CN111977020B - Method for testing static friction force of landing gear shock absorption strut - Google Patents
Method for testing static friction force of landing gear shock absorption strut Download PDFInfo
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- CN111977020B CN111977020B CN202010643491.7A CN202010643491A CN111977020B CN 111977020 B CN111977020 B CN 111977020B CN 202010643491 A CN202010643491 A CN 202010643491A CN 111977020 B CN111977020 B CN 111977020B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
- B64F5/60—Testing or inspecting aircraft components or systems
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Abstract
A method for testing the static friction force of a shock-absorbing strut of an undercarriage is characterized in that the existing test equipment of a landing gear shock-absorbing strut press is utilized, the load application mode of the shock-absorbing strut of the undercarriage is improved, the load is applied in a mode closer to the actual load frequently borne by the undercarriage, the design parameter compression ratio K of the undercarriage and the friction force parameter Pt of the shock-absorbing strut are calculated according to the compression test data obtained by the test of the shock-absorbing strut press, and the performance and the static friction force characteristic of the shock-absorbing strut of the undercarriage of an airplane are compared and judged accordingly.
Description
Technical Field
The invention relates to the field of design and manufacture of a shock absorption strut of an aircraft landing gear, in particular to a static friction force testing method of the shock absorption strut of the aircraft landing gear.
Background
Most modern aircraft landing gear strut dampers use the most widely used, relatively efficient form of oil-to-gas damper design. The design principle is equivalent to an energy conversion and dissipation system consisting of a liquid damper and an air spring, and relative motion kinetic energy between the airplane body and the ground is converted into compressed gas internal energy, tire elastomer internal energy and friction heat energy through tire transmission, so that the shock absorption target of the airplane body is realized, the design load is reduced, and the comfort is improved.
The shock strut structural design has particularity. Under the action of load, the outer cylinder and the strut (i.e. the inner cylinder) of the shock absorption strut can move relatively, and the outer cylinder and the strut are contacted with each other to form a bearing pair, so that friction force exists; because of the existence of high-pressure gas and oil, specially designed sealing devices are needed, and the sealing devices inevitably cause the damping strut structure to have the friction force characteristic which is changed along with the load of the strut; the elastic deformation of the shock strut structure affects the characteristics of the bearing pair contact and sealing device, and can also cause changes in the frictional force characteristics.
The particularities of the shock strut fabrication process. The shock-absorbing strut is made of rich materials (various metals, hydraulic oil, leather, special sealing materials, nitrogen and the like), complex in part shape and process, high in machining precision, high in requirements on installation and inspection equipment, and multiple in process files and technical conditions, and the friction force characteristics of the shock-absorbing strut are directly influenced by the factors.
After the assembly of the landing gear shock strut is completed, a compression test needs to be carried out on a press machine, compression and extension travel curves of the shock strut are drawn, the data relation of the curves meets corresponding technical conditions, and whether the design and the manufacture of the landing gear shock strut of the airplane meet the standards or not is judged according to the data relation.
Disclosure of Invention
The application aims to provide a static friction force testing method for a shock strut of an undercarriage according to the actual load of the shock strut of the undercarriage of the airplane and the problems in the prior art.
The utility model provides an undercarriage shock strut static friction force test method, known this undercarriage shock strut's design parameter, undercarriage shock strut's upper end is equipped with first nodical, and undercarriage shock strut's lower extreme is equipped with the second nodical, and undercarriage shock strut can take place the compression under the effect of external load, and its characterized in that contains following content: 1) fixing the first intersection point, and gradually applying a load on the second intersection point, wherein the included angle between the load and the axis of the landing gear shock strut is alpha; 2) gradually increasing the load to gradually increase the compression amount of the landing gear shock strut and form a first relation curve of the compression amount of the landing gear shock strut and the load; 3) when the compression amount of the landing gear shock strut reaches a preset value, the applied load is gradually reduced, so that the compression amount of the landing gear shock strut is gradually recovered, and a second relation curve of the compression amount of the landing gear shock strut and the load is formed; 4) recording the initial load value of the first curve as P1 and the maximum load value as P2, and recording the initial load value of the second curve as P3 and the minimum load value as P4; 5) when the compression amount of the landing gear shock strut is the same, recording the load value corresponding to the first curve as PA and the load value corresponding to the second curve as PB; 5) calculating the compression ratio K of the landing gear shock strut according to the following equations (P2+ P3)/(P1+ P4); 6) calculating a friction parameter Pt of the landing gear shock strut according to the following formula, wherein Pt is (PA-PB)/2/PB/cos alpha; 7) and comparing the compression ratio K and the friction force parameter Pt with the design parameters of the landing gear damping support.
The load applied at the second intersection point comprises a load parallel to the axis of the landing gear shock strut and an aircraft reverse heading load.
The load applied at the second intersection point comprises a load parallel to the axis of the landing gear shock strut and a side load of the landing gear shock strut.
The beneficial effect of this application lies in: 1) the friction force characteristic of the damping strut is mainly characterized by friction force parameters, in short, the friction force parameters are large, the damping strut is poor in motion function and serious in abrasion, high in failure probability, poor in reliability and poor in performance, and the invention provides a test load loading mode and a friction force parameter calculation method of the damping strut, so that the reliability level of a damping strut product can be tested and controlled with low cost. 2) Usually, only the compression ratio K is compared with the design parameters of the landing gear damping support, a friction force parameter Pt is added for comparison with the design parameters of the landing gear damping support, the load loading mode is more practical, and the problem of parameter loss of static friction force of the landing gear damping support is solved.
The present application is described in further detail below with reference to the following example figures:
drawings
FIG. 1 is a schematic view of an aircraft landing leg loaded on a press for testing.
FIG. 2 is a graph showing the compression versus load curve obtained from the press loading test.
The numbering in the figures illustrates: 1 shock strut, 2 first intersection point, 3 second intersection point, 4 landing gear shock strut axis, 5 first curve, 6 second curve.
Detailed Description
Referring to the attached drawings, the static friction force testing method of the landing gear shock strut of the application has the advantages that the design parameters of the landing gear shock strut 1 are known, the upper end of the landing gear shock strut 1 is provided with a first intersection point 2, the intersection point is used for being in cross-linking with an airplane body, during testing, the first intersection point is fixed, the lower end of the landing gear shock strut 1 is provided with a second intersection point 3, the intersection point is in cross-linking with the landing gear, during testing, a load is applied to the second intersection point 3 through a press machine to simulate the actual load transferred to the second intersection point 3 by the landing gear during airplane landing, and the landing gear shock strut 1 can be axially compressed under the action of an external load.
The static friction force test process of the landing gear shock strut is as follows:
loading is carried out on a press machine by using a proper loading supporting tool according to figure 1, a first intersection point 2 at the upper end of the shock strut 1 is fixed, a second intersection point 3 at the lower end of the shock strut 1 applies a load P through the press machine, and the direction of the load P forms an included angle alpha with the axis 4 of the shock strut. The plane of the included angle α takes into account the 2 directions of the longitudinal and transverse planes, the values of which are determined by the landing gear design requirements of a particular aircraft, and the load is increased step by step to increase the compression of the landing gear shock strut step by step, forming a first relationship curve 5 of the compression of the landing gear shock strut to the load, as shown in fig. 2.
When the amount of compression of the landing gear shock strut 1 reaches a predetermined value, the applied load P is then reduced progressively, causing the amount of compression of the landing gear shock strut to progressively recover, forming a second relationship curve 6 of the amount of compression of the landing gear shock strut to the load, as shown in figure 2.
According to a graph of a relation curve of compression amount and load obtained by a loading test on a press, a load initial value of a first curve 5 is recorded as P1, a load maximum value is recorded as P2, a load initial value of a second curve 6 is recorded as P3, and a load minimum value is recorded as P4, and a compression ratio K of a landing gear shock strut is calculated according to a formula K ═ P2+ P3)/(P1+ P4.
And when the same compression amount of the landing gear shock strut in the first curve 5 and the second curve 6 is selected arbitrarily, recording the corresponding load value of the compression amount in the first curve 5 as PA, and the corresponding load value in the second curve 6 as PB, and calculating the friction force parameter Pt of the landing gear shock strut according to the formula Pt ═ PA/2/PB/cos alpha.
And finally, comparing the compression ratio K and the friction force parameter Pt with the design parameters of the landing gear damping support. Usually, only the compression ratio K is compared with the design parameters of the landing gear damping strut, a friction force parameter Pt is added in the method and compared with the design parameters of the landing gear damping strut, the load loading mode is more practical, and the problem of parameter loss of static friction force of the landing gear damping strut is solved.
In the implementation, according to the method, the damping pillars of the left main undercarriage, the right main undercarriage and the nose undercarriage of an airplane are respectively detected, the included angle between the load P direction and the axis of the damping pillar is taken as the alpha included angle and is 0 degree, and the test is carried out according to the technical scheme of the application. The calculated friction parameter Pt is shown in table 1.
As can be seen from table 1, the front start Pt is better than the main start, and the main start large compression case is better than the small compression case, which have been verified by actual airplanes.
Claims (3)
1. The utility model provides an undercarriage shock strut static friction force test method, known this undercarriage shock strut's design parameter, undercarriage shock strut's upper end is equipped with first nodical, and undercarriage shock strut's lower extreme is equipped with the second nodical, and undercarriage shock strut can take place the compression under the effect of external load, and its characterized in that contains following content: 1) fixing the first intersection point, and gradually applying a load on the second intersection point, wherein the included angle between the load and the axis of the landing gear shock strut is alpha; 2) gradually increasing the load to gradually increase the compression amount of the landing gear shock strut and form a first relation curve of the compression amount of the landing gear shock strut and the load; 3) when the compression amount of the landing gear shock strut reaches a preset value, the applied load is gradually reduced, so that the compression amount of the landing gear shock strut is gradually recovered, and a second relation curve of the compression amount of the landing gear shock strut and the load is formed; 4) recording the initial load value of the first curve as P1 and the maximum load value as P2, and recording the initial load value of the second curve as P3 and the minimum load value as P4; 5) when the compression amount of the landing gear shock strut is the same, recording the load value corresponding to the first curve as PA and the load value corresponding to the second curve as PB; 5) calculating the compression ratio K of the landing gear shock strut according to the following formula (P2+ P3)/(P1+ P4); 6) calculating a friction parameter Pt of the landing gear shock strut according to the following formula, wherein Pt is (PA-PB)/2/PB/cos alpha; 7) and comparing the compression ratio K and the friction force parameter Pt with the design parameters of the landing gear damping support.
2. The landing gear shock strut static friction test method according to claim 1, wherein the load applied at the second intersection point comprises a load parallel to the landing gear shock strut axis and an aircraft reverse heading load.
3. The landing gear shock strut static friction test method of claim 1, wherein said applying a load at the second intersection point comprises a load parallel to the landing gear shock strut axis and a side load of the landing gear shock strut.
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| CN202010643491.7A CN111977020B (en) | 2020-07-06 | 2020-07-06 | Method for testing static friction force of landing gear shock absorption strut |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102010029023A1 (en) * | 2010-05-17 | 2011-11-17 | Müller-Werkzeug GmbH & Co. KG Kfz.-Spezialwerkzeuge | Wheel suspension backlash device for landing gear of motor vehicle, has force application portion provided between wheel and contact surface of wheel, where high static friction exists between portion and wheel |
| EP3326730A1 (en) * | 2016-11-29 | 2018-05-30 | The Boeing Company | Tooling with permanent low friction coating for setting interference-fit fasteners |
| CN108388733A (en) * | 2018-02-27 | 2018-08-10 | 清华大学 | Four-wheel layout undercarriage modeling method based on frictional ground force and device |
| CN208833463U (en) * | 2018-09-17 | 2019-05-07 | 中航飞机起落架有限责任公司 | Drop-test lateral sliding test mechanism and drop test device |
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2020
- 2020-07-06 CN CN202010643491.7A patent/CN111977020B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102010029023A1 (en) * | 2010-05-17 | 2011-11-17 | Müller-Werkzeug GmbH & Co. KG Kfz.-Spezialwerkzeuge | Wheel suspension backlash device for landing gear of motor vehicle, has force application portion provided between wheel and contact surface of wheel, where high static friction exists between portion and wheel |
| EP3326730A1 (en) * | 2016-11-29 | 2018-05-30 | The Boeing Company | Tooling with permanent low friction coating for setting interference-fit fasteners |
| CN108388733A (en) * | 2018-02-27 | 2018-08-10 | 清华大学 | Four-wheel layout undercarriage modeling method based on frictional ground force and device |
| CN208833463U (en) * | 2018-09-17 | 2019-05-07 | 中航飞机起落架有限责任公司 | Drop-test lateral sliding test mechanism and drop test device |
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