For most users of the Railway Fastening System, you may know the type of
fastener dynamic torque standards during use, but you do not know some factors
that affect the dynamic torque of the fastener, which will seriously affect the
fastener during use Performance.
Railway Fastening System
Four factors that analyze the dynamic torque of fasteners: Railway Fastening System Manufacturer:
1.Shape of fastener head
With the increase of the diameter of the bearing surface of the head, the friction surface keeps increasing, and the torque required to achieve the same axial preload force also increases. Therefore, under the same conditions, the larger the torque required for the fastener with a large diameter of the friction surface of the head.
2.Friction coefficient of fastener surface
The friction coefficients of fasteners with different surface treatment methods vary widely. However, the surface friction coefficient can be adjusted to the required range by adding a modifier.
In the case of surface plating without friction coefficient modifier, the friction coefficient is about 0.3; when the surface is oily, it is about 0.1;
The surface without a coating is about 0.1; the GM standard is 0.1 ~ 0.16;
Because the surface friction coefficient has a great influence on the axial force generated under the same torque condition, it is necessary to specify the range of surface friction coefficient for important fasteners.
3. The actual cooperation between the threads
In general, there should be clearance fit between the threads. That is, the surface of the bolt is 6h after plating, and the surface of the nut is 6H. However, due to the manufacturing error of the fastener itself and the error of the surface coating thickness, the fastener may actually be an interference fit or a clearance fit. This may cause under-screwing or slipping.
4. Characteristics of Fasteners
The nut of the self-tapping bolt has no thread, and the bolt needs to tap the thread directly on the nut. Therefore, additional torque is required. The thread is coated with thread glue (to prevent loosening or sealing), or the nut is a self-locking nut, which will cause the actual fit between the threads to be an interference fit, so additional torque is required.
Why is the firmware not hard enough?
With the improvement of social needs, the use of fasteners' performance and quality is also continuously improved, but there are still many users who will ask why the hardness of some fasteners is not enough. Defects caused by.
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