A method for predicting the tensile strength of a material notch by damage amplification

Abstract

The application discloses a method for predicting the notched tensile strength of metal materials by damage amplification, and belongs to the technical field of material science and engineering. t The method explores the tensile properties and damage changes of materials under different stress concentration coefficients K t , analyzes the tensile damage amplification between notched and smooth samples, constructs a relationship with K t , and determines material parameters, so that a method for predicting the notched tensile strength based on the stress concentration effect is established. The application establishes the relationship between the stress concentration effect and the tensile strength through easy-to-measure tensile experiments, and the method is simple, fast, high in prediction accuracy, and has engineering value for popularization and application.

Description

Technical Field

[0001] This invention relates to the field of materials science and engineering application technology, specifically a method for predicting the notched tensile strength of materials by damage amplification. Background Technology

[0002] Since the Industrial Revolution, to address the contradiction between socio-economic needs and insufficient productivity, large-scale equipment in many fields has tended towards systematization and structural complexity. Determining the strength limits of components is crucial to ensuring structural integrity and equipment safety. However, most components have complex shapes, exhibiting geometric discontinuities such as tenons, chamfers, and holes. During service, these components are prone to localized stress concentration, severely impacting their service life. Therefore, establishing a method for predicting notched tensile strength is essential to avoid serious accidents.

[0003] Current research on notch strength in structural components primarily relies on finite element stress analysis. However, selecting appropriate fracture criteria and material elastic-plastic models is crucial for different components and operating conditions, directly impacting the accuracy of predictions and inevitably involving complex analysis and experimental verification. Given current research trends, tensile testing will remain one of the most reliable methods for studying the fundamental properties of materials and components for a considerable period. Therefore, exploring methods for predicting notch tensile strength by analyzing material notch sensitivity and damage amplification due to stress concentration effects through experimental data and sample characterization is of significant importance. Summary of the Invention

[0004] To improve the efficiency of predicting notched tensile strength, the present invention aims to provide a method for predicting the notched tensile strength of a material by damage amplification, thereby achieving accurate and efficient prediction of notched tensile strength.

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

[0006] A method for predicting the notched fatigue strength of metallic materials, the method specifically includes the following steps:

[0007] (1) Prepare smooth specimens and at least one set of notched specimens of the target metallic material; the theoretical stress concentration factor K of the smooth specimens. t =1, stress concentration factor K of the notched specimen t >1;

[0008] (2) Tensile properties were tested on smooth and notched specimens of the target metallic material. The tensile strength σ of the smooth specimen was obtained through the tensile test. b The tensile strength σ of the notched specimen bn ;

[0009] (3) Substitute the tensile strength data obtained in step (2) into formula (1) to obtain K in step (1). t The parameter value M at the time of value K ;

[0010]

[0011] (4) The parameter value M obtained in step (3) K With the corresponding K t The value is fitted using formula (2) to obtain the parameter value C;

[0012]

[0013] (5) Combine the obtained parameter value C with the tensile strength σ of the smooth specimen. b Substituting into formula (3), the K value of the material can be calculated. t Notched tensile strength σ >1 bn The predicted value;

[0014]

[0015] In step (1) above, tensile tests on smooth and notched specimens need to be conducted under the same loading conditions, such as ambient atmosphere, loading type, number of cycles, and test temperature. To ensure high prediction accuracy, two or more groups with different K values ​​can be selected. t The test was conducted using notched specimens; in addition, to ensure the repeatability of the test, at least 3 specimens were required for each group of tensile tests, and the tensile strength could be taken as the average value.

[0016] In step (3) and formula (1) above, the parameter value M of the smooth sample is... K It is 0, and is consistent with the M of the notched specimen. K The value is used to fit the formula (2).

[0017] The advantages and beneficial effects of this invention are as follows:

[0018] 1. This invention, based on a deep understanding of the damage nature of notched tensile tests, comprehensively considers the influence of stress concentration effect on the tensile damage mechanism of materials, quantifies the damage increase of components with smoother notches, and has clear physical significance.

[0019] 2. This invention involves fewer material parameters and is simple and quick to calculate. Different K values ​​can be predicted through two sets of tensile tests. t The tensile properties of notched specimens require fewer samples for experimental data, saving a significant amount of time and manpower.

[0020] 3. The prediction method of the present invention has high accuracy and still has a small prediction deviation for notched specimens with high stress concentration effect, and has the value of promotion and application. Attached Figure Description

[0021] Figure 1 For metallic materials at different K t Flowchart of the method for predicting notched tensile strength under certain conditions.

[0022] Figure 2 The 25CrNiMoV steel in Example 1 at different K t Predicted tensile strength of notched material under the given conditions; where: (a) Experimental data K t With M K (a) The relationship between predicted and experimental values; (b) The relationship between predicted and experimental values.

[0023] Figure 3 For example, the 30XH2MΦA martensitic steel in Example 2 is used at different K... t Predicted tensile strength of notched material under the given conditions; where: (a) Experimental data K t With M K (a) The relationship between predicted and experimental values; (b) The relationship between predicted and experimental values. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] Figure 1 The metallic materials of the present invention are at different K t The operation process of the method for predicting the tensile strength of notches under certain conditions is described below. This method is simple, fast, and highly accurate. The following is an explanation with reference to an example.

[0026] Example 1:

[0027] This embodiment is for different K t Predicting the notched tensile strength of 25CrNiMoV steel, for smooth (K) t =1), K t Tensile tests were conducted on specimens with a notch value of 3 to determine their tensile strength (experimental data), which was then used to predict the notched tensile strength of the remaining untested notched specimens (verification data).

[0028] Step 1: Perform a tensile test on 25CrNiMoV steel. The tensile strength σ of the smooth specimen is... b 805 MPa, K t =3 Notched tensile strength σ of the specimen bn The value is 1240 MPa, as shown in Table 1.

[0029] Step 2: Substitute the above experimental data into the formula. Calculations were performed to obtain the material's K... t =1 and K t =3 of M KThe values ​​are 0 and 0.540, respectively.

[0030] Step 3, obtain the parameter M as described above. K The values ​​0 and 0.540 correspond to K respectively. t =1 and K t =3 via formula Perform fitting (e.g.) Figure 2 As shown in (a), the parameter C value was obtained as 0.708.

[0031] Step four, combine the obtained parameter C value of 0.708 and the tensile strength σ of the smooth specimen. w =805MPa Substitute into the formula In this process, the material at different K values ​​can be obtained. t Lower fatigue strength σ bn The predicted values ​​are shown in Table 1.

[0032] Step 5: To verify the accuracy of the predicted data, calculate the deviation of the predicted notched tensile strength of the remaining untested notched specimens. The deviation values ​​are shown in Table 1. The accuracy of the prediction is as follows: Figure 2 As shown in (b), the prediction deviations are all within ±5% (this step is to verify the method and can be omitted in actual operation).

[0033] Table 1 25CrNiMoV steel at different K t Summary table of data related to the predicted notch tensile strength under certain conditions

[0034]

[0035] Example 2:

[0036] This embodiment is for different K t Predicting the notched tensile strength of 30XH2MΦA martensitic steel, for smooth (K) t =1), K t Tensile tests were conducted on specimens with a strength of 3.7 to determine their tensile strength (experimental data), which was then used to predict the notched tensile strength of the remaining untested notched specimens (validation data).

[0037] Step 1: Perform a tensile test on 30XH2MΦA martensitic steel, and determine the tensile strength σ of the smooth specimen. b 1042 MPa, K t =3 Notched tensile strength σ of the specimen bn The value is 1782 MPa, as shown in Table 2.

[0038] Step 2: Substitute the above experimental data into the formula. Calculations were performed to obtain the material's K... t =1 and K t =3.7 of MK The values ​​are 0 and 0.710, respectively.

[0039] Step 3, obtain the parameter M as described above. K The values ​​0 and 0.710 correspond to K respectively. t =1 and K t =3.7 by formula Perform fitting (e.g.) Figure 3 As shown in (a), the parameter C value was obtained as 0.946.

[0040] Step four, combine the obtained parameter C value of 0.946 and the tensile strength σ of the smooth specimen. w =1042MPa substituted into the formula In this process, the material at different K values ​​can be obtained. t Lower fatigue strength σ bn The predicted values ​​are shown in Table 2.

[0041] Step 5: To verify the accuracy of the predicted data, calculate the deviation of the predicted notched tensile strength of the remaining untested notched specimens. The deviation values ​​are shown in Table 1. The accuracy of the prediction is as follows: Figure 3 As shown in (b), most prediction errors are within ±15% (this step is to verify the method and can be omitted in actual operation).

[0042] Table 2 30XH2MΦA martensitic steel at different K t Summary table of data related to the predicted notch tensile strength under certain conditions

[0043]

[0044] The above embodiments are merely illustrative of the principles and performance of the present invention and are not exhaustive. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for predicting the notched tensile strength of a material by damage amplification, characterized in that: The method specifically includes the following steps: (1) Prepare smooth specimens and at least one set of notched specimens of the target metallic material; the theoretical stress concentration factor K of the smooth specimens. t =1, stress concentration factor K of the notched specimen t >1; (2) Tensile properties were tested on smooth and notched specimens of the target metallic material. The tensile strength σ of the smooth specimen was obtained through the tensile test. b The tensile strength σ of the notched specimen bn ; (3) Substitute the tensile strength data obtained in step (2) into formula (1) to obtain K in step (1). t The parameter value M at the time of value K ; (4) The parameter value M obtained in step (3) K With the corresponding K t The value is fitted using formula (2) to obtain the parameter value C; (5) Combine the obtained parameter value C with the tensile strength σ of the smooth specimen. b Substituting into formula (3), the K value of the material can be calculated. t Notched tensile strength σ >1 bn The predicted value; 2. The method for predicting the notched tensile strength of a material by damage amplification according to claim 1, characterized in that: In step (1), tensile tests of smooth and notched specimens need to be conducted under the same loading conditions; to ensure high prediction accuracy, two or more groups with different K values ​​can be selected. t The test was conducted using notched specimens; in addition, to ensure the repeatability of the test, at least 3 specimens were required for each group of tensile tests, and the tensile strength could be taken as the average value.

3. The method for predicting the notched tensile strength of a material by damage amplification according to claim 2, characterized in that: The loading conditions include ambient atmosphere, loading type, number of cycles, and test temperature.

4. The method for predicting the notched tensile strength of a material by damage amplification according to claim 1, characterized in that: In step (3) of formula (1), the parameter value M of the smooth sample is... K It is 0, and is consistent with the M of the notched specimen. K The value is fitted by formula (2).

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