Unmanned helicopter flexible beam bending fatigue test load monitoring method

Abstract

The invention discloses an unmanned helicopter flexible beam bending fatigue test load monitoring method comprising the following steps: pasting strain gauges on a test piece and a test piece fixing joint, and checking the effectiveness of the pasting of the strain gauges; calibrating all specified sections of the test piece and the test piece fixing joint; carrying out load debugging before the test so as to obtain a load value of the monitoring section meeting the test task requirement; carrying out a bending fatigue test of the flexible beam, carrying out the fatigue test in a strain monitoring load mode in the test process, and monitoring the bending load of the flexible beam; after all the strain gauges on the test piece are damaged, the test load is lowered and upgraded to fix the strain output load value and the flapping force on the joint to implement test monitoring. According to the technical scheme, the problems that the test period is prolonged, the test efficiency is low, the labor cost is increased, the test resources are wasted, and the test task is difficult to complete in the specified time are solved.

Description

Technical Field

[0001] The invention relates to the field of but not limited to the technical field of fatigue test of helicopter flexible beams, and in particular to a load monitoring method for bending fatigue test of flexible beams of unmanned helicopters. Background Art

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

[0003] The bearingless rotor structure gets rid of the traditional helicopter articulated rotor structure, cancels the flapping hinge, shimmy hinge and pitch hinge, and completely relies on the flapping and torsional deformation of the flexible beam in the hub support arm to achieve the flapping, shimmy and pitch movement of the blade. The force condition of the flexible beam is relatively complex, and it bears all the loads transmitted by the blade, so it is particularly important to conduct fatigue test assessment on the flexible beam. At present, in the bending fatigue test of the flexible beam, the test loading stroke is large. During this large stroke loading test, the surface strain of the test piece is large, and the strain gauge attached to the surface of the test piece cannot remain intact for a long time. After loading tens of thousands of times under this large stroke loading condition, the strain gauge on the surface of the test piece will fail and cannot play a monitoring role. In addition, if the load of the monitoring section is used to monitor the changes of the test piece during the entire test process, the flexible beam bending fatigue test piece needs to be re-patched and calibrated before the test monitoring can continue. Before the target number of tests is reached, this monitoring method during the test process requires repeated patching and calibration, which greatly prolongs the test cycle, is inefficient, and increases labor costs and wastes test resources, further resulting in the flexible beam bending fatigue test failing to complete the test task within the specified time and ensure the test node. Summary of the invention

[0004] Purpose of the present invention: In order to solve the above-mentioned problems, an embodiment of the present invention provides a load monitoring method for an unmanned helicopter flexible beam bending fatigue test, so as to solve the problems in the existing flexible beam bending fatigue test, that is, due to the use of a large-stroke loading method, the surface strain of the test piece is large, and multiple patches and calibrations need to be repeated during the test, thereby extending the test cycle, low test efficiency, increased labor costs, waste of test resources, and difficulty in completing the test task within the specified time.

[0005] The technical solution of the present invention: The embodiment of the present invention provides a method for monitoring load of a bending fatigue test of a flexible beam of an unmanned helicopter, comprising:

[0006] Step 1, affixing strain gauges to a flexible beam bending fatigue test piece and a test piece fixed joint, wherein the flexible beam bending fatigue test piece is a test piece of a flexible beam of a bearingless rotor;

[0007] Step 2, check the effectiveness of all strain gauges;

[0008] Step 3, calibrating all designated sections of the flexible beam bending fatigue test piece and the fixed joints of the test piece to obtain a calibration coefficient k for each designated section;

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

[0010] Step 5, performing a flexible beam bending fatigue test, during which a strain monitoring load method is used to perform a fatigue test; wherein during the flexible beam bending fatigue test, the flexible beam bending load is monitored;

[0011] Step 6: After all strain gauges on all designated sections of the flexible beam bending fatigue test piece are damaged, the test load is reduced and upgraded to implement test monitoring by outputting the strain load value and swinging force on the fixed joint.

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

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

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

[0015] Check whether the pasting position of the strain gauge meets the requirements, and check whether the welding wire and wiring of the strain gauge are complete.

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

[0017] For each designated section, the calibration coefficient k of each designated section is obtained by using the linear relationship k between the section strain ε of each designated section and the section bending moment M of the designated section, that is, M=kε.

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

[0019] During the load debugging process, loads are applied to the test piece and the fixed joints of the test piece. The section strain ε of each specified section is directly measured by the strain gauge. Combined with the calibration coefficient k of each specified section obtained in step 3, the bending moment load M on each specified section is obtained. According to the requirements of the test task book, the load value of the monitoring section that meets the test task requirements is obtained.

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

[0021] The swinging bending moment load is loaded by the swinging bending moment actuator cylinder, and the displacement of the swinging bending moment actuator cylinder is adjusted to make the loading load of the monitoring section meet 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 maintained, and the displacement of the swinging bending moment actuator cylinder is controlled to remain unchanged to ensure that the load on the monitoring section is maintained at a load value that meets the test task requirements.

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

[0023] During the monitoring process, the load value of the monitored section meets the test task requirements, and the load values ​​and output swinging forces of all other specified sections are recorded. After recording at least three times, the average load value is taken as the initial load value and initial applied swinging force of all specified sections; wherein the recorded output swinging force is directly obtained from the swinging sensor.

[0024] Optionally, in the unmanned helicopter flexible beam bending fatigue test load monitoring method as described above, the test load reduction and upgrade in step 6 are implemented by the strain output load value and swinging force on the fixed joint to monitor the test in the following manner:

[0025] Compare the strain output load value and swinging force on the fixed joint with the strain output load value and swinging force on the fixed joint when the load of the monitoring section meets the test task requirements, and observe whether the change is within the preset range. In the test monitoring, the strain output load value monitoring on the fixed joint is used as the first monitoring strategy, and the swinging force output by the sensor is used as the second monitoring strategy, so as to realize the monitoring method of the test load coordinated by multiple monitoring strategies

[0026] Beneficial effects of the present invention: An embodiment of the present invention provides a load monitoring method for a bending fatigue test of a flexible beam of an unmanned helicopter, which is a bending fatigue test of a flexible beam of a bearingless rotor. The overall test process of the test 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 monitored section that meets the requirements of the test task; executing a bending fatigue test of the flexible beam, and performing fatigue testing using a strain monitoring load method during the test, and monitoring the bending load of the flexible beam; after all the strain gauges on the test piece are damaged, the test load is reduced and upgraded to implement test monitoring by outputting the strain load value and the swinging force on the fixed joint. By adopting the fatigue test load monitoring method provided in the 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. In the test process, 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 the labor cost, reducing the waste of test resources, and can ensure that the test task is completed within the specified time. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 1 A schematic flow chart of a method for monitoring load in a bending fatigue test of a flexible beam of an unmanned helicopter provided by an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a cross-sectional patch of a test piece and a fixed joint in a load monitoring method for a bending fatigue test of a flexible beam of an unmanned helicopter provided in Example 2 of the present invention;

[0030] Figure 3 A schematic diagram of loading of a flexible beam bending fatigue test in a method for monitoring load of a flexible beam bending fatigue test of an unmanned helicopter provided in Example 2 of the present invention;

[0031] Figure 4 Schematic diagram of displacement loading of a flexible beam bending fatigue test in a load monitoring method for a flexible beam bending fatigue test of an unmanned helicopter provided in Example 2 of the present invention

[0032] Figure 5A schematic diagram of strain output of each designated section on a flexible beam bending fatigue test piece in a load monitoring method for a flexible beam bending fatigue test of an unmanned helicopter provided in Example 2 of the present invention;

[0033] Figure 6 A schematic diagram of the feedback of the flexible beam bending fatigue swinging force sensor in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided in Example 2 of the present invention. Specific implementation plan

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

[0035] As explained in the above background technology, based on the advantages of helicopter bearingless rotors, this bearingless rotor has become the main development direction of wing technology. In the existing flexible beam bending fatigue test of this type of bearingless rotor, due to the use of a large stroke loading method, the surface strain of the test piece is large, and the patching and calibration need to be repeated many times during the test, which leads to extended test cycles, low test efficiency, increased labor costs, waste of test resources, and difficulty in completing the test task within the specified time.

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

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

[0038] Figure 1 A flow chart of a load monitoring method for a flexible beam bending fatigue test of an unmanned helicopter provided by an embodiment of the present invention. The load monitoring method provided by an embodiment of the present invention comprises the following steps:

[0039] Step 1, affixing strain gauges to a flexible beam bending fatigue test piece and a test piece fixed joint, wherein the flexible beam bending fatigue test piece is a test piece of a flexible beam of a bearingless rotor;

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

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

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

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

[0044] Step 6: After all strain gauges on all designated sections of the flexible beam bending fatigue test piece are damaged, the test load is reduced and upgraded to implement test monitoring by outputting the strain load value and swinging force on the fixed joint.

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

[0046] In an implementation of the embodiment of the present invention, the above step 2 includes: checking whether the pasting position of the strain gauge meets the requirements, and checking whether the welding wires and wiring of the strain gauge are complete.

[0047] In one implementation of the embodiment of the present invention, the calibration method in the above step 3 is:

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

[0049] In one implementation of the embodiment of the present invention, the load debugging method in the above step 4 is:

[0050] During the load debugging process, loads are applied to the test piece and the fixed joints of the test piece. The section strain ε of each specified section is directly measured by the strain gauge. Combined with the calibration coefficient k of each specified section obtained in step 3, the bending moment load M on each specified section is obtained. According to the requirements of the test task book, the load value of the monitoring section that meets the test task requirements is obtained.

[0051] In one implementation of the embodiment of the present invention, the fatigue test is performed in step 5 as follows:

[0052] The swinging bending moment load is loaded by the swinging bending moment actuator cylinder, and the displacement of the swinging bending moment actuator cylinder is adjusted to make the loading load of the monitoring section meet 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 maintained, and the displacement of the swinging bending moment actuator cylinder is controlled to remain unchanged to ensure that the load on the monitoring section is maintained at a load value that meets the test task requirements.

[0053] In one implementation of the embodiment of the present invention, the method of monitoring the bending load of the flexible beam in the above step 5 is:

[0054] During the monitoring process, the load value of the monitored section meets the test task requirements, and the load values ​​and output swinging forces of all other specified sections are recorded. After recording at least three times, the average load value is taken as the initial load value and initial applied swinging force of all specified sections; wherein the recorded output swinging force is directly obtained from the swinging sensor.

[0055] In one implementation of the embodiment of the present invention, the test load reduction and upgrade in the above step 6 are implemented by the strain output load value and the swinging force on the fixed joint to implement the test monitoring in the following manner:

[0056] The strain output load value and swinging force on the fixed joint are compared with the strain output load value and swinging force on the fixed joint when the load of the monitoring section meets the test task requirements, and it is observed whether the changes are within the preset range. In the test monitoring, the strain output load value monitoring on the fixed joint is used as the first monitoring strategy, and the swinging force output by the sensor is used as the second monitoring strategy, realizing a monitoring method in which multiple monitoring strategies coordinately 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 a test piece and a fixed joint of the test piece, and checking the effectiveness of pasting the strain gauges; calibrating all specified sections of the test piece and the fixed joint of the test piece; performing load debugging before the test to obtain a load value of the monitored section that meets the requirements of the test task; executing a bending fatigue test of the flexible beam, performing the fatigue test in a strain monitoring load manner 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 adopting the fatigue test load monitoring method provided in the 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. In the test process, 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 the labor cost, reducing the waste of test resources, and can ensure that the test task is completed within the specified time.

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

[0059] Embodiment 1:

[0060] This embodiment 1 provides a method for monitoring load in a bending fatigue test 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 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 at the patch.

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

[0064] Step 3, calibrate all designated sections (such as the sections designated 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 designated section, a linear relationship k between the section strain ε and the section bending moment M of the corresponding designated section is used, ie, M=kε, to obtain a calibration coefficient k for each designated section.

[0066] Step 4: During the debugging of the flexible beam bending fatigue test, the section strain ε of each designated section can be directly obtained through the strain measurement system (for example, by applying a load to the entire test piece and directly measuring it with a strain gauge), and then combined with the calibration coefficient k corresponding to each designated section, the bending moment load M on each designated section of the test piece can be obtained. According to the requirements of the test task book, the load on the monitoring section (a designated section is selected as the monitoring section) meets the test task requirements, and the fatigue test can be carried out.

[0067] Step 5, performing a flexible beam bending fatigue test, in which a strain monitoring load method is used to perform the fatigue test.

[0068] The flexible beam bending fatigue test method in this step is: load the swinging bending moment load through the swinging bending moment actuator cylinder, adjust the displacement of the swinging bending moment actuator cylinder, make the loading load of the test piece meet the requirements of the test task book, after meeting the requirements of the test task book, maintain the horizontal installation position of the test piece, and adopt the method of controlling the displacement of the swinging bending moment actuator cylinder to remain unchanged to ensure that the load of the monitored section is maintained at a load value that meets the test task requirements.

[0069] In this step, during the flexible beam bending fatigue test, the bending load of the flexible beam is monitored in the following manner: during the monitoring process, the load values ​​and output swinging forces of all other designated sections (including those on fixed joints) are recorded when the load of the monitored section meets the test task requirements. The records are recorded at least three times, and the average load value is taken as the initial load and initial applied swinging force of all designated sections, wherein the output swinging force can be directly obtained by the swinging sensor.

[0070] Step 6. During the flexible beam bending fatigue test, as the number of tests increases, all the strain gauges on all designated sections of the flexible beam bending fatigue test piece are damaged. The test load reduction and upgrade are mainly implemented by the strain output load value and the swinging force on the fixed joint to implement test monitoring. The specific load monitoring method is: the strain output load value and the swinging force on the fixed joint are compared with the strain output load value and the swinging force on the fixed joint when the load of the monitored section meets the test task requirements, and it is observed whether the change is within the preset range (usually the change is required to be within 10%). In the test monitoring, the strain output load value monitoring on the fixed joint is used as the first monitoring strategy, and the swinging force output by the sensor is used as the second monitoring strategy, so as to realize the coordinated monitoring of the test load in multiple ways; wherein, the sensor is installed on the swinging actuator cylinder.

[0071] Embodiment 2:

[0072] This embodiment 2 provides a method for monitoring load in a bending fatigue test of a flexible beam of an unmanned helicopter, which is implemented by the following steps:

[0073] 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.

[0074] In this step, the position of the test piece patch is given according to the relevant technical requirements. For example, the position of the test piece fixed joint patch is selected at the 1# section patch. The 1# section patch has a good position, strong operability, and small error in strain output; the 2# section patch, 3# section patch, 4# section patch, and 5# section patch are respectively located at 5%, 7%, 22%, and 40% of the center position of the fixed end bolt hole of the test piece; Figure 2 , which is a schematic diagram of the cross-sectional patches of the test piece and the fixed joint in the load monitoring method for the unmanned helicopter flexible beam bending fatigue test provided in Example 2 of the present invention.

[0075] Step 2: Check that all strain gauges are well pasted, the pasting position meets the requirements, and the welding wires and wiring are complete and without problems.

[0076] Step 3, calibrate all designated sections of the flexible beam bending fatigue test piece and the fixed joints of the test piece, and use the linear relationship k between the section strain ε and the section bending moment M of the corresponding designated section, that is, M=kε, to obtain the calibration coefficient k of each designated section.

[0077] Step 4: The section strain ε of each specified section in the flexible beam bending fatigue test can be directly obtained through the strain measurement system (for example, by applying a load to the entire test piece and directly measuring it with a strain gauge), and then combined with the calibration coefficient k corresponding to 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, select Figure 2 The 5# section is used as the monitoring section. When the load on the 5# section meets the test requirement of load value M=650Nm, fatigue test can be carried out.

[0078] Step 5, performing a flexible beam bending fatigue test, in which a strain monitoring load method is used to perform the fatigue test.

[0079] The flexible beam bending fatigue test method in this step is: load the swinging bending moment load through the swinging bending moment actuator cylinder, adjust the displacement of the swinging bending moment actuator cylinder, make the test piece load M = 650Nm to meet the requirements of the test task book, and after meeting the requirements of the test task book, keep the horizontal installation unchanged, and keep the swinging bending moment actuator cylinder loading displacement ±94.5mm unchanged, and continue loading. Figure 3 As shown, it is a schematic diagram of the loading of the flexible beam bending fatigue test in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided in Example 2 of the present invention; Figure 4 As shown, it is a schematic diagram of displacement loading of a flexible beam bending fatigue test in a load monitoring method for a flexible beam bending fatigue test of an unmanned helicopter provided in Example 2 of the present invention;.

[0080] During the flexible beam bending fatigue test, the bending load of the flexible beam is monitored in this step. The monitoring method is as follows: when the debugging load of the monitoring section (section 5#) meets the requirements, the load values ​​of other designated sections (section 1#, section 2#, section 3#, section 4#) and the swing force output by the swing moment actuator sensor are recorded for more than three times, and the average load value is taken as the initial load and initial applied swing force of all designated sections. The output swing force can be directly obtained from the swing sensor. Figure 5 , which is a schematic diagram of strain output of each designated section on a flexible beam bending fatigue test piece in a load monitoring method for an unmanned helicopter flexible beam bending fatigue test provided in Example 2 of the present invention.

[0081] Step 6. During the bending fatigue test of the flexible beam, as the number of tests increases, the strain gauges on all designated sections (section 2#, section 3#, section 4#, section 5#) on the flexible beam test piece are all damaged, and the test load cannot be monitored when it decreases. In the subsequent tests, the test load decrease is mainly monitored by the strain output load value on the fixed joint (i.e., section 1#) and the sensor output swing force. The specific load monitoring method is to compare the strain output load value change on the fixed joint (section 1#) with the sensor output swing force to obtain the monitoring section debugging load state and observe whether there is any change. In the test monitoring, the strain output load value on the fixed joint (section 1#) is monitored as the first monitoring method, and the sensor output swing force is monitored as the second monitoring method. The test load monitoring is improved to achieve collaborative monitoring of the test load in multiple ways. Figure 6 , which is a schematic diagram of the flexible beam bending fatigue swinging force sensor feedback in the unmanned helicopter flexible beam bending fatigue test load monitoring method provided in Example 2 of the present invention.

[0082] Reference Figure 5 and Figure 6 It can be seen that the 5# section is the monitoring section. Figure 5 The output strain value of each specified section after the initial load commissioning is completed is shown in FIG. Figure 6 As shown, the bending fatigue swing force of the flexible beam changes relatively little during the early test process; among them, the results of monitoring the designated sections on the test piece are mainly used as the basis for 0 to 30,000 times, and the results of monitoring the 1# section on the fixed joint are used as the basis for 40,000 to 50,000 times.

[0083] By monitoring the load on the flexible beam in the above-mentioned manner, the strain gauge can monitor the test load all the time to ensure that the test is carried out effectively.

[0084] Although the embodiments disclosed in the present invention are as above, the contents are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for monitoring load of bending fatigue test of flexible beam of unmanned helicopter, characterized in that: include: Step 1, affixing strain gauges to a flexible beam bending fatigue test piece and a test piece fixed joint, wherein the flexible beam bending fatigue test piece is a test piece of a flexible beam of a bearingless rotor; Step 2, check the effectiveness of all strain gauges; Step 3, calibrating all designated sections of the flexible beam bending fatigue test piece and the fixed joints of the test piece to obtain a calibration coefficient k for each designated section; Step 4, performing load adjustment before the flexible beam bending fatigue test to obtain a load value of a monitoring section that meets the test task requirements; wherein the monitoring section is a section selected from the specified sections; Step 5, performing a flexible beam bending fatigue test, during which a strain monitoring load method is used to perform a fatigue test; wherein during the flexible beam bending fatigue test, the flexible beam bending load is monitored; Step 6: After all strain gauges on all designated sections of the flexible beam bending fatigue test piece are damaged, the test load is reduced and upgraded to implement test monitoring by outputting the strain load value and swinging force on the fixed joint.

2. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1 is characterized in that: In the step 1, The patch position of the flexible beam bending fatigue test piece is determined according to the requirements of the test task book, and the patch position of the test piece's fixed joint is determined according to the shape of the fixed joint and the regularity of the shape of the patch.

3. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1 is characterized in that: The step 2 comprises: Check whether the pasting position of the strain gauge meets the requirements, and check whether the welding wire and wiring of the strain gauge are complete.

4. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1 is characterized in that: The calibration method in step 3 is: For each designated section, the calibration coefficient k of each designated section is obtained by using the linear relationship k between the section strain ε of each designated section and the section bending moment M of the designated section, that is, M=kε.

5. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1 is characterized in that: The load debugging method in step 4 is: During the load debugging process, loads are applied to the test piece and the fixed joints of the test piece. The section strain ε of each specified section is directly measured by the strain gauge. Combined with the calibration coefficient k of each specified section obtained in step 3, the bending moment load M on each specified section is obtained. According to the requirements of the test task book, the load value of the monitoring section that meets the test task requirements is obtained.

6. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 1 is characterized in that: The method of performing the fatigue test in step 5 is: The swinging bending moment load is loaded by the swinging bending moment actuator cylinder, and the displacement of the swinging bending moment actuator cylinder is adjusted to make the loading load of the monitoring section meet 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 maintained, and the displacement of the swinging bending moment actuator cylinder is controlled to remain unchanged to ensure that the load on the monitoring section is maintained at a load value that meets the test task requirements.

7. The unmanned helicopter flexible beam bending fatigue test load monitoring method according to claim 6 is characterized in that: The method for monitoring the bending load of the flexible beam in step 5 is: During the monitoring process, the load value of the monitored section meets the test task requirements, and the load values ​​and output swinging forces of all other specified sections are recorded. After recording at least three times, the average load value is taken as the initial load value and initial applied swinging force of all specified sections; wherein the recorded output swinging force is directly obtained from the swinging sensor.

8. The method for monitoring load in bending fatigue test of an unmanned helicopter flexible beam according to any one of claims 1 to 7, characterized in that: The test load reduction and upgrade in step 6 are implemented by the method of testing and monitoring the strain output load value and swinging force on the fixed joint as follows: The strain output load value and swinging force on the fixed joint are compared with the strain output load value and swinging force on the fixed joint when the load of the monitoring section meets the test task requirements, and it is observed whether the changes are within the preset range. In the test monitoring, the strain output load value monitoring on the fixed joint is used as the first monitoring strategy, and the swinging force output by the sensor is used as the second monitoring strategy, realizing a monitoring method in which multiple monitoring strategies coordinately monitor the test load.

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