Bidirectional clamping high-temperature test fixture for drill rod

Abstract

The invention relates to the technical field of drilling and production equipment testing tools, in particular to a drill rod bidirectional clamping high-temperature testing clamp which comprises a shell, an outer wall clamping mechanism and an inner wall clamping mechanism, and the outer wall clamping mechanism and the inner wall clamping mechanism are arranged in the shell. The outer wall clamping mechanism comprises a contraction elastic clamping sleeve and a first driving device in driving connection with the contraction elastic clamping sleeve, and the inner wall clamping mechanism comprises an expansion elastic clamping sleeve and a second driving device in driving connection with the expansion elastic clamping sleeve. The contraction elastic clamping sleeve and the expansion elastic clamping sleeve are coaxially arranged in a spaced mode, and a clamping channel used for clamping the end of the drill rod is formed between the inner wall of the contraction elastic clamping sleeve and the outer wall of the expansion elastic clamping sleeve. The first driving device can drive the contraction elastic clamping sleeve to contract in the radial direction of the clamping channel, and the contraction elastic clamping sleeve expands and resets in the radial direction of the clamping channel after being undriven; the second driving device can drive the expansion elastic clamping sleeve to expand in the radial direction of the clamping channel, and the expansion elastic clamping sleeve shrinks and resets in the radial direction of the clamping channel after being undriven.

Description

Technical Field

[0001] This invention relates to the field of testing fixtures for drilling and production equipment, specifically to a bidirectional high-temperature testing fixture for drill pipes. Background Technology

[0002] As resource exploration and scientific drilling extend into deep formations, the deep sea, and geothermal environments, drill pipe, as a key component of the drill string system, faces increasingly harsh operating conditions, often needing to withstand temperatures exceeding 200°C and extremely high combined loads. Under such conditions, key mechanical properties of drill pipe materials, such as yield strength, fatigue life, and creep performance, will significantly degrade. Accurately assessing its high-temperature mechanical properties is crucial for wellbore structure design, drilling safety, and cost control.

[0003] The mechanical properties of drill pipe at high temperatures can be simulated using laboratory testing equipment. The performance of the drill pipe clamps in the testing equipment directly determines the validity of the data. However, existing clamps are insufficient to meet high-end testing requirements, and their main technical bottlenecks are reflected in the following aspects:

[0004] 1. Existing fixtures mostly adopt the external clamping type, which clamps the sample in one direction. At high temperatures, the external clamping type is prone to sample pressure damage due to increased interference. Especially for thin-walled drill pipes, this one-way external clamping method, that is, radial clamping of the drill pipe, is more likely to introduce additional bending moment or local stress concentration, resulting in distorted test results, or even sample fracture failure, making it impossible to complete the performance test smoothly.

[0005] 2. Insufficient adaptability to diameter changes. Traditional clamps are typically designed for specific diameters and lack adaptability to drill pipes of different diameters within a certain range. While shims or mechanical adjustments can achieve some diameter changes, the operation is cumbersome and it is difficult to ensure clamping coaxiality and uniform clamping force distribution. It is also difficult to achieve dynamic adaptive compensation of clamping surface gaps during high-temperature testing.

[0006] 3. Stress concentration at the clamping edge is prominent. Existing clamping fixtures often have obvious geometric abrupt changes at the clamping end, leading to stress concentration. This makes it easier for the drill pipe surface to be crushed, develop microcracks, or undergo plastic deformation at the edge of the clamping area, forming fatigue sources, compromising the integrity of the sample, and affecting the accuracy of high-temperature mechanical property tests, especially fatigue and fracture performance tests.

[0007] 4. Lack of measures for maintaining and compensating clamping force under high-temperature conditions. High temperatures cause thermal mismatch between different material components of the clamp, resulting in a decrease in the preset clamping force. Existing technologies lack proactive and intelligent force compensation methods, relying only on excessive pre-tightening or empirical estimation, which severely restricts the precise control of clamping force stability at high temperatures, especially during temperature changes, making it difficult to meet the requirements of long-term high-temperature creep and fatigue tests.

[0008] Therefore, there is an urgent need for a high-performance fixture that can solve the above problems in order to overcome the bottleneck of clamping technology in drill pipe mechanical testing under high temperature and complex load conditions. Summary of the Invention

[0009] (a) Technical problems to be solved

[0010] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a bidirectional clamping high-temperature test fixture for drill pipes, which solves the technical problems of existing drill pipe test fixtures being prone to damage to drill pipes when clamped in a single direction under high temperature and complex load conditions, and having poor ability to adapt to drill pipes of different diameters when changing diameter.

[0011] (II) Technical Solution

[0012] To achieve the above objectives, the bidirectional clamping high-temperature test fixture for drill pipes of the present invention includes a housing, and an outer wall clamping mechanism and an inner wall clamping mechanism built into the housing;

[0013] The outer wall clamping mechanism includes a shrinking elastic sleeve and a first driving device drivenly connected to the shrinking elastic sleeve. The inner wall clamping mechanism includes an expanding elastic sleeve and a second driving device drivenly connected to the expanding elastic sleeve. The shrinking elastic sleeve and the expanding elastic sleeve are coaxially spaced apart, and a clamping channel for clamping the drill pipe end is formed between the inner wall of the shrinking elastic sleeve and the outer wall of the expanding elastic sleeve.

[0014] The first driving device can drive the retractable elastic sleeve to retract radially along the clamping channel, and the retractable elastic sleeve can re-expand radially along the clamping channel to reset after the driving is removed;

[0015] The second driving device can drive the expansion elastic sleeve to expand radially along the clamping channel, and the expansion elastic sleeve will retract and reset radially along the clamping channel after the driving is removed.

[0016] Optionally, the second drive device includes a driver and an expander;

[0017] The driver is connected to the housing; the expander is built into the expansion elastic sleeve; the output shaft of the driver is connected to the expansion elastic sleeve so as to drive the expander to expand or contract radially along the clamping channel, and the expander can uniformly squeeze the inner wall of the expansion elastic sleeve during expansion.

[0018] Optionally, a T-shaped hanger is provided inside the housing; the expander is an elastic ring; and the output shaft of the driver is connected to a compression plate.

[0019] The extrusion plate and the elastic ring are both sleeved on the T-shaped hanger; the expansion elastic sleeve is suspended on the T-shaped hanger;

[0020] The output shaft of the driver can drive the extrusion plate to extrude the elastic ring along the axial direction of the clamping channel.

[0021] Optionally, the inner wall clamping mechanism further includes a shape memory alloy scale ring embedded in the elastic ring;

[0022] The shape memory alloy ring is fitted onto the T-shaped pendant; the shape memory alloy ring can undergo phase change expansion at a preset temperature, so that the shape memory alloy ring can expand radially and drive the elastic ring to expand.

[0023] Optionally, multiple sets of the shape memory alloy scale rings are arranged along the axial direction of the expanded elastic jacket, and the preset temperature at which the phase transformation occurs is sequentially increased or decreased.

[0024] Optionally, the inner wall of the expandable elastic sleeve is vertically connected to a cross-shaped connector; the cross-shaped connector includes an annular ring and multiple connecting strips arranged around the annular ring;

[0025] The annular ring is fitted onto the T-shaped hanger and is axially supported by the T-shaped hanger;

[0026] The free end of the connecting strip is connected to the inner wall of the expandable elastic sleeve; the inner wall of the expandable elastic sleeve, the annular ring, and a pair of adjacent connecting strips form a deformation adaptive opening.

[0027] Optionally, the contractile elastic sleeve is a multi-lobed contractile elastic sleeve;

[0028] The outer wall of the multi-lobed contractile elastic jacket has multiple stress relief grooves that run axially through it along its circumference.

[0029] Optionally, the walls of the contractile elastic sleeve and / or the expansion elastic sleeve are provided with axially extending extension buffer sections.

[0030] Optionally, chamfers are provided on the outer walls of both ends of the extended buffer section.

[0031] Optionally, the first driving device includes a plurality of radial hydraulic pistons arranged circumferentially around the contractile elastic jacket; the second driving device includes an axial hydraulic piston arranged axially along the expansion elastic jacket.

[0032] The housing has a bidirectional integrated annular groove oil cavity, and both the radial hydraulic piston and the axial hydraulic piston are disposed in the bidirectional integrated annular groove oil cavity.

[0033] Multiple radial hydraulic pistons can simultaneously compress the outer wall of the retractable elastic jacket along the radial direction of the clamping channel;

[0034] The axial hydraulic piston can compress the inner wall of the expanding elastic jacket along the axial direction of the clamping channel.

[0035] (III) Beneficial Effects

[0036] The beneficial effects of this invention are:

[0037] The bidirectional clamping high-temperature test fixture achieves efficient and reliable bidirectional coordinated clamping of drill pipe samples. A first driving device drives the retractable elastic sleeve to radially contract along the clamping channel, while a second driving device drives the expandable elastic sleeve to radially expand along the clamping channel, achieving bidirectional clamping of the drill pipe end. This ensures the symmetry and synchronization of the clamping forces, effectively avoiding the force imbalance problem of unidirectional clamping, and is particularly suitable for high-precision testing of thin-walled drill pipes.

[0038] The bidirectional clamping high-temperature testing fixture possesses excellent adaptive capability for varying diameters. Both the shrinking elastic sleeve and the expanding elastic sleeve are elastic components, capable of radial elastic contraction and expansion. This allows them to adaptively grip the outer and inner walls of drill pipes of different diameters within a certain size range through elastic deformation, constructing an elastic clamping channel. It is highly versatile and easy to operate.

[0039] Both the inner and outer walls of the drill pipe are subjected to elastic compression. The bidirectional elastic compression clamping method makes the clamping force relatively gentle, effectively protecting the end of the drill pipe and ensuring the integrity of the drill pipe after the test. Attached Figure Description

[0040] Figure 1 This is a perspective view of the bidirectional clamping high-temperature test fixture for drill pipes according to the present invention;

[0041] Figure 2 This is a cross-sectional view of the bidirectional clamping high-temperature test fixture for drill pipes according to the present invention;

[0042] Figure 3 This is a schematic diagram of the bidirectional integrated annular groove oil cavity inside the housing of the present invention;

[0043] Figure 4 This is a schematic diagram showing the connection between the T-shaped pendant, the shape memory alloy scale ring, and the elastic ring of the present invention;

[0044] Figure 5 This is a top view of the expansion elastic sleeve of the present invention;

[0045] Figure 6 This is a schematic diagram of the structure of the shrinkable elastic jacket of the present invention;

[0046] Figure 7This is a schematic diagram of the installation of the drill pipe sample to be tested in the testing machine according to the present invention;

[0047] Figure 8 This is a schematic diagram showing the connection between the drill pipe sample to be tested and a pair of bidirectional clamping high-temperature test fixtures according to the present invention.

[0048] Explanation of reference numerals in the attached figures

[0049] 1: Housing; 101: Drill pipe end face limiting surface; 102: Drill pipe sample to be tested; 103: Testing machine; 104: T-shaped hanger;

[0050] 2: Two-way integrated annular groove oil cavity;

[0051] 3: Radial hydraulic piston;

[0052] 4: Shrinkable elastic sleeve;

[0053] 5: Axial hydraulic piston;

[0054] 6: Extruded plate;

[0055] 7: Elastic band;

[0056] 8: Expandable elastic sleeve; 801: Annular ring; 802: Connecting strip; 803: Deformation adaptive opening; 804: Inner ring;

[0057] 9: Shape memory alloy scale ring; 901: First scale ring; 902: Second scale ring; 903: Third scale ring; 904: Fourth scale ring;

[0058] 10: First extended buffer section;

[0059] 11: Stress relief groove;

[0060] 12: T-type sealing ring;

[0061] 13: Second extended buffer section. Detailed Implementation

[0062] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0063] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0064] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0065] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; "connection" can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0066] See Figures 1 to 3 This invention provides a bidirectional high-temperature testing fixture for drill pipes. The bidirectional high-temperature testing fixture includes a housing 1, and an outer wall clamping mechanism and an inner wall clamping mechanism built into the housing 1. The outer wall clamping mechanism includes a contractile elastic sleeve 4 and a first driving device drivenly connected to the contractile elastic sleeve 4. The inner wall clamping mechanism includes an expandable elastic sleeve 8 and a second driving device drivenly connected to the expandable elastic sleeve 8. The contractile elastic sleeve 4 and the expandable elastic sleeve 8 are coaxially spaced apart, and a clamping channel for clamping the end of the drill pipe is formed between the inner wall of the contractile elastic sleeve 4 and the outer wall of the expandable elastic sleeve 8. The first driving device can drive the contractile elastic sleeve 4 to contract radially along the clamping channel, and the contractile elastic sleeve 4 expands and resets radially along the clamping channel after the driving is removed. The second driving device can drive the expandable elastic sleeve 8 to expand radially along the clamping channel, and the expandable elastic sleeve 8 contracts and resets radially along the clamping channel after the driving is removed.

[0067] The first and second drive devices can be selectively activated or activated simultaneously. Activating one can eliminate the other drive device, simplifying the equipment structure. When neither drive device is activated, the radial dimension of the clamping channel between the contractile elastic sleeve 4 and the expansion elastic sleeve 8 is greater than the wall thickness of the drill rod end, allowing the drill rod to smoothly enter the clamping channel. When the first and second drive devices are activated, the contractile elastic sleeve 4 is driven to press inward against the outer wall of the drill rod, while the expansion elastic sleeve 8 presses outward against the inner wall of the drill rod, achieving bidirectional clamping of the drill rod in its radial direction. Furthermore, both the inner and outer walls of the drill rod are subjected to elastic compression. This bidirectional elastic compression clamping method results in a gentler clamping force, effectively protecting the drill rod end and ensuring the integrity of the drill rod after testing.

[0068] In this embodiment, the outer wall clamping mechanism includes a radial hydraulic piston 3 and a contractile elastic sleeve 4 coaxial with the housing 1; the inner wall clamping mechanism includes an axial hydraulic piston 5, an elastic ring 7, and an expanding elastic sleeve 8 coaxial with the housing 1; a clamping channel is formed between the inner wall of the contractile elastic sleeve 4 and the outer wall of the expanding elastic sleeve 8; the elastic ring 7 is built into the expanding elastic sleeve 8; the axial hydraulic piston 5 can squeeze the elastic ring 7 along the axial direction of the expanding elastic sleeve 8, so that the elastic ring 7 expands radially and drives the expanding elastic sleeve 8 to expand; a bidirectional integrated annular groove oil cavity 2 is provided inside the housing 1; the radial hydraulic piston 3 and the axial hydraulic piston 5 are both disposed in the bidirectional integrated annular groove oil cavity 2, so that after pressure oil is introduced, the axial hydraulic piston 5 can squeeze the contractile elastic sleeve 4 to contract radially along the clamping channel, and at the same time, the radial hydraulic piston 3 can squeeze the elastic ring 7 to expand radially along the clamping channel, that is, squeeze the expanding elastic sleeve 8 to expand radially.

[0069] Specifically, an axial hydraulic piston 5 is provided at the top of the housing 1; the bottom of the housing 1 is open to allow the end of the drill rod to pass into the clamping channel; multiple radial hydraulic pistons 3 are evenly arranged on the side wall of the housing 1. The elastic ring 7 is a spring ring, and the outer ring of the spring ring should be able to fully contact the inner wall of the expanding elastic sleeve 8. The contraction elastic sleeve 4 and the expansion elastic sleeve 8 can be made of 60Si2Mn (silicon manganese spring steel) or 50CrVA (chromium vanadium spring steel), suitable for medium and high temperature (not exceeding 300℃) fatigue clamping scenarios. Furthermore, the elastic ring 7, the contraction elastic sleeve 4, and the expansion elastic sleeve 8 can all automatically reset during the reset process of the hydraulic piston, without the need for manual reset, effectively improving the testing efficiency when testing multiple drill rods.

[0070] It should be noted that the deformation of the shrinkage elastic sleeve 4 and the expansion elastic sleeve 8 should not be too large. They can be used to clamp the end of the drill pipe with a wall thickness of 5mm to 20mm to ensure the clamping stability and positioning accuracy of the shrinkage elastic sleeve 4 and the expansion elastic sleeve 8 on the end of the drill pipe, thereby ensuring the accuracy of the test data.

[0071] The axial hydraulic piston 5 can compress the elastic ring 7 along the axial direction of the expanding elastic sleeve 8, causing the elastic ring 7 to expand radially and drive the expanding elastic sleeve 8 to expand. In this way, the axial movement of the axial hydraulic piston 5 is converted into the radial expansion movement of the expanding elastic sleeve 8, enabling the expanding elastic sleeve 8 to work in conjunction with the contracting elastic sleeve 4 to perform radial clamping. On the one hand, this provides internal support force for the drill pipe, preventing the drill pipe from being crushed by the contracting elastic sleeve 4. On the other hand, it improves the axial friction limiting capability of the drill pipe, enhances the connection stability between the drill pipe and the fixture during the test, and thus improves the test accuracy.

[0072] The bidirectional integrated annular groove oil chamber 2 is connected to the external oil supply pipeline, which can simultaneously provide pressurized oil to the radial and axial hydraulic pistons for synchronously driving the radial hydraulic piston 3 to move radially and the axial hydraulic piston 5 to move axially. This realizes the function of a single hydraulic source driving the fixture to perform bidirectional clamping, optimizes the driving components of the clamping structure, improves clamping efficiency and release efficiency, and saves equipment costs.

[0073] The radial hydraulic piston 3 can be equipped with a spherical crown-shaped piston head to ensure full contact between the radial hydraulic piston 3 and the outer wall of the compressive elastic jacket 4. Pressurized oil is introduced into the bidirectional integrated annular groove oil chamber 2, and multiple radial hydraulic pistons 3 uniformly radially compress the outer wall of the compressive elastic jacket 4, causing the compressive elastic jacket 4 to radially contract to clamp the outer wall of the drill pipe; at the same time, the axial hydraulic piston 5 axially compresses the top surface of the elastic ring 7, causing the elastic ring 7 to radially expand, which in turn drives the expansion elastic jacket 8 to radially expand to clamp the inner wall of the drill pipe, ultimately achieving bidirectional clamping of the drill pipe end.

[0074] The bidirectional clamping high-temperature test fixture achieves efficient and reliable bidirectional coordinated clamping of drill pipe samples. A first driving device drives the retractable elastic sleeve 4 to radially contract along the clamping channel, while a second driving device drives the expanding elastic sleeve 8 to radially expand along the clamping channel, achieving bidirectional clamping of the drill pipe end. This ensures the symmetry and synchronization of the clamping forces, effectively avoiding the force imbalance problem of unidirectional clamping, and is particularly suitable for high-precision testing of thin-walled drill pipes.

[0075] The bidirectional clamping high-temperature test fixture has excellent adaptive capability for varying diameters. Both the shrinking elastic sleeve 4 and the expanding elastic sleeve 8 are elastic components, capable of radial elastic contraction and expansion. This allows them to adaptively clamp the outer and inner walls of drill pipes of different diameters within a certain size range through elastic deformation, thus constructing an elastic clamping channel. It is highly versatile and easy to operate.

[0076] See Figure 4 The inner wall clamping mechanism also includes a shape memory alloy ring 9 (SMA ring) built into the elastic ring 7. The shape memory alloy ring 9 undergoes phase transformation expansion at a preset temperature, allowing it to expand radially and drive the elastic ring 7 to expand as well. Specifically, the elastic ring 7 and the shape memory alloy ring 9 are connected in a contact manner, transmitting force through contact to ensure sufficient radial deformation without restricting minute axial deformation displacement. In a high-temperature testing environment, when the temperature reaches the phase transformation point of the shape memory alloy ring 9, it undergoes an austenitic phase transformation, generating significant expansion force. This expansion force is directly converted into radial expansion force, achieving radial pushing of the expanding elastic sleeve 8. This combined motion with the expanding elastic sleeve 8 enhances the overall radial expansion force of the expanding elastic sleeve 8, effectively compensating for the decrease in clamping force at high temperatures.

[0077] It should be noted that the "reset" of the shape memory alloy ring 9 is achieved through the contraction force generated during the reset process of the elastic ring 7. That is, the "reset" of the shape memory alloy ring 9 only involves contraction towards its inward side, rather than returning it to its original position. This characteristic allows the outer ring of the shape memory alloy ring 9 and the inner ring attached to the elastic ring 7 to exhibit faster response speeds when reaching the phase transition temperature in subsequent tests, thus saving test time.

[0078] Furthermore, the second driving device includes a driver and an expander; the driver is connected to the housing 1; the expander is built into the expanding elastic sleeve 8; the output shaft of the driver is connected to the expanding elastic sleeve 8, so as to drive the expander to expand or contract radially along the clamping channel. During expansion, the expander can uniformly squeeze the inner wall of the expanding elastic sleeve 8. Specifically, the driver is a linear driver, which can be a cylinder, a hydraulic cylinder, or an electric push rod. In this embodiment, linear drive is achieved by a hydraulic piston cooperating with the bidirectional integrated annular groove oil chamber 2. The expander can expand radially and can be a trilobal, butterfly, or annular expander, as well as a balloon expander, flange expander, etc. In this embodiment, an elastic ring 7 is selected. The advantage of the elastic ring 7 is that it has sufficient space inside to install the shape memory alloy scale ring 9, and at the same time, it cooperates with the shape memory alloy scale ring 9 to expand radially, providing a more stable internal support force for the drill pipe end. The expander can squeeze the inner wall of the drill pipe as uniformly as possible, so that the wall surface of the expanding elastic sleeve 8 can expand radially evenly, so as to distribute the clamping force on the inner wall of the drill pipe and avoid damaging the inner wall of the drill pipe.

[0079] like Figure 4 As shown, multiple sets of shape memory alloy rings 9 are arranged along the axial direction of the expanding elastic jacket 8, and the preset temperatures corresponding to the phase transitions increase or decrease sequentially. In this embodiment, a first ring 901, a second ring 902, a third ring 903, and a fourth ring 904 are arranged sequentially from top to bottom along the axial direction, and the preset temperatures corresponding to the phase transitions increase sequentially, constructing a gradient phase transition temperature. The multiple sets of shape memory alloy rings 9 can be activated sequentially during the temperature rise, generating controllable additional expansion force, intelligently compensating for the attenuation of clamping force caused by thermal mismatch, realizing dynamic stability of clamping force in high-temperature environments, and providing intelligent high-temperature clamping force compensation for bidirectional clamping high-temperature testing fixtures, that is, effectively compensating for the clamping force loss caused by the thermal expansion or mechanical performance degradation of other components due to high temperature, which is a core advantage not possessed by existing technologies.

[0080] Furthermore, the inner wall of the housing 1 facing the clamping channel is constructed as a drill rod end face limiting surface 101; the output shaft of the driver is connected to the extrusion plate 6; a T-shaped hanger 104 is provided inside the housing 1, coaxially connected to the drill rod end face limiting surface 101; the extrusion plate 6, the elastic ring 7, and the shape memory alloy scale ring 9 are all sleeved on the T-shaped hanger 104; the expansion elastic sleeve 8 is suspended on the T-shaped hanger 104; the extrusion plate 6 and the T-shaped hanger 104 are axially slidably connected; the axial hydraulic piston 5 can push the extrusion plate 6 to extrude the elastic ring 7. Specifically, the drill rod end face limiting surface 101 is used to abut against the end face of the drill rod, axially positioning the drill rod in a face-to-face abutment manner, and then the contraction elastic sleeve 4 and the expansion elastic sleeve 8 provide axial frictional resistance, improving the axial positioning of the drill rod and ensuring that the drill rod will not move axially during the test. In this embodiment, the top surface heights of both the shrinking elastic sleeve 4 and the expanding elastic sleeve 8 are lower than the height of the drill rod end face limiting surface 101, so that the bidirectional clamping high temperature test fixture clamps the drill rod closer to the end of the drill rod, rather than at the end, effectively avoiding the situation of damaging the drill rod due to clamping the end of the drill rod.

[0081] Compared to the axial hydraulic piston 5 directly compressing the elastic ring 7, the addition of a compression plate 6 to compress the elastic ring 7 effectively increases the axial thrust displacement of the axial hydraulic piston 5. Since the outer diameter of the compression plate 6 is no larger than the inner diameter of the expanding elastic sleeve 8, the compression plate 6 can slide axially on the T-shaped hanger 104 and slide to the inside of the expanding elastic sleeve 8 to abut against the top of the expanding elastic sleeve 8. The T-shaped hanger 104 is integrally set with the housing 1. The T-shaped hanger 104 includes a rod that fits into the corresponding component and a disc vertically connected to the bottom of the rod. The disc is used to support the expanding elastic sleeve 8, and its height is adapted to the displacement of the expanding elastic sleeve 8 during radial expansion, providing stable support force for the expanding elastic sleeve 8.

[0082] See Figure 5The inner wall of the expansion elastic sleeve 8 is vertically connected with a cross-shaped connector, which can be made of the same elastic material as the expansion elastic sleeve 8. The cross-shaped connector includes an annular ring 801 and multiple connecting strips 802 arranged around the annular ring 801. The annular ring 801 is sleeved on the T-shaped hanger 104 and is axially supported by the T-shaped hanger 104. The free ends of the connecting strips 802 are connected to the inner wall of the expansion elastic sleeve 8. The inner wall of the expansion elastic sleeve 8, the annular ring 801 and a pair of adjacent connecting strips 802 form a deformation adaptive opening 803. Specifically, during expansion, with the annular ring 801 as the center, multiple connecting strips 802 move radially along the wall of the expansion elastic sleeve 8. Since the contact area between the connecting strips 802 and the inner wall of the expansion elastic sleeve 8 is small, the total area of ​​the multiple deformation adaptive openings 803 is large, which makes the resistance of the cross-shaped connector to the radial expansion of the expansion elastic sleeve 8 small, so that the wall of the expansion elastic sleeve 8 can expand radially more uniformly, ensuring full contact between the outer wall of the expansion elastic sleeve 8 and the inner wall of the drill pipe.

[0083] Optionally, the cross-shaped connector also includes an inner ring 804. The inner ring 804 increases the contact area between the connecting strip 802 and the inner wall of the expansion elastic sleeve 8, reduces stress concentration at the connection during deformation, and improves the reliability of the cross-shaped connector, which integrates support and radial deformation follow-up performance.

[0084] Optionally, the end of the extrusion plate 6 facing the elastic ring 7 is constructed as a tapered end. On the one hand, the tapered section can contact the middle of the elastic ring 7, improving the axial extrusion effect on the elastic ring 7; on the other hand, the two sides of the tapered end are hollowed out, providing allowance for the axial deformation of the two sides of the elastic ring 7. Compared with the horizontal plate structure of the extrusion plate 6, the tapered structure of the extrusion plate 6 effectively avoids interference between its tapered surface and the two sides of the elastic ring 7 during axial extrusion, or the existence of greater axial resistance to the deformation of the two sides of the elastic ring 7, thereby improving the smoothness of the radial expansion of the elastic ring 7.

[0085] like Figure 6 As shown, the shrinkage elastic sleeve 4 is a multi-lobed shrinkage elastic sleeve; multiple stress relief grooves 11 are formed along the circumference of the outer wall of the multi-lobed shrinkage elastic sleeve. Specifically, after the shrinkage elastic sleeve 4 is formed with multiple stress relief grooves 11, it has a multi-lobed structure. The stress relief grooves 11 can provide radial and circumferential deformation allowance during the radial shrinkage of the shrinkage elastic sleeve 4, improve the stability and shape regularity of the radial deformation of the shrinkage elastic sleeve 4, so that the shrinkage elastic sleeve 4 can produce uniform radial shrinkage deformation, so as to achieve self-equilibrium distribution of pressure on the shrinkage elastic sleeve 4, adapt to drill pipes of different diameters and hold their outer wall tightly.

[0086] Furthermore, the walls of the contraction elastic sleeve 4 and / or expansion elastic sleeve 8 are correspondingly provided with axially extending extension buffer sections. In this embodiment, a first extension buffer section 10 is added to the bottom of the contraction elastic sleeve 4, and the inner diameter of the first extension buffer section 10 is consistent with the inner diameter of the contraction elastic sleeve 4; the contraction elastic sleeve 4 and the first extension buffer section 10 can be integrally formed. A second extension buffer section 13 is added to the bottom of the expansion elastic sleeve 8, and the inner diameter of the second extension buffer section 13 is consistent with the inner diameter of the expansion elastic sleeve 8; the expansion elastic sleeve 8 and the second extension buffer section 13 can be integrally formed. The extension buffer section correspondingly extends the axial length of the contraction elastic sleeve 4 or the expansion elastic sleeve 8, distributes the clamping force on the outer wall of the drill pipe, reduces the local stress of the drill pipe, and thus protects the integrity of the outer wall of the drill pipe.

[0087] Secondly, chamfers are provided on the outer walls of both ends of the extended buffer section, preferably rounded corners. This chamfer design effectively reduces stress concentration at the drill pipe clamping edges, significantly improving stress distribution at the clamping ends and preventing damage to the inner and outer walls of the drill pipe or the clamp itself during clamping. The bidirectional clamping high-temperature test clamp effectively suppresses stress concentration at the clamping edges. The extended buffer sections of the multi-lobed contractile elastic sleeve 4 and the expansion elastic sleeve 8, along with the chamfering at both ends of the extended buffer sections, smooth the transitional distribution of clamping force, significantly reduce boundary stress peaks, protect the integrity of the sample surface, and ensure the accuracy of the test data.

[0088] In addition, the bidirectional integrated annular groove oil chamber 2 is sealed to the housing 1 by a T-shaped sealing ring 12. Compared with the traditional O-ring seal, the T-shaped sealing ring 12 has better stability, temperature resistance and fatigue resistance, and is more suitable for high-temperature reciprocating motion conditions. The T-shaped sealing ring 12 effectively improves the sealing reliability between the radial hydraulic piston 3 and the housing 1 under high-temperature conditions, ensuring the stable application of radial pressure of the radial hydraulic piston 3.

[0089] This embodiment takes the 200℃ high-temperature tensile test of an S135 steel grade drill pipe sample (hereinafter referred to as drill pipe sample 102) with an outer diameter of Φ120mm and an inner diameter of Φ100mm as an example to illustrate the working process and method of the bidirectional clamping high-temperature testing fixture (hereinafter referred to as the fixture) of the present invention:

[0090] S1. Fixture Preparation and Installation

[0091] The fixture is securely mounted within the high-temperature heating furnace of an FLPL-G series metal high-temperature tensile and compressive fatigue testing machine via its housing 1. For example... Figure 7As shown, the outer shell 1 is connected to the upper and lower loading heads of the testing machine 103 via a conical sleeve locking structure to ensure coaxial force transmission and overall stability of the fixture. The oil inlet of the hydraulic system, namely the bidirectional integrated annular groove oil chamber 2, is connected to the external hydraulic control module of the testing machine 103 via a high-temperature resistant metal hose. The hydraulic system pressure is synchronously controlled by the control system of the testing machine 103 to achieve coordination of clamping and loading actions. The fixture is made of high-temperature resistant alloy material and is placed inside the high-temperature heating furnace chamber of the testing machine 103. Its exterior is covered with a high-temperature resistant sealing protective sleeve to prevent the hydraulic oil pipes and cables from aging due to heat and ensure long-term stable operation of the system. Connect the external hydraulic source to the oil inlet of the fixture and preset the hydraulic system pressure to 20MPa. Check the integrity of the T-type sealing ring 12 to ensure reliable sealing of the hydraulic system.

[0092] S2. Sample clamping and initial clamping

[0093] like Figure 8 As shown, the drill pipe sample 102 to be tested is placed at the center of the fixture, and the coaxiality of the axis is corrected to ensure uniform axial force transmission during loading. The hydraulic system is started, and pressurized oil enters the bidirectional integrated annular groove oil chamber 2.

[0094] Outward clamping process: The pressurized oil pushes the radial hydraulic piston 3 of the outer wall clamping mechanism to move radially inward. The spherical head of the radial hydraulic piston 3 forms surface contact with the multi-lobed shrinking elastic jacket 4 and applies a uniform compressive force. The stress relief groove 11 on the outer surface of the multi-lobed shrinking elastic jacket 4 undergoes elastic deformation, and its inner diameter shrinks uniformly from the initial Φ125mm to Φ120mm, thereby clamping the outer circle of the drill rod sample 102 to be tested.

[0095] Inward clamping process: Simultaneously, pressurized oil pushes the axial hydraulic piston 5 to move axially downward. The axial hydraulic piston 5 pushes the extrusion plate 6, converting the axial displacement into radial extrusion of the spring coil 7, causing its outer diameter to expand from Φ98mm to Φ100mm. The spring coil 7 pushes the expanding elastic sleeve 8 to expand radially, ultimately tightening it against the inner wall of the drill pipe. At this point, the initial clamping force of the inward clamping is mainly provided by the elastic deformation of the spring coil 7.

[0096] Thus, the clamping device completes the bidirectional coordinated clamping of the drill rod sample 102 under test through a single hydraulic action at room temperature, with symmetrical and uniform clamping force.

[0097] S3, High Temperature Testing and Intelligent Compensation

[0098] The heating furnace is started, and the ambient temperature is raised to 200℃ at a rate of 10℃ / min and held at that temperature. During this process, the coefficient of thermal expansion of the steel components such as the clamp housing 1, radial hydraulic piston 3, and axial hydraulic piston 5 is greater than that of the drill rod sample 102 to be tested, which will cause the clamping force of the clamping mechanism to decrease.

[0099] Among them, the first scale ring 901 to the fourth scale ring 904 are shape memory alloy scale rings that undergo austenitic phase transformation at the first phase transformation temperature to the fourth phase transformation temperature. In this embodiment, the first scale ring 901 is arranged in pairs, that is, a pair of scale rings are symmetrically arranged on the left and right sides of the T-shaped hanger 104, and the second scale ring 902 to the fourth scale ring 904 are arranged in pairs simultaneously.

[0100] When the temperature rises to 75°C, the first scale ring 901, which has a first phase transformation temperature of 70°C, undergoes an austenitic phase transformation, resulting in radial expansion. This exerts an additional radial expansion force on the spring ring 7, compensating for the clamping force loss at this temperature.

[0101] When the temperature continues to rise to 125℃ and 175℃, the second scale ring 902 and the third scale ring 903, with phase change temperatures of 120℃ and 170℃ respectively, are activated in sequence and undergo phase change expansion.

[0102] When the temperature reaches and stabilizes at 200℃, the fourth scaly ring 904, with a phase transition temperature of 190℃, is fully activated.

[0103] These four sets of shape memory alloy scale rings 9 with gradient phase transformation temperatures (70℃, 120℃, 170℃, 190℃) provide active radial force compensation in stages and smoothly throughout the heating process. This effectively compensates for the attenuation of inward clamping force caused by the "thermal mismatch" effect, ensuring that the clamping force remains within the preset stable range at the 200℃ test temperature.

[0104] S4. Test Execution and Termination

[0105] Under a 200℃ holding condition, the control system issues a command to apply a tensile load for mechanical property testing. Throughout the test, due to the dynamic stability of the bidirectional clamping force, the sample exhibits no slippage or abnormal noise, and the data curves are smooth and reliable.

[0106] After the test, the tensile load was unloaded, heating was stopped, and the sample was cooled to room temperature. The hydraulic pressure was released, and the elastic sleeve 4, spring ring 7, and expansion elastic sleeve 8 returned to their initial state under their own elastic restoring force, allowing the intact drill rod sample 102 to be easily removed.

[0107] This invention provides a bidirectional clamping high-temperature testing fixture, which achieves the following through a single hydraulic operation:

[0108] (1) Bidirectional adaptive clamping of drill rods of specific size can adapt to the clamping of drill rods of different diameters and thicknesses within a certain range.

[0109] (2) Through multiple sets of shape memory alloy scale rings 9 with temperature gradient, intelligent and active compensation of clamping force is achieved in a wide temperature range (room temperature to 200℃), which improves the stability of clamping force of the fixture at high temperature.

[0110] (3) The drill pipe is effectively protected by the first extended buffer section 10, the second extended buffer section 13 and the chamfer design. After testing, there are no indentations or cracks in the drill pipe clamping area.

[0111] The bidirectional clamping high-temperature testing fixture of the present invention is particularly suitable for high-temperature mechanical property testing of drill pipes in deep and ultra-deep wells, as well as high-temperature mechanical property testing of thin-walled drill pipes, providing an effective solution to the industry problem of reliable high-temperature clamping in existing material testing machines.

[0112] It should be understood that the above description of specific embodiments of the present invention is only for illustrating the technical approach and features of the present invention, and is intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, the present invention is not limited to the specific embodiments described above. All changes or modifications made within the scope of the claims of the present invention should be covered within the protection scope of the present invention.

Claims

1. A bidirectional clamping high-temperature testing fixture for drill pipes, characterized in that, The bidirectional clamping high temperature test fixture includes a housing (1), and an outer wall clamping mechanism and an inner wall clamping mechanism built into the housing (1); The outer wall clamping mechanism includes a shrinking elastic sleeve (4) and a first driving device drivenly connected to the shrinking elastic sleeve (4). The inner wall clamping mechanism includes an expanding elastic sleeve (8) and a second driving device drivenly connected to the expanding elastic sleeve (8). The shrinking elastic sleeve (4) and the expanding elastic sleeve (8) are coaxially spaced apart, and a clamping channel for clamping the end of the drill rod is formed between the inner wall of the shrinking elastic sleeve (4) and the outer wall of the expanding elastic sleeve (8). The first driving device can drive the retractable elastic sleeve (4) to retract radially along the clamping channel, and the retractable elastic sleeve (4) to re-expand radially along the clamping channel after the driving is removed; The second driving device can drive the expansion elastic sleeve (8) to expand radially along the clamping channel, and the expansion elastic sleeve (8) will retract and reset radially along the clamping channel after the driving is removed.

2. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 1, characterized in that, The second drive unit includes a driver and an expander; The driver is connected to the housing (1); the expander is built into the expansion elastic sleeve (8); the output shaft of the driver is connected to the expansion elastic sleeve (8) so as to drive the expander to expand or contract radially along the clamping channel, and the expander can uniformly squeeze the inner wall of the expansion elastic sleeve (8) when expanding.

3. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 2, characterized in that, The housing (1) is provided with a T-shaped hanger (104); the expander is an elastic ring (7); the output shaft of the driver is connected to a compression plate (6). The extrusion plate (6) and the elastic ring (7) are both sleeved on the T-shaped hanger (104); the expansion elastic sleeve (8) is suspended on the T-shaped hanger (104); The output shaft of the driver can drive the extrusion plate (6) to extrude the elastic ring (7) along the axial direction of the clamping channel.

4. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 3, characterized in that, The inner wall clamping mechanism also includes a shape memory alloy scale ring (9) built into the elastic ring (7); The shape memory alloy ring (9) is fitted onto the T-shaped pendant (104); the shape memory alloy ring (9) can undergo phase change expansion at a preset temperature, so that the shape memory alloy ring (9) can expand radially and drive the elastic ring (7) to expand.

5. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 4, characterized in that, Multiple sets of the shape memory alloy scale rings (9) are arranged along the axial direction of the expanded elastic jacket (8), and the preset temperature corresponding to the phase transformation increases or decreases sequentially.

6. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 3, characterized in that, The inner wall of the expansion elastic sleeve (8) is vertically connected with a cross-shaped connector; the cross-shaped connector includes an annular ring (801) and multiple connecting strips (802) arranged around the annular ring (801). The annular ring (801) is sleeved on the T-shaped hanger (104) and is axially supported by the T-shaped hanger (104); The free end of the connecting strip (802) is connected to the inner wall of the expansion elastic sleeve (8); the inner wall of the expansion elastic sleeve (8), the annular ring (801) and a pair of adjacent connecting strips (802) form a deformation adaptive opening (803).

7. The bidirectional clamping high-temperature test fixture for drill pipes according to any one of claims 1-6, characterized in that, The shrinkable elastic sleeve (4) is a multi-lobed shrinkable elastic sleeve; The outer wall of the multi-lobed contractile elastic jacket has multiple stress relief grooves (11) that run through the axial direction along its circumference.

8. The bidirectional clamping high-temperature test fixture for drill pipes according to any one of claims 1-6, characterized in that, The walls of the contractile elastic sleeve (4) and / or the expansion elastic sleeve (8) are provided with axially extending buffer sections.

9. The bidirectional clamping high-temperature test fixture for drill pipes according to claim 8, characterized in that, Chamfers are provided on the outer walls of both ends of the extended buffer section.

10. The bidirectional clamping high-temperature test fixture for drill pipes according to any one of claims 1-6, characterized in that, The first drive device includes a plurality of radial hydraulic pistons (3) arranged circumferentially around the contractile elastic jacket (4); the second drive device includes an axial hydraulic piston (5) arranged axially along the expansion elastic jacket (8). The housing (1) has a bidirectional integrated annular groove oil cavity (2), and the radial hydraulic piston (3) and the axial hydraulic piston (5) are both located in the bidirectional integrated annular groove oil cavity (2). Multiple radial hydraulic pistons (3) can simultaneously compress the outer wall of the retractable elastic sleeve (4) radially along the clamping channel; The axial hydraulic piston (5) is capable of pressing the inner wall of the expanding elastic sleeve (8) along the axial direction of the clamping channel.

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