Lock nuts are commonly used connectors, and their national standards and specifications have detailed regulations. The influencing factors of lock nuts mainly include material strain hardening, Low-cycle fatigue, friction coefficient, manufacturing and assembly, and closing value.
Lock nuts are generally made of alloy steel, which belongs to the cyclic strain hardening material. During the cyclic loading process, the strain hardening of the threaded piece will lead to an increase in its elastic recovery force, thereby increasing the screwing out torque.
During use, the lock nut needs to bear a constant reciprocating load, which is likely to lead to Low-cycle fatigue of the threaded piece, reducing the pressure of the threaded piece and the screwing out torque.
The friction coefficient is one of the important factors affecting the maximum tightening torque of a locking nut. Under the cyclic friction effect, the rough positions and edges of the threaded piece are smoothed and the friction coefficient decreases, thereby reducing the maximum tightening torque of the nut.
Manufacturing technology and assembly accuracy also affect the important performance of lock nuts. If there are sharp corners on the edge of the thread or the size fit between the parts is not coordinated, there may be certain fluctuations or fluctuations in the screw-in and screw-out torque, which requires a certain number of running in to obtain more accurate locking nut reuse characteristics.
The closing value refers to the degree to which the threaded piece in the locking nut opens, and its change will have an impact on the reuse characteristics of the locking nut. A change in the closing value will increase the deformation of the threaded piece when it opens, exacerbate the strain cyclic hardening phenomenon, and increase the pressure of the threaded piece, showing a trend of increasing the screwing out torque; On the other hand, the larger the closing value, the smaller the total area of the threaded piece, the lower the friction with the bolt, the higher the strain of the threaded piece, and the lower the Low-cycle fatigue performance, which has a tendency to reduce the maximum screw out torque.
Overall, under the combined action of multiple factors, it is difficult to predict the maximum tightening torque of the lock nut as it changes with the number of repeated uses, and it can only be observed and verified through experiments. In practical applications, it is necessary to select appropriate locking nuts based on specific usage situations, and regularly inspect and replace them to ensure their normal performance and achieve the expected results.
