Method and device for testing fatigue life of riveting hole of aircraft rear flap

Abstract

The invention discloses a method and a device for testing the fatigue life of a riveting hole of an aircraft rear flap. The method comprises the following steps: firstly, circularly simulating a flight simulation experiment of an airplane in an extreme environment until an overall evaluation factor of a pair of riveting holes in each riveting hole group in a wing plate and a connecting plate in a middle area of a rear flap is greater than a preset value, and obtaining the cycle index in the extreme environment; next, a new rear flap is replaced, the flight simulation experiment of the airplane in the normal environment is cyclically simulated until the overall evaluation factor of one pair of riveting holes is larger than the maximum overall evaluation factor value after the flight simulation experiment under the first limit condition, and the number of cycles in the normal environment with the result equal to that of one cycle in the limit environment is obtained; therefore, the fatigue life of the riveting hole in the rear flap in the normal environment is obtained. Compared with an existing method for testing the fatigue life of the riveting hole in the rear flap, the testing cycle frequency is reduced, the testing time is shortened, and the testing efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of wing performance detection, and particularly relates to a fatigue life test method for riveting holes of an aircraft trailing flap. Background Art

[0002] The trailing flap is a movable wing surface installed at the trailing edge of the wing, which plays a role in increasing lift. The life of the trailing flap has an important impact on the life of the entire wing. It adopts a riveting connection method, and the riveting holes are often the stress concentration points of the entire trailing flap. Therefore, the fatigue life of the trailing flap depends on the fatigue life of the riveting holes. However, there are problems in the current fatigue life test of the riveting holes, such as a large number of test cycles, a long single detection time, and a complex process. Therefore, it is necessary to design a fatigue life test method for the riveting holes of an aircraft trailing flap that is simple in process and can shorten the test cycle times and detection time. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and propose a fatigue life test method and test device for riveting holes of an aircraft trailing flap.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A fatigue life test method for riveting holes of an aircraft trailing flap of the present invention is as follows:

[0006] Step 1: Clamp both ends of the simulated wing in the simulated wing assembly with two horizontally symmetric wing clamps. In the simulated wing assembly, the trailing flap is synchronously driven to extend or retract by two driving components located at both ends of the trailing edge of the simulated wing; every two adjacent wing plates on the trailing flap are riveted through a connecting plate and rivets, and there are multiple connecting positions between the two wing plates and the connecting plate. A pair of riveting hole groups are provided in a facing manner at each connecting position. The riveting hole group is composed of a riveting hole opened on the wing plate and a riveting hole opened on the connecting plate. The two riveting holes of each riveting hole group are connected by a rivet; multiple groups of strain gauge groups are evenly distributed along the circumferential direction on each rivet. The strain gauge group is composed of multiple strain gauges arranged at equal distances; in the initial state, the trailing flap is in a retracted state; place the simulated wing assembly in the test chamber.

[0007] Step 2: Set the takeoff time, flight time, and landing time during the flight simulation experiment, and set the temperature in the test chamber during the takeoff period, flight period, and landing period, as well as the flow rate of a single precipitation and rain shower nozzle; among them, the temperature in the test chamber is adjusted by passing a liquid through the circulation pipe for cooling or heating by a heater, and is detected by a temperature sensor.

[0008] Step 3: The blower at the opening of the test chamber operates, and the blower wind speed is increased until the extrusion force measured by one strain gauge causes the corresponding riveting hole to reach the yield limit, then a flight simulation experiment is carried out: Simulate the flight process of an aircraft from takeoff to flight and then to landing, and the trailing edge flaps extend during the takeoff period and the landing period, and the trailing edge flaps retract during the flight period; and while the flight simulation experiment is carried out, the temperature in the test chamber is maintained at the set temperature, and each water spray and rain shower nozzle sprays water at the set flow rate.

[0009] Step 4: After the flight simulation experiment is completed, the blower, the circulation pipe, the heater, and the precipitation and rain shower nozzles stop working, the trailing edge flaps retract to the initial state, the wing plates and connecting plates in the middle area of the trailing edge flaps are removed, and each rivet on these wing plates and connecting plates is removed, the contact positions of the two riveting holes in each riveting hole group are detected, and then these wing plates, connecting plates, and each rivet are installed back in place.

[0010] Step 5: Calculate the roundness defect evaluation factor and the crack evaluation factor of the contact positions of the two riveting holes in each riveting hole group on these wing plates and connecting plates, and then calculate the overall evaluation factor of the two riveting holes in each riveting hole group.

[0011] Step 6: Record the maximum value S0 of the overall evaluation factors of the two riveting holes corresponding to each riveting hole group on the wing plates and connecting plates in the middle area after a flight simulation experiment when a riveting hole reaches the yield limit, and then repeat Steps 3 to 5 until the overall evaluation factor of the two riveting holes corresponding to one of the riveting hole groups on the wing plates and connecting plates in the middle area is greater than the preset value, and obtain the number of cycles n of the flight simulation experiment at this time.

[0012] Step 7: Replace the new trailing edge flap, repeat Steps 3 to 5, and during the repetition process, the blower operates so that the extrusion force measured by one strain gauge causes the corresponding riveting hole to reach half of the yield limit; until the overall evaluation factor of the riveting holes corresponding to one of the riveting hole groups on the wing plates and connecting plates in the middle area is greater than S0, and then obtain the number of cycles p of the flight simulation experiment, and then calculate the fatigue life m of the riveting holes on the trailing edge flap when a riveting hole reaches half of the yield limit as m = (n - 1)·p.

[0013] Preferably, after the two wing fixing clamps clamp the simulated wings, adjust each wing fixing clamp to drive the simulated wing assembly to move downward so that the simulated wings contact the support plate in the test chamber and are supported on the support plate.

[0014] Preferably, there is a group of strain gauges on each rivet on the side far from the blower.

[0015] Preferably, the extrusion force F received by the riveting hole under the yield limit is

[0016] F = σ S ·A = σS ·h·d0

[0017] In the formula, σ S is the yield limit stress of the rear flap material; A is the longitudinal cross-sectional area of the rivet hole passing through the central axis; h is the depth of the rivet hole; d0 is the initial diameter of the rivet hole.

[0018] Preferably, in step four, detecting the contact position of two rivet holes in each rivet hole group specifically refers to detecting the area of the contact position of the two rivet holes, the maximum curvature radius of the contact position of the two rivet holes, the minimum curvature radius of the contact position of the two rivet holes, the center offset of the contact position of the two rivet holes, the length of each crack at the contact position of the two rivet holes, and the maximum width.

[0019] More preferably, the roundness defect evaluation factor of the contact position of two rivet holes in each rivet hole group in step five is

[0020]

[0021] In the formula, A 上 , S 上 , R 上max and R 上min are respectively the roundness defect evaluation factor, area, maximum curvature radius, and minimum curvature radius of the rivet hole of the wing plate at the contact position with the rivet hole of the connecting plate, A 下 , S 下 , R 下max and R 下min are respectively the roundness defect evaluation factor, area, maximum curvature radius, and minimum curvature radius of the rivet hole of the connecting plate at the contact position with the rivet hole of the wing plate; S 初始 is the initial cross-sectional area of the rivet hole of the wing plate or the connecting plate;

[0022] The crack evaluation factor of the contact position of two rivet holes in each rivet hole group is

[0023]

[0024] In the formula, B is the crack evaluation factor of the contact position of two rivet holes, l i is the length of the i-th crack, a i is the maximum width of the i-th crack, b is the total number of cracks at the contact position of two rivet holes; h is the depth of the rivet hole; d0 is the initial diameter of the rivet hole;

[0025] The overall evaluation factor of two rivet holes in each rivet hole group is

[0026]

[0027] In the formula, L 上L is the center offset of the riveting hole of the wing plate before and after the flight simulation experiment at the contact position with the riveting hole of the connecting plate. 下 It is the center offset of the riveting hole of the connecting plate before and after the flight simulation experiment at the contact position with the riveting hole of the wing plate.

[0028] A fatigue life test device for riveting holes of an aircraft rear flap of the present invention includes a frame, a wing fixing assembly, an environment control assembly, multiple groups of piezoresistive chip groups and a test chamber. The piezoresistive chip group is composed of multiple piezoresistive chips arranged at equal intervals. The environment control assembly includes a blower assembly, a temperature control assembly and a rain shower assembly.

[0029] The wing fixing assembly includes a wing fixing clamp, a support plate, a support frame and a mounting plate. The test chamber is fixed on the frame, and openings are provided at both ends of the test chamber; one end of the horizontally arranged mounting plate passes through one of the openings and penetrates into the test chamber, and is fixed to the bottom plate of the test chamber through a column, and the other end is fixed to the frame, and there is a gap between the lower surface of the mounting plate and the bottom plate; the support frame is fixed to the bottom plate; two symmetrically arranged wing fixing clamps are detachably fixed on both sides of the support frame and are located on both sides of the mounting plate. The blower assembly includes a motor and a blower. The blower is fixed at one end of the mounting plate outside the test chamber and is driven by the motor. The motor is controlled by a controller, and the air outlet of the blower faces the opening of the test chamber. The temperature control assembly includes a circulation pipe, and the circulation pipe is fixed on the lower surface of the mounting plate and is located between the bottom plate and the mounting plate; a rain shower assembly is fixed above the mounting plate on the support frame, and the rain shower assembly is composed of a plurality of precipitation rain shower nozzles arranged in an array.

[0030] Preferably, a horizontally arranged support plate is fixed on the mounting plate through a connecting frame, and the support plate is located directly below the rain shower assembly; the wing fixing clamp is fixed on the support frame through bolts and nuts.

[0031] Preferably, the blower includes a volute, a collector and an impeller. The volute is fixed on the mounting plate, the impeller is arranged in the volute, forms a rotating pair with the volute, and is driven by the motor to rotate. The air inlet of the volute is fixed to the collector, and the air outlet of the volute faces the opening.

[0032] More preferably, the housing of the motor is fixed on the frame, and the output shaft is connected to the impeller through a belt drive mechanism.

[0033] The present invention has the following beneficial effects:

[0034] 1. The present invention can conveniently implement the fatigue life test of the riveted holes of the rear flap of the aircraft, and has a high test efficiency. Specifically, the present invention uses a blower to make the extrusion pressure on the riveted holes on the rear flap make the corresponding riveted holes reach the yield limit, and conducts a flight simulation experiment to simulate the flight conditions of the aircraft under extreme environments. Then, each riveted hole group on the wing panel and the connecting plate in the middle area of ​​the rear flap is detected, and the overall evaluation factor of the two riveted holes in each riveted hole group is calculated based on the detected data, and then the above steps are repeated until the overall evaluation factor of the two riveted holes in one of the riveted hole groups is greater than the preset value, thereby obtaining the number of cycles under extreme environments. Furthermore, the present invention replaces a new rear flap, uses a blower to make the extrusion pressure on the riveted holes on the rear flap make the corresponding riveted holes reach half of the yield limit, and conducts a flight simulation experiment to simulate the flight conditions of the aircraft under normal environments. Then, each riveted hole group on the wing panel and the connecting plate in the middle area of ​​the rear flap is tested. The rivet hole groups are tested, and the overall evaluation factors of the two rivet holes in each rivet hole group are calculated according to the detected data, and then the above steps are repeated until the overall evaluation factor of the two rivet holes in one of the rivet hole groups is greater than the maximum value of the overall evaluation factors of the two rivet holes in each rivet hole group after the first flight simulation experiment under the extreme condition, thereby obtaining the number of cycles under normal conditions that have the same result as one cycle under the extreme condition, and calculating the fatigue life of the rivet holes on the rear flap under normal conditions according to the number of cycles under the extreme condition and the number of cycles under normal conditions that have the same result as one cycle under the extreme condition, thereby realizing the detection of the fatigue life of the rivet holes on the rear flap of the aircraft, and compared with the existing method for testing the fatigue life of the rivet holes on the rear flap, the number of test cycles is reduced, the test time is shortened, and the test efficiency is improved.

[0035] 2. The overall evaluation factor for the two riveted holes in each riveted hole group of the rear flap established in the present invention takes into account the roundness and center offset of the riveted hole contact surface and the influence of cracks on their fatigue life, thereby improving the accuracy of the fatigue life test of the riveted holes of the rear flap; wherein, the present invention adopts a machine vision recognition method to detect the morphology and cracks of the riveted hole contact surface, which has high detection accuracy, and adopts the ratio of the crack volume to the original radius of the riveted hole to realize the evaluation of the crack, which reflects the influence of the riveted hole depth on the crack propagation, and can more accurately measure the crack damage of the riveted hole. Furthermore, considering that the CF / PEEK material is a plastic material with a small elastic modulus, the deformation of the circular hole will not become an elliptical hole when subjected to force, but will form an irregular hole. The roundness of the riveted hole is detected by a metrological method, and a correction coefficient related to the ratio of the area before and after the deformation of the riveted hole contact position is introduced, thereby improving the accuracy of the detection data and further improving the accuracy of the fatigue life test of the riveted hole of the rear flap.

[0036] 3. When conducting flight simulation experiments in the present invention, the trailing flap is extended or retracted by driving components that simulate the wings, so as to achieve the angle changes of the trailing flap during takeoff, steady flight, and landing in the process of simulating aircraft flight. Different temperatures of water are circulated through the circulation pipe to set different temperatures in the test chamber at different stages of takeoff, steady flight, and landing, so as to achieve the environment of temperature change in the process of simulating aircraft flight. Water is sprayed through each precipitation and rain shower nozzle to achieve the environment affected by water vapor when simulating the aircraft flying through clouds during flight. Furthermore, the simulation of the force angle and environmental changes of the trailing flap during aircraft flight is realized, making the test results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic structural diagram of the present invention after removing the frame;

[0038] Figure 2 is Figure 1 a schematic structural diagram of the structure after removing the test chamber and installing the simulated wing assembly;

[0039] Figure 3 is Figure 2 a schematic structural diagram of the structure after removing the blower assembly in

[0040] Figure 4 is a schematic structural diagram of the blower assembly in the present invention;

[0041] Figure 5 is a schematic structural diagram of the support frame, mounting plate, temperature control component, and rain shower component in the present invention;

[0042] Figure 6 is a schematic structural diagram of the simulated wing;

[0043] Figure 7 is a schematic structural diagram of the simulated wing assembly in the retracted state;

[0044] Figure 8 is Figure 7 the front view of

[0045] Figure 9 is a schematic structural diagram of the simulated wing assembly in the extended state;

[0046] Figure 10 is Figure 9 the front view of

[0047] Figure 11 is a schematic structural diagram of two adjacent wing plates on the surface of the trailing flap;

[0048] Figure 12 is a schematic structural diagram of multiple groups of piezoresistive element groups arranged on the rivets of the trailing flap. DETAILED DESCRIPTION OF THE INVENTION

[0049] The present invention will be further described below in conjunction with the accompanying drawings.

[0050] As Figure 1 and Figure 2 shown, a fatigue life test device for riveting holes of an aircraft trailing flap according to the present invention includes a frame (not shown in the figure), a wing fixing assembly 101, an environment control assembly, multiple groups of piezoresistive element groups, and a test chamber 104. The piezoresistive element group is composed of multiple piezoresistive elements (pressure strain gauges) 602 arranged at equal intervals. The environment control assembly includes a blower assembly 102, a temperature control assembly, and a rain shower assembly 103.

[0051] As Figure 3 shown, the wing fixing assembly 101 includes a wing fixing clamp 201, a support plate, a support frame 203, and a mounting plate 204. The test chamber 104 is fixed to the frame, and openings are provided at both ends of the test chamber 104; one end of the horizontally arranged mounting plate 204 passes through one of the openings, penetrates into the test chamber 104, and is fixed to the bottom plate of the test chamber 104 through a column, and the other end is fixed to the frame. There is a gap between the lower surface of the mounting plate 204 and the bottom plate; the horizontally arranged support plate is fixed to the mounting plate 204 through a connecting frame 202 and is located inside the test chamber 104, and the support frame 203 is fixed to the bottom plate; two symmetrically arranged wing fixing clamps 201 are fixed to both sides of the support frame 203 through bolts and nuts and are located on both sides of the support plate. By loosening each bolt and each nut, the height of each wing fixing clamp 201 can be adjusted to facilitate adjusting the height of the simulated wing 501 so that the simulated wing 501 is supported on the support plate to ensure the stability of the simulated wing 501.

[0052] As Figure 4 shown, the blower assembly 102 includes a motor 301 and a blower. The blower is fixed to one end of the mounting plate 204 located outside the test chamber 104 and is driven by the motor 301. The motor 301 is controlled by a controller, and the air outlet of the blower faces the opening of the test chamber 104. As Figure 5 shown, the temperature control assembly includes a circulation pipe 401. The circulation pipe 401 is fixed to the lower surface of the mounting plate 204 and is located between the bottom plate and the mounting plate 204. By circulating liquids at different temperatures through the circulation pipe 401, the temperature inside the test chamber 104 can be changed; a rain shower assembly 103 is fixed above the support plate on the support frame 203. The rain shower assembly 103 is composed of a plurality of precipitation rain shower nozzles 402 arranged in an array for simulating a rainfall environment.

[0053] As a preferred embodiment, the blower includes a volute 302, an air collector 303, and an impeller 304. The volute 302 is fixed to the mounting plate 204. The impeller 304 is disposed inside the volute 302, forms a rotating pair with the volute 302, and is driven to rotate by the motor 301. The air inlet of the volute 302 is fixed to the air collector 303, and the air outlet of the volute 302 faces the opening.

[0054] More preferably, the housing of the motor 301 is fixed to the frame, and the output shaft is connected to the impeller 304 through a belt drive mechanism.

[0055] A fatigue life test method for riveting holes of the rear flap of an aircraft according to the present invention is as follows:

[0056] Step 1: Directly connect the outlet of the circulation pipe 401 to the first water tank, and connect the inlet to the first water tank through the first water pump. A temperature sensor and a heater are provided in the first water tank, and it is connected to a liquid nitrogen tank. The temperature of the liquid in the first water tank can be detected in real time through the temperature sensor, the liquid in the first water tank can be heated through the heater, and the liquid in the first water tank can be cooled by the liquid nitrogen tank; connect the inlets of the respective precipitation and rain shower nozzles 402 to the second water tank through the second water pump; then clamp the simulated wing assembly, so that the two wing fixing clamps 201 hold both ends of the simulated wing 501 in the simulated wing assembly. Two driving assemblies 502 are symmetrically arranged at both ends of the trailing edge of the simulated wing 501 away from the blower. The rear flap is detachably installed on the two driving assemblies 502 and is synchronously driven by the two driving assemblies 502 to extend (lower, the angle with the simulated wing 501 becomes larger) or retract (turn up, the angle with the simulated wing 501 becomes smaller), as Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 and Figure 10 shown, Figure 6 The plate with the trailing edge of the simulated wing 501 warped upwards in is a spoiler for increasing resistance; in the initial state, the rear flap is in the retracted state; among them, as Figure 11 and Figure 12As shown in the figure, every two adjacent wing plates on the rear flap are connected by a connecting plate and rivets 601, and there are multiple connection positions between the two wing plates and the connecting plate. A pair of riveting hole groups are provided at each connection position, and the riveting hole groups are composed of a riveting hole opened on the wing plate and a riveting hole opened on the connecting plate. The two riveting holes of each riveting hole group are connected by a rivet 601. Each wing plate is made of CF / PEEK material, and multiple groups of strain gauges are evenly distributed along the circumference on each rivet 601. The strain gauges 602 in the strain gauge group are used to measure the extrusion force received by the riveting holes, and one of the groups of strain gauges on each rivet 601 is located on the side of the corresponding rivet 601 away from the blower, so as to more accurately measure the extrusion force received by each riveting hole. Then loosen each bolt and each nut, and manually adjust each wing fixing clamp 201 to drive the simulated wing assembly to move downward, so that the simulated wing 501 contacts the support plate and is supported on the support plate.

[0057] Step 2: Set the takeoff time, flight time, and landing time during the flight simulation experiment, and set the temperature during the takeoff period, flight period, and landing period, as well as the flow rate of a single precipitation shower nozzle 402. In this embodiment, the total time of the flight simulation experiment is set to 6 minutes, the takeoff time, flight time, and landing time are all 2 minutes, the temperature during the takeoff period is 150 °C, the temperature during the flight period is -50 °C, the temperature during the landing period is 0 °C, and the flow rate of a single precipitation shower nozzle 402 is 4 L / h.

[0058] Step 3: The controller controls the motor to drive the blower to work, and when the wind speed of the blower increases to the extrusion force measured by a strain gauge that makes the corresponding riveting hole reach the yield limit, keep the wind speed at this time, so as to simulate the stress condition of the riveting holes on the flap during flight at the yield limit (extreme environment). Then conduct the flight simulation experiment: simulate the flight process of the aircraft from takeoff to stable flight and then to landing. During the simulated takeoff period, the two drive components 502 drive the rear flap to extend synchronously to simulate the takeoff state of the aircraft. During the stable flight period, the two drive components 502 drive the rear flap to retract synchronously. During the landing period, the two drive components 502 drive the rear flap to extend synchronously to simulate the landing state of the aircraft. And while conducting the flight simulation experiment, the water pump 1 works to continuously transport the liquid at the set temperature in the water tank 1 to the circulation pipe 401, so that the temperature in the test chamber changes according to the set temperature. The water pump 2 works to transport the water in the water tank 2 to each spray shower nozzle 402, so that each spray shower nozzle 402 sprays water at the set flow rate. Among them, the extrusion force F received by the riveting hole at the yield limit is

[0059] F = σ S ·A = σ S ·h·d0

[0060] In the formula, σ Sis the yield stress of the rear flap material; A is the longitudinal cross-sectional area of ​​the rivet hole through the center axis; h is the depth of the rivet hole; d0 is the initial diameter of the rivet hole.

[0061] Step 4: After completing a flight simulation experiment, the two drive assemblies 502 synchronously drive the rear flap to retract to the initial state, remove the wing panels and connecting plates in the middle area of ​​the rear flap, and remove the rivets on these wing panels and connecting plates. Use machine vision recognition methods to detect each riveting hole group on these wing panels and connecting plates (the wing panels and connecting plates in the middle of the rear flap are subject to the largest extrusion pressure) to obtain the following detection data for each riveting hole group: the area of ​​the contact positions of the two rivet holes in each rivet hole group, the maximum curvature radius of the contact positions of the two rivet holes, the minimum curvature radius of the contact positions of the two rivet holes, the center offset of the contact positions of the two rivet holes, the length and maximum width of each crack at the contact positions of the two rivet holes; then install the wing panels and connecting plates in the middle area and the rivets back to their original positions.

[0062] Step 5: Analyze the inspection data of each riveting hole group on the wing plate and the connecting plate in the middle area: First, use the measurement method to analyze the roundness defect of the contact position of the two riveting holes, that is, calculate the roundness defect evaluation factor of the contact position of the two riveting holes

[0063]

[0064] In the formula, A 上 , S 上 , R 上max and R 上min They are the roundness defect evaluation factor, area, maximum curvature radius and minimum curvature radius of the rivet hole of the wing plate at the contact position with the rivet hole of the connecting plate, A 下 , S 下 , R 下max and R 下min They are the roundness defect evaluation factor, area, maximum curvature radius and minimum curvature radius of the riveting hole of the connecting plate at the contact position with the riveting hole of the wing plate; S 初始 is the initial cross-sectional area of ​​the riveting hole of the wing plate or the connecting plate; wherein, considering that CF / PEEK material is a plastic material with a small elastic modulus, the circular hole will not become an elliptical hole when subjected to force, but will form an irregular hole. The ratio of the areas before and after the deformation of the contact position of the riveted hole of the CF / PEEK material has an important influence on the accurate evaluation of the roundness defect of the riveted hole. Therefore, a correction coefficient related to the ratio of the areas before and after the deformation of the contact position of the riveted hole of the CF / PEEK material is introduced into the roundness defect evaluation factor of the contact position of the riveted hole of the CF / PEEK material.

[0065] Then the crack defect at the contact position of the two riveted holes is analyzed, and the crack evaluation factor at the contact position of the two riveted holes is calculated as follows:

[0066]

[0067] In the formula, B is the crack evaluation factor at the contact position of the two rivet holes, and l i is the length of the i-th crack, and a i is the maximum width of the i-th crack, and b is the total number of cracks at the contact position of the two rivet holes; among them, the depth and radius of the rivet holes are closely related to the generation and propagation of cracks. Therefore, the ratio of the depth to the radius of the rivet holes is introduced as a correction coefficient in the crack evaluation factor at the contact position of the two rivet holes.

[0068] Then, the overall evaluation of the two rivet holes is carried out, and the overall evaluation factor of the two rivet holes is calculated as

[0069]

[0070] In the formula, L 上 is the center offset of the rivet hole on the wing panel at the contact position with the rivet hole on the connecting plate before and after the flight simulation experiment, and L 下 is the center offset of the rivet hole on the connecting plate at the contact position with the rivet hole on the wing panel before and after the flight simulation experiment.

[0071] Step Six: Record the maximum value S0 of the overall evaluation factors of the two rivet holes corresponding to each rivet hole group on the wing panel and the connecting plate in the middle area after a flight simulation experiment when a rivet hole reaches the yield limit. Then repeat Steps Three to Five until the overall evaluation factor of the two rivet holes corresponding to one of the rivet hole groups on the wing panel and the connecting plate in the middle area is greater than the preset value, and obtain the number of cycles n of the flight simulation experiment at this time.

[0072] Step Seven: Replace the new rear flap, and repeat Steps Three to Five. During the repetition process, the blower works so that the extrusion force measured by one of the piezoresistive chips makes the corresponding rivet hole reach half of the yield limit, thereby simulating the stress condition of the rivet holes on the rear flap during flight in a normal environment until the overall evaluation factor of the rivet holes corresponding to one of the rivet hole groups on the wing panel and the connecting plate in the middle area is greater than S0, and then obtain the number of cycles p of the flight simulation experiment when a rivet hole reaches half of the yield limit (in a normal environment) that has the same result as a flight simulation experiment when a rivet hole reaches the yield limit. In this embodiment, p = 170; then calculate the number of cycles m of the flight simulation experiment when a rivet hole reaches half of the yield limit, that is, the fatigue life of the rivet holes on the rear flap when a rivet hole reaches half of the yield limit is

[0073] m=(n - 1)·p

[0074] Among them, according to the number of flight simulation experiment cycles \(n\) obtained in Step 6, it can be known that when a rivet hole reaches the yield limit, the rivet holes on the trailing flap will not show fatigue failure after \(n - 1\) flight simulation experiments, but will show fatigue failure after \(n\) flight simulation experiments. Therefore, when calculating \(m\), it should be multiplied by \(n - 1\) and \(p\).

Claims

1. A fatigue life test method for the riveting holes of an aircraft's trailing flap, characterized in that: The details are as follows: Step 1: Clamp both ends of the simulated wing in the simulated wing assembly with two horizontally symmetric wing clamps. The trailing flap in the simulated wing assembly is synchronously driven by two drive assemblies located at both ends of the trailing edge of the simulated wing to extend or retract. Each adjacent pair of wing plates on the trailing flap is riveted through a connecting plate and rivets, and there are multiple connection positions between the two wing plates and the connecting plate. A pair of riveting hole groups are provided in a facing manner at each connection position. The riveting hole group is composed of a riveting hole opened on the wing plate and a riveting hole opened on the connecting plate. The two riveting holes of each riveting hole group are connected by a rivet. Multiple groups of strain gauge groups are evenly distributed along the circumferential direction on each rivet. The strain gauge group is composed of multiple strain gauges arranged at equal intervals. In the initial state, the trailing flap is in the retracted state. Place the simulated wing assembly in the test chamber. Step 2: Set the takeoff time, flight time, and landing time during the flight simulation experiment, and set the temperature in the test chamber during the takeoff period, flight period, and landing period, as well as the flow rate of a single precipitation sprinkler. The temperature in the test chamber is adjusted by passing a liquid through the circulation pipe for cooling or by heating with a heater, and is detected by a temperature sensor. Step 3: The blower at the opening of the test chamber operates, and when the wind speed of the blower increases to the extrusion force measured by one strain gauge causing the corresponding riveting hole to reach the yield limit, conduct the flight simulation experiment: Simulate the flight process of the aircraft from takeoff to flight and then to landing, with the trailing flap extending during the takeoff period and landing period and retracting during the flight period. While conducting the flight simulation experiment, maintain the temperature in the test chamber at the set temperature, and each water spray sprinkler sprays water at the set flow rate. Step 4: After completing the flight simulation experiment, stop the blower, circulation pipe, heater, and precipitation sprinkler. Retract the trailing flap to the initial state. Remove the wing plates and connecting plates in the middle area of the trailing flap, and remove each rivet on these wing plates and connecting plates. Detect the contact position of the two riveting holes in each riveting hole group, and then install these wing plates, connecting plates, and each rivet back to their original positions. Step 5: Calculate the roundness defect evaluation factor and crack evaluation factor for the contact position of the two riveting holes in each riveting hole group on these wing plates and connecting plates, and then calculate the overall evaluation factor for the two riveting holes in each riveting hole group. Step 6: Record the maximum value S0 of the overall evaluation factors of the two riveting holes corresponding to each riveting hole group on the wing plates and connecting plates in the middle area after a flight simulation experiment when a riveting hole reaches the yield limit. Then repeat Steps 3 to 5 until the overall evaluation factor of the two riveting holes corresponding to one of the riveting hole groups on the wing plates and connecting plates in the middle area is greater than the preset value, and obtain the number of cycles n of the flight simulation experiment at this time. Step 7: Replace the rear flap with a new one and repeat Steps 3 to 5. During the repetition, the blower operates so that the extrusion force measured by one of the strain gauges causes the corresponding rivet hole to reach half of the yield limit. Continue until the overall evaluation factor of the rivet holes corresponding to one of the rivet hole groups on the wing plate and the connecting plate in the middle area is greater than S0, thereby obtaining the number of flight simulation experiment cycles p. Then calculate the fatigue life m of the rivet holes on the rear flap when a rivet hole reaches half of the yield limit, where m = (n - 1)·p.

2. The fatigue life test method for the riveting holes of the rear flap of an aircraft according to claim 1, characterized in that: After the two wing fixing clamps hold the simulated wing, adjust each wing fixing clamp to drive the simulated wing assembly downward so that the simulated wing contacts the support plate in the test chamber and is supported on the support plate.

3. A fatigue life test method for riveting holes of an aircraft trailing flap according to claim 1, characterized in that: There is a set of strain gauge groups on each rivet on the side away from the blower.

4. A fatigue life test method for riveting holes of an aircraft trailing flap according to claim 1, characterized in that: The extrusion force F received by the rivet hole under the yield limit is F = σ S ·A = σ S ·h·d0 where σ S is the yield limit stress of the rear flap material; A is the longitudinal cross-sectional area of the rivet hole passing through the central axis; h is the depth of the rivet hole; and d0 is the initial diameter of the rivet hole.

5. A fatigue life test method for the riveting holes of an aircraft trailing flap according to claim 1, characterized in that: In Step 4, the specific detection of the contact position of the two rivet holes in each rivet hole group is to detect the area of the contact position of the two rivet holes, the maximum curvature radius of the contact position of the two rivet holes, the minimum curvature radius of the contact position of the two rivet holes, the center offset of the contact position of the two rivet holes, the length and maximum width of each crack at the contact position of the two rivet holes.

6. A fatigue life test method for riveting holes of an aircraft trailing flap according to claim 5, characterized in that: The roundness defect evaluation factor of the contact position of the two rivet holes in each rivet hole group in Step 5 is Where, A 上 , S 上 , R 上max and R 上min are respectively the roundness defect evaluation factor, area, maximum curvature radius and minimum curvature radius of the riveting hole of the wing plate at the contact position with the riveting hole of the connecting plate. A 下 , S 下 , R 下max and R 下min are respectively the roundness defect evaluation factor, area, maximum curvature radius and minimum curvature radius of the riveting hole of the connecting plate at the contact position with the riveting hole of the wing plate; S 初始 is the initial cross-sectional area of the riveting hole of the wing plate or the connecting plate; The crack evaluation factor of the contact position of the two rivet holes in each rivet hole group is Where B is the crack evaluation factor at the contact position of two riveting holes, l i is the length of the i-th crack, a i is the maximum width of the i-th crack, b is the total number of cracks at the contact position of two riveting holes; h is the depth of the riveting hole; d0 is the initial diameter of the riveting hole; The overall evaluation factor of the two rivet holes in each rivet hole group is where L 上 is the center offset of the riveting hole of the wing plate before and after the flight simulation experiment at the contact position with the riveting hole of the connecting plate, and L 下 is the center offset of the riveting hole of the connecting plate before and after the flight simulation experiment at the contact position with the riveting hole of the wing plate.

7. A test device used for the fatigue life test method of the riveting holes of an aircraft trailing flap according to any one of claims 1 to 6, comprising a frame and a wing fixing assembly, characterized in that: It also includes an environmental control component, multiple sets of strain gauge groups, and a test chamber. The strain gauge group is composed of multiple strain gauges arranged at equal intervals. The environmental control component includes a blower assembly, a temperature control component, and a rain shower component. The wing fixing component includes wing fixing clamps, a support plate, a support frame, and a mounting plate. The test chamber is fixed on the frame, and openings are provided at both ends of the test chamber. One end of the horizontally arranged mounting plate passes through one of the openings and enters the test chamber, and is fixed to the bottom plate of the test chamber through a column, and the other end is fixed to the frame. There is a gap between the lower surface of the mounting plate and the bottom plate. The support frame is fixed to the bottom plate. Two symmetrically arranged wing fixing clamps are detachably fixed on both sides of the support frame and are located on both sides of the mounting plate. The blower assembly includes a motor and a blower. The blower is fixed at one end of the mounting plate outside the test chamber and is driven by the motor. The motor is controlled by a controller, and the air outlet of the blower faces the opening of the test chamber. The temperature control component includes a circulation pipe, which is fixed on the lower surface of the mounting plate and is located between the bottom plate and the mounting plate. A rain shower component is fixed above the mounting plate on the support frame. The rain shower component is composed of multiple precipitation rain shower nozzles arranged in an array.

8. The testing device used in the fatigue life testing method for the riveting holes of the rear flap of an aircraft according to claim 7, characterized in that: A horizontally arranged support plate is fixed on the mounting plate through a connecting frame, and the support plate is located directly below the rain shower component. The wing fixing clamps are fixed on the support frame by bolts and nuts.

9. The test device used in the fatigue life test method for the riveting holes of the aircraft trailing flap according to claim 7, characterized in that: The blower includes a volute, a collector, and an impeller. The volute is fixed on the mounting plate. The impeller is arranged in the volute, forms a rotating pair with the volute, and is driven by the motor to rotate. The air inlet of the volute is fixed to the collector, and the air outlet of the volute faces the opening.

10. The test device used in the fatigue life test method for the riveting holes of the rear flap of an aircraft according to claim 9, characterized in that: The housing of the motor is fixed to the frame, and the output shaft is connected to the impeller through a belt drive mechanism.

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