CN112683476B - Turbofan engine fan blade multi-axis loading fatigue test stand and method - Google Patents
Turbofan engine fan blade multi-axis loading fatigue test stand and method Download PDFInfo
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- CN112683476B CN112683476B CN202011637346.4A CN202011637346A CN112683476B CN 112683476 B CN112683476 B CN 112683476B CN 202011637346 A CN202011637346 A CN 202011637346A CN 112683476 B CN112683476 B CN 112683476B
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Abstract
The invention relates to a multi-axis loading fatigue test bed and a method for a fan blade of a turbofan engine, wherein the test bed comprises the following steps: the device comprises a test piece, a vertical loading device, a horizontal loading device, a disturbance loading device, a crack image detection device, a hydraulic system, an electric control system and upper computer software; the test piece comprises a blade and turbine disk test piece, the invention breaks through the limit of space size on the existing single-shaft material testing machine, and the multi-shaft loading capability of the test piece is expanded by adding a horizontal loading device and a disturbance loading device, so that the actual loading form of the root part of the fan blade can be effectively simulated; the invention can control the application of the horizontal load and the disturbance load of the test piece in the fatigue test process, and can realize the measurement of parameters such as stress strain and the like of the test piece in the fatigue crack generation process by pasting a strain gauge on the surface of the test piece and combining the image processing technology.
Description
Technical Field
The invention relates to the technical field of aero-engines, in particular to a multi-axis loading fatigue test bed and a method for a dovetail tenon at the root of a fan blade of a turbofan engine.
Background
The fan blade is an important component of a turbofan engine, which is in its most forward position in the engine. The shape of the fan blades is complex, and the working environment is severe; the blades are subjected to various complex load effects such as centrifugal load and complex airflow disturbance generated by high-speed rotation during operation [1-2 ]. The current aerospace technology is developed rapidly, the large bypass ratio and the large thrust-weight ratio of a turbofan engine are outstanding, the requirements on the reliability of fan blades are continuously improved, and the failure problems of various blades are more and more prominent [3 ]. The fracture position of a fan blade is almost positioned near the root part of the blade, in the structural design of the turbofan engine, a dovetail joint structure is formed by a tenon at the root part of the fan blade and a mortise on a turbine disc, and after the blade is loaded, a contact surface between the tenon and the turbine slot is in a micro-motion state [4 ].
In the process of taking off, cruising and finally landing of an airplane, the working state of an engine is changed to a certain extent, centrifugal load enables the tenon of a blade to generate stress with frequency intersection, meanwhile, vibration and airflow disturbance force generated by the operation of the engine can cause the vibration stress, but the stress is characterized by small amplitude and high frequency [5], as the root shape and the load environment of the blade of the engine are complex, under the micro-motion condition that the tenon of the root of the blade is connected with a turbine disc groove, the contact area between the root of the blade and the turbine disc groove is generally in a multi-axis stress state, and in recent years, the international fan blade failure analysis statistical data also shows that the fatigue failure reason of the root of the blade is almost caused by the multi-axis load action of high-speed centrifugal force and abnormal vibration stress.
At present, more uniaxial loading fatigue failure researches aiming at a tenon connecting structure between the root of a fan blade of an engine and a mortise of a turbine disc are developed at home and abroad.
[1] Gaoqing, research on technical life of rotor blades of compressor of certain series of engines [ J ]. aeroengine, 2008(03):22-26.
[2] Zhao Nu, multiaxial low cycle fatigue study of single crystal blade of aeroengine [ D ]. Zhongnan university, 2011.
[3] Yang Ruiyao. engine fan blade fatigue life calculation and vibration characteristics analysis [ D ]. university of electronic technology, 2014.
[4]Orly Leivia,Effects of shear load on fretting fatigue behavior of Ti-6Al-4V,Doctoral dissertation,University of Dayton，2003.
[5] Analysis and test of Tangling, Shangbeilin, Gaoxingwei, Chenpengcfei, Yi Shipeng and certain type of engine fan blade composite fatigue test loading system [ J ]. mechanical strength, 2018,40(01):61-67.
[6]BERETTA S,ERNASCONI A,ARBONI M.Fatigue assessment of root failures in HSLA steel welded joints:Acomparison among local approaches[J].International Journal of Fatigue,009,1(1):102-110.
Disclosure of Invention
The invention solves the problems: aiming at the defects of the existing loading form, the multi-axis loading fatigue test bed and the method for the fan blade of the turbofan engine are provided, so that the loading form of the root of the fan blade can be effectively simulated; and the monitoring of the fatigue crack generation process is realized by combining an image processing technology.
The technical scheme of the invention is as follows: a turbofan engine fan blade multi-axis loading fatigue test bench, comprising:
the test piece consists of a blade test piece and a turbine disc test piece, the blade test piece effectively simulates the geometry and the material characteristics of the root of the fan blade, and the blade test piece and the turbine disc test piece form a dovetail joint structure. The geometric shape and size of the test piece can be adjusted in a certain range, and the material composition and surface spraying treatment of the test piece can be selected according to the loading test requirements. The turbine disk test piece bilateral symmetry design guarantees that the load that the turbine disk test piece received when carrying out tensile loading about equals, and the upper, left and right processing through-hole of turbine disk test piece to be connected with anchor clamps conveniently.
The vertical loading device outputs a load in the vertical direction to realize the tension loading on the root part of the blade test piece and mainly comprises accessories such as a material fatigue testing machine, an upper hydraulic chuck, a lower hydraulic chuck, a vertical test piece clamp and the like; the vertical direction test piece jig includes: the device comprises a clamp on the turbine disc, a clamp for the blade test piece and a switching clamp. The upper hydraulic chuck and the lower hydraulic chuck are positioned on the same vertical axis; the upper hydraulic chuck fixes a turbine disc test piece through a turbine disc upper clamp, the lower hydraulic chuck is connected with a blade test piece through a blade test piece clamp, and normal centrifugal force borne by the blade test piece can be effectively simulated through loading in the vertical direction; the material fatigue testing machine is characterized in that the American MTS810 type hydraulic drive material testing machine is selected as the material fatigue testing machine, the load of a main machine of the material fatigue testing machine is +/-250 kN, the lower hydraulic chuck is an accessory of the material fatigue testing machine, and the material fatigue testing machine further comprises a cross beam, a stand column, a rack and a vertical loading hydraulic actuator.
The horizontal loading device is used for symmetrically outputting horizontal direction loads, tension loading of a turbine disc test piece is achieved, dovetail groove expansion caused by loading of the turbine disc during actual operation of an engine is simulated, and the horizontal loading device is installed on a rack of the material fatigue test piece and is lower than a cross beam in height. The loading device mainly comprises a horizontal hydraulic loading actuator, a loading chuck, a turbine disc test piece horizontal clamp, a horizontal loading platform and the like; horizontal loading platform through with material fatigue testing machine about the stand be connected and fix on the take the altitude, horizontal hydraulic pressure loading actuator install horizontal loading platform on, and bilateral symmetry distributes in perpendicular loading device both sides, horizontal hydraulic pressure loading actuator (two) are respectively through horizontal loading chuck connection test piece anchor clamps, the test piece anchor clamps other end is connected through round pin axle turbine dish test piece, the accessible pastes the foil gage and realizes the detection to horizontal output load on the test piece.
Furthermore, the horizontal loading platform consists of accessories such as a bottom plate, a fixed flange, a pull rod, a bottom plate supporting sleeve frame and the like. The bottom plate supports the sleeve frame and is respectively sleeved with the left and right stand columns, the bottom surface of the sleeve is tightly attached to the working surface of the hydraulic material testing machine, the fixed plate is welded on the sleeve, a threaded hole is formed in the fixed plate, the bottom plate is connected with the square supporting block through a bolt, and the bottom plate is fixed at a space position which is a certain height away from the working surface of the hydraulic material testing machine; the two fixing flanges (divided into a left part and a right part) are respectively fixed on the bottom plate through bolts, the horizontal hydraulic loading actuator is arranged on the flanges through bolts, two counter bores are processed on the fixing flanges, and the left fixing flange and the right fixing flange are respectively connected through the pull rod to form a geometric closed force system frame.
The disturbance loading unit outputs disturbance load to the root of the blade, so that vibration load borne by the blade due to airflow disturbance under the actual working condition is simulated, the disturbance loading device is installed on the working surface of the material fatigue testing machine, and the load of the disturbance loading device acts on the root of a blade test piece. The base is installed on a working face of a material fatigue testing machine, the geometric center of the base and a vertical loading device are on a central line, the loading frame is sleeved on a handle portion of a blade test piece and fixed through a pin, the other end of the loading frame is connected with the electric push rod, the electric push rod is fixed on the base, the electric push rod drives the loading frame to slightly move through reciprocating motion of a lead screw, and disturbance loading on the blade test piece is achieved.
The hydraulic system mainly comprises a filter, a motor, a variable plunger pump, a check valve, a two-position four-way electromagnetic directional valve, an energy accumulator, a stop valve, an energy accumulator control valve group, a pilot type pressure reducing valve, an H-shaped three-position four-way electromagnetic directional valve, a one-way throttle valve, a hydraulic control check valve, a horizontal loading hydraulic cylinder, a vertical loading hydraulic cylinder, a cooler, an oil tank, an electromagnetic overflow valve, a pressure sensor, a pressure gauge and the like, and can realize pressure maintaining and lowest power operation design.
In the hydraulic system, the main pressure of the whole system can be adjusted through a pilot overflow valve, and as high-pressure oil directly enters a vertical loading loop after passing through a one-way valve, the system pressure of a vertical loading unit reaches a preset value by adjusting the set value of an electromagnetic overflow valve; the horizontal load pressure is steplessly adjusted by the pilot type pressure reducing valve 1, and different working pressures are adjusted by matching the overflow valve and the pressure reducing valve, so that the load requirement of the test bed is met.
The crack image detection device mainly comprises accessories such as a CCD camera, an illumination light source and the like; the CCD camera is arranged on the camera support, an illumination light source is arranged on the surface of the test piece, the CCD camera continuously shoots the test piece during fatigue loading, and the pictures are transmitted to the upper computer control software. Before the test, the surface of a test piece is required to be subjected to speckle spraying treatment, the speckles at the root of a blade test piece are shot by a CCD camera, a lighting source irradiates light onto the test piece, the light is reflected by the test piece and is imaged on a CCD camera, and then the CCD camera collects images and sends the images into upper computer software for analysis and treatment.
The electric control system can be connected with the hydraulic system and the disturbance loading system through signal lines, provides power output interfaces of required types for each loading system, can control the work of each function of the hydraulic system and the disturbance loading system, and can collect circuit signals on the strain gauge and perform certain signal processing. The electric control system is arranged in the electric control cabinet, and the electric control cabinet is arranged on the horizontal ground.
The upper computer special software is used for setting each parameter of the test loading and controlling the electric control system to realize the control of each loading device; the software can control the CCD camera to photograph the test piece, detect the crack image, calculate the fatigue crack tip displacement and measure the strain field to give an analysis result.
The invention discloses a multi-axis loading fatigue test method for a fan blade of a turbofan engine, which comprises the following operation steps:
step 1: and (3) treating the surface material of the test piece: according to different test requirements, whether surface material treatment is carried out on a tenon joint surface formed by the root parts of the turbine disk test piece and the blade test piece or not and what surface treatment is carried out can be selected;
step 2: and (3) spraying speckles on the test piece: the CCD camera is used for photographing the loaded test piece, the strain and stress in the loading process can be conveniently calculated, the surface of the turbine disc and the blade test piece is required to be subjected to speckle spraying treatment, and speckles can be distributed uniformly and clearly and are easy to identify by the CCD camera;
and step 3: installing a test piece: firstly, a turbine disc test piece is installed in an upper clamp through a pin shaft, the upper clamp is fixed to a hydraulic upper chuck, the height of a cross beam of a hydraulic material testing machine is adjusted, the turbine disc test piece is in a state to be clamped, a lower clamp is connected to a blade test piece through the pin shaft, then the root of the blade test piece is installed in a dovetail groove in the turbine disc test piece, after the lower clamp is fixed through the hydraulic lower chuck, a vertical loading hydraulic actuator is started in advance, the blade test piece is subjected to pretightening force, and the height of the cross beam and the stroke size of the hydraulic actuator are respectively adjusted, so that the test piece which is integrally clamped is in a horizontal loading height; respectively installing a left clamp and a right clamp on two sides of the turbine disc test piece, and respectively connecting the clamps to the tail end chuck parts of the left hydraulic actuator and the right hydraulic actuator; then, performing a preloading test, wherein the test mainly comprises the step of adjusting the matching relation between test pieces to enable the root of a blade test piece and the dovetail groove part of the turbine disk to be in a micro-motion state;
and 4, step 4: mounting crack image detection device
Erecting an illumination light source beside the test bed, wherein the illumination light source and the normal line of the surface of the blade test piece close to the root part are irradiated at an angle of 0-90 degrees, the light source is required to be completely and clearly irradiated on the surface of the test piece, the reflection phenomenon does not occur on the surface of the blade test piece close to the root part, and the dovetail joint can be clearly seen; erecting a camera support on a horizontal ground close to the hydraulic fatigue testing machine, fixing a CCD camera on the support, and adjusting the focal length of the camera;
and 5: setting test parameters
Setting vertical loading parameters, horizontal loading parameters and test termination conditions on special software of the upper computer respectively, wherein the loading parameters comprise loading forms in horizontal and vertical directions and loading force, and the loading forms comprise static loading and unidirectional pulsating loading; because the test can be loaded in the horizontal and vertical directions, the sequence of horizontal and vertical loading also needs to be set on the special software of the upper computer; after the parameters are set, preparing a preloading test;
step 6: test load application and feedback control
Installing resistance strain gauges on the surfaces of a turbine disc test piece and a blade test piece, wherein the resistance strain gauges can collect strain electric signals in the test piece loading process and transmit the strain electric signals into an electric control cabinet for processing to obtain the load output in the vertical direction and the horizontal direction, an electric control system uploads the load signals output in the vertical direction and the horizontal direction to an upper computer for storage and processing, comparison is carried out according to preset loading parameters, feedback output signals are sent to an electric control system, and the electric control system then controls each hydraulic loading actuator to work;
and 7: in the preloading test, a tester needs to carefully observe whether the test piece has large deformation or damage of the sending tenon connecting structure in the loading process, and if the large deformation or damage occurs, the test is immediately stopped; after the test piece is preloaded normally, setting working parameters of the CCD camera on special software of the upper computer, wherein the working parameters comprise: the frequency of taking pictures, whether the image is preprocessed or not, and the like; focusing of the camera is adjusted again, so that the image of the tenon joint part of the root of the blade is displayed on a special software interface of the upper computer clearly in real time;
and 8: and (4) terminating the test: and the upper computer analyzes whether the acquired image has large-deformation cracks in real time through monitoring the signals of the strain gauge sensors in all directions on the surface of the test piece and the special software of the upper computer through a DIC detection algorithm, judges whether the test piece reaches the termination condition set by the test, and then terminates the test.
Compared with the prior art, the invention has the advantages that:
(1) compared with the existing single-shaft fatigue testing machine, the system can output vertical and horizontal direction and vibration load at the same time by adding the horizontal and disturbance loading devices on the existing single-shaft testing machine, and can effectively simulate the tension-bending-vibration multi-shaft fatigue load in a stressed state in service of a turbofan engine blade test piece;
(2) the horizontal loading device of the fatigue loading test bed is arranged into a closed mechanical frame, so that the horizontal loading load only acts in the horizontal loading platform, the vertical column cannot be impacted, the normal work of the vertical column is ensured, and the horizontal loading device is stably fixed on a single-shaft material testing machine;
(3) the test bed hydraulic system runs at low power and can output load in an adjustable mode, the pressure signal is monitored in real time by using the sensor, the hydraulic system can keep loading pressure and intermittently unload the hydraulic system by adjusting the state of a relevant electromagnetic valve and using a negative feedback principle, and therefore power loss is reduced;
(4) the invention can test various test piece forms (such as plate-shaped test pieces and bars) in various loading forms (such as single shaft, double shafts and multiple shafts), and the application range of the testing machine is wider;
(5) the system has a fatigue crack image detection system, and has the characteristics of real time, intuition, accuracy, easy acquisition and the like. The fatigue crack propagation condition can be detected in real time by taking pictures through the CCD camera, the crack generation process can be detected, and the small crack initiation position can be predefined in the special software of the upper computer for monitoring.
Drawings
FIG. 1 is a schematic view of a multi-axis loading fatigue test bed for a turbofan engine fan blade of the present invention;
FIG. 2 is a schematic view of a loading structure of a multi-axis loading fatigue test bed for a blade according to the present invention;
FIG. 3 is a schematic diagram of a test piece designed according to the present invention;
FIG. 4 is a schematic view of a vertical loading unit of the fatigue test stand of the present invention;
FIG. 5 is a schematic view of a clamp Y-adapter of the present invention;
FIG. 6 is a schematic view of an upper fixture of the present invention;
FIG. 7 is a schematic view of a lower clamp of the present invention;
FIG. 8 is a schematic view of a horizontal clamp of the present invention;
FIG. 9 is a schematic view of a test piece being clamped into a fixture in accordance with the present invention;
FIG. 10 is a view of the horizontal loading device of the fatigue test stand of the present invention;
FIG. 11 is a schematic view of a stationary locking sleeve of the fatigue test rig of the present invention;
FIG. 12 is a schematic view of a disturbance loading component of the fatigue test rig of the present invention;
FIG. 13 is a schematic diagram of a horizontal loading hydraulic system of the fatigue test stand of the present invention.
FIG. 14 is an enlarged view of a disturbance loading structure of a fatigue test stand according to the present invention
FIG. 15 is a schematic view of a crack image detection device of a fatigue test stand according to the present invention
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. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 and 2, the multi-axis loading fatigue test bed for the fan blade of the turbofan engine, which is designed by the invention, mainly comprises a test piece 1, a vertical loading device 2, a horizontal loading device 3, a disturbance loading device 4, a hydraulic system 5, an electric control system 6, an illumination light source 7, a CCD camera 8 and upper computer software 9.
As shown in fig. 3, a test piece 1 is composed of a blade test piece 12 and a turbine disk test piece 11, the blade test piece 12 effectively simulates the root geometry and material characteristics of a fan blade, the blade test piece and the turbine disk test piece form a dovetail joint structure, through holes are processed on the blade test piece 12 and the turbine disk test piece 11, the blade test piece and the turbine disk test piece are conveniently connected with a clamp through a pin shaft, the root of the blade test piece 12 and the turbine disk test piece 11 can form a dovetail tongue-and-groove structure, the shapes of a tenon and a tongue-and-groove part can be enlarged or reduced according to a certain ratio during processing of the test piece, and after the sizes of the tenon and the tongue-and-groove part are specifically determined, the length of the blade test piece or the length or the width of the turbine disk test piece can meet the installation space of a loading test bed.
As shown in fig. 4, 5, 6, and 7, the vertical loading device 2 is composed of a material fatigue testing machine (the material testing machine mainly comprises a column 21, a beam 22, an upper hydraulic chuck 23, a lower hydraulic chuck 24, a loading base 25, and the like), a switching clamp Y-shaped adapter 26, a turbine disk upper clamp 27, and a blade test piece clamp 28.
As shown in fig. 9 and 4, in the hydraulic chuck 27 clamped by the convex edge of the Y-adapter 26, the concave end of the Y-adapter 26 is connected with the convex end of the turbine disk upper clamp 27, so that the additional bending moment caused by uneven loading geometric center can be eliminated in the loading process, the structure of the MTS material testing machine can be effectively protected from being damaged in the loading process, the turbine disk upper clamp 27 can penetrate through the through hole by a pin shaft to be connected with a turbine disk test piece, the turbine disk lower clamp 28 can penetrate through the through hole by a pin shaft to be connected with a blade test piece, and the state of each clamp after being connected with the test piece is shown in fig. 9. The Y-shaped adapter 26 can be connected to the cross beam 22 of the material fatigue testing machine, the blade test piece clamp 28 is connected to the vertical hydraulic loading actuator, the material fatigue testing machine can realize vertical loading by controlling the vertical loading hydraulic actuator, and in test piece loading, because the inner part of the mortise is in a fretting wear state, the elastic deformation of the mortise is very small.
The material fatigue testing machine is a hydraulic drive material testing machine of American MTS810 type, and the load of a main engine is +/-250 kN.
As shown in fig. 8 and 10, the horizontal loading device 3 is of a symmetrical design and is composed of a hydraulic loading actuator 31, a loading chuck 32, a blade specimen horizontal clamp 33, a horizontal loading platform 35 and a bottom plate support sleeve frame 36.
As shown in fig. 11, the number of the bottom plate support sleeve frames 36 is two, each of the bottom plate support sleeve frames is composed of a half sleeve 361 and a half sleeve 362, the aperture of the inner portion of each sleeve is slightly smaller than the diameter of the upright post 21, a fixing plate 3623 is welded at the upper end of each sleeve, threaded holes are machined in the fixing plate 3623, the half sleeve 361 and the half sleeve 362 are respectively connected with the left upright post 21 and the right upright post 21 of the hydraulic fatigue testing machine, fixing blocks 3611 and 3621 are welded at the upper side and the lower side of the left half sleeve and the right half sleeve, threaded holes are machined in the fixing blocks 3611 and 3621 and penetrate through the fixing blocks 3611 and 3621 through bolts, the bottom surface of the bottom plate support sleeve frame 36 is tightly attached to the lower working surface of the material fatigue testing machine, and the bottom plate support sleeve frame 36 is fixed on the upright posts to be locked. The horizontal loading platform 35 may be mounted on a mounting plate 3623 of the floor support sleeve mount 36 so that the horizontal loading platform is fixed at a height from the material testing machine base.
The horizontal loading platform 35 is composed of a bottom plate 351, a fixed flange 352 and a pull rod 353. The bottom plate 351 is connected with the fixing plate 3623 through bolts and is fixed at a space position with a certain height away from the working surface of the material fatigue testing machine; the fixed flanges 3521 and 3522 are fixed on the bottom plate 351 through bolts respectively, the horizontal hydraulic loading actuator 31 is installed on the fixed flange 352 through bolts, two counter bores are machined in the fixed flanges, and the pull rods 353 and 354 connect the fixed flanges 3521 and 3522 respectively to form a geometric closed force system frame.
Horizontal hydraulic loading actuators 31 are installed on the horizontal loading platform and are symmetrically distributed on the two sides of the vertical loading device 2 in the left-right direction, the hydraulic loading actuators 31 are respectively connected with a test piece clamp 33 through a horizontal loading chuck 32, the other end of the test piece clamp 33 is connected with the turbine disc test piece 11, and detection of horizontal output load can be achieved by attaching a strain gauge to the tail end of the clamp 33.
The horizontal loading device is additionally arranged on the existing material testing machine, the horizontal loading hydraulic actuator outputs large load in the horizontal direction, the load output by the horizontal loading hydraulic actuator 32 is except for acting on a test piece, the reaction force is limited in a closed force system, and the left stand column and the right stand column cannot be impacted.
As shown in fig. 12 and 14, the disturbance loading unit 4 is composed of an electric push rod 41, a loading frame 42, and a base 43, wherein the base 43 is installed on a fixing plate 3622 welded on the fixing and locking sleeve 36, and the geometric center of the base and the vertical loading device 2 are on a central line. The loading frame 42 is sleeved on the handle part of the blade test piece 11, a threaded hole is processed on the loading frame, a pin is screwed into the threaded hole to prop against the handle part of the blade test piece, the other end of the loading frame is connected with the electric push rod 41, the electric push rod 41 is fixed on the base 43, and the electric push rod 41 drives the loading frame to slightly move through the reciprocating motion of the push rod, so that the disturbance loading on the blade test piece is realized.
As shown in fig. 15, the crack image detection device is shown in fig. 14 and consists of a CCD camera 7, an illumination light source 8 and upper computer software 9; the detection device realizes measurement of tip displacement and strain field of fatigue crack based on DIC principle. Before the test, the surfaces of the test pieces 11 and 12 need to be subjected to speckle spraying treatment, the speckles at the root parts of the blade test pieces are shot by the CCD camera 7, the lighting source 8 irradiates light rays onto the test pieces, the light rays are reflected by the test pieces and are imaged on the CCD camera, and then the CCD camera 7 collects images and sends the images into a computer for analysis and treatment.
As shown in fig. 13, the hydraulic system 5 is composed of a filter 13-1, a motor 13-2, a variable plunger pump 13-3, a check valve 13-4, a two-position four-way electromagnetic directional valve 13-5, an energy accumulator 13-6, a stop valve 13-7, an energy accumulator control valve group 13-8, a pilot type pressure reducing valve 13-9, an H-type three-position four-way electromagnetic directional valve 13-10, a one-way throttle valve 13-11, a pilot type check valve 13-12, a horizontal loading hydraulic cylinder 13-13, a cooler 13-15, an oil tank 13-16, an electromagnetic overflow valve 13-17, a 1 pressure sensor 3-18 and a pressure gauge 13-19.
The basic working principle of the hydraulic system is as follows:
according to the design of a hydraulic system, firstly, a motor 13-2 is started, the motor drives a one-way variable plunger pump 13-3 to operate, hydraulic oil enters the plunger pump after filtering oil impurities and air in a filter 13-1, the plunger pump provides high-pressure oil with corresponding flow to the system, the high-pressure oil pushes a one-way valve 13-4(A) to enter a main system, the one-way valve 13-4(A) can prevent the normal work of the pump from being influenced by the high-pressure impact of the system during work, and the pressure of the high-pressure oil can be regulated through a pilot overflow valve 13-9 so as to meet the pressure requirement of a loading system; the high-pressure oil firstly enters the energy accumulator to charge, and when the pressure sensor 13-18(A) outputs an energy accumulation signal of the energy accumulator, the two-position four-way electromagnetic valve 13-5 is electrified, and the high-pressure oil can enter the loading loop system.
After the high-pressure oil pushes the one-way valve 13-4(B), the one-way valve 13-4(B) has the function of separating the two loops, so that the pressure oil of the vertical loading loop is prevented from flowing backwards to influence the normal work of other systems. The pressure of the hydraulic oil can be remotely adjusted by the high-pressure oil in the B path through the pilot type reducing valves 13-9, and the reduced high-pressure oil respectively enters the lever working cavities of the horizontal loading hydraulic cylinders which are symmetrical left and right, so that the horizontal loading hydraulic cylinders output pulling force outwards. The hydraulic loading loop is provided with three-position four-way electromagnetic directional valves 13-10 of which the middle part can be H-shaped, and in the early preparation process of tests such as mounting fixtures and other devices, the electric control system 5 can control the left and right positions of the electromagnetic valves to be powered on and off, and the hydraulic loading actuator 31 is controlled to extend and retract, so that the extending distance of the end part of the piston rod can be adjusted, and the connection and mounting among all parts are facilitated.
The hydraulic system can realize pressure maintenance and minimum power operation: the fatigue loading times of the common blade root tenon fatigue test are 104In the above, the time duration of one fatigue test is about 5 hours, the hydraulic loading actuator 31 outputs the hydraulic load in the test, the moving distance of the piston rod is very small each time, and the overflow of the high-pressure oil with excessive flow in the work is reduced; when the pressure sensor 13-18 on the main system sends out a signal that the system pressure reaches the designed upper limit, the electric control system 5 makes the electromagnetic valve 13-17 lose power, the pilot valve of the pilot overflow valve is communicated with the oil tank, the hydraulic pump is unloaded, the motor reduces the lowest power to operate, the main system is separated by the one-way valve 13-4(A), the pressure oil required by the hydraulic cylinder is provided by the energy accumulator, when the pressure of the energy accumulator is reduced to the designed lower limit value of the pressure measured by the sensor 13-18, the PLC sends out an electric signal to make the electromagnetic valve 13-17 electrified, the pilot overflow valve restores to the normal working state, the high-pressure oil output by the plunger pump enters through the one-way valve againThe system and the energy accumulator ensure the pressure of the system to be maintained stably through simple negative feedback control of the PLC, and can reduce the energy consumption of the system in operation.
Furthermore, the hydraulic system can realize stepless adjustment of loading pressure. In the hydraulic system, the main pressure of the whole system can be adjusted through the pilot overflow valve 13-9, and the high-pressure oil directly enters the vertical loading loop after passing through the one-way valve, so that the system pressure of the vertical loading unit reaches a preset value by adjusting the set value of the electromagnetic overflow valve 13-9; the horizontal load pressure is steplessly adjusted by the pilot type reducing valve 13-9, and different working pressures are adjusted by the cooperation between the overflow valve 13-7 and the reducing valve 13-9 so as to meet the load requirement of the test bed.
Further, a hydraulic locking loop is arranged on the hydraulic loading actuator: the hydraulic circuits of the three loading units are all provided with hydraulic locks 13-12, namely two superposed hydraulic control one-way valves, when the electromagnetic reversing valve is in a middle position, an oil inlet circuit of each hydraulic control one-way valve is connected to an oil tank, after pressure is unloaded, the loading circuit is blocked by the one-way valve, when the three-position four-way electromagnetic reversing valve is in a left (right) position, high-pressure oil can push the hydraulic control one-way valve open, and the hydraulic lock circuits are in a normal communication state.
While particular embodiments of the present invention have been described, it will be understood by those skilled in the art that these are by way of illustration only and that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is, therefore, defined in the appended claims.
Claims (9)
1. The utility model provides a turbofan engine fan blade multiaxis loading fatigue test platform which characterized in that includes: the device comprises a test piece, a vertical loading device, a horizontal loading device, a disturbance loading device, a crack image detection device, a hydraulic system, an electric control system and upper computer software;
the test piece consists of a blade test piece and a turbine disc test piece, wherein the blade test piece effectively simulates the geometry and the material characteristics of the root of the fan blade, and the blade test piece and the turbine disc test piece form a dovetail joint structure; the geometric shape and the size of the test piece can be adjusted within a set range, and the material composition and the surface spraying treatment of the test piece can be selected according to the loading test requirement; the turbine disc test piece is designed in a bilateral symmetry mode, so that the loads borne by the turbine disc test piece are equal when the turbine disc test piece is subjected to left-right tensile loading, and through holes are machined in the upper side, the left side and the right side of the turbine disc test piece so as to be conveniently connected with a clamp;
the vertical loading device outputs a load in the vertical direction to realize the tension loading on the root part of the blade test piece and consists of a material fatigue testing machine, an upper hydraulic chuck, a lower hydraulic chuck and a vertical test piece clamp; the vertical direction test piece jig includes: the device comprises a turbine disc test piece upper clamp, a blade test piece clamp and a switching clamp; the upper hydraulic chuck and the lower hydraulic chuck are positioned on the same vertical axis; the upper hydraulic chuck fixes a turbine disc test piece through a turbine disc test piece clamp, the lower hydraulic chuck is connected with a blade test piece through a blade test piece clamp, and normal centrifugal force borne by the blade test piece is effectively simulated through loading in the vertical direction; the upper hydraulic chuck and the lower hydraulic chuck are accessories of the material fatigue testing machine, and the material fatigue testing machine further comprises a cross beam, an upright post, a rack and a vertical loading hydraulic actuator; the vertical loading hydraulic actuators are arranged in the rack, the upright columns are arranged on the left side and the right side of the rack, and the cross beam is sleeved on the upright columns and fixed at a certain height;
the horizontal loading device is used for symmetrically outputting horizontal direction loads to realize tensile loading on a turbine disc test piece and simulate dovetail groove expansion caused by loading of a turbine disc when an engine actually works, and is arranged on a rack of a material fatigue test piece and is lower than a cross beam;
the disturbance loading device outputs disturbance load to the root of the blade and simulates the vibration load borne by the blade due to airflow disturbance under the actual working condition, the disturbance loading device is arranged on the working surface of the material fatigue testing machine, and the load acts on the root of a blade test piece;
the hydraulic system consists of a series of hydraulic components and provides hydraulic oil to power a hydraulic loading actuator of the horizontal loading device; the hydraulic system is connected to the hydraulic actuator through a hydraulic pipeline and is arranged on the horizontal ground;
the electric control system is connected with the hydraulic system and the disturbance loading system through signal lines, provides power output interfaces of required types for each loading system, controls the work of each function of the hydraulic system and the disturbance loading system, and can collect circuit signals on the strain gauge and perform certain signal processing; the electric control system is arranged in the electric control cabinet, and the electric control cabinet is arranged on the horizontal ground;
the crack image detection device is arranged on the CCD camera bracket, is irradiated on the surface of the test piece by an illumination light source, and continuously photographs the test piece by the CCD camera during fatigue loading and transmits the photographs to the upper computer software;
the upper computer software is used for setting each parameter of the test loading and controlling the electric control system to realize the control of each loading device; and simultaneously controlling a CCD camera to photograph the test piece, detecting a crack image, calculating the tip displacement of the fatigue crack, and measuring a strain field to obtain an analysis result.
2. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 1 wherein: the horizontal loading device consists of a hydraulic loading actuator, a loading chuck, a turbine disc test piece horizontal clamp and a horizontal loading platform; horizontal loading platform is connected and is fixed on the take the altitude through the left and right sides stand with material fatigue testing machine, hydraulic pressure loading actuator installs horizontal loading platform on, and bilateral symmetry distributes in perpendicular loading device both sides, two hydraulic pressure loading actuators are respectively through horizontal loading chuck connection turbine dish test piece anchor clamps, the turbine dish test piece is gone up the anchor clamps other end and is connected through round pin axle turbine dish test piece, through pasting the foil gage on the test piece, realizes the detection to horizontal output load.
3. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 2 wherein: the horizontal loading platform comprises: the bottom plate, the fixed flange, the pull rod and the bottom plate support sleeve frame; the bottom plate supporting sleeve frame is respectively sleeved with the left and right stand columns, the bottom surface of the sleeve is tightly attached to the working surface of the material fatigue testing machine, a fixed plate is welded on the sleeve, a threaded hole is machined in the fixed plate, the bottom plate is connected with the fixed plate, and the bottom plate is fixed at a spatial position which is a certain height away from the working surface of the material fatigue testing machine; the two fixing flanges are fixed on the bottom plate left and right respectively, the hydraulic loading actuator is installed on the flanges, two counter bores are machined in the fixing flanges, and the left fixing flange and the right fixing flange are connected through the pull rod respectively.
4. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 1 wherein: the disturbance loading device consists of a disturbance loading platform, an electric push rod and a disturbance loading frame; the disturbance loading platform is installed on the working face of the material fatigue testing machine, the geometric center of the disturbance loading platform and the vertical loading device are on the same central line, the electric push rods are symmetrically installed on two sides of the disturbance loading platform, the disturbance loading frame penetrates through the root of the blade, the tail end of the electric push rod is connected with the disturbance loading frame, threaded holes are machined in the disturbance loading frame, the disturbance loading frame is fixed at a certain position of the root of the blade through screw-in screws, the electric push rods drive the loading frame to slightly move through the reciprocating motion of the lead screws, and disturbance loading of a blade test piece is achieved.
5. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 3 wherein: the structure of the horizontal loading platform realizes a closed force system frame, a left fixing flange and a right fixing flange which are symmetrical are arranged on a bottom plate, the fixing flanges are connected by two pull rods, and when a horizontal loading device outputs symmetrical horizontal loading loads, the horizontal loads are limited in the closed structure and act on a turbine disc test piece.
6. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 3 wherein: the bottom plate support sleeve comprises left and right support sleeves, and is installed respectively on two stands of material fatigue testing machine, and it has the fixed plate to weld at telescopic top, and processing has the mounting hole on the fixed plate, provides fixed position for horizontal loading device, or provides mounting platform for other experimental facilities.
7. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 1 wherein: the single-shaft vertical direction fatigue testing machine is utilized, the limitation on the space size is broken through, the multi-shaft loading of the test piece is realized by adding the horizontal loading device and the disturbance loading device thereof, and the normal work of the whole system is ensured.
8. The turbofan engine fan blade multi-axial loading fatigue test rig of claim 1 wherein: the crack image detection device consists of a CCD camera and an illumination light source; measuring the tip displacement and strain field of the fatigue crack based on DIC principle; before the test, the surface of a test piece is required to be subjected to speckle spraying treatment, the speckles at the root of a blade test piece are shot by a CCD camera, a lighting source irradiates light onto the test piece, the light is reflected by the test piece and is imaged on a CCD camera, and then the CCD camera collects images and sends the images into upper computer software for analysis and treatment.
9. A multi-axis loading fatigue test method for a fan blade of a turbofan engine is characterized by comprising the following operation steps:
step 1: and (3) treating the surface material of the test piece: according to different test requirements, selecting a tenon joint face formed by the root parts of the turbine disk test piece and the blade test piece to carry out surface material treatment;
step 2: and (3) spraying speckles on the test piece: the CCD camera is used for photographing the loaded test piece, the strain and stress in the loading process can be conveniently calculated, the surface of the turbine disc and the blade test piece is required to be subjected to speckle spraying treatment, and speckles can be distributed uniformly and clearly and are easy to identify by the CCD camera;
and step 3: installing a test piece: firstly, a turbine disc test piece is installed in an upper clamp, the upper clamp is fixed to a hydraulic upper chuck, the height of a cross beam of a material fatigue testing machine is adjusted to enable the turbine disc test piece to be in a state to be clamped, a lower clamp is connected to a blade test piece, the root of the blade test piece is installed in a dovetail groove in the turbine disc test piece, after the lower clamp is fixed through the hydraulic lower chuck, a vertical loading hydraulic actuator is started in advance to enable the blade test piece to be subjected to pretightening force, and then the height of the cross beam and the stroke size of the vertical loading hydraulic actuator are respectively adjusted to enable the test piece which is integrally clamped to be in a height convenient for horizontal loading; respectively installing a left clamp and a right clamp on two sides of the turbine disc test piece, and respectively connecting the left clamp and the right clamp to the tail end chuck parts of the left hydraulic actuator and the right hydraulic actuator; then, performing a preloading test to adjust the matching relationship between the test pieces so as to enable the root of the blade test piece and the dovetail groove part of the turbine disk to be in a micro-motion state;
and 4, step 4: installing a crack image detection device, installing an illumination light source beside the test bed, wherein the illumination light source and the normal line of the surface of the blade test piece close to the root part are irradiated at an angle of 0-90 degrees, the illumination light source is firstly completely and clearly irradiated on the surface of the test piece, the reflection phenomenon does not occur on the surface of the blade test piece close to the root part, and the dovetail joint can be clearly seen; erecting a camera support on a horizontal ground close to the hydraulic fatigue testing machine, fixing the CCD camera on the camera support, and adjusting the focal length of the CCD camera;
and 5: setting test parameters, and respectively setting vertical loading parameters, horizontal loading parameters and test termination conditions on upper computer software, wherein the loading parameters comprise loading forms in horizontal and vertical directions and the magnitude of loading force, and the loading forms comprise static loading and unidirectional pulsating loading; when horizontal and vertical direction loading is carried out, the sequence of horizontal and vertical loading is also set on the upper computer software; after setting parameters, preparing a preloading test;
step 6: test load acquisition and feedback control: installing resistance strain gauges on the surfaces of a turbine disc test piece and a blade test piece, acquiring strain electric signals in the test piece loading process by the resistance strain gauges, transmitting the strain electric signals into an electric control cabinet for processing to obtain the load output in the vertical direction and the horizontal direction, uploading the load signals output in the vertical direction and the horizontal direction to an upper computer by an electric control system for storage and processing, comparing according to preset loading parameters, sending feedback output signals to the electric control system, and controlling each hydraulic loading actuator to work by the electric control system;
and 7: during preloading, determining whether the deformation or damage of the tenon connection structure occurs in the loading process of the test piece, and if so, immediately stopping the test; after the test piece is preloaded normally, setting working parameters of the CCD camera in the software of the upper computer, wherein the working parameters comprise: the frequency of photographing, whether to preprocess the image; focusing of the CCD camera is adjusted again, so that the image of the tenon joint part of the root of the blade is displayed on a software interface of the upper computer clearly in real time;
and 8: and (4) terminating the test: and monitoring the signals of the strain gauge sensors in all directions on the surface of the test piece by the upper computer software, analyzing whether the acquired image has deformed cracks or not in real time through a DIC (digital image computer) detection algorithm, judging that the test piece reaches the termination condition set by the test, and finishing the test.
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