A method for evaluating the fracture mechanics performance of a water-soluble brittle solid material

Abstract

The method for evaluating the fracture mechanics performance of the water-soaked brittle solid material of the present application comprises the following steps: 1. A group of cuboid brittle solid material samples are prepared, and the samples are immersed in water. After the immersion is completed, the samples with different immersion times are selected for weighing, and then the samples with different water contents are selected; 2. The samples with different water contents in step 1 are selected, and the relationship curve between the uniaxial compression stress and strain of the brittle solid material samples and the initial density of the micro-defects of the samples under different water contents are measured; 3. The samples with different water contents in step 1 are selected, and the sliding friction coefficients of the brittle solid material samples with different water contents are determined; 4. The brittle solid samples containing cracks are prepared, and the fracture toughness of the brittle solid material with different water contents is measured; and 5. Based on the above steps, the fracture strength of the brittle solid material samples under the action of different water contents after being soaked in water is determined.

Description

Technical Field

[0001] This invention relates to the field of mechanical engineering technology for brittle solid materials, and in particular to a method for evaluating the fracture mechanical properties of brittle solid materials that have been soaked in water. Background Technology

[0002] Materials are closely related to human survival and development. From the most basic human needs of clothing, food, shelter and transportation to high-tech products, from basic tools used in production and daily life to complex satellites and missiles, all kinds of materials are indispensable.

[0003] The most prominent characteristic of brittle materials is their high brittleness, and they generally have high hardness. They are mainly represented by ceramics, stone, and glass. Brittle solid materials are among the most important materials in human production practices. Examples include concrete in building construction, rock in underground construction, ceramics in machinery manufacturing, and glass, which is commonly found in daily life.

[0004] During the application of these brittle materials, they are often subjected to different mechanical loads and may also be affected by water environment to varying degrees. Under the combined action of load and water environment, as the water content of brittle solid materials increases after soaking in water, the degree of internal damage to the material increases, which in turn leads to a weakening of the strength of the brittle solid materials and makes them more prone to fracture.

[0005] Internal damage to brittle solid materials is often amplified, leading to increased safety hazards in engineering structures made of such materials. For example, the load-bearing capacity of concrete walls in buildings is greatly reduced after they are soaked in water and corroded; the stability of underground tunnel structures is weakened after the rocks around them are corroded by groundwater.

[0006] In the existing technology, there is no specific method for evaluating the fracture mechanical properties of brittle solid materials after soaking in water, nor is it possible to evaluate the fracture mechanical properties of brittle materials after soaking in water in engineering practice; therefore, it has no practical engineering significance.

[0007] Therefore, those skilled in the art are dedicated to developing a method for evaluating the fracture mechanical properties of water-brittle solid materials, aiming to address the shortcomings of existing technologies. Summary of the Invention

[0008] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is that there is currently no specific method for evaluating the fracture mechanical properties of brittle solid materials after soaking in water, and it is also impossible to evaluate the fracture mechanical properties of brittle materials after soaking in water in engineering practice; therefore, it has no practical engineering significance.

[0009] To achieve the above objectives, the present invention provides a method for evaluating the fracture mechanical properties of water-brittle solid materials, comprising the following steps:

[0010] Step 1: Prepare a set of rectangular brittle solid material samples. Immerse the samples in water. After immersion, weigh the samples with different immersion times, and then select samples with different moisture contents.

[0011] Step 2: Select samples with different moisture contents from Step 1, and measure the uniaxial compressive stress-strain relationship curve and the initial density of micro-defects of the brittle solid material samples under different moisture contents.

[0012] Step 3: Select samples with different moisture contents from Step 1 and determine the sliding friction coefficient of brittle solid material samples with different moisture contents.

[0013] Step 4: Pre-fabricate brittle solid samples containing cracks and measure the fracture toughness of brittle solid materials with different moisture contents.

[0014] Step 5: Based on the above steps, complete the determination of the fracture strength of brittle solid material samples under different moisture contents after soaking in water.

[0015] Step 1: Prepare a set of rectangular brittle solid material samples. Immerse the samples in water. After immersion, weigh the samples with different immersion times, and then select samples with different moisture contents.

[0016] In step 1, brittle solid materials after different soaking times are weighed to determine the degree of weight change of the brittle solid materials before and after soaking. The weight difference is the weight of water. Then, the ratio of the weight of water to the weight of the dried brittle solid material sample is the moisture content ω.

[0017] Step 2: Select samples with different moisture contents from Step 1, and measure the uniaxial compressive stress-strain relationship curve and the initial density of micro-defects of the brittle solid material samples under different moisture contents.

[0018] In step 2, the uniaxial compressive stress-strain relationship curves of brittle solid material samples with different moisture contents are obtained by measuring with conventional compression testing instruments.

[0019] In step 2, the initial density of microdefects in samples with different moisture contents is determined using an electron microscope scanning instrument. The volume of internal defects in brittle solid materials with different moisture contents is determined, and the ratio of this volume to the sample volume is the initial density of microdefects D0 of the sample. The relationship between this initial density and moisture content is as follows:

[0020] D0(ω)=a1ω+a2 (1)

[0021] Step 3: Select samples with different moisture contents from Step 1 and determine the sliding friction coefficient of brittle solid material samples with different moisture contents.

[0022] In step 3, the sliding friction coefficient of samples with different moisture contents is determined using two identical, smooth-surfaced brittle solid materials through a direct shear test instrument. The relationship between the friction coefficient and the moisture content is then established as follows:

[0023] μ(ω)=c1ω+c2 (2)

[0024] Step 4: Pre-fabricate brittle solid samples containing cracks and measure the fracture toughness of brittle solid materials with different moisture contents.

[0025] Step 4 involves preparing a brittle solid sample with cracks and using a three-point bending test instrument to measure the fracture toughness K of the brittle solid material with different moisture contents. IC The relationship between fracture toughness and water content is determined as follows:

[0026] K IC (ω)=b1-b2ω+b3ω 2 (3)

[0027] Step 5: Based on the above steps, complete the determination of the fracture strength of brittle solid material samples under different moisture contents after soaking in water.

[0028] In step 5, based on the theory of solid damage and fracture mechanics, the stress-strain relationship of brittle solid materials considering different moisture contents is determined as follows:

[0029] f(σ1,ε1,ω)=σ1-K IC (ω) / (πa 2 A1A2)=0 (4)

[0030] In the formula:

[0031]

[0032]

[0033] A3=a(D0(ω)) -1 / 3 {1-exp[-(ε1 / ε0) m ]} 1 / 3 -a (7)

[0034]

[0035] In step 5, the parameter D0(ω) in equation (7) can be determined by equation (1) in step 2;

[0036] In step 5, the parameter K in equation (4) IC (ω) can be determined by equation (3) in step 4;

[0037] In step 5, the parameter μ(ω) in equation (5) can be determined by equation (2) in step 3;

[0038] In step 5, equation (4) states that parameter a is the average size of the initial defects inside the brittle solid material.

[0039] In step 5, equation (5) contains parameters. The initial defect angle, which takes a value greater than 0 and less than 90;

[0040] In step 5, parameter a, The specific value needs to be determined by comparing and analyzing the theoretical and experimental stress-strain relationship curves in step 5 and step 2. When the two are closest, parameter a is determined.

[0041] In step 5, equation (7) states that parameter ε0 is approximately equal to the strain value corresponding to the maximum stress in the stress-strain relationship curve in step 2.

[0042] The parameter m is generally selected as a value of 1, 2, or 3; the parameter β is generally a value greater than 0 and less than 1.

[0043] In step 5, all parameters of a certain brittle solid material are determined. According to step 6, the stress-strain relationship curves of the brittle solid material under different moisture contents are calculated. Then, the deformation and strength characteristics of the brittle solid material soaked in water can be determined. When the brittle solid material is subjected to a load greater than the calculated strength value of the material, the material will fracture. Then, the fracture mechanical properties of the material can be evaluated.

[0044] Furthermore, the initial density of micro-defects in the sample during step 2 is less than 1;

[0045] Furthermore, the specific values ​​of the parameters mentioned above in step 5 can be appropriately adjusted under the above conditions to ensure that the stress-strain relationship curves obtained theoretically and experimentally in step 6 and step 2 are as consistent as possible.

[0046] By adopting the above scheme, the fracture mechanical properties evaluation method for water-soaked brittle solid materials disclosed in this invention has the following advantages:

[0047] (1) The fracture mechanical properties evaluation method of water-soaked brittle solid materials of the present invention establishes a stress-deformation relationship equation of the brittle solid material considering the influence of the internal water content after soaking; according to the equation, the degree of internal damage change of the brittle solid material after soaking can be explained, and the stress-strain relationship of the material can be judged. The fracture mechanical properties of the brittle solid material can be evaluated through this relationship.

[0048] (2) The fracture mechanical properties evaluation method of water-soaked brittle solid materials of the present invention is specifically designed for brittle solid materials after soaking in water. As the water content of brittle solid materials increases after soaking in water, the degree of internal damage to the material increases, which in turn leads to a decrease in the strength of the brittle solid materials and makes them more prone to fracture. The rationality of the method has been verified through experimental examples. The method of the present invention provides support for the safety and stability evaluation of brittle solid materials under different degrees of water immersion environment. It has important engineering practical significance for the evaluation of fracture mechanical properties of water-soaked brittle solid materials.

[0049] In summary, the fracture mechanical properties evaluation method for water-soaked brittle solid materials disclosed in this invention establishes a stress-deformation relationship equation for brittle solid materials considering the influence of internal moisture content after soaking. This equation can determine the stress-strain relationship of the material, and through this relationship, the fracture mechanical properties of brittle solid materials can be evaluated. This provides support for the safety and stability evaluation of brittle solid materials under different degrees of water immersion, and has significant engineering practical implications for evaluating the fracture mechanical properties of water-soaked brittle solid materials.

[0050] The following will further explain the concept, specific technical solution and technical effects of the present invention in conjunction with specific embodiments, so as to fully understand the purpose, features and effects of the present invention. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the process for evaluating the fracture mechanical properties of water-soaked brittle solid materials according to the present invention;

[0052] Figure 2 This is a graph showing the stress-strain test results of sandstone material under two moisture contents in Embodiment 1 of the present invention.

[0053] Figure 3 This is a graph showing the stress-strain theoretical calculation results of sandstone material under two water contents in Embodiment 1 of the present invention.

[0054] Figure 4 This is a comparison curve of theoretical and experimental results of stress and strain of sandstone material under two water contents in Embodiment 1 of the present invention. Detailed Implementation

[0055] The following describes several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, which are described exemplarily, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0056] Example 1: Sandstone was selected as a brittle solid material. After soaking in water, its fracture strength was evaluated.

[0057] As shown in the figure Figure 1 This is a schematic diagram of the process for evaluating the fracture mechanical properties of water-soaked brittle solid materials according to the present invention;

[0058] First, perform step 1: prepare a set of rectangular brittle solid material samples, immerse the samples in water, weigh the samples after immersion for different times, and then select samples with different moisture contents.

[0059] In specific implementation, in this embodiment 1, the operation of step 1 is that there is no limit to the soaking time of the sample, and the soaking time can be freely adjusted;

[0060] In step 1, brittle solid materials after different soaking times are weighed to determine the degree of weight change of the brittle solid materials before and after soaking. The weight difference is the weight of water. Then, the ratio of the weight of water to the weight of the dried brittle solid material sample is the moisture content ω.

[0061] In specific implementation, in this Example 1, two brittle solid material samples with different moisture contents were selected, and the ratio of the length, width and height of the samples was 1:1:2.

[0062] In specific implementation, in this Example 1, the two moisture contents are 1.04% and 3.41%, respectively;

[0063] Then proceed to step 2, select samples with different moisture contents from step 1, and measure the uniaxial compressive stress-strain relationship curve and the initial density of micro-defects of the brittle solid material samples under different moisture contents.

[0064] In step 2, the uniaxial compressive stress-strain relationship curves of brittle solid material samples with different moisture contents are obtained by measuring with conventional compression testing instruments.

[0065] In step 2, the initial density of microdefects in samples with different moisture contents is determined using an electron microscope scanning instrument. The volume of internal defects in brittle solid materials with different moisture contents is determined, and the ratio of this volume to the sample volume is the initial density of microdefects D0 of the sample. The relationship between this initial density and moisture content is as follows:

[0066] D0(ω)=a1ω+a2 (1)

[0067] In specific implementation, in Embodiment 1 of the present invention, the value of the initial density of micro-defects in the sample in step 2 is less than 1;

[0068] Then, step 3 is performed: samples with different moisture contents from step 1 are selected, and the sliding friction coefficient of brittle solid material samples with different moisture contents is determined.

[0069] In step 3, the sliding friction coefficient of samples with different moisture contents is determined using two identical, smooth-surfaced brittle solid materials through a direct shear test apparatus. The relationship between the friction coefficient and the moisture content is then established as follows:

[0070] μ(ω)=c1ω+c2 (2)

[0071] Perform step 4: Pre-fabricate brittle solid samples containing cracks and measure the fracture toughness of brittle solid materials with different moisture contents.

[0072] Step 4 involves preparing a brittle solid sample with cracks and using a three-point bending test instrument to measure the fracture toughness K of the brittle solid material with different moisture contents. IC The relationship between fracture toughness and water content is determined as follows:

[0073] K IC (ω)=b1-b2ω+b3ω 2 (3)

[0074] Finally, step 5 is performed. Based on the above steps, the fracture strength of brittle solid material samples under different moisture contents after soaking in water is determined.

[0075] In step 5, based on the theory of solid damage and fracture mechanics, the stress-strain relationship of brittle solid materials considering different moisture contents is determined as follows:

[0076] f(σ1,ε1,ω)=σ1-K IC (ω) / (πa 2 A1A2)=0 (4)

[0077] In the formula:

[0078]

[0079]

[0080] A3=a(D0(ω)) -1 / 3 {1-exp[-(ε1 / ε0) m ]} 1 / 3 -a (7)

[0081]

[0082] In step 5, the parameter D0(ω) in equation (7) can be determined by equation (1) in step 2;

[0083] In step 5, the parameter K in equation (4) IC (ω) can be determined by equation (3) in step 4;

[0084] In step 5, the parameter μ(ω) in equation (5) can be determined by equation (2) in step 3;

[0085] In step 5, equation (4) states that parameter a is the average size of the initial defects inside the brittle solid material.

[0086] In step 5, equation (5) contains parameters. The initial defect angle, which takes a value greater than 0 and less than 90;

[0087] In step 5, parameter a, The specific value needs to be determined by comparing and analyzing the theoretical and experimental stress-strain relationship curves in step 5 and step 2. When the two are closest, parameter a is determined.

[0088] In step 5, equation (7) states that parameter ε0 is approximately equal to the strain value corresponding to the maximum stress in the stress-strain relationship curve in step 2.

[0089] In specific implementation, the parameters of this embodiment 1 are summarized in Table 1;

[0090] Table 1 Sandstone Parameters

[0091]

[0092] In step 5, all parameters of a certain brittle solid material are determined. According to step 6, the stress-strain relationship curve of the brittle solid material under different moisture contents is calculated, and then the deformation and strength characteristics of the brittle solid material soaked in water can be judged. When the brittle solid material is subjected to a load greater than the calculated strength value of the material, the material will fracture, and then the fracture mechanical properties of the material can be evaluated.

[0093] As shown in the figure Figure 2 This is a graph showing the stress-strain test results of sandstone material under two moisture contents in Embodiment 1 of the present invention.

[0094] from Figure 2 As can be seen, for brittle solid materials with low moisture content, after the axial strain reaches 1.0%, the low moisture content sample can still have strong axial stress when the axial strain is close to 1.25%. However, the sample with a moisture content of 3.41%, that is, the sample with a longer soaking time, reaches the maximum axial tensile force when the axial strain is close to 1.1%. When the axial strain is close to the low moisture content, its axial tensile force has been greatly reduced.

[0095] As shown in the figure Figure 3This is a curve showing the theoretical calculation results of stress and strain of sandstone material under two moisture contents in Embodiment 1 of the present invention. It can be seen from the theoretical curve that as the axial strain gradually increases, the axial stress increases linearly with the increase of axial strain before the axial strain reaches 0.75% at both moisture contents. As the axial strain gradually increases, the axial stress reaches its maximum at approximately the same axial strain at both moisture contents, and then the axial stress decreases with the increase of axial strain.

[0096] As shown in the figure Figure 4 This is a comparison curve of theoretical and experimental results of stress and strain of sandstone material under two moisture contents in Embodiment 1 of the present invention. By using this method, the actual experimental curve and the theoretical curve obtained are roughly similar in trend. It can be used to qualitatively evaluate the fracture mechanical properties of water-soaked brittle solid materials and can provide constructive engineering suggestions, which has high practical applicability.

[0097] In summary, this patented technical solution establishes a stress-deformation relationship equation for brittle solid materials considering the influence of internal moisture content after immersion in water. Based on this equation, the degree of internal damage changes in brittle solid materials after immersion in water can be explained, thereby determining the stress-strain relationship and evaluating the fracture mechanics properties of the brittle solid material. Specifically targeting brittle solid materials after immersion in water, as the moisture content increases, the degree of internal damage increases, leading to a weakening of the brittle solid material's strength and a greater susceptibility to fracture. Furthermore, experimental examples verify the rationality of this method. This invention provides support for evaluating the safety and stability of brittle solid materials under different degrees of water immersion, and has significant engineering practical implications for evaluating the fracture mechanics properties of brittle solid materials after immersion in water.

[0098] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for evaluating the fracture mechanical properties of water-brittle solid materials, characterized in that, Includes the following steps: Step 1: Prepare a set of rectangular brittle solid material samples. Immerse the samples in water. After immersion, weigh the samples with different immersion times, and then select samples with different moisture contents. Step 2: Select samples with different moisture contents from Step 1, and measure the uniaxial compressive stress-strain relationship curve and the initial density of micro-defects of the brittle solid material samples under different moisture contents. Step 3: Select samples with different moisture contents from Step 1 and determine the sliding friction coefficient of brittle solid material samples with different moisture contents. Step 4: Pre-fabricate brittle solid samples containing cracks and measure the fracture toughness of brittle solid materials with different moisture contents. Step 5: Based on the above steps, complete the determination of the fracture strength of brittle solid material samples under different moisture contents after soaking in water. In step 2, the uniaxial compressive stress-strain relationship curves of brittle solid material samples with different moisture contents are obtained by measuring with conventional compression testing instruments. In step 2, the initial density of microdefects in samples with different moisture contents is determined using an electron microscope scanning instrument. The volume of internal defects in brittle solid materials with different moisture contents is then determined, and the ratio of this volume to the sample volume is the initial density of microdefects for that sample. D 0, the relationship between the initial density and moisture content is: (1)； In step 3, the sliding friction coefficient of samples with different moisture contents is determined using two identical, smooth-surfaced brittle solid materials through a direct shear test apparatus. μ The relationship between the friction coefficient and the moisture content is determined as follows: (2)； Step 4 involves preparing brittle solid specimens with pre-existing cracks and using a three-point bending test instrument to measure the fracture toughness of brittle solid materials with different moisture contents. K IC The relationship between fracture toughness and water content is determined as follows: (3)； In step 5, based on the theory of solid damage and fracture mechanics, the stress-strain relationship of brittle solid materials considering different moisture contents is determined as follows: (4) In the formula: (5) (6) (7) (8) In step 5, the parameters in equation (7) D 0(ω) can be determined by equation (1) in step 2; In step 5, the parameter in equation (4) K IC (ω) can be determined by equation (3) in step 4; In step 5, the parameters in equation (5) μ (ω) can be determined by equation (2) in step 3; In step 5, equation (4) contains the parameter... a It is the average size of the initial defects inside a brittle solid material; In step 5, equation (5) contains parameters. φ The initial defect angle, which takes a value greater than 0 and less than 90; In step 5, the parameters a , φ The specific values ​​need to be determined by comparing and analyzing the theoretical and experimental stress-strain relationship curves from step 5 and step 2. The parameter is determined when the two are closest. a , φ ; In step 5, equation (7) contains the parameter... ε 0 is approximately equal to the strain value corresponding to the maximum stress in the stress-strain relationship curve in step 2; σ1 is the axial stress, and ε1 is the axial strain; The initial density of micro-defects in the sample in step 2 is less than 1; In step 5, the parameters m Select values ​​1, 2, and 3; In step 5, the parameters β The value is greater than 0 and less than 1.

2. The method for evaluating the fracture mechanical properties of water-soaked brittle solid materials as described in claim 1, characterized in that, In step 1, brittle solid materials after different soaking times are weighed to determine the degree of weight change of the brittle solid materials before and after soaking. The weight difference is the weight of water. Then, the ratio of the weight of water to the weight of the dried brittle solid material sample is the moisture content.

Images