Why Do Fasteners Loosen And How Can You Prevent It?

During the course of using fasteners, one of the problems you may end up encountering is finding that the fasteners loosen on their own. This can be gradual or sudden depending on the cause of the problem. Either way, unintended loosening can bring about a number of problems. For instance, if you had used the fasteners to keep an electronic device sealed, the process of self-loosening can have a negative impact on the integrity of the device, and this means that it may end up failing. If the fasteners were used for structural construction, their loosening may also result in failure of the structure as a whole, and it might end up resulting in a collapse of the building.

For this reason, it’s usually a good idea to understand the reasons why this type of failure occurs, so that you can avoid them. Putting in place the measures to reduce the chances of this happening when you are initially putting the fasteners in place is the best policy you can have in this regard. Some of the reasons why they loosen include:
Transverse joint movement
Fasteners are usually used to create joints between two surfaces. When there is too much movement between these surfaces, the area of contact between the fastener and the material may end up being subjected to a lot more tension than it can handle. When it exceeds the friction between the fasteners and the material, loosening will occur. This is particularly so when the movement is repetitive. In order to avoid this, it’s usually necessary to brace the surfaces that are likely to move in order to reduce this. You can also use fasteners such as A325 Structural hex lag bolts or A490 Structural Hex Tap Bolts. In addition to that, it’s also important to make sure that the clamp force on the fastened surfaces is adequate to resist such movement, and that thread locking devices are used as well.

 
Temperature differentials
Differences in temperature between the fastener and the other materials it is holding together can also result in loosening. This is usually due to different expansion between the two materials. For instance, if the fastened object expands faster than the fastener, it could lead to an increase in the size of the hole that the fastener is placed in. Proper material selection is usually all that is needed to ensure that this form of loosening does not occur.
Embedment
When the fastener is being put in place for the first time, there can be loss of preload, which in turn means that the fastener might end up loosening. This can be due to the flattening of the surfaces between the material being fastened and the fastener. This results in loss of friction between the two surfaces, and encourages such loosening.
In summary, loosening is a process that you need to be wary of when you are thinking of using fasteners, particularly in environments that will be subjected to a lot of movement. Careful selection of fastener type and making sure that they are properly placed is often the best way to avoid the problem.