CN117168980A - Method for predicting notch tensile strength of material through damage amplification - Google Patents
Method for predicting notch tensile strength of material through damage amplification Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 28
- 239000000463 material Substances 0.000 title claims abstract description 23
- 230000003321 amplification Effects 0.000 title claims abstract description 8
- 238000003199 nucleic acid amplification method Methods 0.000 title claims abstract description 8
- 238000002474 experimental method Methods 0.000 claims abstract description 13
- 239000007769 metal material Substances 0.000 claims abstract description 8
- 238000012360 testing method Methods 0.000 claims description 9
- 238000009864 tensile test Methods 0.000 claims description 3
- 230000003416 augmentation Effects 0.000 claims 3
- 238000009499 grossing Methods 0.000 claims 2
- 230000000694 effects Effects 0.000 abstract description 5
- 238000004458 analytical method Methods 0.000 abstract description 3
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 4
- 238000012795 verification Methods 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000010200 validation analysis Methods 0.000 description 2
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Abstract
The invention discloses a method for predicting notch tensile strength of a metal material through damage amplification, and belongs to the technical fields of material science and engineering application. The method explores the material in different stress concentration coefficients K t Tensile Property and damage Change under analysis of tensile damage increase between notched and smooth samples and K t And constructing a relation and determining material parameters, so as to establish a method for predicting the notch tensile strength based on the stress concentration effect. The invention establishes the relation between the stress concentration effect and the tensile strength through the tensile experiment easy to measure, and the method is simple and quick, has high prediction precision and has engineering value of popularization and application.
Description
Technical Field
The invention relates to the technical field of material science and engineering application, in particular to a method for predicting the notch tensile strength of a material through damage amplification.
Background
Since the industrial revolution, large equipment in many areas has tended to be systematic and structurally complex in order to solve the contradiction between socioeconomic demands and productivity shortages, while determining the strength limits of the components is critical in order to guarantee structural integrity and equipment safety. Most of the components have complex shapes, have geometrical discontinuities such as mortises, chamfers, holes and the like, easily cause the components to be in a local stress concentration state in the service process, and seriously influence the service life of the components. Therefore, in order to avoid serious accidents, it is necessary to establish a notch tensile strength prediction method.
At present, the research on the component notch is mainly finite element stress analysis, but proper fracture criteria, material elastoplastic models and the like are required to be selected according to different components and working conditions, the accuracy of a predicted result is directly related, and complex analysis and experimental verification are not avoided in the process. In view of the current research trends, tensile experiments have been one of the most reliable means of studying the basic properties of materials and components for a long time in the future. Therefore, by experimental data and sample characterization, it is of great importance to explore methods for predicting notch tensile strength from the notch sensitivity of materials and the damage amplification of stress concentration effects.
Disclosure of Invention
In order to improve the efficiency of predicting the notch tensile strength, the invention aims to provide a method for predicting the notch tensile strength of a material by damage amplification, so as to realize accurate and efficient prediction of the notch tensile strength.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a method for predicting notch fatigue strength of a metallic material, the method comprising the steps of:
(1) Preparing a smooth sample of the target metallic material and at least one set of notched samples; theoretical stress concentration coefficient K of smooth sample t Stress concentration coefficient K of notch specimen =1 t >1；
(2) The tensile property test is carried out on the smooth sample and the notch sample of the target metal material, and the tensile strength sigma of the smooth sample is obtained through a tensile experiment b And tensile Strength sigma of notched specimen bn ；
(3) Substituting the tensile strength data obtained in the step (2) into the formula (1) to obtain K in the step (1) t Parameter value M at value K ；
(4) The parameter value M obtained in the step (3) is obtained K And corresponding K t Fitting the values through a formula (2) to obtain a parameter value C;
(5) The obtained parameter value C and the tensile strength sigma of the smooth sample b Substituting into formula (3), calculating to obtain the material in K t >Notched tensile Strength sigma of 1 bn Is a predicted value of (2);
in the step (1), the stretching experiments of the smooth and notch samples are required to be carried out under the same loading conditions such as ambient atmosphere, loading type, cycle times, test temperature and the like; in order to obtain high prediction accuracy, two or more groups of K can be selected t Carrying out experiments on notch samples; in addition, at least 3 samples are needed for each set of tensile tests to ensure the repeatability of the tests, and the tensile strength can be averaged.
In the above step (3), equation (1), the parameter value M of the smooth sample K 0 and M with notched specimen K The values participate in the formula (2) fit.
The invention has the following advantages and beneficial effects:
1. the method combines deep understanding of the damage essence of the notch stretching experiment, comprehensively considers the influence of the stress concentration effect on the material stretching damage mechanism, quantifies the damage amplification of a member with a smoother notch, and has definite physical significance.
2. The method has the advantages of less material parameters, simple and quick calculation, and different K can be predicted through two groups of stretching experiments t The tensile property of the notch sample of the test piece is small in sample requirement on experimental data, and a large amount of time and people are savedForce cost.
3. The prediction method provided by the invention has higher precision, has smaller prediction deviation for predicting the notch sample with high stress concentration effect, and has popularization and application values.
Drawings
FIG. 1 shows a metal material at different K t And a flow chart of a notch tensile strength prediction method under the condition.
FIG. 2 shows the difference in K for the 25CrNiMoV steel of example 1 t Predicting the tensile strength of the notch under the condition; wherein: (a) Experimental data K t And M is as follows K Is a relationship of (2); (b) relation between predicted value and experimental value.
FIG. 3 is a graph showing the difference in K for 30XH2M phi A martensitic steel of example 2 t Predicting the tensile strength of the notch under the condition; wherein: (a) Experimental data K t And M is as follows K Is a relationship of (2); (b) relation between predicted value and experimental value.
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples.
FIG. 1 shows the metal material of the present invention at different K t The operation flow of the notch tensile strength prediction method under the condition is simple and rapid to operate and high in accuracy, and is described below with reference to examples.
Example 1:
the embodiment is to different K t Notch tensile strength prediction was performed on 25CrNiMoV steel of (1), smooth (K t ＝1)、K t The test specimens of =3 were subjected to a tensile test, the tensile strength was measured (test data), and the tensile strength of the remaining non-tested notched specimens was used to predict (validation data).
Step one, a tensile experiment is carried out on 25CrNiMoV steel, and the tensile strength sigma of a smooth sample is measured b Is 805MPa, K t Notched tensile Strength sigma of sample =3 bn 1240MPa, as shown in table 1.
Step two, substituting the experimental data into a formulaIs performed in the middle ofCalculating to obtain the material in K t =1 and K t M of=3 K The values are 0 and 0.540, respectively.
Step three, the obtained parameter M K The values 0 and 0.540 correspond to K respectively t =1 and K t =3 by the formulaFitting (as shown in fig. 2 (a)) was performed, and a value of 0.708 was obtained for the parameter C.
Step four, the obtained parameter C value is 0.708 and the tensile strength sigma of the smooth sample is w Substituted formula of =805 MPaIn which the material can be obtained at different K t Lower fatigue strength sigma bn Is shown in table 1.
And fifthly, in order to verify the accuracy of the predicted data, calculating and predicting the deviation of the notch tensile strength of the rest non-tested notch samples, wherein the deviation value is shown in table 1, the prediction accuracy is shown in fig. 2 (b), and the prediction deviation is within +/-5% (the step is verification of the method and can be omitted in the actual operation process).
TABLE 1 25CrNiMoV Steel at different K t Condition prediction notch tensile strength related data summary table
Example 2:
the embodiment is to different K t Notch tensile strength prediction was performed on 30XH2MΦA martensitic steel of (C) and sliding (K) t ＝1)、K t Samples=3.7 were subjected to tensile experiments, tensile strength was measured (experimental data) and used to predict notched tensile strength (validation data) for the remaining non-tested notched samples.
Step one, a tensile experiment is carried out on 30XH2M phi A martensitic steel, and the tensile strength sigma of a smooth sample is measured b Is 1042MPa, K t Notched tensile Strength sigma of sample =3 bn 1782MPa, as shown in Table 2.
Step two, substituting the experimental data into a formulaThe calculation is performed to obtain the material in K t =1 and K t M=3.7 K The values are 0 and 0.710, respectively.
Step three, the obtained parameter M K The values 0 and 0.710 correspond to K respectively t =1 and K t =3.7 by the formulaFitting (as shown in fig. 3 (a)) was performed to obtain a value of 0.946 for parameter C.
Step four, the obtained parameter C value is 0.946 and the tensile strength sigma of the smooth sample is w Substituted 1042MPa into formulaIn which the material can be obtained at different K t Lower fatigue strength sigma bn As shown in table 2).
And fifthly, calculating and predicting the deviation of the notch tensile strength of the rest non-tested notch samples in order to verify the accuracy of the predicted data, wherein the deviation value is shown in table 1, the prediction accuracy is shown in fig. 3 (b), and most of the predicted deviation is within +/-15% (the step is verification of the method and can be omitted in the actual operation process).
Table 2 30XH2M phi A martensitic steels at different K t Condition prediction notch tensile strength related data summary table
The foregoing embodiments are merely illustrative of the principles and capabilities of the present invention, and other embodiments can be obtained from the present embodiments without inventive faculty, all of which fall within the scope of the present invention.
Claims (4)
1. A method for predicting the notch tensile strength of a material by damage amplification, which is characterized by comprising the following steps: the method specifically comprises the following steps:
(1) Preparing a smooth sample of the target metallic material and at least one set of notched samples; theoretical stress concentration coefficient K of smooth sample t Stress concentration coefficient K of notch specimen =1 t >1；
(2) The tensile property test is carried out on the smooth sample and the notch sample of the target metal material, and the tensile strength sigma of the smooth sample is obtained through a tensile experiment b And tensile Strength sigma of notched specimen bn ；
(3) Substituting the tensile strength data obtained in the step (2) into the formula (1) to obtain K in the step (1) t Parameter value M at value K ；
(4) The parameter value M obtained in the step (3) is obtained K And corresponding K t Fitting the values through a formula (2) to obtain a parameter value C;
(5) The obtained parameter value C and the tensile strength sigma of the smooth sample b Substituting into formula (3), calculating to obtain the material in K t >Notched tensile Strength sigma of 1 bn Is a predicted value of (2);
2. the method for predicting notched tensile strength of a material by damage augmentation of claim 1, wherein: in the step (1), the smoothing and the smoothing are required to be carried out under the same loading conditionStretching experiments of notch samples; in order to obtain high prediction accuracy, two or more groups of K can be selected t Carrying out experiments on notch samples; in addition, at least 3 samples are needed for each set of tensile tests to ensure the repeatability of the tests, and the tensile strength can be averaged.
3. The method for predicting notched tensile strength of a material by damage augmentation of claim 2, wherein: the loading conditions are ambient atmosphere, loading type, cycle times, test temperature and the like.
4. The method for predicting notched tensile strength of a material by damage augmentation of claim 1, wherein: in the step (3), in the formula (1), the parameter value M of the smooth sample K 0 and M with notched specimen K The values are fitted by equation (2).
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