D-Beam composite blade root section fatigue test method and system

Abstract

The application provides a D-shaped beam composite material blade root section fatigue test method and system, and belongs to the technical field of helicopter structure strength design. The method comprises the following steps: patching and calibrating a D-shaped beam blade root section test piece; determining a fatigue test static load and a dynamic load; and then implementing a D-shaped beam blade root section fatigue test. The application proposes a method for applying a static load of a waving bending moment and a wobbling bending moment in a D-shaped beam blade fatigue test. The test static load covers the theoretical static load, solves the problem caused by the static load correction, and can effectively evaluate the fatigue performance of the D-shaped beam blade root section.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of helicopter structure strength design, and particularly relates to a D-shaped beam composite blade root section fatigue test method and system. BACKGROUND

[0002] Large and heavy helicopters have relatively large tonnage, and have high requirements on the rotor system blades in terms of size, load and economy. The D-shaped beam blade has the advantages of lightweight, fewer parts and high structural efficiency, and is widely used in large and heavy helicopters. At present, most helicopters use C-shaped beam composite blades, and the application of D-shaped beam blades in helicopters is still blank.

[0003] The root of the D-shaped beam blade is a hollow ring structure made of composite materials, and its root configuration is obviously different from that of the traditional C-shaped beam blade. In the fatigue test method, no flap bending moment and edgewise bending moment static load is usually applied during the fatigue test of the root of the C-shaped beam blade, and static load correction is needed to calculate the fatigue performance. However, due to the different root configurations and load forms of the D-shaped beam blade, static load correction may cause excessive equivalent stress and distorted fatigue life calculation results. Therefore, the fatigue test method of the root section of the traditional C-shaped beam blade cannot be completely applied to the fatigue test of the root section of the D-shaped beam blade. SUMMARY

[0004] To solve the technical problem that the fatigue test method of the root section of the traditional C-shaped beam blade cannot be completely applied to the fatigue test of the root section of the D-shaped beam blade, the present application provides a D-shaped beam composite blade root section fatigue test method and system according to the characteristics of the new D-shaped beam blade root configuration. In the fatigue test, flap bending moment and edgewise bending moment static load are applied to determine the fatigue dangerous position and fatigue failure mode of the new configuration D-shaped beam blade root section, and effectively determine the fatigue performance of the D-shaped beam blade root section, providing technical support for blade life estimation and component structure optimization design. The technical solution is as follows:

[0005] In a first aspect, a D-shaped beam composite blade root section fatigue test method is provided, which comprises:

[0006] Step 1: patching and calibration of the D-shaped beam blade root section test piece;

[0007] Step 2: determining the fatigue test static load and dynamic load;

[0008] Step 3: implementing the D-shaped beam blade root section fatigue test.

[0009] Optionally, step 1 comprises:

[0010] Multiple cross sections are pasted near the bushing hole of the test piece, one group of flap strain gauges and one group of edgewise strain gauges are pasted at each cross section, and flap bending moment and edgewise bending moment of the center cross section of the bushing hole are obtained;

[0011] Flap bending moment load calibration and edgewise bending moment load calibration are performed on each cross section of the test piece to meet the fatigue test requirements.

[0012] Optionally, in step two, the size of the fatigue test load parameter is designed according to the first condition and the second condition, the fatigue test load parameter includes static load and dynamic load, and the static load corresponds to centrifugal force, flap bending moment, edgewise bending moment and cycle number, the dynamic load corresponds to centrifugal force, flap bending moment, edgewise bending moment and cycle number,

[0013] The first condition is that the extrusion load P S试验 of the blade root bushing hole under the test static load is 1.1 times the extrusion load P S理论 of the blade root bushing hole under the calculated load, and the extrusion load P S试验 of the blade root bushing hole under the test dynamic load is determined according to the size of the fatigue test load parameter.

[0014] The second condition is that the fatigue performance P∞ meets the blade life index requirement; and the fatigue performance P∞ is calculated according to the extrusion load P d试验 of the blade root bushing hole under the test dynamic load, the extrusion load P d试验 of the blade root bushing hole under the test dynamic load is calculated according to the size of the fatigue test load parameter.

[0015] Optionally, step three includes:

[0016] The blade root clamping and constraint are completed: the test piece blade root support joint is fixed on the test bench, the test piece process joint end is connected with the vibration head, the centrifugal force Fc is applied to the test piece by the horizontal actuator through the steel cable and the vibration head, and the flap bending moment and the edgewise bending moment are realized by the vibration head through the vertical actuator to apply the combined force Fe;

[0017] The flap bending moment dynamic load and the edgewise bending moment dynamic load are applied: the vertical actuator displacement is adjusted, the flap bending moment value is slowly increased to reach the dynamic load flap bending moment requirement value Mbd determined in step two; the fixing bolts of the test bench two ends, i.e. the blade root support joint and the process joint end, are loosened, the test piece is rotated around the axis of the centrifugal force direction, the rotation angle is adjusted so that the edgewise bending moment dynamic load reaches the dynamic load edgewise bending moment requirement value Mtd determined in step two; in order to facilitate subsequent data management and query, the vertical actuator loading displacement at this time can be recorded;

[0018] Apply the flapwise bending moment static load and the edgewise bending moment static load: adjust the vertical actuator displacement to make the flapwise bending moment static load reach the static load flapwise bending moment requirement value Mbs determined in step two; adjust the vertical actuator fixed bolt to generate a horizontal displacement, so that the edgewise bending moment dynamic load reaches the static load edgewise bending moment requirement value Mts determined in step two; for the convenience of subsequent data management and inquiry, the vertical actuator loading displacement at this time can be recorded;

[0019] Perform fatigue test loading: if the test piece does not appear abnormal condition, the test static load is kept unchanged, the dynamic load is increased by 10% to 20%, and the next level load test is performed; if the test piece stiffness decreases by more than 10% in the current test, the original test load is restored, and the test is continued; until the test termination condition is reached, the test termination condition is: the test piece appears serious damage, or the test dynamic load decreases by more than 10% and the load cannot be restored.

[0020] Optionally, in order to further ensure that the safety of the D-shaped beam blade root section after completing the fatigue test meets the actual flight requirements, the application can further implement a residual strength test of the D-shaped beam blade root section, after step three, the method further comprises:

[0021] Step four, implementing a residual strength test of the D-shaped beam blade root section.

[0022] After the fatigue test examination is completed, the residual strength test is performed. The residual strength test load covers the most severe working condition under the flight load, and the application verifies the carrying capacity of the D-shaped beam blade root section under the limit load.

[0023] Optionally, step four includes:

[0024] Designing residual strength test load parameters, the residual strength test load parameters include: centrifugal force Fc, flapwise bending moment Mb 剩余 , edgewise bending moment Mt 剩余 , and cycle number or time:

[0025] The test centrifugal force is loaded to the centrifugal force Fc in increments of not more than 10% of the load value of each level, the test flapwise bending moment is loaded to the flapwise bending moment Mb in increments of not more than 10% of the load value of each level 剩余 , and the test edgewise bending moment is loaded to the edgewise bending moment Mt in increments of not more than 10% of the load value of each level 剩余 .

[0026] Keep the load for 3 seconds, and then unload to 0; unload the centrifugal force Fc to 0, and the test is completed.

[0027] Further, in order to further verify whether the test error of the application meets the preset error requirement, step five can be further executed, and after step four, the method further comprises:

[0028] Step five, analyzing the test error.

[0029] Optionally, step five comprises:

[0030] determining the test control error δ according to the displacement sensor error, the control system error and the loading error C ;

[0031] determining the test measurement error δ according to the measurement system error and the strain gauge calibration error M ;

[0032] judging whether the total test error is not greater than 3% If the total test error is not greater than 3%, the test error meets the preset error requirement.

[0033] Further, in order to further verify the effectiveness of the test result of the application, step six can be further executed, and after step five, the method further comprises:

[0034] Step six, judging the effectiveness of the test result: after the test is completed, the test piece is visually inspected or non-destructive testing, and if there is no crack, the test result is effective.

[0035] In a second aspect, a D-shaped beam composite blade root section fatigue test system is provided for the D-shaped beam composite blade root section fatigue test method of the first aspect, and the system comprises a processor, a test piece, a loading device and a strain gauge,

[0036] The processor is configured to determine the fatigue test static load and the dynamic load.

[0037] The loading device is configured to fix the test piece to facilitate the test.

[0038] The strain gauge is configured to measure the test load.

[0039] The D-shaped beam composite blade root section fatigue test method and system can guide the completion of the new configuration D-shaped beam blade root section fatigue test, determine the fatigue dangerous position and fatigue failure mode of the new configuration D-shaped beam blade root section, and fill the gap in the D-shaped beam blade fatigue test field. Compared with the traditional C-shaped beam blade fatigue test method, the application provides a method of applying a static load of a waving bending moment and a wobbling bending moment in the D-shaped beam blade fatigue test, which covers the theoretical static load through the test static load, solves the problem caused by the static load correction, and can effectively evaluate the fatigue performance of the D-shaped beam blade root section. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1A flowchart of a D-shaped beam composite blade root section fatigue test method provided by an embodiment of the present application is shown in the figure.

[0041] Figure 2 A D-shaped beam blade root section patch diagram provided by an embodiment of the present application is shown in the figure.

[0042] Figure 3 A simulation diagram of a blade fatigue test bed provided by an embodiment of the present application is shown in the figure.

[0043] Figure 4 A test flap vibration bending moment loading diagram provided by an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0044] The present application is further described in detail below through specific embodiments and accompanying drawings.

[0045] An embodiment of the present application provides a D-shaped beam composite blade root section fatigue test method, which includes test piece patching and calibration, determination of test load, determination of test requirements, test implementation, test error analysis, and test effectiveness determination. Figure 1 The method specifically includes the following steps:

[0046] Step 1: Patching and calibration of the D-shaped beam blade root section test piece. Specifically includes:

[0047] 11. Patching is performed on multiple cross sections near the bushing hole of the test piece to obtain the flap bending moment and the vibration bending moment of the cross section at the center of the bushing hole. For example, as shown in the figure, patching is performed on the A, B, and C cross sections at the right end of the bushing hole, and patching is performed on the D cross section at the left end of the bushing hole. One set of flap strain gauges and one set of vibration strain gauges are used for each cross section. The flap bending moment and the vibration bending moment obtained by the flap strain gauges and the vibration strain gauges are interpolated and calculated to obtain the flap bending moment and the vibration bending moment of the cross section at the center of the bushing hole. Figure 2 12. Flap bending moment load calibration and vibration bending moment load calibration are performed on each cross section (A, B, C, and D cross sections) of the test piece. The calibration is performed using the overall calibration method. During calibration, the test piece root support joint is installed on a special calibration table. The standard load is applied to the test piece process joint end through the actuator. The influence of the blade weight is eliminated by vertically placing the test piece and clearing the zero point. The calibration is repeated three times. After calibration, the calibration results of each cross section are linearly verified to meet the fatigue test requirements.

[0048] Step 2: Determine the static load and dynamic load of the fatigue test.

[0049]

[0050] ​Specifically, the magnitude of the fatigue test load parameters is designed according to the first and second conditions. The fatigue test load parameters include static load and dynamic load, as well as the centrifugal force, flapping moment, oscillation moment and number of cycles corresponding to the static load, and the centrifugal force, flapping moment, oscillation moment and number of cycles corresponding to the dynamic load, as shown in Table 1:

[0051] Table 1 Fatigue test loads

[0052] Serial number Test type Centrifugal force (N) Flap bending moment (Nm) Torsional bending moment (Nm) Cycle number 1 Static load Fc Mbs Mts / 2 Dynamic load / Mbd Mtd Ni times per stage

[0053] The first condition is: the compressive load P of the bushing hole at the blade root under the test static load. S试验 The compressive load P generated by the theoretical calculation load S理论 1.1 times, that is, P S试验 =1.1Ps 理论 The compressive load P at the blade root bushing hole under static load was tested. S试验 Determined based on the magnitude of the fatigue test load parameters;

[0054] The second condition is: fatigue performance. P∞ Meets blade life requirements. Fatigue performance. P∞ Based on the compressive load P at the blade root bushing hole under experimental dynamic load. d试验 The calculated compressive load P at the blade root bushing hole under the experimental dynamic load was obtained. d试验 The fatigue performance is calculated based on the magnitude of the fatigue test load parameters. P∞ The calculation formula is as follows:

[0055]

[0056] In the formula, n is the number of dynamic load levels in the test, Ni is the number of load cycles per level, and α is the shape parameter of the SN curve of the composite material.

[0057] Step 3: Conduct fatigue tests on the root section of the D-shaped beam impeller. This specifically includes:

[0058] 31. For example Figure 3 and Figure 4 As shown, the blade root support joint of the test specimen is fixed on the test bench, and the process joint end of the test specimen is connected to the vibrating head. Centrifugal force Fc is applied to the test specimen by a horizontal actuator through a steel cable and the vibrating head; flapping moment and oscillation moment are achieved by a vertical actuator applying a combined force Fe through the vibrating head. This completes the blade root clamping and constraint.

[0059] 32. Apply flapwise bending moment dynamic load and edgewise bending moment dynamic load: adjust the vertical actuator displacement, slowly increase the flapwise bending moment value to reach the dynamic load flapwise bending moment requirement value Mbd determined in step two, see Table 1; loosen the fixing bolts of the test piece at both ends, i.e. the blade root support joint 01 and the process joint end 02, rotate the test piece around the axis of the centrifugal force direction, adjust the rotation angle so that the edgewise bending moment dynamic load reaches the dynamic load edgewise bending moment requirement value Mtd determined in step two, see Table 1; for the convenience of subsequent data management and query, the vertical actuator loading displacement at this time can be recorded;

[0060] 33. Apply flapwise bending moment static load and edgewise bending moment static load: adjust the vertical actuator displacement, so that the flapwise bending moment static load reaches the static load flapwise bending moment requirement value Mbs determined in step two; adjust the fixing bolts of the vertical actuator to produce horizontal displacement, so that the edgewise bending moment dynamic load reaches the static load edgewise bending moment requirement value Mts determined in step two; for the convenience of subsequent data management and query, the vertical actuator loading displacement at this time can be recorded;

[0061] 34. Perform fatigue test loading: if the test piece does not appear cracks, delamination, opening or dynamic load drop more than 10%, etc. after 500,000 cycles of the test, the test static load remains unchanged, the dynamic load increases by 10% to 20%, and the next level of load test is performed; if the stiffness of the test piece decreases by more than 10% during the current test, the original test load needs to be restored, and the test continues; until the test termination condition is reached: the test piece appears serious damage, or the test dynamic load drops more than 10% and the load cannot be restored.

[0062] In another embodiment, in order to further ensure that the safety of the D-shaped beam blade root section after completing the fatigue test meets the actual flight requirements, the present application can further implement the residual strength test of the D-shaped beam blade root section. Further, after step three, the method further comprises:

[0063] Step four, implement the residual strength test of the D-shaped beam blade root section.

[0064] After the fatigue test examination is completed, the residual strength test is performed. The residual strength test load covers the most severe working condition under flight load, and the present application verifies the carrying capacity of the D-shaped beam blade root section under the limit load. Specifically, it includes:

[0065] 41. Design residual strength test load parameters, including: centrifugal force Fc, flapwise bending moment Mb 剩余 , edgewise bending moment Mt 剩余 and cycle number or time, as shown in Table 2:

[0066] Table 2 Residual strength test load

[0067] Serial number Centrifugal force (N) Flap bending moment (Nm) Torsional bending moment (Nm) Cycle number or time 1 Fc Mb 剩余 ]]> Mt 剩余 ]]> Hold for 3 seconds

[0068] 42. The test centrifugal force is loaded in increments of no more than 10% of the load value of each level to the centrifugal force Fc, and the test flapwise bending moment is loaded in increments of no more than 10% of the load value of each level to the flapwise bending moment Mb 剩余 , and the test edgewise bending moment is loaded in increments of no more than 10% of the load value of each level to the edgewise bending moment Mt 剩余

[0069] 43. The load is maintained for 3 seconds, and then unloaded to 0; the centrifugal force Fc is unloaded to 0, and the test is ended.

[0070] In another embodiment, in order to further verify whether the test error of the application meets the preset error requirement, step five can be further executed:

[0071] Step five, analyze the test error. Specifically, it includes:

[0072] 51. Determine the test control error δ according to the displacement sensor error, the control system error and the loading error C

[0073] 52. Determine the test measurement error δ according to the measurement system error and the strain gauge calibration error M

[0074] 53. Calculate the total test error whether it is no more than 3%, if it is no more than 3%, the test error meets the preset error requirement.

[0075] In an embodiment, in order to further verify the effectiveness of the test result of the application, step six can be further executed:

[0076] Step six, determine the effectiveness of the test result.

[0077] After the test is ended, the test piece is visually inspected or non-destructive testing, and if there is no crack, the test result is effective.

[0078] The D-shaped beam composite blade root section fatigue test method provided by the embodiment of the application can guide the completion of the new configuration D-shaped beam blade root section fatigue test, determine the fatigue dangerous position and fatigue failure mode of the new configuration D-shaped beam blade root section, and fill the blank in the field of D-shaped beam blade fatigue test;

[0079] Compared with the traditional C-shaped beam blade fatigue test method, the embodiment of the application provides a method for applying flapwise bending moment and edgewise bending moment static load in the D-shaped beam blade fatigue test, the test static load covers the theoretical static load, the problem caused by static load correction is solved, and the fatigue performance of the D-shaped beam blade root section can be effectively evaluated.

[0080] ​​​The embodiment of the present application also provides a D-shaped beam composite blade root section fatigue test system for the D-shaped beam composite blade root section fatigue test method, the system comprising: a processor, a test piece, a loading device and a strain gauge,

[0081] The processor is used for determining the static load and the dynamic load of the fatigue test.

[0082] The loading device is used for fixing the test piece, facilitating the test.

[0083] The strain gauge is used for measuring the test load.

[0084] The specific working process of the D-shaped beam composite blade root section fatigue test system can refer to the corresponding steps in the foregoing method embodiments, and will not be described here again.

[0085] The above only expresses the embodiments of the present application, and the description is relatively specific and detailed, but should not be understood as a limitation on the patent scope. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. In addition, the parts not described in the present application are all conventional technologies.

Claims

1. A method of fatigue testing a D-Beam composite blade root section, characterized by, The method comprises: Step one, patching and calibration of the D-shaped beam blade root section test piece; Step two, determination of static load and dynamic load for fatigue test; Step three, implementation of D-shaped beam blade root section fatigue test: Complete clamping and constraint of the blade root: fix the blade root support joint of the test piece on the test bench, connect the process joint end of the test piece with the vibration head; centrifugal force Fc is applied to the test piece by the horizontal actuator through the steel cable and the vibration head; edgewise bending moment and flapwise bending moment are realized by the vibration head through the vertical actuator to apply the combined force Fe; Apply edgewise bending moment dynamic load and flapwise bending moment dynamic load: adjust the displacement of the vertical actuator, slowly increase the edgewise bending moment value to the required value Mbd of the dynamic load edgewise bending moment determined in step two; loosen the fixing bolts of the blade root support joint and the process joint end at both ends of the test bench, rotate the test piece around the axis of the centrifugal force, and adjust the rotation angle to make the flapwise bending moment dynamic load reach the required value Mtd of the dynamic load flapwise bending moment determined in step two; Apply edgewise bending moment static load and flapwise bending moment static load: adjust the displacement of the vertical actuator to make the edgewise bending moment static load reach the required value Mbs of the static load edgewise bending moment determined in step two; adjust the horizontal displacement of the fixing bolt of the vertical actuator to make the flapwise bending moment dynamic load reach the required value Mts of the static load flapwise bending moment determined in step two; Perform fatigue test loading: if the test piece does not have abnormal conditions after a plurality of cycles of the test, keep the test static load unchanged, increase the dynamic load by 10% to 20%, and perform the next level of load test; if the stiffness of the test piece decreases by more than 10% in the current level of test, restore to the original test load and continue the test; until the test termination condition is reached, the test termination condition is that the test piece has serious damage, or the test dynamic load decreases by more than 10% and the load cannot be restored.

2. The method of claim 1, wherein, Step one comprises: Patch the test piece at multiple cross sections near the bushing hole, and for each cross section, one group of edgewise strain gauges and one group of flapwise strain gauges are used to obtain the edgewise bending moment and the flapwise bending moment of the center cross section of the bushing hole; Edgewise bending moment load calibration and flapwise bending moment load calibration are performed on each cross section of the test piece to meet the requirements of the fatigue test.

3. The method of claim 1, wherein, In step two, the size of the fatigue test load parameters, including static load and dynamic load, and the centrifugal force, edgewise bending moment, flapwise bending moment and cycle number corresponding to the static load, and the centrifugal force, edgewise bending moment, flapwise bending moment and cycle number corresponding to the dynamic load, are designed according to the first condition and the second condition. Wherein, the first condition is: the extrusion load P of the blade root bushing hole under the test static load S试验 The extrusion load P generated by the theoretical calculation load is 1.1 times the extrusion load P of the blade root bushing hole under the test static load S理论 The extrusion load P generated by the theoretical calculation load is 1.1 times the extrusion load P of the blade root bushing hole under the test static load S试验 According to the size of the fatigue test load parameter The second condition is: fatigue performance P ∞ The second condition is: fatigue performance P ∞ According to the extrusion load P of the blade root bush hole under the test dynamic load d试验 According to the extrusion load P of the blade root bush hole under the test dynamic load d试验 According to the size of the fatigue test load parameter 4. The method of claim 1, wherein, After step three, the method further comprises: Step four, implementation of D-shaped beam blade root section residual strength test.

5. The method of claim 4, wherein, Step four comprises: designing a residual strength test load parameter, the residual strength test load parameter comprising: a centrifugal force Fc, an edgewise bending moment Mb 剩余 , a flapwise bending moment Mt 剩余 and a number of cycles or time: The test centrifugal force is loaded to the centrifugal force Fc in increments of not more than 10% of the load value per stage, and the test flap bending moment is loaded to the flap bending moment Mb in increments of not more than 10% of the load value per stage 剩余 , and the test roll bending moment is loaded to the roll bending moment Mt in increments of not more than 10% of the load value per stage 剩余 . Hold the load for 3 seconds and then unload to 0; unload the centrifugal force Fc to 0, and the test is completed.

6. The method of claim 4, wherein, After step four, the method further comprises: Step five, analysis of test error.

7. The method of claim 6, wherein, Step five comprises: According to the displacement sensor error, the control system error, and the loading error, the test control error δ is determined C ; According to the measurement system error, the strain gauge calibration error, the test measurement error δ is determined M ; determining whether the total error of the test is not greater than 3% whether the total error of the test is not greater than 3%, and if the total error of the test is not greater than 3%, the test error satisfies the preset error requirement.

8. The method of claim 6, wherein, After step five, the method further comprises: Step six, determination of the validity of the test results: after the test is completed, visually inspect or non-destructive testing the test piece, and if there is no crack, the test results are valid.

9. A D-Beam composite blade root section fatigue test system, characterized by, The system for the D-shaped beam composite material paddle root section fatigue test method according to any one of claims 1 to 8 comprises a processor, a test piece, a loading device and a strain gauge. The processor is configured to determine a static load and a dynamic load of the fatigue test. The loading device is configured to fix the test piece and facilitate the test. The strain gauge is configured to measure the test load.

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