CN115307855A - Rotor blade high cycle fatigue test method and device considering centrifugal force effect - Google Patents

Rotor blade high cycle fatigue test method and device considering centrifugal force effect Download PDF

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CN115307855A
CN115307855A CN202210860106.3A CN202210860106A CN115307855A CN 115307855 A CN115307855 A CN 115307855A CN 202210860106 A CN202210860106 A CN 202210860106A CN 115307855 A CN115307855 A CN 115307855A
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blade
rotor blade
iron core
centrifugal force
vibration
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CN115307855B (en
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牛序铭
吴伟晶
彭秋洪
孙志刚
宋迎东
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M7/00—Vibration-testing of structures; Shock-testing of structures
    • G01M7/02—Vibration-testing by means of a shake table
    • G01M7/025—Measuring arrangements
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/10—Geometric CAD
    • G06F30/17—Mechanical parametric or variational design
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T17/00—Three dimensional [3D] modelling, e.g. data description of 3D objects
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/04—Ageing analysis or optimisation against ageing
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation

Abstract

The invention discloses a rotor blade high-cycle fatigue test method and a test device considering a centrifugal force effect, wherein the device comprises three modules, namely a classical vibration module, a blade clamping module and an electromagnet control module, the test method is characterized in that three-dimensional finite element software is utilized to determine the position of a dangerous point of a rotor blade and calculate the centrifugal force of the dangerous point, the electromagnet control module is utilized to use the attraction force generated by an electromagnetic field to equivalent the centrifugal force, a current controller is used to adjust the attraction force of the current control magnetic field, the blade clamping module is used to clamp and fix the rotor blade, the classical vibration module is utilized to test the rotor blade, and the high-cycle fatigue limit of the rotor blade is measured. The testing device provided by the invention has the advantages that the structure is optimized, the testing cost is low, the process is easy to control, and the centrifugal effect is considered, so that the stress state of the rotor blade during high-cycle vibration fatigue test is closer to the actual service environment, and the testing result is more accurate compared with the testing result obtained by a conventional testing means.

Description

Rotor blade high cycle fatigue test method and device considering centrifugal force effect
Technical Field
The invention relates to the technical field of rotor blades of aero-engines, in particular to a high-cycle fatigue test method and a high-cycle fatigue test device for rotor blades considering a centrifugal force effect.
Background
In addition to being subjected to centrifugal force, the engine rotor blades vibrate due to some uncertain factors (such as flow field unevenness) during service. When the rotating speed is constant, the stress value generated by the centrifugal force at each point in the blade basically does not change along with time, and can be simplified into constant stress; the stress generated by the vibration at each point of the blade is changed periodically along with the time, so that the symmetrical cyclic stress (namely the stress ratio is-1) can be simplified. The two forms of stress recombine at the same point in the blade, and the resulting composite stress can be considered an asymmetric cyclic stress (i.e., a stress ratio greater than 1). The composite stress is easier to generate fatigue cracks in the blade, and further causes a series of serious consequences such as blade fracture. Therefore, the rotor blade is one of the most critical parts in the engine structure, and the reliability of the rotor blade directly restricts the requirements of the engine for high thrust-weight ratio and high applicability.
A journal article of Tangling et al (university of air force) of Tangling et al (analysis and test of composite fatigue test loading system for certain type of engine fan blade) (analysis and test of composite fatigue test loading system for certain type of engine fan blade [ J ]. Mechanical strength, 2018,40 (01): 61-67) discloses a composite fatigue test loading system for engine fan blade. The blade is fixed on an excitation platform, and the vibration of the excitation platform is used for simulating high-cycle fatigue stress; and the root of the blade is connected by a steel cable, and the tension of the steel cable is used for simulating the low-cycle fatigue stress caused by centrifugal load. The scheme has the following defects: the tension of the wire rope only acts on the root of the blade, i.e.: the low cycle fatigue stress is applied only to the root of the blade, while the main body of the vibration, the blade body, is only subjected to the high cycle fatigue stress. The invention patent application of Chenliwei et al, the Beijing environmental research institute of Strength, "an aeroengine blade vibration fatigue test method based on an electric vibration table" (China, publication No. CN104748928A, publication date 2015.07.01) discloses an aeroengine blade vibration fatigue test method based on an electric vibration table. The vibration stress level of the maximum stress point of the blade is monitored by calibrating the maximum vibration stress response point and selecting an auxiliary monitoring point. The disadvantages are that: the centrifugal loads to which the rotor blades are subjected are not taken into account.
In order to improve the reliability of the rotor blade of the engine in actual work, a high-cycle fatigue test needs to be carried out before the blade is in service, the fatigue limit of the rotor blade is measured, and the bearing capacity of the rotor blade in actual work is predicted. However, it is difficult to equivalently replace centrifugal force with other types of loads in high cycle fatigue tests, and the most direct and effective scheme is to rotate the blades on a vibration table at high speed to realize the coupling of blade vibration and centrifugal force. However, the scheme is the same as the actual test run, so that the test cost is high, and the real-time monitoring of the centrifugal force in the test process is also a difficult problem.
Therefore, there is a need in the art for a method and an apparatus for testing high cycle fatigue of a rotor blade considering centrifugal force effect to solve the above problems. Therefore, a device and a method for testing the high-cycle fatigue of the rotor blade by considering the centrifugal force effect are designed to solve the problems.
Disclosure of Invention
The invention aims to solve the defect that the vibration fatigue test result of an engine blade is not accurate enough due to the fact that the stress of the aircraft engine blade vibration fatigue test is not considered comprehensively and the centrifugal load of the rotor blade is not considered in the prior art, and provides a high-cycle fatigue test device and a high-cycle fatigue test method of the rotor blade considering the centrifugal force effect.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high-cycle fatigue test method for a rotor blade considering centrifugal force effect comprises the following steps:
the first step is as follows: determining the position of a dangerous point of the rotor blade, establishing a three-dimensional model of the rotor blade by using three-dimensional software, carrying out modal analysis on the model of the rotor blade by using finite element software, and considering the centrifugal load action of the rotor blade to obtain the vibration mode of the rotor blade and the position of the dangerous point of the rotor blade, and recording the positions as a point P;
the second step: according to the geometry of the rotor blade, the centrifugal force of the point P at the rotating speed is calculated by adopting a centrifugal force calculation formula, wherein the centrifugal force calculation formula is as follows:
Figure BDA0003758000760000031
wherein rho is the density of the blade material, omega is the rotation angular velocity of the rotor, zk is the distance from the blade tip to the rotating shaft, zi is the distance from the blade root to the rotating shaft, Z is the projection of the distance from the point P to the rotating shaft in the blade height direction, and A (Z) is the sectional area of the blade where the point P is;
the third step: establishing a three-dimensional assembly model of a rotor blade, a blade tip resin chuck and a spherical armature, carrying out modal analysis on the three-dimensional assembly model by using finite element analysis software, giving an initial value of a blade tip cutting length L, considering the centrifugal load action (the rotating speed is n) of the rotor blade, obtaining the vibration mode of the three-dimensional assembly model and the maximum alternating stress position under first-order resonance, marking the vibration mode as a point P ', taking the blade tip cutting length L as a design variable, taking the position and the vibration mode of the point P as a target, establishing a multi-objective optimization program, giving the initial value of the blade tip cutting length L again when the position of the point P' is not similar to that of the point P and the vibration modes corresponding to the two points are not equal, calculating to obtain the vibration mode of the three-dimensional assembly model and the position P 'of the maximum alternating stress point under first-order resonance, and outputting the blade tip cutting length L which is the blade tip cutting length when the position of the point P' is similar to that the point P and the vibration modes corresponding to the two points are equal;
the fourth step: manufacturing a test piece, cutting off a material with the length of L at the blade tip of the rotor blade according to the blade tip cutting length L, forming a blade tip resin chuck through a casting process, immersing the blade tip of the rotor blade into molten epoxy resin in the casting process, cooling, fixing and forming, and bonding one side of the blade tip resin chuck and the rotor blade together to obtain the test piece;
the fifth step: the method comprises the following steps of (1) clamping a test piece and setting a magnetic field, wherein the test piece is fixed on a classical vibration module by using a blade clamping module, and the magnetic field setting is performed on the test piece by using an electromagnet control module;
and a sixth step: and calibrating the current value, starting a classical vibration module to set vibration, testing a test piece, and measuring the high cycle fatigue limit of the rotor blade.
Furthermore, the formula (1) integral is solved by adopting a numerical integration method, the blade is divided into n sections, the 0,1,2, \8230;, n, and n +1 sections are arranged from the blade tip to the blade root, the first section is the blade section between the 0 th section and the 1 st section, and the centrifugal force of the mass of the blade along the blade height direction of the section is as follows:
ΔF 1 ＝ρω 2 A m1 Z m1 ΔZ 1 (2)
in the formula, A m1 Denotes the average cross-sectional area, Z, of the first stage blade m1 Denotes the average coordinate, AZ, in the direction of the leaf height 1 Representing the absolute height of the first section of the blade;
Figure BDA0003758000760000041
Figure BDA0003758000760000051
ΔZ 1 ＝Z 0 -Z 1 (5)
in the above formula, Z 0 ，Z 1 The coordinates of the 0 th section and the 1 st section along the blade height direction, A 0 ，A 1 The cross-sectional areas of the 0 th cross-section and the 1 st cross-section respectively;
similarly, calculate Δ F 2 ，ΔF 3 ，……，ΔF n The section where the setpoint P is located is the ith section, the centrifugal force to which the point P is subjected being:
F iion ＝ΔF 1 +ΔF 2 +…+ΔF i (6)。
Further, in the fifth step, the test piece clamping is to fix the rabbet of the rotor blade of the test piece in the blade clamp of the blade clamping module by using a screw, and the method for setting the magnetic field of the test piece comprises the following steps:
step 1, pushing a spherical armature of an electromagnet control module into a groove of a blade tip resin chuck, and fixing the spherical armature by using a first positioning screw;
winding a coil on an annular iron core of the electromagnet control module, aligning a groove of the annular iron core to a boss of an iron core fixture of the electromagnet control module and pushing in the groove, and fixing the annular iron core on the iron core fixture by using a second positioning screw;
and 3, adjusting the position of the iron core clamp to enable the annular iron core to face the spherical armature, and fixing the iron core clamp base on an electric vibration table of the classical vibration module by using a screw.
Further, in the sixth step, the method for calibrating current includes:
step 1, firstly, a pressure sensor of an electromagnet control module is arranged on a contact surface of a groove of an annular iron core and a boss of an iron core clamp;
step 2, switching on coil current to generate a magnetic field, so that attraction force is generated between the spherical armature and the annular iron core, and the numerical value of the pressure sensor changes accordingly;
and 3, adjusting the current of the coil through a current controller to enable the value of the pressure sensor to be equal to the centrifugal force calculated in the second step, calibrating the current value at the moment, recording the current value as a current calibration value I, closing a power supply and taking out the pressure sensor.
Further, in the sixth step, the vibration is set as: and (3) turning on a power supply, adjusting the value of the coil current to enable the reading value of the coil current to be equal to the current calibration value I, setting the amplitude and frequency parameters of the classical vibration module, starting an electric vibration table and a power amplifier of the classical vibration module, and measuring the high cycle fatigue limit value of the test piece.
Further, the three-dimensional software includes any one or two of CAE software and UG software used in combination, and the finite element software includes any one or more of ABAQUS software, ANSYS software, or MSC software used in combination.
An experimental device applied to the method for testing the high cycle fatigue of the rotor blade considering the centrifugal force effect comprises the following steps:
a classical vibration module, the classical vibration module comprising: the computer is connected with the electric vibration table, the power amplifier and the laser displacement sensor through signal lines, and the power amplifier is connected with the electric vibration table through the signal lines;
a blade clamping module, the blade clamping module comprising: the blade clamp is fixedly arranged on one side of the electric vibration table and clamps a tenon for fastening a rotor blade;
an electromagnet control module, the electromagnet control module comprising: iron core anchor clamps, annular iron core, coil, spherical armature, pressure sensor and current controller, the installation of spherical armature is fixed on the apex resin chuck, the iron core anchor clamps are fixed one side of electrodynamic vibration platform, annular iron core's one end card is established and is fixed on the iron core anchor clamps, and the peripheral surface twines in order the coil, pressure sensor set up in on the contact surface of annular iron core and iron core anchor clamps, current controller with the coil links to each other.
Furthermore, the blade tip resin chuck is formed through a casting process, the blade tip of the rotor blade is immersed into molten epoxy resin in the casting process, the molten epoxy resin is cooled and fixed to be formed, one side of the blade tip resin chuck is bonded with the rotor blade, and the other side of the blade tip resin chuck is provided with a stepped first boss.
Furthermore, one end of the spherical armature is of a spherical curved surface structure, a first groove is formed in the middle of the spherical armature, and the first boss is inserted into the first groove and fastened by a first positioning screw.
Furthermore, the iron core clamp is formed by casting epoxy resin materials, a stepped second boss is arranged at one end of the iron core clamp, one side of the annular iron core is of an inwards concave curved surface structure and corresponds to a spherical curved surface of the spherical armature, a second groove is formed in the other side of the annular iron core, and the second boss is clamped in the second groove and fastened by a second positioning screw.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, an electromagnetic field is constructed on the basis of a classic fatigue testing machine, the magnetic attraction force generated by the magnetic field is used for being equivalent to the centrifugal force of a first-order resonance point, the magnitude of the magnetic force is controlled by current, the structure of the device is optimized, the device is easy to control, the testing process can be monitored in real time in the testing process, and effective support is provided for the experimental demonstration; the method provided by the invention can simulate the stress state of the rotor blade when the rotor blade vibrates under the actual service condition, the testing device provided by the invention is utilized to carry out the high cycle fatigue test measurement of the rotor blade, the stress analysis and the consideration are comprehensive, the centrifugal force and the vibration are simultaneously acted on the rotor blade, the defect of mutual interference influence is avoided, the obtained high cycle fatigue test result of the rotor blade is closer to the actual service condition, and the accuracy of the high cycle fatigue test result of the engine rotor blade is improved.
Drawings
FIG. 1 is a front view of the overall structure of the testing device according to the present invention;
FIG. 2 is a partial enlarged view of a blade clamping module and an electromagnet control module of the testing device of the present invention;
FIG. 3 is a top view of a blade clamping module and an electromagnet control module of the testing apparatus of the present invention;
FIG. 4 is an assembly view of the toroidal core and coil of the test apparatus of the present invention;
FIG. 5 is a front three-axis view of the core clamp of the test apparatus of the present invention;
FIG. 6 is a schematic view of a tip resin cartridge of the test apparatus of the present invention;
FIG. 7 is a schematic view of a ball armature of the test apparatus of the present invention;
FIG. 8 is a flow chart of a test method of the present invention for determining tip cutback length.
The reference numbers in the figures: 11. an electric vibration table; 12. a power amplifier; 13. a computer; 21. a rotor blade; 22. a blade clamp; 23. blade tip resin clamping heads; 31. an iron core clamp; 32. an annular iron core; 33. a coil; 34. a spherical armature; 41. a first set screw; 42. a second set screw; 51. a second groove; 52. a second boss; 53. a first boss; 54. a first groove; 61. a contact surface.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments.
The first embodiment is as follows:
based on the defects existing in the prior art, the invention provides a high cycle fatigue test method of a rotor blade considering the centrifugal force effect, which has the following principle:
carrying out modal analysis on the rotor blade three-dimensional model by using finite element analysis software, and taking the centrifugal load action (the rotating speed is n) into consideration to obtain the vibration mode of the rotor blade and the maximum alternating stress position under first-order resonance, and recording the position as a point P; the position of the point P can be regarded as the crack initiation position of the actual blade at the rotating speed, and the danger coefficient is the highest, so that in the test process, the high-cycle fatigue limit of the rotor considering the centrifugal force effect can be measured as long as the centrifugal force and the vibration mode of the point P are equivalent to the actual condition.
According to the geometry of the rotor blade, a centrifugal force calculation formula is adopted to calculate the centrifugal force of a point P at the rotating speed, a infinitesimal section with the height dZ is taken on the rotor blade, a infinitesimal body dXdYdZ is taken on the infinitesimal section, the area dXdY = dA of the infinitesimal body is made, and then the centrifugal force dF of the infinitesimal body is:
dF＝ρω 2 Z′dAdZ
wherein rho is the density of the blade material, omega is the rotation angular velocity of the rotor, Z 'is the distance between the center of gravity of the infinitesimal element and the rotation axis, and Z represents the projection of Z' in the direction of the blade height
Figure BDA0003758000760000091
In the formula (I), the compound is shown in the specification,
Figure BDA0003758000760000092
the angle formed by the Z' direction and the leaf height direction is shown.
The component of the infinitesimal centrifugal force dF in the direction of the blade height is:
Figure BDA0003758000760000093
the centrifugal force in the Z direction resulting from the mass of the vane micro-segment of cross-sectional area a (Z) is therefore:
Figure BDA0003758000760000101
in this way, the component of the centrifugal force of the blade mass above a certain cross section (Z = Zi) of the rotor blade in the blade height direction can be determined as:
Figure BDA0003758000760000102
in the formula, zk represents the distance from the blade tip to the rotation axis, zi represents the distance from the blade root to the rotation axis, Z represents the projection of the distance from the point P to the rotation axis in the blade height direction, and a (Z) represents the cross-sectional area of the blade where the point P is located.
Considering that the magnetic force and the centrifugal force have certain similarity and belong to field force, and the principle of magnetic force generation is simple, so that the attractive force generated by the electromagnetic field is equivalent to the centrifugal force; the electromagnet mainly comprises a coil, an iron core and an armature, wherein the iron core and the armature are made of soft iron or silicon steel, so that the electromagnet can be demagnetized immediately at the moment of power failure, the armature is fixed at the blade tip, the iron core and the coil are fixed opposite to the armature, the intensity of a magnetic field is controlled by adjusting the current, and the intensity of the magnetic force can be further controlled.
The armature is fixed on the blade tip to increase the weight of the blade tip, so that the vibration mode of the blade is increased, in order to ensure the vibration mode of the blade to be equivalent to the actual vibration mode, partial materials can be cut properly on the blade tip in advance to adjust the vibration frequency and the vibration mode after the armature is added, the length of the cut materials can be determined through a finite element method and a multi-objective optimization program together, a parameterized three-dimensional assembly model of the rotor blade and the armature is established, modal analysis is carried out on the assembly model through finite element analysis software, and the vibration mode of the three-dimensional assembly model and the maximum alternating stress position under first-order resonance are obtained by considering the centrifugal load action (the rotating speed is n) and are marked as P'. And establishing a multi-objective optimization program by taking the cutting length L of the blade tip as a design variable and the position and the vibration mode of the point P as targets, wherein when the position of P' and the corresponding vibration mode are matched with the point P, the output L is the cutting length of the blade tip.
Based on the above principle, as shown in fig. 8, the present embodiment provides a method for testing high cycle fatigue of a rotor blade considering centrifugal force effect, which includes the following specific steps:
the first step is as follows: determining the location of a hazard point for rotor blade 21; establishing a three-dimensional model of the rotor blade 21 by using three-dimensional modeling software (one or two of UG software or CAE software), then performing modal analysis on the rotor blade 21 model by using finite element software (any one or more of ABAQUS software, ANSYS software or MSC software), and taking the centrifugal load action (rotating speed n) into consideration to obtain the vibration mode of the rotor blade 21 and the maximum alternating stress position under first-order resonance, and marking the position as a point P.
The second step is that: according to the geometry of the rotor blade 21, the centrifugal force of the point P at this rotational speed is calculated using a centrifugal force calculation formula:
Figure BDA0003758000760000111
wherein rho is the density of the blade material, omega is the rotation angular velocity of the rotor, zk is the distance from the blade tip to the rotating shaft, zi is the distance from the blade root to the rotating shaft, Z is the projection of the distance from the point P to the rotating shaft in the blade height direction, and A (Z) is the sectional area of the blade where the point P is;
the formula (1) integral is solved by adopting a numerical integration method, the rotor blade 21 is divided into n sections, the 0,1,2, \8230;, n, and n +1 sections are arranged from the blade tip to the blade root, the first section is the blade section between the 0 th section and the 1 st section, and the centrifugal force of the mass of the blade along the blade height direction is as follows:
ΔF 1 ＝ρω 2 A m1 Z m1 ΔZ 1 (2)
in the formula, A m1 Denotes the average cross-sectional area, Z, of the first stage blade m1 Denotes the mean coordinate in the direction of the leaf height, Δ Z 1 Representing the absolute height of the first section of the blade;
Figure BDA0003758000760000121
Figure BDA0003758000760000122
ΔZ 1 ＝Z 0 -Z 1 (5)
in the above formula, Z 0 ，Z 1 The coordinates of the 0 th section and the 1 st section along the blade height direction, A 0 ，A 1 The cross-sectional areas of the 0 th cross-section and the 1 st cross-section respectively;
similarly, calculate Δ F 2 ，ΔF 3 ，……，ΔF n The section where the setpoint P is located is the ith section, the centrifugal force to which the point P is subjected being:
F i is away ＝ΔF 1 +ΔF 2 +…+ΔF i (6)。
The third step: establishing a three-dimensional assembly model of the rotor blade 21, the blade tip resin chuck 23 and the spherical armature 34, performing modal analysis on the three-dimensional assembly model by using finite element analysis software (any one or more of ABAQUS software, ANSYS software or MSC software), giving an initial value of a blade tip cutting length L, considering the centrifugal load action (the rotating speed is n) of the rotor blade 21, obtaining the vibration mode of the three-dimensional assembly model and the maximum alternating stress position under first-order resonance, marking the vibration mode as a point P ', taking the blade tip cutting length L as a design variable, and taking the position of the point P and the vibration mode as a target, establishing a multi-objective optimization program, when the position of the point P' is not similar to the position of the point P and the vibration modes corresponding to the two points are not equal, re-giving the initial value of the blade tip cutting length L, calculating to obtain the vibration mode of the three-dimensional assembly model and the position P 'of the maximum alternating stress point under the first-order resonance, and when the position of the point P' is similar to the point P and the vibration modes corresponding to the two points are equal, outputting the blade tip cutting length L which is the cut away length;
the fourth step: manufacturing a test piece, cutting off a material with the length L at the blade tip of the rotor blade 21 according to the blade tip cutting length L, forming a blade tip resin chuck 23 through a casting process, immersing the blade tip of the rotor blade 21 into molten epoxy resin in the casting process, cooling, fixing and forming, and bonding one side of the blade tip resin chuck 23 and the rotor blade 21 together to obtain the test piece;
the fifth step: the method comprises the steps of (1) clamping a test piece and setting a magnetic field, wherein the test piece is fixed on a classical vibration module by using a blade clamping module, a blade clamp 22 is fixed on one side of an electric vibration table 11 of the classical vibration module by using screws, and a tenon of a rotor blade 21 of the test piece is fixed in the blade clamp 22 of the blade clamping module by using screws; the electromagnet control module is utilized to set the magnetic field of the test piece by adopting the following steps:
step 1, pushing a spherical armature 34 of an electromagnet control module into a first boss 53 of a blade tip resin chuck 23, and fixing the first boss 51 by using a first positioning screw 41;
step 2, winding the coil 33 on the annular iron core 32 of the electromagnet control module, aligning the second groove 51 of the annular iron core 32 with the second boss 52 of the iron core clamp 31 of the electromagnet control module and pushing in, and fixing the annular iron core 32 on the iron core clamp 31 by using a second positioning screw 42;
and 3, adjusting the position of the iron core clamp 31 to enable the annular iron core 32 to be opposite to the spherical armature 34, and fixing the base of the iron core clamp 31 on the other side of the electric vibration table 11 of the classical vibration module by using screws.
And a sixth step: and current calibration and vibration setting, namely, installing a pressure sensor on a contact surface 61 of a second groove 51 of the annular iron core 32 and a second boss 52 of the iron core clamp 31, switching on a power supply, enabling the coil 33 to pass through current to generate a magnetic field, generating attraction between the spherical armature 34 and the annular iron core 32, changing the reading of the pressure sensor, adjusting the magnitude of the current passing through the coil 33 through a current controller, enabling the reading of the pressure sensor to be equal to the centrifugal force value of the point P calculated in the second step, recording the current magnitude at the moment as a current calibration value I, switching off the power supply, taking out the pressure sensor, switching on the power supply again, adjusting the value of the current of the coil 33 through the current controller to enable the reading of the current of the coil 33 to be equal to the current calibration value I, setting the amplitude and frequency parameters of the classical vibration module through a software system in the computer 13, starting an electric vibration table 11 and a power amplifier 12 of the classical vibration module, and measuring the high-cycle fatigue limit value of the test piece.
Example two:
the experimental device of the embodiment provides equipment support for the smooth implementation of the rotor blade high-cycle fatigue test method considering the centrifugal effect in the first embodiment, and comprises a classical vibration module, a blade clamping module and an electromagnet control module;
as shown in fig. 1, a classical vibration module includes: electric vibration table 11, power amplifier 12, computer 13 and laser displacement sensor, computer 13 and electric vibration table 11, power amplifier 12 and laser displacement sensor pass through the signal line and link to each other, and power amplifier 12 passes through the signal line with electric vibration table 11 and links to each other, installs the vibration control software of classic vibration module in the computer 13, and laser displacement sensor installs on classic vibration module for gather and to computer 13 transmission vibration signal.
As shown in fig. 2 and 6, the blade clamping module includes: the blade clamp 22 is fixedly installed on one side of the electric vibration table 11, the blade clamp 22 clamps and fastens a tenon of the rotor blade 21, a base of the blade clamp 22 is connected with the electric vibration table 11 through screws, and the number of the screws is 6; the blade tip resin chuck 23 is formed through a casting process, the blade tip of the rotor blade 21 is immersed into molten epoxy resin in the casting process, the blade tip resin chuck is cooled and fixed to be formed, one side of the blade tip resin chuck 23 is bonded with the rotor blade 21, and the other side of the blade tip resin chuck is provided with a stepped first boss 53.
As shown in fig. 2 to 5 and 7, the electromagnet control module includes: an iron core clamp 31, an annular iron core 32, a coil 33, a spherical armature 34, a pressure sensor and a current controller; the spherical armature 34 is fixedly arranged on the blade tip resin chuck 23, the iron core clamp 31 is fixedly arranged on one side of the electric vibration table 11, one end of the annular iron core 32 is clamped and fixed on the iron core clamp 31, the coil 33 is sequentially wound on the peripheral surface of the annular iron core 32 to form an electromagnet together with the annular iron core 32 and the spherical armature 34, the pressure sensor is arranged on a contact surface 61 of the annular iron core 32 and the iron core clamp 31, and the current controller is connected with the coil 33 and used for controlling the current of the coil 33 and indirectly controlling the generated magnetic attraction.
One end of the spherical armature 34 is in a spherical curved surface structure, the middle part of the spherical armature is provided with a first groove 54, and the first boss 53 is inserted in the first groove 54 and fastened by the first positioning screw 41.
The first groove 54 in the middle of the spherical armature 34 is matched with the stepped first boss 53 of the tip resin chuck 23, and the first boss 53 is inserted into the first groove 54 and fastened by the first positioning screw 41, so that the annular iron core 32 is prevented from bouncing in the vertical direction in the vibration process.
Iron core anchor clamps 31 adopts the casting of epoxy material shaping, 5 bolt holes have been opened to its base, link to each other with electric vibration platform 11 through the screw, iron core anchor clamps 31's one end (exposed core) is provided with stairstepping second boss 52, one side of annular iron core 32 is the curved surface structure of indent, and corresponding with the spherical curved surface of spherical armature 34, guarantee that the distance of both in the vibration process is unchangeable all the time, annular iron core 32's opposite side is provided with second recess 51, cooperate with the second boss 52 of stairstepping on iron core anchor clamps 31 and use, second boss 52 card is established in with second recess 51, and fasten with second set screw 42.
The method comprises the following steps that the blade tip of a rotor blade 21 with the blade tip cut of a material with the length of L and a blade tip resin chuck 23 are formed through a casting process, the blade tip of the rotor blade 21 is immersed into molten epoxy resin in the casting process, the molten epoxy resin is cooled and fixed to be formed, and one side of the blade tip resin chuck 23 is bonded with the rotor blade 21 to obtain a test piece; with the aid of the testing device, the tenon of the rotor blade 21 of the tested piece is fixed on the blade clamp 22, the spherical armature 34 of the electromagnet control module is pushed into the first boss 53 of the blade tip resin chuck 23, the first boss 51 is fixed by the first positioning screw 41, then the coil 33 is wound on the annular iron core 32 of the electromagnet control module, the second groove 51 of the annular iron core 32 is aligned with and pushed into the second boss 52 of the iron core clamp 31 of the electromagnet control module, and the annular iron core 32 is fixed on the iron core clamp 31 by the second positioning screw 42, so that the test piece can be installed by the testing device.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered as the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.

Claims (10)

1. A high cycle fatigue test method for a rotor blade considering centrifugal force effect is characterized by comprising the following steps:
the first step is as follows: determining the position of a dangerous point of the rotor blade, establishing a three-dimensional model of the rotor blade by using three-dimensional software, carrying out modal analysis on the model of the rotor blade by using finite element software, and considering the centrifugal load action of the rotor blade to obtain the vibration mode of the rotor blade and the position of the dangerous point of the rotor blade, and recording the positions as a point P;
the second step is that: according to the geometry of the rotor blade, the centrifugal force of the point P at the rotating speed is calculated by adopting a centrifugal force calculation formula, wherein the centrifugal force calculation formula is as follows:
Figure FDA0003758000750000011
wherein rho is the density of the blade material, omega is the rotation angular velocity of the rotor, zk is the distance from the blade tip to the rotating shaft, zi is the distance from the blade root to the rotating shaft, Z is the projection of the distance from the point P to the rotating shaft in the blade height direction, and A (Z) is the sectional area of the blade where the point P is;
the third step: establishing a three-dimensional assembly model of a rotor blade, a blade tip resin chuck and a spherical armature, carrying out modal analysis on the three-dimensional assembly model by using finite element analysis software, setting an initial value of a blade tip cutting length L, considering the centrifugal load effect of the rotor blade to obtain the vibration mode of the three-dimensional assembly model and the maximum alternating stress position under first-order resonance, recording as a point P ', setting a multi-objective optimization program by taking the blade tip cutting length L as a design variable and the position and the vibration mode of the point P as targets, resetting the initial value of the blade tip cutting length L when the position of the point P' is not close to that of the point P and the vibration modes corresponding to the two points are not equal, and calculating to obtain the vibration mode of the three-dimensional assembly model and the position P 'of the maximum alternating stress point under the first-order resonance, wherein the output blade tip cutting length L is the cut length of the blade tip when the position of the point P' is close to that the position of the point P and the vibration modes corresponding to the two points are equal;
the fourth step: manufacturing a test piece, cutting a material with the length L at the blade tip of the rotor blade according to the blade tip cutting length L, forming a blade tip resin chuck through a casting process, immersing the blade tip of the rotor blade into molten epoxy resin in the casting process, cooling, fixing and forming, and bonding one side of the blade tip resin chuck and the rotor blade together to obtain the test piece;
the fifth step: the method comprises the following steps of (1) clamping a test piece and setting a magnetic field, wherein the test piece is fixed on a classical vibration module by using a blade clamping module, and the magnetic field setting is performed on the test piece by using an electromagnet control module;
and a sixth step: and calibrating the current value, starting a classical vibration module to set vibration, testing a test piece, and measuring the high cycle fatigue limit of the rotor blade.
2. The method for testing the high cycle fatigue of the rotor blade considering the centrifugal force effect according to claim 1, wherein the formula (1) integral is solved by a numerical integration method, the blade is divided into n sections, and the 0,1,2, \8230;, n +1 sections are arranged from the blade tip to the blade root, the first section is the section of the blade between the 0 th section and the 1 st section, and the centrifugal force of the mass of the blade along the height direction of the blade is:
ΔF 1 ＝ρω 2 A m1 Z m1 ΔZ 1 (2)
in the formula, A m1 Denotes the average cross-sectional area, Z, of the first stage blade m1 Denotes the mean coordinate in the direction of the leaf height, Δ Z 1 Representing the absolute height of the first section of the blade;
Figure FDA0003758000750000021
Figure FDA0003758000750000022
ΔZ 1 ＝Z 0 -Z 1 (5)
in the above formula, Z 0 ，Z 1 The coordinates of the 0 th section and the 1 st section along the blade height direction, A 0 ，A 1 The cross-sectional areas of the 0 th cross-section and the 1 st cross-section respectively;
similarly, calculate Δ F 2 ，ΔF 3 ，……，ΔF n The section where the setpoint P is located is the ith section, the centrifugal force to which the point P is subjected being:
F iion ＝ΔF 1 +ΔF 2 +…+ΔF i (6)。
3. The method for testing the high-cycle fatigue of the rotor blade considering the centrifugal force effect according to claim 1, wherein in the fifth step, the test piece clamping is to fix the rabbet of the rotor blade of the test piece in the blade clamp of the blade clamping module by using a screw, and the method for setting the magnetic field of the test piece comprises the following steps:
step 1, pushing a spherical armature of an electromagnet control module into a groove of a blade tip resin chuck, and fixing the spherical armature by using a first positioning screw;
step 2, winding the coil on an annular iron core of the electromagnet control module, aligning a groove of the annular iron core with a boss of an iron core fixture of the electromagnet control module and pushing the boss in the groove, and fixing the annular iron core on the iron core fixture by using a second positioning screw;
and 3, adjusting the position of the iron core clamp to enable the annular iron core to face the spherical armature, and fixing the iron core clamp base on an electric vibration table of the classical vibration module by using a screw.
4. The method for testing high cycle fatigue of a rotor blade in consideration of centrifugal force effect as claimed in claim 3, wherein in the sixth step, the method for calibrating current comprises:
step 1, firstly, a pressure sensor of an electromagnet control module is arranged on a contact surface of a groove of an annular iron core and a boss of an iron core clamp;
step 2, switching on coil current to generate a magnetic field, so that attraction force is generated between the spherical armature and the annular iron core, and the numerical value of the pressure sensor changes accordingly;
and 3, adjusting the current of the coil through the current controller to enable the numerical value of the pressure sensor to be equal to the centrifugal force calculated in the second step, calibrating the current at the moment, recording the current as a current calibration value I, closing the power supply and taking out the pressure sensor.
5. The method for testing high cycle fatigue of a rotor blade in consideration of centrifugal force effect as claimed in claim 4, wherein in the sixth step, the vibration is set as: and turning on a power supply, adjusting the value of the coil current to enable the reading value of the coil current to be equal to the current calibration value I, setting the amplitude and frequency parameters of the classical vibration module, starting an electric vibration table and a power amplifier of the classical vibration module, and measuring the high cycle fatigue limit value of the test piece.
6. The method of claim 1, wherein the three-dimensional software comprises any one or two of CAE software and UG software, and the finite element software comprises any one or more of ABAQUS software, ANSYS software or MSC software.
7. An experimental device applied to the method for testing the high-cycle fatigue of the rotor blade considering the centrifugal force effect according to any one of claims 1 and 3 to 6, wherein the experimental device comprises:
a classical vibration module, the classical vibration module comprising: the device comprises an electric vibration table (11), a power amplifier (12), a computer (13) and a laser displacement sensor, wherein the computer (13) is connected with the electric vibration table (11), the power amplifier (12) and the laser displacement sensor through signal lines, and the power amplifier (12) is connected with the electric vibration table (11) through the signal lines;
a blade clamping module, the blade clamping module comprising: the blade clamp (22) is fixedly installed on one side of the electric vibration table (11), and the blade clamp (22) clamps a tenon for fastening a rotor blade (21);
an electromagnet control module, the electromagnet control module comprising: iron core anchor clamps (31), annular iron core (32), coil (33), spherical armature (34), pressure sensor and current controller, spherical armature (34) installation is fixed on apex resin chuck (23), iron core anchor clamps (31) are fixed one side of electric vibration platform (11), the one end card of annular iron core (32) is established and is fixed on iron core anchor clamps (31), and the peripheral surface twines in order coil (33), pressure sensor set up in on contact surface (61) of annular iron core (32) and iron core anchor clamps (31), current controller with coil (33) link to each other.
8. The experimental device as claimed in claim 7, wherein the tip resin clamp (23) is formed by a casting process, the tip of the rotor blade (21) is immersed into molten epoxy resin during the casting process and is cooled and fixed to be formed, one side of the tip resin clamp (23) is bonded with the rotor blade (21), and the other side of the tip resin clamp is provided with a stepped first boss (53).
9. The experimental device as claimed in claim 8, wherein one end of the spherical armature (34) is in a spherical curved surface structure, a first groove (54) is formed in the middle of the spherical armature, and the first boss (53) is inserted into the first groove (54) and fastened by a first positioning screw (41).
10. The experimental device according to claim 7, wherein the iron core fixture (31) is molded by casting epoxy resin material, one end of the iron core fixture is provided with a second stepped boss (52), one side of the annular iron core (32) is of a concave curved surface structure and corresponds to the spherical curved surface of the spherical armature (34), the other side of the annular iron core is provided with a second groove (51), and the second boss (52) is clamped in the second groove (51) and is fastened by a second positioning screw (42).
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