Mini wedge splitting test device and method for testing fracture parameters of quasi-brittle materials

Abstract

This invention discloses a micro-wedge splitting test device and a method for testing fracture parameters of quasi-brittle materials. The device includes a micro-sample, a groove on the upper part of the micro-sample, and a force-transmitting component. The force-transmitting component comprises a wedge, a roller, and a force-transmitting block connected in sequence. Compared with existing standard wedge splitting test devices, the ratio of the fracture cross-section to the volume of the micro-sample increases by more than 1.8 times, and the ratio of the shoulder width to half-width of the micro-sample decreases by less than 10%. By controlling the ratio of fracture cross-section to sample volume and the ratio of sample shoulder width to sample half-width, the device can reduce the size of the wedge splitting test device while ensuring that the crack forms and propagates stably at the center. Furthermore, by limiting the load rate to approximately 0.1 mm / min, the device ensures stable energy release during the micro-splitting test, making the micro-wedge splitting test device suitable for testing the fracture performance of small-sized functional components.

Description

Technical Field

[0001] This invention relates to the field of wedge splitting device technology, and in particular to a micro wedge splitting test device and a method for testing fracture parameters of quasi-brittle materials. Background Technology

[0002] Accurate measurement of material strength and fracture energy is crucial for new material development, quality control, service safety evaluation, and numerical simulation parameter acquisition. For quasi-brittle materials such as refractories, concrete, and rocks, tensile strength is much lower than compressive strength, making the development of Mode I tensile failure testing methods a long-standing focus in this field. Tensile tests can be divided into direct and indirect methods. Due to the difficulty in sample preparation, complex fixtures, and the challenge in ensuring load coaxiality in direct tensile testing, indirect tensile testing is widely used. Among these methods, the wedge splitting test is a widely applied indirect tensile testing method, offering the following advantages: by using a larger block specimen, the fracture section / specimen volume ratio is increased; by employing force-transmitting components such as wedges and rollers, longitudinal loading is converted into transverse load, reducing the elastic energy stored within the specimen, ensuring stable crack propagation during the fracture process of quasi-brittle materials, and reducing the restriction of the specimen boundary on the development of the fracture process zone, which is beneficial for the accurate measurement of fracture parameters.

[0003] However, in order to achieve a stable fracture process, the existing standard wedge splitting test device and the existing wedge splitting device used for testing are generally large in size (thickness of at least 65mm). For test samples of some small parts of smelting continuous casting functional components (such as long nozzles with a wall thickness of less than 30mm), the material properties obtained by using large-size splitting tests are significantly different from their actual service mechanical properties, which cannot meet the actual engineering application requirements.

[0004] In view of this, it is necessary to design a micro wedge splitting test device and a method for testing fracture parameters of quasi-brittle materials to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a micro-wedge splitting test device and a method for testing fracture parameters of quasi-brittle materials that can solve the engineering problem of large differences between the service performance and intrinsic properties of small-sized functional components.

[0006] To achieve the above-mentioned objectives, this invention provides a micro wedge splitting test device, comprising a micro specimen, a groove located on the upper part of the micro specimen, and a force transmission component placed in the groove. The force transmission component includes a wedge block, a roller, and a force transmission block connected in sequence. Compared with the existing standard wedge splitting test device, the ratio of the fracture cross section to the volume of the micro specimen is increased by more than 1.8 times, and the ratio of the shoulder width to half width of the micro specimen is reduced by less than 10%. The ratio of the fracture cross section to the volume of the existing standard wedge splitting test device is 0.0066 / mm, and the ratio of the shoulder width to half width of the specimen is 0.76.

[0007] As a further improvement of the present invention, the micro sample has a thickness of 28-32 mm, a length of 48-52 mm, and a width of 48-52 mm.

[0008] As a further improvement of the present invention, the diameter of the roller is 3-4 mm and the thickness of the force transmission block is ≤5 mm.

[0009] As a further improvement of the present invention, the angle between the inclined surface of the force transmission block and the vertical direction is 5°.

[0010] As a further improvement of the present invention, the wedge angle of the wedge is 10°.

[0011] As a further improvement of the present invention, the height and width of the groove are 11-13mm and 15-17mm, respectively.

[0012] As a further improvement of the present invention, the length and width of the pre-fabricated initial crack of the micro sample are 5-7 mm and 1.5-2.5 mm, respectively.

[0013] As a further improvement of the present invention, a support strip is provided at the bottom of the micro sample.

[0014] This invention also provides a method for testing fracture parameters of quasi-brittle materials, which involves conducting tests using the micro-wedge splitting test device described in any of the above technical solutions, and includes the following steps:

[0015] S1. Place a support bar directly below the central axis of the testing machine, and then place the micro sample on the support bar so that its two sides are suspended in the air, so as to ensure that the two sides of the micro sample can deflect freely without being constrained by external forces during the splitting process.

[0016] S2. Place force transmission blocks on the left and right sides of the groove, and ensure that their outer walls are in close contact with the inner side of the groove; place rollers and wedges on the inner side of the force transmission blocks respectively.

[0017] S3. The test machine pressure head slowly descends and makes slight contact with the upper end of the wedge to achieve the predetermined inlet force;

[0018] S4. Set the predetermined loading speed, start the test, and record the longitudinal displacement δ. V -load F V curve;

[0019] S5. Stop the test when the load after the peak decreases to 15% of the peak value.

[0020] As a further improvement of the present invention, the inlet force is 18-22N and the loading speed is 0.08-0.12mm / min.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention increases the ratio of fracture cross-section to specimen volume by at least 1.8 times compared to existing standard wedge splitting test devices, and reduces the ratio of specimen shoulder width to specimen half-width by less than 10% compared to existing standard wedge splitting test devices. This allows for crack formation at the center of the specimen, rather than fracture at the shoulder, while minimizing the size of the wedge splitting test device, and ensures stable crack propagation. Furthermore, by limiting the load rate to approximately 0.1 mm / min, stable energy release during the micro-splitting test is guaranteed, resulting in a stable post-peak region and fracture energy release process. This makes the micro-wedge splitting test device of this invention suitable for performance testing of small-sized functional components. Moreover, the fracture parameters obtained through the test method of this invention show no significant difference from their actual service mechanical properties, meeting the needs of practical engineering applications.

[0023] 2. The quasi-brittle material fracture parameter testing method of the present invention has good test normalization and simple operation. In particular, it is significantly superior to the existing wedge splitting test method in the study of the actual service mechanical properties of small-sized functional components. It can greatly help the development of new materials, service safety evaluation and numerical simulation parameter acquisition related to small-sized functional components. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the device in Example 1.

[0025] Figure 2 This is a schematic diagram of the device dimensions for Example 1.

[0026] Figure 3 This is a schematic diagram of the force transmission component dimensions in Example 1.

[0027] Figure 4 The displacement-load curve results are for Example 1.

[0028] Figure Labels

[0029] 1. Miniature sample; 2. Wedge; 3. Roller; 4. Force transmission block; 5. Support bar. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0032] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0033] This invention provides a micro wedge splitting test device, comprising a micro specimen 1, a groove located on the upper part of the micro specimen 1, and a force transmission component placed in the groove. The force transmission component includes a wedge block 2, a roller 3, and a force transmission block 4 connected in sequence. Compared with the existing standard wedge splitting test device, the ratio of the fracture cross section to the volume of the micro specimen 1 is increased by more than 1.8 times, and the ratio of the shoulder width to half width of the micro specimen 1 is reduced by less than 10%. The ratio of the fracture cross section to the volume of the existing standard wedge splitting test device is 0.0066 / mm, and the ratio of the specimen shoulder width to half width of the specimen is 0.76.

[0034] Specifically, the micro sample 1 has a thickness of 28-32 mm, a length of 48-52 mm, and a width of 48-52 mm; the height and width of the groove are 11-13 mm and 15-17 mm, respectively; and the length and width of the pre-fabricated initial crack are 5-7 mm and 1.5-2.5 mm, respectively.

[0035] Specifically, the wedge angle of wedge 2 is 10°, the diameter of roller 3 is 3-4mm, the angle of force transmission block 4 is 5°, and the thickness of force transmission block 4 is ≤5mm. By controlling the size of roller 3, it is possible to avoid the frictional force from being too small and the roller 3 from deforming, which would have an adverse effect on the calculation of fracture parameters.

[0036] Specifically, there are two rollers 3, and the wedge block 2 is located at the center of the two rollers 3 and is connected to the two rollers 3; there are two force transmission blocks 4, the left roller is connected to the micro sample 1 through the left force transmission block, and the right roller is connected to the micro sample 1 through the right force transmission block.

[0037] Specifically, a support strip 5 is provided at the bottom of the micro sample 1.

[0038] This invention also provides a method for testing fracture parameters of quasi-brittle materials, which involves conducting tests using the micro-wedge splitting test device described in any of the above technical solutions, and includes the following steps:

[0039] S1. Place the support bar 5 directly below the central axis of the testing machine, and then place the micro sample 1 on the support bar 5 so that its two sides are suspended in the air, so as to ensure that the two sides of the micro sample 1 can deflect freely without being constrained by external forces during the splitting process.

[0040] S2. Place force transmission blocks 4 on the left and right sides of the groove, and make their outer walls fit tightly against the inner side of the groove; place rollers and wedges 2 on the inner side of the force transmission blocks 4 respectively.

[0041] S3. The pressure head of the test machine slowly descends and makes slight contact with the upper end of the wedge 2 to achieve an inlet force of 18-22N;

[0042] S4. Set the predetermined loading speed, start the test, and record the longitudinal displacement δ. V -load F V curve;

[0043] S5. Stop the test when the load after the peak decreases to 15% of the peak value.

[0044] Specifically, in step S4, the loading speed is 0.08-0.12 mm / min.

[0045] Specifically, the lateral load F is obtained by converting the longitudinal load. H F H The calculation formula is:

[0046]

[0047] Where β is the wedge angle, equal to 10°; F V For longitudinal loads.

[0048] Specifically, through the maximum lateral load F H,max Calculate tensile strength σ NT , σ NT The calculation formula is as follows:

[0049]

[0050] Where b and h are the height and width of the fracture section, respectively, and are constants; y is the vertical distance between the roller and the center of gravity of the micro specimen 1.

[0051] Specifically, the fracture energy G can be obtained by dividing the area under the displacement-load curve by the fracture section. F The energy required to form a fracture surface per unit area, G, is obtained. F The calculation formula is as follows:

[0052]

[0053] Specifically, the characteristic length l of the material is calculated using tensile strength and fracture energy. ch :

[0054]

[0055] Where E is the elastic modulus, and the smaller the characteristic length value, the higher the brittleness of the material.

[0056] The following describes the micro wedge-shaped splitting test device and the method for testing fracture parameters of quasi-brittle materials provided by the present invention with reference to specific embodiments.

[0057] Example 1

[0058] This embodiment provides a miniature wedge-shaped splitting test device, such as Figures 1-3 As shown, the micro sample 1 has external dimensions of 50mm × 50mm × 30mm, with a groove height and width of 12mm and 16mm respectively, and a pre-fabricated initial crack length and width of 6mm and 2mm respectively; the wedge block 2 in the force transmission component ( Figure 3 a) The wedge angle is 10°, and the roller 3 ( Figure 3 c) The diameter is 3.5mm, and the force transmission block 4 ( Figure 3 b) The angle between the inclined plane and the vertical direction is 5°, and the thickness of the force transmission block 4 is 5mm.

[0059] The fracture cross section of the existing standard wedge splitting test device is 4224 mm. 2 The fracture cross section / sample volume ratio was 0.0066 / mm, the initial crack / sample width ratio was 12:100, the sample shoulder width / sample half-width ratio was 0.76, and the loading rate was 0.5mm / min.

[0060] In this embodiment, the fracture cross section of the micro wedge splitting test device is: (50-6-12)*30=960 (mm) 2 The ratio of fracture section to sample volume is 960 / (50*50*30)=0.0128 / mm; the ratio of initial crack to sample width is 6:50; the sample shoulder width is (50-16) / 2=17(mm); the ratio of sample shoulder width to sample half width is 17 / 25=0.68.

[0061] Compared with the standard wedge splitting test device, although the fracture cross section of the micro wedge splitting test device is only 23% of that of the standard wedge splitting test device, it maintains the initial crack to specimen width ratio unchanged, increases the fracture cross section to specimen volume ratio by about 2 times, reduces the specimen shoulder width to specimen width ratio by only 10%, and reduces the loading rate by 0.1 mm / min. Thus, while reducing the size of the wedge splitting test device, it ensures that the crack forms in the center rather than fractures at the specimen shoulder and propagates stably.

[0062] This embodiment also provides a method for testing fracture parameters of quasi-brittle materials. The test materials are three groups of refractory ceramic materials A, B, and C for continuous casting functional components in metallurgical processes, with their brittleness increasing sequentially. A and B are alumina-carbon composite materials, and C is a zirconia-carbon composite material. Quasi-brittle material fracture parameter tests are conducted on the three groups of materials, with five parallel tests for each type. The aforementioned micro-wedge splitting test device is used for detection, including the following steps:

[0063] S1. Place the support bar 5 directly below the central axis of the testing machine, and then place the micro sample 1 on the support bar 5 so that its two sides are suspended in the air, so as to ensure that the two sides of the micro sample 1 can deflect freely without being constrained by external forces during the splitting process.

[0064] S2. Place force transmission blocks 4 on the left and right sides of the groove, and make their outer walls fit tightly against the inner side of the groove; place rollers and wedges 2 on the inner side of the force transmission blocks 4 respectively.

[0065] S3. The pressure head of the test machine slowly descends and makes slight contact with the upper end of the wedge 2 to achieve an inlet force of 20N;

[0066] S4. Set the loading speed to 0.1 mm / min, start the test, and record the longitudinal displacement δ. V -load F V curve;

[0067] S5. Stop the test when the load after the peak decreases to 15% of the peak value.

[0068] Where b and h are 30mm and 32mm respectively, y is 32mm, and the E values ​​for materials A, B and C are 13.9GPa, 16.6GPa and 9.7GPa respectively.

[0069] Its displacement-load curve is as follows Figure 4 As shown in Table 1, the calculation results of the fracture parameters are as follows.

[0070] Table 1. Calculation results of fracture parameters for three groups of refractory ceramic materials A, B, and C.

[0071] <![CDATA[F v，max (N)]]> <![CDATA[F H，max (N)]]> <![CDATA[σ NT (MPa)]]> <![CDATA[G F N / m)]]> <![CDATA[1 ch (mm)]]> A 116.31±7.79 664.65±44.52 4.90±0.38 203.01±15.38 117.30±15.38 B 98.34±10.00 561.93±57.17 4.23±0.29 124.94±19.04 116.03±21.66 C 92.67±4.47 529.55±25.54 3.65±0.2 81.31±11.15 58.96±5.41

[0072] Depend on Figure 3 It is known that the displacement-load curve obtained by using the micro wedge splitting test device of the present invention to test small-sized functional components is a smooth curve, and the test results are relatively stable. The refractory ceramic material shows a stable crack propagation peak-back region, and the material fracture parameters can be effectively obtained. Moreover, the fracture parameter results of the three groups of quasi-brittle materials are consistent with the expected service performance. This avoids the situation where the fracture cross section of the wedge splitting test device is significantly reduced compared with the existing standard wedge splitting test device, and the crack propagation is unstable during the test process and cracks are formed at the shoulder end due to the difference between the fracture interface and the sample volume ratio or the ratio of the sample shoulder width and the sample width. This ensures the accuracy of the test.

[0073] In summary, the micro wedge splitting test device and the method for testing fracture parameters of quasi-brittle materials disclosed in this invention, by controlling the ratio of fracture cross-section to sample volume to be at least 1.8 times larger than that of existing standard wedge splitting test devices, and by reducing the ratio of sample shoulder width to sample half-width by less than 10% compared to existing standard wedge splitting test devices, can ensure that cracks form in the center of the sample rather than at the shoulder, and that the cracks propagate stably, while reducing the size of the wedge splitting test device. Furthermore, by limiting the load rate to approximately 0.1 mm / min, the stable release of energy during the micro-splitting test process can be guaranteed, resulting in a stable post-peak region and fracture energy release process. This makes the micro wedge splitting test device of this invention suitable for performance testing of small-sized functional components, and the fracture parameters obtained by the test method of this invention do not differ significantly from their actual service mechanical properties, meeting the needs of practical engineering applications.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A miniature wedge-shaped splitting test device, characterized in that: The device includes a micro-sample, a groove on the upper part of the micro-sample, and a force-transmitting component placed in the groove. The force-transmitting component includes a wedge, a roller, and a force-transmitting block connected in sequence. Compared with the existing standard wedge splitting test device, the ratio of the fracture cross section to the volume of the micro-sample is increased by more than 1.8 times, and the ratio of the shoulder width to half width of the micro-sample is reduced by less than 10%. The ratio of the fracture cross section to the volume of the existing standard wedge splitting test device is 0.0066 / mm, and the ratio of the shoulder width to half width of the sample is 0.

76. The micro sample has a thickness of 28-32 mm, a length of 48-52 mm, and a width of 48-52 mm. The micro sample is provided with a support strip at the bottom.

2. The micro wedge-shaped splitting test device according to claim 1, characterized in that: The roller diameter is 3-4mm, and the thickness of the force transmission block is ≤5mm.

3. The micro wedge-shaped splitting test device according to claim 2, characterized in that: The angle between the inclined surface of the force transmission block and the vertical direction is 5°.

4. The micro wedge-shaped splitting test device according to claim 2, characterized in that: The wedge angle of the wedge is 10°.

5. The micro wedge-shaped splitting test device according to claim 1, characterized in that: The height and width of the groove are 11-13mm and 15-17mm, respectively.

6. The micro wedge-shaped splitting test device according to claim 5, characterized in that: The initial crack length and width of the micro-sample were 5-7 mm and 1.5-2.5 mm, respectively.

7. A method for testing fracture parameters of quasi-brittle materials, characterized in that, The test is conducted using the micro wedge-shaped splitting test apparatus according to any one of claims 1 to 6, comprising the following steps: S1. Place a support bar directly below the central axis of the testing machine, and then place the micro sample on the support bar so that its two sides are suspended in the air, so as to ensure that the two sides of the micro sample can deflect freely without being constrained by external forces during the splitting process. S2. Place force transmission blocks on the left and right sides of the groove, and ensure that their outer walls are in close contact with the inner side of the groove; place rollers and wedges on the inner side of the force transmission blocks respectively. S3. The test machine pressure head slowly descends and makes slight contact with the upper end of the wedge to achieve the predetermined inlet force; S4. Set the predetermined loading speed, start the test, and record the longitudinal displacement δV-load FV curve; S5. Stop the test when the load after the peak decreases to 15% of the peak value; The inlet force is 18-22N, and the loading speed is 0.08-0.12mm / min.

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