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Preload control. Amount of the no-load tension in the bolted joint ( preload) 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] torque-controlled tightening ...
The most common usage is to describe the load applied to a fastener as a result of its being installed, i.e., before any external loads are applied (e.g., tightening the nut on a bolt). Preload in such cases is important for several reasons. First, a tightened bolt experiences only a small fraction of any external load that will be applied ...
The applied torque causes the bolt to "climb" the thread causing a tensioning of the bolt and an equivalent compression in the components being fastened by the bolt. The preload developed in a bolt is due to the applied torque and is a function of the bolt diameter, the geometry of the threads, and the coefficients of friction that exist in the ...
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.
Rockwell scale. The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load). [1] There are different scales, denoted by a single letter, that use different loads or ...
Strength of materials. The field of strength of materials (also called mechanics of materials) typically refers to various methods of calculating the stresses and strains in structural members, such as beams, columns, and shafts. The methods employed to predict the response of a structure under loading and its susceptibility to various failure ...
Junker test. A Junker test is a mechanical test to determine the point at which a bolted joint loses its preload when subjected to shear loading caused by transverse vibration. Design engineers apply the Junker test to determine the point at which fastener securing elements – such as lock nuts, wedges and lock washers – fail when subjected ...
The bolt was qualified to a preload (F p*) of 19,300 lbf (85,900 N), actuated by torque (τ) from an actuator (3) having a maximum sustained output of 1,600 lb⋅in (180,000 mN⋅m). [105] The effective preload can change (F cte ) after berthing by the difference between coefficients of thermal expansion of bolts and flanges.