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GB/T 37616-2019: Aluminium alloys extruded profiles-axial force controlled fatigue testing method
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Aluminium alloys extruded profiles-axial force controlled fatigue testing method
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GB/T 37616-2019
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Basic data | Standard ID | GB/T 37616-2019 (GB/T37616-2019) | | Description (Translated English) | Aluminium alloys extruded profiles-axial force controlled fatigue testing method | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | H61 | | Classification of International Standard | 77.150.10 | | Word Count Estimation | 22,241 | | Date of Issue | 2019-06-04 | | Date of Implementation | 2020-05-01 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 37616-2019: Aluminium alloys extruded profiles-axial force controlled fatigue testing method---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Aluminium alloys extruded profiles-axial force controlled fatigue testing method
ICS 77.150.10
H61
National Standards of People's Republic of China
Aluminum alloy extruded profile axial force
Control fatigue test method
Published on.2019-06-04
2020-05-01 implementation
State market supervision and administration
China National Standardization Administration issued
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by the China Nonferrous Metals Industry Association.
This standard is under the jurisdiction of the National Nonferrous Metals Standardization Technical Committee (SAC/TC243).
This standard was drafted. Liaoning Zhongwang Group Co., Ltd., Nonferrous Metals Technology and Economic Research Institute, Guohe General Test Evaluation and Certification Shares
Company, China Aviation Shenfei Civil Aircraft Co., Ltd., Guangdong Industrial Analysis and Testing Center, Shannan Nanshan Aluminum Co., Ltd., Northeast Light
Alloy Co., Ltd., Southwest Aluminum (Group) Co., Ltd., Shandong Yankuang Light Alloy Co., Ltd., Guangdong Gaodeng Aluminum Co., Ltd.
CZ Zhuzhou Electric Locomotive Co., Ltd., CRRC Tangshan Locomotive & Rolling Stock Co., Ltd., CRRC Qingdao Sifang Locomotive & Rolling Stock Co., Ltd., Guangdong
Jianmei Aluminum Profile Factory (Group) Co., Ltd.
The main drafters of this standard. Sun Wei, Xi Huan, Wu Lei, Liu Zuoyu, Shi Changliang, Li Cast Iron, Wang Jinhua, Xiao Hong, Liu Bo, He Jiajin, Yue Yixin,
He Tian, Lin Huaqiang, Xu Shiguang, Jia Dazhao.
Aluminum alloy extruded profile axial force
Control fatigue test method
1 Scope
This standard specifies aluminum alloy extruded profiles at room temperature (10 ° C ~ 35 ° C) (no stress concentration introduced) by axial equal amplitude force control fatigue
Test method.
This standard is applicable to the determination of fatigue life under the specified stress level of aluminum alloy extruded profiles, and specifies the fatigue strength under the condition of cycle number.
Determination of SN curve, PSN curve and Goodman curve.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article.
Pieces. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 10623 Metallic material mechanical properties test terminology
JJG556 axial afterburning fatigue testing machine
3 Terms and definitions
The following terms and definitions as defined in GB/T 10623 apply to this document.
3.1
Survivability probabilityofsurvival
The probability that the fatigue life or fatigue strength exceeds the specified value is expressed as a percentage.
3.2
Median fatigue life medianfatiguelife
N50
Fatigue life with 50% survival.
3.3
Fatigue lifeforPsurvival
NP
The fatigue life of the base material survival rate P at or above the specified stress level.
Note. Survival rate P generally takes 97.5%, 95%, 90%, etc.
3.4
Median logarithmic fatigue life medianlogarithmfatiguelife
X50 (or lgN50)
Log fatigue life with 50% survival.
3.5
Logarithmic fatigue life with a specified survival rate logarithmfatiguelifeforPsurvival
xP (or lgNP)
The logarithmic fatigue life at which the parent metal survival rate P can reach or exceed at a specified stress level.
3.6
Fatigue strength for survival rate fatiguetengforforsursural
σP
When a certain fatigue life N is specified, the base material survival rate P can reach or exceed the fatigue strength.
3.7
Median fatigue strength medianfatiguestrength
Σ50
Fatigue strength with 50% survival.
3.8
Median SN curve medianS-Ncurve
A curve obtained by fitting the median fatigue life at each stress level and fitting the median fatigue strength at each specified life, ie
Stress-life relationship curve for 50% survival.
3.9
PSN curve PS-Ncurve
Fit the fatigue life of the P-survival rate at each stress level and fit the fatigue strength of the P-survival rate at each specified life
The resulting curve, the stress-life curve of P survival rate.
3.10
Goodman curve Goodmancurve
Under the specified fatigue life conditions (for example. specified fatigue life Nf = 1 × 107), by at least three different stress ratios R (for example. R =
The fatigue stress level parameters of -1, 0.1, and 0.5), that is, the relationship between the maximum stress, the minimum stress, the stress amplitude, and the average stress.
4 Method Overview
The method is to apply a constant amplitude alternating load along the longitudinal direction of the sample (see Figure 1). The cyclic stress type is shown in Figure 2. Prescribed stress level
Under the conditions, the fatigue life of the material is measured; and the fatigue strength of the material is measured under the condition of a predetermined number of cycles.
Description.
1---upper fixture;
2---sample;
3--- Lower fixture.
Figure 1 Schematic diagram of fatigue test
Description.
Σa --- stress amplitude;
Σm --- average stress;
Pressure---σmax≤0, σmin< 0;
Pulling pressure---σmax>0, σmin< 0;
Lara---σmax >0, σmin≥0.
Figure 2 cyclic stress type
5 test equipment
5.1 Fatigue testing machine. Electromagnetic resonance fatigue testing machine, electro-hydraulic servo fatigue testing machine or other forms of axial fatigue testing machine.
5.2 The fatigue tester shall meet the requirements of JJG556.
6 sample
6.1 Sample classification
The shape of the sample varies according to the shape and size of the cross section of the working part, and can be divided into a circular single-section sample, a circular cross-section sample, and a rectangular shape.
Single-section specimens and rectangular cross-section specimens. The circular sample is divided into a cylindrical sample and a threaded sample according to the type of the clamping end. Notched specimen
The shape and size are indicated on the order form (or contract) after agreement between the supplier and the buyer.
6.2 Sample shape and size
6.2.1 Round sample
6.2.1.1 Round single section specimen
The shape of the circular single-section specimen is shown in Figure 3. The dimensions and deviations are in accordance with Table 1.
Description.
R1 --- sample arc radius;
D1 --- the smallest diameter of the sample;
D(M)---sample clamping part diameter or thread size;
L1 --- clamping part;
L --- Total length of the sample.
Figure 3 Schematic diagram of a circular single-section sample
Table 1 Round single-section sample size and deviation unit is mm
Profile thickness a sample type
Minimum diameter of sample
D1
Sample arc radius
R1
Sample holding part diameter or snail
Grain specification D (M)
>15.00~25.00
Thread sample
Cylindrical sample
5.00±0.02 50.00±1.00
M14×1
12.00±1.00
>25.00
Thread sample
Cylindrical sample
10.00±0.02 80.00±1.00
M22×1
20.00±1.00
6.2.1.2 Round equal section specimen
The shape of the circular cross-section sample is shown in Figure 4. The dimensions and deviations are in accordance with Table 2.
Description.
R2 --- sample transition arc radius;
D2 --- sample cross-sectional diameter;
D(M)---sample clamping part diameter or thread size;
L1 --- clamping part;
Lc --- parallel length of the working part of the sample;
L --- Total length of the sample.
Figure 4 Schematic diagram of a circular cross-section sample
Table 2 The dimensions and deviation units of the circular equal section specimen are in millimeters
Profile thickness a sample type
Specimen cross-sectional diameter
D2
Sample transition arc radius
R2
Specimen working part
Parallel length Lc
Sample holding part diameter or
Thread size D (M)
≥25.00
Thread sample
Cylindrical sample
10.00±0.05 60.00±1.00 35.00±1.00
M22×1
20.00±1.00
6.2.1.3 Allowable deviation
For circular cross-section specimens, the allowable deviation of coaxiality and parallelism is not more than 0.05mm, and the perpendicularity between the end faces of the threaded specimen and the axis
The allowable deviation is not more than 0.05mm.
6.2.2 Rectangular specimen
6.2.2.1 Rectangular single section specimen
The shape of the rectangular single-section specimen is shown in Figure 5. The dimensions and deviations are in accordance with Table 3. If there are special requirements, the supply and demand double
After the party has agreed, please indicate it in the order form (or contract).
Description.
R1---sample arc radius;
a --- sample thickness;
B1 --- the minimum width of the sample;
B --- sample clamping part width;
L1---clamping part;
L --- Total length of the sample.
Figure 5 Schematic diagram of a rectangular single-section sample
Table 3 Rectangular single-section specimen size and deviation unit is mm
Profile thickness a Sample minimum width b1 Sample arc radius R1 Sample clamping portion width B
≤15.00 15.00±0.05 120.00±1.00 40.00±1.00
6.2.2.2 Rectangular equal section specimen
The shape of the rectangular cross-section sample is shown in Figure 6. The dimensions and deviations should be in accordance with Table 4. If there are special requirements, the supply and demand double
After the party has agreed, please indicate it in the order form (or contract).
Description.
R2---sample transition arc radius;
a --- sample thickness;
B2 --- sample cross section width;
B --- sample clamping part width;
L1---clamping part;
Lc---the parallel length of the working part of the sample;
L --- Total length of the sample.
Figure 6 Schematic diagram of a rectangular equal-section sample
Table 4 Rectangular equal section sample size and deviation unit is mm
Profile thickness a Specimen cross-sectional width b2 Specimen transition arc radius R2 Parallel length Lc of specimen working part Width of specimen clamping part B
≤15.00 15.00±0.05 50.00±1.00 50.00±1.00 40.00±1.00
6.2.2.3 Allowable deviation
The allowable deviation of the parallelism of the parallel portion of the sample is not more than 0.15 mm, and the allowable deviation of the coaxiality of the clamping portions at both ends is not more than 0.40 mm.
6.3 Sample preparation
6.3.1 General requirements
6.3.1.1 The sampling position and direction shall comply with the requirements of relevant standards or agreements. If the sampling position and direction are not specified, it may be as specified in 6.3.2.
Sampling with 6.3.3 and numbering and marking the samples.
6.3.1.2 The processing dimensions, shape tolerances and surface roughness of the specimen shall meet the requirements, and the arc and parallel length shall be smoothly connected. Single cross section test
Sample size and shape tolerances should be verified and measured using a tool microscope.
6.3.1.3 During turning and milling, the depth of cut shall be reduced successively and sufficient cutting fluid shall be provided to reduce work hardening and prevent overheating.
6.3.1.4 When the sample is polished, it shall be polished along the longitudinal direction of the sample, and the force pressed against the surface of the sample shall be as small as possible to reduce the influence of surface residual stress.
6.3.1.5 The surface of the specimen shall be free from scratches, bumps and corrosion.
6.3.2 Round specimen
6.3.2.1 When the wall thickness of the profile is greater than 15.00mm and not more than 40.00mm, a circular specimen is cut at the center of the profile wall thickness; the profile wall
When the thickness is greater than 40.00 mm, a circular sample having a diameter of d 5.00 mm is cut from the center of the wall thickness of the profile to the position 1/2 of the surface.
6.3.2.2 After the round sample is roughed, the diameter of the sample is d 0.50mm. It is recommended to cut through 3 times, each cutting depth is
1.25mm, 0.75mm, 0.25mm.
6.3.2.3 After the roughing of the sample is finished, the diameter of the sample is d 0.02mm. It is recommended to cut through 3 times.
The degree is 0.12 mm, 0.07 mm, and 0.05 mm.
6.3.2.4 Polish the finished sample in a direction approximately perpendicular to the axis of the sample, and finally reach the nominal size of the sample, except for the sample holding end
Further, the surface roughness Ra is not more than 0.32 μm.
6.3.3 Rectangular specimen
6.3.3.1 When the wall thickness of the profile is not more than 15.00mm, cut the rectangular specimen with full wall thickness.
6.3.3.2 Rectangular cross-section The surface of the specimen is generally not required to be machined. The side is generally longitudinally milled. It is recommended that after 3 passes, each
The secondary milling depth is 0.50 mm, 0.20 mm, 0.10 mm.
6.3.3.3 Polish the milled specimen longitudinally until it reaches the nominal size. The side surface roughness Ra is not higher than 0.32 μm except for the sample holding end.
6.3.3.4 In order to avoid the occurrence of fatigue cracks on the edges, the edge of the working part of the specimen should have a reverse radius of 0.10 mm along the axial direction.
A rounded corner of 0.20 mm and a roughness of no more than 0.32 μm.
7 Test instructions
7.1 Before the test, the sample shall be visually inspected. When the surface of the sample is cleaned, the sample shall not be damaged.
Surface defects, cracks, chisels, nicks, circumferential scratches, unfused and corroded defects are not permitted.
7.2 Use a tool microscope to measure the width or diameter of the smallest cross section of a single-section specimen, measure the thickness of the specimen with a micrometer, and measure the fine
The degree should be no less than 0.01mm.
7.3 The clamping specimen shall be such that the load applied to the specimen is axial.
7.4 The applied load shall be smooth and shall not be overloaded. The load should be kept stable during the sample process.
7.5 The test selection frequency range is generally not more than.200 Hz.
7.6 The specimen shall be tested under the specified stress until the specimen is broken or tested to the specified number of cycles.
7.7 The sample fracture occurs in the non-working part and the test result is invalid.
7.8 Record test results and abnormalities during the test.
8 Test methods and data processing
8.1 Passability test
8.1.1 Overview of test methods
Passivity test is used for random sampling test of product production process control.
8.1.2 Number of samples
Prepare at least 3 samples for each inspection lot.
8.1.3 Test conditions
The test conditions are generally the specified stress level, the stress ratio R, the specified number of cycles, and the test frequency range. Stress level, stress ratio, and
The number of cycles is determined by the test conditions specified by the technical standards and technical agreements.
8.1.4 Evaluation of test results
Under the specified test conditions, if all the fatigue samples of the same inspection batch have reached the specified number of cycles without breaking, the test knot
If the sample is broken or broken in the non-working part, the test result is unqualified.
8.2 Determination of fatigue life
8.2.1 Overview of test methods
The group test method was used to determine the median fatigue life at a certain stress level in the middle life zone and the fatigue life of the specified survival rate.
8.2.2 Number of samples
A set of samples of at least 3 pieces. The number of samples that need to be repeated for each level of stress depends on the degree of dispersion of the test data and should meet the requirements.
The confidence level sought.
8.2.3 Determination of median fatigue life
The fatigue life of a set of samples was measured at the same stress level. When the confidence level γ is required, it should be based on the variation system during the test.
For the number CV=s/x and the given confidence γ, refer to Table A.1 of Appendix A to determine the minimum number of observations required. When testing data processing, first
Each fatigue life is taken as a logarithmic fatigue life xi = lgNi, and then calculated.
Subsample mean x.
x=
N∑
i=1
Xi (1)
Subsample standard deviation s.
s=
i=1
(xi-x)2
N-1
(2)
Median fatigue life N50.
N50=lg-1x (3)
8.2.4 Determination of the fatigue life of the specified survival rate
Specifies the logarithmic fatigue life xP of the survival rate P.
xP = x ± uPs (4)
In the formula, the standard normal offset uP value corresponding to the survival rate P refers to Table A.2. According to the characteristics of uP, when P≥50%, take a negative value.
A positive value is obtained when P < 50%.
The fatigue life NP of the prescribed survival rate P.
NP = lg-1xP (5)
Note. If the user or product technical conditions require sample standard deviation correction or unilateral tolerance coefficient correction, or fatigue test factor F method for fatigue assessment
For the life, refer to Appendix B, Appendix C and Appendix D for data processing.
8.3 Determination of fatigue strength
8.3.1 Overview of test methods
The median fatigue strength at a predetermined number of cycles in the long-life zone and the fatigue strength of the prescribed survival rate were measured by the lift test method.
8.3.2 Number of samples
Generally, about 15 pieces of effective samples are required. The number of samples required for each level of stress depends on the degree of dispersion of the test data.
The required confidence γ is satisfied.
8.3.3 Determination of median fatigue strength
The stress increment Δσ=σi 1-σi of the two adjacent stress levels of the lifting test method shall be the expected fatigue limit or median fatigue strength.
3% to 5%. The level of stress level depends on the magnitude of the stress increment and the degree of dispersion of the test data, and is generally 3 to 5 grades. The first thing
The test stress level of the sample should be slightly higher than the expected fatigue limit or median fatigue strength, and then the test stress level of the sample depends on the previous test.
Sample test results. Where the previous sample does not reach the specified number of cycles, the subsequent test will be at a lower level of stress.
Under the next test; if the previous sample reaches the specified number of cycles without destruction, the subsequent test is carried out at a high level of stress level until the end
Until all tests are completed. The test data before the first occurrence of the opposite result can be used once in subsequent tests.
Median fatigue strength σ50.
Σ50=
N∑
i=1
Viσi (6)
In the formula.
n --- the total number of effective trials;
m --- stress series;
Σi --- the i-th stress level;
Vi --- Number of tests for the i-th stress level.
If the test requires the determination of the median fatigue strength and standard deviation, the data points of adjacent stress levels should be plotted as a break point (×) and
An unbreaking point (○) is paired. If the lifting diagram is closed, all test points can be paired, and the median fatigue strength
The estimated amount is calculated according to equation (7), and the results calculated by equations (7) and (6) are the same.
Median fatigue strength σ50.
Σ50=
n*∑
m*
i=1
V*iσ*i (7)
In the formula.
n*---the total number of pairs, that is, half of the number of samples n;
m*---the number of pairs of pairs, that is, the number of stress levels m minus 1, ie m*=m-1;
Σi*---the stress level of the pair (σi σi 1)/2;
Vi*---the number of pairs of adjacent two levels.
Standard deviation.
s* =
m*
i=1
[V*i (σ*i -σ50)2]
n* -1
(8)
When the confidence level γ is required, it should be based on the coefficient of variation CV=s/x=s/σ50 and the given confidence level γ during the test, refer to Table A.1.
And Table A.2, determine the minimum number of observations required.
8.3.4 Determination of the fatigue strength of the specified survival rate
Specify the fatigue strength of the survival rate P.
σP = σ50 uPs* (9)
In the formula, the standard normal offset uP values are shown in Table A.2.
Note. If the user or product agreement requires sample standard deviation correction or one-sided tolerance coefficient correction, please refer to Appendix B or Appendix C for data processing.
8.4 SN curve determination
8.4.1 Determination of single point SN curve
When the number of specimens or test conditions is limited, the SN curve can be roughly determined by a single point method. The number of samples is about 10 pieces.
In the medium life zone, the stress level should not be less than 5. When the fatigue limit σN is measured, if the sample is at the i-th stress σi, the specified value is not reached.
The number of cycles is broken, and no fracture occurs at the lower i-th grade stress σi 1 , and the two-stage stress difference (σi-σi 1) does not exceed
For 5% of σi 1, the average of σi and σi 1 can be the fatigue limit reference value, ie.
σN =
(σi σi 1) (10)
8.4.2 Determination of SN curve and PSN curve
8.4.2.1 Medium life zone segment
In the middle life section, the stress level of 3~5 grades is selected, and the median fatigue life and the fatigue life under the specified survival rate are determined by a group test.
8.4.2.2 Long life section line segment
Long-life zone segment, under the specified number of cycles N (for example. N = 1 × 107), using the lifting method test to determine the median fatigue strength and gauge
The fatigue strength of the survival rate; if necessary, the lifting test can also be carried out under the specified number of cycles N (for example. N=5×106).
The method measures the fatigue strength of the median fatigue strength and the specified survival rate.
8.4.2.3 SN curve and PSN curve fitting
In semi-logarithmic coordinates, the stress σ is plotted on the ordinate, and the number of cycles N is plotted on the abscissa (logarithmic lgN) to plot the SN curve and P-
SN curve. In the medium life zone, the SN curve and PSN curve fitting expressions are as shown in equations (11) and (12).
lgN50=a blgσmax (11)
lgNP = a blgσP (12)
In the formula, a and b are undetermined coefficients, which are obtained by the least squares method.
8.5 Goodman curve determination
The Goodman curve (or equal life-stress curve) is plotted against the 8.3 and 8.4 measurement data or the specified stress level indicators.
Under the specified number of cycles (for example. N = 1 × 107), by at least three different stress ratios R (for example. R = -1, 0.1, 0.5), and most
The Goodman curve is plotted for the large stress σmax, the minimum stress σmin, the stress amplitude σa, and the average stress σm. Goodman curve fitting expression
The binary one-order equation (13) is as follows.
Σmax=(Aσm C)
Σmin=(Bσm-C){ (13)
Where A, B and C are undetermined coefficients, which are obtained by least squares method.
The fatigue properties of engineering materials should meet the requirements of formula (14).
Σmax≥ (Aσm C)
Σmin≤ (Bσm-C){ (14)
9 numerical repair
9.1 Force (unit. N) and stress (unit. MPa) are rounded to single digits.
9.2 The sample size is trimmed to 0.01mm.
9.3 The test frequency is rounded to a single digit.
9.4 Fatigue life or number of cycles is expressed in 10n form, retaining three significant digits, for example. 3.56 × 105.
10 test report
The test report should include the following.
a) the standard number;
b) profile alloy grade, status, model and lot number;
c) sample type, size, sampling direction and sampling position;
d) Test conditions, including. fatigue tester model, loading method, stress level, stress ratio, test frequency, test waveform and test temperature
Degree
e) end of test criteria, number of cycles (N = 1 × 107), or sample failure, or other criteria;
f) test results, including. test analysis data, which may include expressions and relationship curve graphs;
g) the tester, the date of the test and the test unit;
h) Abnormal conditions during the test.
Appendix A
(informative appendix)
Numerical table
Tables A.1 to A.5 give the relevant value tables.
Table A.1 specifies the minimum number of samples when the confidence γ is specified (P=50%, relative error δ=±5%)
Coefficient of variation CV=
x
Less than
γ=95% γ=90%
Minimum number of samples
0.0201 0.0297 3
0.0314 0.0425 4
0.0403 0.0524 5
0.0476 0.0608 6
0.0541 0.0681 7
0.0598 0.0746 8
0.0650 0.0806 9
0.0699 0.0863 10
0.0744 0.0915 11
0.0787 0.0964 12
0.0828 0.1012 13
0.0866 0.1056 14
0.0903 0.1099 15
0.0938 0.1141 16
0.0972 0.1181 17
0.1005 0.1219 18
0.1037 0.1257 19
0.1068 0.1293 20
Table A.2 P value table
uP 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09
0.0 0.5000 0.5040 0.5089 0.5120 0.5160 0.5199 0.5239 0.5279 0.5319 0.5359
0.1 0.5398 0.5438 0.5478 0.5517 0.5557 0.5596 0.5636 0.5675 0.5714 0.5753
0.2 0.5793 0.5832 0.5871 0.5910 0.5948 0.5987 0.6026 0.6064 0.6103 0.61...
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