Effects Of Temperature And Vibration On Rail Nuts And Fasteners

Since their invention, bolts, nuts, and fasteners have become a reliable tool for many engineers who want to strongly hold components together. And one of their advantages over other adjoining alternatives (e.g. Welded joints) is that they can be easily dismantled.

All sort of nuts -- such as rail nuts and Philidas nuts -- is always used together with a bolt. But while these two, together with fasteners, make up a formidable tandem, they are not exempted to eventual, unintentional loosening up. And the consequences of loose nuts and bolts range from hampering production at a certain factory to serving as a safety hazard to the workers themselves.

There are several reasons behind this phenomenon. But two of the most common causes are temperature and vibration.

Temperature

Change in temperature leaves a significant impact on the properties of many materials -- including bolts, rail nuts, Philidas nuts, and fasteners. They can expand or contract swiftly if they are exposed to extreme temperature differences. This can ultimately lead to the loosening of the bolt.

Be careful to choose the right material when using bolts, nuts, and fasteners to hold things together. If they will be exposed to environments with high heat, engineers are taught to not use anything made of plastic or those that are non-ferrous (don’t contain iron). If inappropriate materials will be used, they can get oxidised and cause them to corrode, break down and fail.

For temperatures up to 450° F, low steel and medium carbon alloys will work great; stainless steel for 450° - 900° F; superalloys for 900° - 1,200° F; and nickel-cobalt allows for up 1,200° - 1,600° F.

If your bolts, nuts, and fasteners will be subject to cold environments, inappropriately-used type of materials will eventually get brittle because the low temperature will affect their toughness and ductility.

Nickel-rich grades can withstand temperature above -100° F; steel for -100° to -300° F. Non-metallics and super alloys can also work under cold-temperature settings.

Vibration

Remember the dismantling advantage of bolts, fasteners, and nuts like Philidas nuts and rail nuts? This can also be the very reason for their failure.

Vibrations refer to the oscillations caused by a series of sounds and/or movements. Since decades ago, these vibrations have posed hazards to different structures built by engineers.

When exposed to these, impermanent fastening solutions like bolts and nuts can move in parallel with the joint they are attached to. Prolonged exposure to vibrations can further work against the friction binding them, eventually causing them to loosen over time.

One of the most popular tests regarding the effect of vibrations on fasteners, bolts, and nuts is the Junker Test. Developed by German engineer Gerhard Junker, this test involves subjecting bolts to a so-called Junker machine that gives out strong lateral vibrations. Nowadays, many facilities use this machine to ensure the strength of the fastening solutions employed in their structures.

To counter the consequences of vibration, engineers have devised tools like thread lockers, locking nuts, trilobular threads, and underhead serration among others.