A load monitoring method for a flexible beam bending fatigue test of an unmanned helicopter

Abstract

The application discloses a flexible beam bending fatigue test load monitoring method of unmanned helicopter, which comprises the following steps: pasting strain gauges on a test piece and a test piece fixing joint, checking the effectiveness of the strain gauges; calibrating all specified sections of the test piece and the test piece fixing joint; performing load debugging before the test to obtain load values of monitoring sections meeting test task requirements; performing a flexible beam bending fatigue test, monitoring the flexible beam bending load in the test process by using a strain monitoring load mode; and performing test monitoring by means of test load drop and upgrade according to strain output load values and edgewise forces on the test piece fixing joint after all the strain gauges on the test piece are damaged. The technical scheme of the application solves the problems of prolonged test period, low test efficiency, increased labor cost, wasted test resources, and difficulty in completing the test task within a specified time.

Description

TECHNICAL FIELD

[0001] The present application relates to, but is not limited to, the technical field of helicopter flexible beam fatigue test, and in particular to a load monitoring method for bending fatigue test of a flexible beam of an unmanned helicopter. BACKGROUND

[0002] The bearingless rotor of a helicopter has the advantages of high control efficiency, good agility, high reliability and simple maintenance, and is one of the main development directions of rotor technology. Therefore, many advanced helicopters in the world adopt the bearingless rotor configuration. Thus, a new type of unmanned helicopter first adopts the bearingless rotor configuration in the structural design of the main rotor.

[0003] The bearingless rotor structure eliminates the flap hinge, lag hinge and pitch hinge of the traditional hinged rotor structure of a helicopter, and completely relies on the flap and torsional deformation of the flexible beam in the hub support arm to realize the movement of the flap, lag and pitch of the blade. The stress condition of the flexible beam is relatively complex, and the flexible beam bears all the loads transmitted from the blade. Therefore, it is particularly important to perform a fatigue test on the flexible beam. At present, in the bending fatigue test of the flexible beam, the test loading stroke is large. In this large-stroke loading test process, the surface strain of the test piece is large, and the strain gauges attached to the surface of the test piece cannot be kept intact for a long time. Under the condition of large-stroke loading, the surface strain gauges of the test piece will fail after several ten-thousands of loading, and cannot play a monitoring role. In addition, if the load of the monitoring section is used to monitor the changes in the entire test process of the test piece, the flexible beam bending fatigue test piece needs to be re-pasted and calibrated to continue monitoring the test. This monitoring method needs to repeat the pasting and calibration multiple times before the test number reaches the target requirement, which greatly prolongs the test cycle, is low in efficiency, increases the labor cost and wastes test resources, and further causes the bending fatigue test of the flexible beam to be unable to complete the test task within the specified time and ensure the test node. SUMMARY

[0004] The present application aims to solve the above problems. An unmanned helicopter flexible beam bending fatigue test load monitoring method is provided to solve the problems in the existing flexible beam bending fatigue test, i.e., due to the use of large-stroke loading, the surface strain of the test piece is large, and the pasting and calibration need to be repeated multiple times during the test, thereby prolonging the test cycle, reducing the test efficiency, increasing the labor cost, wasting test resources, and making it difficult to complete the test task within the specified time.

[0005] The technical solution of the present application is as follows. An unmanned helicopter flexible beam bending fatigue test load monitoring method is provided, which comprises the following steps.

[0006] Step 1: Paste strain gauges on the flexible beam bending fatigue test piece and the test piece fixing joint. The flexible beam bending fatigue test piece is a test piece of the flexible beam of a bearingless rotor.

[0007] Step 2, check the validity of all strain gauge pasting;

[0008] Step 3, calibrate all specified sections of the flexible beam bending fatigue test piece and test piece fixed joint to obtain the calibration coefficient k of each specified section;

[0009] Step 4, load adjustment before the flexible beam bending fatigue test to obtain the load value of the monitoring section that meets the test task requirements; wherein the monitoring section is a selected section from the specified section;

[0010] Step 5, perform the flexible beam bending fatigue test, and use strain monitoring load method during the flexible beam bending fatigue test; wherein the flexible beam bending load is monitored during the flexible beam bending fatigue test;

[0011] Step 6, after all strain gauges on all specified sections of the flexible beam bending fatigue test piece are damaged, the test load is decreased and upgraded to implement test monitoring according to the strain output load value and the flapwise force on the fixed joint.

[0012] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method described above, in the step 1,

[0013] The pasting position of the flexible beam bending fatigue test piece is determined according to the test task book, and the pasting position of the test piece fixed joint is determined according to the shape of the fixed joint and the regularity of the shape at the pasting position.

[0014] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method described above, the step 2 includes:

[0015] Check whether the pasting position of the strain gauge meets the requirements, and check the integrity of the soldering wire and the wiring of the strain gauge.

[0016] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method described above, the calibration method in the step 3 is:

[0017] For each specified section, the linear relationship k between the section strain ε and the section bending moment M of the specified section is used, that is, M=kε, to obtain the calibration coefficient k of each specified section.

[0018] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method described above, the load adjustment method in the step 4 is:

[0019] During the load debugging process, the load is applied to the test piece and the test piece fixing joint, the cross section strain ε of each designated cross section is directly measured by the strain gauge, the bending moment load M on each designated cross section is obtained in combination with the calibration coefficient k of each designated cross section obtained in step 3, and the load value of the monitoring cross section meeting the test task requirements is obtained according to the requirements of the test task book.

[0020] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method as described above, the fatigue test in step 5 is performed in the following manner:

[0021] The flap bending moment cylinder is loaded with the flap bending moment load, the displacement of the flap bending moment cylinder is adjusted, the load of the monitoring cross section reaches the requirements of the test task book, after meeting the requirements of the test task book, the horizontal installation position of the test piece is kept, the displacement of the flap bending moment cylinder is kept unchanged, and the load of the monitoring cross section is kept at the load value meeting the requirements of the test task.

[0022] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method as described above, the monitoring of the flexible beam bending load in step 5 is performed in the following manner:

[0023] During the monitoring process, the load values of all other designated cross sections and the output flap force when the load value of the monitoring cross section meets the requirements of the test task are recorded, and the average load value obtained by recording at least three times is taken as the initial load value and the initial applied flap force of all designated cross sections; wherein, the recorded output flap force is directly obtained by the flap sensor.

[0024] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method as described above, the test load in step 6 is lowered and upgraded, and the strain output load value and the flap force on the fixing joint are used to implement test monitoring in the following manner:

[0025] The strain output load value and the flap force on the fixing joint are compared with the strain output load value and the flap force on the fixing joint when the load of the monitoring cross section meets the requirements of the test task, and it is observed whether the change is within the preset range, the strain output load value on the fixing joint is used as the first monitoring strategy, and the flap force output by the sensor is used as the second monitoring strategy, so as to realize the monitoring manner of multiple monitoring strategies cooperating to monitor the test load

[0026] The beneficial effects of the present application: the embodiment of the present application provides a flexible beam bending fatigue test load monitoring method for unmanned helicopter, which is for the bending fatigue test of the flexible beam of the bearingless rotor. The overall test process of the test includes: pasting strain gauges on the test piece and the test piece fixing joint, and checking the effectiveness of the strain gauge pasting; calibrating all specified sections of the test piece and the test piece fixing joint; performing load debugging before the test to obtain the load value of the monitoring section that meets the test task requirements; performing the flexible beam bending fatigue test, and monitoring the bending load of the flexible beam during the test; after all the strain gauges on the test piece are damaged, the test load is lowered and upgraded to implement the test monitoring according to the strain output load value and the flapping force on the fixing joint. The above-mentioned fatigue test load monitoring method provided by the embodiment of the present application is used to perform the bending fatigue test on the flexible beam of the unmanned helicopter, so that the output strain value of each specified section can be obtained after the initial load debugging is completed, and during the test, the monitoring results of the strain gauges on the specified sections at different positions are used as the test results. The test process does not need to be repeated multiple times, and only one pasting and calibration can complete the entire test process. Compared with the existing test method, the test period is greatly shortened, the test efficiency is improved, the test is efficiently completed, the labor cost is reduced, the waste of test resources is reduced, and the test task can be completed within the specified time. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, which are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0028] Figure 1 A flowchart of the flexible beam bending fatigue test load monitoring method for unmanned helicopter provided by the embodiment of the present application is shown in the figure;

[0029] Figure 2 A schematic diagram of the section pasting of the test piece and the fixing joint in the flexible beam bending fatigue test load monitoring method for unmanned helicopter provided by the embodiment 2 of the present application is shown in the figure;

[0030] Figure 3 A schematic diagram of the flexible beam bending fatigue test loading in the flexible beam bending fatigue test load monitoring method for unmanned helicopter provided by the embodiment 2 of the present application is shown in the figure;

[0031] Figure 4 A schematic diagram of the flexible beam bending fatigue test displacement loading in the flexible beam bending fatigue test load monitoring method for unmanned helicopter provided by the embodiment 2 of the present application is shown in the figure

[0032] Figure 5The strain output schematic diagram of each designated section on the flexible beam bending fatigue test piece in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment 2 of the present application is shown in the figure.

[0033] Figure 6 The schematic diagram of the waving force sensor feedback in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment 2 of the present application is shown in the figure. Specific embodiments

[0034] In order to make the purpose, technical solutions and advantages of the present application more clear and obvious, the embodiments of the present application will be described in detail below with reference to the drawings. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other arbitrarily without conflict.

[0035] As described in the above background, based on the advantages of the bearingless rotor of the helicopter, the bearingless rotor has become the main development direction of the wing technology. In the existing flexible beam bending fatigue test of this kind of bearingless rotor, due to the use of large-stroke loading method, the surface strain of the test piece is large, and the test piece needs to be pasted and calibrated repeatedly during the test, thereby prolonging the test cycle, reducing the test efficiency, increasing the labor cost, wasting the test resources, and the test is difficult to complete the test task within the specified time.

[0036] In order to solve the above problems, the present application provides an unmanned helicopter flexible beam bending fatigue test load monitoring method to ensure efficient completion of the test and save cost.

[0037] The present application provides the following specific embodiments which can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0038] Figure 1 The flowchart of the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment of the present application is shown in the figure. The load monitoring method provided by the embodiment of the present application includes the following steps:

[0039] Step 1, pasting strain gauges on the flexible beam bending fatigue test piece and the test piece fixing joint, the flexible beam bending fatigue test piece is the test piece of the flexible beam of the bearingless rotor;

[0040] Step 2, checking the effectiveness of all strain gauges;

[0041] Step 3, calibrating all designated sections of the flexible beam bending fatigue test piece and the test piece fixing joint to obtain the calibration coefficient k of each designated section;

[0042] Step 4, load adjustment before the flexible beam bending fatigue test is performed to obtain the load value of the monitoring section meeting the test task requirements; wherein the monitoring section is one selected from the specified sections;

[0043] Step 5, performing the flexible beam bending fatigue test, and using the strain monitoring load method to perform the fatigue test during the flexible beam bending fatigue test; wherein the bending load of the flexible beam is monitored during the flexible beam bending fatigue test;

[0044] Step 6, after all the strain gauges on the specified sections of the flexible beam bending fatigue test piece are damaged, the test load is decreased and upgraded to fix the strain output load value and the flapping force of the joint to implement the test monitoring.

[0045] In an implementation manner of the embodiment of the present application, in step 1, the patch position of the flexible beam bending fatigue test piece is determined according to the test task book requirements, and the patch position of the test piece fixed joint is determined according to the shape of the fixed joint and the regularity of the shape at the patch position.

[0046] In an implementation manner of the embodiment of the present application, step 2 includes checking whether the paste position of the strain gauge meets the requirements and checking the welding line and the wiring of the strain gauge.

[0047] In an implementation manner of the embodiment of the present application, the calibration method in step 3 is:

[0048] For each specified section, the calibration coefficient k of each specified section is obtained by using the linear relationship k between the section strain ε of each specified section and the section bending moment M of the present specified section, i.e. M=kε.

[0049] In an implementation manner of the embodiment of the present application, the load adjustment method in step 4 is:

[0050] During the load adjustment, the section strain ε of each specified section is directly measured by the strain gauge by applying load to the test piece and the test piece fixed joint, the bending moment load M on each specified section is obtained by combining the calibration coefficient k of each specified section obtained in step 3, and the load value of the monitoring section meeting the test task requirements is obtained according to the test task book requirements.

[0051] In an implementation manner of the embodiment of the present application, the fatigue test method in step 5 is:

[0052] The waving bending moment actuating cylinder is loaded with the waving bending moment load, the displacement of the waving bending moment actuating cylinder is adjusted, the loading load of the monitoring section reaches the requirement of the test task, after the requirement of the test task is met, the horizontal installation position of the test piece is kept, the displacement of the waving bending moment actuating cylinder is kept unchanged, and the load of the monitoring section is kept at the load value meeting the requirement of the test task.

[0053] In an implementation manner of the embodiment of the present application, the monitoring manner of the flexible beam bending load in step 5 is as follows:

[0054] The load values of all the specified sections and the output waving force when the load value of the monitoring section meets the test task requirement are recorded in the monitoring process, the average load value obtained by taking at least three times is taken as the initial load value and the initial applied waving force of all the specified sections, and the recorded output waving force is directly obtained from the waving sensor.

[0055] In an implementation manner of the embodiment of the present application, the test monitoring manner in step 6 is that the test load is reduced and upgraded to implement the test monitoring by the strain output load value and the waving force of the fixed joint.

[0056] The strain output load value and the waving force of the fixed joint are compared with the strain output load value and the waving force of the fixed joint when the load of the monitoring section meets the test task requirement, whether the change is within the preset range is observed, the strain output load value of the fixed joint is taken as the first monitoring strategy, the waving force output by the sensor is taken as the second monitoring strategy in the test monitoring, and the monitoring manner of the multiple monitoring strategies is cooperated to monitor the test load.

[0057] An embodiment of the present invention provides a load monitoring method for a bending fatigue test of a flexible beam of an unmanned helicopter. The entire test process includes: pasting strain gauges on the test piece and the fixed joints of the test piece, and checking the effectiveness of the strain gauge pasting; calibrating all specified sections of the test piece and the fixed joints of the test piece; performing load debugging before the test to obtain the load value of the monitoring section that meets the requirements of the test task; executing a flexible beam bending fatigue test, using a strain monitoring load method to perform the fatigue test during the test, and monitoring the bending load of the flexible beam; after all strain gauges on the test piece are damaged, the test load is reduced and upgraded to implement test monitoring by outputting the load value and swinging force of the strain on the fixed joint. By using the fatigue test load monitoring method provided in an embodiment of the present invention to perform a bending fatigue test on the flexible beam of an unmanned helicopter, the output strain value of each specified section can be obtained after the initial load debugging is completed. During the test, the monitoring results of the strain gauges on the specified sections at different positions are used as the test results. During the entire test process, there is no need to repeat the patching and calibration multiple times. The entire test process can be completed by performing the patching and calibration once. That is, compared with the existing test method, the test cycle is shortened to a great extent, the test efficiency is accelerated, thereby ensuring the efficient completion of the test, and reducing labor costs, reducing the waste of test resources, and ensuring that the test task is completed within the specified time.

[0058] The following is a schematic illustration of the implementation of the load monitoring method for the bending fatigue test of the flexible beam of an unmanned helicopter provided by the embodiment of the present invention through several specific embodiments.

[0059] Example 1:

[0060] This embodiment 1 provides a method for monitoring load during bending fatigue testing of a flexible beam of an unmanned helicopter, which is implemented by the following steps:

[0061] Step 1: Paste strain gauges on the flexible beam bending fatigue test piece and the test piece fixed joints according to the test task book.

[0062] In this step, the patch position of the test piece used for the flexible beam bending fatigue test is given according to relevant technical requirements, for example, according to the requirements of the test task book, and the patch position of the test piece fixed joint is determined according to the shape of the fixed joint and the regularity of the shape of the patch.

[0063] Step 2: Check the effectiveness of all strain gauges; specifically check the pasting position and welding wires and wiring to ensure there are no problems.

[0064] Step 3: calibrate all designated sections (such as sections specified in the test task book) of the flexible beam bending fatigue test specimen and the fixed joints of the test specimen.

[0065] In this step, for each specified section, the calibration coefficient k of each specified section is obtained by using the linear relationship k between the section strain ε and the corresponding specified section bending moment M, i.e. M=kε.

[0066] In step 4, the section strain ε of each specified section in the flexible beam bending fatigue test debugging can be directly obtained by the strain measurement system (for example, by applying a load to the entire test piece, the strain is directly measured by the strain gauge), and then combined with the calibration coefficient k of each specified section, the bending moment load M on each specified section of the test piece can be obtained. According to the requirements of the test task book, the load of the monitoring section (one specified section is selected as the monitoring section) meets the test task requirements, i.e. the fatigue test can be carried out.

[0067] In step 5, the flexible beam bending fatigue test is carried out, and the strain monitoring load method is used in the flexible beam bending fatigue test.

[0068] The flexible beam bending fatigue test method in this step is: the edgewise bending moment load is applied by the edgewise bending moment actuator cylinder, the displacement of the edgewise bending moment actuator cylinder is adjusted to make the test piece load meet the requirements of the test task book, and after meeting the requirements of the test task book, the horizontal installation position of the test piece is kept, the displacement of the edgewise bending moment actuator cylinder is controlled to be unchanged, and the load of the monitoring section is kept at the load value meeting the requirements of the test task book.

[0069] In this step, the flexible beam bending load is monitored during the execution of the flexible beam bending fatigue test, and the monitoring method is: during the monitoring process, the load values of all specified sections (including the fixed joint) and the output edgewise force when the load of the monitoring section meets the requirements of the test task book are recorded, and the average load value is taken as the initial load and the initial edgewise force of all specified sections, and the output edgewise force can be directly obtained from the edgewise sensor.

[0070] In step 6, during the flexible beam bending fatigue test, with the increase of the test number, all strain gauges on the specified sections of the flexible beam bending fatigue test piece are damaged, and the test load is decreased and upgraded mainly by monitoring the strain output load value and the edgewise force of the fixed joint. The specific load monitoring method is: the strain output load value and the edgewise force of the fixed joint are compared with the load of the monitoring section meeting the requirements of the test task book, and it is observed whether the change is within the preset range (usually required to be within 10%), the strain output load value of the fixed joint is used as the first monitoring strategy, and the edgewise force output by the sensor is used as the second monitoring strategy, so as to realize the cooperative monitoring of the test load in multiple ways; wherein, the sensor is installed on the edgewise actuator cylinder.

[0071] Example 2:

[0072] The embodiment 2 provides a flexible beam bending fatigue test load monitoring method of an unmanned helicopter, and is implemented through the following steps:

[0073] Step 1, according to the test task book, strain gauges are pasted on the flexible beam bending fatigue test piece and the test piece fixing joint.

[0074] In this step, the test piece patch position is given according to the relevant technical requirements, for example, the test piece fixing joint patch position is selected at the 1# profile patch, the 1# profile patch position is good, the operation is strong, and the error corresponding to the strain output is small; the 2# profile patch, the 3# profile patch, the 4# profile patch and the 5# profile patch are respectively located at 5%, 7%, 22% and 40% of the distance from the test piece to the center position of the fixing end bolt hole. Figure 2 As shown in the figure, it is a schematic diagram of the profile patch of the test piece and the fixing joint in the flexible beam bending fatigue test load monitoring method of the unmanned helicopter provided by the embodiment 2 of the present application.

[0075] Step 2, check that all the strain gauges are pasted perfectly, the pasting position meets the requirements, and the welding line and the wire are complete and have no problems.

[0076] Step 3, calibrate all the specified profiles of the flexible beam bending fatigue test piece and the test piece fixing joint, utilize the linear relationship k between the profile strain ε and the profile bending moment M of the specified profile, that is, M=kε, and obtain the calibration coefficient k of each specified profile.

[0077] Step 4, in the flexible beam bending fatigue test debugging, the profile strain ε of each specified profile can be directly obtained through the strain measurement system (for example, by applying a load to the whole test piece, directly measuring by the strain gauge), and then combined with the calibration coefficient k of each specified profile, the bending moment load M on each specified profile of the test piece can be obtained, according to the requirements of the test task book, the 5# profile in the formula is selected as the monitoring profile, and when the load of the 5# profile meets the test requirement load value M=650 Nm, the fatigue test can be performed. Figure 2

[0078] Step 5, perform the flexible beam bending fatigue test, and the strain monitoring load mode is adopted in the flexible beam bending fatigue test.

[0079] The flexible beam bending fatigue test mode in this step is that the flap bending moment cylinder is loaded with the flap bending moment load, the displacement of the flap bending moment cylinder is adjusted, the test piece is loaded with the load M=650 Nm to meet the requirements of the test task book, after the requirements of the test task book are met, the horizontal installation is kept unchanged, the loading displacement of the flap bending moment cylinder is kept unchanged at ±94.5 mm, and the loading is continued. Figure 3 As shown in the figure, it is a schematic diagram of the flexible beam bending fatigue test loading in the flexible beam bending fatigue test load monitoring method of the unmanned helicopter provided by the embodiment 2 of the present application.​Figure 4 Fig. 2 shows a schematic diagram of the displacement loading of the flexible beam bending fatigue test in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment 2 of the present application.

[0080] In this step, the flexible beam bending load is monitored during the flexible beam bending fatigue test, and the monitoring method is as follows: the load values and the edgewise bending moment cylinder sensor output edgewise force of the other specified sections (1# section, 2# section, 3# section, 4# section) are recorded when the monitoring section (5# section) meets the requirements during the monitoring process, and the average load value is recorded more than three times and taken as the initial load of all the specified sections and the initial edgewise force, wherein the output edgewise force can be directly obtained from the edgewise sensor. For example, Figure 5 Fig. 3 shows a schematic diagram of the strain output of each specified section of the flexible beam bending fatigue test piece in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment 2 of the present application.

[0081] Step 6: During the flexible beam bending fatigue test, with the increase of the test times, all the strain gauges on the flexible beam test piece (2# section, 3# section, 4# section, 5# section) are damaged, and the test load cannot be monitored when it decreases, and the test load decrease is mainly monitored by the strain output load value of the fixed joint (i.e. 1# section) and the sensor output edgewise force during the subsequent test process. The specific load monitoring method is to compare the strain output load value change of the fixed joint (1# section) with the sensor output edgewise force to obtain the monitoring section debugging load state, and to observe whether there is a change. In the test monitoring, the strain output load value of the fixed joint (1# section) is the first monitoring method, and the sensor output edgewise force is the second monitoring method, which can improve the test load monitoring and realize the collaborative monitoring of the test load in multiple ways. For example, Figure 6 Fig. 4 shows a schematic diagram of the feedback of the flexible beam bending fatigue edgewise force sensor in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided by the embodiment 2 of the present application.

[0082] Referring to Figure 5 and Figure 6 It can be seen that the 5# section is the monitoring section, Figure 5 Fig. 5 shows the output strain values of each specified section after the initial load debugging is completed; for example, Figure 6 As shown in Fig. 6, the flexible beam bending fatigue edgewise force changes relatively small during the early test process; among 0-30,000 times, the monitoring results of each specified section of the test piece are mainly used as the basis, and among 40,000-50,000 times, the monitoring results of the 1# section of the fixed joint are mainly used as the basis.

[0083] With the above flexible beam load monitoring method, the strain gauges can monitor the test load all the time, and ensure the effective test.

[0084] Although the embodiments of the present application have been disclosed with reference to the above embodiments, the present application is not limited to the above embodiments. Any person skilled in the art, without departing from the spirit and scope of the present application, can make any modification and change in the form and details, but the patent protection scope of the present application should be determined by the appended claims.

Claims

1. A method for monitoring loads in a flexible beam fatigue test of an unmanned helicopter, characterized by, The method comprises the following steps: Step 1, paste strain gauges on the flexible beam bending fatigue test piece and the test piece fixing joint, wherein the flexible beam bending fatigue test piece is a test piece of a bearingless rotor flexible beam; Step 2, check the effectiveness of the paste of all strain gauges; Step 3, calibrate all specified sections of the flexible beam bending fatigue test piece and the test piece fixing joint to obtain the calibration coefficient k of each specified section; Step 4, perform pre-test load adjustment of the flexible beam bending fatigue test to obtain the load value of the monitoring section meeting the test task requirements; wherein the monitoring section is a selected section from the specified sections; Step 5, perform the flexible beam bending fatigue test, and use the strain monitoring load method to perform the fatigue test during the flexible beam bending fatigue test; wherein the flexible beam bending load is monitored during the flexible beam bending fatigue test; Step 6, after all the strain gauges on all the specified sections of the flexible beam bending fatigue test piece are damaged, the test load is lowered and upgraded to implement test monitoring according to the strain output load value and the flapping force on the fixing joint.

2. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1, characterized in that, In the step 1, The paste positions of the flexible beam bending fatigue test piece are determined according to the test task book requirements, and the paste positions of the test piece fixing joint are determined according to the shape of the fixing joint and the regularity of the shape at the paste position.

3. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1, characterized in that, The step 2 comprises: Check whether the paste positions of the strain gauges meet the requirements, and check the completeness of the soldering wires and the connecting wires of the strain gauges.

4. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1, characterized in that, The calibration method in the step 3 is: For each specified section, the sectional strain ε of each specified section and the sectional bending moment M of the specified section are linearly related, that is, M=kε, to obtain the calibration coefficient k of each specified section.

5. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1, characterized in that, The load adjustment method in the step 4 is: During the load adjustment, the sectional strain ε of each specified section is directly measured by the strain gauges by applying loads to the test piece and the test piece fixing joint, the calibration coefficient k of each specified section is obtained in the step 3, the bending moment load M on each specified section is obtained, and the load value of the monitoring section meeting the test task requirements is obtained according to the test task book requirements.

6. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1, characterized in that, The fatigue test method in the step 5 is: The flapping bending moment load is loaded by the flapping bending moment actuator cylinder, the displacement of the flapping bending moment actuator cylinder is adjusted, the loading load of the monitoring section reaches the requirements of the test task book, the horizontal installation position of the test piece is kept, the displacement of the flapping bending moment actuator cylinder is kept unchanged, and the load of the monitoring section is kept at the load value meeting the requirements of the test task book.

7. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 6, characterized in that, The monitoring method of the flexible beam bending load in the step 5 is: During the monitoring, the load values of all the specified sections and the output flapping force are recorded when the load value of the monitoring section meets the requirements of the test task, the average load value of at least three times is taken as the initial load value and the initial applied flapping force of all the specified sections, and the output flapping force is directly obtained by the flapping sensor.

8. The unmanned helicopter flexible beam fatigue test load monitoring method according to any one of claims 1 to 7, characterized in that, The test monitoring method in the step 6 is: The strain output load value on the fixed joint and the flap force are compared with the load of the monitoring section, and the strain output load value on the fixed joint and the flap force are monitored when the load of the monitoring section meets the test task requirements, and it is observed whether the changes are within the preset range, and in the test monitoring, the strain output load value on the fixed joint is monitored as the first monitoring strategy, and the flap force output by the sensor is monitored as the second monitoring strategy, so as to realize the monitoring mode of multiple monitoring strategies cooperating to monitor the test load.

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