A method for determining the effect of plastic deformation on the tensile properties of a metal material

Abstract

The application provides a method for determining the influence of plastic deformation on the tensile property of a metal material, comprising the following steps: S1, processing the metal material into a test sample and performing a tensile property test; S2, pretreating the test sample at different plastic deformation rates according to the total elongation rate of the maximum force measured in step S1, obtaining tensile test samples under different plastic deformation conditions, and performing a mechanical property test; S3, establishing a relationship model of the yield strength and the plastic deformation rate according to the test results in steps S1 and S2; S4, converting the engineering stress-strain data measured in steps S1 and S2 into true stress-strain data, and obtaining the true stress-strain curves after different plastic deformation treatments; and S5, establishing a relationship model of the true stress and the true yield strength-tensile strength-strain under different plastic deformation rates; the application can accurately calculate and predict the yield strength and the true stress-strain curve of the metal material after different plastic deformations, and provides theoretical support for ensuring the safe service of metal parts.

Description

Technical Field

[0001] This invention relates to the field of tensile property testing technology for metallic materials, and in particular to a method for determining the effect of plastic deformation on the tensile properties of metallic materials. Background Technology

[0002] Metallic materials possess excellent mechanical properties, good cold and hot workability, and good weldability, thus they are widely used in the manufacture of mechanical structural components that bear high loads, such as ships and pressure vessels. During actual service, the complex and variable working environment, short-term overloads, and collisions can cause localized plastic deformation in components, leading to changes in the mechanical properties of the material and affecting the normal service life of the component. In engineering, components with localized plastic deformation are usually replaced, which significantly increases the manufacturing and maintenance costs of equipment and wastes resources. Therefore, accurately assessing the impact of plastic deformation on the mechanical properties of metallic materials is a major challenge currently faced in engineering.

[0003] In the existing technology, Yang Gang (Yang Gang, Gao Yongliang, Wang Limin, et al. Influence of plastic deformation method on mechanical properties of austenitic stainless steel [J]. Iron and Steel, 2007, 42(02): 0047-0050.) et al. found that the grain size and yield strength of the samples obtained by different plastic deformation methods are significantly different. The yield strength of the samples decreased by about 10% after equal diameter angular hot extrusion deformation treatment. Bakhshi (R.Bakhshi, MHFarshidi, SASajjadi. Strengthening of aluminum alloy 7005 through imposition of severe plastic deformation supplemented by different aging treatments[J].Trans.Nonferrous Met.Soc.China,2021,31:2909-2921.) et al. found in their study on the mechanical properties of 7005 aluminum alloy after large plastic deformation treatment that the mechanical properties of the samples after "large plastic deformation treatment + aging treatment" were better than those of the samples after conventional "solution treatment + aging treatment". The yield strength of the samples after large plastic deformation can be increased by about 25% compared with the undeformed samples.

[0004] Although existing technologies have conducted research on the influence of plastic deformation on the mechanical properties of metallic materials, these studies are all qualitative analyses of experimental results and have failed to clarify the quantitative calculation relationship between the amount of plastic deformation and tensile property parameters. Therefore, exploring the influence law of plastic deformation on the tensile properties of metallic materials and establishing a calculation model between the amount of plastic deformation and tensile property parameters are of great significance for ensuring the normal service of metallic materials. Summary of the Invention

[0005] Given that most current research on the influence of plastic deformation on the tensile properties of materials focuses on qualitative analysis of specific experimental results, and there are no reports on accurate quantitative calculations, this invention aims to propose a method for determining the influence of plastic deformation on the tensile properties of metallic materials. In particular, it proposes a model relating the plastic deformation rate to the yield strength of the material, as well as a model relating the true stress to the true yield strength-tensile strength-strain ratio. This model can accurately calculate and predict the yield strength and true stress-strain curves of metallic materials after different plastic deformations, providing theoretical support for ensuring the safe service of metallic components.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for determining the effect of plastic deformation on the tensile properties of metallic materials includes: S1, processing a homogeneous metallic material into a standard circular tensile specimen, and performing tensile property tests on the processed specimen to obtain engineering stress-strain curves, yield strength, tensile strength, and total elongation at maximum force; S2, based on the total elongation at maximum force obtained in step S1, performing plastic deformation pretreatment on the specimen with different plastic deformation rates to obtain tensile specimens under different plastic deformation conditions, and performing mechanical property tests on the tensile specimens to obtain engineering stress-strain curves, yield strength, tensile strength, and total elongation at maximum force of the specimens after plastic deformation; S3, based on the test results in steps S1 and S2, establishing a relationship model between the yield strength and plastic deformation rate of the material after different plastic deformation treatments; S4, converting the engineering stress-strain data measured in steps S1 and S2 into true stress-strain data to obtain true stress-strain curves after different plastic deformation treatments; S5, establishing a relationship model between the true stress and true yield strength-tensile strength-strain of the material under different plastic deformation rates.

[0008] Furthermore, in step S1, the uniformly composed metallic material is processed into a standard round tensile specimen according to the requirements of GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". Then, the processed specimen is tested using an electronic universal testing machine with an accuracy of 0.5 grade, and the strain of the specimen in the uniform deformation stage during the tensile process is measured using an extensometer with an accuracy of 0.5 grade, so as to obtain the engineering stress-strain curve, yield strength, tensile strength and total elongation at maximum force of the original specimen.

[0009] Furthermore, in step S2, the corresponding specimens are subjected to plastic deformation pretreatment with plastic deformation rates of 10%, 30%, 50%, 70%, and 100% respectively to obtain tensile specimens under the corresponding plastic deformation conditions.

[0010] Furthermore, in step S2, the formula for calculating the plastic deformation rate is: Where r is the plastic deformation rate; ε T A represents the total strain during the pre-deformation process; gt This represents the total elongation at maximum force of the original material.

[0011] Further, step S3 includes: S31, based on the test results in steps S1 and S2, analyzing the variation trend of the yield strength of the material after different plastic deformation treatments, and using data processing software to fit the relationship between the yield strength and the total strain of plastic deformation, establishing the relationship between the yield strength and the total strain of plastic deformation of the material after different plastic deformation treatments: σ sp =σ s *(1+ln(1+k1*ε T 3*m S32, the formula for calculating the plastic deformation rate. Substituting the relationship between yield strength and total plastic deformation strain in step S31, we obtain the relationship model between yield strength and plastic deformation rate of materials after different plastic deformation treatments: Where, σ sp σ represents the yield strength of the specimen after plastic deformation pretreatment. s denoted as the yield strength of the original specimen, k1 as the strain hardening coefficient, and m as the strain hardening exponent.

[0012] Furthermore, in step S4, the relationship between the engineering stress-strain data and the true stress-strain data is: ε t =ln(1+ε); σ t =σ*(1+ε); where ε is the measured engineering strain and σ is the measured engineering stress; ε t For true strain, σ t This is the true stress.

[0013] Furthermore, in step S4, based on the relationship between engineering stress-strain data and true stress-strain data, the engineering stress-strain curves of the specimens under different plastic deformation conditions in the uniform deformation stage measured in steps S1 and S2 are converted into true stress-strain curves.

[0014] Furthermore, in step S5, based on the true stress-strain curve obtained in step S4, a model is established to represent the relationship between the true stress and the true yield strength-tensile strength-strain of the material after different plastic deformation treatments: the elastic stage is σ p，t =E p，t *ε p，t The plastic stage is Where, σ p,t σ is the true stress under tension after plastic deformation. p,tb σ is the true tensile strength after plastic deformation. p,ts ε is the true yield strength after plastic deformation. p,t E represents the true strain under tension after plastic deformation. p,t is the elastic modulus under tension after plastic deformation, k2 is the hardening coefficient, and n is the strain hardening exponent.

[0015] Compared with existing technologies, the method for determining the effect of plastic deformation on the tensile properties of metallic materials described in this invention has the following advantages:

[0016] This invention discloses a method for determining the influence of plastic deformation on the tensile properties of metallic materials. This method involves pre-treating tensile specimens of uniformly composed metallic materials under different plastic deformation conditions, and then conducting tensile tests on the specimens after plastic deformation treatment. Stress-strain data of the specimens under different plastic deformation conditions are obtained. Based on this, a model is established to represent the relationship between the plastic deformation rate and the material's yield strength, as well as the relationship between the material's true stress and its true yield strength-tensile strength-strain ratio. This method allows for accurate calculation and prediction of the yield strength and true stress-strain curves of metallic materials after different plastic deformations, yielding calculation results that closely match actual measurement data. This provides theoretical support for ensuring the safe service of metallic components. Attached Figure Description

[0017] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 These are the engineering stress-strain curves of the specimens under different plastic deformation conditions in this invention;

[0019] Figure 2 This is a comparison between the yield strength calculated by the model of plastic deformation rate and material yield strength in this invention and the measured yield strength.

[0020] Figure 3 These are the true stress-strain curves of the specimens during the uniform deformation stage under different plastic deformation conditions in this invention.

[0021] Figure 4 This invention compares the true stress-strain curves predicted by the model of true stress and true yield strength-tensile strength-strain for the material with measured data. Detailed Implementation

[0022] The inventive concepts of this disclosure will be described below using terminology commonly used by those skilled in the art to communicate the essence of their work to others skilled in the art. However, these inventive concepts may be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

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

[0025] Given that most current research on the influence of plastic deformation on the tensile properties of materials focuses on qualitative analysis of specific experimental results, and there are no reports on accurate quantitative calculations, this embodiment proposes a method for determining the influence of plastic deformation on the tensile properties of metallic materials, including:

[0026] S1. Process the uniform metal material into a standard round tensile specimen, and perform tensile property tests on the processed specimen to obtain the engineering stress-strain curve, yield strength, tensile strength and total elongation at maximum force.

[0027] In this process, uniformly composed metallic materials are processed into standard round tensile specimens according to the relevant requirements in GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". The processed specimens are then tested using an electronic universal testing machine with an accuracy of 0.5 grade, and the strain of the specimens during the uniform deformation stage is measured using an extensometer with an accuracy of 0.5 grade. The engineering stress-strain curves, yield strength, tensile strength and total elongation at maximum force of the original specimens are obtained.

[0028] S2. Based on the total elongation of the maximum force obtained in step S1, the specimens are subjected to plastic deformation pretreatment with different plastic deformation rates to obtain tensile specimens under different plastic deformation conditions. The mechanical properties of the tensile specimens are then tested to obtain the engineering stress-strain curves, yield strength, tensile strength and total elongation of the maximum force of the specimens after plastic deformation.

[0029] The mechanical property test performed in step S2 is consistent with the tensile property test performed in step S1. Preferably, in step S2, the corresponding specimens are subjected to plastic deformation pretreatment at plastic deformation rates of 10%, 30%, 50%, 70%, and 100% to obtain tensile specimens under the corresponding plastic deformation conditions. To avoid ambiguity, the plastic deformation condition in this application refers to a certain plastic deformation rate, which can also be understood as the degree of plastic deformation.

[0030] The formula for calculating the plastic deformation rate is:

[0031]

[0032] Where r is the plastic deformation rate; ε T A represents the total strain during the pre-deformation process; gt This represents the total elongation at maximum force of the original material.

[0033] S3. Based on the test results in steps S1 and S2, establish a model relating the yield strength and plastic deformation rate of materials after different plastic deformation treatments.

[0034] Step S3 includes:

[0035] S31. Based on the test results in steps S1 and S2, analyze the changing trend of the yield strength of the material after different plastic deformation treatments, and use data processing software to fit the relationship between yield strength and total plastic deformation strain, establishing the relationship between yield strength and total plastic deformation strain of the material after different plastic deformation treatments: σ sp =σ s *(1+ln(1+k1*ε T 3*m ));

[0036] S32, the formula for calculating the plastic deformation rate. Substituting the relationship between yield strength and total plastic deformation strain in step S31, we obtain the relationship model between yield strength and plastic deformation rate of materials after different plastic deformation treatments:

[0037] Where, σ sp σ represents the yield strength of the specimen after plastic deformation pretreatment. s denoted as the yield strength of the original specimen, k1 as the strain hardening coefficient, and m as the strain hardening exponent.

[0038] S4. Convert the engineering stress-strain data measured in steps S1 and S2 into true stress-strain data to obtain true stress-strain curves after different plastic deformation treatments.

[0039] The relationship between engineering stress-strain data and true stress-strain data is as follows:

[0040] ε t =ln(1+ε)

[0041] σ t =σ*(1+ε)

[0042] Where ε is the measured engineering strain and σ is the measured engineering stress; ε t For true strain, σ t This is the true stress.

[0043] Based on the relationship between engineering stress-strain data and true stress-strain data, the engineering stress-strain curves of the specimens under different plastic deformation conditions in the uniform deformation stage measured in steps S1 and S2 are converted into true stress-strain curves.

[0044] S5. Establish a model relating true stress to true yield strength-tensile strength-strain under different plastic deformation rates, and compare and verify it with measured data.

[0045] Specifically, based on the true stress-strain curves obtained in step S4, the true tensile strength and true yield strength data of the material after plastic deformation treatment are extracted by analyzing the true stress-strain curves under different plastic deformation conditions. A preliminary mathematical model conforming to the relationship of the true stress-strain curves is established based on the true tensile strength, true yield strength, and true stress-strain curves. The mathematical model is then fitted and corrected using measured data in data processing software to establish a model relating the true stress to the true yield strength-tensile strength-strain relationship of the material after different plastic deformation treatments.

[0046] The elastic phase is σ p，t =T p，t *ε p，t

[0047] The plastic stage is

[0048] Where, σ p,t σ is the true stress under tension after plastic deformation. p,tb σ is the true tensile strength after plastic deformation. p,ts ε is the true yield strength after plastic deformation. p,t E represents the true strain under tension after plastic deformation. p,t is the elastic modulus under tension after plastic deformation, k2 is the hardening coefficient, and n is the strain hardening exponent.

[0049] Example 1

[0050] A1. Low-alloy structural steel of uniform composition is processed into standard round tensile specimens according to the relevant requirements in GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". Then, the processed specimens are tested using an electronic universal testing machine with an accuracy of 0.5 grade. During the test, the crossbeam displacement is controlled at a rate of 0.45 mm / min. The strain of the specimen in the uniform deformation stage during the tensile process is measured using an extensometer with an accuracy of 0.5 grade. The engineering stress-strain curve, yield strength, tensile strength and total elongation at maximum force of the original specimen are obtained.

[0051] A2. Based on the test results of step A1, the specimens were subjected to plastic deformation pretreatment at 10%, 30%, 50%, 70%, and 100% of the total elongation at maximum force of the original specimens, respectively, to obtain pre-deformed specimens under different plastic deformation conditions. Subsequently, the specimens were tested according to the tensile property testing method in step A1 to obtain the engineering stress-strain curves of the specimens under different plastic deformation levels (as shown in the attached figure). Figure 1 As shown in Table 1, the yield strength, tensile strength, and total elongation at maximum force are as follows.

[0052] Table 1. Relevant test results of specimens after different plastic deformations.

[0053]

[0054] A3. Based on the test results in steps A1 and A2, through... Figure 2 The variation trend of yield strength of materials after different plastic deformation treatments was analyzed. The relationship between yield strength and total plastic deformation strain was fitted and corrected using 1stOpt software, establishing the relationship between yield strength and total plastic deformation strain after different plastic deformation treatments: σ sp =σ s *(1+ln(1+k1*ε T 3*m )).

[0055] A4. The formula for calculating the plastic deformation rate. Substituting the relationship between yield strength and total plastic deformation strain from step A3, we obtain the model showing the relationship between yield strength and plastic deformation rate of materials after different plastic deformation treatments: Where k1 = 0.039 and m = 0.312, the model calculation data is validated using measured data, and the comparison between the measured data and the calculated data is as follows: Figure 2As shown, after data comparison calculation using 1stOpt software, the correlation coefficient between the theoretical data and the measured data obtained by the relationship model between yield strength and plastic deformation rate of this application is 0.98. Therefore, the relationship model between plastic deformation rate and yield strength established by this invention can be used to calculate the yield strength of materials under different plastic deformation conditions, and can obtain calculation results that are more consistent with actual measurement data, which is conducive to providing theoretical support for ensuring the safe service of metal components.

[0056] A5. Based on the relationship between engineering stress-strain data and true stress-strain data: ε t =1n(1+ε),σ t =σ*(1+ε), converting the engineering stress-strain curves of the specimens under different plastic deformation conditions in the uniform deformation stage obtained in steps A1 and A2 into true stress-strain curves, where the true stress-strain curves of the specimens after different plastic deformation treatments in the uniform deformation stage are as follows. Figure 3 As shown.

[0057] A6. Based on the true stress-strain curve obtained in step A5 (e.g.) Figure 3 As shown), through the Figure 3 Measured true stress-strain curves under different plastic deformation conditions were analyzed to extract the true tensile strength and true yield strength data of the material after plastic deformation treatment. Based on the true tensile strength, true yield strength, and true stress-strain curves, a preliminary mathematical model conforming to the relationship of the true stress-strain curves was established. The mathematical model was then fitted and corrected using measured data in 1stOpt software to establish a model relating true stress to true yield strength-tensile strength-strain of the material after different plastic deformation treatments.

[0058] The elastic phase is σ p，t =∑ p，t *ε p，t

[0059] The plastic stage is

[0060] The relevant parameters in this model are shown in Table 2.

[0061] Table 2. Relevant parameters in the model of true stress and true yield strength-tensile strength-strain relationship of materials.

[0062] Original sample 190021 1.2322 0.1917 10% pre-deformation 182650 1.2866 0.2404 30% pre-deformation 174050 1.2598 0.2159 50% pre-deformation 160597 1.4557 0.3272 70% pre-deformation 159262 1.7381 0.4559 100% pre-deformation 162483 2.2225 0.5309

[0063] The model in step A6 was used to calculate the true stress-strain data of specimens after different plastic deformation treatments during the uniform deformation stage. The measured data and calculated data were then compared and verified. The comparison results are as follows: Figure 4As shown. Based on the comparison results, data comparison calculations were performed using 1stOpt software. The correlation coefficients between the calculated data and the measured data of the true stress-strain curves under different plastic deformation conditions obtained by the model in step A6 were all greater than 0.95, indicating good correlation. Therefore, the model in step A6 can be used to calculate the stress-strain relationship of materials after plastic deformation, and can obtain calculation results that are more consistent with actual measurement data, which is beneficial to providing theoretical support for ensuring the safe service of metal components.

[0064] Therefore, the method proposed in this application for determining the influence of plastic deformation on the tensile properties of metallic materials involves pre-treating tensile specimens of uniformly composed metallic materials under different plastic deformation conditions, and then conducting tensile tests on the specimens after plastic deformation treatment to obtain stress-strain data of the specimens under different plastic deformation conditions. Based on this, a model of plastic deformation rate and material yield strength, as well as a model of true stress and true yield strength-tensile strength-strain of the material, are established. Through this method, the yield strength and true stress-strain curves of metallic materials after different plastic deformations can be accurately calculated and predicted, and calculation results that are more consistent with actual measurement data can be obtained, providing theoretical support for ensuring the safe service of metallic components.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for determining the effect of plastic deformation on the tensile properties of metallic materials, characterized in that, The method includes: S1. Process the uniform metal material into a standard round tensile specimen, and perform tensile property tests on the processed specimen to obtain the engineering stress-strain curve, yield strength, tensile strength and total elongation at maximum force. S2. Based on the total elongation of the maximum force obtained in step S1, the specimens are subjected to plastic deformation pretreatment with different plastic deformation rates to obtain tensile specimens under different plastic deformation conditions. The mechanical properties of the tensile specimens are then tested to obtain the engineering stress-strain curves, yield strength, tensile strength and total elongation of the maximum force of the specimens after plastic deformation. S3. Based on the test results in steps S1 and S2, establish a model relating the yield strength and plastic deformation rate of materials after different plastic deformation treatments. S4. Convert the engineering stress-strain data measured in steps S1 and S2 into true stress-strain data to obtain true stress-strain curves after different plastic deformation treatments. S5. Establish a model for the relationship between the true stress and the true yield strength-tensile strength-strain of the material under different plastic deformation rates; Step S3 includes: S31. Based on the test results in steps S1 and S2, analyze the changing trend of the yield strength of the material after different plastic deformation treatments, and use data processing software to fit the relationship between yield strength and total plastic deformation strain, establishing the relationship between yield strength and total plastic deformation strain of the material after different plastic deformation treatments: ; S32, the formula for calculating the plastic deformation rate. Substituting the relationship between yield strength and total plastic deformation strain in step S31, we obtain the relationship model between yield strength and plastic deformation rate of materials after different plastic deformation treatments: ; Where, σ sp σ represents the yield strength of the specimen after plastic deformation pretreatment. s ε is the yield strength of the original specimen, k1 is the strain hardening coefficient, m is the strain hardening exponent; r is the plastic deformation rate; ε T A represents the total strain during the pre-deformation process; gt The maximum total elongation at force of the original material; In step S5, based on the true stress-strain curves obtained in step S4, a model is established to represent the relationship between the true stress and the true yield strength-tensile strength-strain of the materials after different plastic deformation treatments: The elastic phase is ; The plastic stage is ; Where, σ p,t σ is the true stress under tension after plastic deformation. p,tb σ is the true tensile strength after plastic deformation. p,ts ε is the true yield strength after plastic deformation. p,t E represents the true strain under tension after plastic deformation. p,t is the elastic modulus under tension after plastic deformation, k2 is the hardening coefficient, and n is the strain hardening exponent.

2. The method for determining the effect of plastic deformation on the tensile properties of metallic materials according to claim 1, characterized in that, In step S1, the uniformly composed metallic material is processed into a standard round tensile specimen according to the requirements of GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature". Then, the processed specimen is tested using an electronic universal testing machine with an accuracy of 0.5 grade, and the strain of the specimen in the uniform deformation stage during the tensile process is measured using an extensometer with an accuracy of 0.5 grade, so as to obtain the engineering stress-strain curve, yield strength, tensile strength and total elongation at maximum force of the original specimen.

3. The method for determining the effect of plastic deformation on the tensile properties of metallic materials according to claim 1, characterized in that, In step S2, the corresponding specimens are subjected to plastic deformation pretreatment with plastic deformation rates of 10%, 30%, 50%, 70%, and 100% respectively to obtain tensile specimens under the corresponding plastic deformation conditions.

4. The method for determining the effect of plastic deformation on the tensile properties of metallic materials according to claim 1, characterized in that, In step S4, the relationship between the engineering stress-strain data and the true stress-strain data is as follows: ； ； Where ε is the measured engineering strain and σ is the measured engineering stress; ε t For true strain, σ t This is the true stress.

5. The method for determining the effect of plastic deformation on the tensile properties of metallic materials according to claim 4, characterized in that, In step S4, based on the relationship between engineering stress-strain data and true stress-strain data, the engineering stress-strain curves of the specimens under different plastic deformation conditions in the uniform deformation stage measured in steps S1 and S2 are converted into true stress-strain curves.

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