The application in the automobile is very extensive, the reliability of the screw connection mainly depends on the axial preload of the bolts, and the friction coefficient between the thread pairs plays a key role in the size of the assembly torque, and the factors that influence the friction coefficient of the fastener are more in the thread connection. Mainly from the gasket hardness, lubrication conditions, assembly technology, matching nut surface Treatment 4 aspects of the impact of the friction coefficient of fasteners.
Taking a bolt group of light duty truck as the research object, the advantages of twisting force thread connection because of its strong bearing capacity, good interchangeability, detachable moment distribution, change of axial preload and so on are widely used in modern automobile manufacture, and the friction coefficient and bearing of screw thread are studied in detail.
Because of its strong bearing capacity, good interchangeability and disassembly, threaded connection has been widely used in modern production and has important influence on the quality and safety of the whole machine. The thread connection relies on the friction transfer load between the threaded pair and the connected parts, and the friction force is directly related to the axial preload. If the axial preload is too large or too small, it will affect the thread connection negatively. The axial preload force is too small, the thread connection carrying capacity and the loose-proof performance are not up to the design requirements; The axial preload force is too large, the stress value of the thread contact surface is large, which leads to the mechanical damage such as thread deformation and slip buckle, and reduces the reliability of thread connection. Therefore, in order to ensure that the threaded connection satisfies the practical work need, the reasonable axial preload range must be determined.
At present, when the thread connection design, because the GB, the row standard does not have to the thread fastener's friction performance to make the specific request, usually the method is based on empirical formula, empirical data to calculate torsional torsion, when the threaded fasteners and connected parts of the surface state changes, will cause the axial preload force too large or too small, resulting in the thread connection fracture, Loose and other quality problems. The total torque force required in the fastening process of threaded connections is the twist of the torsional force needed to overcome the friction between the screw pairs and the torsion of the torsional force that overcomes the friction of the supporting surface.
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