Buckling-restrained device for fracture toughness test thin plate MT sample and test system

Abstract

The utility model relates to an anti-buckling device and a testing system for a fracture toughness test thin plate MT sample, the anti-buckling device comprises two anti-buckling assemblies, the two anti-buckling assemblies respectively comprise a pressing plate contacted with the MT sample and ear plates arranged at the two sides of the pressing plate, and the thin plate-shaped MT sample to be tested is clamped between the two pressing plates; a crack observation groove penetrating through the thickness direction of the pressing plate is formed in the middle of the pressing plate and is used for observing a prefabricated crack on an MT sample; the fastening assembly penetrates through the buckling-restrained assemblies in the thickness direction of the MT sample and is used for fastening and clamping the MT sample between the buckling-restrained assemblies; and the antifriction assembly is arranged between the anti-buckling assembly and the MT sample. Compared with the prior art, the device can effectively prevent the MT sample piece from buckling in the fracture toughness test process, and has the advantages of simplicity in installation, independent support, convenience in crack observation and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of material testing devices, in particular to an anti-buckling device and a testing system for a fracture toughness test thin plate MT specimen. Background Art

[0002] Fracture toughness tests are an important test method in the field of materials engineering, used to evaluate the fracture properties and crack behavior of materials. They play an important role in engineering design, fatigue analysis and material selection. In such tests, center-cracked tensile specimens (MT specimens) are usually subjected to applied forces or pressures to simulate the load conditions in real applications. However, the buckling behavior of MT specimens during testing may invalidate the test results.

[0003] The existing anti-buckling devices basically adopt I-shaped anti-buckling devices (such as CN 216955556 U, CN211740896U), which are mainly used for small-sized long strip material specimens for fatigue specimens. The anti-buckling fixture is often rigidly attached to the specimen without an independent support system, and the prefabricated cracks of the MT specimen cannot be effectively observed. Therefore, it is almost unsuitable for large-sized MT specimens for fracture toughness tests.

[0004] Therefore, a new anti-buckling device for MT specimens in fracture toughness tests is needed to effectively prevent the specimens from buckling during the test, so as to improve the reliability and accuracy of the fracture toughness test results. Utility Model Content

[0005] The utility model aims to solve the problem that the existing anti-buckling device is not suitable for MT specimens of fracture toughness test and to provide an anti-buckling device and a test system for MT specimens of fracture toughness test thin plates.

[0006] The purpose of the utility model can be achieved through the following technical solutions:

[0007] An anti-buckling device for a fracture toughness test thin plate MT specimen, comprising:

[0008] Buckling prevention components, both of which include a pressing plate in contact with the MT specimen and ear plates arranged on both sides of the pressing plate, and the thin plate-shaped MT specimen to be tested is clamped between the two pressing plates; a crack observation groove is opened in the middle of the pressing plate and runs through the thickness direction thereof, for observing prefabricated cracks on the MT specimen;

[0009] A fastening component, which penetrates the anti-buckling component along the thickness direction of the MT specimen and is used to fasten and clamp the MT specimen between the anti-buckling components;

[0010] The friction reduction assembly is arranged between the anti-buckling assembly and the MT specimen.

[0011] Furthermore, the MT sample is a thin plate of aluminum alloy material, polymer material or other composite material.

[0012] Furthermore, a side of the pressing plate in contact with the MT sample is provided with a centering groove for installing the MT sample along the length direction, and the MT sample is clamped in a space formed between the centering grooves of the two pressing plates.

[0013] Furthermore, the pressure plate and the ear plate of the anti-buckling assembly are integrally formed.

[0014] Furthermore, the material of the anti-buckling component includes one of titanium alloy, aluminum alloy or carbon steel.

[0015] Furthermore, the anti-buckling assembly is provided with a plurality of ear plates at equal intervals along the length direction.

[0016] Furthermore, the ear plates of the anti-buckling assembly are each provided with bolt holes for the fastening assembly to pass through.

[0017] Furthermore, the fastening assembly includes a bolt and a nut matching the bolt, and the bolt passes through the bolt hole and is fastened by the nut.

[0018] Furthermore, a gasket is provided between the nut and the bolt hole, and the bolt penetrates the gasket and is then matched with the nut.

[0019] Furthermore, the crack observation groove is a cross-shaped structure, and the lateral length of the cross-shaped structure is greater than the length of the prefabricated crack, which can meet the observation needs during the crack growth process.

[0020] Furthermore, a plurality of anti-friction component positioning grooves which do not penetrate the thickness direction of the MT sample are formed along the length direction of the pressing plate on the side in contact with the MT sample, and the anti-friction component is installed in the anti-friction component positioning grooves.

[0021] Furthermore, the friction reduction assembly has a plurality of evenly distributed positioning grooves to effectively reduce the negative impact of friction on the MT specimen during a long test.

[0022] Furthermore, the friction reduction component is a needle roller bearing, preferably a 2 mm needle roller bearing.

[0023] The utility model also provides a fracture toughness test system, which comprises the anti-buckling device of the fracture toughness test thin plate MT specimen, wherein the anti-buckling components of the anti-buckling device are installed in pairs on the clamping block of the fatigue testing machine.

[0024] Furthermore, the fracture toughness test system also includes an extensometer installed in the crack observation slot for measuring the length change of the prefabricated crack.

[0025] Furthermore, the extensometer is an open displacement gauge (COD).

[0026] Compared with the prior art, the utility model has the following beneficial effects:

[0027] (1) The anti-buckling device of the utility model has a pair of anti-buckling components, which can be installed on a fatigue testing machine and clamp the MT specimen to be tested, thereby effectively preventing the MT specimen from buckling during the fracture toughness test and improving the accuracy and repeatability of the test results.

[0028] (2) The anti-buckling device of the utility model is provided with a crack observation groove for observing cracks, and the crack observation groove can also be used to install an extensometer for measuring the crack length.

[0029] (3) The anti-buckling device of the present invention has an anti-buckling assembly that can be independently supported and does not need to be rigidly attached to the material sample to be tested.

[0030] (4) The anti-buckling device of the utility model is provided with a centering groove which is convenient for installing the MT specimen, and can greatly improve the installation efficiency of the device.

[0031] (5) The anti-buckling device of the utility model can be applied to MT specimens of different thicknesses and can be flexibly fastened by fastening components, thus having a wide range of application potentials.

[0032] (6) The anti-buckling device of the utility model is provided with a friction-reducing bearing, which can greatly reduce the negative impact of friction on the MT test during long-term testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the anti-buckling device of the utility model after assembly.

[0034] Figure 2 It is a schematic diagram of the explosion structure of the anti-buckling device of the utility model.

[0035] Figure 3 It is a schematic diagram of the connection between the anti-buckling assembly and the fastening assembly of the anti-buckling device of the utility model.

[0036] Figure 4 The diagrams are the front and back views of the anti-buckling assembly of the anti-buckling device of the utility model.

[0037] Figure 5 It is a structural schematic diagram of the fracture toughness test system of the utility model.

[0038] Figure 6 This is the fitting curve of the crack growth rate test.

[0039] Description of the markings in the figure:

[0040] 1-fatigue testing machine, 11-clamp, 12-MT specimen, 121-prefabricated crack, 2-anti-buckling assembly, 21-pressure plate, 22-ear plate, 221-bolt hole, 23-crack observation groove, 24-centering groove, 25-anti-friction assembly positioning groove, 3-fastening assembly, 31-bolt, 32-nut, 33-gasket, 4-anti-friction assembly, 5-extensometer. DETAILED DESCRIPTION

[0041] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0042] In the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present utility model; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, 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 an indirect connection through an intermediate medium, or it can be a communication between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0043] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0044] Embodiment 1:

[0045] This embodiment provides an anti-buckling device for a fracture toughness test thin plate MT specimen, comprising an anti-buckling component 2 , a fastening component 3 and a friction reduction component 4 .

[0046] The two anti-buckling assemblies 2 of this embodiment each include a pressing plate 21 in contact with the MT specimen 12 and ear plates 22 disposed on both sides of the pressing plate 21, and the thin plate-shaped MT specimen 12 to be tested is clamped between the two pressing plates 22. A crack observation groove 23 is provided in the middle of the pressing plate 21 and runs through the thickness direction thereof, which can be used to observe the prefabricated crack 121 on the MT specimen 12.

[0047] The fastening assembly 3 penetrates through the ear plate 22 of the anti-buckling assembly 2 along the thickness direction of the MT specimen 12 , and is used to fasten and clamp the MT specimen 12 between the anti-buckling assemblies 2 .

[0048] The friction reducing assembly 4 is disposed between the anti-buckling assembly 2 and the MT specimen 12 to reduce the friction between the anti-buckling assembly 2 and the MT specimen 12 .

[0049] Embodiment 2:

[0050] This embodiment provides a specific anti-buckling device for a fracture toughness test thin plate MT specimen, comprising an anti-buckling component 2 , a fastening component 3 and a friction reduction component 4 .

[0051] The two anti-buckling assemblies 2 of this embodiment both include a pressing plate 21 in contact with the MT specimen 12 and ear plates 22 arranged on both sides of the pressing plate 21, and the pressing plate 21 and the ear plates 22 are integrally formed. A side of the pressing plate 21 in contact with the MT specimen 12 is provided with a centering groove 24 for installing the MT specimen 12 along the length direction, and the thin plate-shaped MT specimen 12 to be tested is clamped in the space formed between the centering grooves 24 of the two pressing plates 21. A crack observation groove 23 is provided in the middle of the pressing plate 21 running through the thickness direction thereof, which can be used to observe the prefabricated crack 121 on the MT specimen 12. The crack observation groove 23 is a cross-shaped structure, and the lateral length of the cross-shaped structure is greater than the length of the prefabricated crack 121, which can meet the observation needs during the crack growth process.

[0052] The buckling prevention assembly 2 is provided with a plurality of ear plates 22 at equal intervals along the length direction. The ear plates 22 are each provided with a bolt hole 221 for the fastening assembly 3 to pass through. The fastening assembly 3 includes a bolt 31 and a nut 32 matching the bolt 31. The bolt 31 passes through the bolt hole 221 and is fastened by the nut 32. A gasket 33 is further provided between the nut 32 and the bolt hole 221. The bolt 31 passes through the gasket 33 and is connected with the nut 32, so that the MT specimen 12 can be fastened and clamped between the buckling prevention assembly 2.

[0053] The friction reduction component 4 is arranged between the anti-buckling component 2 and the MT specimen 12, and is used to reduce the friction between the anti-buckling component 2 and the MT specimen 12. Specifically, a plurality of friction reduction component positioning grooves 25 that do not penetrate the thickness direction of the MT specimen 12 are provided along the length direction on the side of the pressure plate 21 that contacts the MT specimen 12, and the friction reduction component 4 is installed in the friction reduction component positioning grooves 25. The friction reduction component 4 of this embodiment is a needle bearing, so that the friction force of the anti-buckling device of this embodiment on the MT specimen 12 is small, which greatly avoids the influence of excessive friction on the test results.

[0054] Embodiment 3:

[0055] The present embodiment provides a fracture toughness test system, which includes the anti-buckling device of the fracture toughness test thin plate MT specimen described in Example 2 and a fatigue testing machine 1 (MTS Landmark). The anti-buckling components 2 of the anti-buckling device are installed in pairs on the platform of the clamping block 11 of the fatigue testing machine 1. The two ends of the MT specimen 12 are clamped by the upper and lower clamping blocks 11 respectively. The fracture toughness test system of the present embodiment also includes an extensometer 5 installed in the crack observation groove 23, which is used to measure the length change of the prefabricated crack 121. The extensometer 5 used in the present embodiment is an open displacement gauge (model MTS 632.02F-20). Since the crack observation groove 23 is a cross-shaped structure, the longitudinal part of the cross-shaped structure can be used to install the open displacement gauge. The anti-friction component 4 of the present embodiment is a 2mm needle bearing.

[0056] This embodiment uses the fracture toughness test system to conduct the following crack growth rate test on the MT sample 12. Figure 5 As shown, the anti-buckling device and the MT specimen 12 are assembled, and the opening displacement gauge is installed on the wedge-shaped blade of the notch of the fatigue testing machine 1.

[0057] The following experimental parameters were set: the thickness of the MT specimen 12 was 4.94 mm, the size was 400 × 100 mm, and the material was 7075 aluminum alloy. The loading direction of the fatigue testing machine 1 was axial loading. The test frequency was 8 Hz, the waveform was a sine wave, the stress ratio was R = -1, and the pre-crack period was Pre-crack period F final =14.7kN, the pre-crack length is 2mm. The initial load of the crack growth rate test is F during the pre-crack period. final =14.7kN. The test frequency is 8Hz, the loading waveform is a sine wave, the stress ratio R is -1, and the test termination condition is: the final crack length ≥50mm.

[0058] This embodiment uses the compliance method to measure the crack length. The compliance method has high measurement accuracy, and the detection process is automatic and continuous, which is convenient for realizing closed-loop control of mechanical parameters, such as constant K control and reduced K control; the detected crack length can represent the average value of the crack front. During the test, as the crack expands forward, the opening displacement measured by the open displacement gauge also changes. Through the computer data acquisition system, the force and displacement data during one or more load cycles are collected and calculated in real time to obtain the crack length under the current number of cycles.

[0059] The test data of the above test are shown in Table 1, and the aN curve and da / dn fitting curve are shown in Figure 6 a and 6b. The fitting results are:

[0060] da / dN=9.297×10 -8 ΔK3.456 ,R 2 =0.99

[0061] Table 1 da / dN-ΔK test data

[0062]

[0063] Through the test of this embodiment, the aN curve of the negative stress ratio of the MT specimen and the da / dN curve equation were successfully obtained, which provided real and reliable test data for subsequent CAE simulation calculations and optimization of processing and production processes, and has important engineering practical value.

[0064] The above description of the embodiments is to facilitate the understanding and use of the utility model by those skilled in the art. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the utility model is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the utility model without departing from the scope of the utility model should be within the scope of protection of the utility model.

Claims

1. An anti-buckling device for a fracture toughness test thin plate MT specimen, characterized in that: include: Anti-buckling assemblies (2), each of the two anti-buckling assemblies (2) comprising a pressing plate (21) in contact with the MT specimen (12) and ear plates (22) arranged on both sides of the pressing plate (21), the thin plate-shaped MT specimen (12) to be tested is clamped between the two pressing plates (21); a crack observation groove (23) is provided in the middle of the pressing plate (21) and runs through the thickness direction thereof, for observing the prefabricated crack (121) on the MT specimen (12); A fastening component (3) which penetrates the anti-buckling component (2) along the thickness direction of the MT specimen (12) and is used to fasten and clamp the MT specimen (12) between the anti-buckling components (2); The friction reduction component (4) is arranged between the anti-buckling component (2) and the MT specimen (12).

2. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: A centering groove (24) for installing the MT sample (12) is provided along the length direction on the side of the pressing plate (21) in contact with the MT sample (12). The MT sample (12) is clamped in the space formed between the centering grooves (24) of the two pressing plates (21).

3. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: The pressing plate (21) and the ear plate (22) of the anti-buckling assembly (2) are integrally formed.

4. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: The anti-buckling component (2) is provided with a plurality of ear plates (22) at equal intervals along the length direction.

5. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: The ear plates (22) of the anti-buckling components (2) are each provided with bolt holes (221) for the fastening components (3) to penetrate.

6. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 5, characterized in that: The fastening assembly (3) comprises a bolt (31) and a nut (32) matching the bolt (31); the bolt (31) passes through the bolt hole (221) and is fastened by the nut (32).

7. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: The crack observation groove (23) is a cross-shaped structure, and the lateral length of the cross-shaped structure is greater than the length of the prefabricated crack (121).

8. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: A plurality of anti-friction component positioning grooves (25) which do not penetrate the thickness direction of the MT sample (12) are provided along the length direction on a side of the pressing plate (21) in contact with the MT sample (12), and the anti-friction component (4) is installed in the anti-friction component positioning grooves (25).

9. The anti-buckling device for a fracture toughness test thin plate MT specimen according to claim 1, characterized in that: The friction reducing component (4) is a needle roller bearing.

10. A fracture toughness test system, characterized in that: An anti-buckling device for a fracture toughness test thin plate MT specimen according to any one of claims 1 to 9, wherein the anti-buckling components (2) of the anti-buckling device are installed in pairs on a clamping block (11) of a fatigue testing machine (1); The fracture toughness test system also includes an extensometer (5) installed in the crack observation slot (23) for measuring the length change of the prefabricated crack (121).

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