of the connecting rod to the drill bit, achieving cooling, lubrication and cuttings removal during the drilling process. This is a key factor in maintaining the efficient operation of the drill bit and extending the life of the drill bit.

[0043] The male thread on the second conical surface at the end of the second connecting rod cooperates with the female thread of the first connecting rod to achieve a tight connection between the two connecting rods. This conical thread connection provides high torque transmission capacity and good self-locking performance, ensuring the stability of the connection. The part of the second connecting rod corresponding to the second conical surface can move in the through hole of the first connecting rod. This design allows a certain range of axial or radial adjustment to adapt to slight deformation or position deviation during assembly and operation, avoiding the problem of hard top. By providing a connection method that can self-adjust to a certain extent, the design of the second connecting rod effectively avoids the problems of contact surface deformation, jamming and difficulty in shackle caused by excessive torque or excessive material stress. When the male thread of the second conical surface is screwed with the female thread of the first connecting rod, the design of the conical surface ensures good contact and force transmission even under high load. Compared with straight threads, conical threads can more evenly distribute loads and reduce local stress concentration. The movable design of the second connecting rod in the through hole of the first connecting rod allows self-adjustment when subjected to axial thrust or torque. This adjustment capability reduces the excessive stress that may occur due to the fixed connection, especially when the torque increases suddenly or there is a slight deformation of the contact surface. When releasing (shackle), the mobility of the second link allows it to adjust its position to reduce friction and engagement between the primary and secondary shoulders, thus simplifying the removal process and reducing the risk of seizure caused by excessive friction.

[0044] The positioning surface is formed on the second connecting rod along the radial direction of the through hole and can abut against the end surface of the first connecting rod. This design prevents unnecessary movement between the first connecting rod and the second connecting rod when there is no external load, and maintains the stability of the connection and the correct relative position. The stress groove is located on the side of the positioning surface close to the second conical surface. Its function is to connect the positioning surface and the second conical surface, and optimize the transition of stress streamlines between the two surfaces, reducing the risk of stress concentration. Stress concentration usually occurs at the sudden change of the structure, such as sharp angles or geometric sudden changes. The stress groove alleviates this phenomenon by providing a transition area. Through the design of the positioning surface, when the second connecting rod is assembled to the first connecting rod, it can achieve precise positioning through the contact between the positioning surface and the end surface of the first connecting rod. This contact limits any slight movement when there is no axial load, ensuring the accuracy of assembly and the stability of the system. The design of the stress groove takes into account the transmission path of force inside the material (i.e., stress streamline). In the structural design, any sudden change may cause the stress streamline to gather and cause local stress concentration. The stress groove changes the path of the stress streamline by providing a smooth transition area, so that the stress can be more evenly distributed over a larger area. The result of this uniform distribution is a reduction in local stress peaks, improving the durability and reliability of the structure. The presence of the stress groove reduces the degree of stress streamline transition between the locating surface and the second tapered surface, which means that the transition between these two structural features is smoother, reducing possible stress concentration. In addition, the stress groove helps maintain the overall strength and stability of the structure under loads such as torque or axial force.

[0045] The design of the stress groove allows its opening to change dynamically (shrink or increase) when it is subjected to the force from the first tapered surface. This change can adapt to the force changes during the connection process or operation, reducing the stress concentration caused by the sudden change of force. By eliminating the generation of corners or sharp points, the stress groove design avoids the stress concentration problems common in traditional structures. In the structural design without sharp angles or mutations, the stress streamlines can pass more smoothly, reducing the local stress value. The stress groove improves the stress transfer path from the locating surface to the second tapered surface by providing a more gradual transition area. This design helps to reduce the uneven deformation caused by geometric constraints, thereby achieving a more uniform stress distribution. When the force is transmitted from the first tapered surface to the second tapered surface, the change in the opening of the stress groove allows the stress streamlines to be dynamically adjusted inside the connecting rod. This adjustment allows the stress to be distributed over a wider area instead of being concentrated on narrow or sharp geometric features. By alleviating the mutation of the stress path, the stress groove design helps to reduce the local stress peak. When the stress streamlines can flow smoothly in the structure without sharp corners, the accumulation of stress in a small area is avoided, thereby reducing the risk of fatigue failure. The dynamic response capability of the stress groove ensures that the connection structure can adaptively adjust the stress distribution when the applied force increases or decreases. This not only improves the reliability of the structure, but also increases its stability and durability under different working conditions.

[0046] In any of the above embodiments, the opening direction of the stress groove is the same as the axial direction of the first connecting rod; when the second connecting rod abuts against the end surface of the first connecting rod through the positioning surface, the end surface of the first connecting rod covers the stress groove.

[0047] In this embodiment, the stress groove helps to reduce stress concentration by changing the path of the stress streamline, especially at sharp angles or geometric discontinuities that may exist at the connection. When the first conical surface transfers the force to the second conical surface, the opening of the stress groove may deform (shrink or increase) accordingly according to the load size. This dynamic change helps to adjust the contact stress and further reduce the stress concentration effect. When the second connecting rod abuts the end face of the first connecting rod through the positioning surface, the stress groove is covered by the end face of the first connecting rod, which not only provides additional structural support, but also protects the stress groove from direct external influences, such as contamination or mechanical damage.

[0048] The presence of the stress groove reduces stress concentration caused by geometric mutations, making the force from the first connecting rod to the second connecting rod more evenly distributed. This is achieved by providing a gradual geometric shape, so that the stress can be dispersed over a wider area instead of concentrating on sharp corners or mutation points. In actual use, as the applied force changes, the stress groove can adapt to different load conditions by changing its shape, thereby optimizing the stress state of the connection. This dynamic adaptability reduces the risk of local excessive deformation and damage caused by overload or uneven load. When the end face of the first connecting rod covers the stress groove, it provides a smooth and continuous support surface, which helps to further disperse the force passing through the area. In addition, this design also protects the stress groove from direct contact with the external environment, preventing damage and corrosion, and extending the service life of the connecting rod.

[0049] In any of the above embodiments, the stress groove is located outside the through hole, so that the action exerted by the first connecting rod on the second connecting rod can be directly received by the stress groove.

[0050] In this embodiment, the stress groove is designed outside the through hole of the second connecting rod, close to the area in contact with the first connecting rod, so that the force applied by the first connecting rod to the second connecting rod can be directly received by the stress groove. This design helps to directly affect the initial distribution of forces. The presence of the stress groove provides a geometric feature that reduces stress concentration, especially in the force transmission path. By changing the distribution of force in the material, the stress groove helps to reduce the high local stress values ​​caused by geometric mutations or sharp angles. The design of the stress groove improves the layout of stress streamlines (i.e., the virtual path for force transmission inside the material) and avoids the accumulation of force in a small area, which is crucial to preventing material fatigue and cracks.

[0051] When the first link applies force to the second link, this structural feature receives the applied force first, as the stress groove is located outside the through hole and close to the contact surface. The stress groove changes the way the force is distributed on the second link through its shape and position, so that the force is transmitted more evenly to the rest of the link. The stress groove reduces the sharp transition and accumulation of stress streamlines by providing a geometrically smooth transition zone, especially at the corners and edges of the connection. This smooth transition allows the force to be more evenly distributed in the structure of the link, reducing the risk of local stress concentration. By optimizing the stress distribution, the stress groove also helps to make the deformation of the material more uniform when it is subjected to force. Compared with the design without stress grooves, this structure can reduce the increase of internal stress caused by uneven deformation, thereby improving the overall stability and durability of the structure. Due to the presence of the stress groove, when the first link and the second link contact through the positioning surface, the stress groove can effectively disperse the stress on the contact surface, reducing the possibility of deformation or damage of the direct contact surface due to excessive pressure.

[0052] In any of the above embodiments, a first tool retreat groove is formed at the end with a larger diameter of the first tapered surface, and a second tool retreat groove is formed at the end with a larger diameter of the second tapered surface.

[0053] When the positioning surface abuts the end face of the first connecting rod, the first tool recess corresponds to the second conical surface along the radial direction of the first connecting rod, and / or the second tool recess is staggered with the second cone along the radial direction of the first connecting rod. When a large axial force is generated, axial deformation can be performed to reduce stress concentration.

[0054] In this embodiment, the design of the relief groove improves the force transmission path from the first connecting rod to the second connecting rod. By providing the relief groove at the large diameter end of the tapered surface, a decompression zone can be introduced in the threaded connection portion, which helps to evenly distribute the force, thereby reducing local stress concentration. In structural design, any geometric discontinuity or sharp angle may cause stress concentration. The relief groove reduces this discontinuity by providing a transition zone, allowing stress to be evenly distributed over a wider area, thereby reducing the risk of damage that may be caused by stress concentration. The relief groove also helps to improve the stability of the threaded connection. Under high torque or high load, the relief groove can reduce material deformation caused by stress concentration and ensure the integrity and long-term stability of the connection.

[0055] When the first connecting rod is connected to the second connecting rod by threading, the force is transmitted through the tapered surface. The undercut is located at the large diameter end of the tapered surface, which can introduce a deformation allowance zone on these transmission paths. This means that in this area, the material can have more room to deform, thereby dispersing the stress over a larger range and reducing the generation of local high stress values. By reducing local high stress, the undercut reduces the risk of fatigue damage in the threaded connection and extends the service life of the entire connection system. This is because stress concentration is one of the main causes of material fatigue and eventual fracture. During assembly and disassembly, the presence of the undercut allows a certain degree of self-adjustment. This self-adjustment ability helps to cope with small deviations in the assembly process, ensures the correct fit of the threaded connection, and reduces the additional stress caused by assembly errors.

[0056] Under the action of axial force, the first and second undercuts allow the connecting rod to deform in the axial direction. This deformation capacity can absorb and disperse the forces acting on the connection, reducing the risk of local stress concentration. Through the careful design of the undercut position and shape, a more uniform stress distribution can be generated in the connection. This helps to avoid material fatigue, cracking or fracture caused by stress concentration. When a large axial force is generated, this structural design helps to maintain the stability of the connection and maintain good performance even under high load conditions.

[0057] When an axial force acts on the connection, the first and second relief grooves provide a physical way to allow the material to undergo a small elastic or plastic deformation in the axial direction. This deformation is performed without affecting the overall structural integrity of the connection. The presence of the relief groove changes the stress transfer path in the connection. In the absence of the relief groove, sharp geometric transitions and abrupt changes may cause stress concentration. The relief groove reduces the degree of local stress concentration by providing a more gradual geometric transition, allowing the stress to be distributed over a larger area. During the deformation process, the relief groove structure allows the connection to adaptively adjust to the load changes. This adaptive ability further enhances the stability and reliability of the connection, especially when facing dynamic conditions such as cyclic loading or vibration.

[0058] In any of the above embodiments, the stress groove is connected to the second undercut groove, so as to reduce the entity structure of the second connecting rod between the stress groove and the second undercut groove, thereby further reducing stress concentration.

[0059] When the positioning surface abuts the end face of the first connecting rod, the inner wall of the stress groove, the inner wall of the second backing groove and the surface of the first conical surface form a deformation cavity. After axial sectioning of the second connecting rod, the deformation cavity on one side is L-shaped, which is adapted to stress application in more directions.

[0060] In this embodiment, the interconnected design of the stress groove and the second undercut creates a composite decompression channel that provides a smoother stress transition area in the structure, thereby reducing the possibility of local stress concentration. By forming a connected stress groove and undercut on the second connecting rod, the amount of material in the area is reduced, thereby reducing the local structural stiffness. This reduction in stiffness helps to increase the deformation capacity of the structure, enabling it to better disperse stress under load. This design not only reduces stress concentration, but also enhances the stability of the entire connection by providing a more uniform stress distribution, especially under long-term or cyclic loads.

[0061] The interconnected design of the stress groove and the second relief groove changes the way stress is distributed in the second connecting rod. When external loads (such as axial force or torque) act on the connecting rod, this design allows stress to be more evenly distributed along the connected groove, reducing the high stress concentration areas that usually occur at sharp angles or sudden geometric structures. The connected groove structure provides additional deformation space, allowing the material in this area to undergo more elastic or plastic deformation under load. This deformation helps absorb and distribute the applied force, thereby reducing the risk of material fatigue or damage caused by stress concentration. By reducing stress concentration and improving stress distribution, the connected stress groove and relief groove design helps to extend the fatigue life of the material. This is critical to ensuring the reliability and durability of drilling equipment and other high-performance mechanical systems.

[0062] The L-shaped design of the deformation cavity can adapt to stresses applied from different directions, including axial and radial forces. This adaptability enables the connection system to maintain stability and performance under complex loading conditions. By creating a deformation cavity in the connection structure, stresses generated at sharp angles, sudden geometry or other potential stress concentration areas can be effectively dispersed and relieved. The deformation cavity provides a physical path so that stress can be distributed over a wider area, reducing the risk of local stress concentration. The L-shaped deformation cavity increases the deformation space of the material when the load is applied, allowing the structure to undergo more elastic or plastic deformation without compromising its integrity. This deformation ability helps absorb loads and reduce fatigue and damage caused by stress concentration.

[0063] When transferring forces from the first link to the second link, the structural design of the L-shaped deformation cavity guides the stress to be distributed in a more uniform manner and redirects the stress path when necessary. This redirection reduces the concentration of too much stress at a specific point, especially in the area of ​​geometric mutation of the connection. The design of the L-shaped deformation cavity not only provides additional deformation space, but also optimizes the shape and position of this space to maximize its stress absorption and dispersion capabilities in all directions. This design allows the structure to self-adjust when subjected to abnormal loads, mitigating potential structural damage. By reducing stress concentration and providing an efficient deformation path, the L-shaped deformation cavity helps maintain the integrity of the connection structure, even in the face of repeated or multi-directional loads. This design strategy enhances the reliability and durability of the entire system.

[0064] In any of the above embodiments, the stress groove is filled with lubricating liquid, and the deformation cavity is connected to the abutment between the positioning surface and the end surface of the first connecting rod and the threaded connection between the second tapered surface and the first tapered surface. The lubricating liquid can lubricate the adhesion between the end surface and the positioning surface and the area between the male thread and the female thread so that the disengagement can be smoother. And the stress groove is an axial opening to facilitate the pre-addition of lubricant before the first connecting rod and the second connecting rod are connected.

[0065] In this embodiment, by filling the key contact points with lubricating liquid, friction and wear are reduced during connection and separation (especially when removing the threaded connection), making the operation smoother. The lubricating liquid not only reduces friction, but also prevents adhesion between metal surfaces and corrosion caused by long-term contact, thereby extending the service life of the connection parts. The presence of the lubricating liquid in the stress groove further optimizes the stress distribution, and indirectly reduces the stress concentration phenomenon by reducing friction.

[0066] The axial opening design of the stress groove allows the pre-addition of lubricant before the first connecting rod and the second connecting rod are connected, ensuring that there is sufficient lubrication at the beginning of the connection process. This method of pre-adding lubricant improves the efficiency and reliability of the entire connection process. During the connection and separation process, the lubricating liquid moves in the stress groove and the deformation cavity, and is dynamically distributed to the contact area between the positioning surface and the end face of the first connecting rod and the contact area between the male thread and the female thread as needed. This dynamic distribution mechanism ensures that the friction coefficient remains low during the entire operation, reducing the operating resistance. The presence of lubrication reduces the force required for connection and separation, which not only makes the operation easier, but also reduces the risk of errors or damage caused by difficult operation.

[0067] Furthermore, along the axial direction of the first connecting rod, the groove depth of the stress groove is a; along the radial direction of the first connecting rod, the single-side width of the stress groove is b, then: a=0.70b-0.85b, so as to take into account the flow properties of the lubricating fluid and the flatness of the stress streamline of the stress groove.

[0068] As can be seen from the above, by adjusting the ratio of the groove depth to the width, the effective flow of the lubricant in the stress groove can be ensured. It not only helps the lubricant to reach all necessary contact points during the connection and disassembly of the drill pipe, but also maintains a good lubrication state and reduces friction and wear. The geometric design of the stress groove is strongly related to the distribution pattern of the guiding stress streamlines in the material. By selecting the ratio of the groove depth to the groove width, the design optimizes the distribution of stress at the connection part, effectively reduces the stress concentration phenomenon, and thus improves the overall strength and durability of the structure.

[0069] The flow properties of the lubricant in the stress groove directly affect the lubrication effect of the threaded joint. The ratio of a=0.8b ensures that the groove depth is sufficient to accommodate and guide the lubricant, while the groove width ensures that the lubricant can cover a sufficient contact area for effective lubrication. This balanced design is conducive to the distribution and retention of the lubricant, and avoids the situation where the lubricant is squeezed out of the contact area during high-pressure operations. The flatness of the stress streamline is an important indicator to measure the uniformity of stress distribution in the material. By adjusting the depth and width of the stress groove, the stress streamline path inside the material can be changed to make it smoother and more uniform. Such a design reduces the probability of stress concentration on sharp edges or mutation areas, thereby reducing the risk of material fatigue and fracture.

[0070] Furthermore, for the relationship between a and b in a fixed ratio range, the following formula is used to solve a:

[0071]

[0072] Where F represents the force acting on the second link, E represents the elastic modulus of the material,

[0073] σy represents the yield strength of the material, K represents a factor that takes into account the influence of the curvature of the tapered surface, n represents the influence factor of the material plasticity, and α represents the geometric factor of the engagement with the male and female threads.

[0074] As can be seen above, by comprehensively considering multiple factors such as mechanical properties, geometry and material properties, we attempt to provide a more comprehensive and accurate perspective to estimate the impact of stress groove depth on the overall structural performance. This complex calculation method is designed to more accurately simulate the conditions in actual applications and provide customized solutions for specific design needs.

[0075] Specifically, for b and the tooth depth d of the male and female threads on the tapered surface, the following formula is used to solve:

[0076] b=λ×d γ ;

[0077] Wherein, d represents the tooth depth of the thread, λ represents the material difference coefficient of the second tapered surface, and γ represents the material difference coefficient of the first tapered surface.

[0078] As can be seen from the above, the thread tooth depth d, as well as λ and γ, which represent the difference coefficients of the materials of the second tapered surface and the first tapered surface, respectively, constitute a framework for the design of threaded connections and stress grooves. Here, λ and γ are used to quantify and adjust the impact of material property differences in threaded connections on the design, especially when considering the size and shape of the stress groove. Designers can more finely adjust and optimize the size and shape of the stress groove in the threaded connection to ensure that the performance and stability of the connection are maintained even in the face of significant differences in material properties. This approach provides a flexible design strategy that enables threaded connections to adapt to a wide range of application requirements and material combinations, thereby achieving higher reliability and efficiency.

[0079] In any of the above embodiments, the stress groove is a circumferential ring; along the radial direction of the first connecting rod, the outer edge of the stress groove is provided with a rounded corner. The rounded corner causes the stress groove to deform and shrink when receiving a large stress, so as to guide the internal lubricant through the rounded corner between the end face and the positioning surface to avoid adhesion between the two. λ and γ quantify the difference between the material properties of the second conical surface and the reference standard or relative material (which may be the material of the first conical surface). This coefficient can be used to adjust the stress groove design to compensate for the effects caused by differences in the hardness, strength, elastic modulus, etc. of the second conical surface material. The reference standard or relative material is selected to be alloy steel or high-strength aluminum alloy.

[0080] In this embodiment, the annular stress groove naturally acts as a lubricant distribution channel through its design, allowing the lubricant to evenly cover the entire contact surface and provide a continuous and effective lubrication effect. When subjected to greater stress, the design of the stress groove allows it to deform or shrink moderately. This dynamic deformation helps to push the lubricant to the contact area more effectively, reducing friction and adhesion caused by high stress. The rounded corner design not only helps to guide the lubricant, but also avoids stress concentration caused by sharp angles. At the same time, when the lubricant flows through these rounded corners, it effectively reduces the risk of adhesion at the threaded connection.

[0081] When the first connecting rod and the second connecting rod are connected, the lubricant in the stress groove is pushed to the contact surface due to the relative movement and pressure change between the connecting rods. The structure of the annular stress groove ensures that the lubricant is evenly distributed along the circumference of the entire connection surface. Under the action of external stress (especially large stress), the deformation or contraction behavior of the stress groove further promotes the movement of the lubricant to the part that needs lubrication. The presence of the fillet makes the lubricant flow smoother and also reduces any possible lubricant leakage or overflow. The fillet design of the stress groove not only reduces local stress concentration, but also acts as an effective guiding structure when the lubricant flows, ensuring that the lubricant can accurately reach the contact area between the positioning surface and the end face of the first connecting rod. This ensures that the connection area can maintain a good lubrication state even under high load conditions.

[0082] In any of the above embodiments, a plurality of spaced-apart square grooves are provided on the side wall of the second connecting rod along the axial direction of the first connecting rod, and at least one shoulder is formed on the side wall of the second connecting rod.

[0083] The positioning surface is located on a shoulder close to the second tapered surface. The shoulder formed by the square groove can be deformed together with the stress groove when it deforms, further reducing stress concentration.

[0084] In this embodiment, a shoulder is formed on the side wall of the second connecting rod to form a stable mechanical support with the first connecting rod or other matching parts, thereby improving the structural stability of the connection. The square groove design helps to evenly distribute the stress from the operation or working conditions on the second connecting rod. The square grooves arranged at intervals can create multiple stress dispersion points inside the material, reducing the possibility of local stress concentration. The square grooves can also serve as channels or storage areas for lubricants, helping to provide continuous lubrication between the connection interfaces and reduce wear and friction, especially under high load or high speed operating conditions.

[0085] The shoulder provides a significant blocking surface in the structure, which can form a close fit with the first connecting rod or corresponding structural component. This physical contact point provides additional support force to help maintain the accuracy and stability of the connection. The square grooves arranged at intervals help change the transmission path of stress in the connecting rod by providing discontinuous structural features. When external forces act on the connecting rod, these square grooves act as stress dispersion areas, so that the stress is not overly concentrated on a single point or line, but distributed over a wider area, thereby improving the durability of the overall structure. The lubricant in the square groove can be gradually released to the contact surface during operation, ensuring a good lubrication state of the connection. This self-lubricating function reduces heat and wear caused by friction and extends the service life of the components.

[0086] By opening a square groove and forming a shoulder on the side wall of the second connecting rod, this structure can deform in a controlled manner when subjected to external forces. This deformation helps to disperse local stress and reduce stress concentration. The positioning surface is located on the shoulder, which not only enhances the accuracy and stability of positioning, but also increases the contact area during connection due to the presence of the shoulder, improving the strength and reliability of the connection. When the stress groove deforms, the design of the shoulder allows the entire structure to deform adaptively, further reducing stress concentration while maintaining the integrity of the connection.

[0087] The presence of the square groove provides physical space so that the side wall can deform moderately when subjected to axial or radial forces. This deformation helps to disperse the stress generated by the load in the connection area over a larger range, avoiding the formation of high stress concentration areas at sharp edges or geometric mutations. When the stress groove is deformed by external forces, the shoulder formed by the square groove will also deform accordingly. This synchronous deformation helps to maintain the mechanical balance of the entire connection and reduce local stress peaks through deformation coordination. During the connection and separation process, the locating surface on the shoulder provides an optimized contact area, which helps to keep the lubricant where it is needed. Especially when the stress groove and shoulder are deformed, the lubricant can be effectively directed to the critical contact area, reducing friction and wear and improving the smoothness of operation.

[0088] In any of the above embodiments, along the axial direction of the first connecting rod, the stress groove and the square groove are staggered to avoid the stress groove and the square groove being provided at the same time, which would cause the axial force bearing performance defect of the second connecting rod.

[0089] In this embodiment, by staggering the stress grooves and the square grooves, the material is avoided from being reduced at the same axial position, thereby maintaining the structural strength and rigidity of the connecting rod. This helps to ensure that the connecting rod can withstand high-intensity axial and radial loads. The staggered groove design allows for a more uniform stress distribution inside the second connecting rod. This layout helps to disperse the stress that may be concentrated at a single groove and reduce material fatigue or damage caused by stress concentration. With this design, the axial force performance of the second connecting rod is enhanced because it avoids the groove area from becoming a potential breaking point, thereby improving the reliability and safety of the connecting rod in practical applications.

[0090] When stress grooves and square grooves are set in the connecting rod, the position and layout of the grooves are crucial to influencing the distribution of stresses in the material. The staggered arrangement means that the grooves are arranged alternately in the axial direction, avoiding excessive reduction in material strength on any single cross-section, thereby ensuring a more uniform force distribution in all directions. Because the stress grooves and square grooves are not in the same axial position, each groove acts on a different cross-section, which can disperse the load over a wider area and reduce stress concentration in specific areas, especially when external forces are applied. This groove layout strategy also means that the connecting rod can provide a certain degree of deformation allowance at each square groove when it encounters bending or torsional loads, without causing excessive stress concentration at a specific point.

[0091] The embodiment of the second aspect of the present invention provides a drill rod. In some embodiments of the present invention, the drill rod comprises the stress relief groove structure on the end face of the male thread of any of the above embodiments.

[0092] The drill rod provided by the present invention includes the stress release groove structure on the end face of the male thread as in any of the above-mentioned embodiments. Therefore, the drill rod provided by the second aspect of the present invention has all the technical effects of the stress release groove structure on the end face of the male thread, which will not be repeated here.

[0093] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0094] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A stress relief groove structure on the end face of a male thread, characterized in that: include: A first connecting rod, one end of which is connected to the drill bit; the first connecting rod has a through hole along its axial direction; the inner wall of the through hole is formed with a first conical surface, and the first conical surface corresponds to the other end of the first connecting rod; A second connecting rod, with a second conical surface provided at the end thereof; the second conical surface is connected to the first conical surface by threads; a positioning surface connected to the circumferential direction of the second conical surface is formed on the second connecting rod along the radial direction of the through hole; a stress groove is provided on the side of the positioning surface close to the second conical surface; the inner wall of the stress groove is used to connect the positioning surface and the second conical surface to reduce the degree of transition of the stress streamline between the positioning surface and the second conical surface; the opening direction of the stress groove is the same as the axial direction of the first connecting rod; when the second connecting rod abuts against the end face of the first connecting rod through the positioning surface, the end face of the first connecting rod covers the stress groove; The stress groove corresponds to the larger diameter end of the second conical surface, and when the first conical surface transmits force to the second conical surface, the opening of the stress groove shrinks or expands.

2. The stress release groove structure on the end face of the male thread according to claim 1 is characterized in that: The stress groove is located outside the through hole.

3. The stress release groove structure on the end face of the male thread according to claim 1, characterized in that: A first tool-relief groove is formed at a larger diameter end of the first tapered surface, and a second tool-relief groove is formed at a larger diameter end of the second tapered surface; When the positioning surface abuts against the end surface of the first connecting rod, the first tool relief groove corresponds to the second tapered surface along the radial direction of the first connecting rod, and / or the second tool relief groove is staggered with the second tapered surface along the radial direction of the first connecting rod.

4. The stress release groove structure on the end face of the male thread according to claim 3 is characterized in that: The stress groove is connected to the second tool-relief groove; When the positioning surface abuts against the end surface of the first connecting rod, the inner wall of the stress groove, the inner wall of the second tool relief groove and the surface of the first tapered surface form a deformation cavity.

5. The stress release groove structure on the end face of the male thread according to claim 4, characterized in that: The stress groove is filled with lubricating liquid, and the deformation cavity is respectively connected to the abutment between the positioning surface and the end surface of the first connecting rod and the threaded connection between the second conical surface and the first conical surface.

6. The stress release groove structure on the end face of the male thread according to claim 5, characterized in that: The stress groove is in the shape of a circumferential ring; along the radial direction of the first connecting rod, the outer edge of the stress groove is provided with a rounded corner.

7. The stress release groove structure on the end face of the male thread according to claim 1, characterized in that: A plurality of spaced-apart square grooves are provided on the side wall of the second connecting rod along the axial direction of the first connecting rod, and at least one shoulder is formed on the side wall of the second connecting rod; Wherein, the positioning surface is located on the shoulder close to the second tapered surface.

8. The stress release groove structure on the end face of the male thread according to claim 7, characterized in that: Along the axial direction of the first connecting rod, the stress groove and the square groove are staggered.

9. A drill pipe, characterized in that: It comprises the stress relief groove structure on the end face of the male thread as described in any one of claims 1-8.

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