Method for calculating fracture toughness of multilayer biomimetic ceramic cutting tool

Abstract

The application discloses a kind of multilayer biomimetic ceramic cutter computing fracture toughness method, the invention is based on the toughening mechanism of imitated shell pearl layer, the microstructure evolution mechanism of shell, crack propagation mechanism and fracture mode and the high performance as research object, then its features and functions are applied to ceramic cutter, to study the crack propagation mechanism, toughening mechanism in homogeneous layer of biomimetic ceramic cutter, between heterogeneous layers, and establish the crack propagation mechanism, toughening mechanism model of biomimetic ceramic cutter, then it is linked with component, sintering process, structure parameter, constructs the fracture toughness model of biomimetic ceramic cutter, and then develops biomimetic ceramic cutter.

Description

Technical Field

[0001] This invention discloses a method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools. Background Technology

[0002] Currently, there is limited theoretical research on fracture toughness models for biomimetic ceramic cutting tools. Existing methods for calculating the fracture toughness of homogeneous ceramic cutting tools include the indentation method (Cook RF, Lawn B RA Modified Indentation Toughness Technique [J]. Journal of the American Ceramic Society, 1983, 66(11): 0-0. DOI: 10.1111 / j.1151-2916.1983.tb10571.x.) and the single-sided V-beam notch method (GBT4161).

[0003] Among them, the fracture toughness model of multilayer materials based on experimental testing proposed by Song (Song J, Zhang Y, Fang Y, et al. Influence of structural parameters and transition interface on the fracture property of Al2O3 / Mo laminated composites[J]. Journal of the European Ceramic Society, 2015, 35(5):1581-1591.DOI:10.1016 / j.jeurceramsoc.2014.11.004.) improves the single-sided notched beam method; however, both the indentation method and the single-sided V-notched beam method are applicable to the performance testing of homogeneous material samples that have already been obtained, and cannot predict the results using existing models before conducting experiments and performance tests. The single-sided V-notched beam method requires pre-fabricated notches, which is not very friendly to Al2O3-based ceramic materials, and its calculation accuracy is reduced. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention discloses a novel method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools, based on SiC whiskers (SiC... w The growth phenomenon during the sintering process was investigated in the intermediate layer material SiC. w Growth mechanism and in different SiC w The study investigated the effects of different SiC content, sintering processes, and structural parameters on the overall fracture toughness of biomimetic ceramic cutting tool materials. A predictive model was established for the relationship between material composition, sintering process, structural parameters, and fracture toughness. Specific parameters included SiC content.w Composition, sintering temperature, holding time, sintering pressure, layer thickness ratio, etc.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for calculating the fracture toughness of a multilayer biomimetic ceramic cutting tool includes the following steps:

[0007] Step (1) Obtain the crack propagation and toughening mechanism within the homogeneous layer of the biomimetic ceramic cutting tool and its contribution to the fracture toughness of the biomimetic ceramic cutting tool, including SiC. w The contributions of bridging effect, pull-out effect and nanophase toughening.

[0008] Step (2) Based on the SiC whiskers in the intermediate layer of the biomimetic ceramic cutting tool (SiC w The growth phenomenon during sintering was investigated, and a growth mechanism model was established to obtain the contribution of this growth mechanism to the fracture toughness within the homogeneous layer, including the effects of different component contents, sintering temperature, holding time, and sintering pressure on the fracture toughness within the homogeneous layer.

[0009] Step (3) obtains the contribution of residual thermal stress between heterogeneous layers to the fracture toughness of biomimetic ceramic cutting tools, including the influence of structural parameters on the fracture toughness between heterogeneous layers.

[0010] Step (4) combines steps (1) to (3) to obtain a SiC-based product. w Fracture toughness K of multi-scale, multi-component, biomimetic ceramic cutting tools with growth mechanism IC Theoretical prediction model; fracture toughness of biomimetic ceramic cutting tools is calculated based on this model.

[0011] As a further technical solution, the fracture toughness of biomimetic ceramic cutting tools depends on the fracture toughness contribution of each layer of material, that is, to study the crack propagation toughening mechanism within homogeneous layers and the crack propagation toughening mechanism between heterogeneous layers.

[0012] As a further technical solution, the expression for the crack propagation and toughening mechanism within the homogeneous layer in step (1) is as follows:

[0013] K IC =∑K i +K r

[0014] In the formula, Contribution to matrix grains, K i K represents the contribution of different crack propagation modes to fracture toughness when there is no residual thermal stress. r The toughening contribution of residual thermal stress can be positive or negative.

[0015] As a further technical solution, in step (1), the crack propagation toughening mechanism within the homogeneous layer considers SiC. w The contributions of bridging effect, pull-out effect, and nanophase toughening are expressed as follows:

[0016]

[0017] In the formula, SiC crack overcoming w The energy contributions of bridging and pull-out effects, ΔK n E represents the contribution of the nanophase to toughening, and E is the elastic modulus of the composite material within the homogeneous layer.

[0018] As a further technical solution, the elastic modulus E of the composite material within the homogeneous layer is expressed as follows:

[0019] E = E m V m +E w V w

[0020] In the formula, E m E w V m V w These represent the elastic modulus and volume fraction of the matrix phase and reinforcing phase of the biomimetic ceramic cutting tool material within the homogeneous layer, respectively.

[0021] As a further technical solution, the contribution expression of the nanophase toughening is as follows:

[0022] ΔK n =ΔK cb +ΔK cg

[0023] In the formula, ΔK cb ΔK cg These represent the contributions of nanoparticles to the fracture toughness of the matrix grain boundaries and the fracture toughness of the matrix grains, respectively.

[0024] As a further technical solution, due to SiC w The expressions for the energy contribution of the system due to the bridging effect and the pull-out effect are as follows:

[0025]

[0026]

[0027] In the formula, l b SiC w The critical debonding length from the matrix phase, l p SiC w Pull out the length, SiC for bridgingw areal density, SiC w Surface density at the time of extraction SiC w The fracture strength, r is SiC w The radius τ is SiC w Interfacial friction with the matrix phase, SiC w The elastic modulus.

[0028] The intermediate SiC layer in step (2) w The expression for the growth mechanism model is:

[0029]

[0030] In the formula, D is the grain diameter after sintering, D0 is the original grain size, m is a constant determined by the sintering mechanism, and t is the holding time; K0 and Q are the SiC... w The growth mechanism constant and activation energy in the diameter direction, R is the molar gas constant, T is the sintering temperature, k represents the influence coefficient of sintering pressure on grain growth, and σ is the sintering pressure; the sintered SiC w Grain diameter size D and SiC w The expression for radius r is:

[0031] D = 2r.

[0032] As a further technical solution, the contribution expression of the residual thermal stress of the heterolayer in step (3) is as follows:

[0033]

[0034] In the formula, h(x,a) is the weighting function, a is the crack length, x is the distance to the surface, and σ res (x) represents residual thermal stress;

[0035] The weight function is expressed as:

[0036]

[0037] In the formula, A vu is a coefficient; h is the total layer thickness of the tool;

[0038] The residual stress of the heterogeneous layer is calculated as follows:

[0039]

[0040] σ res1 =-σ res2 ×L v

[0041]

[0042] In the formula, σ res1 σ res2 This represents the residual thermal stress in the surface and intermediate layers, where E1, E2, α1, and α2 are the composite elastic modulus and thermal expansion coefficients of the surface and intermediate layers, respectively, and T0 is the room temperature. sf h1 is the stress-free temperature; N is the number of layers of the intermediate layer material; h1 is the thickness of the surface layer material; h2 is the layer thickness of the intermediate layer material.

[0043] As a further technical solution, the fracture toughness K of the multi-scale, multi-component heterogeneous interlayer biomimetic ceramic cutting tool... IC The theoretical prediction model is as follows:

[0044]

[0045] In the formula, N is the number of intermediate layer materials, h is the total layer thickness, and h1 and h2 are the layer thicknesses of the surface layer material and the intermediate layer material, respectively. These are the fracture toughnesses of the surface material and the intermediate layer material, respectively. These represent the contributions of residual stress in the surface and intermediate layers to fracture toughness, respectively.

[0046] As a further technical solution, when N is 0, the prediction model is the fracture toughness K of a single-layer biomimetic ceramic cutting tool. IC Theoretical prediction model.

[0047] The beneficial effects of this invention are as follows:

[0048] This invention establishes a relationship model between materials and sintering processes. Based on the study of the material mechanism, fracture toughness can be predicted. That is, before conducting experiments, the material composition, sintering process, and structural parameters (layer thickness ratio) can be optimized in reverse according to the fracture toughness requirements. This greatly reduces material waste and experimental complexity, and also saves labor and time costs. Attached Figure Description

[0049] Figure 1 Overall flowchart of the present invention;

[0050] Figure 2 This is a schematic diagram of the loading of the multi-layer biomimetic ceramic cutting tool of the present invention. Detailed Implementation

[0051] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0052] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] To improve the brittleness and experimental complexity of ceramic cutting tools, this invention, based on the fundamental principles of bionics, draws upon the microstructure evolution mechanism, crack propagation mechanism, and fracture mechanism of seashells to study the crack propagation and toughening mechanisms within homogeneous layers and between heterogeneous layers in bionic ceramic cutting tools. Furthermore, it establishes models of these crack propagation and toughening mechanisms for bionic ceramic cutting tools, linking them to sintering processes and structural parameters. This leads to the development of bionic ceramic cutting tools that achieve advantages such as controllable performance and adjustable interfaces.

[0054] Glossary: ​​In this embodiment, "homogeneous layer" refers to a single layer of material with the same composition;

[0055] "Middle layer" refers to all layers other than the bottom and top layers;

[0056] "Heterogeneous layer" refers to a single layer of material with different components.

[0057] This invention proposes a method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools. The fracture toughness of the biomimetic ceramic cutting tool depends on the fracture toughness contribution of each layer, i.e., it studies the crack propagation toughening mechanism within homogeneous layers and the crack propagation toughening mechanism between heterogeneous layers. Therefore, the method includes the following steps:

[0058] Step (1) Obtain the crack propagation and toughening mechanism within the homogeneous layer of the biomimetic ceramic cutting tool and its contribution to the fracture toughness of the biomimetic ceramic cutting tool, including SiC w The contributions of bridging effect, pull-out effect, and nanophase toughening; the expression for the toughening mechanism of crack propagation within the homogeneous layer is as follows:

[0059] K IC =∑K i +K r

[0060] In the formula, K i K represents the contribution of different crack propagation modes to fracture toughness when there is no residual thermal stress. r The toughening contribution of residual thermal stress can be positive or negative;

[0061] The toughening mechanism of intralayer crack propagation in SiC is considered. w The contributions of bridging effect, pull-out effect, and nanophase toughening are expressed as follows:

[0062]

[0063] In the formula, SiC crack overcoming w The energy contributions of bridging and pull-out effects, ΔK n E represents the contribution of the nanophase to toughening, and E is the elastic modulus of the composite material within the homogeneous layer.

[0064] The expression for the elastic modulus E of a composite material within a homogeneous layer is:

[0065] E = E m V m +E w V w

[0066] In the formula, E m E w V m V w These represent the elastic modulus and volume fraction of the matrix phase and reinforcing phase of the biomimetic ceramic cutting tool material within the homogeneous layer, respectively.

[0067] The contribution expression for toughening by nanophases is:

[0068] ΔK n =ΔK cb +ΔK cg

[0069] In the formula, ΔK cb ΔK cg These represent the contributions of nanoparticles to the fracture toughness of the matrix grain boundaries and the fracture toughness of the matrix grains, respectively.

[0070] Due to SiC w The expressions for the energy contribution of the system due to the bridging effect and the pull-out effect are as follows:

[0071]

[0072]

[0073] In the formula, l b SiC w The critical debonding length from the matrix phase, l p SiC w Pull out the length, SiC for bridging w areal density, SiC w Surface density at the time of extraction.

[0074] Step (2) Based on the SiC whiskers in the intermediate layer of the biomimetic ceramic cutting tool (SiC wTo investigate the growth phenomenon during sintering, a growth mechanism model was established to obtain the contribution of this growth mechanism to the fracture toughness within the homogeneous layer, including the effects of different component contents, sintering temperature, holding time, and sintering pressure on the fracture toughness within the homogeneous layer.

[0075] Intermediate SiC w The expression for the growth mechanism model is:

[0076]

[0077] In the formula, D is the grain diameter after sintering, D0 is the original grain size, m is a constant determined by the sintering mechanism, and t is the holding time; K0 and Q are the SiC... w The growth mechanism constant and activation energy in the diameter direction, R is the molar gas constant, T is the sintering temperature, and k represents the influence coefficient of sintering pressure on grain growth.

[0078] The sintered SiC w Grain diameter size D and SiC w The expression for the grain radius r is:

[0079] D = 2r.

[0080] Step (3) obtains the contribution of residual thermal stress between heterogeneous layers to the fracture toughness of biomimetic ceramic cutting tools, including the influence of structural parameters on the fracture toughness between heterogeneous layers.

[0081] The contribution expression for the residual thermal stress of the heterolayer in step (3) is as follows:

[0082]

[0083] In the formula, h(x,a) is the weighting function, a is the crack length, and x is the distance to the surface.

[0084] The weight function is expressed as:

[0085]

[0086] In the formula, A vu For coefficients;

[0087] The residual stress of the heterogeneous layer is calculated as follows:

[0088]

[0089] σ res1 =-σ res2 ×L v

[0090] In the formula, σ res1 σ res2This represents the residual thermal stress in the surface and intermediate layers, where E1, E2, α1, and α2 are the composite elastic modulus and thermal expansion coefficients of the surface and intermediate layers, respectively, and T0 is the room temperature. sf The stress-free temperature is denoted by N; the number of layers of the intermediate layer material is denoted by N; h1 is the thickness of the surface layer material; and h2 is the thickness of the intermediate layer material.

[0091] Step (4) combines steps (1), (2), and (3) to obtain a SiC-based product. w Fracture toughness K of multi-scale, multi-component, biomimetic ceramic cutting tools with growth mechanism IC Theoretical prediction model; details are as follows:

[0092] The fracture toughness K of the multi-scale, multi-component heterogeneous interlayer biomimetic ceramic cutting tool IC The theoretical prediction model is as follows:

[0093]

[0094] In the formula, N is the number of intermediate layer materials, and h is the total layer thickness; h1、 h2 represents the fracture toughness and layer thickness of the surface and intermediate layers, respectively. These represent the contributions of residual stress in the surface and intermediate layers to the fracture toughness, respectively. It should be noted that in this model, when N is 0, the prediction model represents the fracture toughness K of a single-layer biomimetic ceramic cutting tool. IC A theoretical prediction model is used to calculate the fracture toughness of biomimetic ceramic cutting tools.

[0095] The following explanation uses a specific cutting tool as an example. The surface material of this tool is 74% vol Al2O3 and 20% vol SiC. w 5% vol SiC n 0.5% vol Y₂O₃, 0.5% vol MgO, with the intermediate layer material being 20% ​​SiC w For example, the material composition is 74% vol Al2O3 and 20% vol SiC. w 5% vol TiC n 0.5% vol Y2O3, 0.5% vol MgO, sintering temperature 1700℃, holding time 30 min, sintering pressure 32 MPa.

[0096] It should be noted here that, as Figure 2 The three-layer biomimetic ceramic knife shown has a surface layer and a middle layer that are homogeneous, while the surface layer and the middle layer are heterogeneous.

[0097] First, the crack propagation and toughening mechanism within the homogeneous layer of the biomimetic ceramic tool in step (1) and its contribution to the fracture toughness of the biomimetic ceramic tool are obtained, namely, the fracture toughness contributions of the surface layer and the intermediate layer. and

[0098] Then, the contribution of the residual thermal stress between the heterogeneous layers in step (3) to the fracture toughness of the biomimetic ceramic tool is obtained, i.e. and

[0099] Finally, the fracture toughness K of the multilayer biomimetic ceramic tool in step (4) is obtained. IC Theoretical prediction model.

[0100] Based on theoretical and experimental data, it is concluded that

[0101] The fracture toughness of the intermediate layer is:

[0102] The fracture toughness of the surface material is:

[0103] Theoretical fracture toughness K of the positive surface layer IC =5.71, K was actually measured IC =5.68.

[0104] Based on fracture toughness and statistical analysis of SiC in the intermediate layer fracture morphology w Given the quantity and diameter, solve for m, Q, and K in reverse order.

[0105] Under isothermal and isobaric conditions, the activation energy m = 8 was obtained.

[0106] To obtain the activation energy Q, sintering experiments were conducted on biomimetic ceramic cutting tools under pressureless conditions. The microstructure and particle size distribution of the intermediate layer were analyzed to obtain the SiC... w The diameter D. The sintering process here is: SiC w The content is 20%, the holding time is 30 min, the sintering pressure is 0 MPa, and the sintering temperatures are 1600℃ and 1700℃ respectively. Substitute these values ​​into the formula... The activation energy Q is obtained by comparing the two equations.

[0107] After calculation, Q = 167.584 kJ / mol;

[0108] Under isobaric conditions, K0 = 37.35 μm was obtained. 8 / h;

[0109] Based on the values ​​of Q and K0, k is solved. Under the conditions of 1700℃, holding time of 30 min, and sintering pressure of 32 MPa, k = 2.44 x 10⁻⁶. -6 MPa-1 .

[0110] This invention compensates for the influence of different compositions, sintering processes, and structural parameters on the grain growth mechanism and densification process of ceramic cutting tools during hot pressing sintering. Therefore, before the experiment, composition design, sintering process optimization, and structural parameter optimization can be carried out according to fracture toughness requirements, which greatly improves experimental efficiency and reduces the complexity of experimental operations.

Claims

1. A method for calculating the fracture toughness of a multilayer biomimetic ceramic cutting tool, characterized in that, Includes the following steps: Step (1) Obtain the toughening mechanism of crack propagation in the homogeneous layer of the biomimetic ceramic tool and its contribution to the fracture toughness of the biomimetic ceramic tool; Step (2) Based on the SiC intermediate layer of the biomimetic ceramic cutting tool w The growth phenomenon during sintering was investigated, and a growth mechanism model was established to obtain the contribution of this growth mechanism to the fracture toughness within the homogeneous layer. Step (3) Obtain the contribution of residual thermal stress between heterogeneous layers to the fracture toughness of biomimetic ceramic cutting tools; Step (4) combines steps (1), (2), and (3) to obtain a SiC-based product. w Fracture toughness of multi-scale, multi-component, biomimetic ceramic cutting tools with growth mechanism at multiple scales K IC A theoretical prediction model was developed, and the fracture toughness of the biomimetic ceramic cutting tool was calculated based on this model. The fracture toughness of the multi-layer biomimetic ceramic cutting tool in step (4) K IC Theoretical prediction model for : In the formula, N The number of layers of intermediate material. h The total layer thickness of the cutting tool; 、h 1 、 、h 2 represents the fracture toughness and thickness of the surface layer and intermediate layer materials, respectively. 、 These represent the contributions of residual stress in the surface and intermediate layers to fracture toughness, respectively.

2. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 1, characterized in that, The expression for the crack propagation and toughening mechanism within the homogeneous layer in step (1) is as follows: + In the formula, K i The contribution of different crack propagation modes to fracture toughness under conditions of no residual thermal stress. K r The toughening contribution of residual thermal stress can be positive or negative.

3. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 1, characterized in that, In step (1), the crack propagation toughening mechanism within the homogeneous layer considers the contributions of SiCw bridging effect, pull-out effect, and nanophase toughening, and its expression is: In the formula, Contribution to the matrix grains, , SiC crack overcoming w The energy contributions of bridging and pull-out effects Contribution to the toughening effect of nanophases, E is Elastic modulus of composite materials within a homogeneous layer.

4. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 3, characterized in that, The elastic modulus of the composite material within the homogeneous layer E The expression is: In the formula, E m 、E w 、V m 、V w These represent the elastic modulus and volume fraction of the matrix phase and reinforcing phase of the biomimetic ceramic cutting tool material within the homogeneous layer, respectively.

5. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 3, characterized in that, The contribution expression for the toughening effect of the nanophase is as follows: In the formula, Δ K cb Δ K cg These represent the contributions of nanoparticles to the fracture toughness of the matrix grain boundaries and the fracture toughness of the matrix grains, respectively.

6. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 3, characterized in that, Due to SiC w The expressions for the energy contribution of the system due to the bridging effect and the pull-out effect are as follows: In the formula, l b SiC w Critical debonding length from the matrix phase. l p SiC w Pull out the length, SiC for bridging w areal density, SiC w Surface density at the time of extraction SiC w The fracture strength, r is SiC w The radius τ is SiC w Interfacial friction with the matrix phase, SiC w The elastic modulus.

7. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 1, characterized in that, The expression for the growth mechanism model of the intermediate SiCw layer in step (2) is as follows: In the formula, D This refers to the grain diameter after sintering. D 0 represents the original grain size. m It is a constant, determined by the sintering mechanism. t For heat preservation time; K 0、 Q SiC w The growth mechanism constant and activation energy in the diameter direction, R For molar gas constant, T The sintering temperature is... k The coefficient representing the effect of sintering pressure on grain growth is σ, where σ is the sintering pressure; the sintered SiC w Grain diameter size D and SiC w radius r The expression is: 。 8. The method for calculating the fracture toughness of multilayer biomimetic ceramic cutting tools as described in claim 1, characterized in that, The contribution expression for the residual thermal stress of the heterostructure in step (3) is as follows: In the formula, h(x, a) For the weight function, a The length of the crack. x σ is the distance to the surface. res ( x () represents residual thermal stress; The weight function is expressed as: In the formula, A vu is a coefficient; h is the total layer thickness of the tool.

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