A compression-shear combined loading system based on a pulley system multi-point mean loading

Abstract

The application relates to a compression-shear composite loading system based on a pulley system multi-point mean loading, and relates to a compression-shear composite loading system. In order to solve the problem that the traditional compression-shear composite loading is prone to uneven shear flow for a large-size composite stiffened wall plate structure, the application applies uniform compression loads to the side end surface loading end of a test piece through compression actuating cylinders and a flat pressing plate; two shear actuating cylinders output leftward shear loads along the upper end surface of the test piece; and the other two shear actuating cylinders output rightward shear loads along the lower end surface of the test piece; the loads are converted in direction through a pulley assembly and finally act on the shear plates on the upper and lower sides of the test piece. The application realizes the test under different compression-shear ratios by simultaneously adjusting the sizes of the compression and shear actuating cylinder forces, and optimizes the problem of uneven shear loading through the multi-point coordinated loading system, so that the shear of the measuring point is uniform, and the strength test of the large-size stiffened wall plate structure can be better satisfied.

Description

TECHNICAL FIELD

[0001] The present application relates to a compression-shear composite loading system, in particular to a compression-shear composite loading system based on a multi-point mean loading of a pulley system, and belongs to the technical field of structural strength. BACKGROUND

[0002] As a key component of an aircraft, a composite stiffened panel is widely used in modern thin-walled aviation structures such as a fuselage and a wing, has the characteristics of light weight, high temperature resistance, impact resistance and fatigue resistance, and has good buckling and post-buckling load bearing capacity. By using a composite stiffened panel, the stability of the aircraft structure can be significantly improved. In actual service, the composite stiffened panel is affected by the combined action of compression load and in-plane shear load, which causes interlaminar and interlayer damage, cracks, delamination, buckling and other defects. In addition, various damages may interact during the post-buckling process, causing more serious internal damage to the stiffened panel, leading to material failure and reducing the load bearing capacity, which affects the safe operation of the aircraft. Therefore, many scholars at home and abroad have applied Hashin, Puckt and other damage failure criteria to conduct a large number of progressive damage studies on the damage and failure process of the composite stiffened panel, and have conducted experimental research using various compression-shear composite devices.

[0003] A pulley block is a mechanical design assembled by multiple movable pulleys and fixed pulleys. The pulley block can not only save effort but also change the direction of force. By introducing the pulley block, uniform loading of the large-sized stiffened panel under compression load and in-plane shear load is achieved. The cost of materials is reduced, and the phenomenon of uneven shear force transmission is optimized, which plays an important role in the compression-shear composite test of the large-sized stiffened panel.

[0004] When a large-sized composite stiffened panel structure is subjected to traditional compression-shear composite loading, uneven shear flow is prone to occur. In order to meet the strength test requirements of large-sized structural parts, a compression-shear composite loading system that can meet the test requirements of large-sized panels is needed. Through the multi-point coordinated loading system, the strength test of the large-sized stiffened panel structure and the compression-shear composite test of other large-sized aircraft parts can be better met. The cost of materials is reduced, and the stress condition of the large-sized panel is more accurately simulated. SUMMARY

[0005] In order to meet the strength test requirements of large-sized structural parts, to accurately study the influence of the combined action of tensile load and in-plane shear load on the composite stiffened panel under actual working conditions, to solve the problem of uneven shear flow when a large-sized composite stiffened panel structure is subjected to traditional compression-shear composite loading, and to further propose a compression-shear composite loading system based on a multi-point mean loading of a pulley system.

[0006] The technical scheme adopted by the present application to solve the above problems is:

[0007] The present application comprises a first counterforce frame, a second counterforce frame, a third counterforce frame, a fourth counterforce frame, a compression action cylinder, a flat pressing plate, a test piece, a lower pressing head and a support column, the lower surface of the first counterforce frame is fixedly connected with the left side of the upper surface of the fourth counterforce frame, the lower surface of the third counterforce frame is fixedly connected with the right side of the upper surface of the fourth counterforce frame, and the upper surface of the third counterforce frame is fixedly connected with the right side of the lower surface of the second counterforce frame; the compression action cylinder is installed on the first counterforce frame, the compression action cylinder is connected with the flat pressing plate through a pressure sensor, and the lower pressing head is connected with the third counterforce frame through the support column; the test piece is installed between the flat pressing plate and the lower pressing head, and the two side ends of the test piece are rotatably connected with the flat pressing plate and the lower pressing head, respectively.

[0008] The compression-shear composite loading system based on the pulley system multi-point average loading further comprises pulley assemblies A, B, C and D and a multi-point average loading system, the multi-point average loading system comprises first, second, third, fourth, fifth, sixth, seventh and eighth shear plates, the upper end of the test piece is provided with the first, second, third and fourth shear plates, and the lower end surface of the test piece is provided with the fifth, sixth, seventh and eighth shear plates, the pulley assemblies A and D are installed on the first counterforce frame, the pulley assemblies B and C are installed on the third counterforce frame, the pulley assembly A is connected with the first and second shear plates, the pulley assembly B is connected with the third and fourth shear plates, the pulley assembly C is connected with the fifth and sixth shear plates, and the pulley assembly D is connected with the seventh and eighth shear plates.

[0009] Further, the pulley assembly A comprises first, second, third fixed pulleys, a first steel cable, a first shear actuating cylinder, a fourth fixed pulley, a first tension sensor, a fifth fixed pulley and a sixth fixed pulley, the first shear actuating cylinder is installed on the first counterforce frame and located at the upper portion of the compression action cylinder, the fourth fixed pulley is installed on the first shear actuating cylinder, one end of the first steel cable is connected to the first shear plate through the fourth fixed pulley, the first fixed pulley and the second fixed pulley, the other end of the first steel cable is connected to the second shear plate through the fourth fixed pulley, the third fixed pulley, the fifth fixed pulley and the sixth fixed pulley, and the first tension sensor is located on the first steel cable.

[0010] Further, the pulley assembly B comprises a seventh fixed pulley, an eighth fixed pulley, a second tension sensor, a second steel cable, a ninth fixed pulley, a tenth fixed pulley, a second shearing actuator, the second shearing actuator is installed on the third counter-force frame and located at the upper part of the support column, the tenth fixed pulley is installed on the second shearing actuator, one end of the second steel cable is connected to the third shearing plate through the tenth fixed pulley, the seventh fixed pulley and the eighth fixed pulley; the other end of the second steel cable is connected to the fourth shearing plate through the tenth fixed pulley and the ninth fixed pulley, and the second tension sensor is located on the second steel cable.

[0011] Further, the pulley assembly C comprises a third tension sensor, a third steel cable, a tenth fixed pulley, a twelfth fixed pulley, a thirteenth fixed pulley, a third shearing actuator, a fourteenth fixed pulley, a fifteenth fixed pulley, a sixteenth fixed pulley, the third shearing actuator is installed on the third counter-force frame and located at the lower part of the support column, one end of the third steel cable is connected to the fifth shearing plate through the fifteenth fixed pulley, the thirteenth fixed pulley and the twelfth fixed pulley; the other end of the third steel cable is connected to the sixth shearing plate through the fifteenth fixed pulley, the tenth fixed pulley, the fourteenth fixed pulley and the sixteenth fixed pulley; and the third tension sensor is located on the third steel cable.

[0012] Further, the pulley assembly D comprises a seventeenth fixed pulley, an eighteenth fixed pulley, a nineteenth fixed pulley, a fourth tension sensor, a fourth steel cable, a twentieth fixed pulley and a fourth shearing actuator, the fourth shearing actuator is installed on the first counter-force frame and located at the lower part of the compression actuator, one end of the fourth steel cable is connected to the seventh shearing plate through the twentieth fixed pulley, the eighteenth fixed pulley and the seventeenth fixed pulley; the other end of the fourth steel cable is connected to the eighth shearing plate through the twentieth fixed pulley and the nineteenth fixed pulley; and the fourth tension sensor is located on the fourth steel cable.

[0013] Further, the first shearing plate, the second shearing plate, the third shearing plate, the fourth shearing plate, the fifth shearing plate, the sixth shearing plate, the seventh shearing plate and the eighth shearing plate are all made of aluminum alloy.

[0014] Further, the compression-shear composite loading system based on the pulley system multi-point average loading further comprises a first load sensor and a second load sensor, the first load sensor is installed on one side of the upper end surface of the test piece, and the second load sensor is installed on the other side of the lower end surface of the test piece.

[0015] A compression-shear composite loading method based on a pulley system multi-point average loading, which comprises the following steps:

[0016] Step one: according to the size of the test piece and the position of the stiffened wall plate, strain measurement points are selected, strain gauges are installed on the test piece, and the arrangement of the strain measurement points is performed;

[0017] Step two: fix the test piece on the test system, align the flat plate with the left end of the test piece, and rotate the flat plate with the left end of the test piece;

[0018] Step three: adjust the position of the compression actuator before the test, so that the pressure center coincides with the stiffness center (pressure center) of the cross section of the test piece, and the pressure center is located at the cross section center of the longeron and the skin;

[0019] Step four: adjust the shear frame before the test, so that the shear load passes through the skin center of the test piece 22, that is, the shear center is located at the cross section center of the skin;

[0020] Step five: install the first load sensor on the left side of the upper end surface of the test piece, and install the second load sensor on the right side of the lower end surface of the test piece, for monitoring the vertical shear force of the test piece at any time;

[0021] Step six: install the first shear actuator and the fourth shear actuator on the first counterforce frame, install the second shear actuator and the third shear actuator on the third counterforce frame, install the first shear plate, the second shear plate, the third shear plate and the fourth shear plate on the upper end surface of the test piece, and install the fifth shear plate, the sixth shear plate, the seventh shear plate and the eighth shear plate on the lower end surface of the test piece;

[0022] Step seven: fix all the fixed pulleys on the support surface by bolts, and connect the pulley blocks by steel cables; adjust the positions of the first fixed pulley to the twentieth fixed pulley, so that the shear forces at the left and right ends of the test piece are symmetrically loaded with the same center;

[0023] Step eight: control the operation of the compression actuator and the first shear actuator to the fourth shear actuator by computer at the same time, so as to apply compression load and shear load to the test piece at the same time;

[0024] Step nine: during the loading process, use the strain tester and the electronic displacement sensor to measure the strain of the test piece;

[0025] Step ten: load at a loading rate of 1mm / min to the buckling load, determine the buckling load of the test piece according to the inflection point of the load-strain curve and the observation on the test site, and then unload to zero;

[0026] Step eleven: load at a loading rate of 1mm / min to the buckling load, then load at a loading rate of 0.5mm / min to 1.5 times the buckling load, and then load to the destruction of the test piece with a step difference of 2% of the buckling load, and then unload to zero;

[0027] Step twelve: visually inspect and non-destructively test the test piece to confirm the failure mode, and process the test data in the computer.

[0028] The beneficial effects of the present application are:

[0029] 1. Since the compression-shear composite loading system has the advantages of mutual independence and non-interference when applying compression load and shear load, the test under different compression-shear ratios can be realized by simultaneously adjusting the sizes of compression and shear cylinder forces;

[0030] 2. Generally, the composite load uses multiple cylinders to realize the lateral and longitudinal compression-shear composite load loading, although the sizes of the loads applied by different cylinders can be arbitrarily changed, the device consumes a large amount of materials. The present application realizes the compression-shear composite loading of the large-sized stiffened wall plate test piece by introducing a pulley block and using fewer cylinders, thereby reducing the number of cylinders used and lowering the cost of the compression-shear composite test;

[0031] 3. The shear load is applied to the upper and lower shear plates of the test piece through the steel cable after the action of the pulley system, and the pulley system is symmetrically stretched by double cables on both sides, so as to ensure that the side shear flow is located in the center of the skin;

[0032] 4. The shear load is applied by using the frame self-balancing principle, and the frame formed by the first to eighth shear plates has a tendency to rotate around the rotation shaft under the action of the reaction force of the test piece, so that the shear plates apply shear load to the left end of the test piece, and according to the balance of the moment, the shear flows on the four sides of the test piece are equal, thereby optimizing the problem of uneven shear load.

[0033] 5. Through the multi-point coordinated loading system, the strength test of the large-sized stiffened wall plate structure and the compression-shear composite test of other large aircraft parts can be better satisfied, the cost of materials is reduced, and the test results of the large wall plate compression-shear composite are more accurate and reliable. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a structural schematic view of the multi-point average loading compression-shear composite loading device of the present application;

[0035] Figure 2 It is a punching position schematic view of the test piece of the present application;

[0036] Figure 3 It is a shear flow loading schematic view of the compression-shear composite loading of the test piece of the present application;

[0037] Figure 4 It is a first-order buckling analysis result view of the test model of the present application.

[0038] In the figure: 1-first counterforce frame, 2-first fixed pulley, 3-second fixed pulley, 4-third fixed pulley, 5-first steel cable, 6-first shearing actuator, 7-fourth fixed pulley, 8-first tension sensor, 9-first load sensor, 10-fifth fixed pulley, 11-first shearing plate, 12-sixth fixed pulley, 13-second shearing plate, 14-seventh fixed pulley, 15-eighth fixed pulley, 16-third shearing plate, 17-second tension sensor, 18-second steel cable, 19-ninth fixed pulley, 20-fourth shearing plate, 21-tenth fixed pulley, 22-test piece, 23-pressing head, 24-second counterforce frame, 25-second shearing actuator, 26-third tension sensor, 27-support column, 28-third steel cable, 29-tenth fixed pulley, 30-twelfth fixed pulley, 31-thirteenth fixed pulley, 32-third counterforce frame, 33-fourth counterforce frame, 34-third shearing actuator, 35-fifth shearing plate, 36-fourteenth fixed pulley, 37-fifteenth fixed pulley, 38-second load sensor, 39-sixteenth fixed pulley, 40-sixth shearing plate, 41-seventeenth fixed pulley, 42-eighteenth fixed pulley, 43-seventh shearing plate, 44-nineteenth fixed pulley, 45-fourth tension sensor, 46-eighth shearing plate, 47-fourth steel cable, 48-pressing plate, 49-twentieth fixed pulley, 50-pressure sensor, 51-fourth shearing actuator, 52-compression actuator. DETAILED DESCRIPTION

[0039] DETAILED DESCRIPTION Figure 1 In this embodiment, the compression and shear combined loading system based on the pulley system multi-point average loading includes a first counterforce frame 1, a second counterforce frame 24, a third counterforce frame 32, a fourth counterforce frame 33, a compression actuator 52, a pressing plate 48, a test piece 22, a pressing head 23 and a support column 27. The lower surface of the first counterforce frame 1 is fixedly connected to the left side of the upper surface of the fourth counterforce frame 33. The lower surface of the third counterforce frame 32 is fixedly connected to the right side of the upper surface of the fourth counterforce frame 33. The upper surface of the third counterforce frame 32 is fixedly connected to the right side of the lower surface of the second counterforce frame 24. The compression actuator 52 is installed on the first counterforce frame 1. The compression actuator 52 is connected to the pressing plate 48 through a pressure sensor 50. The pressing head 23 is connected to the third counterforce frame 32 through the support column 27. The test piece 22 is installed between the pressing plate 48 and the pressing head 23. The two ends of the test piece 22 are rotatably connected to the pressing plate 48 and the pressing head 23 respectively.

[0040] The compression-shear composite loading system based on the pulley system multi-point mean loading further comprises pulley assembly A, pulley assembly B, pulley assembly C, pulley assembly D and a multi-point mean loading system, the multi-point mean loading system comprises first shear plate 11, second shear plate 13, third shear plate 16, fourth shear plate 20, fifth shear plate 35, sixth shear plate 40, seventh shear plate 43 and eighth shear plate 46, the upper end surface of the test piece 22 is provided with the first shear plate 11, the second shear plate 13, the third shear plate 16 and the fourth shear plate 20, the lower end surface of the test piece 22 is provided with the fifth shear plate 35, the sixth shear plate 40, the seventh shear plate 43 and the eighth shear plate 46, the pulley assembly A and the pulley assembly D are installed on the first counterforce frame 1, the pulley assembly B and the pulley assembly C are installed on the third counterforce frame 32, the pulley assembly A is connected with the first shear plate 11 and the second shear plate 13, the pulley assembly B is connected with the third shear plate 16 and the fourth shear plate 20, the pulley assembly C is connected with the fifth shear plate 35 and the sixth shear plate 40, and the pulley assembly D is connected with the seventh shear plate 43 and the eighth shear plate 46.

[0041] The present application is directed to a 3m-level composite stiffened panel, and according to the comprehensive technology of material science, mechanics and mechanics, a compression-shear composite loading system is provided, preferably a compression actuator cylinder 52 adopts 200T pressure, and the maximum range is 2000mm.

[0042] Specific implementation method two: combined Figure 1 In this embodiment, the pulley assembly A comprises a first fixed pulley 2, a second fixed pulley 3, a third fixed pulley 4, a first steel cable 5, a first shear actuator cylinder 6, a fourth fixed pulley 7, a first tension sensor 8, a fifth fixed pulley 10 and a sixth fixed pulley 12, the first shear actuator cylinder 6 is installed on the first counterforce frame 1 and located at the upper part of the compression actuator cylinder 52, the fourth fixed pulley 7 is installed on the first shear actuator cylinder 6, one end of the first steel cable 5 is connected to the first shear plate 11 through the fourth fixed pulley 7, the first fixed pulley 2 and the second fixed pulley 3, and the other end of the first steel cable 5 is connected to the second shear plate 13 through the fourth fixed pulley 7, the third fixed pulley 4, the fifth fixed pulley 10 and the sixth fixed pulley 12, and the first tension sensor 8 is located on the first steel cable 5. The tension on the first steel cable 5 is monitored by the first tension sensor.

[0043] The other components and connection relationships of this embodiment are the same as those of the specific implementation method one.

[0044] Specific implementation method three: combined Figure 1In this embodiment, the pulley assembly B includes a seventh fixed pulley 14, an eighth fixed pulley 15, a second tension sensor 17, a second cable 18, a ninth fixed pulley 19, a tenth fixed pulley 21, a second shearing actuator 25, which is installed on the third counterforce frame 32 and located at the upper part of the support column 27, a tenth fixed pulley 21 installed on the second shearing actuator 25, and one end of the second cable 18 connected to the third shearing plate 16 through the tenth fixed pulley 21, the seventh fixed pulley 14, and the eighth fixed pulley 15. The other end of the second cable 18 is connected to the fourth shearing plate 20 through the tenth fixed pulley 21 and the ninth fixed pulley 19, and the second tension sensor 17 is located on the second cable 18. The tension on the second cable 18 is monitored by the second tension sensor 17.

[0045] The other components and connection relationships of this embodiment are the same as those of Embodiment 1 or 2.

[0046] Embodiment 4: Combination Figure 1 In this embodiment, the pulley assembly C includes a third tension sensor 26, a third cable 28, a tenth fixed pulley 29, a twelfth fixed pulley 30, a thirteenth fixed pulley 31, a third shearing actuator 34, a fourteenth fixed pulley 36, a fifteenth fixed pulley 37, a sixteenth fixed pulley 39, the third shearing actuator 34 is installed on the third counterforce frame 32 and located at the lower part of the support column 27, one end of the third cable 28 is connected to the fifth shearing plate 35 through the fifteenth fixed pulley 37, the thirteenth fixed pulley 31, and the twelfth fixed pulley 30; the other end of the third cable 28 is connected to the sixth shearing plate 40 through the fifteenth fixed pulley 37, the tenth fixed pulley 29, the fourteenth fixed pulley 36, and the sixteenth fixed pulley 39; and the third tension sensor 26 is located on the third cable 28. The tension on the third cable 28 is monitored by the third tension sensor 26.

[0047] The other components and connection relationships of this embodiment are the same as those of Embodiment 1, 2, or 3.

[0048] Embodiment 5: Combination Figure 1 In this embodiment, the pulley assembly D includes a seventeenth fixed pulley 41, an eighteenth fixed pulley 42, a nineteenth fixed pulley 44, a fourth tension sensor 45, a fourth cable 47, a twentieth fixed pulley 49, and a fourth shearing actuator 51, which is installed on the first counterforce frame 1 and located at the lower part of the compression actuator 52. One end of the fourth cable 47 is connected to the seventh shearing plate 43 through the twentieth fixed pulley 49, the eighteenth fixed pulley 42, and the seventeenth fixed pulley 41; the other end of the fourth cable 47 is connected to the eighth shearing plate 46 through the twentieth fixed pulley 49 and the nineteenth fixed pulley 44; and the fourth tension sensor 45 is located on the fourth cable 47.

[0049] The tension on the fourth cable 47 is monitored by a fourth tension sensor 45.

[0050] The other components and connection relationships of the embodiment are the same as those of the first, second, third, fourth or fifth embodiment.

[0051] Sixth embodiment: combination Figure 1 In this embodiment, the first shear plate 11, the second shear plate 13, the third shear plate 16, the fourth shear plate 20, the fifth shear plate 35, the sixth shear plate 40, the seventh shear plate 43 and the eighth shear plate 46 are all made of aluminum alloy. The use of aluminum alloy can eliminate the uneven distribution of bolt shear force caused by load.

[0052] The other components and connection relationships of the embodiment are the same as those of the first, second, third, fourth or fifth embodiment.

[0053] Seventh embodiment: combination Figures 1 to 3 In this embodiment, the test piece 22 has two symmetrically arranged shear plates on the front and back surfaces of the skin on one side. Preferably, each shear plate has a length of 520 mm, and the distance between each adjacent two shear plates is 27 mm. Eight bolts are arranged on each shear plate, and the distance between the bolts is 60 mm. The bolt holes with a diameter of 24 mm are used to connect the cables.

[0054] Further, the multi-point mean loading system loads through the first shear plate 11 to the eighth shear plate 46. The eight shear plates form a shear frame that tends to rotate around the rotation shaft under the action of the reaction force of the test piece. The shear plates apply shear load to the upper end of the test piece, and the shear flows on the four sides of the test piece are equal according to the balance of the moment.

[0055] The shear flows on the upper and lower sides of the test piece 22 are applied through the connecting bolts. The test piece 22 is fixed with the shear plates through the bolts. The tension acts on the shear plates, and the bolts conduct the shear force to the test piece. The punching position of the test piece 22 is shown in Figure 2 .

[0056] The other components and connection relationships of the embodiment are the same as those of the first, second, third, fourth, fifth or sixth embodiment.

[0057] Eighth embodiment: combination Figure 1 In this embodiment, the compression-shear composite loading system based on the pulley system multi-point mean loading further includes a first load sensor 9 and a second load sensor 38. The first load sensor 9 is installed on one side of the upper end surface of the test piece 22. The second load sensor 38 is installed on the other side of the lower end surface of the test piece 22. This can prevent the test piece 22 from bending too early and can monitor the vertical shear force at any time.

[0058] The other components and connection relationships of the embodiment are the same as those of the first, second, third, fourth, fifth, sixth, or seventh embodiment.

[0059] Ninth Embodiment: Combination Figures 1 to 3 In the embodiment, the shear load applied by the first shear actuator 6 and the second shear actuator 25 is converted in direction by the first pulley assembly and the second pulley assembly, and a shear load in the direction of the left side of the test piece 22 is generated.

[0060] The shear load applied by the third shear actuator 34 and the fourth shear actuator 51 is converted in direction by the third pulley assembly and the fourth pulley assembly, and a shear load in the direction of the right side of the test piece 22 is output.

[0061] Further, considering the adjustability in actual tests, a certain space needs to be reserved for the pulley device within the normal operation range of the pulley system.

[0062] The other components and connection relationships of the embodiment are the same as those of the first, second, third, fourth, fifth, sixth, seventh, or eighth embodiment.

[0063] Tenth Embodiment: Combination Figures 1 to 4 In the embodiment, the shear load applied by the first shear actuator 6 and the second shear actuator 25 is converted in direction by the first pulley assembly and the second pulley assembly, and a shear load in the direction of the left side of the test piece 22 is generated.

[0064] Step one: according to the size of the test piece 22 and the position of the stiffened wall plate, the strain measurement points are selected, and the strain gauges are installed on the test piece 22 to arrange the strain measurement points.

[0065] Step two: the test piece 22 is fixed on the test system, the flat pressing plate 48 is aligned with the left end of the test piece 22, and the flat pressing plate 48 is rotationally connected with the left end of the test piece 22; the right end of the test piece 22 is rotationally connected with the lower pressing head 23.

[0066] Step three: before the test, the position of the compression actuator 52 is adjusted so that the pressure center coincides with the stiffness center (pressure center) of the cross section of the test piece 22, and the pressure center is located at the cross section centroid of the stringer and the skin.

[0067] Step four: before the test, the shear frame is adjusted so that the shear load passes through the skin center of the test piece 22, and the shear center is located at the cross section centroid of the skin.

[0068] Step five: the first load sensor 9 is installed on the left side of the upper end surface of the test piece 22, and the second load sensor 38 is installed on the right side of the lower end surface of the test piece 22, for monitoring the vertical shear force of the test piece 22 at any time.

[0069] Step six: install the first and fourth shearing actuators 6 and 51 on the first reaction frame 1, install the second and third shearing actuators 25 and 34 on the third reaction frame 32, and install the first, second, third and fourth shearing plates 11, 13, 16 and 20 on the upper end face of the test piece 22, and install the fifth, sixth, seventh and eighth shearing plates 35, 40, 43 and 46 on the lower end face of the test piece 22;

[0070] Step seven: bolt all the fixed pulleys to the support surface, and connect the pulley blocks by steel ropes, and adjust the positions of the first to twentieth fixed pulleys 2 to 49 to make the shearing forces at the left and right ends of the test piece 22 adopt the same central symmetry loading;

[0071] Step eight: control the compression actuator 52 and the first to fourth shearing actuators 6 to 51 to work by the computer, and apply the compression and shearing loads to the test piece 22 simultaneously;

[0072] Step nine: measure the strain of the test piece 22 by using the strain tester and the electronic displacement sensor during the loading process;

[0073] Step ten: load at a rate of 1 mm / min to the buckling load, determine the buckling load of the test piece 22 according to the inflection point of the load-strain curve and the observation on the test site, and then unload to zero;

[0074] Step eleven: load at a rate of 1 mm / min to the buckling load, then load at a rate of 0.5 mm / min to 1.5 times the buckling load, and then load at a rate of 2% of the buckling load to the destruction of the test piece 22, and then unload to zero;

[0075] Step twelve: visually inspect and non-destructively test the test piece 22 to confirm the failure mode, and process the test data in the computer, and the first-order buckling mode result is shown in Figure 4 .

[0076] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution of the present application, and make equivalent embodiments with equivalent changes, as long as they do not depart from the technical solution of the present application, and are within the spirit and principles of the present application. Any simple modification, equivalent replacement and improvement of the above embodiments, as long as they do not depart from the technical solution of the present application, are within the protection scope of the present application.

Claims

1. A compression-shear composite loading system based on multi-point average loading of a pulley system, comprising a first reaction frame (1), a second reaction frame (24), a third reaction frame (32), a fourth reaction frame (33), a compression actuator (52), a flat plate (48), a test piece (22), a lower pressure head (23), and a support column (27). The lower surface of the first reaction frame (1) is fixedly connected to the left side of the upper surface of the fourth reaction frame (33), and the lower surface of the third reaction frame (32) is fixedly connected to the right side of the upper surface of the fourth reaction frame (33). The upper surface of the third reaction frame (32) is fixedly connected to the right side of the lower surface of the second reaction frame (24); the compression actuator (52) is installed on the first reaction frame (1) and connected to the flat pressure plate (48) through the pressure sensor (50); the lower pressure head (23) is connected to the third reaction frame (32) through the support column (27); the test piece (22) is installed between the flat pressure plate (48) and the lower pressure head (23), and the two ends of the test piece (22) are rotatably connected to the flat pressure plate (48) and the lower pressure head (23) respectively; Its features are: It also includes pulley assemblies A, B, C, and D and a multi-point average loading system; the multi-point average loading system includes a first shear plate (11), a second shear plate (13), a third shear plate (16), and a fourth shear plate (20) set on the upper end face of the test piece (22), and a fifth shear plate (35), a sixth shear plate (40), a seventh shear plate (43), and an eighth shear plate (46) set on the lower end face of the test piece (22); pulley assemblies A and D are installed on the first reaction frame (1), and pulley assemblies B and C are installed on the third reaction frame (32); The pulley assembly A includes a first fixed pulley (2), a second fixed pulley (3), a third fixed pulley (4), a first steel cable (5), a first shearing actuator (6), a fourth fixed pulley (7), a first tension sensor (8), a fifth fixed pulley (10), and a sixth fixed pulley (12). The first shearing actuator (6) is mounted on the first reaction frame (1) and located above the compression actuator (52). The fourth fixed pulley (7) is mounted on the first shearing actuator (6). One end of the first steel cable (5) is connected to the first shearing plate (11) through the fourth fixed pulley (7), the first fixed pulley (2), and the second fixed pulley (3), and the other end is connected to the second shearing plate (13) through the fourth fixed pulley (7), the third fixed pulley (4), the fifth fixed pulley (10), and the sixth fixed pulley (12). The first tension sensor (8) is located on the first steel cable (5). The pulley assembly B includes a seventh fixed pulley (14), an eighth fixed pulley (15), a second tension sensor (17), a second steel cable (18), a ninth fixed pulley (19), a tenth fixed pulley (21), and a second shearing actuator (25). The second shearing actuator (25) is mounted on the third reaction frame (32) and located on the upper part of the support column (27). The tenth fixed pulley (21) is mounted on the second shearing actuator (25). One end of the second steel cable (18) is connected to the third shear plate (16) through the tenth fixed pulley (21), the seventh fixed pulley (14), and the eighth fixed pulley (15), and the other end is connected to the fourth shear plate (20) through the tenth fixed pulley (21) and the ninth fixed pulley (19). The second tension sensor (17) is located on the second steel cable (18). The pulley assembly C includes a third tension sensor (26), a third steel cable (28), an eleventh fixed pulley (29), a twelfth fixed pulley (30), a thirteenth fixed pulley (31), a third shearing actuator (34), a fourteenth fixed pulley (36), a fifteenth fixed pulley (37), and a sixteenth fixed pulley (39). The third shearing actuator (34) is mounted on the third reaction frame (32) and located at the lower part of the support column (27). The fifteenth fixed pulley is mounted on the third shearing actuator. One end of the third steel cable (28) is connected to the fifth shear plate (35) through the fifteenth fixed pulley (37), the thirteenth fixed pulley (31), and the twelfth fixed pulley (30), and the other end is connected to the sixth shear plate (40) through the fifteenth fixed pulley (37), the eleventh fixed pulley (29), the fourteenth fixed pulley (36), and the sixteenth fixed pulley (39). The third tension sensor (26) is located on the third steel cable (28). The pulley assembly D includes a seventeenth fixed pulley (41), an eighteenth fixed pulley (42), a nineteenth fixed pulley (44), a fourth tension sensor (45), a fourth steel cable (47), a twentieth fixed pulley (49), and a fourth shearing actuator (51). The fourth shearing actuator (51) is mounted on the first reaction frame (1) and located below the compression actuator (52). The twentieth fixed pulley is mounted on the fourth shearing actuator. One end of the fourth steel cable (47) is connected to the seventh shearing plate (43) through the twentieth fixed pulley (49), the eighteenth fixed pulley (42), and the seventeenth fixed pulley (41), and the other end is connected to the eighth shearing plate (46) through the twentieth fixed pulley (49) and the nineteenth fixed pulley (44). The fourth tension sensor (45) is located on the fourth steel cable (47).

2. A compression-shear composite loading system based on multi-point average loading of a pulley system according to claim 1, characterized in that: The first shear plate (11), the second shear plate (13), the third shear plate (16), the fourth shear plate (20), the fifth shear plate (35), the sixth shear plate (40), the seventh shear plate (43), and the eighth shear plate (46) are all made of aluminum alloy.

3. A compression-shear composite loading system based on multi-point average loading of a pulley system according to claim 1, characterized in that: A compression-shear composite loading system based on multi-point average loading of pulley system also includes a first load sensor (9) and a second load sensor (38). The first load sensor (9) is installed on one side of the upper end face of the test piece (22); the second load sensor (38) is installed on the other side of the lower end face of the test piece (22).

4. A loading method for a compression-shear composite loading system based on multi-point average loading of a pulley system, as described in any one of claims 1 to 3, comprising the following steps: Step 1: Select strain measurement points according to the size of the test piece (22) and the position of the stiffened wall panel, install the strain gauges on the test piece (22), and arrange the strain measurement points; Step 2: Fix the test piece (22) on the test system, align the flat plate (48) with the left end of the test piece (22), and rotate the flat plate (48) to the left end of the test piece (22); rotate the right end of the test piece (22) to the lower pressure head (23); Step 3: Before the test, adjust the position of the compression actuator (52) so that the pressure center coincides with the stiffness center of the cross section of the test piece (22) and the pressure center is located at the centroid of the cross section of the stringer and the skin. Step 4: Before the test, adjust the shear frame so that the shear load passes through the skin center of the test piece (22), that is, the shear center is located at the centroid of the skin section; Step 5: Install the first load sensor (9) on the left side of the upper end face of the test piece (22) and the second load sensor (38) on the right side of the lower end face to monitor the magnitude of the vertical shear force of the test piece (22) at any time; Step 6: Install the first shearing actuator (6) and the fourth shearing actuator (51) on the first reaction frame (1); install the second shearing actuator (25) and the third shearing actuator (34) on the third reaction frame (32); install the first shearing plate (11), the second shearing plate (13), the third shearing plate (16) and the fourth shearing plate (20) on the upper end face of the test piece (22); install the fifth shearing plate (35), the sixth shearing plate (40), the seventh shearing plate (43) and the eighth shearing plate (46) on the lower end face of the test piece (22); Step 7: Fix all the fixed pulleys to the support surface with bolts and connect the pulley group with steel cables; adjust the positions of the first fixed pulley (2) to the twentieth fixed pulley (49) so that the shear force at the left and right ends of the test piece (22) is applied with the same central symmetric loading. Step 8: The compression actuator (52) is controlled by computer, and the first shear actuator (6) to the fourth shear actuator (51) are controlled to work simultaneously, so that the test piece (22) is subjected to both compression load and shear load. Step 9: During the loading process, strain measurement of the test piece (22) is performed using a strain tester and an electronic displacement sensor; Step 10: Load to the buckling load at a loading rate of 1 mm / min, determine the buckling load of the test piece (22) based on the inflection point of the load-strain curve and on-site observation, and then unload to zero; Step 11: Load to the buckling load at a loading rate of 1 mm / min, then load to 1.5 times the buckling load at a loading rate of 0.5 mm / min, then load in increments of 2% buckling load until the test specimen (22) fails, and then unload to zero; Step 12: Visually inspect and perform non-destructive testing on the test piece (22), confirm the failure mode, and process the test data in the computer.

Images