CN115931565A - Intersection point load actual measurement and verification method of statically indeterminate installation engine - Google Patents
Intersection point load actual measurement and verification method of statically indeterminate installation engine Download PDFInfo
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Abstract
The invention has established the actual measurement of point load of point of intersect and verified method of a hyperstatic installation aeroengine, at first, design and install the strain bridge circuit, have developed the single load calibration test of thrust pin, vertical/horizontal tie rod in the engine/outside, have adopted the gradual multiple linear regression method to establish the strain-load equation of each point of intersect load component; then, an on-machine load calibration test of the thrust pin and the vertical/horizontal pull rod in/out of the engine is carried out, and a method for verifying the rationality and the prediction precision of the strain-load equation is established by using calibration test data. The invention avoids the problem that the constructed load equation has multiple collinearity to influence the robustness, improves the prediction precision of the equation, provides a technical path for verifying the rationality of the hyperstatic mounting aeroengine strain-load equation constructed based on the single load calibration test data, and provides reliable support for the flight actual measurement of the aeroengine mounting intersection point load.
Description
Technical Field
The invention belongs to the technical field of health monitoring of aircraft engine mounting structures, and particularly relates to an intersection point load actual measurement and verification method of an statically indeterminate mounted engine.
Background
The mounting and supporting structure of the aircraft engine belongs to a critical part of fatigue fracture, and once the mounting and supporting structure fails, the engine loses effective support and is out of control, so that the flight safety is influenced. Therefore, the actual load of the engine directly acting on the airframe structure in the flight process of the airplane is obtained, the strength design rationality of the engine installation supporting structure is verified, the health monitoring of the structure is carried out, and the method is very important for ensuring the safety of the airplane.
A great deal of research and application are carried out on the thrust actual measurement Method of the aircraft engine at home and abroad, two mature thrust measurement methods are formed, namely a Gas Generator Method (GGM) and a direct measurement Method, and the two methods are successfully applied to various airplanes.
The GGM method needs to be additionally provided with a large number of sensors for temperature, pressure, flow and the like on an engine, and has the disadvantages of complex calculation model, high cost and few applications at present. The direct measurement method arranges the strain bridge circuit on the installation section of the engine without establishing a complex calculation model, and has relatively simple modification and test and high reliability.
In the existing research application, most of research objects are three-point statically determinate engines, and only the thrust of the engines is measured. However, the main mounting intersection point of the aircraft engine generally bears bidirectional or three-way loads, and only obtaining the thrust of the engine is not enough for strength check and health monitoring of an engine mounting support structure. Particularly, for an engine adopting four-point hyperstatic mounting, intersection point loads of mounting intersection points are accurately obtained, a set of verification method is established, and corresponding research is lacked at present.
Disclosure of Invention
The purpose of the invention is as follows: the invention solves the problem of obtaining the engine installation intersection point load in the actual flight of the serving airplane by establishing an intersection point load actual measurement and verification method of the hyperstatic installation aircraft engine, and provides more accurate load input for strength check and health monitoring of an engine installation support structure. The invention uses the thought of a direct thrust measurement method for reference to measure the intersection point load of a four-point statically indeterminate mounted engine. Firstly, designing a strain bridge circuit, developing an independent load calibration test of an engine mounting section, and establishing a strain-load equation of load components of each intersection point by adopting a step-by-step multiple linear regression method; and then, establishing a method for verifying the rationality and the prediction precision of the load equation by using the onboard load calibration test data.
The technical scheme of the invention is as follows:
the hyperstatic four-point mounting engine is mounted on an airplane through an inner thrust pin, an outer thrust pin, a vertical pull rod and a horizontal pull rod. Wherein, the inner/outer thrust pin fixes one end on the machine body structure through two mounting joints, the other end is connected with the engine in a hinged mode, and the axis of the inner/outer thrust pin is parallel to the ground and vertical to the course; the inner thrust pin restrains course and vertical translational displacement of the engine, and the outer thrust pin restrains lateral, course and vertical translational displacement of the engine.
One end of the vertical/horizontal pull rod is connected with the engine body in a hinged mode, the other end of the vertical/horizontal pull rod is connected with the engine in a hinged mode, the vertical pull rod restrains vertical translational displacement of the engine, and the horizontal pull rod restrains lateral translational displacement of the engine.
The coordinate system is established as follows: the origin is 270mm above the aircraft nose, the Y axis is the symmetry axis of the aircraft, and is located on the manufacturing horizontal line plane of the aircraft body, and is positive backwards; the Z axis is vertical to the Y axis and is upward positive in the plane of symmetry; the X axis is perpendicular to the YZ plane and points to the left wing direction as positive.
Aiming at the intersection point load actual measurement and verification method of the hyperstatic four-point mounting engine, the invention provides the following scheme, comprising the following steps:
the method comprises the following steps: and strain bridges are designed on the inner/outer thrust pins and the vertical/horizontal pull rods.
Ten groups of strain bridges are arranged on the inner/outer thrust pins; the front and back surfaces of the area of the first section are respectively provided with a group of shear bridges, the upper and lower surfaces of the area of the first section are respectively provided with a group of shear bridges and a group of tension and compression bridges, the front and back surfaces of the area of the second section are respectively provided with a group of shear bridges, and the upper and lower surfaces of the area of the second section are respectively provided with a group of shear bridges;
the first section is positioned between the two mounting sections, and the second section is positioned between the mounting sections and the engine;
and a group of tension and compression bridges are symmetrically arranged on two sides of the outer surface of the middle part of the cylinder of the vertical/horizontal pull rod respectively.
Step two: carrying out individual load calibration tests on the inner/outer thrust pins and the vertical/horizontal pull rods;
the inner thrust pin and the outer thrust pin are fixed by two mounting joint dummy pieces respectively, and the fixing mode is the same as the mounting mode of the inner thrust pin and the outer thrust pin on the machine; the vertical/horizontal pull rod is fixed by an axial force loading device respectively.
For the thrust pin, firstly, respectively carrying out unidirectional loading calibration tests in all directions, wherein the inner thrust pin comprises 4 working conditions of course pulling and pressing and vertical pulling and pressing, and the outer thrust pin comprises 6 working conditions of lateral pulling and pressing and course pulling and pressing and vertical pulling and pressing; and then carrying out a bidirectional or three-way composite loading calibration test, dividing the test according to an included angle between resultant force of the course and the vertical load and the Z-axis forward direction, wherein the inner thrust pin composite loading calibration test comprises the following five working conditions: the test of the composite loading calibration of the thrust pin at the outer side comprises the following six working conditions: 126.8 °, 158.0 °, 187.5 °, 314.8 °, 37.0 ° 78.0 °.
For the vertical/horizontal pull rod, the actuator cylinders respectively apply axial tension/compression loads to carry out calibration tests.
Step three: carrying out on-machine load calibration tests on the inner/outer thrust pins and the vertical/horizontal pull rods;
designing an engine dummy piece, and mounting the engine dummy piece on an airplane through an inner thrust pin, an outer thrust pin and a vertical/horizontal pull rod; the aircraft is fixed on a ground rail through a dummy wheel of the landing gear, wherein the front landing gear restrains the vertical translational displacement of the aircraft, and the left/right main landing gears restrain the lateral, course and vertical translational displacement of the aircraft.
The engine dummy part is provided with five loading points, namely a first lateral loading point and a first vertical loading point which are positioned in front of the course and in front of the inside and outside thrust pins, a course loading point and a second lateral loading point which are positioned behind the course, and a second vertical loading point which is positioned in the middle and behind the vertical/horizontal pull rod;
the working conditions of the on-machine load calibration test of the inner/outer thrust pin and the vertical/horizontal pull rod comprise: the method specifically comprises the following steps of loading one pure course and six composite loads, wherein the six composite loads specifically comprise: one of (lateral +, vertical +), (lateral +, vertical-), (lateral-, vertical-), "+" indicates that the load is positive, and "-" indicates that the load is negative.
Step four: the test data of the single load calibration test and the onboard load calibration test of the inner/outer thrust pin and the vertical/horizontal pull rod are preprocessed, and the method comprises the following steps: in test data, data of the strain bridges responding to the linear section with the loading ratio of 50% -100% are reserved, other data are eliminated, and the quantity of the data eliminated by each group of strain bridges is the same under each working condition.
Step five: dividing test data of an individual load calibration test into a regression data set and a check data set according to the load size and direction of different load calibration working conditions, dividing the working conditions into a regression working condition and a check working condition, wherein the regression working condition and the check working condition both cover the positive direction and the negative direction of a load component, the load size of the regression working condition covers a typical value, and the number of the regression working conditions is more than the number of the check working conditions; then, the load and the bridge data corresponding to the regression working condition are used as regression data sets, and the load and the bridge data of the verification working condition are used as verification data sets.
Step six: constructing respective 'strain-load' equation sets respectively based on regression data sets of the inner thrust pin, the outer thrust pin and the vertical/horizontal pull rod; the equation of the vertical/horizontal pull rod is constructed by adopting a traditional linear regression method, and the equation of the inner/outer thrust pin is constructed according to the following method and steps:
step six A: calculating covariance correlation coefficients between the load vectors and each group of bridge strain response vectors in the regression data set, and eliminating strain bridges with the covariance correlation coefficients smaller than r 1; r1 is in a value range of [0.3,0.5];
step six B: calculating covariance correlation coefficients between response data of any two groups of strain bridges in the residual strain bridges, and screening all strain bridge combinations with covariance correlation coefficients smaller than r2 between any two groups, wherein the value range of r2 is [0.9,0.95];
step six C: in all the strain bridge combinations screened in the step six B, constructing a strain-load equation of each bridge combination based on a stepwise linear regression method so as to fit goodness of fit (R) 2 ) Maximum criterion, respectively determining the optimal equation in the strain-load equation containing the bn = 2-k sets of bridges, wherein k represents the number of bridges of the combination containing the most bridges found in step six B.
Step seven: and substituting the bridge data in the verification data set into the k-1 groups of strain-load equations established in the step six, predicting to obtain a load value, comparing the load value with the load in the verification data set, calculating the relative error between the load value and the load in the verification data set, and selecting an equation with the minimum predicted relative error as an optimal strain load equation.
Step eight: respectively substituting the test data of the on-machine load calibration test preprocessed in the fourth step into an optimal strain-load equation of the inner/outer thrust pin and the vertical/horizontal pull rod, and solving the following intersection point loads (namely internal forces) acting on the engine dummy member: load component F of outer thrust pin at intersection point in X, Y and Z directions x outer side 、F Outside y 、F z outer Load component F at intersection point of inner thrust pin in Y and Z directions In y 、F In z Vertical load P of vertical tie rod z is perpendicular to Side load P of horizontal tie rod x level ；
Step nine: calculating resultant force and resultant moment of the intersection point loads (belonging to internal force) obtained in the step eight on the appointed direction of the engine by adopting the intersection point loads (belonging to internal force); and (3) calculating the resultant force and the resultant moment of the external load (belonging to the external force) on the engine loading point in the specified direction of the engine by using the external load. The method comprises the following steps:
step nine A: calculating course load resultant force Py, vertical load resultant force Pz and resultant moment Mz of an inner thrust pin hinge pivot of the engine dummy part caused by the internal force by adopting formulas (1) to (3);
Py＝ F outside y + F In y (1)
Pz＝ F z outer + F In z +P z is perpendicular to (2)
Mz＝P x level ×L 1 + F Outside y ×L 2 (3)
Wherein L is 1 Is the Y-direction distance, L, between the horizontal pull rod and the inner thrust pin 2 The distance between the load action point of the intersection point of the outer thrust pin and the hinge fulcrum of the inner thrust pin is in the X direction;
step nine B: calculating course load resultant force Py ' of the engine dummy part, vertical load resultant force Pz ' and resultant force Mz ' of a hinge pivot of the inner thrust pin, which are caused by external force, by adopting the steps (4) to (6);
Py＇＝ P y9015 (4)
Pz＇＝ P z9012 +P z9013 (5)
Mz＇＝ P x9011 ×L 3 + P z9014 ×L 4 + P y9015 ×L 5 (6)
L 3 the Y-direction distance, L, between the first side direction loading point and the inner side thrust pin 4 The Y-direction distance, L, between the second side loading point and the inner side thrust pin 5 The distance between the heading loading point and the inner thrust pin in the X direction is obtained.
Step ten: and comparing whether the resultant force and the resultant moment obtained by respectively calculating the intersection point load and the external load are balanced or not, if so, indicating that a strain-load equation established according to test data of a single load calibration test is reasonable and has enough precision, and the method can be used for predicting the intersection point load of the inner/outer thrust pin and the vertical/horizontal pull rod in actual flight. The method comprises the following steps:
step ten A: respectively combining Py and Py ', pz and Pz ', mz and Mz ', fitting the linear relation by least square regression, and if the absolute value of the fitting slope is within 1 +/-0.03, fitting goodness (R) 2 ) If the average load is more than 0.99, the high coincidence of Py and Py ', pz and Pz ', and Mz ' is shown, the balance of Py and Pz ' and Mz ' is realized, the fact that the load of the thrust pin on the machine can be accurately predicted through the optimal strain-load equation established through single load calibration test data is indirectly proved, and the optimal strain-load equation can be used for subsequent actual measurement of the load of the installation intersection point of the engine;
otherwise the optimal strain-load equation is not available. In this case, find the unbalanced term and execute step B.
Step ten B: and returning to the seventh step, removing the corresponding strain-load equation in the tenth step A aiming at the unbalanced item of the resultant force or the resultant moment in the tenth step A, selecting one group with the highest prediction precision in the residual equation set, and executing the eighth step, the ninth step and the tenth step A again.
The invention has the beneficial effects that:
the intersection point load actual measurement and verification method for the hyperstatic installation aero-engine provided by the invention avoids the problem that the robustness is influenced due to the multiple collinearity of the constructed load equation, improves the prediction precision of the equation, establishes the technical method for verifying the rationality and the accuracy of the load equation based on the on-board load calibration test data, and provides reliable support for the flight actual measurement of the engine installation intersection point load.
Drawings
FIG. 1 is a technical flow chart of the method of the present invention;
FIG. 2 is a schematic view of an engine mounting arrangement;
FIG. 3 is a schematic view of the thrust pin and fuselage structural connection, wherein the letters C and D respectively represent a first section and a second section of the thrust pin bridge installation;
FIG. 4 is a schematic diagram of the distribution of loading points of a dummy part of an on-board load calibration test engine, wherein 1 is an inner thrust pin, 2 is an outer thrust pin, 3 is a vertical pull rod, 4 is a horizontal pull rod, 9011 is a first lateral loading point, 9012 is a first vertical loading point, 9013 is a second vertical loading point, 9014 is a second lateral loading point, and 9015 is a course loading point;
FIG. 5 is a flow chart of load equation establishment;
FIG. 6 is a load equation validation flow chart;
fig. 7 is a schematic diagram comparing resultant force and resultant moment caused by internal and external forces on an engine dummy, wherein fig. 7 (a) is a comparison of course load resultant force caused by the internal and external forces, fig. 7 (b) is a comparison of vertical load resultant force caused by the internal and external forces, and fig. 7 (c) is a comparison of Z-direction resultant moment caused by the internal and external forces.
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.
A cross point load actual measurement and verification method of a statically indeterminate installation engine is disclosed, the flow of the method is shown in a figure 1, and one of possible embodiments comprises the following steps:
in the first step, for the aeroengine adopting the four-point statically indeterminate installation shown in fig. 2, 10 sets of strain bridges are respectively arranged on the inner/outer thrust pins in consideration of the installation effect and the cross shaft effect, wherein 5 sets are backup bridges, and the strain bridges are positioned on a first section C and a second section D shown in fig. 3, wherein the section C is between two installation joints, and the section D is between the installation joints and the engine; the cross section C comprises two groups of shear bridges on the front and rear surfaces, two groups of shear bridges on the upper and lower surfaces and two groups of tension and compression bridges; the cross section D comprises two groups of shear bridges on the front surface and the rear surface, and two groups of shear bridges on the upper surface and the lower surface. Two groups of tension and compression bridges are arranged on the outer surface of the middle part of the cylindrical barrel of the vertical/horizontal pull rod. All bridges are full bridges.
Secondly, carrying out individual load calibration tests of the inner/outer thrust pin and the vertical/horizontal pull rod, and fixing the inner/outer thrust pin and the vertical/horizontal pull rod respectively by using a mounting joint dummy piece in the same way as the mounting mode on the machine; the vertical/horizontal pull rod is fixed by an axial force loading device respectively.
The single load calibration test is to perform unidirectional loading calibration tests in all directions on the thrust pin, wherein the inner thrust pin comprises 4 working conditions of course pulling, pressing, vertical pulling and pressing, and the outer thrust pin comprises 6 working conditions of lateral pulling and pressing, and course pulling, pressing, vertical pulling and pressing; then a calibration test of bidirectional or three-way composite loading is carried out, the calibration test is divided according to the included angle between the resultant force of the course direction and the vertical load and the forward direction of the Z axis, the composite loading working conditions of 5 different resultant force angles (107.6 degrees, 112.4 degrees, 99.2 degrees, 63.6 degrees and 224.4 degrees) are designed in the YZ plane in the inner thrust pin composite loading calibration test, the composite loading working conditions of 6 different resultant force angles (126.8 degrees, 158.0 degrees, 187.5 degrees, 314.8 degrees and 37.0 degrees 78.0 degrees) are designed in the YZ plane in the outer thrust pin composite loading calibration test, and the typical stress form of the thrust pin is covered; and for the vertical/horizontal pull rod, the vertical/horizontal pull rod is fixed on an axial force loading device, axial loading is carried out through the actuating cylinder, and a calibration test under the conditions of pulling load and pressing load is carried out.
Thirdly, designing an engine dummy part, replacing an engine real part with the same connection form through an inner thrust pin, an outer thrust pin and a vertical/horizontal pull rod, installing the engine dummy part on an airplane, designing 5 loading points on the dummy part, and applying lateral, heading and vertical loads in a combined manner as shown in fig. 4; the aircraft is fixed on a ground rail through a dummy wheel of the landing gear, wherein the front landing gear restrains the vertical translational displacement of the aircraft, and the left/right main landing gears restrain the lateral, course and vertical translational displacement of the aircraft.
The engine dummy is provided with five loading points, as shown in fig. 4, a first lateral loading point 9011 and a first vertical loading point 9012 which are positioned in front of the course and in front of the inside and outside thrust pins, a course loading point 9015 and a second lateral loading point 9014 which are positioned behind the course, and a second vertical loading point 9013 which is positioned in the middle and behind the vertical/horizontal tie rod;
the calibration working conditions comprise: the loading device comprises 1 pure heading loading working condition and 6 lateral and vertical combined loading working conditions, wherein the pure heading loading working condition comprises one (lateral plus vertical plus) and three (lateral plus vertical plus), the two (lateral plus vertical plus), the plus represents that the load is positive, and the minus represents that the load is negative. The force and moment of the external load on the airplane are balanced by applying trim load on a main bearing frame of the front fuselage and a drag parachute joint above an engine.
And fourthly, preprocessing test data of the independent load calibration test and the onboard load calibration test of the inner/outer thrust pin and the vertical/horizontal pull rod, wherein the test data comprises the following steps: in test data, data of the strain bridges responding to the linear section with the loading ratio of 50% -100% are reserved, other data are eliminated, and the quantity of the data eliminated by each group of strain bridges is the same under each working condition.
And fifthly, dividing the test data of the single load calibration test into a regression data set and a verification data set, wherein 5 working conditions of the inner thrust pin are used as regression working conditions, the rest 4 working conditions are used as verification working conditions, 8 working conditions of the outer thrust pin are used as regression working conditions, and 4 working conditions are used as verification working conditions. And the load and the bridge data corresponding to the regression working condition are used as a regression data set, and the load and the bridge data of the verification working condition are used as a verification data set.
Sixthly, constructing course strain-load equations of the inner thrust pin containing 2 and 3 sets of electric bridges and a vertical load equation containing 2 sets of electric bridges; the outer thrust pin comprises lateral strain-load equations of 2 and 3 sets of electric bridges, heading strain-load equations of 2 and 3 sets of electric bridges and vertical load equations of 2 and 3 sets of electric bridges; the vertical and horizontal tie rods contain a set of strain-load equations for the bridge.
The strain-load equation is of the form:
Load＝c1×bridge1+c2×bridge2+c3×bridge3+…。
wherein c1, c2, c3 and r 8230denote coefficients, bridge1, bridge2, bridge3 and r 8230denote response values of a bridge, and Load is a Load value obtained through prediction.
And seventhly, substituting corresponding bridge data in the checking data set into the strain-load equation set established in the sixth step, predicting to obtain a load value, and selecting the equations with 2 groups of bridges for the heading and the vertical optimal strain-load equations of the inner thrust pin by calculating the relative error with the load in the checking data set, wherein the equations with 3 groups of bridges, 2 groups of bridges and 2 groups of bridges are respectively used as the lateral, heading and vertical optimal strain-load equations of the outer thrust pin.
And eighthly, substituting bridge data of the on-board load calibration test preprocessed in the fourth step into the optimal strain-load equation of the inner/outer thrust pin and the vertical/horizontal pull rod in the seventh step respectively to solve the following intersection point loads (namely internal forces) acting on the engine dummy member: load component F of intersection point of outer thrust pin along X, Y and Z directions Outside x 、F Outside y 、F z outer Load component F at intersection point of inner thrust pin in Y and Z directions In y 、F In z Vertical load P of vertical tie rod z is perpendicular to Side load P of horizontal pull rod x level 。
And step nine, respectively adopting the intersection point load (belonging to internal force) acting on the engine dummy piece and the external load (belonging to external force) on the loading point of the engine dummy piece, and calculating resultant force and resultant moment in the appointed direction of the engine dummy piece, wherein the numerical values of the resultant force and the resultant moment are shown in figure 7.
Tenth step, respectively fitting and calculating course load resultant force, vertical load resultant force, slope of resultant moment Mz of hinge pivot of inner thrust pin and fitting goodness R of the two 2 As shown in fig. 7, the absolute values of the slopes are 0.9948, 1.0073 and 1.0229, which are all in the range of 1 ± 0.03; goodness of fit R 2 0.9998, 0.9986, 0.9952, respectively, all greater than 0.995. The results show that the two have high coincidence, and the resultant force and resultant moment of the engine caused by internal force and external force are balanced, so that the load equation established by the data of the independent load calibration tests of the internal/external thrust pins and the vertical/horizontal pull rods can accurately predict the intersection point load of the aeroengine with four-point hyperstatic mounting on the aircraft, and can be used for the subsequent actual measurement of the mounting intersection point load of the engine.
The above description is only one of the specific embodiments of the present invention, and the present invention will be described in detail, but not be limited to the conventional technology. The scope of the present invention is not limited thereto, and any changes or substitutions that can be easily made by those skilled in the art within the technical scope of the present invention will be covered by the scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An intersection point load actual measurement and verification method of a hyperstatic installation engine is characterized by comprising the following steps: the engine is arranged on the machine body structure by adopting an inner/outer thrust pin and a vertical/horizontal pull rod; the inner/outer thrust pin is respectively fixed at one end on the machine body structure through two mounting joints, the other end is connected with the engine in a hinged mode, and the axis of the inner/outer thrust pin is parallel to the ground and vertical to the course; the inner thrust pin restricts the course and vertical translational displacement of the engine, and the outer thrust pin restricts the lateral, course and vertical translational displacement of the engine;
one end of the vertical/horizontal pull rod is connected with one machine body frame in a hinged mode, the other end of the vertical/horizontal pull rod is connected with the engine in a hinged mode, the vertical pull rod restrains the vertical translational displacement of the engine, and the horizontal pull rod restrains the lateral translational displacement of the engine;
the coordinate system is established as follows: the origin is 270mm above the aircraft nose, the Y axis is the symmetry axis of the aircraft, is positioned on the manufacturing horizontal line plane of the aircraft body and is positive backwards; the Z axis is vertical to the Y axis and is upward positive in the plane of symmetry; the X axis is vertical to the YZ plane and points to the left wing direction as positive;
the method comprises the following steps:
the method comprises the following steps: strain bridges are designed on the inner/outer thrust pins and the vertical/horizontal pull rods;
step two: carrying out individual load calibration tests on the inner/outer thrust pins and the vertical/horizontal pull rods;
step three: carrying out on-machine load calibration tests on the inner/outer thrust pins and the vertical/horizontal pull rods;
step four: preprocessing test data of an independent load calibration test and an onboard load calibration test of the inner/outer thrust pin and the vertical/horizontal pull rod;
step five: dividing the test data of the preprocessed single load calibration test into a regression data set and a check data set according to the load size and the load direction; the regression data set and the calibration data set both comprise loads and bridge response data corresponding to the loads;
step six: constructing respective 'strain-load' equation sets respectively based on regression data sets of the inner thrust pin, the outer thrust pin and the vertical/horizontal pull rod;
step seven: verifying the load equation set in the step six based on a verification data set, and selecting an optimal 'strain-load' equation with highest prediction precision;
step eight: substituting the on-board load calibration data preprocessed in the fourth step into the optimal strain-load equation in the seventh step, and calculating to obtain intersection point loads at the joints of the inner/outer thrust pins, the vertical/horizontal pull rods and the engine;
step nine: calculating resultant force and resultant moment of the intersection point loads (belonging to internal force) obtained in the step eight on the appointed direction of the engine by adopting the intersection point loads (belonging to internal force); calculating resultant force and resultant moment of the external load (belonging to external force) on the engine loading point in the specified direction of the engine;
step ten: and comparing whether the resultant force and the resultant moment obtained by respectively calculating the intersection point load and the external load are balanced or not, if so, indicating that a strain-load equation established according to test data of a single load calibration test is reasonable and has enough precision, and the method can be used for predicting the intersection point load of the inner/outer thrust pin and the vertical/horizontal pull rod in actual flight.
2. The method for intersection load measurement and verification of a statically indeterminate mount engine as claimed in claim 1, wherein: in the first step, ten groups of strain bridges are arranged on the inner/outer thrust pins; the front and back surfaces of the area of the first section are respectively provided with a group of shear bridges, the upper and lower surfaces of the area of the first section are respectively provided with a group of shear bridges and a group of tension and compression bridges, the front and back surfaces of the area of the second section are respectively provided with a group of shear bridges, and the upper and lower surfaces of the area of the second section are respectively provided with a group of shear bridges;
the first section is positioned between the two mounting sections, and the second section is positioned between the mounting sections and the engine;
and a group of tension and compression bridges are symmetrically arranged on two sides of the outer surface of the middle part of the cylinder of the vertical/horizontal pull rod respectively.
3. The method of claim 2 for cross-point load measurement and verification of a statically indeterminate mount engine, characterized in that: in the second step, the inner thrust pin and the outer thrust pin are fixed by two mounting joint fake pieces respectively, and the fixing mode is the same as the mounting mode of the inner thrust pin and the outer thrust pin on the machine; fixing the vertical/horizontal pull rod by using an axial force loading device respectively;
for the thrust pin, firstly, respectively carrying out unidirectional loading calibration tests in all directions, wherein the inner thrust pin comprises 4 working conditions of course pulling and pressing and vertical pulling and pressing, and the outer thrust pin comprises 6 working conditions of lateral pulling and pressing and course pulling and pressing and vertical pulling and pressing; and then performing a bidirectional or three-way composite loading calibration test, dividing the test according to an included angle between the resultant force of the course and the vertical load and the Z-axis forward direction, wherein the inner thrust pin composite loading calibration test comprises the following five working conditions: the test of the composite loading calibration of the thrust pin at the outer side comprises the following six working conditions: 126.8 °, 158.0 °, 187.5 °, 314.8 °, 37.0 ° 78.0 °;
for the vertical/horizontal pull rod, the actuator cylinders respectively apply axial tension/compression loads to carry out calibration tests.
4. The method of claim 3 for cross-point load measurement and verification of statically indeterminate mount engines, characterized by: in the third step, an engine dummy piece is designed, and the engine dummy piece is arranged on the airplane through an inner/outer thrust pin and a vertical/horizontal pull rod;
the aircraft is fixed on a ground rail through a dummy wheel of the landing gear, wherein the front landing gear restrains the vertical translational displacement of the aircraft, and the left/right main landing gears restrain the lateral, course and vertical translational displacement of the aircraft;
the engine dummy part is provided with five loading points, namely a first lateral loading point and a first vertical loading point which are positioned in front of the course and in front of the inside and outside thrust pins, a course loading point and a second lateral loading point which are positioned behind the course, and a second vertical loading point which is positioned in the middle and behind the vertical/horizontal pull rod;
the working conditions of the on-machine load calibration test of the inner/outer thrust pin and the vertical/horizontal pull rod comprise: the method specifically comprises the following steps of loading one type of pure course and six types of compound loading, wherein the steps of: one of (lateral +, vertical +), (lateral +, vertical-), (lateral-, vertical-), "+" indicates that the load is positive, and "-" indicates that the load is negative.
5. The method of claim 4 for cross-point load measurement and verification of statically indeterminate mount engines, characterized by: in the fourth step, the pretreatment comprises: in test data, data of the strain bridges responding to the linear section with the loading ratio of 50% -100% are reserved, other data are eliminated, and the quantity of the data eliminated by each group of strain bridges is the same under each working condition.
6. The method of claim 5 for cross-point load measurement and verification of a statically indeterminate mount engine, characterized in that: dividing the test data of the single load calibration test into a regression data set and a verification data set according to the load size and direction of different load calibration working conditions, wherein the working conditions are divided into the regression working condition and the verification working condition which both cover the positive direction and the negative direction of the load component, the load size of the regression working condition covers typical values, and the number of the regression working conditions is more than that of the verification working conditions; then, the load and the bridge data corresponding to the regression working condition are used as regression data sets, and the load and the bridge data of the verification working condition are used as verification data sets.
7. The method of claim 6 for cross-point load measurement and verification of a statically indeterminate mount engine, characterized in that: in the sixth step, a strain-load equation set is constructed based on a regression data set, an equation set of the vertical/horizontal pull rod is constructed by adopting a traditional linear regression method, and an equation set of the inner/outer thrust pin is constructed according to the following method and steps:
step six A: calculating covariance correlation coefficients between the load vectors and each group of bridge strain response vectors in the regression data set, and eliminating strain bridges with covariance correlation coefficients smaller than r 1; r1 is in a value range of [0.3,0.5];
step six B: calculating covariance correlation coefficients between response data of any two groups of strain bridges in the residual strain bridges, screening out all strain bridge combinations with the covariance correlation coefficients smaller than r2 between any two groups, wherein the value range of r2 is [0.9,0.95];
step six C: in all the strain bridge combinations screened in the step six B, a strain-load equation of each bridge combination is constructed based on a stepwise linear regression method so as to fit goodness of fit (R) 2 ) Maximum criteria, determining the optimal equation in the strain-load equation with bn = 2-k sets of bridges, respectively, where k represents the number of bridges of the combination with the most bridges found in step six B.
8. The method of claim 7 for cross-point load measurement and verification of a statically indeterminate mount engine, characterized in that:
in the seventh step, the bridge data in the verification data set is substituted into the k-1 groups of strain-load equations established in the sixth step, load values are obtained through prediction and are compared with the loads in the verification data set, the relative errors of the load values and the loads in the verification data set are calculated, and the equation with the minimum predicted relative error is selected as the optimal strain load equation;
in the eighth step, the test data of the on-board load calibration test preprocessed in the fourth step are respectively substituted into the optimal strain-load equations of the inner/outer thrust pins and the vertical/horizontal pull rods, and the following intersection point loads (namely internal forces) acting on the engine dummy are solved: load component F of intersection point of outer thrust pin along X, Y and Z directions Outside x 、F Outside y 、F z outer Load component F at intersection point of inner thrust pin in Y and Z directions In y 、F In z Vertical load P of vertical tie rod z is perpendicular to Side load P of horizontal tie rod x level 。
9. The method for intersection load measurement and verification of a statically indeterminate mount engine as claimed in claim 1, wherein: in the ninth step, the concrete method and steps of respectively calculating resultant force and resultant moment by adopting intersection point load (internal force) and external load (external force) on the engine dummy piece are as follows:
step nine A: calculating course load resultant force Py, vertical load resultant force Pz and resultant moment Mz of an inner thrust pin hinge pivot of the engine dummy part caused by the internal force by adopting formulas (1) to (3);
Py＝ F outside y + F In y (1)
Pz＝ F z outer + F In z +P z is perpendicular to (2)
Mz＝P x level ×L 1 + F Outside y ×L 2 (3)
Wherein L is 1 Is the Y-direction distance, L, between the horizontal pull rod and the inner thrust pin 2 The distance between the load action point of the intersection point of the outer thrust pin and the hinge fulcrum of the inner thrust pin is in the X direction;
step nine B: calculating course load resultant force Py ' of the engine dummy part, vertical load resultant force Pz ' and resultant force Mz ' of a hinge pivot of the inner thrust pin, which are caused by external force, by adopting the steps (4) to (6);
Py＇＝ P y9015 (4)
Pz＇＝ P z9012 +P z9013 (5)
Mz＇＝ P x9011 ×L 3 + P z9014 ×L 4 + P y9015 ×L 5 (6)
L 3 the Y-direction distance, L, between the first side direction loading point and the inner side thrust pin 4 The Y-direction distance, L, between the second side loading point and the inner side thrust pin 5 The distance between the heading loading point and the inner side thrust pin in the X direction is obtained.
10. The method of claim 1 for cross-point load measurement and verification of a statically indeterminate mount engine, characterized in that: in the step ten, the following method and steps are adopted to compare whether the resultant force and the resultant moment obtained by calculating the intersection point load and the external load are balanced or not:
step ten A: respectively combining Py and Py ', pz and Pz ', mz and Mz ', fitting the linear relation by least square regression, and if the absolute value of the fitting slope is within 1 +/-0.03 and the fitting goodness (R) 2 ) If the average value is more than 0.995, the Py and Py ', the Pz and Pz', and the Mz and Mz 'have high coincidence, and the Py and Py', the Pz and the Pz ', the Mz and the Mz' are balanced, so that the optimal strain-load equation established through single load calibration test data can accurately predict the load of the thrust pin on the machine, and the optimal strain-load equation can be used for subsequent actual measurement of the load at the installation intersection point of the engine;
otherwise, the optimal strain-load equation is unavailable, in this case, an unbalanced term is found out, and step eleb is executed;
step ten B: and returning to the seventh step, removing the corresponding strain-load equation in the tenth step A aiming at the unbalanced item of the resultant force or the resultant moment in the tenth step A, selecting one group with the highest prediction precision in the residual equation set, and executing the eighth step, the ninth step and the tenth step A again.
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| CN116907788B (en) * | 2023-09-12 | 2024-01-19 | 中国空气动力研究与发展中心低速空气动力研究所 | Additional load measuring device and correction method for rotor wing test |
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