Helicopter high radial viscoelastic damper durability verification method
By applying axial and radial loads to a helicopter high radial viscoelastic damper, and combining finite element analysis and damage equivalence methods, the problem of accuracy in durability assessment was solved, and the effective assessment of the damper's life and safety assurance were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA HELICOPTER RES & DEV INST
- Filing Date
- 2024-07-25
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies make it difficult to accurately assess the durability of high radial viscoelastic dampers for helicopters, thus affecting their service life.
A durability verification method is provided, including test platform construction, test load determination, and test control technology. The method identifies fatigue-prone areas through finite element modeling and analysis, applies axial and radial loads, simplifies the spectrum using the damage equivalence method, simulates actual operating conditions, conducts fatigue tests, and performs periodic inspections.
It enables accurate assessment of the mean time to failure and safety inspection interval of viscoelastic dampers, ensuring helicopter safety, shortening the test cycle, and is applicable to lateral load fatigue testing of two-force bar structures.
Smart Images
Figure CN118961165B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of high radial viscoelastic dampers for helicopters, and specifically to a method for verifying the durability of high radial viscoelastic dampers for helicopters. Background Technology
[0002] Viscoelastic dampers are key elastic components in helicopter rotor systems. They are simple in structure, lightweight, highly reliable, long-lasting, and can be maintained as needed. Their main function is to provide sufficient damping for the tessellation of rotor blades, preventing ground resonance caused by the coupling between the rotor and the fuselage supported by the landing gear during takeoff and landing, and in-flight resonance caused by the coupling between the rotor and the fuselage. A cylindrical viscoelastic damper mainly consists of a cylindrical metal outer cylinder, an inner cylinder, and rubber in between. When the blades tessellate, the metal cylinder of the cylindrical viscoelastic damper undergoes relative axial movement, causing shear deformation of the rubber and generating damping.
[0003] High radial viscoelastic dampers bear both axial and high radial loads, which makes it difficult to assess their durability. The accuracy of durability test verification methods directly affects the service life of viscoelastic dampers. Summary of the Invention
[0004] Purpose of the invention
[0005] The purpose of this invention is to provide a method for verifying the durability of a high radial viscoelastic damper for helicopters, including test platform construction, test load determination, and test control technology. This invention proposes a novel test method, providing a method for compiling the test load spectrum for the durability test of a high radially stable viscoelastic damper elastomer, a test loading method, and a test operation process.
[0006] Technical solution
[0007] A method for verifying the durability of a helicopter high radial viscoelastic damper.
[0008] 1. Preparation of test specimens and supporting components, and patch installation;
[0009] 2. Fixture design and test piece boundary simulation;
[0010] Three: Application of characteristic loads;
[0011] 4. Pre-test inspection;
[0012] 5. Conduct fatigue tests and ensure periodic inspections during the test process;
[0013] Six: After the test is completed, check to determine the mean time to failure of the structural elastomer and the safety inspection interval.
[0014] The specific steps are as follows:
[0015] Step 1: The two ends of the high radial stability viscoelastic damper test piece are connected using dummy lugs to simulate the actual structure. The fatigue-prone areas of the inner and outer cylinder metal parts are determined by finite element modeling and analysis. Axial force is measured by attaching a patch to the inner metal cylinder and bending moment is measured by attaching a patch to the outer metal cylinder.
[0016] Step Two: The high radial stability viscoelastic damper test specimen is mounted on a fatigue testing machine, with single-ear dummy pieces designed at both ends to simulate the actual structural connection. Appropriate bending clamps should be installed in the test fixture, and an air-cooling device is required to maintain the ambient temperature of the test specimen during the test. Axial load is applied through the testing machine. Radial load is applied via a rope pulley system with weights; during the test, the radial load is applied as an environmental load, and the axial load as a dynamic load, applied simultaneously.
[0017] Step 3: Based on the load spectrum of the high radial stability viscoelastic damper during actual flight, simplify the spectrum by using the damage equivalence method.
[0018] Step 4: From the receipt of the test piece to the installation of the test piece, and throughout the entire durability test, it is necessary to prevent the elastomer part of the viscoelastic damper from being corroded by organic solutions. Before the test begins, the damper needs to be preheated by applying a load displacement of 1mm±2mm for 5 minutes and a static stiffness test is performed as the initial static stiffness.
[0019] Step 5: During the test, load or displacement monitoring should be performed to ensure that the test load meets the requirements; record the crack length and depth on the damper crack propagation record chart. After each loading program block is completed, the test specimen should undergo an online static stiffness test and a visual inspection.
[0020] Step Six: Visually inspect and tap the test pieces after the test and record the results.
[0021] Furthermore, in step one, the high radial stability viscoelastic damper test piece is composed of a metal inner cylinder, a metal outer cylinder, and a rubber layer.
[0022] Furthermore, in step two, the test fixture should be equipped with a bending clamp to ensure the coaxiality of the test fixture, the specimen, and the loading direction, and to avoid generating additional bending moments.
[0023] Furthermore, in step two, the test fixture should fully consider the material strength, ensuring easy loading and unloading and a large strength margin.
[0024] Furthermore, in step three, the damage equivalence principle is specifically as follows: the corresponding loads at each level in different states are equivalent to an equivalent load, and the damage caused by the equivalent load is equal to the damage caused by the loads at each level before equivalence.
[0025] Furthermore, in step three, the damage equivalence method is used to simplify the combined spectrum, specifically: the original load spectrum damage is equivalent to load spectrum block 1×M times + load spectrum block 1×N times, defined as a loading program block. This method allows for obtaining static and dynamic equivalent loads that are convenient for experimental loading, and also facilitates adjustment of the experimental load. This yields the mean failure time of the viscoelastic damper elastomer at room temperature.
[0026] Furthermore, in step three, to more realistically simulate the actual use of the damper, it is necessary to consider the ground operation and inspection conditions. Appropriate loads can be applied before the test to simulate these conditions. If the test piece does not fail after the ambient temperature test loading is completed, an accelerated test load can be obtained based on the damage equivalence principle. Once cracks appear in the test piece, high and low temperature tests can be conducted based on the load to determine the inspection interval for the test piece.
[0027] Furthermore, in the previous step, the test data are valid when the performance change of the viscoelastic damper in the room temperature test does not exceed 20%, and the test data are valid when the static stiffness in the high and low temperature test and the change at the end of the initial crack stage test do not exceed 15%.
[0028] Furthermore, in step five, if cracks or obvious damage appear on the test piece during the room temperature test, the test should be suspended, the test piece should be removed, and a comprehensive performance test should be conducted after the stiffness has stabilized.
[0029] When the static stiffness change of the test specimen exceeds 20% for the first time in online measurement, the test specimen should be removed, and a comprehensive performance test should be conducted after the stiffness stabilizes. Subsequently, the proportional relationship between the degree of stiffness change in online measurement and the degree of stiffness change in performance test should be derived. The decision to remove the test specimen for performance testing should be made with reference to the changes in online stiffness measurement and the proportional relationship between the changes in stiffness in performance test. After the room temperature test, the appearance inspection and performance data of the high radial stability viscoelastic damper should be recorded. Special attention should be paid to the initial signs of damage and the development trend of damage to the test specimen.
[0030] High and low temperature test phase: The test must be conducted in an environmental chamber, with at least two sets of tests, one set at a high temperature and the other set at a low temperature.
[0031] Furthermore, the high temperature, normal temperature, and low temperature mentioned are specifically determined according to the requirements for helicopter use.
[0032] The beneficial effects of this application are as follows:
[0033] (1) The viscoelastic damper elastomer durability test verification method provided by the present invention can verify the mean failure time and safety inspection interval of the damper through test, ensuring the safe use of the helicopter viscoelastic damper. Compared with the prior art, it has the advantage of being able to apply a constant lateral force simply and quickly.
[0034] (2) This invention provides a method for compiling the load spectrum, the test loading method, and the test operation process for the durability test of a high radially stable viscoelastic damper elastomer. This invention is also applicable to two-force bar structures and can be used to apply fatigue tests such as lateral loads. Attached Figure Description
[0035] Figure 1 This is a schematic diagram of a viscoelastic damper.
[0036] Figure 2 This is a schematic diagram of a viscoelastic damper under load;
[0037] Figure 3 This is a schematic diagram of a viscoelastic damper test bench. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar components or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this invention. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this invention, and should not be construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The embodiments of this invention will be described in detail below with reference to the accompanying drawings.
[0039] (1) This invention targets a high radial stability viscoelastic damper structure. Based on its loading characteristics, the mean failure time and safety inspection interval of the viscoelastic damper are obtained by applying environmental radial force and axial equivalent static and dynamic loads.
[0040] (2) Based on the principle of material damage equivalence, the present invention constructs an accelerated test load spectrum to obtain the initial crack, which can effectively shorten the test cycle.
[0041] (3) Based on the actual use of the viscoelastic damper, add large load conditions such as ground control to the test load and preheat the damper before the test.
[0042] In the attached diagram,
[0043] Figure 1 Viscoelastic dampers are mainly composed of a metal inner cylinder, an outer cylinder, and a rubber layer. The durability test mainly assesses the average failure time and inspection cycle of the rubber layer.
[0044] Figure 2 In addition to bearing the axial load F, the viscoelastic damper also needs to withstand constant radial loads (centrifugal forces) M1 and M2.
[0045] Figure 3 Constant radial loads M1 and M2 are achieved through ropes and weights.
[0046] Table 1 shows the load spectrum for durability tests at room temperature and high / low temperatures.
[0047] Table 2 shows the accelerated test load spectrum.
[0048] Table 1
[0049]
[0050] Table 2
[0051] As shown in Table 1, the damage equivalent of the original load spectrum is equivalent to load spectrum block 1×M times + load spectrum block 1×N times (defined as a loading program block). This method allows for obtaining static and dynamic equivalent loads that are convenient for experimental loading and also facilitates adjustment of the experimental load. This yields the mean failure time of the viscoelastic damper elastomer at room temperature. Simultaneously, to more realistically simulate the actual use of the damper, ground operation and inspection conditions need to be considered. Appropriate loads can be applied before the test to simulate this condition. If the test specimen is still not damaged after the room temperature test loading is completed, accelerated test loads can be obtained according to the damage equivalence principle, as shown in Table 2. After cracks appear in the test specimen, high and low temperature tests are continued according to the loads in Table 1 to obtain the inspection interval of the test specimen. Test data are valid when the performance change of the viscoelastic damper in the room temperature test does not exceed 20%, and test data are valid when the change in static stiffness in the high and low temperature tests compared to the end of the initial crack stage does not exceed 15%.
[0052] Example
[0053] Taking the fatigue test method of a high radial stability viscoelastic damper metal component as an example, the present invention will be further described in detail with reference to the accompanying drawings:
[0054] Step 1: Structural diagram as shown Figure 1 As shown. The two ends of the high radial stability viscoelastic damper test piece are connected using dummy lugs to simulate the actual structure. The fatigue-prone areas of the inner and outer cylinder metal parts are determined by finite element modeling and analysis. Axial force is measured by attaching a patch to the inner metal cylinder and bending moment is measured by attaching a patch to the outer metal cylinder.
[0055] Step Two: The high radial stability viscoelastic damper test specimen is mounted on a fatigue testing machine, with single-ear dummy pieces designed at both ends to simulate the actual structural connection. The test fixture should be equipped with appropriate bending clamps, and an air-cooling device is required during the test to maintain the ambient temperature of the test specimen. Axial load is applied through the testing machine. Radial load is applied via a rope pulley system with weights; during the test, the radial load is applied as an environmental load, and the axial load as a dynamic load, applied simultaneously. (Details follow...) Figure 2 As shown.
[0056] Step 3: Based on the load spectrum of the high radial stability viscoelastic damper during actual flight, simplify the spectrum by using the damage equivalence method.
[0057] Step 4: From the receipt of the test piece to the installation of the test piece, and throughout the entire durability test, it is necessary to prevent the elastomer part of the viscoelastic damper from being corroded by organic solutions. Before the test begins, the damper needs to be preheated by applying a load displacement of 1mm±2mm for 5 minutes and a static stiffness test is performed as the initial static stiffness.
[0058] Step 5: During the test, load or displacement monitoring should be performed to ensure that the test load meets the requirements; record the crack length and depth on the damper crack propagation record chart. After each loading program block is completed, the test specimen should undergo an online static stiffness test and a visual inspection. During the room temperature test, if cracks or obvious damage appear on the test specimen, the test should be suspended, the test specimen should be removed, and a comprehensive performance test should be conducted after the stiffness stabilizes.
[0059] When the static stiffness change of the test specimen exceeds 20% for the first time in online measurement, the test specimen should be removed, and a comprehensive performance test should be conducted after the stiffness stabilizes. Subsequently, the proportional relationship between the degree of stiffness change in online measurement and the degree of stiffness change in performance test should be derived. The decision to remove the test specimen for performance testing should be made with reference to the changes in online stiffness measurement and the proportional relationship between the changes in stiffness in performance test. After the room temperature test, the appearance inspection and performance data of the high radial stability viscoelastic damper should be recorded. Special attention should be paid to the initial signs of damage and the development trend of damage to the test specimen.
[0060] High and low temperature testing phase: The test must be conducted in an environmental chamber, with at least two sets of tests performed, one at a high temperature and the other at a low temperature. If the dummy component fails during the test, it must be replaced and the test continued.
[0061] Step Six: Visually inspect and tap the test pieces after the test and record the results.
[0062] In one embodiment of the present invention, in step one, the high radial stability viscoelastic damper test piece is composed of a metal inner cylinder, a metal outer cylinder and a rubber layer.
[0063] In one embodiment of the present invention, in step two, the test fixture should be equipped with a bending clamp to ensure the coaxiality of the test fixture, the specimen and the loading direction, and to avoid generating additional bending moments.
[0064] In one embodiment of the present invention, in step two, the test fixture should fully consider the material strength and ensure that it is easy to load and unload and has a large strength margin.
[0065] In one embodiment of the present invention, in step three, the damage equivalence principle is specifically as follows: the corresponding loads at each level in different states are equivalent to an equivalent load, and the damage caused by the equivalent load is equal to the damage caused by the loads at each level before equivalence.
[0066] In one embodiment of the present invention, step three, which simplifies the combined spectrum using the damage equivalence method, specifically involves: the original load spectrum damage is equivalent to load spectrum block 1×M times + load spectrum block 1×N times, defined as a loading program block. This method allows for obtaining static and dynamic equivalent loads that are convenient for experimental loading, and also facilitates adjustment of the experimental load. This yields the mean failure time of the viscoelastic damper elastomer at room temperature.
[0067] In one embodiment of the present invention, in step three, in order to more realistically simulate the actual use of the damper, it is necessary to consider the ground operation and inspection conditions. A corresponding load can be applied before the test to simulate these conditions. If the test piece is still not damaged after the ambient temperature test loading is completed, an accelerated test load can be obtained based on the damage equivalence principle. After cracks appear in the test piece, high and low temperature tests are then conducted based on the load to obtain the inspection interval for the test piece.
[0068] In one embodiment of the present invention, in the previous step, the test data are valid when the performance change of the viscoelastic damper in the room temperature test does not exceed 20%, and the test data are valid when the static stiffness in the high and low temperature test changes by no more than 15% compared with the end of the initial crack stage test.
[0069] In one embodiment of the present invention, the high temperature, normal temperature, and low temperature are specifically determined according to the requirements of helicopter use.
[0070] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Within the spirit and principles of the present invention, any person skilled in the art may use the disclosed technical content to make changes or modifications to create equivalent embodiments applicable to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention, any modifications, equivalent substitutions, improvements, etc., should be included within the protection scope of the present invention.
Claims
1. A method for verifying the durability of a helicopter high radial viscoelastic damper, characterized in that, 1. Preparation of test specimens and supporting components, and patch installation; 2. Fixture design and test piece boundary simulation; Three: Application of characteristic loads; 4. Pre-test inspection; 5. Conduct fatigue tests and ensure periodic inspections during the test process; Six: After the test is completed, conduct an inspection to determine the mean time to failure of the structural elastomer and the safety inspection interval; The specific steps are as follows: Step 1: The two ends of the high radial stability viscoelastic damper test piece are connected using lug dummy parts to simulate the actual structure. The fatigue risk points of the inner and outer cylinder metal parts are determined by finite element modeling and analysis. Axial force is measured by attaching a patch to the inner metal cylinder and bending moment is measured by attaching a patch to the outer metal cylinder. Step 2: The high radial stability viscoelastic damper test specimen is mounted on a fatigue testing machine, with single-ear dummy parts designed at both ends to simulate the actual structural connection; the test fixture is equipped with the corresponding bending fixture, and an air-cooling device is used to ensure the ambient temperature of the test specimen during the test; the axial load is applied through the testing machine; the radial load is applied through a rope pulley with a weight, and during the test, the radial load is applied as an environmental load and the axial load is applied as a dynamic load simultaneously; Step 3: Based on the load spectrum of the high radially stable viscoelastic damper during actual flight, simplify the spectrum by using the damage equivalence method; Step 4: From the receipt of the test piece to the installation of the test piece, and throughout the entire durability test, it is necessary to prevent the elastomer part of the high radial stability viscoelastic damper from being corroded by organic solutions. Before the test begins, a load displacement of 1mm±2mm needs to be applied to the high radial stability viscoelastic damper for 5 minutes for preheating, and a static stiffness test should be performed as the initial static stiffness. Step 5: During the test, load or displacement monitoring is performed to ensure that the test load meets the requirements; the crack length and depth are recorded on the crack propagation record chart of the high radial stability viscoelastic damper; after each loading program block is completed, the test piece is subjected to an online static stiffness test and a visual inspection is performed on the test piece. Step Six: Visually inspect and tap the test pieces after the test and record the results; In step three, the damage equivalence method is used to simplify the combined spectrum. Specifically, the damage equivalence of the original load spectrum is equivalent to load spectrum block 1×M times + load spectrum block 1×N times, which is defined as a loading program block. Static and dynamic equivalent loads that are easy to load in the test are obtained, and the mean failure time of the elastomer of the high radial stability viscoelastic damper at room temperature is obtained. Meanwhile, in order to more realistically simulate the actual use of the high radial stability viscoelastic damper, a corresponding load was applied before the test to simulate the ground operation and testing conditions. If the test piece is still not damaged after the room temperature test loading is completed, the accelerated test load is obtained according to the damage equivalence principle. After the test piece develops cracks, high and low temperature tests are carried out according to the load to obtain the safety inspection interval of the test piece. In step five, if cracks or obvious damage appear on the test piece during the room temperature test, the test is suspended, the test piece is removed, and a comprehensive performance test is carried out after the stiffness stabilizes. When the static stiffness of the test piece changes by more than 20% for the first time during online measurement, the test piece is removed and a comprehensive performance test is conducted after the stiffness stabilizes. Subsequently, a proportional relationship is derived between the degree of stiffness change in online measurement and the degree of stiffness change in performance test. The decision to remove the test piece for performance testing is made based on this proportional relationship. After the room temperature test, the visual inspection of the high radial stability viscoelastic damper and the load or displacement data are recorded, paying attention to the initial signs of damage and the trend of damage development. High and low temperature test stage: The test must be conducted in an environmental chamber, with at least two sets of tests, one at a high temperature and the other at a low temperature.
2. The method as described in claim 1, characterized in that, In step one, the high radial stability viscoelastic damper test piece consists of a metal inner cylinder, a metal outer cylinder, and a rubber layer.
3. The method as described in claim 2, characterized in that, In step two, the test fixture is fitted with a bending fixture to ensure the coaxiality of the test fixture, the specimen, and the loading direction, thus avoiding the generation of additional bending moments.
4. The method as described in claim 3, characterized in that, In step three, the damage equivalence principle is specifically as follows: the corresponding loads at each level in different states are equivalent to an equivalent load, and the damage caused by the equivalent load is equal to the damage caused by the loads at each level before equivalence.