A method for predicting the breaking strength of a notched structural member

Abstract

The application discloses a kind of notch structural member's fracture strength prediction method, specifically includes the following steps: step one, the average grain size G of the quasi-brittle material of the component to be detected is determined and tensile strength f t ;Step two, the notch geometry parameter of the component to be detected is measured;Step three, the average grain size G of the component to be detected obtained in step one and tensile strength f t And the notch geometry parameter obtained in step two are calculated to obtain fracture strength σ N By the way of macro-microscopic parameter combination, the fracture strength prediction model of quasi-brittle material component is established, compared with the fracture model only relying on macroscopic parameter, the mechanical property difference of different quasi-brittle materials is considered from microstructure angle in the application, can analyze fracture behavior from micro-mechanism angle, solves the technical problem that different notch geometry parameters are difficult to quantitatively characterize the influence on fracture strength in prior art.

Description

Technical Field

[0001] This invention belongs to the technical field of fracture mechanics performance prediction model, and relates to fracture strength prediction method, specifically a fracture strength prediction method for notched structural components. Background Technology

[0002] Quasi-brittle materials have a wide range of applications. For example, ceramic materials possess excellent mechanical properties, corrosion resistance, and high-temperature resistance, making them widely used in aerospace, biomedicine, and other fields. Due to design requirements and manufacturing precision limitations, notches are unavoidable in structural components. These notches are prone to stress concentration, leading to component failure. Furthermore, quasi-brittle material structural components exhibit minimal plastic deformation before failure and lack warning signs. Therefore, predicting the fracture strength of notched structural components has become a common concern in the engineering and academic communities.

[0003] Notch shapes are diverse, and studying their impact on fracture performance requires considering the influence of different notch geometry parameters. For cracks, fracture performance is mainly affected by crack length; U-notch structures are affected by notch depth and root radius; V-notches, based on U-notches, incorporate the influence of the opening angle. Therefore, it is necessary to propose a fracture performance prediction method that considers the influence of different notch geometry parameters and can be applied to structures with different notch shapes. Fracture strength is a crucial parameter for determining whether a notched component has reached the failure condition. Therefore, establishing a fracture strength prediction method that considers the influence of notch geometry parameters is of great significance for predicting the fracture behavior of structural components. Currently, there are few methods that can quantitatively characterize the influence of different notch geometry parameters on fracture strength. Therefore, establishing a fracture strength prediction method for notched structures will have significant practical value for the safety design and reliability assessment of structural components. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for predicting the fracture strength of notched structural components, so as to solve the technical problem that it is difficult to quantitatively characterize the influence of different notch geometric parameters on fracture strength in the existing technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for predicting the fracture strength of a notched structural member, specifically including the following steps:

[0007] Step 1: Determine the average grain size G and tensile strength f of the quasi-brittle material of the component to be tested. t ;

[0008] Step 2: Measure the notch geometry parameters of the component to be tested;

[0009] Step 3: Based on the average grain size G and tensile strength f of the component to be tested obtained in Step 1... t The fracture strength σ is calculated using the notch geometry parameters obtained in step two. N .

[0010] This invention also includes the following technical features:

[0011] The notch geometry parameters include the initial notch depth a0, the root radius ρ, and the opening angle α.

[0012] In step three, the average grain size G and tensile strength f of the component to be tested obtained in step one are used... t The initial notch depth a0, root radius ρ, and opening angle α are input into formula (1) to calculate the fracture strength σ. N ;

[0013]

[0014]

[0015]

[0016]

[0017]

[0018] in:

[0019] f t Indicates tensile strength (MPa);

[0020] a0 represents the initial notch depth (m);

[0021] 'a' represents the effective gap depth (m);

[0022] a * Indicates the depth of the characteristic notch; a *

[0023] K t Indicates the stress concentration factor;

[0024] ρ represents the root radius (m);

[0025] α represents the opening angle;

[0026] q, ω, λ represent parameters determined by the opening angle α;

[0027] Y represents the geometric influence factor;

[0028] G represents the average grain size (m).

[0029] Compared with the prior art, the beneficial technical effects of this invention are:

[0030] (I) This invention establishes a fracture strength prediction model for quasi-brittle material components by combining macroscopic and microscopic parameters. Compared with fracture models that rely solely on macroscopic parameters, this invention considers the differences in mechanical properties of different quasi-brittle materials from the perspective of microstructure, and can analyze fracture behavior from the perspective of microscopic mechanism. This solves the technical problem in the prior art that it is difficult to quantitatively characterize the influence of different notch geometry parameters on fracture strength.

[0031] (II) This invention quantitatively characterizes the influence of different notch geometry parameters (initial notch depth, root radius, opening angle) and microstructure size parameters (average grain size) on fracture strength, and proposes a fracture strength model. This model only includes notch size parameters and average grain size. Therefore, given the grain size and component notch size, the fracture strength of notched components made of different quasi-brittle materials can be predicted using the fracture strength model.

[0032] (III) This invention proposes an expression for the stress concentration factor determined by the notch geometry. The proposed expression can effectively characterize the stress concentration of different notches. Attached Figure Description

[0033] Figure 1 This is a predicted curve showing the relationship between fracture strength and notch depth.

[0034] Figure 2 The predicted curve shows the relationship between fracture strength and stress concentration factor.

[0035] Figure 3 A schematic diagram comparing the predicted curve of the relationship between fracture strength and notch depth with experimental data;

[0036] Figure 4 This is a schematic diagram comparing the predicted curve of the relationship between fracture strength and stress concentration factor with experimental data.

[0037] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0038] It should be noted that the documents involved in this invention are:

[0039] [1]Justo J.,Castro J.,Cicero S.,et al.Notch effect on the fracture ofseveral rocks:application of the theory of critical distances[J].Theoreticaland Applied Fracture Mechanics,2017,90:251-258.

[0040] [2]Carolan D.,Alveen P., A.,et al.Effect of notch rootradius on fracture toughness of polycrystalline cubic boron nitride[J].Engineering Fracture Mechanics,2011,78:2885-2895.

[0041] [3]Ayatollahi M.R.,Torabi A.R..Tensile fracture in notchedpolycrystalline graphite specimens[J].Carbon,2010,48:2255-2265.

[0042] [4]Noda N.A.,Takase Y..Generalized stress intensity factors of V-shaped notch in a round bar under torsion,tension,and bending[J].EngineeringFracture Mechanics,2003,70:1447-1466.

[0043] [5]Gross B.,Mendelson A..Plane elastostatic analysis of V-notchedplates[J].International Journal of Fracture Mechanics,1972,8:267-276.

[0044] [6]ASTM E399, Standard test method for linear-elastic plane-strainfracture toughness KIc of metallic materials[S].2009.

[0045] It should be noted that, unless otherwise specified, all components in this invention are those known in the art.

[0046] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0047] This invention provides a method for predicting the fracture strength of a notched structural member, specifically including the following steps:

[0048] Step 1: Determine the average grain size G and tensile strength f of the quasi-brittle material of the component to be tested. t ;

[0049] Step 2: Measure the notch geometry parameters of the component to be tested;

[0050] Step 3: Based on the average grain size G and tensile strength f of the component to be tested obtained in Step 1... t The fracture strength σ is calculated using the notch geometry parameters obtained in step two. N .

[0051] In the above technical solution, a fracture strength prediction model for quasi-brittle material components is established by combining macroscopic and microscopic parameters. Compared with fracture models that rely solely on macroscopic parameters, this invention considers the differences in mechanical properties of different quasi-brittle materials from the perspective of microstructure, and can analyze fracture behavior from the perspective of microscopic mechanism. This solves the technical problem in the prior art that it is difficult to quantitatively characterize the influence of different notch geometry parameters on fracture strength.

[0052] Specifically, the notch geometry parameters include the initial notch depth a0, the root radius ρ, and the opening angle α.

[0053] The above technical solution quantitatively characterizes the influence of different notch geometry parameters (notch depth, root radius, opening angle) and microstructure size parameters (average grain size) on fracture strength, and proposes a fracture strength model. This model only includes notch size parameters and average grain size. Therefore, given the grain size and component notch size, the fracture strength of notched components made of different quasi-brittle materials can be predicted using the fracture strength model.

[0054] Specifically, in step three, the average grain size G and tensile strength f of the component to be tested obtained in step one are used... t The fracture strength σ is calculated by inputting the initial notch depth a0, root radius ρ, and opening angle α into formula (1). N ;

[0055]

[0056]

[0057]

[0058]

[0059]

[0060] in:

[0061] f t Indicates tensile strength (MPa);

[0062] a0 represents the initial notch depth (m);

[0063] 'a' represents the effective gap depth (m);

[0064] a * Indicates the depth of the feature gap;

[0065] K t Indicates the stress concentration factor;

[0066] ρ represents the root radius (m);

[0067] α represents the opening angle;

[0068] q, ω, λ represent parameters determined by the opening angle α;

[0069] Y represents the geometric influence factor;

[0070] G represents the average grain size (m).

[0071] In the above technical solution, the geometric influence factor Y can be determined by the notch geometry parameters of the component to be tested, such as the sample width, notch depth, and root radius. The geometric influence factors Y of the circumferential V-notch round bar sample, the V-notch rectangular sample, the crack sample, and the U-notch sample can be obtained by the calculation methods in references [4], [5], and [6], respectively.

[0072] This scheme proposes an expression for the stress concentration factor determined by the notch geometry. This expression can effectively characterize the stress concentration of different notches.

[0073] Example:

[0074] This embodiment selects some data from literature related to the fracture strength of structural members with different notches for analysis, as shown in Table 1, and compares them with the prediction results of the model in this paper. The results are as follows: Figure 3 and Figure 4 As shown.

[0075] Table 1. Experimental and Predictive Data of Notched Structural Components from Different Literature

[0076]

Claims

1. A method for predicting the fracture strength of a structural member with a notch, characterized in that, Specifically, the following steps are included: Step 1: Determine the average grain size of the quasi-brittle material of the component to be tested. G and tensile strength f t ; Step two, measure the notch geometry parameters of the component to be tested; the notch geometry parameters include the initial notch depth. a 0. Root radius ρ Opening angle α ; Step 3: Based on the average grain size of the component to be tested obtained in Step 1... G ,tensile strength f t The fracture strength is calculated using the notch geometry parameters obtained in step two. ; （1） （2） （3） （4） （5） in: f t Indicates tensile strength (MPa); a 0 indicates the initial notch depth (m); a Indicates the effective notch depth (m); a Indicates the depth of the feature gap; K t Indicates the stress concentration factor; ρ Indicates the root radius (m); α Indicates the opening angle; q, ω, λ represent the opening angles. α Determined parameters; Y Indicates the geometric influence factor; G This represents the average grain size (m).

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