Helicopter transmission system shaft sleeve simulation piece design and fatigue test method

Abstract

The invention provides a helicopter transmission system shaft sleeve simulation piece design and fatigue test method, and relates to material fatigue performance testing, and the method comprises the steps: designing a helicopter transmission system shaft sleeve simulation piece based on finite element calculation in combination with actual conditions, and carrying out a fatigue test. When the shaft sleeve simulation part of the helicopter transmission system is used for analysis and testing, multiple iterations can be carried out in a laboratory environment, expensive physical prototype construction and testing are avoided, and the research and development cost is remarkably reduced. And meanwhile, more normative test standards and design specifications can be established, and the development of the whole industry in the aspect of technical standardization is promoted.

Description

Technical Field

[0001] The invention relates to the field of material fatigue performance testing, and in particular to a helicopter transmission system shaft sleeve simulation component design and a fatigue test method. Background Art

[0002] In the design and manufacturing process of helicopters, the transmission system is the core part of power transmission, and its reliability and performance are directly related to flight safety and mission execution efficiency. The transmission system consists of key components such as the engine, the main reducer and multiple transmission shafts, which are faced with instantaneous large loads and complex operating conditions during flight. Therefore, the demand for the design and analysis of the transmission system is increasing. With the development of new materials and manufacturing processes, the design of bushings and other components in helicopter transmission systems can be more lightweight to improve overall performance. This involves material properties in many aspects such as strength, toughness and environmental adaptability. The application of modern composite materials and high-strength alloys gives designers more options to meet engineering requirements.

[0003] Transmission system components, especially bushings, often experience repeated loads, leading to fatigue failure. Therefore, it is crucial to conduct fatigue tests to provide reliable life prediction data for the design. The fatigue performance evaluation of bushings not only needs to consider the performance of the material itself, but also needs to conduct a comprehensive analysis based on factors such as working conditions and loading methods. In order to ensure the safety of helicopters in various complex environments, it is particularly important to study the reliability of bushings. This not only includes the reasonable selection of materials and processing technology, but also the ability to cope with extreme conditions must be considered during the design process, so that the helicopter can still perform reliably when performing difficult or emergency tasks.

[0004] In terms of fatigue testing, the design of simulation parts for the transmission system is crucial. It not only needs to accurately reflect the actual working conditions, especially the dynamic load changes under various flight modes, but also needs to evaluate its reliability in long-term use through systematic fatigue testing. Therefore, an efficient bushing simulation part design and fatigue test method is urgently needed to provide strong support for the optimization of the transmission system. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a helicopter transmission system shaft sleeve simulation component design and fatigue test method, which not only helps to improve the safety and reliability of the helicopter, but also helps to promote the further development of aviation technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A helicopter transmission system shaft sleeve simulation component design and fatigue test method comprises the following steps: The first step is to design the geometric configuration of the bushing simulation part by combining the design purpose with finite element analysis; The second step is to reduce the axial force and torque in different proportions through finite element analysis to restore the stress distribution of the structural parts and the contribution of the axial force and torque to the stress distribution, obtain the stress analysis of the structure, and determine the load; Step 3: According to the stress analysis of the structure, determine the dangerous position of the structure and set the scratch defect in combination with the direction of the maximum principal stress; The fourth step is to perform fatigue tests on the bushing simulation parts containing standard scratches to obtain fatigue life results for correcting the fatigue life prediction model of the simulation parts containing standard scratches.

[0007] Furthermore, the second step includes: applying a fixed constraint at one end of the simulation component, applying concentrated force and torque at the central axis of the other end, and taking into account that the size of the simulation component varies greatly compared with the size of the original structure, reducing the axial force and torque in different proportions to restore the stress distribution of the structural component and the contribution of the axial force and torque to the stress distribution.

[0008] Further, the setting of the scratch defect in the third step includes: Select the root of the fillet to prefabricate defects, and prefabricate four scratch defects at four symmetrical positions of the root of the fillet.

[0009] Further, the fourth step includes designing a fatigue test fixture, including: When the sleeve simulation is subjected to fatigue test, the clamping device smoothly transmits the cyclic force to the specimen along the longitudinal axis; the clamping device maintains the coaxiality requirement. Before each series of tests and at any time when the loading chain changes, the centering of the testing machine should be checked. The coaxiality of the testing machine should not exceed 5%; the clamping device ensures the reproducibility of the specimen installation, and the coaxiality of the specimen is ensured by the surface, and the tensile and compressive forces can be smoothly transmitted during the test; the specimen is positioned between the upper and lower clamps to ensure axial force, and a predetermined stress mode is applied at the same time to ensure that the force is evenly distributed on the cross section of the specimen; The fixture consists of a disc part with bolt holes and an axial connecting part; the outer diameter of the disc part is 48 mm, and there are 8 bolt holes with a diameter of 5 mm evenly distributed on the circumference, the inner diameter is 27 mm, and there is a through hole for installation or fixing, and the center of the bolt hole is 19 mm away from the center of the disc; the length of the shaft of the axial connecting part is 45 mm, and there is an arc transition at the connection of the shaft with a radius of 5 mm; during use, the disc part is fixed with bolts, and the axial connecting part is used to clamp the specimen or transfer the load.

[0010] Furthermore, the fourth step includes pasting the fatigue test strain gauge, including: The strain gauge is used to measure the strain generated by the material or structure under the action of external force, and is composed of one or more conductive materials and attached to the surface of the object to be measured; a strain rosette is composed of three or more strain gauges, which are arranged near the same point at a specific angle and are used to measure multi-directional strain on a two-dimensional plane, thereby helping to determine the strain distribution of the material or structure under a complex stress state; a strain rosette is pasted on each side of the longitudinal symmetric surface of the opening of the simulation part, the transition section and the middle position of the opening; a strain rosette is pasted symmetrically on the strain rosette on the lower surface and the upper surface of the test piece; the strain gauge data acquisition system is turned on to determine that all strain gauges are in good working condition.

[0011] Furthermore, the fatigue test in the fourth step includes: 1) Carry out formal fatigue test according to the loading conditions, test machine settings, environmental conditions and test time estimation determined in the preliminary test; 2) During the test, observe the status of the test piece. If any abnormality is found, stop the machine immediately for processing; 3) For the first test piece of each group, stop the machine every 10,000 cycles to observe the defect position of the test piece and check whether visible cracks occur; when visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test piece; if the test piece has not yet broken, continue the test until obvious visible cracks occur or it breaks completely, record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece; 4) For the other test pieces in each group, after reaching 50% of the life of the first piece, start stopping the machine for inspection every 10,000 times. When visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test pieces. If the test piece has not yet broken, continue the test until obvious visible cracks or complete fractures occur. Record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece. 5) After the test piece breaks, remove it and store it in a designated location; 6) Based on the test results, analyze whether to continue with the next test under this load condition.

[0012] Beneficial effects: (1) The present invention designs a small test piece that can simulate the key geometric features of the original structure, which is convenient for fatigue test analysis; proposes a scheme for prefabricating scratch defects on the simulated structural parts; and designs a fixture for the simulated part test.

[0013] (2) Simulation parts can test the performance of different materials under specific load and environmental conditions, helping designers select materials with the best performance to improve the durability and lightweight of the bushing; (3) Using simulation parts for analysis and testing allows multiple iterations to be performed in a laboratory environment, avoiding expensive physical prototype construction and testing, significantly reducing R&D costs; (4) By conducting fatigue tests on simulated parts, the performance of the bushing in long-term use can be more accurately evaluated, thereby predicting its service life and maintenance cycle, thereby ensuring flight safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A flowchart of a helicopter transmission system shaft sleeve simulation component design and fatigue test method of the present invention; Figure 2 It is the geometric configuration diagram of the simulation part; Figure 3 It is the maximum principal stress distribution cloud diagram of the shaft sleeve simulation part; Figure 4 It is the minimum principal stress distribution cloud diagram of the bushing simulation part; Figure 5 Schematic diagram of the location of the prefabricated scratch defect; Figure 6 This is a schematic diagram of the test fixture (two sets) for the bushing simulation part; Figure 7 Schematic diagram of the strain gauge installation position (four three-axis strain gauge rosettes in total). DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention is further described in detail below in conjunction with the accompanying drawings.

[0016] like Figure 1 As shown, a helicopter transmission system shaft sleeve simulation component design and fatigue test method of the present invention comprises the following steps: The first step is to design the geometric configuration of the bushing simulation part by combining the design purpose with finite element analysis; The second step is to reduce the axial force and torque in different proportions through finite element analysis to restore the stress distribution of the structural parts and the contribution of the axial force and torque to the stress distribution, obtain the stress analysis of the structure, and determine the load; Step 3: According to the stress analysis of the structure, determine the dangerous position of the structure and set the scratch defect in combination with the direction of the maximum principal stress; The fourth step is to perform fatigue tests on the bushing simulation parts containing standard scratches to obtain fatigue life results for correcting the fatigue life prediction model of the simulation parts containing standard scratches.

[0017] Furthermore, the helicopter transmission system shaft sleeve is usually a cylindrical structural part, which is sleeved on the outside of the power shaft to provide support and positioning functions, and can withstand radial and axial loads. It is generally a symmetrical structure consisting of a front shaft sleeve assembly, a universal joint ring, and a rear shaft sleeve assembly, and the shaft sleeve assembly is a cylindrical structure.

[0018] In order to perform calculation and analysis, it is necessary to give the type of sleeve material and its mechanical properties. Table 1 shows the mechanical properties of a reference material.

[0019] Table 1 Sleeve materials and their mechanical parameters

[0020]

[0021] Table 2 gives an example of the loading condition of a sleeve structure, where one end of the sleeve is fixed and the other end is subjected to axial tension and torque. The steady-state value and alternating value of the alternating load are given in Table 2.

[0022] Table 2 Fatigue load values

[0023]

[0024] Furthermore, the purpose of designing the simulation mentioned in the first step is to test whether the damage evolution equation applicable to the standard specimen is still applicable to the structural parts with more complex stress states. Therefore, the most important thing in designing the simulation is to simulate the stress state of the structural parts. The main body of the sleeve is a slotted thin-walled cylinder, and in order to reduce stress concentration, fillets are added at the edge size mutation and the slot edge. These structural features determine the stress distribution of the sleeve structure; at the same time, for the purpose of saving materials, the size of the simulation can be appropriately reduced without changing the structural features.

[0025] Combining the above factors and analyzing the stress distribution of different size configurations through finite element analysis, a schematic diagram of a certain sleeve simulation is given, such as Figure 2 shown.

[0026] Furthermore, the loads mentioned in the second step include: applying a fixed constraint at one end of the simulation part, and applying concentrated force and torque at the central axis of the other end. Considering that the size of the simulation part is greatly different from the original structure size, the axial force and torque need to be reduced in different proportions to restore the stress distribution of the structural part and the contribution of the axial force and torque to the stress distribution. After calculation, the axial force is multiplied by the reduction factor 0.31, and the torque is multiplied by the reduction factor 0.31. The maximum principal stress distribution cloud diagram of the sleeve simulation part is shown in the figure below: Figure 3 As shown in the figure, it can be seen that stress concentration occurs at the slotted corner due to dimensional changes, and the maximum stress is located on the inner side of the cylinder. Figure 3 , Figure 4As shown in the figure, the location and magnitude of the maximum principal stress and minimum principal stress of the simulated component are basically consistent with those of the original structure.

[0027] Furthermore, the scratch defect setting in the third step includes: According to the stress analysis of the structure, the fillet of the structure is the most dangerous position with the highest stress. However, since the stress state of the structure is a complex stress state, the direction of the maximum principal stress needs to be considered when designing the defect prefabrication. According to the results of the finite element stress analysis, the stress gradient at the fillet of the slot is not large, so the root of the fillet is selected to prefabricate the defect. Figure 5 That is, four scratch defects are prefabricated at four symmetrical positions at the root of the fillet, and a fillet with a radius of 0.2mm is made on the inner side of the opening.

[0028] Furthermore, the fourth step includes designing a fatigue test fixture, including: When the shaft sleeve simulation is subjected to fatigue test, a special fixture needs to be designed to connect the test piece and the chuck of the testing machine. According to the structural form of the shaft sleeve simulation and the characteristics of the chuck of the testing machine, the designed fixture is as follows: Figure 6 As shown. The fixture consists of two parts: a disc part with bolt holes and a shaft-shaped connection part. The outer diameter of the disc part is 48 mm, with 8 bolt holes with a diameter of 5 mm evenly distributed on the circumference, an inner diameter of 27 mm, and a through hole for installation or fixing. The center of the bolt hole is 19 mm away from the center of the disc. The length of the shaft of the shaft-shaped connection part is 45 mm, and there is an arc transition at the connection of the shaft with a radius of 5 mm. During use, it is mainly fixed by bolting through the disc part, while the shaft-shaped connection part is used to clamp the specimen or transfer the load.

[0029] Further, the fourth step includes pasting the fatigue test strain gauge, including: Strain gauges are used to measure the strain (deformation) of materials or structures under the action of external forces. It is a sensor used for strain measurement, usually composed of one or more conductive materials (such as metals or semiconductors) attached to the surface of the object being measured. Strain rosettes consist of three or more strain gauges, usually arranged near the same point at specific angles (such as 0°, 45°, 90°). The main function of strain rosettes is to measure multi-directional strain on a two-dimensional plane, thereby helping to determine the strain distribution of materials or structures under complex stress states. A strain rosette is pasted on each side of the longitudinal symmetric surface of the opening of the simulation part, the transition section and the middle position of the opening. A strain rosette is pasted symmetrically on the lower surface of the specimen with the strain rosette on the upper surface, such as Figure 7 Turn on the strain gauge data acquisition system and make sure all strain gauges are working well.

[0030] Furthermore, the fatigue test method in the fourth step includes: 1) Carry out formal fatigue test according to the loading conditions, test machine settings, environmental conditions and test time estimation parameters determined in the preliminary test; 2) During the test, observe the status of the test piece. If any abnormality is found, stop the machine immediately for processing; 3) For the first test piece of each group, stop the machine every 10,000 cycles to observe the defect position of the test piece and check whether visible cracks occur. When visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test piece. If the test piece has not yet broken, continue the test until obvious visible cracks occur or it breaks completely, record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece; 4) For the other test pieces in each group, after reaching 50% of the life of the first piece, start stopping the machine for inspection every 10,000 times. When visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test piece. If the test piece has not yet broken, continue the test until obvious visible cracks or complete fractures occur. Record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece. 5) After the test piece breaks, remove it and store it in a designated location; 6) Based on the test results, analyze whether to continue with the next test under this load condition.

[0031] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A helicopter transmission system shaft sleeve simulation component design and fatigue test method, characterized in that: The steps include: The first step is to design the geometric configuration of the bushing simulation part by combining the design purpose with finite element analysis; The second step is to reduce the axial force and torque in different proportions through finite element analysis to restore the stress distribution of the structural parts and the contribution of the axial force and torque to the stress distribution, obtain the stress analysis of the structure, and determine the load; Step 3: According to the stress analysis of the structure, determine the dangerous position of the structure and set the scratch defect in combination with the direction of the maximum principal stress; The fourth step is to perform fatigue tests on the bushing simulation parts containing standard scratches to obtain fatigue life results for correcting the fatigue life prediction model of the bushing simulation parts containing standard scratches.

2. A helicopter transmission system shaft sleeve simulation component design and fatigue test method according to claim 1, characterized in that: The second step includes: applying a fixed constraint at one end of the simulation component and applying concentrated force and torque at the central axis of the other end. Considering that the size of the simulation component varies greatly compared with the original structure size, the axial force and torque are reduced in different proportions to restore the stress distribution of the structural component and the contribution of the axial force and torque to the stress distribution.

3. A helicopter transmission system shaft sleeve simulation component design and fatigue test method according to claim 1, characterized in that: The scratch defect setting in the third step includes: Select the root position of the fillet to prefabricate defects, and prefabricate four scratch defects at four symmetrical positions of the root position of the fillet.

4. A helicopter transmission system shaft sleeve simulation component design and fatigue test method according to claim 1, characterized in that: The fourth step includes designing a fatigue test fixture, including: When the sleeve simulation is subjected to fatigue test, the clamping device smoothly transmits the cyclic force to the specimen along the longitudinal axis; the clamping device maintains the coaxiality requirement. Before each series of tests and at any time when the loading chain changes, the centering of the testing machine should be checked. The coaxiality of the testing machine should not exceed 5%; the clamping device ensures the reproducibility of the specimen installation, and the coaxiality of the specimen is ensured by the surface, and the tensile and compressive forces can be smoothly transmitted during the test; the specimen is positioned between the upper and lower clamps to ensure axial force, and a predetermined stress mode is applied at the same time to ensure that the force is evenly distributed on the cross section of the specimen; The fixture consists of a disc part with bolt holes and an axial connecting part; the outer diameter of the disc part is 48 mm, and there are 8 bolt holes with a diameter of 5 mm evenly distributed on the circumference, the inner diameter is 27 mm, and there is a through hole for installation or fixing, and the center of the bolt hole is 19 mm away from the center of the disc; the length of the shaft of the axial connecting part is 45 mm, and there is an arc transition at the connection of the shaft with a radius of 5 mm; during use, the disc part is fixed with bolts, and the axial connecting part is used to clamp the specimen or transfer the load.

5. A helicopter transmission system shaft sleeve simulation component design and fatigue test method according to claim 1, characterized in that: The fourth step includes pasting the fatigue test strain gauge, including: The strain gauge is used to measure the strain generated by the material or structure under the action of external force, and is composed of one or more conductive materials and attached to the surface of the object to be measured; a strain rosette is composed of three or more strain gauges, which are arranged near the same point at a specific angle and are used to measure multi-directional strain on a two-dimensional plane, thereby helping to determine the strain distribution of the material or structure under a complex stress state; a strain rosette is pasted on each side of the longitudinal symmetric surface of the opening of the simulation part, the transition section and the middle position of the opening; a strain rosette is pasted symmetrically on the strain rosette on the lower surface and the upper surface of the test piece; the strain gauge data acquisition system is turned on to determine that all strain gauges are in good working condition.

6. A helicopter transmission system shaft sleeve simulation component design and fatigue test method according to claim 1, characterized in that: The fatigue test in the fourth step includes: 1) Carry out formal fatigue test according to the loading conditions, test machine settings, environmental conditions and test time estimation determined in the preliminary test; 2) During the test, observe the status of the test piece. If any abnormality is found, stop the machine immediately for processing; 3) For the first test piece of each group, stop the machine every 10,000 cycles to observe the defect position of the test piece and check whether visible cracks occur; when visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test piece; if the test piece has not yet broken, continue the test until obvious visible cracks occur or it breaks completely, record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece; 4) For the other test pieces in each group, after reaching 50% of the life of the first piece, start stopping the machine for inspection every 10,000 times. When visible cracks or fractures occur, record the number of test cycles and take photos of the defective parts of the test pieces. If the test piece has not yet broken, continue the test until obvious visible cracks or complete fractures occur. Record the number of cycles at this time, terminate the test, and take photos of the defective parts of the test piece. 5) After the test piece breaks, remove it and store it in a designated location; 6) Based on the test results, analyze whether to continue with the next test under this load condition.

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