Material fatigue-the enemy of automobile safety[汽车修理知识]

CarThere are hundreds of causes of failures, one of which is beyond the control of the user. This is the failure of structural parts caused by material fatigue. The thick and strong steel will be "fatigue"? It is true.
What is the fatigue of metal materials? Parts can be deformed or broken when subjected to super strong forces, just like fractures can occur when the human body is attacked, but this is not fatigue damage. Fatigue failure refers to the performance change of a material under long-term repeated stress under normal working conditions. The magnitude of these stresses does not exceed the range that the material can withstand, but long-term repeated actions will cause material fatigue. The fatigue failure of materials is not detected at the beginning, it is a slow development process.For example, an engineCrankshaftSmall fatigue cracks can be generated when the operation time is not too long. These invisible cracks will continue to expand until one dayCrankshaftSuddenly broke. It's like a person falls ill for a while due to the fatigue accumulated by long-term work.
Mankind has paid a high price to gain the knowledge of material fatigue. After the Second World War, the British De Havilland Aircraft Company designed and manufactured the Comet civil jet aircraft. After a year of use, a Comet passenger aircraft disintegrated in mid-air shortly after taking off from Kolkata Airport in India on May 2, 1953. ; On January 10, 1954, another Comet exploded over the Mediterranean Sea; less than three months later, another Comet exploded in the air after taking off from Rome. In order to find the cause of the accident, engineers from the Royal Institute of Aeronautics and Astronautics conducted a lot of research work and finally confirmed that the culprit was the fatigue cracks in the cockpit.
Modern mechanical design has widely adopted the "fatigue life" method, and the fatigue problem of materials has been fully considered in the design stage. However, just as the fatigue of the human body varies from person to person, the fatigue of a machine varies from machine to machine. For the same type of car, the fatigue failure situation may be very different. Some have reached the end of life, and the degree of fatigue is not too serious; some are still within the life span, but fatigue damage has occurred. Different ways of using will also lead to different fatigue states of the machine. For example, if a Fukang car of the same type is used as a taxi or as a private car, there will be a major difference in the operating state of the vehicle in a few years. In order to avoid fatigue damage, vehicles must be inspected strictly in accordance with various maintenance and repair deadlines in order to discover potential hazards in time.

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