Hardware talks to you about the common problems of loosening of screw flat gaskets

'The embankment of a thousand miles was destroyed by an ant's nestScrews are known as the rice of industry. Although they are small, they are by no means insignificant. However, there are many incidents in history that have caused catastrophes due to the neglect of screws. In response to the loosening of screw flat gaskets, technicians have taken various active and effective measures to inject new vitality into the development of screw fasteners. There are many anti-loosening technologies and anti-loosening structures for screw flat gaskets. The specific solutions are as follows . Controlling the pre-tightening force Controlling the installation pre-tightening force is one of the economical and effective measures to prevent the loosening of the screw flat washer. This method uses the self-locking condition of the thread and does not require any changes to the bolt and nut structure. By ensuring proper pre-tightening Force to prevent loosening. For use occasions with particularly high installation control requirements, the direct control method is adopted to measure the pre-tightening force during the installation process and control it. In general, direct control of the installation pre-tightening force requires the use of special devices or mastering special techniques. Difficult to promote. In order to obtain a satisfactory pre-tightening force in an economical way, more methods of indirect measurement and control of the pre-tightening force are adopted, namely the torque control method. The torque control method uses the torque coefficient to convert the pre-tightening force into the assembly torque, using a fixed torque or torque measuring assembly machine or wrench to control the assembly torque, or using the fastener's own structure to ensure the tightening torque (such as torsion-shear bolt connection pair), indirectly To achieve the purpose of controlling the pre-tightening force. In order to achieve the desired purpose, it is required that the torque coefficient of the connecting pair can be accurately measured in advance, and to ensure that the torque coefficient of the same batch of parts has little dispersion. For example, GB/T1231-1991 clearly stipulates that the average value of the torque coefficient of the same batch of connection pairs is 0.110-0.150, and the standard deviation of the torque coefficient should be less than or better than 0.001%. In engineering practice, there are also control methods such as the angle method and the yield point tightening method. Effective torque type fasteners Effective torque type fasteners are based on the structure of ordinary fasteners. The effective torque part is added. Its function is to add a resistance torque that does not change with external force. The effective torque part is mainly added to the nut. On the above, the products that add effective torque to the external thread are relatively rare. All-metal effective torque type lock nuts, one type uses the deformation of the nut body after the thread processing on the nut body is completed, so that the thread is deformed in the axial or radial direction, causing the internal and external threads to locally interfere during assembly to produce effective torque. And the influence of the deformation resistance and geometric accuracy of the blank before deformation, which requires high processing technology, and the effective torque control is difficult; the other is to thin the effective torque part, and close or groove after closing. At present, guo is mainly used in the military industry. More; the third type is to embed metal elastic elements in the nut body. The external threads force the elastic elements to deform during assembly and produce effective torque. This type of nut has higher requirements on the elastic element elasticity and the position of the insert, and sometimes scratches the outside. Threaded surface. Using washers The washers currently used mainly include flat potential rings, spring washers, and elastic washers. The flat washer is mainly used to improve the contact state of the bearing surface to ensure the stability of the friction coefficient of the bearing surface and have a certain effect on the anti-loosening; the spring washer uses its elasticity to generate axial force and improve the elasticity of the connection. The transverse vibration test results show that it is Under this test condition, the anti-loosening effect is poor; the twisted teeth of the elastic washer are flattened by the tightened nut, so that the threaded auxiliary shaft body is compressed, and at the same time partially embedded in the supporting surface, the elasticity is uniform, the anti-loosening effect is better, and it will scratch. Damage the surface of the part. In some special occasions, scratching the surface of the part is exactly what people want. For example, the terminal on the surface painted part can scratch the paint and ensure the conductivity. Direct locking After tightening the nut, use a locking (stop) element to lock the nut and bolt to prevent them from rotating relative to each other. Commonly used is the use of split pins, tandem steel wires and stop washers. Cotter pins are used in conjunction with bolts with holes at the end and slotted nuts to prevent loosening and reliable. Generally, the slotted angle of the nut is 60°. Ensure that the slotted holes are aligned during installation, which is inconvenient to assemble; use low carbon steel wire to penetrate the bolt head or nut In the metal wire hole, several bolts or nuts are connected in series to restrict each other, which is reliable and reliable; the stop washer is stuck on the nut by the plastic deformation of the washer. When disassembling, the washer should be flattened and restored before loosening the nut. Disassembled heavy, dynamic load connections, such as flywheel nuts. Destroy the relationship of the kinematic pair. Use the punch to locally deform the threads of the bolt and nut to deviate from the original tooth profile, so that the part cannot be meshed with the normal thread direction, destroy the kinematic relationship of the original kinematic pair, and form a non-reusable connection, such as disassembly. , It is necessary to use a larger torque to unscrew the nut or destroy it. This method is rarely used at present. Bonding Bonding is to bond the bolts and nuts or the connected parts together to achieve the purpose of preventing loosening. Bonded bolts used for mass production are usually made by applying anaerobic glue to the parts in the fastener manufacturer and drying them to form microcapsules. The surface of the microcapsules is dry and does not have a sticky feeling. The capsule is squeezed and ruptured, the glue overflows, and the bolt and the nut are firmly bonded. As long as sufficient torque is applied during disassembly, under normal circumstances, within a certain period of time, it can be reused a limited number of times. If you want to know the knowledge of other screw flat washers, please add V: