CN108229080B - Optimization method for model unknown gas turbine blade digital ray subarea transillumination direction - Google Patents
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Abstract
The invention discloses a method for optimizing a digital ray subarea transillumination direction of a model unknown gas turbine blade, which comprises the steps of transilluminating a flat panel detector, determining a gray linear response interval of the flat panel detector, transilluminating each subarea of the blade from different angles, drawing a relation curve between the lowest gray value and the angle change of each subarea of the blade to determine the optimal transillumination direction of each subarea, splicing the transillumination images after each subarea conversion to obtain a transillumination image of the blade, processing the image of each subarea overlapping area, calculating the defect overlapping volume of each subarea by adopting an approximation algorithm, subtracting the defect volume of the overlapping area from the sum of the defect volumes obtained from each subarea to obtain the real volume size of the defect of the blade, and realizing the optimization processing of the transillumination direction. The invention improves the detection efficiency of tiny defects, avoids the design of complex furniture, reduces the detection cost, has high universality and lays a foundation for the positioning, qualitative and quantitative analysis of the defects.
Description
Technical Field
The invention belongs to the technical field of industrial ray nondestructive testing, and particularly relates to an optimization method for a model unknown gas turbine blade digital ray subarea transillumination direction.
Background
The gas turbine is a rotary impeller type power machine which takes continuously flowing gas as a working medium to drive an impeller to rotate at a high speed so as to convert the energy of fuel into useful work, and is widely applied in various fields. The gas turbine blade is usually manufactured by a precision casting method and needs to interact with a high-temperature, high-pressure and high-speed gas medium during the working process, so that various defects such as shrinkage cavity, shrinkage porosity, cracks, inclusions and the like can be generated in the manufacturing and service stages. These defects will seriously affect the working performance, the service life and the operational safety and reliability of the whole gas turbine. Therefore, the method for detecting the defects of the blades of the gas turbine is researched, the defects are timely and accurately found, and the method has very important significance for normal operation of the whole gas turbine set.
Because the gas turbine blade belongs to a complex free-form surface part and the manufacturing material is usually a nickel-based high-temperature alloy material, the nondestructive testing is usually carried out on the gas turbine blade by adopting a ray.
The industrial ct (computed tomography) technology can clearly, intuitively and accurately display the size and shape of the defect, but the equipment and test cost is too high, the detection cost of one blade is about 30 ten thousand, and the detection efficiency is low. Although the industrial photographic detection has the advantages of high imaging resolution, high sensitivity, intuition, reliability and the like, a large amount of films, processing medicines and the like are consumed in the detection process, the cost is high, and the detection efficiency is low due to the need of processing the films.
The dr (digital radiography) technique is a technique for directly performing digital X-ray imaging under the control of a computer, that is, a technique for converting X-ray information of a workpiece into digital signals by using a digital ray flat panel detector, reconstructing an image by using the computer and performing a series of image post-processing. The DR technology is close to photographic detection in resolution, low in transillumination cost and high in detection efficiency, and can be stored digitally, so that the DR technology is adopted for detection. The blade is large in size and uneven in thickness distribution, so that the blade needs to be partitioned, the traditional transillumination method transilluminates all the partitions from the same direction, and then the transillumination images are spliced. There is no clear requirement for transillumination direction, the randomness is large, and transillumination from the same direction cannot achieve the optimization of transillumination direction of each subarea. Based on the problems, the invention discloses a method for optimizing the transillumination direction of the digital ray subareas of the gas turbine blade with unknown model, which selects the optimal transillumination direction of each subarea.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an optimization method for a model with unknown digital ray subarea transillumination direction of a gas turbine blade, aiming at the defects in the prior art.
The invention adopts the following technical scheme:
the optimization method of the digital ray subarea transillumination direction of the model unknown gas turbine blade comprises the steps of transilluminating a flat panel detector, determining a gray linear response interval of the flat panel detector, adopting a lead wire to divide the blade into subareas, transilluminating each subarea of the blade from different angles, drawing a relation curve of the lowest gray value and the angle change of each subarea of the blade to determine the optimal transillumination direction of each subarea, splicing the transillumination images after each subarea is converted to obtain a transillumination image of the blade, processing the image of each subarea overlapping area, determining the defect volume according to the relation curve of the defect gray level and the defect thickness, calculating the subarea-crossing defect overlapping volume by adopting an approximate algorithm, subtracting the defect volume of the overlapping area from the sum of the defect volumes obtained from each subarea to obtain the real defect volume of the blade, and realizing the optimization processing of the transillumination direction.
Specifically, the tube voltage is changed from the lowest value to the highest value, transillumination is carried out on the flat panel detector, a relation curve of an average gray value and the square of the voltage is drawn according to the average gray value of transillumination images obtained under all voltages, and a gray range corresponding to a linear response interval of the flat panel detector is determined according to the linear region of the relation curve of the average gray value and the square of the voltage.
Further, according to the linear relation between the output gray value of the flat panel detector and the input ray intensity, the linear relation between the output gray value of the flat panel detector and the square of the tube voltage is determined, and the ray intensity I at the position of a distance F away from the focus of the X-ray tubeFThe calculation is as follows:
IF＝α·Z·i·V2/F2
wherein α is a proportionality coefficient, Z is an atomic number of the target, i is a tube current, and V is a tube voltage.
Specifically, the perspective direction of the blade is quantified by measuring the angle formed by the reference plane of the blade crown and the blade root part on the blade and the flat panel detector in the horizontal plane, a perspective image of which the gray scale range is in the linear range of the flat panel detector is found out, and a relation curve of the lowest gray scale value of each partition of the blade and the angle change is drawn.
Further, the optimal transillumination angle range of each blade partition is determined, the blade placing angle is changed, the angle is increased by 0.5 degrees from the lowest value to the highest value in the optimal transillumination angle range, the included angle formed by the reference surface of the blade shroud part and the flat panel detector in the horizontal plane is changed to transilluminate the blades, and quantification of the blade transillumination direction is completed.
Further, by taking the region with the highest leaf thickness in the transillumination region as a reference, determining the transillumination angle when the regional transillumination thickness is the lowest as the optimal transillumination direction, wherein the transillumination image is a negative image with higher ray intensity and larger gray value.
Further, the optimal perspective angle of the 1 st subarea of the blade is 30-60 degrees.
Specifically, the blade is transilluminated by taking the transillumination direction of the 1 st subarea of the blade as a reference, the width of the 2 nd subarea, the 3 th subarea, the 4 th subarea, the 5 th subarea and the 6 th subarea of the blade in the transillumination direction of the 1 st subarea is obtained, then the transillumination image width obtained by transilluminating the 2 nd subarea, the 3 th subarea, the 4 th subarea, the 5 th subarea and the 6 th subarea in the respective optimal transillumination directions is adjusted to the width in the transillumination direction of the 1 st subarea, and then the blade is spliced by taking the 1 st subarea as.
Specifically, a wedge block made of the same material as the blade is manufactured, transillumination is carried out to obtain a relation curve between the gray level of the defect and the thickness of the defect, each partition overlapping area is approximately triangular, the gray level value at the partition boundary of transillumination images of two partitions is converted to obtain the length of two sides of the triangle, the included angle is the difference of transillumination angles of the two partitions, the area of the triangle is further obtained, the area of the triangle is multiplied by the width of a pixel point based on a finite element principle to obtain the overlapping volume of the pixel point position, then the overlapping area of each pixel point position of the defect on the partition boundary is calculated, and the obtained total defect volume of the overlapping area is obtained through summation.
Further, the defect volume v of the overlapping region of the 1 st partition and the 2 nd partition12The calculation is as follows:
wherein a is the side length of a pixel point of the flat panel detector, and theta1Optimum transillumination angle, θ, for zone 12Optimum transillumination angle for the 2 nd division, h1kThickness h corresponding to the gray value of the pixel at the boundary line in the 1 st partial image2kThickness corresponding to gray value of pixel at boundary in 2 nd region imageAnd i is the number of the defective pixels on the 1 st and 2 nd partition boundary.
Compared with the prior art, the invention has at least the following beneficial effects:
the optimization method for the digital ray subarea transillumination direction of the unknown model gas turbine blade improves the detection efficiency of tiny defects by optimizing the transillumination direction of each subarea of the gas turbine blade, obtains the blade transillumination direction by measuring the angles of the blade crown, the blade root reference surface and the flat panel detector, avoids the design of a complex special clamp, is simple and easy to implement and low in cost, performs image splicing on each subarea overlapping area and eliminates the overlapping volume, and provides a premise for further positioning, quantifying and qualitatively processing the blade defects.
Further, the transillumination image gray scale is in the linear response gray scale range of the flat panel detector, which is the most basic premise of digital ray transillumination, and the transillumination image with the gray scale in the linear response range of the flat panel detector is an effective transillumination image, so that the gray scale range corresponding to the linear response interval of the flat panel detector needs to be obtained in advance.
Furthermore, the gray level of the transillumination image is in the linear response range of the flat panel detector, which indicates that the image is an effective transillumination image, and on the basis, a relation curve of the lowest value of the gray level of each partition and the angle change is drawn, and the angle value corresponding to the highest point of the curve is the partition optimal transillumination angle. Because the gray value of the transillumination image is inversely proportional to the thickness of the workpiece, the lowest gray value is located at the thickest part of the workpiece, and the angle corresponding to the highest point of the curve is the thinnest transillumination angle at the thickest part of the workpiece. The thinner the workpiece, the higher the detection efficiency of fine defects, so the angle is selected as the zoned optimal transillumination angle.
Furthermore, the traditional transillumination mode is to transilluminate each subarea of the whole blade from the same transillumination direction, so that the transillumination thickness of each subarea is not the lowest value, and the optimization of the fine defect detection efficiency cannot be realized, so that different transillumination directions are respectively selected for each subarea, and the fine defect detection efficiency is necessarily improved. The optimization of the transillumination direction firstly needs to determine the standard of the vectorization of the transillumination direction.
Furthermore, the thicker the transillumination thickness is, the lower the detection efficiency of the small defect is, the lowest the detection efficiency of the small defect in the thickest region of the blade is, and the lowest detection efficiency of the blade to the small defect reaches the maximum when the transillumination thickness of the region is the lowest, so that the optimal transillumination direction is taken as the minimum detection efficiency.
Furthermore, the size of the spliced blade is ensured to be unchanged by splicing the transillumination images, so that the size of the spliced blade can be ensured to be unchanged by changing the widths of the rest subareas to the value on the basis of the width of each subarea transillumination image obtained in the transillumination direction of the first subarea.
Furthermore, when the volume of the cross-region defect is calculated, if only the defect volumes in each partition are superposed, part of the defect volumes are repeatedly calculated, so a near algorithm is adopted to calculate the defect overlapping volume, the defect volumes which are repeatedly calculated are subtracted, and the error of volume calculation is reduced.
In conclusion, the invention improves the detection efficiency of the tiny defects, avoids the design of complex furniture, reduces the detection cost, has high universality and lays a foundation for the positioning, qualitative and quantitative analysis of the defects.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic view of a gas turbine blade digital radiography detection system connection;
FIG. 2 is a schematic view of a blade angle acquisition method;
FIG. 3 is a schematic view of a blade segment;
FIG. 4 is a schematic diagram illustrating the processing principle of the overlapped part of the images;
FIG. 5 is a schematic diagram of a gray scale linear response interval of a flat panel detector;
FIG. 6 is a schematic view of a digital display angle ruler with a bubble level;
FIG. 7 is a graph showing the relationship between the minimum gray level and the angle variation;
FIG. 8 is a graph illustrating the relationship between defect thickness and gray scale.
Detailed Description
Aiming at the defects that the digital ray detection is carried out on a large-scale gas turbine in practical engineering application, a blade is partitioned firstly, then each partition of the blade is transilluminated from the same direction, and the transillumination direction does not reach the optimal transillumination direction, the invention provides an optimization method of the digital ray partition transillumination direction of the unknown gas turbine blade model.
Referring to fig. 1, a ray source is arranged on one side of a turntable, a detector is arranged on the other side of the turntable, the ray source and the detector are respectively connected with a control system, and blades are arranged on the turntable, so that a gas turbine blade digital ray detection system is formed.
The invention discloses an optimization method for a model unknown gas turbine blade digital ray subarea transillumination direction, which comprises the following specific steps:
s1, determining the linear response interval of the gray scale of the flat panel detector
And keeping other parameters unchanged, changing the tube voltage from the lowest value to the highest value, and transilluminating the flat panel detector.
Intensity of radiation I at a distance F from the focal spot of the X-ray tubeFIs composed of
IF＝α·Z·i·V2/F2(1)
Wherein α is a proportionality coefficient (1.1-1.4) x 10-6Z is the atomic number of the target, i is the tube current (mA), and V is the tube voltage (kV);
and calculating the average gray value of the transillumination image obtained under each voltage, and drawing a relation curve of the average gray value and the square change of the voltage.
As can be seen from the above formula (1), under the condition that other parameters are not changed, the radiation intensity is directly proportional to the square of the tube voltage, and the linear response of the flat panel detector is the linear relationship between the output gray-scale value of the flat panel detector and the input radiation intensity, so that within the linear response range of the flat panel detector, the output gray-scale value of the flat panel detector should also be linear relationship with the square of the tube voltage.
And finding out a linear area in the relation curve of the drawn average gray value and the voltage square, and determining a gray range corresponding to the linear response interval of the flat panel detector.
S2, obtaining the optimal transillumination angle of each subarea
And (3) transilluminating each partition of the blade from different angles, finding out a transilluminated image with a gray scale range in the linear range of the flat panel detector, and drawing a relation curve between the lowest gray scale value of each partition of the blade and the angle change.
The perspective direction optimization criterion is that the perspective direction with the minimum perspective thickness is the optimal perspective direction, and as the blades are complex free-form surface parts and the thicknesses of all points in the perspective area are different, the perspective angle when the perspective thickness of the area is the minimum is found out as the optimal perspective direction by taking the area with the highest part thickness in the perspective area as a reference.
The perspective direction of the blade corresponds to the placing angle of the blade on the rotary table one by one, so the perspective direction of the blade is quantified by measuring the angle formed by the reference surface of the blade crown and the blade root part on the blade and the flat panel detector in the horizontal plane, as shown in fig. 2.
And S3, partitioning the blade by adopting lead wires, wherein the lead wires have a large atomic number and a large attenuation rate to rays, and highlight features are formed on the transillumination image to be used as the marks for partitioning the blade and splicing the image. A blade-section schematic is shown in fig. 3.
Because the same subarea is transilluminated from different directions, the obtained transillumination images are different in width, the leaf needs to be transilluminated by taking the transillumination direction of the 1 st subarea as a reference to obtain the width of the 2, 3, 4, 5 and 6 subareas of the leaf in the transillumination direction of the 1 st subarea, then the transillumination images obtained by transilluminating the 2, 3, 4, 5 and 6 subareas in the respective optimal transillumination directions are adjusted to the width in the transillumination direction of the first subarea, and then the leaf is spliced by taking the 1 st subarea as a reference.
S4, cross-partition defect overlap region volume calculation
Firstly, a wedge block made of the same material as the blade is manufactured, transillumination is carried out, a relation curve between defect gray scale and defect thickness is obtained, the image defect gray scale is converted into the thickness, and the size of the cross-partition defect overlapping volume is calculated by adopting an approximate algorithm.
When left and right adjacent images are stitched, the stitched images have overlapping portions, and the overlapping portions of the images need to be processed when calculating the cross-partition defect volume, and the principle is as shown in fig. 4.
The overlap region can be approximately regarded as a triangle, the corresponding relation between the gray scale and the thickness is determined when the defect volume is calculated, the length of two sides of the triangle can be obtained through conversion according to the gray scale value at the partition boundary of the transillumination images of the two partitions, and the included angle is the difference of transillumination angles of the two partitions.
Under the condition that the lengths of two sides of the triangle and the included angle of the two sides of the triangle are known, the area of the triangle can be obtained, the overlapping volume of the pixel point position can be obtained by multiplying the area of the triangle by the pixel point width based on a finite element principle, the overlapping area of each pixel point position of the defect on the partition boundary line can be obtained by the same method, the obtained defect total volume of the overlapping area can be obtained, and the defect volume of the overlapping area is subtracted from the sum of the defect volumes obtained by calculation of each partition, so that the real volume size of the defect can be obtained.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
1. Determining a gray scale linear response interval of a flat panel detector
And (3) transilluminating the flat panel detector by adopting a transilluminating distance of 1000mm, keeping the current of 0.6mA unchanged, changing the voltage from the lowest voltage of 5kV of the ray machine to the highest voltage of 220kV, and increasing 1kV every time. Obtaining a transillumination image f5～f220The average gray value of each transillumination image is calculated, a relation curve of the average gray value of the transillumination image and the square of the transillumination voltage is drawn as shown in figure 5, and a gray linear response interval [ A, B ] of the flat panel detector is obtained by analyzing a linear region in the curve]。
2. Obtaining the optimal transillumination direction of each subarea
The blade is divided into an upper part and a lower part, wherein the upper part is divided into three subareas 1, 2 and 3, and the lower part is divided into three subareas 4, 5 and 6. The digital display angle ruler with the air level is used for measuring the included angle formed by the reference surface of the blade shroud and the blade root part and the flat panel detector in the horizontal plane, the basic structure of the digital display angle ruler is shown in figure 6, and the angle precision measured by the angle ruler can reach +/-0.1 degrees.
Here, taking the 1 st partition as an example, a method for acquiring the optimal transillumination direction of each partition of the blade is described.
The transillumination angle of the 1 st partition is obtained by measuring the included angle formed between the reference plane of the blade crown part and the flat panel detector in the horizontal plane. Through visual observation, the optimal transillumination angle of the subarea can be roughly determined to be within the range of 30-60 degrees, the rotating table is rotated, the blade arrangement angle is changed, the included angle formed by the reference plane of the blade shroud part of the blade and the flat panel detector in the horizontal plane is increased from 30 degrees to 60 degrees, 0.5 degree is increased every time, the 1 st subarea of the blade is transilluminated, and 61 transillumination images of the subarea 1 are obtained. Fig. 7 shows the relationship between the minimum gray level and the change in angle of each transillumination image.
The angle theta corresponding to the highest point in the curve is the optimal transillumination angle of the 1 st partition, and the transillumination direction corresponding to the optimal transillumination angle is the optimal transillumination direction. The same way can be used to obtain the optimal transillumination direction of the blade 2, 3, 4, 5, 6 subareas.
3. Each zone is spliced
Under the optimal transillumination direction of the 1 st subarea, transilluminating the 1 st, 2 nd, 3 th, 4 th, 5 th and 6 th subareas of the blades, and obtaining the transillumination image widths of the 2 nd, 3 th, 4 th, 5 th and 6 th subareas at the moment as wid12、wid13、wid14、wid15、wid16。
In the optimal transillumination direction of the 2 nd subarea, transilluminating the blade subarea 2 to obtain a transillumination image of the blade subarea 2, and adjusting the transillumination image width to wid by using an imresize function in matlab12。
In the same way, the width of the transillumination image obtained by transilluminating the subareas 3, 4, 5 and 6 in the respective optimal transillumination direction is respectively adjusted to wid13、wid14、wid15、wid16。
And then respectively splicing the transillumination images subjected to the partition transformation of 2, 3, 4, 5 and 6 to the transillumination image of the 1 st partition by taking the transillumination image of the 1 st partition as a reference to obtain the transillumination image of the whole blade.
4. Cross-partition defect overlap region volume calculation
Firstly, a wedge block made of the same material as the blade is manufactured, transillumination is carried out, and a relation curve between defect gray scale and defect thickness is obtained, as shown in fig. 8.
Taking the overlapping area of the subarea 1 and the subarea 2 as an example, the optimal perspective angles are theta1And theta2The side length of a pixel point of the flat panel detector is a, the number of defects on the 1 st and 2 nd partition boundaries is i, and the gray value of the pixel at the partition boundary in the 1 st partition image is gray11，gray12，……，gray1iCorresponding thickness is respectively h11，h12，……，h1i(ii) a The gray value of the pixel at the boundary in the 2 nd subarea image is gray21，gray22，……，gray2iCorresponding thickness is respectively h21，h22，……，h2i. The 1 st and 2 nd partitions overlap the partial defect volume v12Is composed of
According to the invention, the gray scale curve of the flat panel detector is manufactured by changing the voltage of the tube and keeping other parameters unchanged, so that the linear response interval of the flat panel detector is obtained, the transillumination image obtained later is ensured to be in the linear range, and a theoretical premise is provided for the subsequent steps. When the optimal transillumination direction of each subarea is determined, the approximate range of the optimal transillumination direction of the blade subareas is obtained through visual observation, and the workload is greatly reduced. And then changing the perspective angle of the blade by rotating the turntable, performing perspective on the blade, making a relation curve of the lowest gray value and the angle change of each perspective image, and obtaining the optimal perspective direction of each subarea through the curve. And adjusting the size of each subarea transillumination image by taking the first subarea transillumination image as a reference, and splicing the blades, so that the size of the spliced blade image is unchanged. By manufacturing the wedge block, the corresponding relation between the gray level and the thickness of the transillumination image is obtained, the gray level of the image defect is converted into the thickness, the overlapping volume of the trans-regional defect is calculated by adopting an approximate algorithm, and the error of defect volume calculation can be greatly reduced.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (4)
1. The optimization method of the model unknown gas turbine blade digital ray subarea transillumination direction is characterized in that, transilluminating the flat panel detector, determining the gray linear response interval of the flat panel detector, partitioning the blade by lead wires, transilluminating each subarea of the blade from different angles, drawing a relation curve between the lowest gray value and the angle change of each subarea of the blade to determine the optimal transilluminating direction of each subarea, splicing the transilluminating images transformed by each subarea to obtain the transilluminating image of the blade, processing the image of each subarea overlapping area, determining the defect volume according to the relation curve of the defect gray level and the defect thickness, calculating the subarea-crossing defect overlapping volume by adopting an approximation algorithm, and subtracting the defect volume of the overlapping area from the sum of the defect volumes obtained from the subareas to obtain the real volume size of the blade defect so as to realize the optimization processing in the transillumination direction;
the method comprises the steps of transilluminating the blade by taking the transillumination direction of the 1 st subarea of the blade as a reference to obtain the width of the 2 nd, 3 rd, 4 th, 5 th and 6 th subareas of the blade in the transillumination direction of the 1 st subarea, adjusting the width of a transillumination image obtained by transilluminating the 2 nd, 3 rd, 4 th, 5 th and 6 th subareas of the blade in the respective optimal transillumination direction to the width in the transillumination direction of the 1 st subarea, and splicing the blade by taking the 1 st subarea as a reference;
changing the tube voltage from the lowest value to the highest value, transilluminating the flat panel detector, drawing a relation curve of an average gray value and the square of the voltage according to the average gray value of transilluminated images obtained under various voltages, determining a gray range corresponding to a linear response interval of the flat panel detector according to the linear region of the relation curve of the average gray value and the square of the voltage, determining that the output gray value of the flat panel detector is in a linear relation with the square of the tube voltage according to the linear relation of the output gray value of the flat panel detector and the input ray intensity, and determining the ray intensity I at the position of a distance F away from the focus of the X-ray tubeFThe calculation is as follows:
IF＝α·Z·i·V2/F2
wherein α is a proportionality coefficient, Z is an atomic number of the target, i is a tube current, and V is a tube voltage
By measuring the angle formed by the reference surfaces of the tip shroud and root parts on the blade and the flat panel detector in the horizontal plane, quantifying the transillumination direction of the blade, finding out the transillumination image with the gray scale range in the linear range of the flat panel detector, drawing the relation curve of the lowest gray scale value and the angle change of each partition of the blade, determining the optimal transillumination angle range of each partition of the blade, changing the blade placement angle, increasing 0.5 degree from the lowest value to the highest value in the optimal transillumination angle range, changing the included angle formed by the reference surface of the blade shroud part and the flat panel detector in the horizontal plane to transilluminate the blade, completing the quantification of the blade transillumination direction, and determining a transillumination angle when the transillumination thickness of the region is the lowest as an optimal transillumination direction by taking the region with the highest blade thickness in the transillumination region as a reference, wherein the transillumination image is a negative image with higher ray intensity and higher gray value.
2. The method for optimizing the trans-illumination direction of the digital ray subarea of the unknown model gas turbine blade of claim 1, wherein the optimal trans-illumination angle of the 1 st subarea of the blade is 30-60 °.
3. The method for optimizing the digital ray subarea transillumination direction of the model unknown gas turbine blade according to claim 1, is characterized in that a wedge block made of the same material as the blade is manufactured, transillumination is performed to obtain a defect gray scale and defect thickness relation curve, each subarea overlapping area is approximately triangular, the gray scale value at the subarea boundary of the transillumination images of the two subareas is converted to obtain the lengths of the two sides of the triangle, the included angle is the difference of transillumination angles of the two subareas, further the area of the triangle is obtained, the pixel point position overlapping volume is obtained by multiplying the area of the triangle by the pixel point width based on a finite element principle, then the overlapping area of each pixel point position of the defect on the subarea boundary is obtained, and the summation is performed to obtain the defect total volume of the obtained overlapping area.
4. The method for optimizing the digital ray subarea transillumination direction of the unknown model gas turbine blade of claim 3, wherein the defect volume v of the overlapping area of the 1 st subarea and the 2 nd subarea12The calculation is as follows:
wherein a is the side length of a pixel point of the flat panel detector, and theta1Optimum transillumination angle, θ, for zone 12Optimum transillumination angle for the 2 nd division, h1kThickness h corresponding to the gray value of the pixel at the boundary line in the 1 st partial image2kFor grey value correspondence of pixels at the boundary lines in the 2 nd zone imageI is the number of defective pixels at the 1 st and 2 nd division boundary.
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