A neutron diffraction test tool and method for deep residual stress of large-scale annular cylinders

Abstract

The present invention belongs to the technical field of residual stress detection, and in particular relates to a neutron diffraction test fixture and method for deep residual stress of large-scale annular cylindrical parts; wherein the test fixture is composed of a fixed base plate, a pressure roller and multiple pairs of support roller groups, the multiple pairs of support roller groups are arranged at intervals along the axial direction of the annular cylindrical part, the pressure roller is arranged inside the annular cylindrical part along the axial direction, and the two ends of the pressure roller are respectively fixedly connected to the neutron stress spectrometer sample platform. The test method is: before the test, the test blind areas in all directions of the annular cylindrical part and the test blind spots on the blind areas are determined, the non-test blind spots are tested, and then the test blind spots are tested by the rotation offset and drilling auxiliary method innovatively proposed by the present invention. The test fixture has a simple structure and is easy to process. It can achieve stable fixation of the annular cylindrical part and rapid switching of axial strain test points, improve test efficiency, and save precious neutron beam time. The test method solves the problem that the deep residual stress of the annular cylindrical part cannot be measured.

Description

Technical Field

[0001] The invention belongs to the technical field of residual stress detection, and in particular relates to a neutron diffraction testing tool and method for deep residual stress of a large-sized annular cylindrical component. Background Art

[0002] Residual stress refers to the self-equilibrium stress state that persists within a material even when no external load is applied. Various complex residual stresses are introduced during various stages of component manufacturing, such as forging / casting, heat treatment, and machining. Residual stress persists within a component for a long time and, as material is removed or external loads are applied, can cause deformation or damage, seriously threatening the component's normal operation and long-term service life. Accurately assessing and measuring residual stress within components is crucial.

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

[0004] Understanding the deep stresses in components can provide real and effective data for evaluating and extending their service life, supporting component performance improvements. In recent years, there has been a growing demand for neutron diffraction technology to measure deep stresses in components in key national sectors, particularly large-scale structural parts such as annular cylinders, such as transition rings for launch vehicle fuel tanks, cylindrical components for rockets and missiles, deep-sea pressure chambers, high-speed rail bearing rings, nuclear power plant pressure vessels, and piping components.

[0005] When using neutron diffraction technology to measure deep stress in large cylindrical parts, the problems of measuring the stress and measuring it quickly must be solved in advance. Specifically:

[0006] (1) It can be measured: Due to the energy limitation of the neutron source, the depth of neutron penetration into 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 of aluminum alloy is only 205mm. For large-sized or thick-walled annular cylindrical parts, when testing some angles and areas, the neutron light path penetrates the material too deep, exceeding the penetration depth limit, and no signal can be measured.

[0007] (2) Fast measurement: Neutron diffraction testing is expensive and testing machines are scarce (neutron beams need to be provided by spallation neutron sources or reactors, and the total annual operating cost of instruments and supporting equipment is tens of millions of dollars. There are only more than ten devices in the world that can provide neutron diffraction stress measurement). During the test, it is necessary to measure the test points in different directions, different circular cross-sections and different radial paths of the annular cylinder. Therefore, it is necessary to place it sideways and vertically and rotate and move it. When the diffractometer supporting sample platform is placed sideways on the annular cylinder, it is difficult to fix the workpiece and adjust the angle around the axis, resulting in low test efficiency, a great waste of testing machine time, and failure to meet actual needs.

[0008] Currently, in the field of residual stress testing technology, neutron diffraction stress testing of annular cylindrical components, such as oil and gas pipelines and nuclear power pipelines, has been reported. However, there are few reports on adjustable angle fixtures, deep stress field auxiliary testing methods, and test process optimization solutions for such workpieces. Patents related to the present invention, such as invention patent application publication number CN115575426A, disclose a neutron diffraction-based residual stress testing platform and experimental methods for large components. The platform provides a fixture for neutron diffraction testing of disk-like components, but this fixture cannot secure annular cylindrical components without an axis.

[0009] Therefore, it is urgent to propose deep residual stress neutron diffraction testing tooling and methods for large-sized annular cylindrical parts, which will help solve the problems in deep residual stress neutron diffraction testing of large annular cylindrical parts and provide guidance for deep stress testing of workpieces with similar structures such as columns and disks. Summary of the Invention

[0010] The purpose of the present invention is to provide a tool and method for neutron diffraction testing of deep residual stress of large-sized annular cylindrical parts, which is convenient for lateral fixing of workpieces and adjustment of angles around the axis during neutron diffraction testing of annular cylindrical parts, as well as estimation and testing of test blind spots during deep residual stress testing. It can improve test efficiency, solve the problem of blind spots being unable to be tested, and meet the actual needs of neutron diffraction testing of deep residual stress of large annular cylindrical parts.

[0011] To achieve the above object, the present invention provides a neutron diffraction test method for deep residual stress of large-scale annular cylindrical components, comprising the following steps:

[0012] S1. Based on the structural dimension parameters of the annular cylindrical component in the circumferential, axial, and radial directions, respectively, calculate the theoretical maximum optical path of the annular cylindrical component in the three test directions. By comparing the theoretical maximum optical path in the three test directions with the maximum penetration depth of the neutron beam into the annular cylindrical component, determine whether there is a test blind area for the annular cylindrical component in the three test directions; for directions without a test blind area, directly perform the neutron diffraction test; for directions with a test blind area, proceed to the next step of determination;

[0013] S2. For the direction where the test blind spot exists on the annular cylinder, calculate the actual optical path of each test point in the direction, compare the actual optical path of each test point in the direction with the maximum penetration depth of the neutron beam into the annular cylinder, determine whether each test point is a test blind spot, and ultimately determine all test blind spots of the annular cylinder in the direction where the test blind spot exists; for non-test blind spots in the direction of the test blind spot, directly perform neutron diffraction testing; for test blind spots in the direction of the test blind spot, proceed to the next step of determination;

[0014] S3. For a test blind spot on the annular cylinder having a test blind area direction, determine whether its actual optical path in the circumferential direction meets specific conditions; if the specific conditions are met, adopt a rotation offset method for testing; if the specific conditions are not met, adopt a drilling-assisted method for testing.

[0015] Furthermore, in step S1, the optical path for performing a diffraction test on a certain point to be tested on the annular cylinder in a certain test direction is: the intersection of the neutron incident beam and the neutron diffraction beam is at the point to be tested, the angle between the neutron incident beam and the neutron diffraction beam is 90°, and the direction of the angle bisector 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 annular cylinder, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two side end faces of the annular cylinder; when measuring the axial stress of the annular cylinder, the plane where the neutron incident beam and the diffraction beam are located is perpendicular to the two side end faces of the annular cylinder.

[0016] Furthermore, in step S1, the calculation expression of the theoretical maximum optical path of the annular cylinder in the three test directions is:

[0017]

[0018] In the above formula, R is the outer radius of the annular tube, B is the wall thickness of the annular tube, l is the axial length of the annular tube, 、 、 They correspond to the theoretical maximum optical path of the annular cylinder in the axial, circumferential and radial directions respectively.

[0019] Furthermore, in step S1, the method for determining whether there is a test blind area in each direction of the annular cylinder is as follows: the theoretical maximum optical path in each direction obtained by calculation is compared with the maximum penetration depth of the neutron beam into the annular cylinder. For comparison, if the theoretical maximum optical path in 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.

[0020] Furthermore, the actual optical path length calculation expression of each test point in the three test directions in step S2 is:

[0021]

[0022] In the above formula, i is the point to be measured on the annular cylinder, X i is the shortest distance between the measured point i and the outer wall of the annular cylinder, Z i The shortest distance between the measured point i and the two end faces of the annular cylindrical component; 、 、 are the actual optical path lengths of the measured point i in the axial, circumferential and radial directions respectively.

[0023] Furthermore, in step S2, the method for determining whether each test point is a test blind spot is as follows: the actual optical path of each test point in a certain direction calculated is compared with the maximum penetration depth of the neutron beam of the test spectrometer into the annular cylinder. By contrast, if the actual optical path of the measured point in a certain direction is greater than , then the point to be tested is a test blind spot; otherwise, the point to be tested is a non-test blind spot.

[0024] Furthermore, in step S3, the specific condition is: if the annular cylinder has a test blind spot in the circumferential direction, and the test blind spot satisfies - ≤0.199 , then the test blind spot can be determined by the rotation offset method to reduce the optical path, so that the test point can be measured; otherwise, the test blind spot can be measured by the drilling auxiliary method.

[0025] Furthermore, the rotation offset method is specifically as follows:

[0026] First, the neutron diffraction wavelength is increased so that the neutron diffraction angle increases by α, and the angle between the incident neutron beam and the diffracted neutron beam decreases by α / 2, where 0°<α≤10°. Then, the annular cylinder is rotated about its axis by γ, where 0°<γ≤5°, away from the neutron optical path, to reduce the optical path of each point to be measured. The diffraction angle increase α and the annular cylinder rotation angle γ must satisfy the following condition: the theoretical maximum optical path after the offset is less than the maximum penetration depth of the neutron beam into the annular cylinder. The diffraction angle increase α and the annular cylinder rotation angle γ can be determined by the following formula:

[0027]

[0028] In the above formula, The actual optical path of the annular cylinder in the circumferential direction after the rotation offset method is used for the test blind spot.

[0029] Furthermore, the drilling assistance method is specifically as follows:

[0030] For a test blind spot in a certain direction, a first hole and a second hole are drilled at the entrance and exit ring cylinders of the test light path, respectively. The radius of the first hole and the second hole is 5-10 mm, and the depth relationship between the first hole and the second hole is determined by the following formula:

[0031]

[0032] In the above formula, f1 and f2 are the depths of the first hole and the second hole respectively. It is the actual optical distance of the blind spot when testing in a certain direction.

[0033] The present invention also provides a deep residual stress neutron diffraction test tool for large-scale annular cylindrical parts, comprising a fixed base plate for connecting to a neutron stress spectrometer sample platform, at least two pairs of support roller groups for supporting the annular cylindrical part to be tested, and a pressure roller for limiting the annular cylindrical part, wherein the at least two pairs of support roller groups are arranged at intervals along the axial direction of the annular cylindrical part, and the two support roller groups in each pair of support roller groups are symmetrically arranged below the radial sides of the annular cylindrical part, the support roller group comprises a support frame connected to the fixed base plate and support rollers rotatably mounted on the support frame; the pressure rollers are arranged in the annular cylindrical part, and the two ends of the pressure rollers extend to the outside of the annular cylindrical part and are fixedly connected to the neutron stress spectrometer sample platform through connecting members respectively; the positional relationship of the two support rollers in each pair of support roller groups satisfies the following formula:

[0034]

[0035] In the above formula, C is the axis center distance between the two support rollers in a pair of support rollers, R is the outer radius of the annular member, d is the diameter of the support roller, H is the distance between the rotation axis of the support roller and the fixed base plate, and L is the design distance between the bottom of the annular member and the fixed base plate, usually L ≥ 10mm;

[0036] The load-bearing capacity of the support roller satisfies the following formula:

[0037]

[0038] In the above formula, is the minimum load-bearing capacity that the support roller must meet, M is the mass of the ring cylinder, n is the number of support rollers, s is the safety factor, and g is the gravity constant, which is 9.8m 2 / s.

[0039] In the above-mentioned neutron diffraction test tooling, the processing flatness of the fixed base plate is less than 0.1mm; the pressure roller is a round rod-shaped structure with open slots at both ends of the pressure roller; the processing straightness error of the support roller fixing hole on the support frame is less than 0.1mm / m, and the support frame is connected to the fixed base plate by at least two bolts.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] (1) The present invention proposes a deep residual stress neutron diffraction test method for large-sized annular cylinders. Among them, the invention innovatively proposes two methods, namely the rotation offset method and the drilling auxiliary method, which can significantly reduce the optical path and solve the problem that the deep stress of large-sized and thick-walled annular cylinders cannot be measured. It provides guidance for solving the problem of insufficient penetration of deep stress neutron diffraction test of similar workpieces.

[0042] (2) The present invention proposes a deep residual stress neutron diffraction test fixture for large-sized annular cylinders, which has a simple structure, is stable and reliable, and is easy to process. It helps to fix the annular cylinders and switch the test points when measuring axial stress, thereby improving the test efficiency and saving precious neutron beam time.

[0043] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present invention, but do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0045] Figure 1 This is a schematic diagram of the three-dimensional structure of a deep stress neutron diffraction test tool for a large-sized annular cylinder according to the present invention;

[0046] Figure 2 This is a side view schematic diagram of the structure of a deep stress neutron diffraction test tool for a large-sized annular cylinder according to the present invention;

[0047] Figure 3 This is a test diagram of a large-sized annular cylindrical component using the test fixture of the present invention in Example 1 of the present invention;

[0048] Figure 4 The present invention provides a diffraction test optical path for a large-sized annular cylindrical component at a point to be tested in three test directions; wherein: (a) is a diffraction test optical path diagram in the radial direction, (b) is a diffraction test optical path diagram in the tangential direction, and (c) is a diffraction test optical path diagram in the circumferential direction;

[0049] Figure 5 This is a flow chart of a neutron diffraction testing method for deep residual stress in a large-sized annular cylindrical component according to the present invention;

[0050] Figure 6Schematic diagram of the deep residual stress measurement points of a large-sized annular cylindrical component according to Example 2 of the present invention; wherein: (a) is the location of section A and section B on the annular cylindrical component, and (b) is a schematic diagram of the structure of section A;

[0051] Figure 7 This is the signal result of the neutron diffraction test using the drilling-assisted method in Example 2 of the present invention;

[0052] Among them, 1-fixed bottom plate; 2-pressing roller; 3-support frame; 4-support roller; 5-connecting piece; 6-neutron stress spectrometer sample platform; 7-ring cylinder piece. DETAILED DESCRIPTION

[0053] The present invention will be described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention.

[0054] Example 1

[0055] See Figure 1 and Figure 2 As shown, this embodiment provides a deep residual stress neutron diffraction test tool for a large-scale annular cylindrical component, comprising a fixed base plate 1 for connecting to a neutron stress spectrometer sample platform 6, at least two pairs of support roller groups for supporting the annular cylindrical component 7, and a pressure roller 2 for limiting the annular cylindrical component 7. The at least two pairs of support roller groups are arranged at intervals along the axial direction of the annular cylindrical component 7, and the two support roller groups in each pair of support roller groups are symmetrically arranged below the radial sides of the annular cylindrical component 7. The support roller group includes a support frame 3 connected to the fixed base plate 1 and a support roller 4 rotatably mounted on the support frame 3; in this structural arrangement, the fixed base plate 1 is a plate with a plurality of through holes, the bottom of which is fixedly connected to the neutron stress spectrometer sample platform 6, and a pressure roller and a support pad are arranged above it; the pressure roller 2 is a round rod-shaped structure arranged in the annular cylindrical component 7, and there are open slots at both ends of the pressure roller 2, and the two ends of the pressure roller 2 extend to the outside of the annular cylindrical component 7 and are fixedly connected to the neutron stress spectrometer sample platform 6 through a connecting member 5.

[0056] Based on 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, which is used to determine the relative positions of the two support rollers on the fixed base plate:

[0057]

[0058] In the above formula, C is the axial center distance between the two support rollers in a pair of support rollers, R is the outer radius of the annular member, d is the diameter of the support roller, H is the distance between the rotation axis of the support roller and the fixed base plate, and L is the designed distance between the bottom of the annular member and the fixed base plate, usually L ≥ 10mm.

[0059] In this example, the test piece (annular cylinder) is a 7050 aluminum alloy shell segment with an outer diameter of 655 mm, an inner diameter of 585 mm, a length of 560 mm, and a weight of approximately 106.89 kg. Substituting the outer radius of the annular cylinder R = 327.5 mm, the diameter of the support roller d = 58 mm, the distance H = 45 mm between the rotation axis of the support roller and the fixed base plate, and the minimum design distance L = 10 mm between the bottom of the annular cylinder and the fixed base plate, the center distance between the two support rollers should be C max =407.6mm, according to the actual selection C=300mm, L=40.9mm.

[0060] Based on the force relationship, the load-bearing capacity selection calculation formula of the support roller 4 is derived to determine the support roller model that meets the load-bearing capacity:

[0061]

[0062] In the above formula, is the minimum load-bearing capacity that the support roller must meet, in N, M is the total mass of the test piece, n is the number of support rollers, and s is the safety factor, which is usually 1.5~2.

[0063] The mass of the ring cylinder is M = 106.89 kg, g = 9.8 m / s 2 , C=300mm, R=327.5mm, d=58mm, s=1.5 are substituted into the above formula to obtain ≥1060.4856N / n, 4 support rollers with a load capacity of more than 50kg are selected and placed in pairs on both sides of the ring cylinder.

[0064] In a specific embodiment, in order to ensure the measurement effect, the processing flatness of the fixed base plate 1 is less than 0.1 mm; the processing straightness error of the support roller fixing hole on the support frame 3 is less than 0.1 mm / m, and when the fixed base plate is connected to the support roller, the number of bolts arranged along the axial direction of the support roller is greater than 2.

[0065] During the test, first fasten the fixed base plate 1 of the test fixture to the sample platform with bolts, then hoist the annular cylinder between the support rollers. After it is stably supported, adjust the position of the annular cylinder by rotation and translation so that the intersection of the diffraction beam is accurately positioned at the test point. Then install the support rollers to press and fix the annular cylinder 7. After confirming that the positioning is correct, the test can be carried out. During the test, the specific placement of the annular cylinder and the test fixture is shown in Figure 3 .

[0066] Example 2

[0067] Figure 5As shown, this embodiment provides a method for testing deep residual stress of a large-sized annular cylindrical component by neutron diffraction. The method uses the above-mentioned testing tool to test the deep residual stress of a large-sized annular cylindrical component by neutron diffraction, and includes the following steps:

[0068] 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 size 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 into the annular cylinder 7, determine whether there is a test blind area for the annular cylinder 7 in these three test directions; for directions where there is no test blind area, directly perform neutron diffraction test; for directions where there is a test blind area, perform the next step of judgment. Specifically: For the optical path of the diffraction test of the test point on the annular cylinder 7 in a certain test direction, refer to Figure 4 : The intersection of the neutron incident beam and the neutron diffraction beam is at the point to be tested, the angle between the neutron incident beam and the neutron diffraction beam is 90°, and the direction of the angle bisector 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 direction of the annular cylinder 7, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two side end faces of the annular cylinder 7, and 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 side end faces of the annular cylinder 7. Among them, the optical path refers to the total penetration distance of the neutron light beam inside the material when it 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 reached for all points on the test annular cylinder in a certain test direction.

[0069] In step S1, the calculation expression of the theoretical maximum optical path of the annular cylinder 7 in the three test directions is:

[0070]

[0071] In the above formula, R is the outer radius of the annular tube, B is the wall thickness of the annular tube, l is the axial length of the annular tube, 、 、 They are the theoretical maximum optical path of the corresponding annular cylinder in the axial, circumferential and radial directions respectively.

[0072] In step S1, the method for determining whether there is a test blind area in a certain direction is: the calculated theoretical maximum optical path in the direction ( / / ) and the maximum penetration depth of the neutron beam to the ring cylinder 7 For comparison, if the theoretical maximum optical path in 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.

[0073] S2. For the direction where there is a test blind spot on the annular cylinder 7, calculate the actual optical path of each test point in the direction, compare the actual optical path of each test point in the direction with the maximum penetration depth of the neutron beam into the annular cylinder 7, determine whether the test point is a test blind spot, and finally determine all the test blind spots of the annular cylinder 7 in the direction where there is a test blind spot; for non-test blind spots in the direction of the test blind spot, directly perform neutron diffraction test, and for test blind spots in the direction of the test blind spot, perform the next step of 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 test point in the three test directions of circumferential, axial and radial directions are:

[0074]

[0075] In the above formula, i is the point to be measured on the annular cylinder, X i is the shortest distance between the measured point i and the outer wall of the annular cylinder, Z i The shortest distance between the measured point i and the two end faces of the annular cylindrical component; 、 、 are the actual optical path lengths of the measured point i in the axial, circumferential and radial directions respectively.

[0076] In step S2, the method for determining whether each test point is a test blind spot is as follows: the actual optical path of the test point in a certain direction calculated is compared with the maximum penetration depth of the neutron beam of the test spectrometer into the ring cylinder. By contrast, if the actual optical path of the measured point in a certain direction is greater than , then the point to be tested is a test blind spot; otherwise, the point to be tested is a non-test blind spot.

[0077] S3, for the test blind spot on the annular cylinder 7, determine whether its actual optical path in the circumferential direction meets the specific conditions; if the specific conditions are met, the rotation offset method is used for testing; if the specific conditions are not met, the drilling auxiliary method is used for testing. The specific conditions that need to be met by the rotation offset method are: if the annular cylinder has a test blind spot in the circumferential direction, and the test blind spot meets - ≤0.199 , then the test blind spot on the circumference can be determined by using the rotation offset method to reduce the optical path so that the test point can be measured; otherwise, the test blind spot can be measured by using the drilling auxiliary method to make the measuring point measurable.

[0078] The rotational offset method in the above steps is specifically as follows: first, increase the neutron diffraction wavelength so that the neutron diffraction angle increases by α, and 0°<α≤10°, and the angle between the neutron incident beam and the neutron diffraction beam decreases by α / 2; then, rotate the annular cylinder 7 around its axis by γ in a direction away from the neutron optical path, and 0°<γ≤5°, so that the optical path of each point to be measured decreases; wherein, the diffraction angle increase α and the workpiece rotation angle γ must meet the condition: the theoretical maximum optical path after offset is less than the maximum penetration depth of the neutron beam into the annular cylinder 7. The diffraction angle increase α and the workpiece rotation angle γ can be determined by the following formula:

[0079]

[0080] In the above formula, is the theoretical maximum optical path of the annular cylinder in the circumferential direction when the rotation offset method is not used in a certain test blind spot. The theoretical maximum optical path of the annular cylinder in the circumferential direction after the rotation offset method is used for the test blind spot.

[0081] In a specific embodiment, for the test points in the circumferential blind zone that cannot be eliminated by the rotation offset method and the test points in the blind zone in other directions, the drilling-assisted method is used to measure the depth; the drilling-assisted method is to reduce the optical path of the neutron light path by drilling and thinning the area far away from the test point through which the neutron light path passes. The drilling-assisted method is specifically as follows:

[0082] For a test blind spot in a certain direction, a first hole and a second hole are drilled at the incident and exit ring cylinder 7 of the test light path respectively. The radius of the first hole and the second hole is 5-10 mm. The depth of the first hole and the second hole can be determined by the following formula:

[0083]

[0084] Where f1 and f2 are the depths of the first hole and the second hole, respectively. It is the actual optical distance of the blind spot when testing in a certain direction, that is for 、 or .

[0085] like Figure 6 As shown, the test piece in this embodiment is a 2219 aluminum alloy ring cylinder to be tested, with an outer diameter of 800mm, a wall thickness of 80mm, and an axial length of 130mm. The test points are on the circular sections A and B at a distance of 32.5mm and 65mm from one end face of the ring cylinder. There is a path along the wall thickness of the ring cylinder on each of the two circular sections. The points with depths of 5mm, 20mm, 40mm, 60mm, and 75mm on the path are the test points. For details, see Figure 7The path and test point locations on Section B are identical to those on Section A. That is, test points B1-B5 on Screenshot B correspond one-to-one to test points A1-A5 on Section A. The points on the path are named based on their depths, sorted from smallest to largest. For example, A1 represents the point with the smallest depth (5mm) on the radial path of Section A.

[0086] According to step S1, the structural dimension parameters of the annular cylinder R = 400 mm, B = 80 mm, and l = 130 mm are substituted to obtain the theoretical maximum optical path of the annular cylinder in three orthogonal test directions: =266.35mm, =183.85mm, =240.53mm, which is the maximum penetration depth of the neutron beam of the test spectrometer into the annular cylinder (This test spectrometer is used for the aluminum alloy of the ring cylinder =205mm), it can be seen that the annular cylinder has test blind areas in the radial and circumferential directions.

[0087] According to step S2, the shortest distance X between each point to be measured and the outer wall is A1 ~X A5 : 5mm, 20mm, 40mm, 60mm, 75mm and R=400mm are substituted, and the actual optical path length of each measured point in the radial direction can be obtained as follows: ~ They are 14.14mm, 56.57mm, 113.14mm, 169.71mm, and 212.13mm respectively. ~ They are 14.42mm, 56.56mm, 113.14mm, 169.71mm and 212.13mm respectively. The maximum penetration depth of the neutron beam of the test spectrometer is the maximum penetration depth of the test piece material. By comparison, it can be seen that the radial test blind spots of the annular cylinder are A5 and B5.

[0088] According to step S2, the shortest distance X between each point to be measured and the outer wall is A1 ~X A5 : 5mm, 20mm, 40mm, 60mm, 75mm, R = 400mm, and the actual optical path of each test point in the circumferential direction can be obtained as follows: ~ They are 260.34mm, 245.05mm, 229.27mm, 217.00mm and 209.43mm respectively. ~ The maximum penetration depths of the neutron beam of the test spectrometer into the annular cylinder are 260.34mm, 245.05mm, 229.27mm, 217.00mm and 209.43mm respectively. By comparison, it can be seen that the test blind spots of the annular cylinder in the circumferential direction are A1, A2, A3, A4, A5, B1, B2, B3, B4, and B5.

[0089] According to step S3, the blind spot X is tested circumferentially. A2 ~X A5 , X B2 ~X B5 All satisfied - ≤0.199 , the optical path can be reduced by using the rotation offset method. =245.05mm, =205mm, calculated by the formula:

[0090] cos(α / 2+γ)-sins(α / 2+γ)≤0.897

[0091] Therefore, at this time, the neutron diffraction wavelength is increased to increase the neutron diffraction angle by α=10°, and the annular cylinder is rotated around the axis by γ=5° in the direction away from the neutron optical path. The actual optical path of the circumferential test blind spots A2~A5 and B2~B5 after the annular cylinder is rotated and offset is calculated to be less than the maximum penetration depth of the neutron beam into the annular cylinder. The above points can be directly measured after the rotation and offset.

[0092] According to step S3, the radial blind spots A5 and B5 and the circumferential blind spots A1 and B1 require a drilling-assisted method to reduce the actual optical path length during neutron beam testing. For these blind spots, a first hole and a second hole are drilled at the entrance and exit rings of the test beam path, respectively. The radii of these holes are 5-10 mm.

[0093] The radial test blind spots A5 and B5 are calculated using the formula, and the depths f1 and f2 of the first hole and the second hole satisfy:

[0094] f1+f2≥17.13

[0095] Therefore, the first and second holes drilled at the radial test blind spots A5 and B5 have the same depth, f1 = 10mm and f2 = 10mm. Similarly, the first and second holes drilled at the circumferential test blind spots A1 and B2 have the same depth, f3 = 35mm and f4 = 35mm.

[0096] The neutron diffraction results measured at the radial blind spot A5 are shown in Figure 7 It can be seen that the neutron intensity signal is evenly distributed and has a high degree of fit with the fitted diffraction peak. This shows that the test signal is good when the drilling-assisted method is used for testing.

[0097] The comparison of the results of the traditional test method and the test method proposed by the present invention is shown in Table 1 below:

[0098] Table 1 Comparison of the test method of the present invention and the traditional typical test scheme

[0099]

[0100] As can be seen from Table 1, the method of the present invention can completely cover all test points required for the deep stress characterization of the annular cylindrical component, significantly shorten the test time consumption, and improve the test efficiency.

[0101] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A neutron diffraction test method for deep residual stress of large-scale annular cylindrical parts, characterized in that: The following steps are involved: S1. Based on the structural dimension parameters of the annular cylindrical component in the circumferential, axial, and radial directions, respectively, calculate the theoretical maximum optical path of the annular cylindrical component in the three test directions. By comparing the theoretical maximum optical path in the three test directions with the maximum penetration depth of the neutron beam into the annular cylindrical component, determine whether there is a test blind area for the annular cylindrical component in the three test directions; for directions without a test blind area, directly perform the neutron diffraction test; for directions with a test blind area, proceed to the next step of determination; S2. For the direction where the test blind spot exists on the annular cylinder, calculate the actual optical path of each test point in that direction, compare the actual optical path of each test point in that direction with the maximum penetration depth of the neutron beam into the annular cylinder, determine whether each test point is a test blind spot, and ultimately determine all test blind spots of the annular cylinder in the direction where the test blind spot exists; For non-test blind spots in the test blind area direction, neutron diffraction test is directly performed; for test blind spots in the test blind area direction, the next step of judgment is performed; S3. For a test blind spot on the annular cylindrical member having a test blind area direction, determine whether its actual optical path in the circumferential direction meets specific conditions; if the specific conditions are met, perform a test using a rotation offset method; if the specific conditions are not met, perform a test using a drilling-assisted method; The rotational offset method is specifically as follows: first, the neutron diffraction wavelength is increased so that the neutron diffraction angle increases by α, and the angle between the neutron incident beam and the neutron diffraction beam decreases by α / 2, where 0°<α≤10°; then, the annular cylinder is rotated about its axis by γ, where 0°<γ≤5°, in a direction away from the neutron optical path, so that the optical path of each point to be measured decreases; the diffraction angle increase α and the annular cylinder rotation angle γ must meet the condition that the theoretical maximum optical path after the offset is less than the maximum penetration depth of the neutron beam into the annular cylinder; the diffraction angle increase α and the annular cylinder rotation angle γ can be determined by the following formula: In the above formula, The actual optical path of the annular cylinder in the circumferential direction after the rotation offset method is used for the test blind spot; The drilling-assisted method is specifically as follows: for a test blind spot in a certain direction, a first hole and a second hole are drilled at the incident and exit ring cylinders of the test light path, respectively. The radius of the first hole and the second hole is 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, f1 and f2 are the depths of the first hole and the second hole respectively. It is the actual optical distance of the blind spot when testing in a certain direction.

2. The deep residual stress neutron diffraction testing method according to claim 1, characterized in that: In the step S1, the optical path for performing a diffraction test on a certain point to be tested on the annular cylinder in a certain test direction is: the intersection of the neutron incident beam and the neutron diffraction beam is at the point to be tested, the angle between the neutron incident beam and the neutron diffraction beam is 90°, and the direction of the angle bisector 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, the plane where the neutron incident beam and the diffraction beam are located is parallel to the two side end faces of the annular cylinder; when measuring the axial stress of the annular cylinder, the plane where the neutron incident beam and the diffraction beam are located is perpendicular to the two side end faces of the annular cylinder.

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

4. The deep residual stress neutron diffraction testing method according to claim 3, characterized in that: In step S1, the method for determining whether there is a test blind area in each direction of the annular cylinder is as follows: the calculated theoretical maximum optical path in each direction is compared with the maximum penetration depth of the neutron beam into the annular cylinder. For comparison, if the theoretical maximum optical path in a certain direction is greater than , then there is a test blind area in this direction; Otherwise, there is no test blind area in this direction.

5. The deep residual stress neutron diffraction testing method according to claim 2, characterized in that: The actual optical path length calculation expression of each test point in the three test directions in step S2 is: In the above formula, i is the point to be measured on the annular cylinder, X i is the shortest distance between the measured point i and the outer wall of the annular cylinder, Z i The shortest distance between the measured point i and the two end faces of the annular cylindrical component; 、 、 are the actual optical path lengths of the measured point i in the axial, circumferential and radial directions respectively.

6. The deep residual stress neutron diffraction testing method according to claim 5, characterized in that: In step S2, the method for determining whether each test point is a test blind spot is as follows: the actual optical path of each test point in a certain direction calculated is compared with the maximum penetration depth of the neutron beam of the test spectrometer into the annular cylinder. By contrast, if the actual optical path of the measured point in a certain direction is greater than , then the point to be tested is a test blind spot; otherwise, the point to be tested is a non-test blind spot.

7. The deep residual stress neutron diffraction testing method according to claim 6, characterized in that: In step S3, the specific condition is: if the annular cylinder has a test blind spot in the circumferential direction, and the test blind spot satisfies - ≤0.199 , then the test blind spot can be determined by the rotation offset method to reduce the optical path, so that the test point can be measured; otherwise, the test blind spot can be measured by the drilling auxiliary method.

8. The deep residual stress neutron diffraction testing method according to any one of claims 1 to 7, characterized in that: A large-scale annular component deep residual stress neutron diffraction test fixture is used for testing. The test fixture includes a fixed base plate for connecting to the neutron stress spectrometer sample platform, at least two pairs of support roller groups for supporting the annular component to be tested, and a pressure roller for limiting the annular component. The at least two pairs of support roller groups are arranged at intervals along the axial direction of the annular component, and the two support roller groups in each pair of support roller groups are symmetrically arranged below the radial sides of the annular component. The support roller group includes a support frame connected to the fixed base plate and support rollers rotatably mounted on the support frame; the pressure rollers are arranged in the annular component, and the two ends of the pressure rollers extend to the outside of the annular component and are fixedly connected to the neutron stress spectrometer sample platform through connecting pieces respectively; the positional relationship of the two support rollers in each pair of support roller groups satisfies the following formula: In the above formula, C is the axis center distance between the two support rollers in a pair of support rollers, R is the outer radius of the annular member, d is the diameter of the support roller, H is the distance between the rotation axis of the support roller and the fixed base plate, and L is the design distance between the bottom of the annular member and the fixed base 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 must meet, M is the mass of the ring cylinder, n is the number of support rollers, s is the safety factor, and g is the gravity constant, which is 9.8m 2 / s.

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