Normal stress application device and method for adhesive interface shear test piece

Abstract

The application relates to a normal stress applying device and method for a bonding interface shear test piece. The device comprises a main body, a guide part arranged on the main body, and a gap between the guide part and the main body; one end of the guide part is connected with a force applying part, and the other end is abutted with a bonding surface of a test piece; the force applying part applies normal stress to the bonding interface of the test piece through the guide part; clamping devices are arranged at two ends of the test piece, the two ends of the test piece are fixed through the clamping devices, and a shear load is applied to the test piece. The application can analyze the mechanical properties of the bonding interface of viscoelastic materials under complex load by simultaneously applying a shear load and normal stress to the test piece, and has important significance in material design and engineering application.

Description

Technical Field

[0001] This application relates to the field of testing equipment technology, and in particular to a device and method for applying normal stress to an adhesive interface shear test specimen. Background Technology

[0002] Solid rocket motors are characterized by long-term storage and single-use. Storage is a crucial part of the entire life cycle of a solid rocket motor. As the requirements for engine response speed increase, vertical storage is becoming a very common operating condition. For large-diameter engines with large propellant charges, gravity will generate significant shear stress at the bonding interface of the engine sidewall during vertical storage. In subsequent engine storage and ignition pressurization conditions, the creep caused by its own weight and the internal pressure during ignition will cause the propellant bonding interface and the artificial debonding layer on the engine sidewall to bear at least large loads in both lateral and shear stress directions simultaneously. This can easily lead to debonding and other damage at the bonding interface, affecting the internal ballistic performance of the engine and compromising its structural integrity. Since solid propellants are typical viscoelastic materials, they are incompressible and pressure-sensitive. Their strength, elongation, and failure modes vary greatly under different operating conditions. Moreover, research on the shear performance of the engine bonding interface is still limited. Therefore, it is urgent to conduct shear load tests on the engine bonding interface considering normal stress.

[0003] Most current research on the shear performance of engine bonding interfaces focuses on its uniaxial shear performance. Since the shear test specimens of the bonding interface are relatively complex in structure, it is difficult to apply normal stress perpendicular to the interface without interfering with the shear load. Therefore, there are few studies on the shear performance of bonding interfaces considering normal stress. Summary of the Invention

[0004] Therefore, it is necessary to provide a device and method for applying normal stress to adhesive interface shear test specimens that can simultaneously apply shear load and normal stress, adjust the magnitude of normal stress, and analyze the mechanical properties of adhesive interfaces under complex loads. This device is mainly used for the analysis of materials with viscoelastic properties.

[0005] A normal stress application device for an adhesive interface shear test specimen includes a main body, on which a guide is provided, and the guide is clearance-fitted with the main body.

[0006] One end of the guide is connected to the force-applying component, and the other end abuts against the bonding surface of the test piece. The force-applying component applies normal stress to the bonding interface of the test piece through the guide.

[0007] The test piece is provided with clamping devices at both ends, which are used to fix the two ends of the test piece and apply shear load to the test piece.

[0008] In one embodiment, a pressure head is also included; the pressure head is coaxially arranged with the guide member, one end of which is fixed to the guide member, and the other end abuts against the bonding surface of the test piece.

[0009] In one embodiment, a force sensor is also included, which is coaxially arranged with the guide and the pressure head, and fixed between the guide and the pressure head.

[0010] In one embodiment, the rear end of the main body is provided with a through hole, and the force-applying member is placed in the through hole and is connected to the guide member at the end.

[0011] In one embodiment, the force-applying component and the through hole at the rear end of the main body are threaded together.

[0012] In one embodiment, the connection between the guide, the sensor, and the pressure head is a threaded connection.

[0013] In one embodiment, a bracket is provided near the front end of the main body, and a connector is provided inside the bracket to fix the bracket to the test piece.

[0014] In one embodiment, a fastener is also included to abut the connector against the test piece, thereby securing the bracket to the test piece.

[0015] In one embodiment, the clamping device has a groove, the test piece is placed in the groove, and fixed by bolts or pins.

[0016] A method for applying normal stress to a shear test specimen at an adhesive interface, the method comprising:

[0017] The guide, force sensor and pressure head are connected coaxially with threads in sequence. The pressure head abuts against the adhesive surface of the test piece, and the force-applying component is screwed into the main body and connected to the end of the guide.

[0018] The bracket is fixed to the test piece by a connector, and a fastening force is applied by fasteners provided on the bracket, thereby fixing the bracket to the test piece and thus fixing the main body to the test piece;

[0019] Place both ends of the test piece in the clamping device and fix them in place;

[0020] After applying a preset normal stress through the force-applying component, the test piece is subjected to a shear load by pulling the clamping device through a universal tensile testing machine.

[0021] Compared with the prior art, the adhesive interface shear test specimen normal stress application device and method provided by the present invention have the following effects:

[0022] 1. The bracket holds the connector and the test piece together with fasteners, and the entire device is fixed to the test piece by friction. The overall structure is compact and suitable for various types of testing machines, and will not interfere with the testing machine from applying shear load.

[0023] 2. The load is applied through the force-applying component, which is easy to operate and install. The load can be flexibly adjusted during the experiment, making it simple and reliable.

[0024] 3. By simultaneously applying shear load and normal stress, the mechanical properties of the bonding interface of viscoelastic materials under complex loads can be analyzed, which is of great significance in materials design and engineering applications. Attached Figure Description

[0025] Figure 1 Left axonometric view of the normal stress application device for the shear test specimen at the bond interface;

[0026] Figure 2 Right-view axonometric view of the normal stress application device for the shear test specimen at the bond interface;

[0027] Figure 3 This is a schematic diagram of the connector structure;

[0028] Figure 4 This is a schematic diagram of the bracket structure;

[0029] Figure 5 Flowchart of the method for applying normal stress to shear test specimens at adhesive interfaces;

[0030] Explanation of reference numerals in the attached drawings: 1. Main body; 2. Force-applying component; 3. Guide component; 4. Force sensor; 5. Pressure head; 6. Bracket; 61. Fastener; 7. Connector; 71. First connecting part; 72. Second connecting part; 8. Clamping device; 9. Test piece. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0033] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly and specifically defined.

[0034] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In one embodiment, such as Figure 1-4 As shown, a normal stress application device for a shear test specimen at an adhesive interface is provided, comprising a main body 1, which is a rectangular structure with a vertical through-slot in the middle. Two connecting beams are arranged in the width direction within the through-slot. Through holes are respectively provided at the rear end of the main body 1 and on the two connecting beams. Guide members 3 are inserted into the through holes. Guide members 3 are rod structures, with one end placed in the through hole at the rear end of the main body 1 and forming a clearance fit with the main body 1. The end of the force-applying member 2 is in contact with the end of the guide member 3. The other end of the guide member 3 is connected to one end of a force sensor 4, and the other end of the force sensor is connected to a pressure head 5. The pressure head 5 abuts against the adhesive surface of the test specimen 9 and applies axial normal stress to the adhesive surface of the test specimen 9.

[0036] Specifically, the force-applying component 2 is a bolt-like structure with a threaded rod, which is threadedly engaged with the through hole at the rear end of the main body 1. By screwing the force-applying component 2 in and out, the magnitude of the axial force applied to the guide component 3 in contact with it can be controlled. The force sensor 4 is a cylindrical structure with threaded rods at both ends, which are connected to the guide component 3 and the pressure head 5 respectively. One end of the pressure head 5 has a threaded hole that engages with the force sensor 4, and the other end is a closed end that abuts against the bonding surface of the test piece 9. It is worth noting that the force-applying component 2, the guide component 3, the force sensor 4, and the pressure head 5, which are connected in sequence, are all coaxially arranged to ensure that their force application methods are on the same axis; the force sensor 4 is also connected to a digital display, which displays the normal stress loading status in real time.

[0037] The bracket 6 is located near the front end of the main body 1, and the main body 1 is fixed to the test piece 9 by the bracket 6. Specifically, the bracket can be fixed to the upper part of the front end of the main body 1 as shown in the figure, or it can be fixed to the lower part of the front end of the main body 1 as appropriate. The bracket 6 has a rectangular structure with a through groove in the middle to form a hollow structure, and a through hole on the side. A fastener 61 is installed in the through hole. After the test piece 9 is passed through the bracket 6, pressure can be applied to the test piece by the fastener 61, thereby generating friction between the test piece 9 and the inner wall of the bracket 6. The main body 1 is fixed to the test piece 9 by the friction. More specifically, a connector 7 is provided between the fastener 61 and the test piece 9. The connector 7 increases the friction between the test piece 9 and the bracket 6, and at the same time connects the main body and the bracket 6 by the connector 7. The connector 7 has an "L" shaped structure, with a first connecting part 71 and a second connecting part 72. The first connecting part 71 has a through hole and is fixed to the main body 1 by means of screws or bolts. The second connecting part 72 is placed between the fastener 61 and the test piece 9. By rotating the fastener 61, the test piece 9 is fixed between the second connecting part 72 and the inner side wall of the bracket 6, thereby increasing the friction area and reducing damage to the test piece.

[0038] Clamping devices 9 are provided at both ends of the test piece 9. The clamping devices 9 are provided with elongated grooves. By placing the test piece 9 in the grooves and then fixing it with bolts or pins, the clamping devices 8 can be pulled by the universal tensile testing machine to apply shear load to the test piece 9.

[0039] During operation, the normal stress application device for the shear test specimen at the bonded interface is first assembled. The pressure head 5 is connected to one end of the force sensor 4 by a threaded connection. The other end of the force sensor 4 is also fixed to the guide 3 by a threaded connection. The force sensor 4 is connected to the digital display by a wire. Then, the guide 3 is passed through the connecting beam and the through hole at the rear end of the main body 1 to form a clearance fit with the main body 1. Then, the force application component 2 is screwed into the through hole at the rear end of the main body 1. The normal stress application component is then assembled.

[0040] Then, the fixing components are assembled. The first connecting part 71 of the connector 7 is fixed in the reserved hole of the main body 1 by screws or bolts. Then, the test piece 9 is placed tightly against the second connecting part 72 of the connector 7, so that the bracket 6 covers the connector 7 and the test piece 9. The fastener 61 is screwed in to fix the entire normal stress application component onto the test piece 9.

[0041] After placing the test specimen 9 into the clamping device 8 and fixing it with bolts or pins, fix the clamping device 8 onto the external tensile testing machine, screw in the force-applying component 2, push the guide rod to move, so that the pressure head 5 contacts the test specimen, continue to screw in the force-applying component 2, and sense the pressure through the force sensor 4 and transmit the pressure magnitude to the digital display. Detect the pressure to the required magnitude through the digital display, and the normal stress loading is completed. Pull the clamping device 8 through the universal tensile testing machine to apply a shear load to the test specimen 9 to achieve a compression-shear combined test.

[0042] After the test, remove the bolts or pins, take the test piece 9 out of the clamping device, then unscrew the force-applying component 2 until the pressure head 5 is no longer in contact with the test piece 9, unscrew the fastener 61 to remove the bracket 6, and finally remove the test piece 9. The test is now complete.

[0043] It is worth noting that, because the force sensor 4 and the connected digital display of this invention require an external power supply, the load applied by the device may deviate significantly due to excessive deformation of the test piece 9 as it undergoes shear failure during the experiment. Therefore, this device is only suitable for materials with small deformation or the initial stage of material deformation. Furthermore, the device of this invention is suitable for materials with viscoelastic properties, such as engine bonding interfaces, but not for testing the bonding surfaces of metallic materials.

[0044] In summary, existing technologies for viscoelastic materials only consider shear stress, taking into account effects such as rotational and deformation dissipation, and delayed strain generated when shear force is applied. However, they neglect effects such as viscous effects generated when normal stress is applied, thus limiting their application in studying the mechanical properties of viscoelastic materials. This invention, by simultaneously applying dual stresses to viscoelastic materials, allows for further investigation of the mechanical properties of viscoelastic materials under nonlinear effects when both normal and shear forces are applied simultaneously. This has significant implications for materials design and engineering applications.

[0045] In one embodiment, such as Figure 5 As shown, a method for applying normal stress to a shear test specimen at an adhesive interface is provided, including the following steps:

[0046] Step 102: Connect the guide 3, force sensor 4 and pressure head 5 coaxially with threads in sequence. The pressure head 5 abuts against the adhesive surface of the test piece 9. Then screw the force application member 2 into the main body and connect it to the end of the guide 3.

[0047] Step 104: Fix the bracket 6 to the test piece 9 using the connector 7, and apply a tightening force using the fastener 61 provided on the bracket 6, thereby fixing the bracket 6 to the test piece 9, and thus fixing the main body 1 to the test piece 9.

[0048] Step 106: Place both ends of the test piece 9 into the clamping device 8 and fix them.

[0049] Step 108: After applying the preset normal stress through the force-applying component 2, the universal tensile testing machine pulls the clamping device 8 to apply a shear load to the test piece 9.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A device for applying normal stress to a shear test specimen at an adhesive interface, comprising a main body, characterized in that: The main body is provided with a guide component, and the guide component is clearance-fitted with the main body. One end of the guide is connected to the force-applying component, and the other end abuts against the bonding surface of the test piece. The force-applying component applies normal stress to the bonding interface of the test piece through the guide. The test specimen is provided with clamping devices at both ends, which are used to fix the two ends of the test specimen and apply shear load to the test specimen. A bracket is provided near the front end of the main body, and a connector is provided inside the bracket to fix the bracket to the test piece. It also includes fasteners, which abut the connector against the test piece, thereby fixing the bracket to the test piece; The clamping device has a groove, the test piece is placed in the groove and fixed by bolts or pins.

2. The device for applying normal stress to an adhesive interface shear test specimen according to claim 1, characterized in that, It also includes the pressure head; The pressure head is coaxially arranged with the guide member, with one end fixed to the guide member and the other end abutting against the bonding surface of the test piece.

3. The device for applying normal stress to an adhesive interface shear test specimen according to claim 2, characterized in that, It also includes a force sensor, which is coaxially arranged with the guide and the pressure head, and fixed between the guide and the pressure head.

4. The device for applying normal stress to an adhesive interface shear test specimen according to any one of claims 1 to 3, characterized in that, The main body has a through hole at its rear end, and the force-applying component is placed in the through hole and is connected to the guide component at its end.

5. The device for applying normal stress to an adhesive interface shear test specimen according to claim 4, characterized in that, The force-applying component is threadedly fitted to the through hole at the rear end of the main body.

6. The device for applying normal stress to an adhesive interface shear test specimen according to claim 3, characterized in that, The connection between the guide, the sensor, and the pressure head is a threaded connection.

7. A method for applying normal stress to a shear test specimen at an adhesive interface, characterized in that, The method of the adhesive interface shear test specimen normal stress application device according to any one of claims 1 to 6 includes: The guide, force sensor and pressure head are connected coaxially with threads in sequence. The pressure head abuts against the adhesive surface of the test piece, and the force-applying component is screwed into the main body and connected to the end of the guide. The bracket is fixed to the test piece by a connector, and a fastening force is applied by fasteners provided on the bracket, thereby fixing the bracket to the test piece and thus fixing the main body to the test piece; Place both ends of the test piece in the clamping device and fix them in place; After applying a preset normal stress through the force-applying component, the test piece is subjected to a shear load by pulling the clamping device through a universal tensile testing machine.

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