Mechanical welding

Mechanical welding is very desirable for a few reasons. But first of all let me explain what is mechanical welding. It refers to the joining process in which forces are created between interlocking surfaces to hold the components together. There is no heating required unlike fusion welding and solid state fusion. Besides it is a cheap joining process because no additional heating and shielding etc are needed like in arc welding. What you might need includes the fasteners and tools. Besides, the process is simple and no extensive training or experience is required prior to working. A great example is that users all around the world can easily unscrew the screws in their cpu casing.

Basically there are 2 types of mechanical welding, namely mechanical fastener and integral mechanical attachment. The former refers to an additional device which is used to faster up the object, while the latter is usually a pre-designed structure which hold the object using mechanical principle. A good example for mechanical fastener is a bolt and nut combination. While for integral mechanical attachment, you can think off the snap fit design in your mobile phone, either the casing or the battery cover in which no additional device is required. This improve its beauty and make it very user friendly. However care must be taken when dealing with it because inappropriate stress or load might break it off. Also frequent dis-assembly might loosen the structure due to high friction. In case you are using an additional device to hold your object, you have to pre-drill a hole to fit the device. Drilling also incur stress concentration at the surrounding and residual stress might build up around the hole and thus affect the mechanical structures and properties. Also when the item is heavily used (e.g. in a rocking chair) the nut might drop off and poses danger to the user as well. You usually will need additional tool to assemble or disassemble the device, unlike integral mechanical attachment you can do it without additional tooling. But this mechanical fastener usually could create a higher clamping force and sustain higher loads. So there are pros and cons like a two-edged knife, you have to choose the most appropriate welding mechanism for the application. You might need to calculate the relative stress the device can hold, and the lowest stress is usually the one that causes failure in the joints.