CN111259557B - Hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation - Google Patents

Hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation Download PDF

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CN111259557B
CN111259557B CN202010071467.0A CN202010071467A CN111259557B CN 111259557 B CN111259557 B CN 111259557B CN 202010071467 A CN202010071467 A CN 202010071467A CN 111259557 B CN111259557 B CN 111259557B
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崔康
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Abstract

The invention belongs to the technical field of investment precision casting of hollow turbine blades of aero-engines, and particularly relates to a hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation. The method comprises the following steps: 1) acquiring data of the inner and outer contour points of the actual hollow turbine blade; 2) three-dimensional iterative registration of the blade outline points and the design model; 3) calculating the pose drift amount of the ceramic core in the precision casting process; 4) calculating the reverse offset of the ceramic core; 5) reverse biasing the ceramic core design model; 6) adjusting the size of the ceramic core positioning element of the wax mould. Aiming at the serious problem of the wall thickness dimension of the hollow turbine blade of the aero-engine at present, from the angle of ceramic core position and posture regulation, the ceramic core positioning element inside the wax pattern die is regulated to change the space position and posture of the ceramic core inside the wax pattern, so that a core-shifting wax pattern is formed, and finally the purposes of improving the position matching relationship between the shell and the ceramic core and realizing the accurate control of the wall thickness precision of the hollow turbine blade are achieved.

Description

Hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation
Technical Field
The invention belongs to the technical field of investment precision casting of hollow turbine blades of aero-engines, and particularly relates to a hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation.
Background
Hollow turbine blades are used as core hot end parts of aircraft engines, and the forming precision of the hollow turbine blades has a direct influence on the performance and the service life of the engines. At present, the shape accuracy of the hollow turbine blade is mainly evaluated from two aspects of the outline and the wall thickness, wherein the wall thickness accuracy is a key index for ensuring the strength and the cooling efficiency of the blade. However, from the practical situation in the industry, the hollow turbine blade has serious wall thickness out-of-tolerance condition and low yield, and the temperature gradient change aggravation, strength reduction and stress concentration in the region with too thin wall thickness caused by wall thickness drift become the most main causes of the fatigue failure of the blade. Therefore, the research on the wall thickness precision control method of the hollow turbine blade has important significance for improving the qualification rate and the service life of the blade.
At present, the hollow turbine blade is generally manufactured by adopting an investment casting method due to the limitation of materials and structures. According to the process flow, the wall thickness precision of the hollow turbine blade is mainly inherited from a precision casting wax pattern, and is finally ensured through the matching relation of the positions of a shell and a ceramic core. In order to prevent the ceramic core from being broken under the action of strong pressure of molten metal casting and solidification, part of a positioning mechanism of the ceramic core in the shell is usually required to be set to be in a free end or sliding end positioning mode, and the positioning mode can cause the posture drift of the ceramic core in the precision casting process, so that the wall thickness of the blade is over-poor. In addition, the position and the posture of the ceramic core can be driven to drift by the non-uniform deformation of the shell in the solidification process, so that the position matching relationship between the ceramic core and the shell is changed, and the wall thickness of the blade is out of tolerance.
Disclosure of Invention
The invention provides a hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation, and aims to solve the problem that the wall thickness of a hollow turbine blade is out of tolerance due to insufficient ceramic core limiting and ceramic core pose drifting caused by non-uniform deformation of a shell in the conventional hollow turbine blade precision casting process.
In order to achieve the purpose, the invention adopts the following technical scheme:
the hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation comprises the following steps:
1) acquiring data of the inner and outer contour points of an actual hollow turbine blade;
2) and (3) three-dimensional iterative registration of the blade outline points and the design model: carrying out three-dimensional iterative registration on the obtained outline points of the actual hollow turbine blade and the outline curved surface of the blade design model, and then completing the synchronous movement of the outline points inside the actual hollow turbine blade by utilizing a space coordinate transformation matrix solved in the three-dimensional iterative registration process of the outline points;
3) calculating the drift amount of the ceramic core pose in the precision casting process: carrying out three-dimensional iterative registration on the actual hollow turbine blade inner contour points after the three-dimensional iterative registration and the ceramic core design model again, and then calculating the ceramic core pose drift amount in the precision casting process by utilizing a space coordinate transformation matrix solved in the three-dimensional iterative registration process;
4) calculating the reverse offset of the ceramic core;
5) reversely biasing the ceramic core design model;
6) and adjusting the size of the ceramic core positioning element of the wax mould.
Further, the specific method for acquiring the data of the inner and outer contour points of the actual hollow turbine blade in the step 1) comprises the following steps: and (3) performing key section scanning on the actual hollow turbine blade with the wall thickness deviation by utilizing industrial CT, then extracting the inner and outer contour points of the actual hollow turbine blade from a scanning gray scale image, and introducing the inner and outer contour points into three-dimensional drawing software.
And furthermore, the key sections are a plurality of sections which are positioned at the edge of the hollow turbine blade, have the maximum curve curvature value and are vertical to the stacking axis direction of the hollow turbine blade.
Further, the step 2) performs three-dimensional iterative registration on the obtained actual hollow turbine blade outline point and the blade design model outline curved surface, and then completes the synchronous movement of the actual hollow turbine blade internal outline point by using a space coordinate transformation matrix solved in the three-dimensional iterative registration process of the outline point, wherein the specific process is as follows:
suppose Pi∈R3×1(i is 1, …, N) is the position coordinates of the outline point of the actual hollow turbine blade outline, wherein N is the number of outline points, the outline points and the outline curved surface of the blade design model are subjected to three-dimensional iterative registration by using a classical ICP algorithm, if the outline points are close enough to the outline curved surface of the blade design model after k iterations, the three-dimensional iterative registration is finished, and the position coordinates of the outline point after the registration are finished
Figure BDA0002377421060000031
Calculated by the following formula:
Figure BDA0002377421060000032
in the formula (I), the compound is shown in the specification,
Figure BDA0002377421060000033
rotating a matrix and a translation vector for the outline point coordinate obtained in the jth three-dimensional iterative registration process;
reuse of
Figure BDA0002377421060000034
For the actual hollow turbine blade inner contour point Qf∈R3×1(f is 1, …, M) performing space coordinate transformation,completing the synchronous movement of the internal contour points of the actual hollow turbine blade, wherein M is the number of the internal contour points, and the position coordinates of the internal contour points of the moved actual hollow turbine blade
Figure BDA0002377421060000035
Calculated by the following formula:
Figure BDA0002377421060000036
furthermore, the outline point is close enough to the outline curved surface of the blade design model, specifically, the difference between the maximum distance between the outline point and the outline curved surface of the blade design model after the last two times of three-dimensional iterative registration is smaller than the registration precision tolerance xi1。
Further, in the step 3), the three-dimensional iterative registration is performed again on the actual hollow turbine blade inner contour points after the three-dimensional iterative registration and the ceramic core design model, and then the ceramic core pose drift amount in the precision casting process is calculated by using the space coordinate transformation matrix solved in the three-dimensional iterative registration process, namely: the ceramic core pose drifting spatial transformation matrix in the precision casting process comprises the following specific processes:
actual hollow turbine blade internal contour points subjected to three-dimensional iterative registration by utilizing ICP (inductively coupled plasma) algorithm
Figure BDA0002377421060000037
Carrying out three-dimensional iterative registration with the ceramic core design model, wherein if the internal contour point is close enough to the ceramic core design model after t iterations, the three-dimensional iterative registration is finished; next, the internal contour point coordinate rotation matrix obtained in the registration process is used
Figure BDA0002377421060000038
And translation vector
Figure BDA0002377421060000039
Calculating a ceramic core position and pose drift space transformation matrix in the precision casting process:
Figure BDA0002377421060000041
in the formula, Rw∈R3×3、Tw∈R3×1Respectively is a ceramic core pose drift rotation matrix and a translation vector in the precision casting process.
Furthermore, the internal contour point is close enough to the ceramic core design model, specifically, the difference between the maximum distance between the internal contour point and the ceramic core design model after the last two three-dimensional iterative registrations is less than the registration precision tolerance xi2。
Further, the step 4) of calculating the reverse offset of the ceramic core specifically comprises the following steps: according to the calculation result of the ceramic core pose drift, solving the ceramic core reverse offset inside the shell, namely: the reverse rotation matrix and the reverse translation vector, thereby the ceramic core after the precision casting drift reaches the theoretical position, wherein, the ceramic core reverse offset rotation matrix is: ru＝Rw -1The ceramic core reverse translation vector is: t isu＝-Tw。
Further, the step 5) of reversely biasing the ceramic core design model comprises the following specific processes:
and performing reverse bias on the ceramic core design model in three-dimensional modeling software by using the calculation result of the ceramic core reverse offset, wherein the bias content comprises ceramic core reverse translation and reverse rotation, and three translation components along an X, Y, Z axis required by the ceramic core reverse translation are ceramic core reverse translation vectors T respectivelyuAnd the rotation angle required for the pottery core to be reversely rotated is calculated by:
assuming that the reverse rotation of the ceramic core design model is realized by rotating a gamma angle around an X axis, then rotating a beta angle around a Y axis and finally rotating an alpha angle around a Z axis, according to the rigid body kinematics correlation theory, the following relations should be satisfied for alpha, beta and gamma:
Figure BDA0002377421060000042
in the formula, rmn(m is more than or equal to 1 and less than or equal to 3, n is more than or equal to 1 and less than or equal to 3) is the reverse deviation of the ceramic coreShift rotation matrix RuThe m-th row and n-th column elements are calculated from the equation, and the rotation angles α, β, γ are derived as follows:
Figure BDA0002377421060000043
α＝atan 2(r21/cosβ,r11/cosβ)
γ＝atan 2(r32/cosβ,r33/cosβ)。
further, the step 6) of adjusting the size of the ceramic core positioning element of the wax mould comprises the following specific steps:
according to a 6-point positioning principle, 6 positioning elements are utilized to complete the space positioning of the ceramic core in the wax mould, meanwhile, the ceramic core positioning elements are designed into a columnar step shape, and external threads are designed at the bottom of the ceramic core positioning elements to be connected with the mould; then, the protruding height of the positioning element in the wax mould cavity is adjusted through the threads, so that the posture of the ceramic core in the internal space of the wax mould cavity can be changed, the reverse deviation of the initial posture of the ceramic core in the wax mould cavity is further realized, and the size adjustment amount and the direction of the positioning element are determined through the following methods:
when designing a wax pattern mold, the top of the ceramic core positioning element is set to be hemispherical and kept in contact with the ceramic core design model, and assuming that the spherical surface diameter of the contact end of a certain positioning element is d, the coordinate vector of the spherical center is B0(ii) a Then, the contact-end hemisphere center B is first calculated0Initial distance s between the ceramic core design model surface after reverse bias0If the distance is greater than the contact hemisphere radius, then: when s is0If the positioning element moves in the direction rho-tau, and if the positioning element moves in the direction rho-tau, the movement is directed to the ceramic core along the axis of the positioning element; next, the length search increment Δ l is set while the initialization iteration increment g is 0, after which the following iterative calculation is performed:
Figure BDA0002377421060000051
finally, when the above iterative calculation is over, the positioning element resizing amount will be expressed as: Δ D is g · Δ l, and the adjustment direction is ρ.
Compared with the prior art, the invention has the following advantages:
1. aiming at the serious problem of the wall thickness dimension of the hollow turbine blade of the aero-engine, from the angle of adjusting and controlling the position and the posture of a ceramic core positioning element in a wax pattern mould, the space and the posture of the ceramic core in the wax pattern mould are changed, so that a core-shifting wax pattern is formed, and finally the purposes of improving the position matching relationship between the shell and the ceramic core and realizing the accurate control of the wall thickness precision of the hollow turbine blade are achieved.
2. According to the method, the actual CT scanning data of the inner and outer contours of the blade are utilized to calculate the ceramic core pose drift amount in the precision casting process, and then the ceramic core in the wax mould cavity is reversely offset based on the amount.
Drawings
FIG. 1 is an example of a hollow turbine blade for an aircraft engine to which embodiments of the present invention are directed;
FIG. 2 is a schematic diagram illustrating a process of obtaining data of inner and outer contour points of an actual hollow turbine blade according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a three-dimensional iterative registration process of a blade contour point and a design model in an embodiment of the invention;
FIG. 4 is a schematic view of the reverse shift process of the ceramic core in the embodiment of the present invention;
FIG. 5 is a schematic view of the assembly relationship between the wax pattern mold and the ceramic core positioning element according to the embodiment of the present invention;
fig. 6 is a schematic view illustrating the calculation of the adjustment amount of the ceramic core positioning element of the wax mold according to the embodiment of the present invention.
Detailed Description
Fig. 1 shows an example of a preferred aero-engine hollow turbine blade according to the present invention, having length and width dimensions: 138.7mm, 72.9 mm.
The method for inversely regulating the wall thickness deviation of the hollow turbine blade based on ceramic core positioning compensation according to the present invention is described in detail below with reference to the example of the hollow turbine blade.
1) Obtaining actual hollow turbine blade inner and outer contour point data
Performing key section scanning on an actual hollow turbine blade with wall thickness deviation by using industrial CT, wherein the key sections are 5 sections which are positioned at the edge of the blade and have the maximum curve curvature value and are vertical to the stacking axis direction of the blade, and are shown in FIG. 2; then, the inner and outer contour points of the blade are extracted from the scanning gray scale image and are led into three-dimensional modeling software UG.
2) Three-dimensional iterative registration of blade outline points and design model
And (3) carrying out three-dimensional iterative registration on the actual blade contour point and the blade design model contour curved surface by using a classical ICP algorithm until the contour point and the blade design model contour curved surface are close enough, namely: the difference between the outline point of the blade after the last two times of registration and the maximum distance of the blade design model is smaller than the registration precision tolerance xi1(ii) a Next, the spatial coordinate transformation matrix obtained in the registration process of the blade contour points is used to complete the synchronous movement of the actual blade inner contour points, as shown in fig. 3.
In this example, the registration accuracy tolerance ξ1The value is 0.01mm, so that after 52 times of iterative registration, the outline point is close to the blade design model enough, the registration is finished, and the position coordinates of the registered outline point are obtained
Figure BDA0002377421060000071
Calculated by the following formula:
Figure BDA0002377421060000072
in the formula, Pi∈R3×1(i is 1, …, N) is the position coordinate of the outline point of the actual hollow turbine blade,
Figure BDA0002377421060000073
rotating a matrix and a translation vector for the outline point coordinate obtained in the jth three-dimensional iterative registration process;
then, utilize
Figure BDA0002377421060000074
For the actual hollow turbine blade inner contour point Qf∈R3×1(f is 1, …, M) performing space coordinate transformation to complete synchronous movement of the internal contour points of the actual hollow turbine blade, wherein M is the number of the internal contour points, and the coordinate of the position of the internal contour points of the moved actual hollow turbine blade is obtained
Figure BDA0002377421060000075
Calculated by the following formula:
Figure BDA0002377421060000076
3) calculating the drift amount of the ceramic core pose in the precision casting process
Actual hollow turbine blade internal contour points subjected to three-dimensional iterative registration by utilizing ICP (inductively coupled plasma) algorithm
Figure BDA0002377421060000077
And carrying out three-dimensional iterative registration with the ceramic core design model again until the inner contour point is close to the ceramic core design model enough, namely: the difference between the point of the inner outline of the blade after the last registration for two times and the maximum distance of the ceramic core design model is smaller than the registration precision tolerance xi2(ii) a And then, calculating the drift amount of the ceramic core pose in the precision casting process by using the space coordinate transformation matrix solved in the three-dimensional iterative registration process.
In this example, the registration accuracy tolerance ξ2The value is 0.01mm, so that after 17 iterations, the inner contour point is close to the ceramic core design model sufficiently, and the registration is finished; next, the internal contour point coordinate rotation matrix obtained in the registration process is used
Figure BDA0002377421060000081
And translation vector
Figure BDA0002377421060000082
Calculating a ceramic core position and pose drift space transformation matrix in the precision casting process, namely:
Figure BDA0002377421060000083
in the formula, Rw∈R3×3、Tw∈R3×1Respectively is a ceramic core pose drift rotation matrix and a translation vector in the precision casting process.
4) Calculating the reverse offset of the ceramic core
According to the calculation result of the ceramic core pose drift, solving the ceramic core reverse offset inside the shell, namely: the reverse rotation matrix and the reverse translation vector, thereby the ceramic core after the precision casting drift reaches the theoretical position as far as possible, wherein, the ceramic core reverse offset rotation matrix is:
Figure BDA0002377421060000084
the ceramic core reverse translation vector is:
Figure BDA0002377421060000085
5) reverse bias ceramic core design model
Using the calculation result of the ceramic core reverse offset, the ceramic core design model is reversely biased in the three-dimensional modeling software UG, as shown in fig. 5, the bias content includes the ceramic core reverse translation and the reverse rotation, wherein three translation components along the X, Y, Z axis required for the ceramic core reverse translation are the ceramic core reverse translation vectors TuAnd the rotation angle required for the rotation of the ceramic core in the reverse direction is calculated by:
assuming that the reverse rotation of the ceramic core design model is realized by rotating a gamma angle around an X axis, then rotating a beta angle around a Y axis and finally rotating an alpha angle around a Z axis, according to the rigid body kinematics correlation theory, the following relations should be satisfied for alpha, beta and gamma:
Figure BDA0002377421060000091
in the formula, rmn(m is more than or equal to 1 and less than or equal to 3, n is more than or equal to 1 and less than or equal to 3) is a ceramic core reverse offset rotation matrix RuThe m-th row and the n-th column. According to this equation, the calculation results of the rotation angles α, β, γ are as follows:
Figure BDA0002377421060000092
α＝atan 2(r21/cosβ,r11/cosβ)＝0.213°
γ＝atan 2(r32/cosβ,r33/cosβ)＝0.096°。
6) adjusting the size of the ceramic core positioning element of the wax mould
According to a 6-point positioning principle, 6 positioning elements are utilized to complete the space positioning of the ceramic core in the wax mould, meanwhile, the ceramic core positioning elements are designed into a columnar step shape, and external threads are designed at the bottom of the ceramic core positioning elements to be connected with the mould; then, the extending height of the positioning element in the wax pattern mold cavity is adjusted through the screw thread, so that the posture of the ceramic core in the internal space of the wax pattern mold cavity can be changed, and further the initial posture reverse offset of the ceramic core in the wax pattern mold cavity is realized, wherein the size adjustment amount and the direction of the positioning element are determined through the following methods:
when designing a wax pattern mold, the top of the ceramic core positioning element is set to be hemispherical and kept in contact with the ceramic core design model, as shown in fig. 6, assuming that the spherical surface diameter of the contact end of a certain positioning element is d, and the coordinate vector of the spherical center is B0(ii) a Then, the contact-end hemisphere center B is first calculated0Initial distance s between the ceramic core design model surface after reverse offset0If the distance is greater than the contact hemisphere radius, then: when s0D/2, determining the moving direction of the positioning element as rho-tau, otherwise, making the positioning element move in the same direction as the p-tauThe element moving direction is rho ═ -tau, wherein tau is a unit vector which is along the axis of the positioning element and points to the ceramic core direction; next, the length search increment Δ l is set while the initialization iteration increment g is 0, after which the following iterative calculation is performed:
Figure BDA0002377421060000093
Figure BDA0002377421060000101
when the iterative calculation is finished, the size of the positioning element size adjustment amount is expressed as: Δ D is g · Δ l, and the adjustment direction is ρ.
The final 6 positioning element sizing amounts and directions determined by calculation are shown in table 1.
TABLE 1 adjustment amount and direction of ceramic core positioning element of wax mold
Figure BDA0002377421060000102
And finally, preparing an eccentric wax pattern by using the wax pattern mould adjusted by the positioning element, and obtaining the final example of the precision casting hollow turbine blade after finishing the subsequent process links of shell making, dewaxing, casting, shelling and the like. Compared with the actually measured blade, the maximum wall thickness deviation of the blade is reduced to 0.12mm from 0.33mm, so that the effectiveness of the method for regulating and controlling the wall thickness deviation of the hollow turbine blade is proved.
While there have been shown and described what are at present considered to be the essential features and advantages of the invention, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims (9)

1. The hollow turbine blade wall thickness deviation reverse regulation and control method based on ceramic core positioning compensation is characterized in that: the method comprises the following steps:
1) acquiring data of the inner and outer contour points of the actual hollow turbine blade;
2) and (3) three-dimensional iterative registration of the blade outline points and the design model: the three-dimensional iterative registration is carried out on the obtained outline points of the actual hollow turbine blade and the outline curved surface of the blade design model, then, a space coordinate transformation matrix solved in the three-dimensional iterative registration process of the outline points is utilized to complete the synchronous movement of the outline points in the actual hollow turbine blade, and the specific process is as follows:
suppose Pi∈R3×1(ii) a i is 1, …, N is the position coordinate of the outline point of the actual hollow turbine blade outline, wherein N is the number of the outline points, the outline points and the outline curved surface of the blade design model are subjected to three-dimensional iterative registration by utilizing a classical ICP algorithm, if the outline points are close enough to the outline curved surface of the blade design model after k iterations, the three-dimensional iterative registration is finished, and the position coordinate P of the registered outline point is the position coordinate of the outline pointi *Calculated by the following formula:
Figure FDA0003462245340000011
in the formula (I), the compound is shown in the specification,
Figure FDA0003462245340000012
rotating a matrix and a translation vector for the outline point coordinate obtained in the jth three-dimensional iterative registration process;
reuse of
Figure FDA0003462245340000013
For the actual hollow turbine blade inner contour point Qf∈R3×1And f is 1, …, M performs space coordinate transformation to finish the synchronous movement of the internal contour points of the actual hollow turbine blade, wherein M is the number of the internal contour points, and the coordinate of the position of the internal contour points of the moved actual hollow turbine blade is changed into the coordinate of the internal contour points
Figure FDA0003462245340000014
Calculated by the following formula:
Figure FDA0003462245340000015
3) calculating the drift amount of the ceramic core pose in the precision casting process: carrying out three-dimensional iterative registration on the actual hollow turbine blade inner contour points after the three-dimensional iterative registration and the ceramic core design model again, and then calculating the ceramic core pose drift amount in the precision casting process by utilizing a space coordinate transformation matrix solved in the three-dimensional iterative registration process;
4) calculating the reverse offset of the ceramic core;
5) reversely biasing the ceramic core design model;
6) and adjusting the size of the ceramic core positioning element of the wax mould.
2. The hollow turbine blade wall thickness deviation inverse regulation and control method based on ceramic core positioning compensation as claimed in claim 1, wherein: the specific method for acquiring the data of the internal and external outline points of the actual hollow turbine blade in the step 1) comprises the following steps: performing key section scanning on the actual hollow turbine blade with wall thickness deviation by utilizing industrial CT; and then, extracting the inner and outer contour points of the actual hollow turbine blade from the scanning gray scale map, and introducing the inner and outer contour points into three-dimensional drawing software.
3. The hollow turbine blade wall thickness deviation inverse regulation and control method based on ceramic core positioning compensation as claimed in claim 2, wherein: the key sections are a plurality of sections which are positioned at the edge of the hollow turbine blade and have the maximum curve curvature value and are vertical to the stacking axis direction of the hollow turbine blade.
4. The hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 1, wherein: the outline point is close enough to the outline curved surface of the blade design model, specifically, the difference of the maximum distance between the outline point and the outline curved surface of the blade design model after the last two times of three-dimensional iterative registration is less than the registration precision tolerance xi1。
5. The hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 1, wherein: and 3) carrying out three-dimensional iterative registration on the actual hollow turbine blade inner contour points subjected to three-dimensional iterative registration and the ceramic core design model again, and then calculating the ceramic core pose drift amount in the precision casting process by using a space coordinate transformation matrix solved in the three-dimensional iterative registration process, namely: the ceramic core pose drifting spatial transformation matrix in the precision casting process comprises the following specific processes:
actual hollow turbine blade internal contour points subjected to three-dimensional iterative registration by utilizing ICP (inductively coupled plasma) algorithm
Figure FDA0003462245340000021
Carrying out three-dimensional iterative registration with the ceramic core design model, wherein if the internal contour point is close enough to the ceramic core design model after t iterations, the three-dimensional iterative registration is finished; next, the internal contour point coordinate rotation matrix obtained in the registration process is used
Figure FDA0003462245340000022
And translation vector
Figure FDA0003462245340000023
Calculating a ceramic core position and pose drift space transformation matrix in the precision casting process:
Figure FDA0003462245340000031
in the formula, Rw∈R3×3、Tw∈R3×1Respectively is a ceramic core pose drift rotation matrix and a translation vector in the precision casting process.
6. The hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 5, wherein: the internal contour point is close enough to the ceramic core design model, specifically, the difference of the maximum distance between the internal contour point and the ceramic core design model after the last two three-dimensional iterative registrations is less than the registration precision tolerance xi2。
7. The hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 1, wherein: the step 4) of calculating the reverse offset of the ceramic core comprises the following specific steps: according to the calculation result of the ceramic core pose drift, solving the ceramic core reverse offset inside the shell, namely: the reverse rotation matrix and the reverse translation vector, thereby the ceramic core after the precision casting drift reaches the theoretical position, wherein, the ceramic core reverse offset rotation matrix is: r isu＝Rw -1The ceramic core reverse translation vector is: t isu＝-Tw。
8. The hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 1, wherein: the step 5) of reversely biasing the ceramic core design model comprises the following specific processes:
and reversely biasing the ceramic core design model in the three-dimensional modeling software by using the calculation result of the ceramic core reverse offset, wherein the biasing contents comprise ceramic core reverse translation and reverse rotation, and three times of the ceramic core reverse translation along the X, Y, Z axis are requiredEach translation component is a pottery core reverse translation vector TuAnd the rotation angle required for the pottery core to be reversely rotated is calculated by:
assuming that the reverse rotation of the ceramic core design model is realized by rotating a gamma angle around an X axis, then rotating a beta angle around a Y axis and finally rotating an alpha angle around a Z axis, according to the rigid body kinematics correlation theory, the following relations should be satisfied for alpha, beta and gamma:
Figure FDA0003462245340000032
in the formula, rmnM is more than or equal to 1 and less than or equal to 3, n is more than or equal to 1 and less than or equal to 3, and the ceramic core reverse offset rotation matrix R isuThe m-th row and n-th column elements are calculated from the equation, and the rotation angles α, β, γ are derived as follows:
Figure FDA0003462245340000041
α＝atan2(r21/cosβ,r11/cosβ)
γ＝atan2(r32/cosβ,r33/cosβ)。
9. the hollow turbine blade wall thickness deviation inverse control method based on ceramic core positioning compensation as claimed in claim 1, wherein: and 6) adjusting the size of the ceramic core positioning element of the wax mould, wherein the specific process is as follows:
according to a 6-point positioning principle, 6 positioning elements are utilized to complete the space positioning of the ceramic core in the wax mould, meanwhile, the ceramic core positioning elements are designed into a columnar step shape, and external threads are designed at the bottom of the ceramic core positioning elements to be connected with the mould; then, the protruding height of the positioning element in the wax mould cavity is adjusted through the threads, so that the posture of the ceramic core in the internal space of the wax mould cavity can be changed, the reverse deviation of the initial posture of the ceramic core in the wax mould cavity is further realized, and the size adjustment amount and the direction of the positioning element are determined through the following methods:
in the design of waxWhen the mould is formed, the top of the ceramic core positioning element is set to be hemispherical and keeps contact with the ceramic core design model, and if the spherical surface diameter of the contact end of a certain positioning element is d, the coordinate vector of the spherical center is B0(ii) a Then, the contact-end hemisphere center B is first calculated0Initial distance s between the ceramic core design model surface after reverse bias0If the distance is greater than the contact hemisphere radius, then: when s is0D/2, determining the moving direction of the positioning element as rho ═ τ, or else, making the moving direction of the positioning element as rho ═ τ, wherein τ is a unit vector which is along the axis of the positioning element and points to the ceramic core direction; next, the length search increment Δ l is set while the initialization iteration increment g is 0, after which the following iterative calculation is performed:
While|sgd/2| ≧ ε, ε is the convergence tolerance
{
g＝g+1；
Updating the position of the spherical center of the contact surface of the positioning element: bg＝B0+g·Δl·ρ；
Calculating the distance s between the contact surface sphere center of the positioning element and the ceramic core profileg；
}
Finally, when the above iterative calculation is over, the positioning element resizing amount will be expressed as: Δ D is g · Δ l, and the adjustment direction is ρ.
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