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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Petroleum and Chemical Industry Federation.
This standard is under the jurisdiction of SAC/TC 19 National Technical Committee on Tyres and Rims of Standardization Administration of China.
Evaluating impact resistance for passenger car tyres
1 Scope
This standard specifies the requirements, test method, judgment rules and test report for evaluating impact resistance for passenger car tyres by pendulum method.
This standard is applicable to new series (30 to 65) of tubeless pneumatic passenger car tyres and is not applicable to run-flat tyres and temporary-use spare tyres.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 2978 Size designation, dimensions, inflation pressure and load capacity for passenger car tyres
GB/T 3487 Rims for passenger car
GB/T 6326 Tyre terms and definitions
GB/T 8170 Rules of rounding off for numerical values & expression and judgement of limiting values
GB/T 30195 Test method for measuring impact performance of motor vehicle tyres
HG/T 2177 Appearance quality of tyres
3 Terms and definitions
For the purpose of this standard, the terms and definitions specified in GB/T 6326 and GB/T 30195 as well as the followings apply.
3.1
striker angle
angle formed by the center plane of the wheel and the intersection line of the center plane of the striker and the curved surface at the front end of the striker, as shown in Figure 1a)
3.2
camber angle; CA
projection of striker angle on a horizontal plane passing through the wheel rotation axis, as shown in Figure 1b)
3.3
slip angle; SA
projection of striker angle on vertical plane passing through the wheel rotation axis, as shown in Figure 1c)
a) Striker angle b) Camber angle c) Slip angle
Key:
1——tyre;
2——striker.
Figure 1 Striker angle, slip angle and camber angle
3.4
impact energy
E
kinetic energy at the moment when the striker falls from the drop height or angle and hits the tyre
3.5
impact bulge
abnormal bulging of tyre side caused by impact on the tyre
3.6
air leakage
obvious and continuous drop of tyre pressure due to impact on the tyre
3.7
impact bulge height
Hb
height at which a tyre bulges after being impacted
3.8
robustness factor
f
index for evaluating the impact resistance of tyres
3.9
impact bulge energy
Ebu
impact energy when the striker impacts the tyre, causing bulge or air leakage of the tyre
3.10
machined steel rim
steel rim machined only for indoor tests, with the profile curve of the rim meeting the requirements of GB/T 3487
4 Evaluation requirements
4.1 The robustness factor of tyres under test shall be no less than those specified in Table 1.
Table 1 Robustness factor of tubeless pneumatic passenger car tyres In: N·m2
Nominal aspect ratio of tyres Series 65, 60 and 55 Series 50 Series 45 and 40 Series 35 and 30
Robustness factor (f) 80 65 50 30
4.2 Substitute the robustness factor (f) specified in Table 1 into Equation (1) to obtain the minimum impact bulge energy (Ebu min) that the test tyre needs to bear, and round it to a single digit and take an integer according to those specified in GB/T 8170.
(1)
Where,
Ebu min——the minimum impact bulge energy of the tyre, J.
f——the robustness factor, N·m2.
LI——the load index of the tyre, dimensionless. For standard tyres, the load index of standard tyres is adopted; for the enhanced type tyres, the load index of the standard tyres corresponding to the specification is adopted; for tyres with only enhanced load but no standard load, the load index is subtracted by 4 from the load index of the enhanced tyres.
C——the constant, C=80mm.
H——the nominal section height of tyre, mm, which is calculated using Equation (2) and rounded to an integer (mm).
D——the outer diameter of tyre, mm, which is calculated using Equation (3) and rounded to an integer (mm).
H=Sn×Ar÷100 (2)
Where,
Sn——the nominal section width, mm;
Ar——the nominal aspect ratio.
D=Dr+2H (3)
Where,
Dr——the nominal rim diameter, mm;
H——the tyre section height, mm.
5 Test method
5.1 Instruments and apparatus
5.1.1 Impact test equipment
The striker, striker support and striker assembly of the impact test equipment shall meet the requirements of Annex A, while the others shall meet the requirements of GB/T 30195.
5.1.2 Impact bulge gauge
The impact bulge gauge consists of a dial indicator and a support, see Annex B for details.
5.1.3 Inflation pressure gauge or air pressure sensor
Hand-held inflation pressure gauge or air pressure sensor, with an accuracy of ±5 kPa.
5.1.4 Image recorder
Impact bulges or air leakage during the test shall be recorded by colorful, clear and storable image recorder.
5.2 Test conditions and preparation
5.2.1 The test tyre shall be placed for over 24h after vulcanization and the appearance quality shall meet the requirements of HG/T 2177.
5.2.2 The test environment temperature shall be 20 ℃~30 ℃.
5.2.3 The test rims shall be machined steel rims specially designed for the impact resistance test of passenger car tyres, and their specification and model shall be in line with that of measured rims defined in GB/T 2978; for the tyres of vehicles equipped with flexible rims, the flexible rims consistent with the requirements of the vehicle shall be used for testing, and stated in the test report.
5.2.4 Install the test tyre on the test rim as specified in 5.2.3 and inflate the tyre with air pressure of 200kPa. Lubricant can be used for installing tyres.
5.2.5 The tyre rim assembly after inflation shall be placed at the test ambient temperature for more than 3h.
5.2.6 Determine 5 test points distributed at approximately equal intervals along the circumferential direction of the tyre, and mark and number them one by one.
5.2.7 The striker angle of the tyre impact resistance tester is fixed at a camber angle of 6° and a slip angle of 0°, with a deviation of ±0.5°.
5.3 Test procedures
5.3.1 Re-adjust the air pressure of the placed test tyre to the value as specified in 5.2.4, with the deviation not exceeding ±2 kPa. If the air pressure of the placed test tyre has abnormal loss, observe the conditions of the test tyre and rim and re-prepare the test tyre.
5.3.2 Install the test tyre rim assembly on the test device as per GB/T 30195, and lock the rim so that it cannot rotate in the circumferential direction. Then test point by point according to the marked serial number.
5.3.3 Adjust the pendulum rod to the free suspension state so that the tyre rotation center and the top of the striker are on the same horizontal line; adjust the tyre position horizontally so that the shoulder touches the middle of the striker. The angular displacement of the pendulum rod caused by tyre touching striker shall not exceed 0.1°.
5.3.4 Lift the striker to a certain extent where its impact energy is equal to the minimum impact bulge energy specified in 4.2, and lock the pendulum rod.
5.3.5 Allow the striker to fall freely from the locked position to impact the test tyre. When the striker rebounds, the locking device locks the pendulum rod to prevent secondary impact. Then the locking device retreats the tyre and the pendulum rod slowly falls to a free hanging state.
5.3.6 After each test point is impacted for 3 min, check the vicinity of the impact point using the impact bulge gauge specified in 5.1.2 and record the check results; measure tyre pressure using the inflation pressure gauge/air pressure sensor specified in 5.1.3 and record the results; record any damage (such as impact bulge or crack) at the impact site with the image recorder specified in 5.1.4.
5.3.7 If the tyre leaks or the air pressure loss within 3 min exceeds 5% of the air pressure as specified in 5.2.4, the tyre and rim shall be checked. In case of obvious air leakage caused by damaged rim, it shall be handled according to 5.3.10. In case of obvious air leakage caused by damaged and cracked tyres, the test shall be terminated, and the location of the crack where the air leakage is found shall be recorded with the image recorder specified in 5.1.4. If the damage of the tyre and rim is not obvious, the test tyre rim assembly should be removed after the impact point is marked, and then check the tyre; if the tyre is found to be damaged, the test shall be terminated and the damaged position shall be recorded with the image recorder specified in 5.1.4; if the tyre is not damaged, re-assemble it (the rim is allowed to be replaced) and inflate it with the air pressure specified in 5.2.4. After 15 min of inflation, re-check whether the tyre is cracked, and measure the air pressure and impact bulge height.
5.3.8 Before impacting the next test point, the air pressure of the test tyre shall be readjusted to the air pressure specified in 5.2.4 (the deviation shall not exceed ±2kPa); at the same time, check whether the fastening bolt of the striker is loose.
5.3.9 If the impact bulge height of each impact point is less than 1mm, keep it still for 30 min. After that, recheck the impact bulge height.
5.3.10 If the rim is damaged due to impact during the test, replace the rim and reassemble the tyre, then inflate it according to those specified in 5.2.4. Recheck the tyre for cracking, and measure the air pressure and the impact bulge height 15 min later after inflation.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Evaluation requirements
5 Test method
6 Judgment rules
7 Test report
Annex A (Normative) Striker, striker support and striker assembly
Annex B (Informative) Impact bulge gauge
