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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 ...
When a fastener is tightened, a tension preload is develops in the bolt, while an equal compressive preload forms in the clamped parts. This system can be modeled as a spring-like assembly, where the clamped parts experience compressive strain, and the bolt tensile strain. When an external tensile load is applied, it reduces the compressive ...
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 torque applied to the fastener must be determined such that it does not contribute to a service condition where the fastener enters a low-cycle fatigue regime. In general, the use of torque-to-yield fasteners is deprecated except in cases where the materials and structures comprising the entire assembly are certified to be within tolerances ...
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.
fasteners, d 0: diameter of the passthrough hole; α = min{e 1 /3d 0 ; p 1 /3d 0 - 1/4 ; f ub /f u ; 1}, with e 1: end distance from the center of a fastener hole to the adjacent end of the part, measured in the direction of load transfer, p 1: spacing between centers of fasteners in the direction of load transfer,
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.
A Belleville washer, also known as a coned-disc spring, [1] conical spring washer, [2] disc spring, Belleville spring or cupped spring washer, is a conical shell which can be loaded along its axis either statically or dynamically. A Belleville washer is a type of spring shaped like a washer. It is the shape, a cone frustum, that gives the ...