Before the high-speed rail, the sound of “should be a jingle...†when riding a train was an unforgettable experience and memories of many people. Sitting on today's high-speed rail, you will find that the rhythmic "jingle" sound between the wheel and the rail is hard to hear. Some people on the Internet said that this change occurred because there was a gap in the place where the rails were connected, but there is no gap between the rails, so there is no noise in the amount. is this real? First of all, it must be said that the above statement is true! On the previous railway, close observation of the rails will reveal that there will be a little gap between the two rails every 10 meters. Why do you want to leave a little space between the rails? Originally, this was done to solve the problem of thermal expansion and contraction of the rail. If there is no such gap, the rails will be squeezed, twisted and arched by the heat elongation, which will deform the whole railway. When the weather is hot in summer, the length of the rail increases, and the rails without gaps can only bulge upwards, which is obviously not good for driving safety. To avoid this, a gap must be reserved between the rails. How much should the gap between the rails be suitable? For driving safety, the rail joint can not exceed 11mm, which is determined by experiments: every 1 °C of rail temperature will be stretched by 0.011mm per meter rail. In China, on the southern and northern railway lines, the temperature between winter and summer can usually differ by about 80 °C. According to the relationship of solid line expansion, the length of each section of rail is preferably 12.5 m. Tell you an interesting number. The gaps left between the rails from Beijing and Guangzhou used to be 2000m long! There is no gap in the current railroad track, is it to eliminate this "jingle" sound? In fact, the reason for choosing to use seamless rails is because of the high-speed rail. Since the wheels will impact the rails, when the train runs too fast, the gap between the rails will cause the train to derail. When the train has a speed of more than 140 kilometers per hour, it is necessary to use seamless rails. So, how to solve the problem of thermal expansion and contraction of seamless rails? Previously used sleepers and spikes, the pressure is not enough to lock the track, so there needs to be a gap to release the pressure. The seamless rail is to control the temperature deformation of the rail due to thermal expansion and contraction between the two sleepers. The specific method is to use the gusset plate and bolt to smash the rails on the sleepers. Since the fixture is resilient (up and down direction), when the lift from the rail is lifted upwards, the force is transferred to itself by the fixture and the force is finally transmitted to the sleeper by the screw. The rubber pad under the rail has a larger expansion coefficient than the rail, so the bottom of the rail can always be kept in a non-empty state. (Seamless rail seamless rails are welded at the weld to suppress heat expansion and contraction. Each fastener provides 1 ton of force and 100 fasteners at each end. A total of 200 tons of force. ) Of course, the above description is only the overall principle. The details are a combination of many technological advances, such as: Working on the rail steel, selecting the material with small expansion and contraction to make the rail; With high-quality sleepers and fasteners, the pressure is large enough to press the rails against the sleepers and not displace in the direction of the track. All deformations (stresses) are locked in a small piece of rail between the sleepers and do not converge out in a concentrated manner; Advances in welding technology, fully consider the variation range of the local temperature of the rails, select moderate temperature welding seamless rails, press the fasteners, professionally known as locking rail temperature. The stress generated by such positive and negative temperature changes is within the controllable range. The technique of train design and operation, when the wheel travels to the joint of two rails, a part of the wheel tread is pressed on the first rail, and another part of the wheel tread is simultaneously pressed on the second rail, so that two The rails are stressed at the same time, so that the wheels pass smoothly through the joints of the two rails without vibration. In addition to the above factors, some netizens think that because ordinary railways are based on stone and sleepers, the rails are barely exposed on the sleepers, and they are not in contact with the ground. The temperature difference is larger than the ground, and any expansion and contraction is their own. To bear, making it seamless will inevitably cause bulging or breaking. The current high-speed railways are all elevated structures and reinforced concrete materials. The temperature and expansion coefficient of the rails are consistent with the pavement. There is no need to special treatment for the thermal expansion and contraction of the rails. The warming effect caused by the passing of the train is minimal, and it can be completely digested by the aid of the curve and the spring and rubber material. As for the rivets, it only serves to prevent derailment. Finally, Metalworking Xiaobian will give you some tips on seamless rails: 1. The high-speed rail is so long, how is the seamless rail produced? When the seamless rail is just produced, it is also a section. Through the seamless rail welding machine, the two ends of the two rails are heated to 1000 degrees or more, and then the two rails are pressed together. The track thus welded can reach 500 meters in length. The rails that have been welded, polished, and inspected will be transported to the paving site and re-welded to other rails, eventually becoming a seamless track of several hundred kilometers. 2. China has such a large railway from south to north, such a long mileage, such a large coverage area, is this seamless rail technology? In the south of China, its temperature difference is not large all year round, so it is more suitable for laying seamless lines. In the northern part of China, the temperature difference between winter and winter is relatively large. The rail regularly releases its stress and opens all the fasteners. There is no need to release the stress.
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If the high-speed rail is to use a seamless track, how to solve the problem of heat and cold contraction?
The most important thing is: seamless rail is a pure "domestic goods" is China's independent research and development technology!