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The screw is a mechanism that converts rotational motion to linear motion, and a torque (rotational force) to a linear force. [1] It is one of the six classical simple machines . The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside.
The force and torque vectors that arise in applying Newton's laws to a rigid body can be assembled into a screw called a wrench. A force has a point of application and a line of action, therefore it defines the Plücker coordinates of a line in space and has zero pitch. A torque, on the other hand, is a pure moment that is not bound to a line ...
The curve representing a clamped parts-to-bolt stiffness ratio of 0.01 shows that when the relative stiffness of the clamped parts is very low, almost all of the load is transferred to the bolt, down to the point where a compressive load equals the preload, and separation at the bolt head occurs, reducing the force in the bolt to zero.
The mechanical advantage of a screw thread depends on its lead, which is the linear distance the screw travels in one revolution. [1] In most applications, the lead of a screw thread is chosen so that friction is sufficient to prevent linear motion being converted to rotary, that is so the screw does not slip even when linear force is applied ...
A force arrow should lie along the line of force, but where along the line is irrelevant. A force on an extended rigid body is a sliding vector. non-rigid extended. The point of application of a force becomes crucial and has to be indicated on the diagram. A force on a non-rigid body is a bound vector. Some use the tail of the arrow to indicate ...
A machine screw or bolt is usually a smaller fastener (less than 1 ⁄ 4 inch (6.35 mm) in diameter) threaded the entire length of its shank that usually has a recessed drive type (slotted, Phillips, etc.), usually intended to screw into a pre-formed thread, either a nut or a threaded (tapped) hole, unlike a wood or self-tapping screw. Machine ...
Bolts are correctly torqued to maintain the friction. The shear force only becomes relevant when the bolts are not torqued. A bolt with property class 12.9 has a tensile strength of 1200 MPa (1 MPa = 1 N/mm 2) or 1.2 kN/mm 2 and the yield strength is 0.90 times tensile strength, 1080 MPa in this case.
These bolts, usually tension control bolts or compressible washer tension indicating type bolts, are tensioned to a minimum required amount to generate large enough friction forces between the faying surfaces such that the shear (or tension) load is transferred by the structural members and not by the bolts (in shear) and the connection plates ...