Modern warfare demands higher and higher adaptability, mobility, and rapid response capability of military off-road vehicles, and the requirements for the use performance of military off-road vehicle tires are correspondingly increased. Traditional bias tires can no longer meet the requirements of military off-road vehicles on the performance of tires, radial requirements for military off-road vehicle tires more and more urgent. Although domestic light and medium military off-road tires have partially achieved radialization, due to various reasons, large-size off-road tires used in domestic heavy-duty military off-road vehicles still use skew structures. This situation has seriously hampered the development of China's heavy military off-road vehicles and the actual performance of the relevant military equipment. Therefore, according to military requirements, we developed a large-size, tubeless military off-road radial tire that is suitable for ultra-low-pressure driving to meet the performance requirements of heavy-duty military off-road vehicles. The design is introduced as follows.
1 Outer profile design In order to ensure that the off-road tires have good passability, the design of the tire's running surface is appropriately wider, so that the ground pressure can be reduced to adapt to the ultra-low pressure of the soft-base road. At the same time, due to the large height of the off-road tire's running surface, a three-segment arc design is adopted, ie, the radius of the primary traveling surface is large, and the radius of the transition arc on both sides is small. In this way, the road pressure of good roads (general engineers of military companies using military off-road tires, which are mainly engaged in the development and design of military off-road radial tires, and process pressures of road pressure and off-road pressure, and the road pressure is slightly higher than off-road pressure) The tire grounding surface is small, rolling resistance is small, and its high-speed performance can be exerted. When the off-road pressure is used in poor road conditions or no road conditions, the grounding surface of the tire is large, which can improve the tire's passing performance on the soft foundation road surface. In addition, when the tire is running on a soft foundation road with an ultra-low pressure, most of the sidewalls above the horizontal axis have been in contact with the ground. The shoulder region is prone to stress concentration, and the sidewall below the horizontal axis near the rim of the rim has been The rim pressure is easy to damage the sidewall. Therefore, in order to reduce the excessive concentration of stress on the shoulder region, the ground contact portion of the shoulder portion and the crown are excessively smooth, and the shoulder portion is designed with a large arc; the radius of the sidewall curve below the horizontal axis is appropriately increased to enhance the upper end of the rim flange. Sidewall support (see).
2 Tire pattern design Military off-road tires have always used "herringbone" pattern.
The groove pattern is deep and wide, and the block area accounts for the tread surface design of the tread: design; the proportion of the lower sidewall curve design with supporting performance is small, and the mountain cross-country and climbing performance is more prominent, but not It is conducive to ultra-low pressure driving on soft ground and high-speed driving on good roads. In addition, the “Riblet†pattern tires have large rolling noise and rolling resistance, high fuel consumption, poor wear resistance, ride comfort and handling stability, and the “Riblet†pattern is a directed pattern. Need to recognize the direction, inconvenience to replace tires in the war. Therefore, the “undirected block†pattern with better comprehensive performance is more suitable for the performance requirements of the current military off-road vehicle than the “Ribbon†pattern.
The depth is shallow and the longitudinal groove is dominant. The width of the lateral groove is small, which can reduce the peristalsis and heat generation of the block, reduce tire noise, vibration and hysteresis loss, and improve the high-speed running performance, ride comfort and manipulation of the tire. stability. The pattern of shoulder shoulders is dominated by the lateral grooves, and the grooves are wide and deep. This allows the tires to have a good grip on the ground during off-road driving and is conducive to drainage, heat dissipation and self-cleaning of the patterns. The right and left blocks of the entire row of blocks or the lengths of the blocks in the adjacent rows (see) make the shoulder part of the pattern form a large concave and convex surface, which can increase the grip of the tire on the ground, and can also make up for block patterns. Herringbone patterns have the disadvantage of poor cross-country and poor climbability.
The arrangement of the tread pattern at the shoulder part a indicates the length of the adjacent rows of blocks, and b indicates the right and left blocks of the entire row. 3 Selection of carcass material For large radial tires, it can be divided into two types: steel and semi-steel. Species. All steel radial tire carcasses have only one layer of steel cords, which have low rolling heat and are suitable for high-speed driving on good roads. However, on poor roads or roads, their thin sidewalls are easily damaged to the carcass steel cords. Causes the steel cord to separate from the carcass rubber and even rust breaks. In addition, all-steel radial tires have poor gas-free use and are not suitable for use at ultra-low pressures (below 50 kPa).
The carcass of the semi-steel radial tire is a multi-layer high-strength fiber ply. The sidewall is solid, and the anti-hook and hanging damage performance is good. Even if the outer carcass ply is hurt, the inner carcass ply still works. The fear of rusting the cords is especially important when there is no road on the battlefield or when the soft ground road (wet or desert) is under low pressure. At the same time, the resistance to bending deformation and fatigue resistance of fiber cords is much higher than that of steel cords, which is an important factor for whether tires can run at low pressures. Therefore, the adaptability of semi-steel radial tires to various road conditions is more suitable for military off-road vehicles.
At present, the carcass skeleton materials used for semi-steel radial tires are mainly modified nylon and polyester cords. Modified nylon cords have low heat generation, good fatigue resistance and strength, but poor dimensional stability; polyester cords have higher heat generation, poorer fatigue resistance than nylon cords, and good dimensional stability, but the carcass More than 3 layers of curtain fabric should not be used.
The performance comparison results of the modified nylon and DSP polyester cords used on 12.5R20 military off-road radial tires are shown in Table 1. It can be seen from Table 1 that for large military air-to-ground radial tires that are adapted to ultra-low pressure, the use of Nylon cords are more suitable for carcass skeleton materials.
Table 1 12.5R20 Military Off-road Radial Tires with Different Material Cords Performance Comparison Item Standard Value 4-ply carcass ply 3-ply carcass ply Standard rim test Pneumatic / kPa Durability 1 138 (child shoulder bag) 199.8 (side drum kit) High speed Performance / min 55 (crown space) 93 (crown space) hydraulic blasting test failure form side of the ring break (5.5 times) one side of the wire ring fracture (5.3 times) one side of the wire ring fracture (4.9 times) times. A semi-cylindrical machine head is used to ensure accurate positioning of the carcass 4 process cord and to prevent the carcass ply from being deformed during the molding process. Skirt, a section of the use of such as the use of a semi-steel structure, the carcass by a multi-layer modified nylon fabric structure under the process: pre-production of fabric tube, expand the guide ※ retractor on the curtain fabric, the bead is mostly double wire ring structure, Therefore, the molding method is 2% (down on page 480), and the silk radial tire is 11% smaller; the aramid single-layer carcass 6.50R16 light truck radial tire is 14.4 % lower than the same specification 3-layer polyester carcass radial tire. 4.3%. In order to evaluate the fatigue resistance of Kevlar cords, an indoor durability test and a practical mileage test were performed on aramid belt light duty radial tires. As a result, the cord strength retention rate was 98% after 120 hours of durability performance test, and the cord strength retention rate was 90.17% after actual driving of 76,000 km. The test results show that the aramid cord has better fatigue resistance than Other synthetic fiber cords are poor, but they can still meet the requirements of tires.
Giant construction machinery tires work in the mining area, and the conditions of use are very harsh. Most of the tires are damaged due to thorns by the ore, and the tire has a very short service life, causing great economic losses. According to the unique cut-resistant and puncture-resistant properties of aramid, the aramid cords are used in the buffer layer of construction machinery tires to protect the carcass. For example, 18.00 to 3332PR aramid cushion tires have good puncture resistance, and their service life is 65% higher than that of nylon tires of the same specification and 18% higher than that of aramid-nylon composite buffer tires. Aramid cushion tires are used in construction machinery tires. The increase in life expectancy can reduce the cost, reduce the number of tire replacements, improve the use efficiency, and have a high technical and economic value.
5 Conclusion Aramid fiber has high fracture strength, high modulus, high temperature resistance and unique cutting resistance.
Aramid cords have high dynamic modulus, good elasticity, and low hysteresis loss rate, but they are slightly less resistant to fatigue.
Aramid radial tires have high speed performance, low mass, and low rolling resistance. Kevlar cushion tires have outstanding puncture resistance, high mileage, and significant social and economic benefits.
The 5th National Seminar on Fabrics and Skeleton Materials for the Rubber Industry 5 Conclusion When designing military off-road radial tires, full consideration must be given to the specificity of the use of off-road tires in the military, in order to ensure the main characteristics of the tires. 71994-2015 China Academic (Continued from page 475. ) The barrel and the finger-shaped bag ※ The capsule flipper completes the packing circle; The two-stage molding adopts the radial condensation outer-casing type capsule machine head. The rubber of the crown is compounded by two rubbers of the upper and lower two sides, so that the composite crown rubber has both good wear resistance and low heat, ensuring the high-speed running performance of the tire.
Under the premise of energy, we must balance other performances, especially the use of tireless radial tires, bullet-proof radial tires, and central charging and ventilating systems, and put forward more on the design of tires (the form of rims and the cooperation of tires and rims). ,higher requirement. This requires designers to learn more about the performance and use characteristics of military vehicles and provide a reliable basis for the design of tires. The continuous emergence of new tire technology, new materials, new processes and new equipment provides a vast space for the design and production of higher performance and better military tires.
Receipt date: G02-030
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