Uniformly distributed fatigue load loading test device for composite material structure test piece

Abstract

The invention relates to the technical field of fatigue testing, in particular to a uniformly distributed fatigue load loading test device for a composite material structure test piece. The invention aims to provide a device capable of performing uniform distribution load fatigue test on a curved surface structure test piece or a large-size and irregular-shaped structure test piece, namely a uniform distribution fatigue load loading test device for a composite material structure test piece, which comprises a clamping and fixing mechanism and a loading mechanism, the clamping and fixing mechanism comprises a clamping base, a fixing plate is vertically fixed to the clamping base, and a fixing and supporting assembly is fixed to the fixing plate. The loading mechanism comprises a plurality of small loading assemblies and a loading table, each small loading assembly comprises a stand column, each stand column is provided with an external thread, the top end of each stand column is in spherical hinge connection with a small loading disc, a connecting rod is fixed to the loading table, and the top end of each connecting rod is in spherical hinge connection with a large loading disc. The testing device is simple in structure and high in applicability.

Description

Technical Field

[0001] The invention relates to the technical field of fatigue testing, in particular to a uniformly distributed fatigue load loading test device for a composite material structure specimen. Background Art

[0002] Composite materials have the advantages of light weight, excellent mechanical properties, and good corrosion resistance. They are widely used in engineering fields such as aerospace, ships, automobiles, and fans. In actual engineering operations, the load conditions borne by composite structures are relatively complex, and the service environment of their structures or components is relatively harsh. Among them, fatigue damage has become one of the main forms of failure and damage of composite structures. With the continuous development of composite material design technology, the previous design concept based on "static coverage of fatigue" has been unable to fully utilize the load-bearing potential of composite materials by avoiding the analysis of composite material fatigue problems. Therefore, the study of composite material fatigue problems has become one of the important factors in improving structural performance.

[0003] At present, fatigue tests on composite materials are usually carried out with the help of conventional fatigue testing machines. However, conventional fatigue testing machines (such as the MTS series fatigue testing machines) have upper and lower clamping structures and have high requirements on the shape and size of the specimens. They cannot perform fatigue tests on curved specimens or large-sized structural specimens (such as curved composite material structure specimens commonly seen on aircraft). At the same time, when conventional fatigue testing machines are used to perform fatigue tests on structural specimens with irregular surfaces or easily deformed surfaces, the specimens are subjected to uneven loading, which affects the accuracy of the specimen fatigue test. In addition, conventional fatigue testing machines are also unable to directly perform fatigue tests on irregularly shaped composite material structure specimens. Therefore, there is an urgent need for a test device that can uniformly load fatigue loads on curved specimens or composite material structure specimens with large sizes, irregular shapes, or surfaces that are easily deformed. Summary of the invention

[0004] The purpose of the present invention is to provide a device capable of performing uniform fatigue load testing on curved test pieces or composite material structure test pieces of larger size and irregular shape, namely, a uniform fatigue load loading test device for composite material structure test pieces.

[0005] The present invention is achieved by adopting the following technical solutions: A uniformly distributed fatigue load loading test device for composite material structure specimens comprises a clamping and fixing mechanism and a loading mechanism, wherein the clamping and fixing mechanism and the loading mechanism are distributed on the left and right sides; the clamping and fixing mechanism comprises a clamping base, a fixing plate is vertically fixed on the clamping base, a fixing support assembly is fixed on the fixing plate, and the fixing support assembly is used to fix the left end of the composite material structure specimen on the right end surface of the fixing plate; the loading mechanism comprises a plurality of small loading assemblies and a loading platform for applying fatigue load to the composite material structure specimen (the loading platform belongs to existing equipment, and in specific implementation, the loading platform can also adopt the lower clamp of a conventional fatigue testing machine), each small loading assembly comprises a column, each column is provided with an external thread and an upper nut and a lower nut adapted to the external thread, the top end of the column is ball-jointed to connect the small loading disc, a vertically arranged connecting rod is installed on the loading platform, a large loading disc is fixed to the top end of the connecting rod through a plurality of circumferentially arranged diagonal braces, a plurality of loading through holes adapted to the columns are provided on the large loading disc, and the upper nut is located at the upper part of the loading through hole, and the lower nut is located at the lower part of the loading through hole.

[0006] The usage steps are as follows: 1) Use a fixed support assembly to fix the left end of the composite material structure specimen to the right end surface of the fixed plate; 2) Use a loading mechanism to apply a fatigue load to the composite material structure specimen, wherein the number and position of the small loading assemblies are determined according to the shape, size and specific fatigue test position of the composite material structure specimen, thereby achieving uniform fatigue load loading. When installing the small loading assembly, the column passes through the loading through hole, and then the height of each column can be adjusted according to the curvature of the test area of ​​the composite material structure specimen under test, and the ball joint at the top of the column can be matched, so that multiple small loading discs are in contact with the lower surface of the composite material structure specimen. At this time, the upper nut is located on the upper part of the large loading disc and is tightened to the column, and the lower nut is located on the lower part of the large loading disc and is tightened to the column. Finally, the loading platform is started to drive multiple small loading assemblies to load uniform fatigue loads on the composite material structure specimen. Among them, the height of the column is adjusted by extracting the curvature information of the test surface of the structural specimen, thereby achieving surface fitting in the vertical direction. The small loading disk is fitted to the test surface of the composite material structure specimen through the ball joint structure. The two work together to achieve static surface fitting of the composite material structure specimen. The structure is simple and ingenious, and provides a new idea for fatigue testing of composite material structure specimens.

[0007] Furthermore, the top end of the connecting rod is connected to a plurality of diagonal braces by a ball joint, and the inclination angle of the ball joint is -5° to +5°. During the loading process, when the composite material structure specimen is greatly deformed or its surface is extremely uneven, the height of a certain column may not be sufficient to make the small loading disc completely fit the curved surface of the composite material structure specimen. At this time, the large loading disc can be slightly tilted by the ball joint between the top end of the connecting rod and the plurality of diagonal braces, so that the small loading disc can better fit the test curved surface of the composite material structure specimen, thereby achieving dynamic curved surface fitting of the composite material structure specimen, more flexible adjustment, and stronger applicability.

[0008] Furthermore, a rubber layer is provided on the upper surface of each small loading plate, which effectively reduces the wear of the composite material structure specimen and enables the small loading plate to fit closely to the curved surface of the composite material structure specimen, transforming point contact into surface contact.

[0009] Furthermore, the fixed support assembly includes four fixed support members, namely an upper fixed support member, a lower fixed support member, a front fixed support member, and a rear fixed support member. The upper fixed support member is a strip-shaped L-shaped connecting plate composed of an upper vertical plate and an upper horizontal plate, and the lower fixed support member is a strip-shaped inverted L-shaped connecting plate composed of a lower vertical plate and a lower horizontal plate. The upper horizontal plate and the lower horizontal plate are used to fit and bolt with the upper surface and the lower surface of the left end portion of the composite material structure specimen, respectively. The upper vertical plate and the lower vertical plate are both bolted to the corresponding parts of the fixed plate. The front fixed support member includes a front left end plate and a rear end plate. The front left end plate and the rear end plate constitute a front connecting plate with an L-shaped cross section. The rear end plate is used to be bolted to the front end face of the left end portion of the composite material structure specimen, and the front left end plate is bolted to the corresponding part of the fixed plate. The rear fixed support member includes a rear left end plate and a front end plate. The rear left end plate and the front end plate constitute a rear connecting plate with an L-shaped cross section. The front end plate is used to be bolted to the rear end face of the left end portion of the composite material structure specimen, and the rear left end plate is bolted to the corresponding part of the fixed plate. The structure of the fixed support assembly is concretized and standardized, so that the composite material structure specimen is clamped stably.

[0010] Furthermore, the front fixed support also includes a front upper end plate and a front lower end plate, which are respectively fixed to the upper and lower parts between the front left end plate and the rear end plate, and the front upper end plate is used to be fixedly connected to the left end of the front upper wing plate of the composite material structure specimen, and the front lower end plate is used to be fixedly connected to the left end of the front lower wing plate of the composite material structure specimen. In order to facilitate the connection between the composite material structure specimen and the fixed plate, wing plates need to be set at the upper and lower edges of the front and rear end surfaces of the composite material structure specimen, namely, the front upper wing plate, the front lower wing plate, the rear upper wing plate, and the rear lower wing plate, so as to better fix the composite material structure specimen.

[0011] Furthermore, the clamping and fixing mechanism also includes an L-shaped clamping plate, and two rib plates are distributed in the front and rear of the left side of the L-shaped clamping plate. The horizontal plate of the L-shaped clamping plate is installed on the upper surface of the clamping base, and the right end surface of the vertical plate of the L-shaped clamping plate is fit and fixedly connected to the left end of the fixing plate, thereby further improving the stability of the clamping and fixing mechanism.

[0012] Furthermore, the upper surface of the clamping base is provided with sliding holes arranged on the left and right, and the horizontal plate of the L-shaped clamping plate is penetrated by sliding bolts matched with the sliding holes, and the sliding bolts are matched with sliding nuts, which facilitate the adjustment of the left and right positions of the L-shaped clamping plate, so that the center of the composite material structure specimen is matched with the center of the loading platform, further ensuring that the loading platform loads the composite material structure specimen evenly.

[0013] Furthermore, the shape of the large loading plate is circular, triangular or rectangular, and the shape of the large loading plate can be selected according to the shape and size of the composite material structure specimen.

[0014] The beneficial effects produced by the present invention are as follows: The uniformly distributed fatigue load loading test device described in the present invention realizes fatigue testing of curved structure specimens or structural specimens with large sizes, irregular shapes or surfaces that are prone to deformation through a clamping and fixing mechanism, a loading mechanism and a clever cooperation with a ball joint. Although the structure is simple, it breaks the upper and lower clamping structure of a conventional fatigue testing machine, providing a new idea for fatigue testing, and realizes uniform fatigue loading of composite material structure specimens through multiple small loading components and a ball joint structure. At the same time, the device has strong applicability, and general specimens can be fatigue loaded through the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0017] Figure 1 It is a schematic diagram of the overall structure of the fatigue test loading device of the present invention; Figure 2 is a schematic diagram of the loading mechanism; Figure 3 is a schematic diagram of a clamping and fixing mechanism; Figure 4 It is a structural schematic diagram of the fixed support assembly.

[0018] In the figure: 1-clamping base, 2-fixed plate, 3-fixed support assembly, 31-upper fixed support, 32-lower fixed support, 33-front fixed support, 34-rear fixed support, 4-composite material structure specimen, 5-column, 6-upper nut, 7-lower nut, 8-small loading plate, 9-loading platform, 10-connecting rod, 11-large loading plate, 12-loading through hole, 13-diagonal support, 14-L-type clamping plate, 15-rib plate, 16-sliding hole. DETAILED DESCRIPTION

[0019] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0020] In the description, it should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. It should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two elements. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0022] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0023] like Figures 1 to 4As shown, a uniformly distributed fatigue load loading test device for a composite material structure specimen comprises a clamping and fixing mechanism and a loading mechanism, wherein the clamping and fixing mechanism and the loading mechanism are distributed on the left and right sides; the clamping and fixing mechanism comprises a clamping base 1, a fixing plate 2 is vertically fixed on the clamping base 1, a fixing support assembly 3 is fixed on the fixing plate 2, and the fixing support assembly 3 is used to fix the left end of the composite material structure specimen 4 to the right end surface of the fixing plate 2; the loading mechanism comprises a plurality of small loading assemblies and a loading platform 9 for applying fatigue load to the composite material structure specimen 4 (the loading platform 9 belongs to existing equipment, and in specific implementation, The loading platform 9 can also adopt the lower chuck of a conventional fatigue testing machine). Each small loading component includes a column 5. Each column 5 is provided with an external thread and an upper nut 6 and a lower nut 7 adapted to the external thread. The top end of the column 5 is ball-jointed to the small loading disc. A vertically arranged connecting rod 10 is installed on the loading platform 9. The top end of the connecting rod 10 is fixed with a large loading disc 11 through a plurality of circumferentially arranged diagonal braces 13. The large loading disc 11 is provided with a plurality of loading through holes 12 adapted to the column 5, and the upper nut 6 is located at the upper part of the loading through hole 12, and the lower nut 7 is located at the lower part of the loading through hole 12.

[0024] The usage steps are as follows: 1) Use the fixed support assembly 3 to fix the left end of the composite material structure specimen 4 to the right end surface of the fixed plate 2; 2) Use the loading mechanism to apply fatigue load to the composite material structure specimen 4, wherein the number and position of the small loading assemblies are determined according to the shape, size and specific fatigue test position of the composite material structure specimen 4, thereby achieving uniform fatigue load loading. When installing the small loading assembly, the column 5 passes through the loading through hole 12, and then the height of each column 5 can be adjusted according to the curvature of the experimental area of ​​the tested composite material structure specimen and the ball joint at the top of the column 5, so that multiple small loading discs are in contact with the lower surface of the composite material structure specimen 4. At this time, the upper nut 6 is located at the upper part of the large loading disk 11 and is tightened to the column 5, and the lower nut 7 is located at the lower part of the large loading disk 11 and is tightened to the column 5. Finally, the loading platform 9 is started to drive multiple small loading assemblies to load the composite material structure specimen 4 with uniform fatigue loads. Among them, the height of the column 5 is adjusted by extracting the curvature information of the test surface of the structural specimen to achieve the surface fitting in the vertical direction. The small loading disk can be fitted to the test surface of the composite material structure specimen through the ball joint structure. The two work together to achieve static surface fitting of the composite material structure specimen 4. The structure is simple and ingenious, and provides a new idea for the fatigue test of the composite material structure specimen 4.

[0025] In specific implementation, the top end of the connecting rod 10 is connected to the multiple diagonal braces 13 through a ball joint, and the inclination angle of the ball joint is -5° to +5°. During loading, when the composite material structure specimen 4 is greatly deformed or its surface is extremely uneven, the height of a certain column 5 may not be enough to make the small loading disc completely fit the curved surface of the composite material structure specimen 4. At this time, the large loading disc 11 can be slightly tilted through the ball joint between the top end of the connecting rod 10 and the multiple diagonal braces 13, so that the small loading disc 8 can better fit the dynamic curved surface of the composite material structure specimen 4, making the adjustment more flexible and more applicable.

[0026] In specific implementation, the upper surface of each small loading plate 8 is provided with a rubber layer, which effectively reduces the wear of the composite material structure specimen 4 and makes the small loading plate 8 closely fit the test surface of the composite material structure specimen 4, transforming point contact into surface contact.

[0027] In specific implementation, the fixed support assembly 3 includes four fixed support members, namely an upper fixed support member 31, a lower fixed support member 32, a front fixed support member 33, and a rear fixed support member 34. The upper fixed support member 31 is a strip-shaped L-shaped connecting plate composed of an upper vertical plate and an upper horizontal plate, and the lower fixed support member 32 is a strip-shaped inverted L-shaped connecting plate composed of a lower vertical plate and a lower horizontal plate. The upper horizontal plate and the lower horizontal plate are used to fit and bolt to the upper surface and the lower surface of the left end of the composite material structure specimen 4, respectively. The upper vertical plate and the lower vertical plate are both opposite to the fixed plate 2. The front fixed support member 33 includes a front left end plate and a rear end plate, the front left end plate and the rear end plate form a front connecting plate with an L-shaped cross section, the rear end plate is used to be bolted to the front end face of the left end of the composite material structure specimen 4, and the front left end plate is bolted to the corresponding part of the fixed plate 2, and the rear fixed support member 34 includes a rear left end plate and a front end plate, the rear left end plate and the front end plate form a rear connecting plate with an L-shaped cross section, the front end plate is used to be bolted to the rear end face of the left end of the composite material structure specimen 4, and the rear left end plate is bolted to the corresponding part of the fixed plate 2. The structure of the fixed support assembly 3 is concretized and standardized, so that the composite material structure specimen 4 is clamped stably.

[0028] In specific implementation, the front fixed support member 33 also includes a front upper end plate and a front lower end plate, which are respectively fixed to the upper and lower parts between the front left end plate and the rear end plate, and the front upper end plate is used to be fixedly connected to the left end of the front upper wing plate of the composite material structure specimen 4, and the front lower end plate is used to be fixedly connected to the left end of the front lower wing plate of the composite material structure specimen 4. In order to facilitate the connection between the composite material structure specimen 4 and the fixed plate 2, wing plates need to be set at the upper and lower edges of the front and rear end surfaces of the composite material structure specimen, namely, the front upper wing plate, the front lower wing plate, the rear upper wing plate, and the rear lower wing plate, so as to better fix the composite material structure specimen 4.

[0029] In specific implementation, the clamping and fixing mechanism also includes an L-shaped clamping plate 14, and two rib plates 15 are distributed in the front and rear of the left side of the L-shaped clamping plate 14. The horizontal plate of the L-shaped clamping plate 14 is installed on the upper surface of the clamping base 1, and the right end surface of the vertical plate of the L-shaped clamping plate 14 is fitted and fixedly connected with the left end surface of the fixing plate 2, thereby further improving the stability of the clamping and fixing mechanism.

[0030] During specific implementation, the upper surface of the clamping base 1 is provided with sliding holes 16 arranged on the left and right, and the horizontal plate of the L-shaped clamping plate 14 is penetrated by sliding bolts matched with the sliding holes 16, and the sliding bolts are matched with sliding nuts, which are convenient for adjusting the left and right positions of the L-shaped clamping plate 14, so that the center of the composite material structure specimen 4 is matched with the center of the loading platform 9, further ensuring that the loading platform 9 evenly loads the composite material structure specimen 4.

[0031] In a specific implementation, the shape of the large loading plate 11 is circular, triangular or rectangular. The shape of the large loading plate 11 can be selected according to the shape and size of the composite material structure specimen 4 .

[0032] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A uniformly distributed fatigue load testing device for composite material structure specimens, characterized in that: The invention comprises a clamping and fixing mechanism and a loading mechanism, wherein the clamping and fixing mechanism and the loading mechanism are distributed on the left and right sides; the clamping and fixing mechanism comprises a clamping base (1), a fixing plate (2) is vertically fixed on the clamping base (1), a fixing support assembly (3) is fixed on the fixing plate (2), and the fixing support assembly (3) is used to fix the left end of the composite material structure specimen (4) to the right end surface of the fixing plate (2); the loading mechanism comprises a plurality of small loading assemblies and a loading platform (9) for applying fatigue load to the composite material structure specimen (4), each small loading assembly comprises a column (5), and each The columns (5) are each provided with an external thread and an upper nut (6) and a lower nut (7) adapted to the external thread. The top end of the column (5) is connected to a small loading disc by a ball joint. A vertically arranged connecting rod (10) is fixed to the loading platform (9). A large loading disc (11) is fixed to the top end of the connecting rod (10) via a plurality of circumferentially arranged diagonal bracing members (13). The large loading disc (11) is provided with a plurality of loading through holes (12) adapted to the columns (5), and the upper nut (6) is located above the loading through hole (12), and the lower nut (7) is located below the loading through hole (12).

2. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 1, characterized in that: The top end of the connecting rod (10) is connected to a plurality of diagonal support members (13) via a ball joint, and the inclination angle of the ball joint is -5° to +5°.

3. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 2, characterized in that: The upper surface of each small loading plate (8) is provided with a rubber layer.

4. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 3, characterized in that: The fixed support assembly (3) comprises four fixed support members, namely an upper fixed support member (31), a lower fixed support member (32), a front fixed support member (33), and a rear fixed support member (34); the upper fixed support member (31) is a strip-shaped L-shaped connecting plate composed of an upper vertical plate and an upper horizontal plate; the lower fixed support member (32) is a strip-shaped inverted L-shaped connecting plate composed of a lower vertical plate and a lower horizontal plate; the upper horizontal plate and the lower horizontal plate are respectively adapted to fit and be bolted to the upper surface and the lower surface of the left end of the composite material structure specimen (4); the upper vertical plate and the lower vertical plate are both aligned with the opposite side of the fixed plate (2); The front fixed support member (33) comprises a front left end plate and a rear end plate, the front left end plate and the rear end plate form a front connecting plate with an L-shaped cross section, the rear end plate is used to be bolted to the front end face of the left end portion of the composite material structure specimen (4), the front left end plate is bolted to the corresponding portion of the fixing plate (2), the rear fixed support member (34) comprises a rear left end plate and a front end plate, the rear left end plate and the front end plate form a rear connecting plate with an L-shaped cross section, the front end plate is used to be bolted to the rear end face of the left end portion of the composite material structure specimen (4), the rear left end plate is bolted to the corresponding portion of the fixing plate (2).

5. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 4, characterized in that: The front fixed support member (33) further comprises a front upper end plate and a front lower end plate, the front upper end plate and the front lower end plate being respectively fixed to the upper portion and the lower portion between the front left end plate and the rear end plate, the front upper end plate being used for being fixedly connected to the left end portion of the front upper wing plate of the composite material structure specimen (4), and the front lower end plate being used for being fixedly connected to the left end portion of the front lower wing plate of the composite material structure specimen (4).

6. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 5, characterized in that: The clamping and fixing mechanism also includes an L-shaped clamping plate (14), two rib plates are distributed at the front and rear of the left side of the L-shaped clamping plate (14), the L-shaped clamping plate (14) is mounted on the clamping base (1), and the right end surface of the vertical plate of the L-shaped clamping plate (14) is fitted and fixedly connected to the left end surface of the fixing plate (2).

7. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 6, characterized in that: The upper surface of the clamping base (1) is provided with sliding holes (16) arranged on the left and right, and the horizontal plate of the L-shaped clamping plate (14) is penetrated with sliding bolts matched with the sliding holes (16), and the sliding bolts are matched with sliding nuts.

8. The uniformly distributed fatigue load loading test device for composite material structure specimens according to claim 7, characterized in that: The shape of the large loading plate (11) is circular, triangular or rectangular.

Images