A method for measuring contact interface mechanical property curve

Abstract

The present application relates to a kind of contact interface mechanical property curve measurement methods, belong to contact force measurement technical field, solve the problem that the contact force level in prior art is greatly influenced to the contact force measurement error of aero-engine turbine blade.The present application includes the following steps: S1: install blade to test table;S2: install force measuring device to test table;S3: connect force sensor to data acquisition card, data processing;S4: adjust the relative position of force measuring device and blade and fix;S5: set acceleration sensor;S6: excitation is applied to blade, and data is recorded;S7: calculate and analyze to obtain mechanical property curve.The present application avoids the influence of contact force level on contact force measurement error by the arrangement mode of specific friction block and force transmission structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of contact force measurement, and particularly relates to a contact interface mechanical property curve measurement method. BACKGROUND

[0002] The turbine blade of an aero-engine often adopts a dry friction damping structure for vibration reduction. The dry friction damping structure relies on the friction of a contact interface for energy dissipation and vibration reduction. The mechanical properties of the contact interface determine the vibration reduction effect of the dry friction damping structure. The mechanical properties of the contact interface include parameters such as contact stiffness, friction coefficient and wear rate, which can be obtained by measuring the mechanical property curve of the contact interface, that is, the "force-displacement" curve of the contact interface.

[0003] The mechanical property curve of the contact interface can usually be measured through a basic element level test, that is, a friction test is performed on a pair of friction pairs to obtain the relative displacement and contact force between the contact surfaces of the friction pairs. The mechanical property curve of the contact interface obtained by this method is usually measured under a given sinusoidal displacement and constant normal pressure. However, the relative displacement between the contact surfaces of the dry friction damping structure under working conditions is often in a complex relative displacement relationship and under a changing normal pressure condition, and the mechanical properties of the contact interface change after a long time of work, thereby changing the vibration reduction effect of the dry friction damping structure.

[0004] The turbine blade of an aero-engine often adopts a dry friction damping structure for vibration reduction. The friction surface of the crown changes with the working cycle, thereby affecting the vibration reduction effect of the crown and the working stability of the blade. Monitoring the changes of the mechanical properties of the contact interface with the working cycle helps to understand the stress condition, vibration reduction effect and possible failure mode of the blade under working conditions, thereby optimizing the design of the crown structure.

[0005] However, the dry friction damping structure of the turbine blade of an aero-engine often has a small structure size, and due to the structural limitations of the turbine blade, there is still a lack of effective contact interface mechanical property curve measurement devices and measurement methods. The core of measuring the mechanical property parameters of the contact interface is to obtain the mechanical property curve of the contact interface, and further, the core is to measure the relative displacement and contact force between the contact interfaces.

[0006] Considering the structural limitations of the turbine blade with a crown of an aero-engine, the measurement of the contact surface is limited by the structure of the turbine blade, and commercial force measuring elements often cannot be directly applied. The existing mechanical decoupling force measurement scheme is often used for large-size structures such as aircraft landing gears, and does not pay attention to the structural stiffness, resulting in low structural stiffness and easy resonance, thereby causing distortion of the measurement results of the force measurement structure, large deformation of the static part of the contact surface friction pair and other problems, thereby causing distortion of the contact force and relative displacement between the contact surfaces.

[0007] For the contact force measurement of small size contact surface, the force measurement structure needs to have small size to ensure accessibility for measuring the contact surface of the dry friction damping structure such as the blade crown or the shoulder. The force measurement structure also needs to have high system stiffness. High stiffness can increase the natural frequency to avoid the measurement error caused by resonance, and ensure that the structural response is much smaller than the measured object, reducing the measurement error of the relative displacement between the contact surfaces.

[0008] In the relative displacement measurement method, laser displacement sensors are often used due to high measurement accuracy, but they are limited by the structure of the turbine blade and cannot be arranged to measure the displacement of the blade crown contact surface, which has low feasibility.

[0009] Therefore, for the measurement of the mechanical property curve of the contact surface of the turbine blade with crown of the aero-engine, the force measurement structure needs to have small size to ensure accessibility. The force measurement structure also needs to have high system stiffness. High stiffness can increase the natural frequency to avoid the measurement error caused by resonance, and ensure that the structural response is much smaller than the measured object, reducing the measurement error of the relative displacement between the contact surfaces. In the relative displacement measurement of the contact surface, both the relative displacement measurement accuracy and the feasibility of the measurement scheme need to be ensured. SUMMARY

[0010] In view of the above analysis, the present application provides a contact interface mechanical property curve measurement method to solve the problems of force coupling between multiple dimensions and large influence of contact force level on contact force measurement error in the existing multi-dimensional contact force measurement scheme, and to realize contact force measurement of the blade crown contact surface of the turbine blade with crown.

[0011] The present application relates to a contact interface mechanical property curve measurement method, comprising the following steps:

[0012] S1: mounting and fixing the blade root of the turbine blade of the aero-engine on the clamp of the test bench;

[0013] S2: installing the force measurement device on the corresponding position of the test bench;

[0014] S3: connecting the force sensor in the force measurement device to the data acquisition card, and connecting the data acquisition card to the computer for data processing;

[0015] S4: adjusting the relative position of the force measurement device and the turbine blade of the aero-engine and fixing: making the friction block contact surface of the friction block of the force measurement device abut the contact surface of the blade crown of the turbine blade of the aero-engine, and then fixing the force measurement assembly of the force measurement device on the mounting base;

[0016] S5: pasting an acceleration sensor at the position of the blade crown contact surface of the turbine blade of the aero-engine, and connecting the acceleration sensor to the data acquisition card;

[0017] S6: applying excitation to the turbine blade of the aero-engine; recording the measurement data of the force sensor and the acceleration sensor through a data acquisition card;

[0018] S7: performing calculation analysis on the data, thereby obtaining the mechanical property curve of the contact interface of the turbine blade of the aero-engine.

[0019] Further, the mechanical property curve is a "force-displacement" curve.

[0020] Further, step S2 specifically comprises the following steps:

[0021] S21: mounting the force measurement assembly to a mounting base;

[0022] S22: fixing the mounting base to a corresponding position on a test bench.

[0023] Further, in step S21, one group or two groups of the force measurement assembly are selected to be mounted to the mounting base.

[0024] Further, the three force transmission structure bases of the force measurement assembly are first mounted to the mounting base, then the assembled three force transmission structures are fixed to the mounting inclined surfaces of the three force transmission structure bases, respectively, the extension directions of the three force transmission structures are x1, y1 and z1 directions of a first rectangular coordinate system, respectively, the positions of the three force transmission structure bases are adjusted, and finally the friction block base with the fixed friction block is mounted to the top ends of the three force transmission structures.

[0025] Further, the position of the mounting base is adjusted so that the spacing between the friction block contact surface of the friction block and the shroud contact surface is not greater than 3 mm.

[0026] Further, step S3 specifically comprises the following steps:

[0027] S31: connecting the force sensor to a data acquisition card;

[0028] S32: connecting the data acquisition card to a computer and data acquisition software, and starting signal sampling;

[0029] S33: performing transformation processing on the signal of the force sensor in the computer and the data acquisition software, thereby obtaining the contact force measurement result in a third rectangular coordinate system; the third rectangular coordinate system takes the plane on which the friction block contact surface is located as an x3-y3 plane, and takes the direction perpendicular to the friction block contact surface as a z3 direction.

[0030] S34: performing zero drift removal processing on the force sensor signal to remove the zero point drift of the signal.

[0031] Further, in step S4, the position of the mounting base and the force measuring assembly is adjusted so that the contact force measured in the z3 direction of the third rectangular coordinate system is between 0.1 N and 0.2 N, and then the force measuring assembly is fixed on the mounting base.

[0032] Further, in step S5, two one-way acceleration sensors or one multi-way acceleration sensor is pasted on the blade crown contact surface of the aero-engine turbine blade A, the two one-way acceleration sensors are pasted along the y3 direction and the z3 direction respectively, and the multi-way acceleration sensor is selected as a two-way acceleration sensor along the y3 direction and the z3 direction respectively.

[0033] Further, in step S6, the excitation applied to the aero-engine turbine blade A is a simple harmonic excitation, and the direction is perpendicular to the blade surface.

[0034] Further, the contact force signal and the acceleration sensor signal in the third rectangular coordinate system are observed, and after the signals are stable, the contact force signal and the acceleration sensor signal in the third rectangular coordinate system are recorded.

[0035] Further, step S7 comprises the following steps:

[0036] S71: filtering the recorded contact force signal and acceleration sensor signal in the third rectangular coordinate system to remove low-frequency components and unnecessary high-frequency noise in the data;

[0037] S72: twice integrating the acceleration signals of the blade crown contact surface of the aero-engine turbine blade A measured by the acceleration sensor in the y3 and z3 directions to obtain the displacement of the blade crown contact surface;

[0038] S73: drawing a "force-displacement" curve according to the measured contact force signal and the processed blade crown contact surface displacement signal.

[0039] Further, the interface parameters such as dissipation factor, damping ratio, contact stiffness and friction coefficient are obtained according to the "force-displacement" curve, wherein the calculation methods of the dissipation factor and the damping ratio are the commonly used formulas or cognition in the industry, and the contact stiffness and the friction coefficient can be obtained by parameter identification method.

[0040] The present application has at least one of the following beneficial effects:

[0041] (1) The present application provides a simple and convenient method for measuring the mechanical property curve of the contact interface based on the force measuring device, which can be applied to the mechanical property curve measurement of the blade crown contact surface of different types and sizes of aero-engine turbine blades.

[0042] (2) The present invention uses an acceleration sensor and a force measuring device to measure the relative displacement and contact force between the contact surfaces, thereby obtaining the mechanical characteristic curve of the contact surface, namely the "force-displacement" curve.

[0043] (3) Based on the force measurement device, the present invention provides a method for measuring the mechanical properties curve of the contact interface, which can realize the monitoring and measurement of the mechanical properties of the crown contact surface of the aero-engine turbine blade, and process the measurement signal to improve the signal-to-noise ratio, thereby realizing real-time monitoring of the working state of the crown contact surface of the aero-engine turbine blade.

[0044] (4) The mechanical property curves of the contact interface measured by the present invention can be used to obtain interface parameters such as dissipation factor, damping ratio, contact stiffness and friction coefficient of the contact interface, thereby evaluating the mechanical properties and vibration reduction effect of the contact interface. Attached Figure Description

[0045] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0046] Figure 1 A three-dimensional structural diagram illustrating the application scenario of the force measuring device of the present invention for measuring the contact force on the friction surface of a crowned blade;

[0047] Figure 2 A side view showing an application scenario of the force measuring device of the present invention for measuring the contact force on the friction surface of a crowned blade;

[0048] Figure 3 For along Figure 2 The cross-sectional view along the BB line is a cross-sectional view of the location of the friction contact surface in the application scenario of this invention;

[0049] Figure 4 This is a front view of the force measuring assembly;

[0050] Figure 5 This is a cross-sectional view along the axis of the force transmission structure.

[0051] Figure 6 This is a structural diagram of the friction block base;

[0052] Figure 7 This is a schematic diagram of the first coordinate system based on the front view of the friction block base;

[0053] Figure 8 This is a schematic diagram of the first coordinate system based on the top view of the friction block base;

[0054] Figure 9 This is a schematic diagram of the second coordinate system based on the front view of the friction block base;

[0055] Figure 10Fig. 2 is a schematic diagram of a second coordinate system based on the top view of the friction block base;

[0056] Figure 11 Fig. 3 is a structural diagram of the friction block;

[0057] Figure 12 Fig. 4 is a schematic diagram of a third coordinate system based on the top view of the friction block base;

[0058] Figure 13 Fig. 5 is a flowchart of the contact interface mechanical property curve measurement method of the present application.

[0059] In the figure: 1 - mounting base; 11 - mounting plane; 111 - first flat key groove; 112 - second flat key groove; 113 - first threaded hole; 114 - second threaded hole; 115 - slide rail mounting groove; 121 - bolt hole; 122 - mounting groove; 2 - first force transmission structure base; 3 - second force transmission structure base; 4 - third force transmission structure base; 5 - force transmission structure; 51 - force sensor adapter block; 511 - force sensor mounting surface; 512 - base mounting surface; 513 - first through hole; 514 - third counterbore; 52 - force sensor; 53 - force transmission shaft; 531 - first part; 532 - second part; 5321 - rib; 533 - third part; 54 - connecting shaft; 6 - friction block base; 61 - platform part; 611 - friction block mounting groove; 612 - fourth threaded hole; 613 - center through hole; 62 - support rod part; 621 - fifth threaded hole; 7 - friction block; 71 - friction block friction end; 711 - friction block contact surface; 72 - friction block pressing platform; 73 - friction block mounting end; A - aero-engine turbine blade. DETAILED DESCRIPTION

[0060] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, which form a part of this application. The accompanying drawings and the following detailed description provide principles and embodiments of the present application, which can be used to explain the principles of the present application and should not be used to limit the scope of the present application.

[0061] Example 1

[0062] The present application relates to a contact interface mechanical property curve measurement method, which uses a force measurement device.

[0063] As Figure 13 shown, the test method of the present application includes the following steps:

[0064] S1: mounting and fixing the blade root of the aero-engine turbine blade A on the clamp of the test bench;

[0065] S2: installing the force measurement device on the corresponding position of the test bench;

[0066] S3: connecting the force sensor in the force measuring device to the data acquisition card and connecting the data acquisition card to the computer to process the data;

[0067] S4: adjusting the relative position of the force measuring device and the turbine blade A of the aero-engine and fixing: making the friction block contact surface 711 of the friction block 7 abut the contact surface of the shroud of the turbine blade A of the aero-engine, and then fixing the force measuring assembly on the mounting base 1;

[0068] S5: pasting the acceleration sensor at the position of the shroud contact surface of the turbine blade A of the aero-engine and connecting the acceleration sensor to the data acquisition card;

[0069] S6: applying excitation to the turbine blade A of the aero-engine; recording the measurement data of the force sensor 52 and the acceleration sensor through the data acquisition card;

[0070] S7: calculating and analyzing the measurement data to obtain the mechanical property curve of the contact interface of the turbine blade A of the aero-engine.

[0071] In step S1, the test bench for mounting and fixing the turbine blade A of the aero-engine and the mounting and fixing method of the blade A both adopt the conventional test equipment in the prior art, which includes but is not limited to an optical platform, an iron test bench containing a T-shaped groove, etc., and the mounting and fixing method includes but is not limited to bolt fixing, screw fixing, hydraulic fixing, etc., which are well known to those skilled in the art and will not be described herein. Through this step, the blade A is stably fixed on the test bench.

[0072] Step S2 specifically includes the following steps:

[0073] S21: mounting the force measuring assembly on the mounting base 1;

[0074] S22: fixing the mounting base 1 to the corresponding position on the test bench.

[0075] In step S21, referring to Figures 1-4 , first, the positioning table of the first force transmission structure base 2 of the force measuring assembly is clamped into the first flat key groove of the mounting base 1, then the slide rail is fixed into the slide rail mounting groove, and the two slide blocks are respectively fixed and mounted on the slide block mounting surface of the second force transmission structure base 3 and the third force transmission structure base 4, and the slide blocks of the second force transmission structure base 3 and the third force transmission structure base 4 are respectively clamped into the slide rails in the two slide rail mounting grooves.

[0076] Next, the assembled three force transmission structures 5 are respectively fixed to the mounting inclined surfaces of the three force transmission structure bases, referring to Figure 4 , the positions of the three force transmission structure bases are adjusted, and finally the friction block base 6 with the fixed friction block 7 is mounted to the top end of the three force transmission structures 5.

[0077] The three force transmission structures 5 of the force measuring assembly are arranged according to a first coordinate system x1-y1-z1, as shown in Figure 7 、 Figure 8 The force sensor 52 in the force transmission structure 5 measures the force along the extension direction of the three force transmission structures 5, i.e. the force along the three coordinate axis directions of the first coordinate system x1-y1-z1.

[0078] A second coordinate system x2-y2-z2 is constructed with the plane of the platform part of the friction block base 6 as the y2-z2 plane and the direction perpendicular to the platform part as the x2 direction, and the arrangement of the second coordinate system x2-y2-z2 is shown in Figure 9 and Figure 10 .

[0079] Further, the friction block contact surface 711 forms an angle a with the x2-y2 plane of the second coordinate system, the plane of the friction block contact surface 711 is the x3-y3 plane, and the direction perpendicular to the friction block contact surface 711 is the z3 direction, and a third coordinate system x3-y3-z3 is constructed, as shown in Figure 12 .

[0080] The linear transformation relationship between the first coordinate system, the second coordinate system and the third coordinate system is related to the definition method of the coordinate system direction, and the difference of the definition method includes the difference of the definition direction and the naming, and the difference of the positive direction, and the linear transformation relationship obtained will change accordingly, and the change includes the transformation between the rows and columns and the transformation between the positive and negative signs. Referring to Figures 7-10 and Figure 12 , under the coordinate system definition method provided in the embodiment, the linear transformation relationship between the three coordinate systems satisfies the following formula:

[0081]

[0082]

[0083]

[0084]

[0085] In step S21, one or two sets of force measuring assemblies can be selected and installed on the mounting base 1. The installation method of the two sets of force measuring assemblies is shown in Figure 3 , one set of the two sets uses the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4, and the other set uses the first force transmission structure base 2', the second force transmission structure base 3' and the third force transmission structure base 4'.

[0086] In step S22, the position of the mounting base 1 is adjusted so that the distance between the friction block contact surface 711 of the friction block 7 and the shroud contact surface is not greater than 3 mm. Preferably, the friction block contact surface 711 of the friction block 7 is in contact with the shroud contact surface. After adjustment, the mounting base 1 is fixed on the test bench. The mounting base 1 is fixedly mounted on the test bench through the bolt holes and the mounting groove. The specific connection mode can be determined according to the structure of the test bench, and does not affect the application effect.

[0087] Through this step, the force measuring device can be initially installed.

[0088] Step S3 specifically includes the following steps:

[0089] S31: connecting the force sensor 52 to the data acquisition card;

[0090] S32: connecting the data acquisition card to the computer and the data acquisition software, and starting signal sampling;

[0091] S33: transforming and processing the signal of the force sensor 52 in the computer and the data acquisition software to obtain the contact force measurement result in the third rectangular coordinate system; wherein the third rectangular coordinate system takes the plane where the friction block contact surface is located as the x3-y3 plane, and takes the direction perpendicular to the friction block contact surface as the z3 direction;

[0092] S34: removing the zero drift of the signal of the force sensor 52 to remove the zero point drift of the signal.

[0093] Through this step, the influence of the zero frequency component error in the force signal can be effectively removed, so as to avoid the measurement error of the static component of the contact force.

[0094] In step S4, specifically, the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4 are moved so that the friction block contact surface 711 of the friction block 7 is in contact with the contact surface of the turbine blade A of the aero-engine, and the data fed back by the force sensor 52 is between 0.1 N and 0.2 N. When this condition is met, it indicates that the friction block 7 is in good contact with the contact surface of the shroud, neither too loose to obtain effective data nor too tight to obtain inaccurate data. Then the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4 are fixed on the mounting plane.

[0095] The platform part 61 of the friction block base 6 is perpendicular to the blade height direction of the turbine blade A of the aero-engine.

[0096] Then the first force transmission structure base 2 is fixed on the installation plane through the countersunk head nail and the first countersunk hole; the second force transmission structure base 3 is fixed at one slot in the first group of second flat key grooves through the flat key and the countersunk screw, and the third force transmission structure base 4 is fixed at one slot in the second group of second flat key grooves.

[0097] In step S5, two acceleration sensors are pasted at the shroud contact surface position of the aero-engine turbine blade A, and the acceleration sensors are connected to the data acquisition card. The pasting directions of the two acceleration sensors are along the y3 direction and the z3 direction, respectively.

[0098] It should be noted that two-way acceleration sensors or three-way acceleration sensors can also be selected to reduce the number of acceleration sensors. The acceleration sensors have high measurement accuracy and good measurement effect for high-frequency vibration signals of the aero-engine turbine blade.

[0099] In some other embodiments, the acceleration sensors can be replaced by displacement sensors.

[0100] In step S6, an excitation is applied to the aero-engine turbine blade A. The excitation direction and signal form can be determined according to the test requirements. Preferably, the excitation can be selected as a simple harmonic excitation, and the direction is perpendicular to the surface of the blade A. The contact force signal and the acceleration sensor signal in the third rectangular coordinate system are observed, and after the signals are stable, the contact force signal and the acceleration sensor signal in the third rectangular coordinate system are recorded.

[0101] Step S7 includes the following steps:

[0102] S71: The recorded contact force signal and the acceleration sensor signal in the third rectangular coordinate system are filtered to remove low-frequency components and unnecessary high-frequency noise in the data;

[0103] S72: The acceleration signals of the shroud contact surface of the aero-engine turbine blade A in the y3 and z3 directions measured by the acceleration sensor are integrated twice to obtain the displacement of the shroud contact surface;

[0104] S73: A "force-displacement" curve is drawn according to the measured contact force signal and the processed shroud contact surface displacement signal.

[0105] In step S7, the force sensor 52 of the three force transmission structures 5 measures the force data f1t as:

[0106]

[0107] It is obvious that the three components in the force data are along the three coordinate axes of the first coordinate system, respectively.

[0108] In step S5, the method of calculating the data specifically includes: performing linear coordinate transformation on the force data f1t measured by the three force sensors 52 to the third rectangular coordinate system, so as to obtain the friction contact force fc on the friction block contact surface 711:

[0109]

[0110] f c =A2A1f 1t ;

[0111]

[0112]

[0113] When a load f2 is applied according to the second coordinate system x2-y2-z2, the load in the first coordinate system x1-y1-z1 can be equivalent to f 1,2 :

[0114]

[0115]

[0116] That is:

[0117]

[0118] The load f 1t,2 in the first coordinate system measured by the three force transmission structures 5 arranged according to the first coordinate system is:

[0119]

[0120] The load f 1t,2 is transformed back to the second coordinate system to obtain the actual measurement result f 2t,2 ,

[0121]

[0122] The relative error between the actual measurement result f 2t,2 and the load f2 can be expressed as:

[0123]

[0124]

[0125]

[0126] At this time, the relative error is only related to the decoupling degree γ and is independent of the contact force level, that is, the relative error of the contact force measurement result can be decoupled from the contact force level by applying the load according to the second coordinate system and measuring the load level according to the first coordinate system, so that the accuracy of the force measuring assembly is only related to the decoupling degree of the force transmission shaft 53.

[0127] The relationship between the third coordinate system established on the friction block contact surface 711 and the second coordinate system can be expressed as that the third coordinate system is obtained by rotating the second coordinate system by α degrees around the x2 axis, and since in the second coordinate system, e y2 and e z2 are equal, therefore, the contact force measurement accuracy when the load is applied in the third coordinate system is the same as that in the second coordinate system.

[0128] Through this setting, for the blade crown contact surfaces with different angles, the measurement can be realized by changing the angle of the friction block contact surface and the corresponding third coordinate system, while the measurement accuracy is not affected, so that the force measuring device for the crown turbine blade of the application can better adapt to the contour shape of the crown turbine blade.

[0129] The force measuring device used in the method of the application reduces the proportion of the load transmitted in the force measuring direction by reducing the ratio of the transverse bending stiffness to the axial tensile and compressive stiffness, and then changes the decoupling degree by changing the structural parameters to control the measurement accuracy.

[0130] On this basis, in order to reduce the influence of the contact force level in different directions on the relative error, the application arranges the force transmission structure in the first rectangular coordinate system, and there is a linear transformation relationship between the rectangular coordinate system and the second coordinate system with the plane of the platform part 61 of the friction block base 6 as the y2-z2 plane and the direction perpendicular to the platform part 61 as the x2 direction, and considering that there is an angle α between the friction block contact surface 711 and the x2-y2 plane of the second coordinate system, a third coordinate system is established based on the friction block contact surface 711 and the x2 direction of the second coordinate system, and there is a linear transformation relationship between the third coordinate system and the first coordinate system and the second coordinate system. Using the third coordinate system as the contact surface coordinate system and using the first coordinate system to arrange the force transmission structure and measure the contact force, so that the coupling influence between the forces in different directions is only related to the decoupling degree of the force transmission shaft 53 and is independent of the contact force.

[0131] In the technical scheme of the application, the friction pair moving part is in contact with the friction block 7 to transmit the contact force, the forces in the three coordinate axes directions in the first coordinate system measured by the three orthogonal direction force sensors 52, and the transformation relationship between the coordinate systems can be used to obtain the measurement results of the contact forces in the second coordinate system and the third coordinate system, and finally obtain the measurement result of the contact force on the contact surface of the friction block 7 in the third coordinate system.

[0132] Further, the interface parameters such as dissipation factor, damping ratio, contact stiffness and friction coefficient of the contact interface can be obtained according to the "force-displacement" curve, wherein the calculation methods of the dissipation factor and the damping ratio are common formulas or cognition in the industry, and will not be described herein again, and the contact stiffness and the friction coefficient can be obtained by a parameter identification method, which does not belong to the scope of the patent.

[0133] The application provides a simple and convenient method for measuring the mechanical property curve of the contact interface based on the force measuring device, which can be applied to the mechanical property curve measurement of the shroud contact surface of the turbine blade of the aero-engine of different types and different sizes.

[0134] Example 2

[0135] The application also relates to a force measuring device for implementing the method in Example 1.

[0136] The force measuring device is shown in Figures 1-3 , and includes a mounting base 1 and at least one force measuring assembly, wherein the structure of the force measuring assembly is shown in Figure 4 . The force measuring assembly is fixedly arranged on the mounting base 1, and the position of the force measuring assembly on the mounting base 1 is adjustable.

[0137] The mounting base 1 has a mounting plane extending in the vertical direction. The mounting plane of the mounting base 1 is used for mounting the force measuring assembly.

[0138] Referring to Figures 1-4 , the force measuring assembly includes a first force transmission structure base 2, a second force transmission structure base 3, a third force transmission structure base 4, three force transmission structures 5, a friction block base 6 and a friction block 7. One end of each of the three force transmission structures 5 is fixedly connected to the first force transmission structure base 2, the second force transmission structure base 3 or the third force transmission structure base 4, and the other end of each of the three force transmission structures 5 is fixedly connected to the friction block base 6. The friction block 7 is fixedly arranged on the platform part of the friction block base 6, and the platform part of the friction block base 6 and the mounting plane of the mounting base 1 are parallel to each other and are spaced apart by a distance.

[0139] Referring to Figures 1-2 , during installation, the first force transmission structure base 2 is installed at the first flat key groove, the second force transmission structure base 3 is installed at the first group of second flat key grooves, the third force transmission structure base 4 is installed at the second group of second flat key grooves, and fastening connection is realized through screws and first threaded holes. The second force transmission structure base 3 and the third force transmission structure base 4 are connected together through screws between the sliding blocks, and the sliding blocks are installed on the sliding rails.

[0140] Referring to Figures 4-6The one end of the force transmission structure 5 is fixedly connected with the support rod part 62 of the friction block base 6 through a threaded fastener, and the other end is fixedly connected with the installation inclined surface of the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4 through a third threaded hole.

[0141] Referring to Figure 5 Each force transmission structure 5 comprises a force sensor adapter block 51, a force sensor 52, a force transmission shaft 53 and a connecting shaft 54.

[0142] The force sensor adapter block 51 comprises a force sensor mounting surface, a base mounting surface, a first through hole and a third countersunk hole.

[0143] The force sensor mounting surface of the force sensor adapter block 51 cooperates with the force sensor 52, and the base mounting surface cooperates with the installation inclined surface of the three force transmission structure bases. Four first through holes are formed around the force sensor adapter block 51, and the positions of the first through holes match the threaded holes on the three force transmission structure bases. A third countersunk hole is formed in the center of the force sensor adapter block 51, and the size of the third countersunk hole matches the size of the screw required by the force sensor 52. During installation, the screw passes through the third countersunk hole to fix the force sensor 52 and the force sensor adapter block 51 together, and the screw passes through the first through hole to fix the force sensor adapter block 51 on the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4.

[0144] The base mounting surface of the force sensor adapter block 51 is fixedly connected with the installation inclined surface of the three force transmission structure bases, the force sensor mounting surface is fixedly connected with one end of the force sensor 52, the other end of the force sensor 52 is fixedly connected with one end of the force transmission shaft 53, the other end of the force transmission shaft 53 is fixedly connected with one end of the connecting shaft 54, and the other end of the connecting shaft 54 is fixedly connected with the friction block base 6.

[0145] The connecting shaft 54 comprises a friction block base connecting end, a force transmission shaft connecting end and a limiting ring. The friction block base connecting end has a semicircular part protruding outward in the axial direction, a protruding block part protruding outward in the radial direction from the center of the semicircular part, and a second through hole 5413 penetrating the semicircular part and the protruding block part, the second through hole 5413 being used for connecting with the friction block base 6 and matching the fifth threaded hole 621 in size and position.

[0146] Preferably, referring to Figure 6 The end of the support rod part 62 of the friction block base 6 is milled to form a slot, which is suitable for positioning and installation with the protruding block part. The force transmission shaft connecting end is provided with external threads. The limiting ring is located between the friction block base connecting end and the force transmission shaft connecting end, and has an outer diameter greater than that of the friction block base connecting end and the force transmission shaft connecting end.

[0147] Referring to Figure 5The force transmission shaft 53 is a hollow shaft structure, and is divided into a first part 531, a second part 532 and a third part 533 in the axial direction. The first end of the first part 531 is fixedly connected to the connecting shaft 54 through threads, the first end of the second part 532 is fixedly connected to the second end of the first part 531, and the second end of the second part 532 is fixedly connected to the first end of the third part 533. The second end of the third part 533 of the force transmission shaft 53 is fixedly connected to the force sensor 52.

[0148] Further, the first part 531 is provided with a threaded hole in the center, which has the same size as the external thread of the connecting end of the force transmission shaft and a smaller diameter than the inner diameter of the second part. The outer diameters of the first part 531, the second part 532 and the first end of the third part 533 are the same. The outer diameter of the second end of the third part 533 is smaller than the first end, and is provided with external threads, which have the same size as the force sensor 52.

[0149] Further, the second part 532 of the force transmission shaft 53 is provided with a plurality of circumferentially distributed ribs 5321. The ribs 5321 of the force transmission shaft 53 are uniformly arranged in the circumferential direction, so as to ensure that the stiffness of the force transmission shaft 53 in each direction is uniform.

[0150] Referring to Figure 6 , Figure 7 , the friction block base 6 comprises a platform part 61 and three support rod parts 62. The platform part 61 is parallel to the mounting plane of the mounting base 1 and is spaced apart from the mounting plane by a distance. The platform part 61 is preferably an equilateral triangle or a hexagon. The center of the platform part 61 is provided with a square friction block mounting groove 611, and a center through hole 613 is arranged at the bottom center of the friction block mounting groove 611.

[0151] Referring to Figure 6 , Figure 7 , the three support rod parts 62 are inclined and protrude from the three vertices of the triangular platform part 61 to the direction of the mounting plane, or are inclined and protrude from the three sides of the hexagonal platform part 61 to the direction of the mounting plane. The central axes of the three support rod parts 62 are orthogonal to each other, and the central intersection point is located on the central vertical line of the platform part 61, as shown in Figure 6 , Figure 7 , Figure 8 The central axes of the three support rod parts 62 respectively extend along the three directions of the first coordinate system x1-y1-z1, as shown in Figure 9 , Figure 11 .

[0152] One end of the three support rod portions 62 is fixedly connected with the platform portion 61, and the other end is provided with a groove on the milled surface, and a fifth threaded hole 621 is arranged at the bottom of the groove. The fifth threaded hole 621 is perpendicular to the milled surface of the support rod portion 62. In some embodiments, the three support rod portions 62 are integrally formed with the platform portion 61.

[0153] Referring to Figure 12 The friction block 7 comprises a friction block friction end 71, a friction block pressing platform 72 and a friction block mounting end 73 connected in sequence. The friction block friction end 71 is a rectangular block, comprising a friction block contact surface 711, which is the side surface of the friction block friction end 71 adjacent to the center of the friction block pressing platform 72. The friction block pressing platform 72 is a disc-shaped flat plate, and a plurality of through holes are uniformly distributed around the periphery. The friction block mounting end 73 is a square block, and the bottom is provided with a threaded hole.

[0154] The friction block mounting end 73 is clamped into the friction block mounting groove 611, and the fixing screw is inserted into the threaded hole of the friction block mounting end 73 of the friction block 7 from the center through hole 613, so as to fix the friction block 7 on the friction block base 6. In order to further improve the mounting and fastening degree of the friction block 7, a plurality of fourth threaded holes 612 are further arranged on the platform portion 61, which are matched with the through holes on the friction block pressing platform 72, and the friction block 7 can be further fastened with the friction block base 6 through the screws.

[0155] The friction block 7 is fastened on the friction block base 6 by the screw, and the friction block 7 serves as a static part of the friction pair, and the friction block contact surface 711 of the friction block friction end 71 bears the contact force of the relative motion between the friction pairs and transmits the contact force to the friction block base 6.

[0156] In the force measuring device, the size of the rib 5321 of the force transmission shaft 53 determines the transverse bending stiffness K b and the axial tension and compression stiffness K p and the decoupling degree of the force transmission shaft 53, and the size of the rib 5321 can be adjusted according to the required transverse bending stiffness K b and the axial tension and compression stiffness K p and the decoupling degree.

[0157] The decoupling degree can be calculated according to the theoretical formula. Based on the formula, the size of the rib 5321 can be designed according to the required transverse bending stiffness K b and the axial tension and compression stiffness K p and the decoupling degree, and in the case of a certain decoupling degree γ, the more the number of ribs 5321, the greater the transverse bending stiffness K b and the axial tension and compression stiffness K pThe larger. Given the size of the ribs 5321, the number of ribs 5321 depends on the diameter of the force transmission shaft 53 and the gap size between different ribs 5321, while the gap size depends on the machining process, and when the machining process allows, the smaller the gap between the ribs 5321, the more the number of ribs 5321, the larger the lateral bending stiffness K b and the axial tension and compression stiffness K p , and thus the higher the structural stiffness of the measuring device.

[0158] In the present application, the lateral bending stiffness K b of the force transmission shaft 53 is less than or equal to 1% of the axial tension and compression stiffness K p .

[0159] Wherein, K b and K p may be calculated by the following formula respectively:

[0160]

[0161]

[0162]

[0163] γ represents the decoupling degree;

[0164] L represents the length of the ribs 5321 of the force transmission shaft 53;

[0165] A n represents the cross-sectional area of a single rib 5321;

[0166] n represents the number of ribs;

[0167] E represents the elastic modulus of the material of the force transmission shaft 53.

[0168] According to the force measuring device of the present application, when the friction block 7 is subjected to three-way contact force load, the force load is transmitted to the first force transmission structure base 2, the second force transmission structure base 3 and the third force transmission structure base 4 through the force transmission structure 5, the three-way orthogonal force transmission structure 5 transmits different directions of force respectively, and the size of the axial force load is measured through the force sensor 52. Since the friction block base 6 connects the three-way orthogonal force transmission structure 5 together, in order to avoid the influence of force coupling between the force measuring results, the specific force transmission shaft 53 is used as the core part of the force transmission structure 5. The two ends of the force transmission shaft 53 are connected with the connecting shaft 54 and the force sensor 52 respectively, and the connection mode can be designed according to the size of the connecting shaft 54 and the force sensor 52. The second part 532 of the force transmission shaft 53 is designed with a special structure, and the rib 5321 is used as a flexible hinge structure. The axial size of the rib 5321 is larger than the cross-sectional size, so as to ensure that the lateral bending stiffness of the rib 5321 is much lower than the axial tensile and compressive stiffness, so as to ensure that the axial tensile and compressive stiffness K p of the force transmission shaft 53 composed of the rib 5321 is much higher than the lateral bending stiffness K b .

[0169] Compared with the prior art, the force measuring device provided by the embodiment effectively reduces the force coupling between the three-way contact force measurement, improves the measurement accuracy, and effectively eliminates the influence of the contact force level on the relative error of the three-way contact force measurement by using the force transmission structure 5 arranged in the three-way orthogonal direction of the first coordinate system and measuring the contact force, and using the third coordinate system to define the friction block contact surface 711. The introduction of the third coordinate system enables the measuring device to measure the contact surface of the turbine blade with different engagement angles. Specifically, different angle friction blocks can be designed for different engagement angles.

[0170] By using the above arrangement scheme of the force transmission structure 5 and connecting them together through the friction block base 6, the friction block 7 is extended, the accessibility of the friction block 7 is ensured, and the friction pair static part for the small size structure such as the shroud contact surface of the turbine blade of the aero-engine is provided, so as to measure the contact force of the contact interface. The three-way force transmission structure 5 is connected together through the friction block base 6 to provide stiffness for the friction block 7, so as to realize the provision of sufficient structural stiffness for the friction block 7 under the condition of ensuring that the size of the friction block 7 is small and accessible. The sliding rail and sliding block are moved to adjust the force measuring assembly, so as to avoid the gap or interference problem between the contact surfaces caused by the assembly positioning and machining error, thereby improving the measurement accuracy.

[0171] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method of measuring a contact interface mechanical property curve, the method comprising: The method comprises the following steps: S1: mounting the blade root of the aero-engine turbine blade on the fixture of the test bed; S2: mounting the force measuring device on the corresponding position of the test bed; S3: connecting the force sensor in the force measuring device to the data acquisition card, and connecting the data acquisition card to the computer for data processing; S4: adjusting the relative position of the force measuring device and the aero-engine turbine blade and fixing: the friction block contact surface of the friction block of the force measuring device abuts against the contact surface of the crown of the aero-engine turbine blade, and then the force measuring assembly of the force measuring device is fixed on the mounting base; S5: pasting the acceleration sensor on the contact surface of the crown of the aero-engine turbine blade, and connecting the acceleration sensor to the data acquisition card; S6: applying excitation to the aero-engine turbine blade; recording the measurement data of the force sensor and the acceleration sensor through the data acquisition card; S7: calculating and analyzing the measurement data to obtain the mechanical property curve of the contact interface of the aero-engine turbine blade; In step S2, the following steps are included: S21: mounting the force measuring assembly on the mounting base; first, mounting the three force transmission structure bases of the force measuring assembly on the mounting base, then fixing the three assembled force transmission structures on the mounting inclined surfaces of the three force transmission structure bases, and the extension directions of the three force transmission structures are x1, y1 and z1 directions of the first rectangular coordinate system; adjusting the positions of the three force transmission structure bases, and finally mounting the friction block base with the fixed friction block on the top ends of the three force transmission structures; S22: fixing the mounting base on the corresponding position of the test bed; In step S3, the following steps are included: S31: connecting the force sensor to the data acquisition card; S32: connecting the data acquisition card to the computer and data acquisition software, and starting signal sampling; S33: transforming and processing the signal of the force sensor in the computer and data acquisition software to obtain the contact force measurement result in the third rectangular coordinate system; the third rectangular coordinate system takes the plane where the friction block contact surface is located as the x3-y3 plane, and takes the direction perpendicular to the friction block contact surface as the z3 direction; S34: removing the zero drift of the force sensor signal to remove the zero point drift of the signal.

2. The contact mechanics property curve measurement method according to claim 1, characterized in that, In step S21, one or two groups of the force measuring assembly are selected to be mounted on the mounting base.

3. The contact mechanics property curve measurement method according to claim 2, characterized in that, In step S22, the position of the mounting base is adjusted so that the distance between the friction block contact surface of the friction block and the crown contact surface is not greater than 3mm.

4. The contact mechanics property curve measurement method according to claim 3, characterized in that, In step S4, the positions of the mounting base and the force measuring assembly are adjusted so that the contact force measurement result in the z3 direction of the third rectangular coordinate system is between 0.1N and 0.2N, and then the force measuring assembly is fixed on the mounting base.

5. The contact mechanics property curve measurement method according to claim 4, characterized in that, In step S5, two one-way acceleration sensors or one multi-way acceleration sensor are pasted on the shroud contact surface of the turbine blade of the aero-engine, the pasting directions of the two one-way acceleration sensors are along the y3 direction and the z3 direction respectively; the multi-way acceleration sensor is selected as a two-way acceleration sensor, the directions are along the y3 direction and the z3 direction respectively.

6. The contact mechanics property curve measurement method according to claim 5, characterized in that, In step S6, the excitation applied to the aero-engine turbine blade A is vibration excitation, the excitation is selected as simple harmonic excitation, the direction is perpendicular to the blade surface.

7. The contact mechanics property curve measurement method according to claim 6, characterized in that, Step S7 comprises the following steps: S71: filtering the recorded contact force signals and acceleration sensor signals in the third rectangular coordinate system to remove low-frequency components and unnecessary high-frequency noise in the data; S72: twice integrating the acceleration signals of the shroud contact surface of the aero-engine turbine blade A measured by the acceleration sensor in the y3 and z3 directions to obtain the displacement of the shroud contact surface; S73: drawing a "force-displacement" curve according to the measured contact force signals and the processed shroud contact surface displacement signals.

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