阅读说明：本技术 一种空心叶片残芯中子检测灵敏度的参考线确定方法 (Reference line determination method for hollow blade residual core neutron detection sensitivity ) 是由 高祥熙 陈木子 王倩妮 何方成 贾新云 于 2020-11-03 设计创作，主要内容包括：本发明公开了一种空心叶片残芯中子检测灵敏度的参考线确定方法。该方法应用反应堆中子检测系统和对比试样,对比试样表面加工有含宽度和深度相同的两条平行长槽,其中一条长槽形成有填充型芯。包括步骤：(1)对比试样在反应堆中子检测系统中透照成像；(2)获取透照图像中等间距线的厚度和灰度；(3)绘制离散点图和参考线,照厚度T与对比度C之间线性关系。该方法避免了铸造实物叶片和脱芯工艺的繁琐步骤,便于得到不同材料厚度下、不同掺杂含量的残芯对比度灵敏度,该灵敏度接近真实的残芯检测灵敏度,同时还有利于定量残芯的细节检测能力,可实现残芯中子检测检测前的定量灵敏度的参考目的。(The invention discloses a reference line determining method for detecting sensitivity of hollow blade residual core neutrons. The method applies a reactor neutron detection system and a comparison sample, wherein the surface of the comparison sample is processed with two parallel long grooves with the same width and depth, and one long groove is formed with a filling core. The method comprises the following steps: (1) transillumination imaging of the contrast sample in a reactor neutron detection system; (2) acquiring the thickness and the gray scale of equidistant lines in a transillumination image; (3) and drawing a discrete point diagram and a reference line according to the linear relation between the thickness T and the contrast C. The method avoids the complex steps of casting the physical blade and a depoling process, is convenient for obtaining the residual core contrast sensitivity with different material thicknesses and different doping contents, is close to the real residual core detection sensitivity, is beneficial to quantifying the detail detection capability of the residual core, and can realize the reference purpose of the quantitative sensitivity before the detection of the residual core neutron.)

1. A reference line determining method for hollow blade residual core neutron detection sensitivity is characterized by comprising the following steps: the method is characterized in that a reactor neutron detection system (1) and a comparison sample (2) are applied;

the reactor neutron detection system can realize transillumination of the hollow blade and generate a gray level image of the transillumination of the blade, the gray level image can be used for developing a residual core in a cavity of the blade, and the gray level of the residual core is different from that of a blade material;

the material of the comparison sample is the same as that of the hollow blade, the thickness of the comparison sample is linearly increased from one end to the other end in the transverse direction, the thickness of the comparison sample is consistent in the longitudinal direction, the minimum thickness in the transverse direction is not more than the minimum wall thickness of the hollow blade, and the maximum thickness in the transverse direction is not less than the maximum wall thickness of the hollow blade;

a first elongated slot and a second elongated slot are arranged in the transverse direction of the comparison sample, the first elongated slot is parallel to the second elongated slot, and the depth and the width of the elongated slots are manufactured according to the acceptance requirements of the residual core of the blade;

the first long groove is a hollow groove, a filling core is formed in the second long groove, and molding slurry of the filling core is mixed with Gd₂O₃The residual core forming slurry;

the method comprises the following steps:

step one, comparing the sample transillumination

Placing a contrast sample in a reactor neutron detection system, and generating a transillumination image through neutron source irradiation;

step two, obtaining the thickness and the gray scale of the equidistant line

On the transillumination image of the contrast sample, a plurality of equidistant lines are taken along the transverse direction, and the image gray value H in the first long groove and the image gray value H in the second long groove at the longitudinal position corresponding to each equidistant line are obtained_C；

Step three, drawing a discrete point diagram

Establishing an XY plane coordinate system, wherein an X axis is a thickness value, a Y axis is a contrast value, discrete points are marked in the XY plane coordinate system, each discrete point corresponds to an equidistant line, an X value of each discrete point is the thickness of a contrast sample corresponding to the equidistant line, a Y value of each discrete point is the contrast of the corresponding equidistant line, and a calculation formula of the contrast is as follows: contrast C ═ H_C－H|/H；

Step four, drawing a reference straight line

And fitting to obtain a straight line through the discrete points marked in the third step, wherein the straight line is used as a reference line which represents the linear relation between the transillumination thickness T and the contrast C.

2. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: and two ends of the contrast sample in the transverse direction form edges with equal thickness, wherein the thickness of one end is the minimum thickness, and the thickness of the other end is the maximum thickness.

3. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: the comparative sample had a minimum thickness in the transverse direction of not more than 1mm and a maximum thickness in the transverse direction of not less than 6 mm.

4. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: the first long groove and the second long groove are both U-shaped cross-section grooves.

5. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: gd is filled and mixed in the second long groove₂O₃The ceramic core slurry is sintered and solidified at high temperature to obtain the filling core.

6. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: the matrix material of the residual core is silicon oxide or aluminum oxide.

7. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 1, wherein: the number of the equidistant lines is at least 10.

8. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 5, wherein: and removing the core material overflowing from the second long groove in a machining mode after solidification.

9. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 5, wherein: the filling degree of the filling core in the second long groove is 100%.

10. The method for determining the reference line of the hollow blade core-remnant neutron detection sensitivity according to claim 5, wherein: the Gd₂O₃Is powder with purity up to 99.9%Above, Gd₂O₃The mass ratio of the powder to the ceramic core slurry is 0.015-0.03.

Technical Field

The invention relates to the technical field of nondestructive testing, and particularly provides a reference line determination method for hollow blade residual core neutron detection sensitivity.

Background

Turbine blades for aircraft engines are usually precision cast from high temperature alloys, and the quality of the turbine blades is related to the performance of the whole engine and more to the safety of the aircraft. Because the temperature of the gas generated by the engine combustion chamber is too high, the existing turbine blades are hollow and the blades are cooled by continuously introducing low-temperature air into the turbine blades. The internal cavity of the turbine blade is fine and complex, the internal space is occupied by the ceramic core during casting, the core is generally removed through a core removing process, but the core removing process is difficult to ensure the complete removal of the ceramic core, the residual core in the cavity not only can influence the normal flow of cooling air flow in the working process of the hollow blade, the cooling effect is reduced, but also air film holes (hundreds of which have the diameter of 0.3mm to 0.5mm) for cooling on the blade body can be blocked, the local ultra-high temperature and early failure of the blade are caused, huge potential safety hazards are brought to an engine, and therefore whether the residual core exists inside the hollow blade or not must be detected by adopting related means.

Conventional X-rays are difficult to perform effectively due to the low density of the core. At present, the common practice at home and abroad is to add a small amount of elements (such as Gd) with very large neutron cross section into a core material to mark the core, and neutron detection is adopted to realize high-sensitivity detection of the residual core. In general, the more the element with a large neutron cross section is added, the higher the detection sensitivity of the remnant core is, and the amount of 0.5% to 6% is usually preferable. Labeling is generally accomplished by two methods: soaking and doping. The soaking method is to remove the core of the possible residual core in Gd (NO) from the leaves₃)₃Soaking in the solution to enable enough contrast agent to be absorbed by the residual core, and then performing neutron detection on the blade, wherein the method can be influenced by a soaking process and risks of over-washing after soaking, and has low reliability; the doping method is to dope Gd₂O₃The powder is directly doped into the ceramic core material, and the neutron detection can be directly carried out after the core of the blade is removed.

For neutron sources, the reactor contains gamma rays, scattered radiation and electricity in addition to producing efficient thermal neutronsSub-equal penalties can increase background noise. Therefore, to ensure good image quality, the rate of thermal neutrons is required to be at least 10 for the detection of the residual core⁵n/cm²S. In addition, in the imaging process, the film imaging is widely applied and has better detection capability, and the digital imaging is lower than the film imaging in terms of spatial resolution and detail detection capability, but the method has high efficiency, is convenient and fast in image processing and has better application prospect.

In conclusion, the neutron detection of the hollow blade residual core is influenced by various factors such as the size of the core, the doping content, a neutron source, an imaging system and the like, and the detection sensitivity must be verified before the detection. At present, two methods are generally adopted, and foreign patents (3, 617, 747) provide a method for verifying neutron detection sensitivity of a residual core, wherein the method is based on decoring of a cast blade to obtain a residual core with the minimum detection amount of 0.5mg, but the size of the residual core obtained by a decoring process has uncertainty, so that quantitative residual cores with smaller sizes cannot be obtained, and detection sensitivity under different material thicknesses is not convenient to obtain; the other method is to make a step contrast sample, and to add doped ceramic core powder into holes with different depths to obtain contrast sensitivity with different doping contents under different material thicknesses.

Disclosure of Invention

The purpose of the invention is as follows: in view of the above, the invention provides a method for determining a reference line of hollow blade residual core neutron detection sensitivity, which establishes a linear relationship between transillumination thickness and contrast by comparing neutron transillumination images of a sample, is not only convenient for realizing residual core contrast sensitivity of different material thicknesses and different doping contents, but also beneficial for quantifying the detail detection capability of residual cores, and is used for verifying reference indexes of the residual core quantitative sensitivity before neutron detection of a neutron detection system and a hollow blade.

The technical scheme of the invention is as follows: a reference line determination method for hollow blade residual core neutron detection sensitivity is provided, wherein a reactor neutron detection system (1) and a comparison sample (2) are applied in the method;

the reactor neutron detection system can realize transillumination of the hollow blade and generate a gray level image of the transillumination of the blade, the gray level image can be used for developing a residual core in a cavity of the blade, and the gray level of the residual core is different from that of a blade material;

the material of the comparison sample is the same as that of the hollow blade, the thickness of the comparison sample is linearly increased from one end to the other end in the transverse direction, the thickness of the comparison sample is consistent in the longitudinal direction, the minimum thickness in the transverse direction is not more than the minimum wall thickness of the hollow blade, and the maximum thickness in the transverse direction is not less than the maximum wall thickness of the hollow blade;

a first elongated slot and a second elongated slot are arranged in the transverse direction of the comparison sample, the first elongated slot is parallel to the second elongated slot, and the depth and the width of the elongated slots are manufactured according to the acceptance requirements of the residual core of the blade;

the first long groove is a hollow groove, a filling core is formed in the second long groove, and molding slurry of the filling core is mixed with Gd₂O₃The residual core forming slurry;

the method comprises the following steps:

step one, comparing the sample transillumination

Placing a contrast sample in a reactor neutron detection system, and generating a transillumination image through neutron source irradiation;

step two, obtaining the thickness and the gray scale of the equidistant line

On the transillumination image of the contrast sample, a plurality of equidistant lines are taken along the transverse direction, and the image gray value H in the first long groove and the image gray value H in the second long groove at the longitudinal position corresponding to each equidistant line are obtained_C；

Step three, drawing a discrete point diagram

Establishing an XY plane coordinate system, wherein an X axis is a thickness value, a Y axis is a contrast value, discrete points are marked in the XY plane coordinate system, each discrete point corresponds to an equidistant line, an X value of each discrete point is the thickness of a contrast sample corresponding to the equidistant line, a Y value of each discrete point is the contrast of the corresponding equidistant line, and a calculation formula of the contrast is as follows: contrast C ═ H_C－H|/H；

Step four, drawing a reference straight line

And fitting to obtain a straight line through the discrete points marked in the third step, wherein the straight line is used as a reference line which represents the linear relation between the transillumination thickness T and the contrast C.

Further, both ends of the comparative sample in the transverse direction form edges of equal thickness, one end of the comparative sample is the minimum thickness, and the other end of the comparative sample is the maximum thickness.

Further, the minimum thickness of the comparative sample in the transverse direction was not more than 1mm, and the maximum thickness in the transverse direction was not less than 6 mm.

Further, the first long groove and the second long groove are both U-shaped cross-section grooves.

Further, Gd is filled and mixed in the second long groove₂O₃The ceramic core slurry is sintered and solidified at high temperature to obtain the filling core. Further, the core material overflowing from the second long groove is removed by machining after solidification. Still further, the filling degree of the filling core in the second long groove is 100%. Further, the Gd₂O₃Is powder with purity of 99.9% or more, Gd₂O₃The mass ratio of the powder to the ceramic core slurry is 0.015-0.03.

Furthermore, the matrix material of the residual core is silicon oxide or aluminum oxide.

Further, the number of the equidistant lines is at least 10.

The invention has the advantages and beneficial effects that:

the invention provides a reference method for detecting the neutron detection sensitivity of the hollow blade residual core, which avoids the complex processes of casting a real blade and depoling and the complexity of manufacturing a step test block and punching, is more convenient to obtain the detection sensitivity of the residual core with different material thicknesses and different doping contents, is close to the real detection sensitivity of the residual core, is beneficial to quantifying the detail detection capability of the residual core, can be used for verifying a neutron detection system and realizing the reference of the quantitative sensitivity of the residual core before the neutron detection of the hollow blade, and provides a basis for the detection implementation.

Drawings

FIG. 1 is a schematic diagram of a neutron detection system;

FIG. 2 is a side view of a comparative sample;

FIG. 3 is a top view of a comparative sample;

FIG. 4 is a perspective view of a comparative sample;

FIG. 5 is 0.2mm Gd of 3% by mass₂O₃A plot of material thickness versus contrast for the core;

FIG. 6 is a graph of material thickness versus contrast;

in fig. 1: 1. the method comprises the following steps of a neutron source, 2 a moderator, 3 a shield, 4 a gamma filter, 5 a diameter of a diaphragm, 6 a collimator, 7 a divergent neutron beam, 8 a contrast sample, 9 an imaging system, 10 a side with the minimum thickness, 11 a U-shaped groove, 12 a side with the maximum thickness, 13 a first long groove, 14 a second long groove, 15 an equidistant line, 16 a first long groove in a transillumination image, and 17 a second long groove in a transillumination image.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific examples, which are illustrative of preferred embodiments of the invention, but the invention is not limited to the above embodiments, and any obvious modifications, substitutions or alterations can be made by those skilled in the art without departing from the spirit of the invention.

The invention provides a reference line determining method for hollow blade residual core neutron detection sensitivity, which establishes a linear relation between transillumination thickness and contrast through comparing neutron transillumination images of a sample, is convenient for realizing residual core contrast sensitivity with different material thicknesses and different doping contents, is also beneficial to quantifying the detail detection capability of residual cores, and is used for verifying the reference indexes of the residual core quantitative sensitivity before neutron detection of a neutron detection system and a hollow blade.

The invention realizes the technical purpose through the following technical means:

a reference line determination method for hollow blade residual core neutron detection sensitivity is provided, wherein a reactor neutron detection system (1) and a comparison sample (2) are applied in the method;

the reactor neutron detection system can realize transillumination of the hollow blade and generate a gray level image of the transillumination of the blade, the gray level image can be used for developing a residual core in a cavity of the blade, and the gray level of the residual core is different from that of a blade material;

the material of the comparison sample is the same as that of the hollow blade, the thickness of the comparison sample is linearly increased from one end to the other end in the transverse direction, the thickness of the comparison sample is consistent in the longitudinal direction, the minimum thickness in the transverse direction is not more than the minimum wall thickness of the hollow blade, and the maximum thickness in the transverse direction is not less than the maximum wall thickness of the hollow blade;

a first elongated slot and a second elongated slot are arranged in the transverse direction of the comparison sample, the first elongated slot is parallel to the second elongated slot, and the depth and the width of the elongated slots are manufactured according to the acceptance requirements of the residual core of the blade;

the first long groove is a hollow groove, a filling core is formed in the second long groove, and molding slurry of the filling core is mixed with Gd₂O₃The residual core forming slurry;

the method comprises the following steps:

step one, comparing the sample transillumination

Placing a contrast sample in a reactor neutron detection system, and generating a transillumination image through neutron source irradiation;

step two, obtaining the thickness and the gray scale of the equidistant line

On the transillumination image of the contrast sample, a plurality of equidistant lines are taken along the transverse direction, and the image gray value H in the first long groove and the image gray value H in the second long groove at the longitudinal position corresponding to each equidistant line are obtained_C；

Step three, drawing a discrete point diagram

Establishing an XY plane coordinate system, wherein an X axis is a thickness value, a Y axis is a contrast value, discrete points are marked in the XY plane coordinate system, each discrete point corresponds to an equidistant line, an X value of each discrete point is the thickness of a contrast sample corresponding to the equidistant line, and a Y value of each discrete point is the corresponding equidistant lineThe contrast of the line, the calculation formula of the contrast is: contrast C ═ H_C－H|/H；

Step four, drawing a reference straight line

And fitting to obtain a straight line through the discrete points marked in the third step, wherein the straight line is used as a reference line which represents the linear relation between the transillumination thickness T and the contrast C.

Examples

Selecting DD5 high-temperature alloy to prepare a comparison sample, wherein the material of the comparison sample is the same as that of the detected hollow blade, and the size of the processed comparison sample is as follows: 55mm (transverse) × 28.5mm (longitudinal), the comparative sample increased linearly from one end to the other in the transverse direction, the two ends formed sides of equal thickness, the minimum thickness side having a thickness of 1mm, the maximum thickness side having a thickness of 10mm, and the transverse length between the minimum thickness side and the maximum thickness side being 35 mm.

And processing a first elongated slot and a second elongated slot in the transverse direction of the surface of the comparison sample, wherein the first elongated slot is parallel to the second elongated slot, the first elongated slot and the second elongated slot are both U-shaped cross-section slots, and the width and the depth of the first elongated slot and the second elongated slot are both 0.2mm after the sample is subjected to mold covering.

With reference to the related literature, incorporation of Gd into ceramic cores₂O₃The detection sensitivity can be obviously improved. This example is selected at SiO₂Gd is mixed in the base ceramic core slurry in a mass ratio of 3%₂O₃And uniformly mixing the powder, filling the slurry into the second long groove, curing for 0.5 hour in a high-temperature furnace at 1150 ℃, and removing the core material overflowing from the second long groove in a machining mode after cooling to achieve 100% filling degree.

And (3) placing the contrast sample between a neutron source and an imaging system, wherein the imaging system is a cassette containing a Gd screen and a single-sided film, tightly attaching and darkening the contrast sample, and exposing for 1 hour. The film was developed in a dark room to obtain a transillumination image of the comparative sample.

On the transillumination image of the contrast sample, 14 equidistant lines are taken along the transverse direction, and the image gray value H in the first long groove and the image gray value H in the second long groove at the longitudinal position corresponding to each equidistant line are obtained_C，And according to the formula of contrast ratio (C ═ H)_C-H/H) obtaining a contrast valueThe results are shown in Table 1.

TABLE 1 thickness and contrast values corresponding to equidistant lines

Establishing an XY plane coordinate system, wherein the X axis is a material thickness value, the Y axis is a contrast value, discrete points are marked in the XY plane coordinate system, each discrete point corresponds to an equidistant line, the X value of each discrete point is the thickness of a contrast sample corresponding to the equidistant line, and the Y value of each discrete point is the contrast corresponding to the equidistant line. According to the relevant literature, the core is distinguishable when the contrast C > 0.05, so that, for the DD5 superalloy material, a doping of 0.2mm with 3% Gd is found when the material thickness is less than 7mm₂O₃The residual core of (2).