A method for evaluating the fracture strength of a brittle solid material subjected to high temperature treatment

Abstract

The high-temperature processing brittle solid material fracture strength evaluation method of the present application comprises the following steps: 1. A group of cubic brittle solid material samples are prepared, the samples are placed in a high-temperature oven for constant temperature and time heating treatment, and then the samples are taken out for normal temperature cooling, and then brittle solid material samples treated at different temperatures are selected; 2. The brittle solid material treated at different high temperatures in step 1 is selected, and the stress-strain relationship curve and the sliding friction coefficient of the brittle solid material at different temperatures are measured; 3. The brittle solid material treated at different high temperatures in step 1 is selected, and the initial microcrack density and the fracture toughness of the brittle solid material sample treated at different high temperatures are measured; 4. Based on the above steps, the fracture strength determination of the brittle solid material sample treated at high temperature is completed. The method can measure the load-carrying and deformation capacity of the brittle solid material treated at high temperature and the influence on the engineering safety and stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of brittle solid material mechanics engineering, and in particular to a method for evaluating the fracture strength of brittle solid material after high-temperature treatment. BACKGROUND

[0002] The structural non-uniformity of brittle solid materials is often more prominent, with a larger scale and a more serious degree of non-uniformity. Brittle solid material rock is composed of mineral particles of various types, shapes, and sizes. Brittle solid material ceramics are usually sintered from small particles, and the size and sintering degree of the particles also have non-uniform distribution. Brittle solid material concrete is composed of cement mortar and various aggregates, and there is an interface between them with different properties. In addition to the above non-uniformity in the composition of the matrix, natural and man-made brittle materials usually contain a large number of defects, mainly in the form of pores and cracks. The size of the defects ranges from geological layers to microns, covering a very wide range, and the orientation of the defects is usually random. The existence of various defects undoubtedly greatly increases the structural non-uniformity of brittle solid materials.

[0003] The non-uniform structure inside the brittle solid material contains a large number of open or closed micro-cracks, which will change with external load. Some micro-cracks will go through the process of nucleation, expansion, and aggregation into macro-cracks, causing the overall destruction of the brittle material.

[0004] Brittle solid materials, such as concrete, rock, ceramics, glass, etc., are one of the important materials in the fields of building, machinery, aviation, aerospace, and marine engineering construction. In these engineering applications, brittle solid materials often bear a large external load and have strong resistance to deformation.

[0005] However, in these engineering applications, when subjected to high-temperature factors such as fire, brittle solid materials often exhibit a common and extremely important failure mode of fracture failure. Some sudden fractures can also cause disastrous consequences.

[0006] The existing fracture strength evaluation methods in the prior art are all based on the evaluation methods for the fracture strength of granular materials, asphalt materials, etc. after high-temperature treatment, and are applied to the fracture strength evaluation of brittle solid materials. The existing public technology has not been optimized for brittle solid materials, and the existing public technology cannot determine the extent of the internal damage of brittle solid materials after high-temperature treatment, nor can it quantify the extent of the decrease in material strength after high-temperature treatment.

[0007] The existing technology also cannot explore the bearing and deformation capacity of brittle solid materials after high-temperature treatment and its impact on engineering safety and stability, nor can it assess whether it can continue to meet human use requirements.

[0008] Therefore, the person skilled in the art is committed to developing a fracture strength evaluation method for high-temperature treated brittle solid materials, aiming to solve the defects in the prior art. SUMMARY

[0009] In view of the above defects of the prior art, the technical problem to be solved by the present application is that the fracture strength evaluation method in the prior art does not optimize the brittle solid material, and the existing public technology cannot obtain the influence of temperature on the internal damage degree of the brittle solid material after high-temperature treatment, and the amplitude of the material strength reduction after high-temperature treatment cannot be quantified; the prior art cannot explore the bearing and deformation capacity of the brittle solid material after high-temperature treatment, and the influence on engineering safety and stability, and cannot evaluate whether it can continue to meet the use requirements of human beings.

[0010] To achieve the above-mentioned purpose, the present application is a fracture strength evaluation method for high-temperature treated brittle solid materials, comprising the following steps:

[0011] Step 1, a group of cubic brittle solid material samples are made, the samples are placed in a high-temperature oven for constant temperature and constant time heating treatment, and then the samples are taken out for normal temperature cooling, and then different temperature treated brittle solid material samples are selected;

[0012] Step 2, the brittle solid materials treated at different high temperatures in step 1 are selected, and the stress-strain relationship curve and the sliding friction coefficient of the brittle solid material at different temperatures are measured;

[0013] Step 3, the brittle solid materials treated at different high temperatures in step 1 are selected, and the initial microcrack density and fracture toughness of the brittle solid material sample treated at different high temperatures are measured;

[0014] Step 4, based on the above steps, the fracture strength determination of the brittle solid material sample after high-temperature treatment is completed;

[0015] The constant temperature temperature in step 1 is 25-850℃;

[0016] In step 1, a group of samples are selected to be heated at uniformly spaced temperatures;

[0017] In step 2, the stress-strain relationship curve of the brittle solid material at different temperatures is obtained by using a compression testing machine to carry out uniaxial compression deformation test;

[0018] In step 2, the sliding friction coefficient of the brittle solid material sample is obtained by using two identical and smooth surface brittle solid materials through a direct shear test instrument;

[0019] Step 3, select brittle solid material after different high temperature treatment in step 1, measure the initial microcrack density and fracture toughness of brittle solid material sample after different high temperature treatment;

[0020] In step 3, the initial microcrack density of the brittle solid material sample is first measured by using a scanning electron microscope test instrument to measure the volume of the internal voids of the brittle solid material sample after different high temperature treatment, and then the volume ratio of the internal voids to the volume of the brittle solid material sample is used to determine the initial microcrack density D0 of the brittle solid material after treatment at a specific temperature, which is less than 1. The relationship between the initial microcrack density and the heat treatment temperature T is:

[0021]

[0022] In step 3, the fracture toughness of the brittle solid material sample is measured by using a three-point bending test instrument to measure the fracture toughness K IC of the brittle solid material after different high temperature treatment, and the relationship between the fracture toughness and the heat treatment temperature T is determined as:

[0023]

[0024] Step 4, based on the above steps, the fracture strength of the brittle solid material sample after high temperature treatment is determined;

[0025] In step 4, the stress-strain relationship of the brittle solid material under the action of different high temperature treatment is determined as:

[0026] f(σ1,ε1,T)=σ1-K IC (T) / (πa 2 C1C2)=0 (3)

[0027] In the formula:

[0028]

[0029]

[0030] C3=a{[(1-exp[-(ε1 / ε0) m ]) / (D0(T))] 13 -1} (6)

[0031]

[0032] In formula (3) of step 4, the parameter a is the average size of the initial defects in the brittle solid material;

[0033] In formula (4) of step 4, the parameter is the initial defect angle, which is greater than 0 and less than 90;

[0034] In step 4, the parameter a, Specific values, need to compare and analyze step 4 and step 2 in the theoretical and experimental stress and strain relationship curve, when they are most close, that is, the parameter a,

[0035] In step 4, the formula (6), the parameter epsilon 0 is approximately equal to the strain value corresponding to the maximum stress of the stress and strain relationship curve in step 2;

[0036] The value of the parameter a is generally less than 4mm;

[0037] The parameter m is generally selected to be 1, 2, 3; the parameter beta is generally greater than 0 and less than 1;

[0038] In step 4, in the above formula, the parameters D0(T), K IC (T) can be determined by step 3, according to the stress and strain curve, the peak stress value of the brittle solid material can be determined, that is, the compressive strength;

[0039] In step 4, all parameters of the brittle solid material sample after high temperature treatment are determined, the stress and strain relationship curve of the brittle solid material under different high temperature treatment is calculated according to step 4, and then the deformation and strength characteristics of the brittle solid material after high temperature treatment can be judged; when the brittle solid material bears a load greater than the calculated strength value of the material, the material will be broken, and then the fracture mechanics characteristics of the material can be evaluated;

[0040] Further, in step 4, the specific values of each parameter can be adjusted appropriately under the above conditions to ensure that the stress and strain relationship curves obtained by step 4 and step 2 are consistent as much as possible;

[0041] By using the above scheme, the high temperature brittle solid material fracture strength evaluation method disclosed by the application has the following advantages:

[0042] (1) The high temperature brittle solid material fracture strength evaluation method of the application establishes an equation that can explain the compression load and deformation of the brittle solid material under the influence of high temperature by using damage fracture mechanics theory; according to the equation, the compression stress and strain relationship curve under different temperatures can be drawn, which can determine the strength of the brittle solid material under different temperatures, and then evaluate the bearing capacity and fracture mechanics performance of the brittle solid material;

[0043] (2) The fracture strength evaluation method for high-temperature treated brittle solid materials of the present application is specifically for brittle solid materials after high-temperature treatment, can quantitatively present the influence of different high temperatures on the internal damage degree of brittle solid materials after different high-temperature treatments, can know the amplitude of the strength reduction of brittle solid materials after different high-temperature treatments, can measure the bearing and deformation capacity of brittle solid materials after high-temperature treatment and the influence on engineering safety and stability, so that it can be evaluated whether the brittle solid materials after high-temperature treatment can meet the use requirements of human beings.

[0044] In summary, the fracture strength evaluation method for high-temperature treated brittle solid materials of the present application establishes an equation that can explain the compression load and deformation of brittle solid materials under the influence of high temperature, is specifically for brittle solid materials after high-temperature treatment, can measure the bearing and deformation capacity of brittle solid materials after high-temperature treatment and the influence on engineering safety and stability, so that it can be evaluated whether the brittle solid materials after high-temperature treatment can meet the use requirements of human beings.

[0045] The concept, specific technical solutions and technical effects of the present application will be further described in combination with specific embodiments, so as to fully understand the purpose, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a flowchart of the fracture strength evaluation method for high-temperature treated brittle solid materials of the present application;

[0047] Figure 2 is a test curve graph of the relationship between the compression strength of granite and the heat treatment temperature in embodiment 1 of the present application;

[0048] Figure 3 is a theoretical curve graph of the relationship between the compression strength of granite and the heat treatment temperature in embodiment 1 of the present application;

[0049] Figure 4 is a comparison curve graph of the relationship between the compression strength of granite and the heat treatment temperature in embodiment 1 of the present application. DETAILED DESCRIPTION

[0050] The following describes a plurality of preferred embodiments of the present application, so that the technical content thereof is more clear and convenient to understand. The present application can be embodied in many different forms of embodiments, and these embodiments are described by way of example, and the protection scope of the present application is not limited to the embodiments mentioned herein.

[0051] Embodiment 1: Selecting granite as a brittle solid material, completing high-temperature treatment, and evaluating the fracture strength thereof

[0052] As shown in the figure, Figure 1This is a schematic diagram of the process for evaluating the fracture strength of brittle solid materials subjected to high-temperature treatment according to the present invention;

[0053] First, perform step 1: prepare a set of cubic brittle solid material samples, place the samples in a high-temperature chamber for constant-temperature and timed heating treatment, and then remove the samples to cool at room temperature; then select brittle solid material samples treated at different temperatures.

[0054] In specific implementation, the sample made in step 1 is a rectangular brittle solid material with a length, width and height of 5cm, 5cm and 10cm respectively.

[0055] In specific implementation, in this Example 1, the selected constant temperature is room temperature, 25℃, 150℃, 300℃, 450℃, 600℃, or 900℃; the timer duration is 1 hour.

[0056] Then proceed to step 2, select brittle solid materials treated at different high temperatures in step 1, and measure the stress-strain relationship curves and sliding friction coefficients of the brittle solid materials at different temperatures;

[0057] In specific implementation, in this Example 1, the stress-strain relationship curves of brittle solid materials at different temperatures are obtained by conducting uniaxial compression deformation tests using a compression testing machine;

[0058] In specific implementation, in this embodiment 1, the sliding friction coefficient μ of the brittle solid material sample is obtained by using two identical brittle solid materials with smooth surfaces through a direct shear test instrument.

[0059] Finally, in step 3, select brittle solid materials after different high-temperature treatments in step 1, and measure the initial microcrack density and fracture toughness of the brittle solid material samples after different high-temperature treatments.

[0060] In step 3, the initial microcrack density of the brittle solid material sample is first determined by using a scanning electron microscope to measure the volume of internal voids in the brittle solid material sample after different high-temperature treatments. Then, the ratio of this volume to the total volume of the brittle solid material sample is used to determine the initial microcrack density D0 of the brittle solid material after treatment at a specific temperature. The value of D0 is less than 1. The relationship between this initial microcrack density and the heat treatment temperature T is as follows:

[0061]

[0062] In step 3, the fracture toughness of the brittle solid material sample...

[0063] The fracture toughness K of brittle solid materials after different high-temperature heat treatments was measured using a three-point bending test apparatus. IC The relationship between fracture toughness and heat treatment temperature T is determined as follows:

[0064]

[0065] Finally, step 4, based on the above steps, complete the determination of the fracture strength of brittle solid material sample after high temperature treatment;

[0066] In step 4, the stress-strain relationship of brittle solid material under the action of different high temperature heat treatment is determined as:

[0067] f(σ1,ε1,T)=σ1-K IC (T) / (πa 2 C1C2)=0 (3)

[0068] In the formula:

[0069]

[0070]

[0071] C3=a{[(1-exp[-(ε1 / ε0) m ]) / (D0(T))] 1 / 3 -1} (6)

[0072]

[0073] In formula (3) of step 4, the parameter a is the average size of the initial defect inside the brittle solid material;

[0074] In specific implementation, the value of parameter a is generally less than 4mm;

[0075] In formula (4) of step 4, the parameter is the initial defect angle, which is greater than 0 and less than 90;

[0076] In step 4, the parameter a, The specific value needs to compare and analyze the theoretical and experimental stress-strain relationship curves in step 4 and step 2, when they are closest, the parameters a,

[0077] In specific implementation, in this embodiment 1, the value of parameter a is selected as 2.1; the value of parameter is selected as 33;

[0078] In formula (6) of step 4, the parameter ε0 is approximately equal to the strain value corresponding to the maximum stress of the stress-strain relationship curve in step 2;

[0079] In specific implementation, the value of parameter m is generally selected as 1, 2, 3; the value of parameter β is generally greater than 0 and less than 1;

[0080] In the embodiment 1, the parameter m is 1, and the parameter β is 0.17.

[0081] In the step 4, the parameters D0(T) and K IC (T) can be determined by the step 3, according to the stress-strain curve, the peak stress value of the brittle solid material, i.e. the compressive strength, can be determined;

[0082] In the embodiment 1, the parameters are summarized in Table 1.

[0083] Table 1: Performance parameter values of the granite brittle solid material

[0084]

[0085] In the step 4, all the parameters of the brittle solid material sample after high-temperature treatment are determined, the stress-strain relationship curve of the brittle solid material under different high-temperature treatments is calculated according to the step 4, and then the deformation and strength characteristics of the brittle solid material after high-temperature treatment can be determined. When the brittle solid material bears a load greater than the calculated strength value of the material, the material will be fractured, and then the fracture mechanics characteristics of the material can be evaluated.

[0086] As shown in the figure, Figure 2 is a test curve diagram of the relationship between the compressive strength of the granite and the heat treatment temperature in the embodiment 1 of the present application.

[0087] From Figure 2 it can be seen that the strength of the granite brittle solid material is still above 120 Mpa after the constant temperature and time treatment at 450℃, and still has strong fracture resistance. However, when the constant temperature exceeds 450℃, the strength decreases significantly.

[0088] As shown in the figure, Figure 3 is a theoretical curve diagram of the relationship between the compressive strength of the granite and the heat treatment temperature in the embodiment 1 of the present application.

[0089] Figure 3 The theoretical curve of the relationship between the compressive strength of the granite and the heat treatment temperature is the most close theoretical curve obtained by precise material strength instrument measurement.

[0090] As shown in the figure, Figure 4 is a comparison curve diagram of the relationship between the compressive strength of the granite and the heat treatment temperature in the embodiment 1 of the present application.

[0091] From Figure 4It can be seen that, by using the method, the actual test curve obtained is similar in trend to the theoretical curve, the test error of each strength point is not more than 10%, and the strength of the test is extremely close to the theoretical strength at the transition point of several constant temperature temperatures;

[0092] By Figure 4 It can be seen that the fracture strength of the granite brittle solid material obtained in embodiment 1 is not much different from the theoretical value, and can be used to evaluate the fracture strength of the building under high temperature conditions, and has high practical applicability.

[0093] In summary, the technical scheme of the patent establishes an equation that can explain the compression load and deformation of brittle solid materials under the influence of high temperature by using damage fracture mechanics theory. According to the equation, a compression stress-strain curve at different temperatures can be drawn, which can determine the strength of brittle solid materials at different temperatures, and further evaluate the bearing capacity and fracture mechanics performance of brittle solid materials. Moreover, for brittle solid materials treated by high temperature, the equation can quantitatively present the influence of different high temperatures on the internal damage degree of brittle solid materials after different high temperature treatments, and also can know the amplitude of the strength reduction of brittle solid materials after different high temperature treatments, so as to measure the bearing and deformation capacity of brittle solid materials after high temperature treatment, and the influence on engineering safety and stability, so that it can be evaluated whether the brittle solid material treated by high temperature can meet the use requirements of human beings.

[0094] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and changes without creative labor based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited test based on the prior art according to the concept of the present application shall be within the protection scope determined by the claims.

Claims

1. A method for evaluating the fracture strength of a brittle solid material subjected to high temperature processing, characterized by, Includes the following steps: Step 1: Prepare a set of cubic brittle solid material samples, place the samples in a high-temperature chamber for constant temperature and time heating treatment, and then take out the samples and cool them at room temperature. Then select brittle solid material samples treated at different temperatures. Step 2: Select brittle solid materials treated at different high temperatures in Step 1, and measure the stress-strain relationship curves and sliding friction coefficients of the brittle solid materials at different temperatures; Step 3: Select brittle solid materials after different high-temperature treatments in Step 1, and measure the initial microcrack density and fracture toughness of the brittle solid material samples after different high-temperature treatments. In the step 3, the initial microcrack density of the brittle solid material sample is first measured by using the scanning electron microscope to measure the volume of the internal voids of the brittle solid material sample after different high temperature treatments, and then the initial microcrack density of the brittle solid material after the specific temperature treatment is determined by using the volume ratio of the internal voids to the volume of the brittle solid material sample D 0, which is less than 1, and the initial microcrack density and the heat treatment temperature T have the following relationship: (1)； In step 3, the fracture toughness of the brittle solid material sample is measured using a three-point bending test instrument to determine the fracture toughness of the brittle solid material after different high-temperature heat treatments. K IC Determine the relationship between fracture toughness and heat treatment temperature T The relationship is: (2)； Step 4: Based on the above steps, complete the fracture strength determination of the brittle solid material sample after high-temperature treatment.

2. The fracture strength evaluation method as described in claim 1, characterized in that, In step 2, the stress-strain relationship curves of brittle solid materials at different temperatures are obtained by conducting uniaxial compression deformation tests using a compression testing machine. In step 2, the sliding friction coefficient of the brittle solid material sample is obtained by using two identical brittle solid materials with smooth surfaces through a direct shear test instrument.

3. The fracture strength evaluation method as described in claim 1, characterized in that, In step 4, the stress-strain relationship of the brittle solid material under different high-temperature heat treatments is determined as follows: (3) In the formula: (4) (5) (6) (7) In step 4, equation (3) contains parameters. a It is the average size of the initial defects inside a brittle solid material; In step 4, equation (4) contains parameters. φ The initial defect angle, which takes a value greater than 0 and less than 90; In step 4, 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 4 and step 2. The parameter is determined when the two curves are closest. a , φ ; In step 4, equation (6) contains parameters. ε 0 is approximately equal to the strain value corresponding to the maximum stress in the stress-strain relationship curve in step 2; In step 4, the parameters in the above formula are... D 0( T ), K IC ( T The peak stress value of the brittle solid material can be determined through step 3, based on the stress-strain relationship curve mentioned above.

4. The fracture strength evaluation method as described in claim 1, characterized in that, In step 4, the specific values ​​of each parameter can be appropriately adjusted under the above conditions to ensure that the stress-strain relationship curves obtained theoretically and experimentally in step 4 are as consistent as possible with those obtained in step 2.

5. The fracture strength evaluation method as described in claim 1, characterized in that, The constant temperature in step 1 is 25°C-850°C.

6. The fracture strength evaluation method as described in claim 3, characterized in that, In step 4, the parameters a The value should be less than 4mm; In step 4, the parameters m Select values ​​1, 2, and 3; In step 4, the parameters β The value is greater than 0 and less than 1.

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