CN111241670B - Comparative analysis method for fatigue curve of automobile plate - Google Patents
Comparative analysis method for fatigue curve of automobile plate Download PDFInfo
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- CN111241670B CN111241670B CN202010014162.6A CN202010014162A CN111241670B CN 111241670 B CN111241670 B CN 111241670B CN 202010014162 A CN202010014162 A CN 202010014162A CN 111241670 B CN111241670 B CN 111241670B
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- 238000010835 comparative analysis Methods 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 title claims description 10
- 239000000463 material Substances 0.000 claims abstract description 44
- 238000004364 calculation method Methods 0.000 claims abstract description 6
- 238000001514 detection method Methods 0.000 claims abstract description 6
- 238000012935 Averaging Methods 0.000 claims abstract description 3
- 238000004458 analytical method Methods 0.000 abstract description 12
- 238000004088 simulation Methods 0.000 abstract description 8
- 238000005457 optimization Methods 0.000 abstract description 4
- 239000002184 metal Substances 0.000 abstract description 2
- 229910000831 Steel Inorganic materials 0.000 description 7
- 239000010959 steel Substances 0.000 description 7
- 238000013461 design Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
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Abstract
A comparison analysis method for an automobile sheet fatigue curve belongs to the technical field of metal sheet performance detection analysis methods and is used for comparison analysis of the automobile sheet fatigue curve. The technical scheme is as follows: carrying out life detection on the two materials with different strain amplitudes according to the same technical condition; fitting original experimental data to obtain an E-N curve; analyzing the fitting difference value of the experimental data and the E-N curve, and averaging the two data; comparative analysis of the two E-N curves was performed to determine the difference. The invention is the first creation of the automobile sheet fatigue curve comparison analysis method and fills the blank of automobile sheet material analysis. The invention determines the difference of the E-N curve between the two materials by analyzing the error between the experimental data and the E-N curve (fitting curve), thereby judging the quality of the fatigue performance, providing technical support for material optimization and simultaneously providing data support for fatigue simulation calculation of an automobile factory.
Description
Technical Field
The invention relates to a comparative analysis method of an automobile sheet fatigue curve, and belongs to the technical field of metal sheet performance detection and analysis methods.
Background
In the automobile design stage, the fatigue life of the automobile plate can be predicted through the fatigue simulation analysis of the automobile plate, so that the optimization and the structural design of the automobile material are guided, and technical support is provided for the structural design of parts and the material selection of the automobile plate. Through carrying out the fatigue simulation calculation of auto sheet, can shorten the development time of new motorcycle type, avoid simultaneously because the improper, the unreasonable later stage auto sheet fatigue fracture scheduling problem that leads to of structural design of material selection, consequently, the fatigue simulation analysis of auto sheet receives the attention of auto factory and auto sheet material supplier more and more. An important factor influencing the fatigue simulation analysis result of the automobile plate is the fatigue parameter of the material, and the quality of the fatigue performance of the material influences the simulation analysis result. In addition, for automobile plate producers, direction is provided for material optimization by judging the quality of material fatigue performance under different processes, so comparative analysis of material fatigue performance is also necessary.
According to the automobile simulation requirements, the fatigue strength, namely the service life of the material under constant-amplitude strain, of a general automobile plate material is described by an E-N curve. For materials with larger difference of fatigue performance, the judgment can be carried out according to the height of the curve. However, for materials with fatigue properties that are not very different, considering experimental errors, how to judge whether the difference of the fatigue properties is the difference of the materials or fluctuation caused by the experimental errors, there is no relevant comparative analysis at present.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for contrastively analyzing fatigue curves of automobile plates, which can judge whether two E-N curves have difference or not by analyzing errors between experimental data and the E-N curves (fitting curves) and differences between the E-N curves (fitting curves) of materials, thereby judging the quality of the fatigue performance.
The technical scheme for solving the technical problems is as follows:
a comparative analysis method for fatigue curves of automobile plates comprises the following steps:
(1) according to the same technical condition, carrying out life detection on two materials with different strain amplitudes to obtain 18 strain amplitudes in total;
(2) fitting the original experimental data to obtain an E-N curve, wherein the fitting formula is
In which
Fatigue strengthThe coefficient, 2Nf is the fatigue reversal frequency, b is the fatigue strength index,
is fatigue ductility coefficient, c is fatigue ductility index, E is elastic modulus;
(3) analyzing the fitting difference value of the experimental data and the E-N curve, and averaging the two data;
(4) performing comparative analysis on the two E-N curves to determine a difference value;
(5) determining whether the absolute value of the difference is less than the average of the fitted differences of the two sets of data in step (3): if the two curves are smaller than the preset value, the two curves are consistent; otherwise the two curves differ.
In the comparative analysis method for the fatigue curve of the automobile sheet, the fitting difference between the calculated experimental data in the step (3) and the E-N curve is defined as: fit difference = | (experimental data-fit data) |/fit data.
According to the comparative analysis method for the fatigue curve of the automobile plate, the fatigue lives of the two materials under the same total strain amplitude are determined in the step (4), and the difference value of the lives of the two materials under different strain amplitudes is calculated, wherein the calculation formula is as follows: (2 Nf of material # 1-2 Nf of material # 2)/2 Nf of material # 2.
The invention has the beneficial effects that:
the invention is the first creation of the automobile sheet fatigue curve comparison analysis method and fills the blank of automobile sheet material analysis. The invention determines the difference of the E-N curve between the two materials by analyzing the error between the experimental data and the E-N curve (fitting curve), thereby judging the quality of the fatigue performance, providing technical support for material optimization and simultaneously providing data support for fatigue simulation calculation of an automobile factory.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
The embodiment is as follows: comparative analysis of fatigue curves for both materials.
(1) Two materials to be compared are selected, namely an IF steel material 1# and an IF steel material 2 #. According to the same technical condition, the low cycle fatigue test adopted in the example adopts axial strain control, the strain cycle ratio R = -1, the service life detection of different strain amplitudes is carried out on two materials, 18 groups of data of strain amplitude-service life are obtained, and the data are shown in the table 1:
TABLE 1 IF steels 1# and 2# samples
(2) Fitting the original experimental data to obtain an E-N curve, wherein the fitting formula is
Wherein
2Nf is the fatigue strength coefficient, b is the fatigue strength index,
the fatigue ductility coefficient, c the fatigue ductility index, and E the modulus of elasticity. The parameters of the fit are as follows:
TABLE 2 fatigue parameters obtained by fitting
(3) And calculating a fitting difference value of the experimental data and the E-N curve to obtain the fitting difference value, wherein the fitting difference value is defined as = | (experimental data-fitting data) |/fitting data. The two sets of data were averaged to give an average of 31.15% of the fitted difference.
TABLE 3 fitting Difference
(4) Comparison of the fatigue life under the same strain amplitude, the fatigue life of the IF steel sample No. 1 and the fatigue life of the IF steel sample No. 2 under the same total strain amplitude are calculated and shown in Table 4. And calculating the difference value of the service life of the IF steel sample No. 1 and the service life of the IF steel sample No. 2 under different strain amplitudes, wherein the calculation formula is as follows: (1#2 Nf-2 #2 Nf)/2 #2Nf, with a lifetime variation of-2% to 20% on the order of 103 to 107.
TABLE 4 2Nf at the same strain amplitude
(5) And comparing the life deviation with the fitting difference, and if the absolute value of the life deviation is smaller than the average value of the fitting difference, determining that the two curves are basically consistent.
The mean value of the fitting difference obtained from (3) was 31.15%, and the life deviation calculated from (4) was-2% to 20%, so that the two curves can be considered to be substantially identical within the fitting error range.
Claims (1)
1. A comparative analysis method for fatigue curves of automobile plates is characterized in that: the method comprises the following steps:
(1) according to the same technical condition, carrying out life detection on two materials with different strain amplitudes to respectively obtain 18 strain amplitudes;
(2) fitting the original experimental data to obtain an E-N curve fitting formula of
Wherein
2Nf is the fatigue strength coefficient, b is the fatigue strength index,
is fatigue ductility coefficient, c is fatigue ductility index, E is elastic modulus;
(3) analyzing the fitting difference value of the experimental data and the E-N curve, wherein the fitting difference value is defined as: the fitting difference value = | (experimental data-fitting data) |/fitting data, the fitting difference values are respectively calculated for 18 strain amplitudes of each material, the 18 fitting difference values of each material are averaged to obtain a fitting difference value average value, and then the fitting difference value average values of the two materials are subjected to averaging data;
(4) calculating the fatigue life of the two materials under the same total strain amplitude, determining a difference value, and calculating the life difference value of the two materials under different total strain amplitudes according to the following calculation formula: (2 Nf of material # 1-2 Nf of material # 2)/2 Nf of material # 2;
(5) determining whether the absolute value of the difference value of the lives of the two materials in the step (4) is smaller than the average data of the average value of the fitting difference values of the two materials in the step (3), and if so, determining that the two curves are consistent; otherwise the two curves differ.
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| US20050273277A1 (en) * | 2004-01-14 | 2005-12-08 | University Of Tennessee Research Foundation, Inc. | Vehicle fatigue life and durability monitoring system and methodology |
| US20120271566A1 (en) * | 2011-04-21 | 2012-10-25 | Vinayak Deshmukh | Method for the prediction of fatigue life for structures |
| US9733201B2 (en) * | 2013-11-15 | 2017-08-15 | Pentair Thermal Management Llc | Thermal age tracking system and method |
| CN104156500A (en) * | 2014-07-10 | 2014-11-19 | 东北大学 | Method for predicting material fatigue life |
| CN107305174B (en) * | 2016-04-20 | 2020-12-11 | 中国特种设备检测研究院 | A Numerical Characterization Method and System for Material Stress-Strain Constitutive Relation |
| CN109308393B (en) * | 2018-09-30 | 2021-04-23 | 中车齐齐哈尔车辆有限公司 | Method and system for evaluating fatigue life of vehicle body |
| CN110530746B (en) * | 2019-09-18 | 2022-04-29 | 武汉钢铁有限公司 | Method for testing high-low cycle fatigue full-strain-life curve of metal material |
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