A clamping device for sucker rod fatigue test

Abstract

The present invention discloses a clamping device for sucker rod fatigue test. A clamping device for sucker rod fatigue test includes sucker rod holders for clamping both ends of the sucker rod respectively. The sucker rod holders are composed of a holder A plate and a holder B plate with relatively fixed clamping surfaces. Clamping grooves are provided on the clamping surfaces of the holder A plate and the holder B plate. A plurality of clamping cylindrical surfaces with different diameters are staggered along the clamping grooves of the holder A plate and the holder B plate respectively. Among them, the small-diameter clamping cylindrical surface of the holder A plate is opposite to the large-diameter clamping cylindrical surface of the holder B plate. Due to the staggered arrangement of the small cylindrical surfaces, the overall deformation of the sucker rod is in an "S" shape, increasing the frictional force during clamping and improving the reliability of non-slip during clamping. Therefore, this clamping device can improve the success rate of the sucker rod fatigue test.

Description

Technical Field

[0001] The present invention relates to the technical field of sucker rod detection, and particularly relates to a clamping device for sucker rod fatigue test. Background Art

[0002] The sucker rod is an important device in the rod pumping system, which bears the load transfer movement between the pumping unit and the subsurface pump. Due to the alternating load it bears, the main failure form is fatigue failure. Therefore, the fatigue performance of the sucker rod is a key index affecting its service life.

[0003] Conducting fatigue test is the most direct and reliable way to obtain the fatigue performance of the sucker rod. The specimens used in the sucker rod fatigue performance test are divided into two types: Type I specimen and Type II specimen. The Type I specimen is a full-size short sucker rod specimen, which is produced according to the required size during the production process, and its manufacturing process is the same as the mass production process; the Type II specimen is intercepted from the finished sucker rods in mass production, which is a physical specimen of the sucker rod. Since the Type II specimen is randomly intercepted from the supplied products, the Type II specimen can better illustrate the quality status of this batch of sucker rods. However, when conducting the fatigue performance test on the Type II specimen, a clamping device is required to clamp the end of the sucker rod. However, due to the complex load situation at the clamping part of the sucker rod, it often fractures first, rather than the specimen fractures due to fatigue failure, resulting in the failure of the fatigue test. In view of this, it is necessary to design a new type of clamping block for the fatigue test of the Type II specimen of the sucker rod, in order to improve the test success rate. Summary of the Invention

[0004] In order to reduce the probability of the sucker rod fracturing at the clamping part during the fatigue test and improve the success rate of the fatigue test, the present invention provides a clamping device for sucker rod fatigue test, which has the characteristics of not being easy to slip during clamping and small strain at the clamping part.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A clamping device for sucker rod fatigue test, including sucker rod holders for clamping both ends of the sucker rod respectively, and the sucker rod holders are composed of a holder A plate and a holder B plate with relatively fixed clamping surfaces;

[0007] Clamping grooves are provided on the clamping surfaces of the holder A plate and the holder B plate, and a plurality of clamping cylindrical surfaces with different diameters are alternately arranged along the clamping grooves of the holder A plate and the holder B plate, wherein the small-diameter clamping cylindrical surface of the holder A plate is opposite to the large-diameter clamping cylindrical surface of the holder B plate.

[0008] The holder A plate and the holder B plate are fixedly connected by connecting bolts and nuts, and a spring washer is also provided between the nut and the holder B plate.

[0009] The clamping cylindrical surfaces of the clamping plate A and the clamping plate B are divided into three types: large, medium, and small. The diameter of the small cylindrical surface is 2 - 4 mm smaller than the diameter of the sucker rod to be clamped. The diameter of the medium cylindrical surface is equal to the diameter of the sucker rod to be clamped. The diameter of the large cylindrical surface is 2 - 4 mm larger than the diameter of the sucker rod to be clamped.

[0010] Among the said clamping cylindrical surfaces, the H and L surfaces are medium cylindrical surfaces, the I, J, and K surfaces are small cylindrical surfaces, and the E, F, and G surfaces are large cylindrical surfaces.

[0011] The H cylindrical surface and the L cylindrical surface of the clamping plate A and the clamping plate B are both medium cylindrical surfaces, which are relatively arranged at the two end faces of the clamping surface and are in contact with the sucker rod to be clamped.

[0012] The I cylindrical surface, the J cylindrical surface, and the K cylindrical surface of the clamping plate A are respectively opposite to the large cylindrical surfaces of the clamping plate B. That is, when the I cylindrical surface, the J cylindrical surface, and the K cylindrical surface are in contact with the sucker rod to be clamped, the cylindrical surfaces of the clamping plate B are not in contact with the sucker rod.

[0013] The I cylindrical surface and the J cylindrical surface of the clamping plate B are opposite to the large cylindrical surfaces of the clamping plate A. That is, when the I cylindrical surface and the J cylindrical surface are in contact with the sucker rod to be clamped, the cylindrical surfaces of the clamping plate A are not in contact with the sucker rod.

[0014] The outer surfaces C and D of the heads of the clamping plate A and the clamping plate B are planes that cooperate with the clamping blocks of the fatigue testing machine.

[0015] When clamping the sucker rod, there is a spacing of 3 - 8 mm between the clamping plate A and the clamping plate B.

[0016] A cylindrical pin for positioning and centering is also provided between the clamping plate A and the clamping plate B.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] For the sucker rod fatigue test clamping device provided by the present invention, when clamping the sucker rod, since the small cylindrical surface and the large cylindrical surface are opposite to each other, the stress on the sucker rod is small. When conducting the fatigue test, the large cylindrical surface provides space for the deformation of the sucker rod and reduces its local stress to ensure that the sucker rod will not break at the clamping part. At the same time, because the small cylindrical surfaces are arranged staggeredly, the overall deformation of the sucker rod is in an "S" shape, increasing the friction force during clamping and improving the reliability of non-slip during clamping. Therefore, this clamping device can reduce the probability of the sucker rod breaking at the clamping part during the fatigue test and improve the success rate of the fatigue test. This clamping device has the characteristics of simple structure, easy to manufacture, not easy to slip during clamping, and small strain at the clamping part. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of the present invention.

[0020] Figure 2 It is the top view of the structure of the present invention.

[0021] Figure 3 It is the side view of the structure of the present invention.

[0022] Figure 4 It is the schematic diagram of the staggered distribution of the clamping space of the present invention.

[0023] Figure 5 The radial load diagram of the sucker rod clamping part of the present invention.

[0024] Figure 6 It is the deformation diagram of the finite element analysis result of the sucker rod clamping part of the present invention.

[0025] Among them, 1 is the A plate of the clamp, 2 is the B plate of the clamp, 3 is the connecting bolt, 4 is the nut, 5 is the spring washer, and 6 is the cylindrical pin. Specific embodiments

[0026] The present invention will be further described in detail below with reference to the accompanying drawings. The following is an explanation rather than a limitation of the present invention.

[0027] See Figures 1 - 4 , a sucker rod fatigue test clamping device, including sucker rod clamps that respectively clamp the two ends of the sucker rod. The sucker rod clamps are composed of a clamp A plate 1 and a clamp B plate 2 with relatively fixed clamping surfaces;

[0028] Clamping grooves are provided on the clamping surfaces of the clamp A plate 1 and the clamp B plate 2. A plurality of clamping cylindrical surfaces with different diameters are staggered along the clamping grooves of the clamp A plate 1 and the clamp B plate 2. Among them, the small-diameter clamping cylindrical surface of the clamp A plate 1 is opposite to the large-diameter clamping cylindrical surface of the clamp B plate 2.

[0029] Furthermore, the clamp A plate 1 and the clamp B plate 2 are fixedly connected by connecting bolts 3 and nuts 4, and a spring washer 5 is also provided between the nut 4 and the clamp B plate.

[0030] Furthermore, the clamping cylindrical surfaces of the clamp A plate 1 and the clamp B plate 2 are divided into three types: large, medium, and small clamping cylindrical surfaces. The diameter of the small cylindrical surface is 2-4 mm smaller than the diameter of the clamped sucker rod, the diameter of the medium cylindrical surface is equal to the diameter of the clamped sucker rod, and the diameter of the large cylindrical surface is 2-4 mm larger than the diameter of the clamped sucker rod.

[0031] Specifically, among the clamping cylindrical surfaces, surfaces H and L are medium cylindrical surfaces, surfaces I, J, and K are small cylindrical surfaces, and surfaces E, F, and G are large cylindrical surfaces;

[0032] The H cylindrical surface and the L cylindrical surface of the gripper A plate 1 and the gripper B plate 2 are both middle cylindrical surfaces, which are relatively arranged at both end faces of the clamping surface; both are in contact with the clamped sucker rod.

[0033] The I cylindrical surface, the J cylindrical surface and the K cylindrical surface of the gripper A plate 1 are respectively opposite to the large cylindrical surface of the gripper B plate 2, that is, when the I cylindrical surface, the J cylindrical surface and the K cylindrical surface are in contact with the clamped sucker rod, the cylindrical surface of the gripper B plate 2 is not in contact with the sucker rod.

[0034] The I cylindrical surface and the J cylindrical surface of the gripper B plate 2 are opposite to the large cylindrical surface of the gripper A plate 1, that is, when the I cylindrical surface and the J cylindrical surface are in contact with the clamped sucker rod, the cylindrical surface of the gripper A plate 1 is not in contact with the sucker rod.

[0035] Specifically, the C surface and the D surface on the outer surface of the heads of the gripper A plate 1 and the gripper B plate 2 are planes that cooperate with the clamping blocks of the fatigue testing machine.

[0036] Specifically, when clamping the sucker rod, there is a spacing of 3 to 8 millimeters between the gripper A plate 1 and the gripper B plate 2.

[0037] Specifically, a cylindrical pin 6 for positioning and centering is also provided between the gripper A plate 1 and the gripper B plate 2.

[0038] Specific embodiments are given below.

[0039] Refer to the attached Figure 1 , a sucker rod fatigue test clamping device, which consists of two sets of sucker rod grippers with the same structure, and are respectively clamped at both ends of the sucker rod.

[0040] Refer to Figure 2 and Figure 3 , each set of sucker rod gripper includes a gripper A plate 1, a gripper B plate 2, a connecting bolt 3, a nut 4, a spring washer 5 and a cylindrical pin 6.

[0041] According to the distance from the sucker rod, the gripper A plate 1 and the gripper B plate 2 have an inner surface and an outer surface. The inner surface is close to the sucker rod, and the outer surface is far from the sucker rod.

[0042] Refer to the attached Figures 4 - 6 , there are two kinds of small and large cylindrical surfaces on the inner surfaces of the gripper A plate 1 and the B plate 2. The diameter of the small cylindrical surface is equal to the diameter of the clamped sucker rod, and the diameter of the large cylindrical surface is several millimeters larger than the diameter of the clamped sucker rod, and it is not in contact with the sucker rod.

[0043] Refer to the attached Figure 4, the sucker rod is placed between the clamp A plate 1 and the clamp B plate 2. The clamp A plate 1 and the clamp B plate 2 are connected by bolts, and the bolts are tightened to clamp the sucker rod. When tightening, the cylindrical pin is used for positioning to ensure the centering of the clamp A plate and the clamp B plate. After both sets of clamps clamp the sucker rod, it is installed on the fatigue testing machine. The C surface and D surface of the clamp A plate 1 and the clamp B plate 2 are in contact with the clamping blocks of the fatigue testing machine and bear the clamping force of the fatigue testing machine.

[0044] When clamping the sucker rod, since the small cylindrical surface and the large cylindrical surface face each other, the stress on the sucker rod is small; when performing the fatigue test, the large cylindrical surface provides space for the deformation of the sucker rod, reducing its local stress to ensure that the sucker rod will not break at the clamping position. At the same time, because the small cylindrical surfaces are staggered, the overall deformation of the sucker rod is in an "S" shape, increasing the friction force during clamping and improving the reliability of non-slip during clamping.

[0045] Refer to the appendix Figure 5 , when the sucker rod is clamped, its radial pressure is distributed staggeredly along the axial direction. Refer to the appendix Figure 6 , when the sucker rod is clamped, its deformation is bending deformation.

[0046] Specific trial experiment: The fatigue test clamping device of the present invention has been used for 7 fatigue tests in total. Among them, 5 tests were successful, and the success rate was 71.4%. The success rate of the test was increased by 46.1% compared with that of the "tooth-shaped fixture" test, and good application effects were obtained in the test. At the same time, for the 2 invalid tests, the uniformity and continuity of the rod body at the clamping position did not change. It is analyzed that the main reasons for the invalid test are the defects in the rod body at the clamping position or the poor coaxiality of the samples.

Claims

1. A clamping device for sucker rod fatigue test, characterized in that, It includes sucker rod holders that respectively clamp both ends of the sucker rod. The sucker rod holders are composed of a holder A plate (1) and a holder B plate (2) with relatively fixed clamping surfaces. Clamping grooves are provided on the clamping surfaces of the holder A plate (1) and the holder B plate (2). Along the clamping grooves of the holder A plate (1) and the holder B plate (2), a plurality of clamping cylindrical surfaces with different diameters are alternately arranged. Among them, the small-diameter clamping cylindrical surface of the holder A plate (1) is opposite to the large-diameter clamping cylindrical surface of the holder B plate (2). The clamping cylindrical surfaces of the holder A plate (1) and the holder B plate (2) are divided into three types: large, medium, and small clamping cylindrical surfaces. The diameter of the small cylindrical surface is 2 - 4 millimeters smaller than the diameter of the clamped sucker rod. The diameter of the medium cylindrical surface is equal to the diameter of the clamped sucker rod. The diameter of the large cylindrical surface is 2 - 4 millimeters larger than the diameter of the clamped sucker rod. Among the clamping cylindrical surfaces, the H and L surfaces are medium cylindrical surfaces, the I, J, and K surfaces are small cylindrical surfaces, and the E, F, and G surfaces are large cylindrical surfaces. The H cylindrical surface and the L cylindrical surface of the holder A plate (1) and the holder B plate (2) are both medium cylindrical surfaces, and are relatively arranged at both end faces of the clamping surface; both are in contact with the clamped sucker rod. The I cylindrical surface, J cylindrical surface, and K cylindrical surface of the holder A plate (1) are respectively opposite to the large cylindrical surfaces of the holder B plate (2). That is, when the I cylindrical surface, J cylindrical surface, and K cylindrical surface are in contact with the clamped sucker rod, the cylindrical surfaces of the holder B plate (2) are not in contact with the sucker rod. The I cylindrical surface and J cylindrical surface of the holder B plate (2) are opposite to the large cylindrical surfaces of the holder A plate (1). That is, when the I cylindrical surface and J cylindrical surface are in contact with the clamped sucker rod, the cylindrical surfaces of the holder A plate (1) are not in contact with the sucker rod. When clamping the sucker rod, there is a spacing of 3 - 8 millimeters between the holder A plate (1) and the holder B plate (2).

2. The fatigue test clamping device for sucker rods according to claim 1, wherein, The holder A plate (1) and the holder B plate (2) are fixedly connected by connecting bolts (3) and nuts (4). A spring washer (5) is also provided between the nut (4) and the holder B plate.

3. The sucker rod fatigue test clamping device according to claim 1, characterized in that, The C surface and D surface on the outer surface of the heads of the holder A plate (1) and the holder B plate (2) are planes that cooperate with the clamping blocks of the fatigue testing machine.

4. The sucker rod fatigue test clamping device according to claim 1, wherein, A cylindrical pin (6) for positioning and centering is also provided between the holder A plate (1) and the holder B plate (2).

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