What actually makes a high quality fastener?
There are certain criteria that reveal whether fasteners are of high quality. At the top of the list are stability and durability. Basically, all the conceivable loads that come into play here can be categorised as one of two forces – displacement force and extraction force.
Extraction Force
Extraction force (sometimes called “groove load-bearing capacity”) refers, for example, to an attempt to pull apart two connected profiles and destroying the fastener or pulling it out of the groove in the process.
Displacement Force
In contrast to extraction force, displacement force refers to the force required to move a profile along a profile groove – provided everything has been screwed into place beforehand as per the assembly specifications.
Testing
To find out exactly how much force can be accomodated, item uses a standardised test procedure, during which the fastener is subject to force until it reaches its point of failure. But how can you identify the precise point at which the connection point fails? After all, it’s impossible to see this kind of deformation with the naked eye. By conducting a series of in-depth tests, item’s team has identified the transition point, when elastic deformation becomes plastic deformation, for every kind of connection point. The increasing force that has to be applied is recorded during the experiment to determine the load limit of connections. Once the transition point is reached, the test result is documented.
Safety Considerations
Safety factors are incorporated into the final load recommendations to ensure that additional, unpredictable influences such as extreme temperature fluctuations, vibrations and sudden load peaks are taken into account. This ensures that the permissable load specifications are reliable and can be used in structural design.