A method for ultrasonic testing the wall thickness of cubic single crystal turbine blades

Abstract

The present invention discloses a method for ultrasonically detecting the wall thickness of a cubic single crystal turbine blade. The method establishes a sound velocity model, measures the wave velocity of a standard sheet, and measures the angle between the vector direction of each wall thickness measurement point and the theoretical Y coordinate axis in a three-dimensional model. oh , the rotation angle of the secondary dendrite [100] of the tested part is measured by Laue method or XRD diffraction method α and the deviation angle between [001] orientation and Z axis i , the angle oh , rotation angle α Deviation angle from the Z axis i Substitute it into the sound velocity calculation model to obtain the true sound velocity at each wall thickness measurement point; then import the wall thickness data measured by the wall thickness meter into the sound velocity model formula to obtain the corrected true wall thickness value. This method can solve the measurement error caused by the anisotropy of cubic alloys and has the advantages of high detection efficiency and low detection cost.

Description

Technical Field

[0001] The invention relates to the technical field of gas engine turbine blade detection, and in particular to a method for ultrasonically detecting the wall thickness of a cubic single crystal turbine blade. Background Art

[0002] At present, the commonly used methods for detecting the wall thickness of gas turbine blades are mainly ultrasonic detection and industrial CT detection. Industrial CT detection of single crystals has the characteristics of high detection accuracy, but the equipment investment is large, the detection cost is high, and the detection efficiency is low. The traditional ultrasonic detection method is only applicable to isotropic materials and cannot be directly used for the wall thickness detection of anisotropic materials or workpieces. Single crystal high-temperature alloys are face-centered cubic crystal structures with four-axis symmetric anisotropic characteristics. Conventional ultrasonic wall thickness measurement methods can no longer be directly applied to cubic crystal alloy materials. For the alloy longitudinal wave ultrasonic sound velocity in the

[100] direction is the smallest, and the sound velocity in the

[110] direction is about 15% higher than that in the

[100] direction. For a wall thickness of 2mm, the measurement error can reach 0.3mm. If the traditional ultrasonic wall thickness measurement method is used, the measurement deviation is extremely large.

[0003] To this end, Chinese Patent No. 202110082787.0 discloses a method and device for measuring anisotropic materials. The method makes standard plates in the

[100] and

[110] directions, and measures the longitudinal wave sound velocity V_L_

[100] of

[100] , the transverse wave sound velocity V_T_

[100] of

[100] and the longitudinal wave sound velocity V_L_

[110] of

[110] , and according to Christoffel The elastic stiffness coefficients C11, C12, and C44 are calculated by the equation, and the elastic stiffness coefficient matrix is ​​further established. Based on the elastic stiffness coefficient matrix, the compliance coefficient matrix is ​​obtained, and the fourth-order compliance tensor is obtained based on the compliance coefficient matrix. The elastic modulus in different directions is further calculated, and finally a 3D sound velocity diagram is obtained. However, the entire wall thickness solution process is complicated, which places high demands on the measurement personnel and is difficult to apply in batch testing. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for ultrasonically detecting the wall thickness of cubic single crystal turbine blades. The method has the advantages of convenient operation, high precision, and applicability to batch detection.

[0005] To this end, the present invention provides a method for ultrasonically detecting the wall thickness of a cubic single crystal turbine blade, comprising:

[0006] Measure the angle between each wall thickness measurement point and the Y axis of the theoretical coordinate system in the 3D model of the part to be tested. oh ;

[0007] Based on the RPS (Reference Point System) positioning points on the part to be tested, a six-point positioning detection fixture is made. The part to be tested is clamped using the positioning detection fixture, and the rotation angle of the secondary dendrite

[100] of the part to be tested is measured using the Laue method. α ,

[001] Orientation deviation angle from the Z axis i , where the reference direction of measurement is the Z axis, the reference plane is the YOZ plane, the X axis is perpendicular to the reference plane and points vertically upward, and the Y axis is horizontal and points to the right;

[0008] Use an ultrasonic wall thickness gauge to measure the standard sound velocity of standard plates in the

[100] and

[110] directions of the same alloy as the part to be tested, and obtain the longitudinal wave sound velocity value in the standard direction. V _100 and V _110 ;

[0009] exist V _110 The wall thickness of the part to be tested is measured at the wall thickness measuring point under the condition of sonic velocity and calculated as d i， The angle oh , rotation angle α and deviation angle i Substitute into the sound speed 3D model formula to obtain the sound speed after anisotropy calibration V , then according to d i ’=d i * V / V _110 Calculate the exact wall thickness value; if V _100 If the wall thickness is measured under the condition of sonic velocity, the formula d i ’=d i * V / V _110 In V _110 Replace with V _100 .

[0010] Specifically, a special positioning card is designed according to the coordinate position of the wall thickness point on the drawing of the part to be measured, and the wall thickness measurement point is marked on the part to be measured with the help of the positioning card.

[0011] Specifically, the angle between the wall thickness measurement point and the Y coordinate axis of the theoretical coordinate system oh For measurement, observe along the Z axis, the counterclockwise angle is positive, the clockwise angle is negative, and the included angle is the angle between the measuring direction of the wall thickness point and the horizontal direction to the right.

[0012] Specifically, the standard sheet orientation angle error is within the range of ±3°.

[0013] Specifically, the solution process of the sound speed 3D model formula is:

[0014] For orientations with direction cosines l, m, n, the speed of sound is:

[0015]

[0016] According to the trigonometric function relationship, we can calculate

[0017] ;

[0018] Will l 2 、m 2 、 2 Substituting into the speed of sound formula, we get the speed of sound 3D model formula:

[0019]

[0020] Among them, ω, α , i The unit is °, and l, m, and n are the direction cosines of the crystallographic coordinate axes

[100] ,

[010] , and

[001] respectively.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] For turbine blades of characteristic models, the angle ω between the measurement direction (vector direction) of each measurement point and the positive direction of the Y axis is a fixed value. No complicated software is required, and only an EXCEL table is used to convert all the angles ω, α , i By entering the equation of the velocity of sound into the table, the accurate wall thickness value after correcting the velocity of sound can be obtained.

[0023] The present invention can solve the problem of large error caused by the change of ultrasonic sound velocity in different measuring directions due to the anisotropy of turbine blades, and does not require C 11 , C 12 , C 44 The calculation of variables such as elastic constants, elastic stiffness coefficient matrix, compliance coefficient matrix, elastic modulus, etc. has the advantages of convenient operation, high accuracy and suitability for batch testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings of the present invention are used to provide further understanding of the present invention, illustrative embodiments and description thereof, but do not constitute improper limitations of the present invention. In the accompanying drawings:

[0025] Figure 1It is a schematic diagram of the angle between the measuring direction of the turbine blade detection point and the Y-axis of the coordinate axis of the present invention. DETAILED DESCRIPTION

[0026] To make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0027] A method for ultrasonically detecting the wall thickness of a cubic single crystal turbine blade, comprising:

[0028] 1. Confirmation of the theoretical direction angle of the turbine blade detection point

[0029] The angle ω between the vector direction (measurement direction) of each detection point in each detection section of the turbine blade and the positive direction of the Y axis is measured in the three-dimensional model as follows: Figure 1 As shown. It is defined that when observing along the Z direction, the positive direction is rotated from the positive direction of the Y axis to the positive direction of the X axis, that is, the counterclockwise angle is positive and the clockwise angle is negative. The angle is the angle between the measuring direction of the wall thickness point and the horizontal rightward direction.

[0030] 2. Determine the deviation angle of the three-dimensional crystal orientation of the turbine blade

[0031] Based on the RPS (Reference Point System) positioning points on the part to be tested, a six-point positioning test fixture is made, and the turbine blade is fixed to the test fixture. The reference direction of the test is the Z axis, the reference plane is the YOZ plane, the X axis is perpendicular to the reference plane and points vertically upward, and the Y axis is horizontal to the right. The Laue method is used to measure the three-dimensional crystal orientation angle of the turbine blade to be tested, including at least THETA ( i , 001 direction and Z axis angle), ALPHA ( α The definition of the orientation of the secondary dendrite (rotation angle

[100] ) refers to the manual of the British National Physical Laboratory, Measurement Good Practice Guide No. 112 "Improving single-crystal orientation determination for advanced nickel-based alloys".

[0032] 3. Measurement of sound velocity of standard film and establishment of sound velocity model

[0033] In cubic materials, the material has three independent elastic constants: C 11 , C 12 , C 44is the anisotropic elastic constant of the material, let l、m、n are the direction cosines of the crystallographic coordinate axes

[100] ,

[010] , and

[001] respectively, where l 2 + m 2 + n 2 =1 ; Material density is ρ, sound speed is V. According to elastic wave theory, for cubic crystals, the longitudinal wave sound speed V can be calculated by the following formula:

[0034]

[0035] From the speed of sound formula:

[0036]

[0037]

[0038] V _100 is the longitudinal sound velocity of the material along the

[100] direction, V _110 is the longitudinal sound velocity of the material along the

[110] direction.

[0039] Standard plates in the

[100] and

[110] directions are made of the same material as the turbine blades. The orientation angle error of the standard plates is within ±3°. The longitudinal wave velocity is measured using an ultrasonic wall thickness meter. V _100 and V _110 , will (C 12 +2C 44 ) As a whole, solving the two-variable linear equation can solve C 11 , (C 12 +2C 44 ), we get:

[0040]

[0041] The C 11 and (C 12 +2C 44 ) into the speed of sound formula, the speed of sound in any direction can be calculated.

[0042] For orientations with direction cosines l, m, n, the speed of sound is:

[0043]

[0044] The squares of the three direction cosines l 2 、m2 、n 2 , which can be calculated based on the trigonometric function relationship.

[0045] ;

[0046] Will l 2 、m 2 、n 2 Substituting into the speed of sound model formula, we can obtain the speed of sound 3D model formula.

[0047]

[0048] Among them, ω, α , i The unit is °.

[0049] 4. Calculation of accurate wall thickness value at the turbine blade wall thickness measurement point

[0050] exist V _110 The wall thickness of the part to be tested is measured at the wall thickness measuring point under the condition of sonic velocity and calculated as d i， The angle oh , rotation angle α and deviation angle i Substitute into the sound speed 3D (Three Dimensions) model formula to obtain the sound speed after anisotropy correction V , then according to d i ’=d i * V / V _110 Calculate the exact wall thickness value; if V _100 If the wall thickness is measured under the condition of sonic velocity, the formula d i ’=d i * V / V _110 In V _110 Replace with V _100 .

[0051] For turbine blades of characteristic models, the angle ω between the measurement direction (vector direction) of each measurement point and the positive direction of the Y axis is a fixed value. No complicated software is required, and only an EXCEL table is used to convert all the angles ω, α , iThe accurate wall thickness value after correcting the sound velocity can be obtained by inputting the equation of the sound velocity into the table. The present invention can solve the problem of large error caused by the change of ultrasonic sound velocity in different measuring directions due to the anisotropy of turbine blades, and there is no need to perform C 11 , C 12 , C 44 The calculation of variables such as elastic constants, elastic stiffness coefficient matrix, compliance coefficient matrix, elastic modulus, etc. has the advantages of convenient operation, high accuracy and suitability for batch testing.

[0052] In order to facilitate the measurement of the measuring points, a special positioning card is designed according to the coordinate position of the wall thickness point on the part drawing to be measured, and the wall thickness measurement point is marked on the part to be measured with the help of the positioning card.

[0053] Specific case 1

[0054] For a second-generation single crystal high-temperature alloy turbine blade, the following steps are included:

[0055] S1. Make standard sheets in the

[100] and

[110] directions and use an ultrasonic wall thickness meter to measure the longitudinal wave velocity. V _100 is 5413m / s, V _110 6196 m / s;

[0056] S2. Measure the angles between the wall thickness points d1~d6 of the two measuring sections I and II and the Y axis in the theoretical coordinate system in the three-dimensional model. oh ;

[0057] S3, using LAUE equipment to measure the crystal orientation deviation angle THETA of the turbine blade ( i ) is 3.1°, ALPHA ( α ) is 41.1°;

[0058] S4. The measured values ​​of all wall thickness points are measured using an Ultrasonic Testing (UT) wall thickness meter, and the actual sound velocity at different wall thickness points of the blade obtained by the sound velocity 3D model formula is used for correction to obtain UT measurement values. After the measurement is completed, the blade is anatomically measured to obtain anatomical measurement values, as shown in Table 1. It can be seen from Table 1 that the errors between the UT measurement values ​​at each cross-section measurement point measured using the method of the present invention and the actual anatomical measurement values ​​are less than ±0.03 mm.

[0059] Table 1

[0060]

[0061] For a third-generation single crystal high-temperature alloy turbine blade, the following steps are included:

[0062] S1. Make standard sheets in the

[100] and

[110] directions and use an ultrasonic wall thickness meter to measure the longitudinal wave velocity. V _100 is 5344m / s, V _110 6121 mm / s;

[0063] S2. Measure the angles between the wall thickness points d1~d6 of the three measurement sections I and II and the Y axis in the theoretical coordinate system in the three-dimensional model. oh ;

[0064] S3, using LAUE equipment to measure the crystal orientation deviation angle THETA of the turbine blade ( i ) is 1.0°, ALPHA ( α ) 71.0°;

[0065] S4. The measured values ​​of all wall thickness points are measured using a UT wall thickness meter, and the actual sound velocity at different wall thickness points of the blade obtained by the sound velocity 3D model formula is corrected to obtain the UT measurement value. After the measurement is completed, the blade is anatomically measured to obtain the anatomical measurement value, as shown in Table 2. It can be seen from Table 2 that the error between the UT measurement value at each cross-section measuring point measured by the method of the present invention and the actual anatomical measurement value is less than ±0.03 mm.

[0066] Table 2

[0067]

[0068] Through the above two cases, it can be concluded that the method of the present invention can solve the measurement error caused by the anisotropy of cubic crystal turbine blades. The detection accuracy can reach ±0.03mm. The maximum wall thickness error before correction can reach 15% of the true value of the wall thickness. The error for the 2mm wall thickness point is 0.3mm. It has the advantages of high detection efficiency and low detection cost, and is more suitable for large-scale industrial production requirements.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, the technical solutions described in the aforementioned embodiments may still be modified without causing the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for ultrasonically detecting the wall thickness of cubic single crystal turbine blades, characterized in that: include: Measure the angle between each wall thickness measurement point and the Y axis of the theoretical coordinate system in the 3D model of the part to be tested. ω ; Based on the RPS positioning points on the part to be tested, a six-point positioning detection fixture is made. The part to be tested is clamped using the positioning detection fixture, and the rotation angle of the secondary dendrite [100] of the part to be tested is measured using the Laue method. α , [001] Orientation deviation angle from the Z axis θ , where the reference direction of measurement is the Z axis, the reference plane is the YOZ plane, the X axis is perpendicular to the reference plane and points vertically upward, and the Y axis is horizontal and points to the right; Use an ultrasonic wall thickness tester to measure the standard sound velocity of standard plates in the [100] and [110] directions of the same alloy as the part to be tested, and obtain the longitudinal wave sound velocity value in the [100] direction. V _100 and the longitudinal wave speed in the [110] direction V _110 ; exist V _110 The wall thickness of the part to be tested is measured at the wall thickness measuring point under the condition of sonic velocity and calculated as d i， The angle ω , rotation angle α and deviation angle θ Substitute into the sound speed 3D model formula to obtain the sound speed after anisotropy calibration V ;in, The expression of the sound speed 3D model formula is: ； In the formula, ω, α、θ The unit is °; Then according to d i ’=d i * V / V _110 Calculate the exact wall thickness value. V _100 When measuring the wall thickness under sonic conditions, the formula d i ’=d i * V / V _110 In V _110 Replace with V _100 .

2. The method for ultrasonically detecting the wall thickness of cubic single crystal turbine blades according to claim 1, characterized in that: According to the coordinate position of the wall thickness point on the part drawing to be measured, a special positioning card is designed, and the wall thickness measurement point is marked on the part to be measured with the help of the positioning card.

3. The method for ultrasonically detecting the wall thickness of cubic single crystal turbine blades according to claim 1, characterized in that: The angle between the wall thickness measurement point and the Y coordinate axis of the theoretical coordinate system ω For measurement, observe along the Z axis, the counterclockwise angle is positive, the clockwise angle is negative, and the included angle is the angle between the measuring direction of the wall thickness point and the horizontal direction to the right.

4. The method for ultrasonically detecting the wall thickness of cubic single crystal turbine blades according to claim 1, characterized in that: The standard film orientation angle error is within ±3°.

5. The method for ultrasonically detecting the wall thickness of a cubic single crystal turbine blade according to any one of claims 1 to 4, characterized in that: The solution process of the sound speed 3D model formula is: For orientations with direction cosines l, m, n, the speed of sound is: ； According to the trigonometric function relationship, we can calculate: ； Will l 2 、m 2 、 2 Substituting into the sound speed formula, the 3D model formula of the sound speed is obtained, where l, m, and n are the direction cosines of the crystallographic coordinate axes [100], [010], and [001] respectively.

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