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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.
The Research Council on Structural Connections (RCSC) is a research organization focused on bolted structural connections. Their technical standard on this subject is cited in the US steel design code. [1] Prior to 1980, the organization was known as the Research Council on Riveted and Bolted Structural Joints (RCRBSJ).
A bolted joint is a mechanical joint which is the most popular choice for connecting two members together. It is easy to design and easy to procure parts for, making it a very popular design choice for many applications. Advantage: Joints are easily assembled/ disassembled by using a torque wrench or other fastener tooling. [7]
In critical fastener joints, embedment can mean loss of preload. Flattening of a surface allows the strain of a screw to relax, which in turn correlates with a loss in tension and thus preload. In bolted joints with particularly short grip lengths, the loss of preload due to embedment can be especially significant, causing complete loss of preload.
Amount of the no-load tension in the bolted joint greatly affects the reliability of the joint. Multiple techniques exist for preload control to ensure that the tension in the bolt is close to the one specified in the design (some bolt-to-bolt statistical variations are inevitable): [1]
The benefit of spring lock washers lies in the trapezoidal shape of the washer. When compressed to loads near the proof strength of the bolt, it will twist and flatten. This reduces the spring rate of the bolted joint which allows it to maintain more force under the same vibration levels. This prevents loosening. [12]
Due to vibration, temperature changes, and other factors such as spiral wound gasket stress relaxation, the bolt tension will gradually decrease, resulting in loss of torque, causing a leak. In general longer bolts and smaller diameters of bolt are better at preventing the loss of torque. A long thin bolt is an effective way to prevent torque loss.
Bolted joint in vertical section Screw joint. The distinction between a bolt and a screw is poorly defined. The academic distinction, per Machinery's Handbook, [3] is in their intended purpose: bolts are designed to pass through an unthreaded hole in a component and be fastened with the aid of a nut.