Neutron diffraction test tool and method for deep residual stress of large-size ring cylinder piece

Abstract

The invention belongs to the technical field of residual stress detection, and particularly relates to a neutron diffraction test tool and method for deep residual stress of a large-size ring cylinder part. Wherein the testing tool is composed of a fixed bottom plate, a compression roller and a plurality of pairs of supporting roller sets, the multiple pairs of supporting roller sets are arranged at intervals in the axial direction of the annular cylinder part, the compression roller is arranged in the annular cylinder part in the axial direction of the annular cylinder part, and the two ends of the compression roller are fixedly connected with the neutron stress spectrometer sample platform respectively. The testing method comprises the steps of judging testing blind areas in all directions of the ring cylinder part and testing blind spots on the blind areas before testing, testing non-testing blind spots, and then testing the testing blind spots through a rotation deviation and drilling auxiliary method innovatively provided by the invention. The testing tool is simple in structure and convenient to machine, stable fixing of the ring cylinder part and rapid switching of axial strain testing points can be achieved, the testing efficiency is improved, precious neutron beam duration is saved, and the problem that the deep residual stress of the ring cylinder part cannot be measured is solved through the testing method.

Description

Technical Field

[0001] The present invention belongs to the technical field of residual stress detection, and particularly relates to a neutron diffraction test tooling and method for deep residual stress of large-sized ring barrel parts. Background Art

[0002] Residual stress refers to the self-equilibrated stress state that still exists inside a material without external load. During various manufacturing processes of components, such as forging / casting, heat treatment, or machining, various complex residual stresses are introduced. Residual stress exists in the component for a long time and is released as the component material is removed or an external load is applied, causing deformation or damage, seriously threatening the normal use state and long-term service life of the component. Therefore, accurate evaluation and measurement of the residual stress inside the component are very important.

[0003] Neutron diffraction technology is the only non-destructive stress test technology with high precision, high resolution, and the ability to measure deep stress. It penetrates the inside of the component with a neutron beam and measures the crystal plane spacing inside the component, thereby obtaining accurate deep stress of the component.

[0004] Mastering the deep stress of components can provide true and effective data for the evaluation of component service performance and life extension, and provide support for the improvement of component performance. In recent years, the demand for measuring the deep stress of components in key national fields by neutron diffraction technology has been increasing continuously, especially for large-sized structural components represented by ring barrel structures, such as: transition ring parts of carrier rocket fuel tanks, barrel-shaped parts of rockets / ammunition, pressure-resistant cabins for deep sea use, high-speed rail bearing rings, nuclear power plant pressure vessels, and pipeline components, etc.

[0005] When measuring the deep stress of large-sized ring barrel parts by neutron diffraction technology, it is necessary to solve the problems of being able to measure and measuring quickly in advance. Specifically: (1) Being able to measure: Due to the energy limitation of the neutron source, the penetration depth of neutrons through crystal materials is limited. Taking the engineering science stress spectrometer developed by Central South University and China Institute of Atomic Energy as an example, the maximum penetration depth for aluminum alloy is only 205 mm. For large-sized or thick-walled ring barrel parts, when testing some angles and regions, the neutron optical path passes through the material with too large a depth, exceeding the penetration depth limit, and no signal can be measured.

[0006] (2) Measuring quickly: The cost of neutron diffraction testing is high and the testing time is scarce (the neutron beam needs to be provided by a spallation neutron source or a reactor, and the total annual operating cost of the instrument and its supporting facilities reaches tens of millions of US dollars. There are only more than a dozen devices globally that can provide neutron diffraction stress measurement). During testing, it is necessary to measure the test points on different directions, different circular cross-sections, and different radial paths of the ring barrel part. Therefore, it needs to be placed laterally and vertically and rotated and moved. When the diffraction instrument is equipped with a sample platform and the ring barrel part is placed laterally, it is difficult to fix the workpiece and adjust the angle around the axis, the testing efficiency is low, a great deal of testing time is wasted, and the actual needs cannot be met.

[0007] At present, in the field of residual stress detection technology, neutron diffraction stress tests on ring-shaped components such as oil and gas pipelines and nuclear power pipelines have been reported, but there is a lack of reports on adjustable-angle fixing tooling, deep stress field auxiliary test methods, and test process optimization schemes for such workpieces. Patents related to the present invention, such as the invention patent application with the publication number CN115575426A, disclose a residual stress test platform based on neutron diffraction for large components and its experimental method, which provides a neutron diffraction test fixing tooling for disk-shaped components, but this fixing tooling cannot fix ring-shaped components without an axis.

[0008] Therefore, there is an urgent need to propose a neutron diffraction test tooling and method for deep residual stress of large-sized ring-shaped components, which will help solve the problems in the neutron diffraction test of deep residual stress of large-sized ring-shaped components and provide guidance for the deep stress test of workpieces such as cylinders and disks with similar structures. Summary of the Invention

[0009] The purpose of the present invention is to provide a neutron diffraction test tooling and method for deep residual stress of large-sized ring-shaped components, which is convenient for laterally fixing the workpiece and adjusting the angle around the axis during the neutron diffraction test of the ring-shaped component, as well as predicting and testing the test blind spots during the deep residual stress test, can improve the test efficiency, solve the problem that the blind spots cannot be tested, and meet the actual needs of the neutron diffraction test of deep residual stress of large-sized ring-shaped components.

[0010] To achieve the above purpose, the present invention provides a neutron diffraction test method for deep residual stress of large-sized ring-shaped components, including the following steps: S1. According to the structural dimension parameters of the ring-shaped component in the circumferential, axial, and radial directions to be tested, calculate the theoretical maximum optical path of the ring-shaped component in the three test directions respectively. By comparing the theoretical maximum optical path in the three test directions with the maximum penetration depth of the neutron beam to the ring-shaped component, judge whether there are test blind spots in the three test directions of the ring-shaped component; for the directions without test blind spots, directly conduct neutron diffraction tests; for the directions with test blind spots, make the next judgment; S2. For the directions with test blind spots on the ring-shaped component, calculate the actual optical path of each point to be tested in this direction, compare the actual optical path of each point to be tested in this direction with the maximum penetration depth of the neutron beam to the ring-shaped component, judge whether each point to be tested is a test blind spot, and finally determine all the test blind spots of the ring-shaped component in the direction with test blind spots; for the non-test blind spots in the direction with test blind spots, directly conduct neutron diffraction tests; for the non-test blind spots in the direction with test blind spots, make the next judgment; S3. For the test blind spots in the directions with test blind areas on the ring cylinder part, determine whether the actual optical path in the circumferential direction meets specific conditions; if it meets the specific conditions, the rotation offset method is adopted for testing; if it does not meet the specific conditions, the drilling assistance method is adopted for testing.

[0011] Further, in the step S1, the optical path for performing diffraction testing on a certain point to be measured on the ring cylinder part in a certain test direction is as follows: the intersection point of the neutron incident beam and the neutron diffraction beam is on the point to be measured, the included angle between the neutron incident beam and the neutron diffraction beam is 90°, and the bisector direction of the included angle between the neutron incident beam and the neutron diffraction beam points to the test direction of the test optical path; when measuring the circumferential stress and radial stress of the ring cylinder part, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two end faces of the ring cylinder part; when measuring the axial stress of the ring cylinder part, the plane where the neutron incident beam and the diffraction beam are located is perpendicular to the two end faces of the ring cylinder part.

[0012] Further, in the step S1, the calculation expression for the theoretical maximum optical path of the ring cylinder part in three test directions is: In the above formula, R is the outer diameter radius of the ring cylinder part, B is the wall thickness of the ring cylinder part, l is the axial length of the ring cylinder part, , , respectively correspond to the theoretical maximum optical paths of the ring cylinder part in the axial, circumferential, and radial directions.

[0013] Further, in the step S1, the method for determining whether there are test blind areas in each direction of the ring cylinder part is: compare the calculated theoretical maximum optical path in each direction with the maximum penetration depth of the neutron beam on the ring cylinder part. If the theoretical maximum optical path in a certain direction is greater than , then there is a test blind area in that direction; otherwise, there is no test blind area in that direction.

[0014] Further, the calculation expression for the actual optical path of each point to be measured in three test directions in the step S2 is: In the above formula, i is the point to be measured on the ring cylinder part, X i is the point to be measured i is the shortest distance from the point to be measured i to the outer wall of the ring cylinder part, Z i is the shortest distance from the point to be measured , , are respectively the point to be measured iThe actual optical path in the axial, circumferential, and radial directions.

[0015] Further, in step S2, the method for determining whether each point to be measured is a test blind spot is as follows: Compare the actual optical path of each point to be measured in a certain direction obtained by calculation with the maximum penetration depth of the neutron beam in the test spectrometer for the ring-shaped cylinder. If the actual optical path of the point to be measured in a certain direction is greater than , then the point to be measured is a test blind spot; otherwise, the point to be measured is not a test blind spot.

[0016] Further, in step S3, the specific condition is: If there is a test blind spot in the circumferential direction of the ring-shaped cylinder, and the test blind spot satisfies - ≤0.199 , then it is determined that the test blind spot can adopt the rotation offset method to reduce the optical path and make the point to be measured measurable; otherwise, the drilling assistance method is adopted for the test blind spot to make the point to be measured measurable.

[0017] Further, the rotation offset method is specifically as follows: First, increase the neutron diffraction wavelength so that the neutron diffraction angle increases by α, and the angle between the neutron incident beam and the neutron diffracted beam decreases by α / 2, where 0° < α ≤ 10°; subsequently, rotate the ring-shaped cylinder around its axis in a direction away from the neutron optical path by γ, where 0° < γ ≤ 5°, and the optical path of each point to be measured decreases; the increased amount of the diffraction angle α and the rotation angle γ of the ring-shaped cylinder need to meet the condition: the theoretical maximum optical path after offset is less than the maximum penetration depth of the neutron beam for the ring-shaped cylinder; the increased amount of the diffraction angle α and the rotation angle γ of the ring-shaped cylinder can be determined by the following formula: In the above formula, is the actual optical path of the ring-shaped cylinder in the circumferential direction after adopting the rotation offset method for this test blind spot.

[0018] Further, the drilling assistance method is specifically as follows: For the test blind spot in a certain direction, drill a first hole and a second hole at the incident and exit of the test optical path for the ring-shaped cylinder respectively. The radii of the first hole and the second hole are 5 - 10 mm, and the depth relationship between the first hole and the second hole is determined by the following formula: In the above formula, f 1 and f 2 are the depths of the first hole and the second hole respectively, is the actual optical path of the test blind spot during the test in a certain direction.

[0019] The present invention also provides a neutron diffraction test tooling for deep residual stress of large-sized ring barrel parts, including a fixed bottom plate for connecting with the sample platform of the neutron stress spectrometer, at least two pairs of support roller groups for supporting the ring barrel parts to be tested, and a pressure roller for limiting the ring barrel parts. The at least two pairs of support roller groups are arranged at intervals along the axial direction of the ring barrel parts, and the two support rollers in each pair of support roller groups are symmetrically arranged below the two radial sides of the ring barrel parts. The support roller group includes a support frame connected with the fixed bottom plate and a support roller rotatably installed on the support frame; the pressure roller is arranged inside the ring barrel parts, and both ends of the pressure roller extend to the outside of the ring barrel parts and are respectively fixedly connected with the sample platform of the neutron stress spectrometer through connecting parts; the positional relationship between the two support rollers in each pair of support roller groups satisfies the following formula: In the above formula, C is the axial center distance between the two support rollers in a pair of support roller groups, R is the outer diameter radius of the ring barrel part, d is the diameter of the support roller, H is the distance from the rotation axis center of the support roller to the fixed bottom plate, L is the designed distance from the bottommost part of the ring barrel part to the fixed bottom plate, usually L ≥10mm; The load-bearing capacity of the support roller satisfies the following formula: In the above formula, is the minimum load-bearing capacity that the support roller needs to meet, M is the mass of the ring barrel part, n is the number of support rollers, s is the safety factor, and g is the gravitational constant, taking 9.8m 2 / s.

[0020] In the above neutron diffraction test tooling, the machining flatness of the fixed bottom plate is less than 0.1mm; the pressure roller is in a round bar structure, and there are opening chutes at both ends of the pressure roller; the machining straightness error of the support roller fixing holes on the support frame is less than 0.1mm / m, and the support frame is connected with the fixed bottom plate through at least two bolts.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1). The present invention proposes a neutron diffraction test method for deep residual stress of large-sized ring barrel parts. Among them, two methods, namely the rotation offset method and the drilling assistance method, are innovatively proposed, which can significantly reduce the optical path and solve the problem that signals cannot be measured for the deep stress of large-sized and thick-walled ring barrels, providing guidance for solving the problem of insufficient penetration in the neutron diffraction test of deep stress of similar workpieces.

[0022] (2) The present invention provides a neutron diffraction test tooling for deep residual stress of large-sized ring barrel parts, which has a simple structure, is stable and reliable, and is convenient for processing. It helps to fix the ring barrel parts and switch the test points when measuring the axial stress, improves the test efficiency, and saves the precious neutron beam time.

[0023] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the accompanying drawings and describe the present invention in further detail. Description of the Drawings

[0024] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention, and constitute a part of the specification. They are used together with the following specific embodiments to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the accompanying drawings: Figure 1 is a three-dimensional structural schematic diagram of a neutron diffraction test tooling for deep stress of large-sized ring barrel parts of the present invention; Figure 2 is a side view structural schematic diagram of a neutron diffraction test tooling for deep stress of large-sized ring barrel parts of the present invention; Figure 3 is a test experimental diagram of a large-sized ring barrel part using the test tooling of the present invention in Embodiment 1 of the present invention; Figure 4 is the diffraction test optical path of the points to be measured of a large-sized ring barrel part of the present invention in three test directions; where: (a) is the diffraction test optical path diagram in the radial direction, (b) is the diffraction test optical path diagram in the tangential direction, and (c) is the diffraction test optical path diagram in the circumferential direction; Figure 5 is a flowchart of a neutron diffraction test method for deep residual stress of large-sized ring barrel parts of the present invention; Figure 6 is a schematic diagram of the points to be measured of deep residual stress of a large-sized ring barrel part in Embodiment 2 of the present invention; where: (a) is the positions of cross-section A and cross-section B on the ring barrel part, and (b) is the structural schematic diagram of cross-section A; Figure 7 is the signal result of neutron diffraction test using the drilling assistance method in Embodiment 2 of the present invention; Among them, 1 - fixed bottom plate; 2 - pressure roller; 3 - support frame; 4 - support roller; 5 - connecting piece; 6 - neutron stress spectrometer sample platform; 7 - ring barrel part. Detailed Description of the Embodiments

[0025] The following will describe the present invention in detail in conjunction with the various embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not limitations to the present invention. Any equivalent transformation or substitution in function, method, or structure made by those of ordinary skill in the art according to these embodiments shall fall within the protection scope of the present invention.

[0026] Example 1 Please refer to Figure 1 and Figure 2 As shown, this example provides a neutron diffraction test tooling for deep residual stress of large-sized ring barrel parts, including a fixed bottom plate 1 for connecting with the sample platform 6 of the neutron stress spectrometer, at least two pairs of support roller groups for supporting the ring barrel part 7, and a pressure roller 2 for limiting the ring barrel part 7. The at least two pairs of support roller groups are arranged at intervals along the axial direction of the ring barrel part 7. The two support rollers in each pair of support roller groups are symmetrically arranged below the two radial sides of the ring barrel part 7. The support roller group includes a support frame 3 connected to the fixed bottom plate 1 and a support roller 4 rotatably installed on the support frame 3. In this structural setting, the fixed bottom plate 1 is a plate member provided with a number of through holes. Its bottom is fixedly connected to the sample platform 6 of the neutron stress spectrometer. A pressure roller and a support pad are arranged above it. The pressure roller 2 is a rod-shaped structure arranged inside the ring barrel part 7. There are opening chutes at both ends of the pressure roller 2, and both ends of the pressure roller 2 extend to the outside of the ring barrel part 7 and are respectively fixedly connected to the sample platform 6 of the neutron stress spectrometer through connectors 5.

[0027] According to the geometric relationship, the calculation formula for the distance between the two support rollers 4 in a pair of support roller groups is derived as follows to determine the relative positions of the two support rollers on the fixed bottom plate: In the above formula, C is the center distance between the axes of the two support rollers in a pair of support roller groups, R is the outer diameter radius of the ring barrel part, d is the diameter of the support roller, H is the distance from the rotation axis of the support roller to the fixed bottom plate, L is the designed distance from the bottom of the ring barrel part to the fixed bottom plate. Usually L ≥10mm.

[0028] In this example, the test piece (ring barrel part) is a 7050 aluminum alloy shell section with an outer diameter of 655 mm, an inner diameter of 585 mm, a length of 560 mm, and a weight of about 106.89 kg. Substitute the outer diameter radius of the ring barrel part R = 327.5 mm, the diameter of the support roller d = 58 mm, the distance from the rotation axis of the support roller to the fixed bottom plate H = 45 mm, and the minimum designed distance from the bottom of the ring barrel part to the fixed bottom plate L = 10 mm into the formula to obtain that the center distance between the two support rollers should C max = 407.6 mm. According to the actual selection of C = 300 mm, L = 40.9 mm.

[0029] Derive the calculation formula for the load-bearing capacity selection of the support roll 4 based on the force relationship, which is used to determine the support roll model that meets the load-bearing capacity: In the above formula, is the minimum load-bearing capacity that the support roll needs to meet, with the unit of N, M is the total mass of the test piece, n is the number of support rolls, s is the safety factor, usually taking 1.5 - 2.

[0030] Regarding the mass of the ring cylinder part M = 106.89 kg, g = 9.8 m / s 2 , C = 300 mm, R = 327.5 mm, d = 58 mm, s Substitute = 1.5 into the above formula to obtain ≥ 1060.4856 N / n, and four support rolls with a load-bearing capacity exceeding 50 kg are selected and placed in pairs on both sides of the ring cylinder part.

[0031] In a specific implementation manner, to ensure the measurement effect, the flatness of the machining plane of the fixed base plate 1 is less than 0.1 mm; the straightness error of the machining of the support roll fixing holes on the support frame 3 is less than 0.1 mm / m. When the fixed base plate is connected to the support roll, the number of bolts arranged along the axial direction of the support roll is greater than 2.

[0032] During the test, first, fasten the fixed base plate 1 of the test fixture to the sample platform through bolts. Then, hoist the ring cylinder part between the support roll groups. After it is stably supported, adjust the position of the ring cylinder part by rotation and translation to accurately position the intersection point of the diffraction light beam to the measurement point. Subsequently, install the support rolls to clamp and fix the ring cylinder part 7. After confirming that the positioning is correct, the test can be carried out. During the test, the specific placement of the ring cylinder part and the test fixture is shown in Figure 3 .

[0033] Example 2 Figure 5 As shown, this example provides a method for testing the deep residual stress of a large-sized ring cylinder part by neutron diffraction. Use the above test fixture to test the deep residual stress of the large-sized ring cylinder part by neutron diffraction, including the following steps: S1. Define the circumferential, axial, and radial directions of the annular cylinder 7 as the three global test directions - circumferential, axial, and radial. According to the structural dimension parameters of the annular cylinder 7, calculate the theoretical maximum optical path of the annular cylinder 7 in the three test directions of circumferential, axial, and radial. By comparing the theoretical maximum optical path of the annular cylinder in the three test directions with the maximum penetration depth of the neutron beam through the annular cylinder 7, determine whether there are test blind spots in the annular cylinder 7 in these three test directions. For the directions without test blind spots, directly perform neutron diffraction testing. For the directions with test blind spots, proceed to the next judgment. Specifically: The optical path for diffraction testing of the points to be measured on the annular cylinder 7 in a certain test direction is shown in Figure 4 : The intersection point of the neutron incident beam and the neutron diffraction beam is on the point to be measured, the included angle between the neutron incident beam and the neutron diffraction beam is 90°, and the bisector direction of the included angle between the neutron incident beam and the neutron diffraction beam points to the test direction. When measuring the circumferential stress and radial stress of the annular cylinder 7, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two end faces of the annular cylinder 7. When measuring the axial stress of the annular cylinder 7, the plane where the neutron incident beam and the diffraction beam are located is perpendicular to the two end faces of the annular cylinder 7. Among them, the optical path refers to the total penetration distance inside the material when the neutron beam penetrates the workpiece. The theoretical maximum optical path of the annular cylinder in a certain test direction refers to the maximum optical path that can be achieved by measuring all points on the test annular cylinder in a certain test direction.

[0034] In step S1, the calculation expressions for the theoretical maximum optical paths of the annular cylinder 7 in the three test directions are as follows: In the above formula, R is the outer diameter radius of the annular cylinder, B is the wall thickness of the annular cylinder, l is the axial length of the annular cylinder, , , are respectively the theoretical maximum optical paths of the corresponding annular cylinder in the axial, circumferential, and radial directions.

[0035] In this step S1, the method for determining whether there is a test blind spot in a certain direction is as follows: Compare the calculated theoretical maximum optical path of this direction ( / / ) with the maximum penetration depth of the neutron beam through the annular cylinder 7. If the theoretical maximum optical path of a certain direction is greater than , then there is a test blind spot in this direction; otherwise, there is no test blind spot in this direction.

[0036] S2. For the direction on the annular cylinder 7 where there are test blind spots, calculate the actual optical path of each point to be measured in this direction. Compare the actual optical path of each point to be measured in this direction with the maximum penetration depth of the neutron beam through the annular cylinder 7 to determine whether this point to be measured is a test blind spot, and finally determine all the test blind spots of the annular cylinder 7 in the direction with test blind spots. For the non-test blind spots in the direction with test blind spots, directly conduct neutron diffraction testing, and for the non-test blind spots in the direction with test blind spots, make the next judgment. Specifically, the actual optical path refers to the optical path of any point on the annular cylinder in each direction, which is obtained through geometric relationships. The calculation expressions of each point to be measured in the three test directions of circumferential, axial, and radial directions are as follows: In the above formula, i is the point to be measured on the annular cylinder, and X i is the point to be measured i is the shortest distance from the point to be measured to the outer wall of the annular cylinder, and Z i is the point to be measured i is the shortest distance from the point to be measured to the nearer side of the two end faces of the annular cylinder; , , are the actual optical paths of the point to be measured i in the axial, circumferential, and radial directions respectively.

[0037] In this step S2, the method for determining whether each point to be measured is a test blind spot is as follows: Compare the actual optical path of the point to be measured in a certain direction calculated with the maximum penetration depth of the neutron beam of the test spectrometer through the annular cylinder. If the actual optical path of the point to be measured in a certain direction is greater than , then this point to be measured is a test blind spot; otherwise, this point to be measured is a non-test blind spot.

[0038] S3. For the test blind spots in the direction with test blind spots on the annular cylinder 7, judge whether the actual optical path in the circumferential direction meets specific conditions; if it meets specific conditions, adopt the rotation offset method for testing; if it does not meet specific conditions, adopt the drilling assistance method for testing. The specific conditions that need to be met for adopting the rotation offset method are that if there are test blind spots in the circumferential direction of the annular cylinder and the test blind spots meet - ≤0.199 , then it is determined that the test blind spots in this circumferential direction can adopt the rotation offset method to reduce the optical path and make this point to be measured measurable; otherwise, this test blind spot adopts the drilling assistance method to make the measuring point measurable.

[0039] The specific method of rotational offset in the above steps is as follows: First, increase the neutron diffraction wavelength to increase the neutron diffraction angle by α, where 0° < α ≤ 10°, and the angle between the neutron incident beam and the neutron diffraction beam decreases by α / 2. Subsequently, rotate the ring barrel 7 around its axis in a direction away from the neutron optical path by γ, where 0° < γ ≤ 5°, and the optical path of each point to be measured decreases. Among them, the increased amount of diffraction angle α and the workpiece rotation angle γ need to meet the condition that the theoretical maximum optical path after offset is less than the maximum penetration depth of the neutron beam through the ring barrel 7. The increased amount of diffraction angle α and the workpiece rotation angle γ can be determined by the following formula: In the above formula, is the theoretical maximum optical path of the ring barrel in the circumferential direction when the rotational offset method is not used for a certain test blind spot, and is the theoretical maximum optical path of the ring barrel in the circumferential direction after using the rotational offset method for this test blind spot.

[0040] In a specific embodiment, for the points to be measured on the circumferential blind area that cannot be eliminated by the rotational offset method and the blind area points to be measured in other directions, the drilling-assisted method is used for depth measurement; the drilling-assisted method reduces the optical path of the neutron optical path by drilling and thinning the area far from the point to be measured through which the neutron optical path passes. The specific drilling-assisted method is as follows: For a test blind spot in a certain direction, a first hole and a second hole are respectively drilled at the incident and exit positions of the test optical path through the ring barrel 7. The radii of the first hole and the second hole are 5 - 10 mm, and the depths of the first hole and the second hole can be determined by the following formula: In the formula, f 1 and f 2 are the depths of the first hole and the second hole respectively, is the actual optical path of the test blind spot during the test in a certain direction, that is, is , or .

[0041] As Figure 6 shown, the workpiece to be measured in this embodiment is a certain 2219 aluminum alloy ring barrel to be measured, with an outer diameter of 800 mm, a wall thickness of 80 mm, and an axial length of 130 mm. The points to be measured are on the circular cross-sections A and B at distances of 32.5 mm and 65 mm from one end face of the ring barrel. There is a path along the wall thickness of the ring barrel on each of the two circular cross-sections. The points with depths of 5 mm, 20 mm, 40 mm, 60 mm, and 75 mm on the path are the points to be measured. Specifically, see Figure 7 , the path and the positions of the points to be measured on cross-section B are the same as those on cross-section A, that is, the points to be measured B1 - B5 on cross-section B correspond one-to-one with the points to be measured A1 - A5 on cross-section A. The names of the points on the path are named by the serial numbers sorted from small to large according to the cross-section and depth where they are located. For example, A1 refers to the point with the smallest depth (depth of 5 mm) on the radial path of cross-section A.

[0042] According to step S1, substitute the structural dimension parameters of the annular cylinder part R = 400 mm, B = 80 mm, l = 130 mm, and the theoretical maximum optical paths of the annular cylinder part in three orthogonal test directions are obtained as follows: = 266.35 mm, = 183.85 mm, = 240.53 mm. Compared with the maximum penetration depth of the neutron beam of the test spectrometer into the annular cylinder part (for the aluminum alloy of the annular cylinder part in this test spectrometer = 205 mm), it can be seen that there are test blind areas in the radial and circumferential directions of the annular cylinder part.

[0043] According to step S2, substitute the shortest distances X A1 ~ X A5 : 5 mm, 20 mm, 40 mm, 60 mm, 75 mm, and R = 400 mm, and the actual optical paths of each measurement point in the radial direction can be obtained as follows: ~ They are 14.14 mm, 56.57 mm, 113.14 mm, 169.71 mm, and 212.13 mm respectively. Similarly, ~ They are 14.42 mm, 56.56 mm, 113.14 mm, 169.71 mm, and 212.13 mm respectively. By comparing with the maximum penetration depth of the neutron beam of the test spectrometer into the measured part material, it can be seen that the test blind spots in the radial direction of the annular cylinder part are A5 and B5.

[0044] According to step S2, substitute the shortest distances X A1 ~ X A5 : 5 mm, 20 mm, 40 mm, 60 mm, 75 mm, R = 400 mm, and the actual optical paths of each measurement point in the circumferential direction can be obtained as follows: ~ They are 260.34 mm, 245.05 mm, 229.27 mm, 217.00 mm, and 209.43 mm respectively, ~ They are 260.34 mm, 245.05 mm, 229.27 mm, 217.00 mm, and 209.43 mm respectively, compared with the maximum penetration depth of the neutron beam of the test spectrometer into the annular cylinder part By comparison, it can be seen that the test blind spots of the ring cylinder in the circumferential direction are A1, A2, A3, A4, A5, B1, B2, B3, B4, and B5.

[0045] According to step S3, the test blind spots in the circumferential direction X A2 ~ X A5 , X B2 ~ X B5 all satisfy - ≤0.199 , the rotation offset method can be used to reduce the optical path, =245.05mm, =205mm, and calculated through the formula: cos(α / 2 + γ) - sins(α / 2 + γ) ≤ 0.897 Therefore, at this time, the neutron diffraction wavelength is increased to increase the neutron diffraction angle α =10°, the ring cylinder is rotated around the axis by γ = 5° in the direction away from the neutron optical path, and it is calculated that the actual optical paths of the test blind spots A2~A5 and B2~B5 in the circumferential direction after the rotation offset of the ring cylinder are all less than the maximum penetration depth of the neutron beam through the ring cylinder. The above points can be directly measured after the rotation offset.

[0046] According to step S3, for the test blind spots A5 and B5 in the radial direction and the test blind spots A1 and B1 in the circumferential direction, the drilling assistance method needs to be used to reduce the actual optical path when the neutron beam tests the blind spots. For the above test blind spots, a first hole and a second hole are drilled at the incident and exit of the test optical path of the ring cylinder respectively, and the radii of the two holes are 5 - 10mm.

[0047] The test blind spots A5 and B5 in the radial direction are obtained through formula calculation. The depths of the first hole and the second hole f 1 and f 2 satisfy: f 1 + f 2 ≥ 17.13 Therefore, the first hole and the second hole drilled for the test blind spots A5 and B5 in the radial direction are both of the same depth, which is f 1 = 10mm, f 2 = 10mm. Similarly, it is obtained that the first hole and the second hole drilled for the test blind spots A1 and B2 in the circumferential direction are both of the same depth, which is f 3 = 35mm, f 4 = 35mm.

[0048] The neutron diffraction results measured for the test blind spot A5 in the radial direction are shown in Figure 7, it can be seen that the neutron intensity signal is evenly distributed and has a high degree of fitting with the fitted diffraction peak, indicating that the test signal is good when the drilling-assisted method is used for testing.

[0049] The effects of the traditional test method and the test method proposed in the present invention are compared as shown in Table 1 below: Table 1 Comparison of the effects of the test method of the present invention and the traditional typical test scheme As can be seen from Table 1, the method of the present invention can completely cover all the test points required for the deep stress characterization of the ring barrel parts, significantly shortening the machine time consumed by the test and improving the test efficiency.

[0050] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A neutron diffraction testing method for deep residual stress of large-sized ring cylinder parts, characterized in that, Including the following steps: S1. According to the structural dimension parameters of the toroidal part to be tested in the circumferential, axial, and radial test directions, calculate the theoretical maximum optical path of the toroidal part in the three test directions respectively. By comparing the theoretical maximum optical path in the three test directions with the maximum penetration depth of the neutron beam through the toroidal part, determine whether there are test blind spots in the toroidal part in these three test directions. For the direction without test blind spots, directly perform neutron diffraction testing. For the direction with test blind spots, proceed to the next judgment; S2. For the direction with test blind spots on the toroidal part, calculate the actual optical path of each measurement point in this direction. Compare the actual optical path of each measurement point in this direction with the maximum penetration depth of the neutron beam through the toroidal part to determine whether each measurement point is a test blind spot, and finally determine all the test blind spots of the toroidal part in the direction with test blind spots; For the non-test blind spots in the direction with test blind spots, directly perform neutron diffraction testing. For the non-test blind spots in the direction with test blind spots, proceed to the next judgment; S3. For the test blind spots in the direction with test blind spots on the toroidal part, judge whether the actual optical path in the circumferential direction meets specific conditions. If it meets the specific conditions, adopt the rotation offset method for testing. If it does not meet the specific conditions, adopt the drilling assistance method for testing.

2. The deep residual stress neutron diffraction test method according to claim 1, characterized in that In the step S1, the optical path for performing diffraction testing on a certain measurement point of the toroidal part in a certain test direction is as follows: the intersection of the neutron incident beam and the neutron diffraction beam is at the measurement point, the included angle between the neutron incident beam and the neutron diffraction beam is 90°, and the angular bisector direction of the included angle between the neutron incident beam and the neutron diffraction beam points to the test direction of the test optical path. When measuring the circumferential stress and radial stress of the toroidal part, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two end faces of the toroidal part. When measuring the axial stress of the toroidal part, the plane where the neutron incident beam and the diffraction beam are located is perpendicular to the two end faces of the toroidal part.

3. The deep residual stress neutron diffraction test method according to claim 1, characterized in that In the step S1, the calculation expression for the theoretical maximum optical path of the toroidal part in the three test directions is: In the above formula, R is the outer diameter radius of the ring barrel part, B is the wall thickness of the ring barrel part, l is the axial length of the ring barrel part, , , respectively correspond to the theoretical maximum optical path of the ring barrel part in the axial, circumferential and radial directions.

4. The deep residual stress neutron diffraction test method according to claim 3, wherein In the step S1, the method for determining whether there are test blind spots in each direction of the annular cylinder is as follows: compare the theoretically maximum optical path in each direction obtained by calculation with the maximum penetration depth of the neutron beam into the annular cylinder If the theoretically maximum optical path in a certain direction is greater than , then there is a test blind spot in this direction; On the contrary, there is no test blind spot in this direction.

5. The deep residual stress neutron diffraction test method according to claim 2, characterized in that, The calculation expression for the actual optical path of each measurement point in the three test directions in the step S2 is: In the above formula, i is the point to be measured on the ring cylinder, and X i is the point to be measured i is the shortest distance from the point to be measured to the outer wall of the ring cylinder, and Z i is the point to be measured i is the shortest distance from the point to be measured to the nearer side of the two end faces of the ring cylinder; , , are respectively the actual optical paths of the point to be measured i in the axial, circumferential and radial directions.

6. The method for deep residual stress neutron diffraction testing according to claim 5, wherein In the step S2, the method for determining whether each point to be measured is a test blind spot is as follows: compare the actual optical path of each point to be measured in a certain direction calculated with the maximum penetration depth of the sub-beam in the test spectrometer for the ring barrel part If the actual optical path of the point to be measured in a certain direction is greater than , then the point to be measured is a test blind spot; otherwise, the point to be measured is not a test blind spot.

7. The deep residual stress neutron diffraction test method according to claim 6, characterized in that In the step S3, the specific condition is that if there is a test blind spot in the circumferential direction of the ring cylinder part, and the test blind spot satisfies - ≤0.199 , it is determined that the test blind spot can adopt the rotation offset method to reduce the optical path to make the point to be measured measurable; otherwise, the test blind spot adopts the drilling assistance method to make the point to be measured measurable.

8. The deep residual stress neutron diffraction test method according to claim 7, characterized in that The rotation offset method is specifically as follows: First, increase the neutron diffraction wavelength so that the neutron diffraction angle increases by α, and the included angle between the neutron incident beam and the neutron diffraction beam decreases by α / 2, where 0° < α ≤ 10°. Subsequently, rotate the toroidal part around its axis in the direction away from the neutron optical path by γ, where 0° < γ ≤ 5°, and the optical path of each measurement point decreases. The increased amount of the diffraction angle α and the rotation angle γ of the toroidal part need to meet the condition that the theoretical maximum optical path after offset is less than the maximum penetration depth of the neutron beam through the toroidal part. The increased amount of the diffraction angle α and the rotation angle γ of the toroidal part can be determined by the following formula: In the above formula, is the actual optical path of the ring barrel in the circumferential direction after the rotation offset method is adopted for this test blind spot.

9. The deep residual stress neutron diffraction test method according to claim 7, wherein The drilling assistance method is specifically as follows: For the test blind spot in a certain direction, drill a first hole and a second hole at the incident and exit positions of the test optical path through the toroidal part respectively. The radii of the first hole and the second hole are 5 - 10 mm, and the depth relationship between the first hole and the second hole is determined by the following formula: In the above formula, f 1 and f 2 are the depths of the first hole and the second hole respectively, is the actual optical path of the test blind spot when testing in a certain direction.

10. A neutron diffraction testing tooling for deep residual stress of large-sized ring barrel parts, characterized in that, It includes a fixed bottom plate for connecting with a neutron stress spectrometer-like platform, at least two pairs of support roller groups for supporting the cylindrical parts to be tested, and a pressure roller for limiting the cylindrical parts. The at least two pairs of support roller groups are arranged at intervals along the axial direction of the cylindrical parts, and the two support rollers in each pair of support roller groups are symmetrically arranged below the two radial sides of the cylindrical parts. The support roller group includes a support frame connected with the fixed bottom plate and a support roller rotatably installed on the support frame; the pressure roller is arranged inside the cylindrical parts, and both ends of the pressure roller extend to the outside of the cylindrical parts and are respectively fixedly connected with the neutron stress spectrometer-like platform through connecting pieces; the positional relationship between the two support rollers in each pair of support roller groups satisfies the following formula: In the above formula, C is the center distance between the two support rollers in a pair of support roller sets, R is the outer diameter radius of the ring-shaped cylinder part, d is the diameter of the support roller, H is the distance from the rotation axis center of the support roller to the fixed bottom plate, L is the designed distance from the bottommost part of the ring-shaped cylinder part to the fixed bottom plate, usually L ≥ 10 mm; The load-bearing capacity of the support roller satisfies the following formula: In the above formula, is the minimum load-bearing capacity that the support rollers need to meet, M is the mass of the ring-shaped cylinder part, n is the number of support rollers, s is the safety factor, and g is the gravitational constant, taking 9.8 m 2 / s.

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