The German TüV bending test is that the wheel does not rotate and the bending load rotates. A certain bending moment is applied to the test wheel by the centrifugal force generated when the load rotates. During the test, the bending load to which the wheel should be subjected is calculated using the following formulae or given directly by the automobile manufacturer. Regardless of the German TüV standard, the US SFI standard or the Japanese JWL standard or its calculation formula are the same. The following formula: M = KF (μR + e) ​​(1) where M - the value of the moment applied to the wheel, Nm K - the wheel load factor F - the allowable load wheel load, Nμ - the tire and the road surface The coefficient of friction R—the dynamic rolling radius when the wheel is mounted with the largest tire, me—the offset value of the wheel, m When the formula is actually applied, K=2, μ=0.9 in the TüV standard; in the SFI standard, When the nominal diameter of the wheel D≤406.4mm, take K=1.6, μ=0.7; when the nominal diameter of the wheel D≥419.1mm, take K=1.35, μ=0.7; in the JWL standard, the value of K, μ and SFI The same. In the TÜV standard, after the bending moment value M is calculated from the formula, 75% of the M value is taken as the heavy load in the test. Under this load, 4 test wheels are completed, and each test wheel needs to complete 200,000 cycles. After completing 200,000 cycles, if one of the 4 test wheels is found to have fatigue cracks (crack length is not less than 3mm), the test wheel is unqualified and the test is stopped; if 200,000 cycles, 4 tests If there are no fatigue cracks in the wheels, additional tests must be continued on the four test wheels until a fatigue crack occurs. The final offset of the test is greater than 110% of the initial offset value before the test is stopped. Record the total number of test cycles and the occurrence of fatigue cracks for each test wheel. Then take 50% of the M value as the light load in the test, and test the other 4 test wheels under this load, so that each wheel can complete 1.8 million cycles. If one of the four test wheels has fatigue cracks (the crack length is not less than 3mm), then the test wheel is judged to be unqualified and the test is stopped; if there are no fatigue cracks in the four test wheels, continue to these 4 pieces. Additional tests were performed on the wheels until fatigue cracks occurred, and when the final offset value was greater than 110% of the initial offset value, the test was stopped. Record the number of actual test cycles and the occurrence of fatigue cracks for each test wheel. Based on the test completion of the above eight test wheels, Weibull bending fatigue life analysis was performed on the test wheels (see the attached figure). The analysis steps are as follows: (1) Find the average value of the light load cycle number n 0. (2) Find the average value of the heavy load cycle m 0. (3) Calculate logarithmic deviation values ​​lgε1, lgε2 at light and heavy loads, respectively. Lgε1={[(lgn 1-lgn 0)2+(lgn 2-lgn 0)2+(lgn 3-lgn 0)2+(lgn 4-lgn 0)2]/3}1/2 and lgε2={[(lgm 1-lgm 0) 2+ (lgm 2-lgm 0) 2+ (lgm 3-lgm 0) 2+ (lgm 4-lgm 0) 2]/3} 1/2 requires lgε 1 0.2 0.2, lgε 2 0.2 0.2 where n 1 n 2, n 3, n 4 - the number of cycles for 4 test wheels at 50% M, m 1, m 2, m 3, m 4 - respectively, the number of cycles for 4 test wheels at 75% M ( 4) Calculate the inclination K of the Weibull curve. K=lg(n 0/m 0)/lg(M 1/M 2), generally requires K ≥ 5 M 1 - bending load value at light load M 2 - bending load value at heavy load When the above analysis meets the requirements, it is considered that the aluminum alloy wheel of this model is qualified, otherwise it is unqualified. In the SFI standard, the result calculated by formula (1) directly acts on the test wheel, and it is required to complete 100,000 working cycles, and a total of 3 test wheels are completed. The United States General Motors Corporation, after completing two 100,000 cycles, added seven test wheels without fatigue cracks. Each test wheel had to complete a total of 250,000 work cycles (this is the wheel bending fatigue test). In the B 10 lifetime, the Weibo B 10 cycle life analysis was finally performed on the test results. The requirements of the bending fatigue test in the JWL standard are similar to those of the SFI standard. Three test wheels are required to complete. The number of cycles is generally 200,000 rpm (but Toyota and Honda sometimes require 1 million cycles to complete), and no longer B. 10 Lifetime and Weibull Life Analysis. Dynamic radial fatigue test Dynamic radial fatigue test is used to simulate the pressure on the tire when the car is driving straight or turning. The test requires that the diameter of the test machine drum driving the rotation of the test wheel is not less than 1.7m, and the radial pressure acting on the test wheel is: F r = fF Where F r - Test load, NF - Permissible dead load wheel Load, N f - wheel load reinforcement factor in TüV standard, f = 2.5, number of test wheels is 2, test tire pressure is 448kPa ± 14kPa, test run is 2000km, after test, no visible fatigue cracks are detected with a flaw detector . In the JWL standard, f=2.25, the number of test wheels is 3, and the tire pressure during the test is 460 kPa±14 kPa. Generally, the number of revolutions is required to complete 3 million rpm, and no visible fatigue cracks are observed with the flaw detector. In the SFI standard, f = 2.25, the number of test wheels is 7, and the tire pressure during the test is 448kPa ± 14kPa. Generally, 1 million samples of diverted testing agent are required to be inspected for no visible cracks, and an additional 1.5 times is required to complete the requirement of 10 turns. . Impact Test 1.13° Impact Test The 13° impact test simulates the impact of a car crashing on the edge of a road during driving and checks the impact resistance of the wheel. In the TüV standard, SFI standard, and JWL standard, there are 13° impact test requirements. The formula for the impact load is: G=0.6F+180 where G—impact weight mass, kg F—allowed static load wheel load, The impact load drop height is 230mm, and the hammer impact wheel width is 25.4mm (measured from the outer rim inward). Each test wheel type must use the tires specified by the manufacturer and the tire inflation pressure is 200kPa±10kPa. The number of test wheels is: In the TüV standard and SFI standard, two tests are to be performed, namely the valve hole and a spoke; In the JWL standard, four tests are required, followed by 0° (valve hole), 90°, 180°, and 270° (front-view wheel, clockwise). Each wheel requires spokes, bolt holes, and installation parts without cracks, no separation, no leakage. Deformation and non-penetrating cracks at the rim of the impact site are allowed. 2.90°impact test and 30°impact test The 90°impact test simulates the situation where the wheel directly hits an obstacle during driving and checks the impact resistance of the wheel rim. There is no specific requirement for this test in the TüV standard and SFI standard. This test requirement is only available in the JWL standard. The test method is to install the test wheel on the tire specified by the manufacturer (tire pressure is generally 260kPa), install it on a 90° impact tester, and then raise the weight to a specified height to drop it (half the impact rim) To test the impact resistance of the rim. The impact weight of this tester is 1000kg. The change of impact energy is achieved by changing the height of the drop of the hammer. According to the test wheel bearing capacity, there are three different requirements of 125mm, 204mm and 254mm. The number of wheels tested was 0° (valve hole), 90°, 180°, and 270° each. The criteria for this test are generally to allow deformation and cracks in the rim, allowing the wheel to leak, not allowing the rim to separate from the spokes, and not allowing cracks at the spokes and mounting flanges. The 30° impact test has been replaced by the 13° impact test, but it still exists in certain Japanese wheel tests. For example, in the Land Cruiser produced by the Toyota Motor Corporation of Japan, the aluminum wheels are used. 30° impact test is required. The tire used is 275/65R17, the tire pressure is 260kPa, the impact height is 472mm, and the test impact parts are 0°, 90°, 180°, and 270°, and each test result wheel is required. Allow deformation, no cracks appear. Conclusion Through the above summary of the aluminum alloy wheel rig test results can be seen: (1) Germany TüV standard focus on bending test, by calculating the bending load M is divided into light load, heavy load in two parts, each load to do 4 test Not only the stability of the wheel manufacturing process was examined, but also the finite life of the wheel was analyzed by the Weibull fatigue life curve. The requirements for radial fatigue test and impact test are not very high, especially the requirement of 90° impact test. The reason why the analysis of the TüV standard is in line with the actual situation in Germany. Because Germany's road surface quality is good, there is no speed limit in the vehicle's driving. In order to understand the vehicle's life span before the vehicle reaches the service age, Weibull fatigue life analysis should be performed in the wheel test. (2) B 10 life is required for both bending and radial tests in the US SFI standard. The number of wheels required to be tested is more (9 and 7 pieces, respectively) but the number of required cycles is not large (bending is 2 pieces 10 Million cycles, B 10 is 7 pieces of 250,000 cycles; radial fatigue is 1 million pieces without cracks, and then added to 2.5 million pieces). This stipulates that the test requirements are compatible with the actual situation in the United States. In the United States, there is a limit to the maximum speed of the vehicle, and the entire vehicle has the limitation of the useful life. By thus specifying the test requirements, the wheel and the vehicle will basically reach the service life at the same time. (3) Japan's JWL standard is also in line with Japan's national conditions. Japan is an island country, with poor road conditions and lack of resources. Therefore, Japanese cars are relatively compact and have maximum speed limit and vehicle service life while the vehicle is traveling. limits. Therefore, in the Japanese wheel test, the general required test load is not large, there is no requirement for the test speed, and the required impact test is more to test the stability of the wheel manufacturing process. In summary, although national standards require different focuses for wheel tests, they are all compatible with the national conditions. At present, after more than 10 years of rapid development, China’s automobile industry has become a major automobile manufacturing country in the world, but most of them are imported foreign models. Similarly, manufacturing standards are also foreign (standards for whoever imports the car), which is not suitable for the actual situation in China. For example, Article 67 of the "Law of the People's Republic of China on Road Traffic Safety" stipulates that the maximum speed indicated on the expressway speed limit sign must not exceed 120km. Especially in China, family cars are mostly driven in cities, and the speed is relatively low. Low (usually only 40-80km/h). In addition, the situation in our country is poor. Except for the expressway, many road sections are not suitable for high-speed driving. Therefore, in the wheel rig test, the test speed should not be too high. It is recommended that the bending test speed be 350 to 700 r/min, and the radial test speed should be about 50 km/h. Since China has its own life expectancy for passenger cars and cars (different car models now have different requirements), in the future, the service life of cars should be determined according to the type of car (such as low, medium and high level), so that cars can be treated as cars. The required service life specifies the number of test cycles required for aluminum alloy wheels. Therefore, China should formulate wheel test standards in accordance with China's national conditions and require all vehicle manufacturers and wheel manufacturers to comply with this standard for all wheels sold in China. * Efficient: The electronically controlled hydrostatic drive system and multi functional joystick provide high levels of performance and maneuverability. SEM816 Bulldozer,SEM816 Coal Bulldozer,SEM816 Crawler Bulldozer,SEM816 250HP Crawler Bulldozer Jinan Tengde Equipment Co., Ltd. , http://www.cat-semmachinery.com
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