Modern warfare has increasingly higher requirements for the suitability, mobility and rapid response capabilities of military off-road vehicles, and the requirements for the performance of military off-road vehicle tires have also increased accordingly.Traditional bias tires can no longer meet the requirements of military off-road vehicle tire performance, and the requirements for radialization of military off-road vehicle tires are becoming more and more urgent.Although the current domestic light and medium military off-road tires have partially achieved radialization, due to various reasons, the large-size off-road tires used in domestic heavy-duty military off-road vehicles still adopt a bias structure.This situation has severely restricted the development of China’s heavy-duty military off-road vehicles and the actual combat performance of related military equipment.Therefore, we have developed a tubeless military cross-country radial tire with a high speed and adaptable to ultra-low pressure to meet the performance requirements of the army’s heavy-duty military cross-country vehicles.The design situation is now introduced as follows.
1 The outer contour is designed to ensure the good passability of the off-road tires, and the tire running surface is designed to be wider, so that the ground pressure can be reduced to adapt to the ultra-low air pressure driving on the soft ground.At the same time, because off-road tires have a large running surface height, a three-segment arc design is adopted, that is, the arc radius of the main running surface is larger, and the radius of the transition arcs on both sides is smaller.In this way, when driving under good road pressure (general military off-road tires use pneumatic company engineers, now mainly engaged in the development and design of military off-road radial tires and the process pressure has two kinds of road pressure and off-road pressure, the road pressure is slightly higher than the off-road pressure) The tire has a small ground surface and low rolling resistance, which can give full play to its high-speed performance; and when driving with off-road air pressure in poor road conditions or no road, the tire has a large ground contact surface, which can improve the tire’s passing performance on soft roads.In addition, when the tire is running on a soft road with ultra-low air pressure, most of the sidewalls above the horizontal axis have been in contact with the ground, and the shoulders are prone to stress concentration areas. Pressing on the rim can easily damage the sidewall.Therefore, in order to reduce the excessive concentration of stress at the shoulders and make the sidewall contact part and the crown of the tire smooth and excessive, the shoulder adopts a large arc design; the radius of the sidewall curve below the horizontal axis is appropriately larger to strengthen the upper end of the rim rim The support of the sidewall (see).
2 The design of the tire pattern. Military off-road tires have always used a “herringbone” pattern in the past.
The grooves of this pattern are deep and wide, and the area of the pattern block occupies the tire side of the running surface. The design indication: Design; The lower sidewall curve design with supporting performance has a small proportion of net product, and the mountain cross-country and climbing performance are more prominent, but not It is good for vehicles to drive at ultra-low air pressure on soft ground roads and high-speed driving on good roads.In addition, the “herringbone” pattern tires have higher rolling noise and rolling resistance, high fuel consumption, poor wear resistance, riding comfort and handling stability, and the “herringbone” pattern is a directional pattern. Need to recognize the direction, which brings inconvenience to the replacement of tires in wartime.Therefore, the “undirected block” pattern with better overall performance is more suitable for the performance requirements of current military off-road vehicles than the “herringbone” pattern.
The depth is shallow and mainly longitudinal grooves, the width of the transverse grooves is small, which can reduce the creep and heat generation of the blocks, reduce the tire noise, vibration and hysteresis loss, and improve the high-speed running performance, riding comfort and handling of the tires stability.The pattern on the shoulder part is dominated by transverse grooves, which are wide and deep, so that when driving off-road, the tire can have a good grip on the ground, and it is conducive to the drainage, heat dissipation and self-cleaning of the pattern; at the same time, The entire row of pattern blocks are staggered on the left and right or the length of adjacent rows of pattern blocks are alternated (see) to make the pattern on the shoulder part form a larger uneven surface, which can increase the tire’s grip on the ground and make up for the blocky pattern. The “herringbone” pattern has the defects of poor off-road and climbability.
The layout of the pattern at the shoulder part is shown a? Adjacent rows of pattern blocks are alternately long and short; b? The entire row of pattern blocks are staggered to the left and right. kind.The carcass of all-steel radial tires has only one layer of steel cord, which has low rolling heat generation and is suitable for high-speed driving on good roads. However, when driving on poor roads or no roads, its thin sidewalls are easily damaged to the steel cord of the carcass. As a result, the steel cord is separated from the carcass rubber, and even rusts and breaks.In addition, all-steel radial tires have poor air-conditioning performance and are not suitable for ultra-low air pressure (below 3kPa).
The carcass of the semi-steel radial tire is made of multi-layer high-strength fiber cords. The sidewalls are relatively solid and have good resistance to hook and hang damage. Even if the outer carcass cord is injured, the inner carcass cord will still function. Worry about rusting of the cord, which is particularly important when driving on a road without roads on the battlefield or when driving on a soft ground (swamp or desert) with ultra-low air pressure.At the same time, the bending resistance and fatigue resistance of fiber cords are much higher than that of steel cords, which is also an important factor in the ability of tires to run at ultra-low air pressure.Therefore, the adaptability of semi-steel radial tires to various road conditions is more suitable for the requirements of military off-road vehicles.
At present, the carcass frame materials used in semi-steel radial tires mainly include modified nylon and polyester cords.Modified nylon cord has low heat generation, good fatigue resistance, high strength, but poor dimensional stability; polyester cord has greater heat generation, poor fatigue resistance than nylon cord, and good dimensional stability, but the carcass It is not suitable to use the curtain with more than 3 layers.
The performance comparison results of modified nylon and DSP polyester cords used on 12.5R20 military off-road radial tires are shown in Table 1. From Table 1, it can be seen that for large-size military off-road radial tires that are adapted to ultra-low pressure driving, use modified cross-country radial tires. Sex nylon cord is more suitable as the carcass frame material.
Giant construction machinery tires work in the mining area, the use conditions are very harsh, most of the tires are damaged by the puncture of the ore, and the tires have a very short service life, causing great economic losses.According to the unique cutting resistance and puncture resistance of aramid, the aramid cord is used as the buffer layer of the construction machinery tire to protect the carcass.For example, 18.00-3332PR aramid buffer tires have good puncture resistance, and their service life is 65% longer than that of the same specification nylon buffer tires, and 18% longer than aramid-nylon composite buffer tires. Use of aramid buffer tires for construction machinery tires The increase in life can reduce the cost, reduce the number of tire changes, and improve the efficiency of use, which has high technical and economic value.
5 Conclusion Aramid fiber has high breaking strength, high modulus, high temperature resistance and unique cutting resistance.
Aramid cord has high dynamic modulus, good elasticity and low hysteresis loss rate, but its fatigue resistance is slightly worse.
Aramid radial tires have good high-speed performance, low quality, and low rolling resistance. Aramid buffer layer construction machinery tires have outstanding puncture resistance, high mileage, and significant social and economic benefits.
**Conclusion of Paper 5 of the National Technical Seminar on Fabrics and Framework Materials for the Rubber Industry In the design of military off-road radial tires, full consideration should be given to the particularity of military off-road tires, and to ensure the main characteristics of the tires 71994-2015ChinaAcademic (continued from page 475) ) Cylinder, finger-shaped forward wrap ※ The capsule turn-up device completes the wrap ring; the second-stage molding adopts a radial condensing outer card type with a capsule head.The tire crown rubber is a compound extrusion of two double rubber types on the upper and lower sides, so that the composite crown rubber has good abrasion resistance and low heat generation, ensuring the high-speed running performance of the tire.
If possible, other performances should be taken into account, especially the use of tubeless radial tires, bullet-proof radial tires, and central inflation and deflation systems. The design of the tire (the form of the rim, the fit of the tire and the rim) is proposed more ,higher requirement.This requires designers to learn more about the performance and use characteristics of military vehicles to provide a reliable basis for tire design.The continuous emergence of new tire technologies, new materials, new processes and new equipment has provided a broad space for the design and production of higher performance and better military tires.
Collection date: G02-030
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Link to this article：Structural design of large-size, high-speed, and ultra-low pressure military off-road radial tires Li Bin
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