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ASTM International has formulated and established a common definition for the technical aspect of the galling phenomenon in the ASTM G40 standard: "Galling is a form of surface damage arising between sliding solids, distinguished by microscopic, usually localized, roughening and creation of protrusions (e.g., lumps) above the original surface". [5]
A bolted joint is one of the most common elements in construction and machine design. It consists of a male threaded fastener (e. g., a bolt) that captures and joins other parts, secured with a matching female screw thread. There are two main types of bolted joint designs: tension joints and shear joints.
Fretting examples include wear of drive splines on driveshafts, wheels at the lug bolt interface, and cylinder head gaskets subject to differentials in thermal expansion coefficients. There is currently a focus on fretting research in the aerospace industry. [ 2 ]
Slip-critical joint, from structural engineering, is a type of bolted structural steel connection which relies on friction between the two connected elements rather than bolt shear or bolt bearing to join two structural elements.
This allows the broadly defined notions of galling, fretting, stiction and adhesion to overlap in some instances. For example, it is possible for a joint to be the result of both cold (or "vacuum") welding and galling (or fretting or impact). Galling and cold welding, therefore, are not mutually exclusive.
In British terminology, a cap screw is a bolt that has threads all the way to the head. Bolts are often used to make a bolted joint . This is a combination of the nut applying an axial clamping force and also the shank of the bolt acting as a dowel , pinning the joint against sideways shear forces .
Multi-jackbolt tensioners (MJTs), registered under the trademark Superbolt or Supernut, are designed to decrease the torque required to tighten large bolted joints. One of the major problems associated with traditional bolt tightening methods is as the diameter of the bolt increases, the amount of torque required to tighten it increases in the third power of the diameter. [1]
In bolted joints with particularly short grip lengths, the loss of preload due to embedment can be especially significant, causing complete loss of preload. Therefore, embedment can lead directly to loosening of a fastener joint and subsequent fatigue failure. In bolted joints, most of the embedment occurs during torquing.