Some standard content:
National Standard of the People's Republic of China
Metals--Rotating bar bending fatigue testingUDC 669 : 620.174
GB 4337-—84
This standard is applicable to the determination of fatigue properties of metal circular cross-section specimens subjected to bending moment under rotating state under air conditions of 15-35℃.
Test principle
The specimen rotates and bears a bending moment. The force F that produces the bending moment is constant and does not rotate. The specimen can be installed as a cantilever and force is applied at one or two points, or installed as a beam and force is applied at four points. The test is carried out until the specimen fails or exceeds the predetermined number of stress cycles. Note: Failure means that the specimen has visible fatigue cracks or complete fracture. In special applications, the plastic deformation or crack growth rate of the specimen can be used to determine the termination of the test.
2 Terms and definitions
Fatigue - When a material is subjected to alternating stress or strain, local cumulative damage occurs and the material fails after a certain number of cycles. Fatigue life, N - the number of cycles that a material undergoes before failure under a specified stress or strain. 2.2
SN curve -
- a graph showing the relationship between stress and fatigue life. Stress ratio, R - the ratio of minimum stress to maximum stress, i.e. αmin/αmax (see Figure 1). 2.4
Stress cycles
Figure 1 Symmetrical stress cycle
2.5 Conditional fatigue limit, RN))
- the median fatigue strength corresponding to a specified number of cycles. Fatigue limit, - the median fatigue strength when N is infinite (for steel materials, N = 1×10° times is generally taken). 2.6 Theoretical stress concentration factor, Kt-
--the ratio of the maximum stress in the stress concentration area calculated according to the elastic theory to the nominal stress in the area. Survival rate, P-
the percentage of fatigue life above the specified value. 2.7
3 Test specimen
3.1 The symbols and instructions related to the test specimen are shown in the following table: Issued by the National Bureau of Standards on April 9, 1984
Implemented on March 1, 1985
3.2 Test specimen shape
GB 4337-84
Diameter of the clamping part or the force-applying part
Diameter at the maximum stress
Radius of the connecting arc between the clamping part and the test part of a cylindrical test specimen or between the clamping parts of a funnel-shaped test specimen The test specimen shape is shown in Figures 2 to 8, which can be cylindrical, conical and funnel-shaped, and its test cross section is circular. The shape of the single
test part should be designed according to the force-adding method of the testing machine used, and the shape of the clamping part should be designed according to the clamping method of the testing machine used. The bending moment M diagram and the nominal stress S diagram of the specimen under various conditions are shown in Figures 2 to 8. AN
Cylindrical specimen-
--single point force
Figure 3 Conical specimen---single point force
GB4337--84
Figure 4 Funnel-shaped specimen---single point force
Figure 5 Cylindrical specimen---two point force
GB4337--84
Figure 6 Cylindrical specimen four point force
Figure 7 "Funnel-shaped specimen
one or two point force| |tt||GB4337-84
Figure 8 Funnel-shaped specimen - four-point force
The ratio of the cross-sectional area of the clamping part to the cross-sectional area of the test part should be greater than 1.5. If it is a threaded clamp, this ratio should not be less than 3. Where possible, the above ratio should be larger. Note: The combined effect of high stress and high test speed may cause overheating of the specimen of some metal materials during testing. When the stress is specified, it can be achieved by using a smaller specimen diameter or using a funnel-shaped The specimen is cooled to reduce heat. If the specimen is cooled, the cooling medium used shall not cause rust on the specimen surface.
3.3 Specimen size
The specimens used in the same batch of fatigue tests shall have the same diameter d, with a deviation of ±IT10. The measurement accuracy of the actual minimum diameter of the specimen shall not be less than 0.01mm. When measuring the diameter, do not damage the surface of the specimen. The coaxiality tolerance between the test part and the clamping part shall not be greater than 0.01mm. Smooth cylindrical standard specimens with the shape and size shown in Figure 9 are recommended. The diameter d is 6, 7.5, and 9.5mm. The deviation of d is ±0.05mm; the distance L between the clamping ends is 40mm.
Note: When studying the notch sensitivity of the material, the notched specimen with the shape and size shown in Figure 10 can be used as a reference. 40.01
Figure 9 Smooth cylindrical specimen (K:=1)
3.4 Specimen preparation
3.4.1 Sampling
GB 4337-84
0 0.75 ±
Figure 10 Annular semicircular notch specimen (0 is the notch radius, K: =1.86) The sampling location, orientation and method shall comply with relevant standards or mutual agreement. 3.4.2 Mechanical processing
The residual stress and work hardening produced by the mechanical processing on the specimen surface shall be as small as possible, and the surface quality obtained shall be as uniform as possible. Grinding is used for finishing of harder metal specimens. Sufficient coolant shall be provided during grinding to ensure that the specimen surface is not overheated. When heat treatment is performed before finishing of the specimen, deformation or surface layer change shall be prevented. Quality. Straightening of the specimen is not allowed. 3.4.3 Surface finishing
For the final finishing of the specimen surface, it is recommended to use water-abrasive sandpaper or emery cloth to mechanically polish the specimen longitudinally. After surface finishing, the surface finish of the smooth specimen test part should strive to reach 10. Note: ① If the test purpose is to evaluate a specific surface condition or the fatigue performance of the known material is not sensitive to surface quality, the preparation of the specimen is not restricted by 3.4.2 and 3.4.3.
② For the processing technology of the specimen, see Appendix A (reference). 3.5 Specimen storage
If the prepared specimen needs to be stored for a period of time before testing, it should be properly protected and stored to ensure that it does not deform during storage and the surface is intact. Before the test, the specimen should be checked by appropriate methods. If there is rust or scratches on the surface, it should be re-finished to eliminate it. 4 Testing machine
Different types of rotary bending fatigue testing machines can be used, but the following requirements should be met: 4.1 The error of the applied bending moment is not greater than ±1%.
4.2 Install the test rod on the test machine, slowly rotate the main shaft of the test machine, and use a dial indicator to measure the radial runout along the test part of the test rod or along its free end. The radial runout measured at the force-applying part of the main shaft barrel is less than 0.06mm when the standard specimen is installed and running without load.
4.3 The initial bending moment should be as small as possible. For pure bending fatigue testing machines with a maximum bending moment greater than 3kgf·m (29.4N·m), the initial bending moment is not greater than 10% of the maximum bending moment. For pure bending fatigue testing machines with a maximum bending moment less than 3kgf·m (29.4N·m), the initial bending moment is not greater than 5% of the maximum bending moment.
4.4 The test speed range is 900~10000rpm, and can be adjusted in stages or continuously. 5 Test procedure
5.1 Install the specimen
Install the specimen into the testing machine, clamp it firmly, and keep it coaxial with the main shaft of the testing machine. When the main shaft of the testing machine is slowly turned by hand, the radial runout measured by the dial indicator on the main shaft of the pure bending test machine or on the free end of the specimen in the cantilever bending test machine should not be greater than 0.03mm. After starting the testing machine, when running normally without load, the radial runout measured at the force-applying part of the main shaft barrel should not be greater than 0.06mm. Before applying force, the above values must be verified to meet the requirements. Avoid touching the surface of the test part of the specimen when loading the sample. 5.2 Obtain the test speed
Start the testing machine and make the test speed reach the specified value. The recommended test speed range is 900~10000rpm. The test speed of the same batch of tests should be the same. The test speed that causes resonance of the specimen shall not be used.
5.3 Add force
Add force to the specified value in an incremental or continuous manner, smoothly and without impact. 5.4 Termination of test
The test is terminated until the specimen fails or the specified number of cycles is reached. In principle, the test shall not be interrupted. If the specimen fails outside the maximum stress position, or there are obvious defects on the fracture, or abnormal data is generated by stopping the test midway, the test results will be invalid.
5.5 Determination of conditional fatigue limit
The conditional fatigue limit is determined by the lifting and lowering method. The number of valid specimens is generally more than thirteen. The stress increment is generally 3-5% of the expected conditional fatigue limit. The test is generally carried out at stress levels of 3-5. The stress level of the first specimen should be slightly higher than the expected conditional fatigue limit. According to the test results of the previous specimen (destruction or passing), the stress of the next specimen is determined (reduced or increased) until all tests are completed. The data before the first pair of opposite results, if within the stress fluctuation range of the subsequent data, shall be used as valid data. During the test, they should be gradually translated to after the first pair of opposite results as the first valid data at the stress level of the specimen.
The conditional fatigue limit is calculated as follows:
Or(N)=m
2U; 0; kgf /mm\(N/mm2)
Where: m---the total number of effective tests (including failure or passing data); n---the number of test stress levels:
Ui--the number of tests at the i-th stress level (i=1, 2, n). 5.6 Determination of SN curve
When determining the S-N curve, usually at least 4 to 5 stress levels are taken. The conditional fatigue limit measured by the lifting method is used as the low stress level point of the SN curve. For other tests at higher stress levels of 3 to 4, the group test method is used. The number of specimens in each group depends on the dispersion of the test data and the required confidence level, and generally increases gradually with the decrease of the stress level. Usually, a group requires about five specimens.
The S·N curve measured by the above method is considered to have a survival rate of 50%. 6 Methods of expressing test results
The test results are expressed in the following two ways
6.1 Tabular method
The table should include the following contents:
Test sequence, specimen number, specimen shape, size and surface finish, test stress, number of cycles experienced, average fatigue life measured by the group method or conditional fatigue limit measured by the lift method. 6.2 Graphical method
SN curve diagram is a commonly used method to illustrate fatigue test results. The drawing method is as follows: 248
GB 4337--84
Rotational bending fatigue test, 40Cr, b=1176N/mm cylindrical specimen, d=7.5mm, ground surface V9 test speed is 3000rpm, test in air at room temperature Lifting method test to failure
Lifting test to pass
58kgf/mm
2/568N/mm2
Fatigue life, N
Figure 11SN curve diagram
zu/jey
With maximum stress or logarithmic maximum stress as the vertical coordinate and logarithmic fatigue life as the horizontal coordinate, mark the test data on single logarithmic or double logarithmic coordinate paper, and use a straight line or curve to perform the best fit to form an S~N curve diagram, as shown in Figure 11. In the S-N curve, the material brand, sample shape and size, surface quality (smoothness, etc.), tensile strength, test speed, test environment atmosphere, etc. should be indicated.
7 Test report
The test report should include the following contents:
Indicate this standard number;
The brand, furnace number, specification, heat treatment process and conventional mechanical properties of the test material, the preparation process of the sample and its shape and size and surface condition (smoothness, etc.), the name and model of the testing machine:
Test speed,
Ambient temperature. If possible, record the sample temperature that is different from the ambient temperature; ambient humidity. If the relative humidity range exceeds 50-70%, it needs to be measured every day during the test; any deviation that does not meet the specified conditions during the test; test results,
Tester, and the date of completion of the test.
A.1 Turning
A.1.1 Rough Turning
GB 433784
Appendix A
Fatigue Specimen Processing Technology
(Reference)
When turning the rough diameter of the specimen from X+5mm (X is the specimen diameter d plus an appropriate surface finishing allowance) to X+0.5mm, it is recommended to use the following gradually decreasing turning depth: 1~0.5~0.25mm.
A.1.2 Finish Turning
When finishing the specimen from X+0.5mm to X, the turning depth should be further reduced. It is recommended to use the following gradually decreasing turning depth: 0.125~0.075~0.05mm.
The recommended cutting depth is 0.06mm/revolution.
A.2 Grinding Finishing
Grinding is used to finish materials that are difficult to finish by turning due to increased strength due to heat treatment. A.2.1 Transverse Grinding
When grinding the specimen from X+0.5mm to X+0.05mm in transverse direction, the following decreasing grinding depth is recommended: 0.03~0.015mm.
When grinding funnel-shaped specimens in transverse direction with a profiled grinding wheel, the grinding wheel and specimen should rotate in the same direction (see figure). Grinding Funnel-Shaped Specimens in Transverse Direction with Profiled Grinding Wheel
A.2.2 Longitudinal Grinding
When grinding the specimen from X+0.05mm to Xmm in transverse direction, the recommended grinding depth is 0.005mm. Multi-hole grinding wheels are suitable for longitudinal grinding of steel. When grinding in longitudinal direction, it is recommended that the grinding wheel speed be controlled at 0.02mm/s for each transverse feed. During grinding, sufficient high-quality coolant, such as water-based solution, should be provided to fully cool the specimen. Note: ① In order to simplify the processing procedures of funnel-shaped specimens, specimens of harder metals can be ground to Xmm in diameter by longitudinal fine grinding after rough turning, but a smaller grinding depth must be used and sufficient cooling must be provided to ensure surface quality. ② If longitudinal fine grinding cannot be implemented temporarily, A.2.2 can be replaced by transverse grinding, but the transverse grinding depth shall not exceed 0.005mm. ③ Measures should be taken and the connecting arc between the test part and the clamping part of the cylindrical specimen should be carefully processed to ensure that the connection between the arc and the cylinder is smooth.
A.3 Surface finishing
After turning or grinding the specimen to Xmm in diameter, it is recommended to use sandpaper or emery cloth with gradually finer sandpaper to perform mechanical polishing along the longitudinal direction of the specimen (try to avoid manual polishing) until the specimen diameter reaches the specified value and obtains a surface finish of √10. 600-grit silicon carbide water-sandpaper is suitable for the final polishing of the test part surface. 256
GB4337.84
When polishing with sandpaper, the force pressed against the specimen surface should be as small as possible, and the surface hardening and residual stress layers should be removed as much as possible. A.4 When conducting comparative tests on different materials, it is recommended to use electrolytic polishing to finish the specimen surface and electrolytically polish off a thin layer.
Note: The notch processing technology of notched specimens can refer to A.1 and A.2, but the grinding finishing is all transverse grinding. Additional notes:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafter of this standard is Gao Shunzhi.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB40--64 "Metal Bending Fatigue Test Method (Trial)" will be invalid. 22 Graphical method
SN curve diagram is a commonly used method to illustrate fatigue test results. The drawing method is as follows: 248
GB 4337--84
Rotational bending fatigue test, 40Cr, b=1176N/mm cylindrical specimen, d=7.5mm, ground surface V9 test speed is 3000rpm, test in air at room temperature Lifting method test failure
Lifting test passed
58kgf/mm
2/568N/mm2bzxZ.net
Fatigue life, N
Figure 11SN curve diagram
zu/jey
With maximum stress or logarithmic maximum stress as the vertical coordinate and logarithmic fatigue life as the horizontal coordinate, mark the test data on single logarithmic or double logarithmic coordinate paper, and use a straight line or curve to perform the best fit to form an S~N curve diagram, as shown in Figure 11. In the S-N curve, the material brand, sample shape and size, surface quality (smoothness, etc.), tensile strength, test speed, test environment atmosphere, etc. should be indicated.
7 Test report
The test report should include the following contents:
Indicate this standard number;
The brand, furnace number, specification, heat treatment process and conventional mechanical properties of the test material, the preparation process of the sample and its shape and size and surface condition (smoothness, etc.), the name and model of the testing machine:
Test speed,
Ambient temperature. If possible, record the sample temperature that is different from the ambient temperature; ambient humidity. If the relative humidity range exceeds 50-70%, it needs to be measured every day during the test; any deviation that does not meet the specified conditions during the test; test results,
Tester, and the date of completion of the test.
A.1 Turning
A.1.1 Rough Turning
GB 433784
Appendix A
Fatigue Specimen Processing Technology
(Reference)
When turning the rough diameter of the specimen from X+5mm (X is the specimen diameter d plus an appropriate surface finishing allowance) to X+0.5mm, it is recommended to use the following gradually decreasing turning depth: 1~0.5~0.25mm.
A.1.2 Finish Turning
When finishing the specimen from X+0.5mm to X, the turning depth should be further reduced. It is recommended to use the following gradually decreasing turning depth: 0.125~0.075~0.05mm.
The recommended cutting depth is 0.06mm/revolution.
A.2 Grinding Finishing
Grinding is used to finish materials that are difficult to finish by turning due to increased strength due to heat treatment. A.2.1 Transverse Grinding
When grinding the specimen from X+0.5mm to X+0.05mm in transverse direction, the following decreasing grinding depth is recommended: 0.03~0.015mm.
When grinding funnel-shaped specimens in transverse direction with a profiled grinding wheel, the grinding wheel and specimen should rotate in the same direction (see figure). Grinding Funnel-Shaped Specimens in Transverse Direction with Profiled Grinding Wheel
A.2.2 Longitudinal Grinding
When grinding the specimen from X+0.05mm to Xmm in transverse direction, the recommended grinding depth is 0.005mm. Multi-hole grinding wheels are suitable for longitudinal grinding of steel. When grinding in longitudinal direction, it is recommended that the grinding wheel speed be controlled at 0.02mm/s for each transverse feed. During grinding, sufficient high-quality coolant, such as water-based solution, should be provided to fully cool the specimen. Note: ① In order to simplify the processing procedures of funnel-shaped specimens, specimens of harder metals can be ground to Xmm in diameter by longitudinal fine grinding after rough turning, but a smaller grinding depth must be used and sufficient cooling must be provided to ensure surface quality. ② If longitudinal fine grinding cannot be implemented temporarily, A.2.2 can be replaced by transverse grinding, but the transverse grinding depth shall not exceed 0.005mm. ③ Measures should be taken and the connecting arc between the test part and the clamping part of the cylindrical specimen should be carefully processed to ensure that the connection between the arc and the cylinder is smooth.
A.3 Surface finishing
After turning or grinding the specimen to Xmm in diameter, it is recommended to use sandpaper or emery cloth with gradually finer sandpaper to perform mechanical polishing along the longitudinal direction of the specimen (try to avoid manual polishing) until the specimen diameter reaches the specified value and obtains a surface finish of √10. 600-grit silicon carbide water-sandpaper is suitable for the final polishing of the test part surface. 256
GB4337.84
When polishing with sandpaper, the force pressed against the specimen surface should be as small as possible, and the surface hardening and residual stress layers should be removed as much as possible. A.4 When conducting comparative tests on different materials, it is recommended to use electrolytic polishing to finish the specimen surface and electrolytically polish off a thin layer.
Note: The notch processing technology of notched specimens can refer to A.1 and A.2, but the grinding finishing is all transverse grinding. Additional notes:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafter of this standard is Gao Shunzhi.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB40--64 "Metal Bending Fatigue Test Method (Trial)" will be invalid. 22 Graphical method
SN curve diagram is a commonly used method to illustrate fatigue test results. The drawing method is as follows: 248
GB 4337--84
Rotational bending fatigue test, 40Cr, b=1176N/mm cylindrical specimen, d=7.5mm, ground surface V9 test speed is 3000rpm, test in air at room temperature Lifting method test failure
Lifting test passed
58kgf/mm
2/568N/mm2
Fatigue life, N
Figure 11SN curve diagram
zu/jey
With maximum stress or logarithmic maximum stress as the vertical coordinate and logarithmic fatigue life as the horizontal coordinate, mark the test data on single logarithmic or double logarithmic coordinate paper, and use a straight line or curve to perform the best fit to form an S~N curve diagram, as shown in Figure 11. In the S-N curve, the material brand, sample shape and size, surface quality (smoothness, etc.), tensile strength, test speed, test environment atmosphere, etc. should be indicated.
7 Test report
The test report should include the following contents:
Indicate this standard number;
The brand, furnace number, specification, heat treatment process and conventional mechanical properties of the test material, the preparation process of the sample and its shape and size and surface condition (smoothness, etc.), the name and model of the testing machine:
Test speed,
Ambient temperature. If possible, record the sample temperature that is different from the ambient temperature; ambient humidity. If the relative humidity range exceeds 50-70%, it needs to be measured every day during the test; any deviation that does not meet the specified conditions during the test; test results,
Tester, and the date of completion of the test.
A.1 Turning
A.1.1 Rough Turning
GB 433784
Appendix A
Fatigue Specimen Processing Technology
(Reference)
When turning the rough diameter of the specimen from X+5mm (X is the specimen diameter d plus an appropriate surface finishing allowance) to X+0.5mm, it is recommended to use the following gradually decreasing turning depth: 1~0.5~0.25mm.
A.1.2 Finish Turning
When finishing the specimen from X+0.5mm to X, the turning depth should be further reduced. It is recommended to use the following gradually decreasing turning depth: 0.125~0.075~0.05mm.
The recommended cutting depth is 0.06mm/revolution.
A.2 Grinding Finishing
Grinding is used to finish materials that are difficult to finish by turning due to increased strength due to heat treatment. A.2.1 Transverse Grinding
When grinding the specimen from X+0.5mm to X+0.05mm in transverse direction, the following decreasing grinding depth is recommended: 0.03~0.015mm.
When grinding funnel-shaped specimens in transverse direction with a profiled grinding wheel, the grinding wheel and specimen should rotate in the same direction (see figure). Grinding Funnel-Shaped Specimens in Transverse Direction with Profiled Grinding Wheel
A.2.2 Longitudinal Grinding
When grinding the specimen from X+0.05mm to Xmm in transverse direction, the recommended grinding depth is 0.005mm. Multi-hole grinding wheels are suitable for longitudinal grinding of steel. When grinding in longitudinal direction, it is recommended that the grinding wheel speed be controlled at 0.02mm/s for each transverse feed. During grinding, sufficient high-quality coolant, such as water-based solution, should be provided to fully cool the specimen. Note: ① In order to simplify the processing procedures of funnel-shaped specimens, specimens of harder metals can be ground to Xmm in diameter by longitudinal fine grinding after rough turning, but a smaller grinding depth must be used and sufficient cooling must be provided to ensure surface quality. ② If longitudinal fine grinding cannot be implemented temporarily, A.2.2 can be replaced by transverse grinding, but the transverse grinding depth shall not exceed 0.005mm. ③ Measures should be taken and the connecting arc between the test part and the clamping part of the cylindrical specimen should be carefully processed to ensure that the connection between the arc and the cylinder is smooth.
A.3 Surface finishing
After turning or grinding the specimen to Xmm in diameter, it is recommended to use sandpaper or emery cloth with gradually finer sandpaper to perform mechanical polishing along the longitudinal direction of the specimen (try to avoid manual polishing) until the specimen diameter reaches the specified value and obtains a surface finish of √10. 600-grit silicon carbide water-sandpaper is suitable for the final polishing of the test part surface. 256
GB4337.84
When polishing with sandpaper, the force pressed against the specimen surface should be as small as possible, and the surface hardening and residual stress layers should be removed as much as possible. A.4 When conducting comparative tests on different materials, it is recommended to use electrolytic polishing to finish the specimen surface and electrolytically polish off a thin layer.
Note: The notch processing technology of notched specimens can refer to A.1 and A.2, but the grinding finishing is all transverse grinding. Additional notes:
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafter of this standard is Gao Shunzhi.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB40--64 "Metal Bending Fatigue Test Method (Trial)" will be invalid. 2005mm. ③ Measures should be taken and the connecting arc between the test part and the clamping part of the cylindrical specimen should be carefully processed to ensure that the connection between the arc and the test part is smooth.
A.3 Surface finishing
After turning or grinding the specimen to Xmm in diameter, it is recommended to use sandpaper or sandpaper with gradually finer grains to perform mechanical polishing along the longitudinal direction of the specimen (try to avoid manual polishing) until the specimen diameter reaches the specified value and the surface finish of √10 is obtained. 600-grit silicon carbide water-sandpaper is suitable for the final polishing of the test part surface. 256
GB4337.84
When polishing with sandpaper, the force pressed on the specimen surface should be as small as possible, and the surface hardening and residual stress layer should be removed as much as possible. A.4 When conducting comparative tests on different materials, it is recommended to use electrolytic polishing to perform surface finishing of the specimen, and electrolytic polishing should be removed a thin layer.
Note: The notch processing technology of notch specimens can refer to A.1 and A.2, but the grinding finishing is all transverse grinding. Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafter of this standard is Gao Shunzhi.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB40--64 "Metal Bending Fatigue Test Method (Trial)" will be invalid. 2005mm. ③ Measures should be taken and the connecting arc between the test part and the clamping part of the cylindrical specimen should be carefully processed to ensure that the connection between the arc and the test part is smooth.
A.3 Surface finishing
After turning or grinding the specimen to Xmm in diameter, it is recommended to use sandpaper or sandpaper with gradually finer grains to perform mechanical polishing along the longitudinal direction of the specimen (try to avoid manual polishing) until the specimen diameter reaches the specified value and the surface finish of √10 is obtained. 600-grit silicon carbide water-sandpaper is suitable for the final polishing of the test part surface. 256
GB4337.84
When polishing with sandpaper, the force pressed on the specimen surface should be as small as possible, and the surface hardening and residual stress layer should be removed as much as possible. A.4 When conducting comparative tests on different materials, it is recommended to use electrolytic polishing to perform surface finishing of the specimen, and electrolytic polishing should be removed a thin layer.
Note: The notch processing technology of notch specimens can refer to A.1 and A.2, but the grinding finishing is all transverse grinding. Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is drafted by the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The main drafter of this standard is Gao Shunzhi.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB40--64 "Metal Bending Fatigue Test Method (Trial)" will be invalid. 2
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