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Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Mechanical Engineering Design, 2022
The sum of all loads and normal forces acting on the entire thread surface in contact are denoted by W and N, respectively. To lift or raise the load, a tangential force Q acts to the right, and the friction force fN acts to oppose the motion (Figure 15.7). The quantity f represents the coefficient of sliding friction between the nut and screw or the coefficient of thread friction. The thread angle increases the frictional force by the wedging action of the threads. The conditions of equilibrium of the horizontal and vertical forces give ΣFh=0:Q−N(fcosλ+cosαnsinλ)=0ΣFυ=0:W+N(fsinλ−cosαncosλ)=0
Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, Mechanical Engineering Design, 2020
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
For fasteners, the standard geometry of screw thread shown in Figure 15.3 is used. This is essentially the same for both the Unified National Standard (UNS), or the so-called unified, and International Standards Organization (ISO) threads. The UNS (inch series) and ISO (metric series) threads are not interchangeable. In both systems, the thread angle is 60°, and the crests and roots of the thread may be either flat (as depicted in the figure) or rounded. The major diameter d and root (minor) diameter dr refer to the largest and smallest diameters, respectively. The diameter of an imaginary cylinder, coaxial with the screw, intersecting the thread at the height that makes width of thread equal to the width of space, is called the pitch diameter dp.
Power Screws, Fasteners, and Connections
Published in Ansel C. Ugural, Youngjin Chung, Errol A. Ugural, MECHANICAL DESIGN of Machine Components, 2018
Ansel C. Ugural, Youngjin Chung, Errol A. Ugural
The sum of all loads and normal forces acting on the entire thread surface in contact are denoted by W and N, respectively. To lift or raise the load, a tangential force Q acts to the right, and the friction force fN acts to oppose the motion (Figure 15.7). The quantity f represents the coefficient of sliding friction between the nut and screw or the coefficient of thread friction. The thread angle increases the frictional force by the wedging action of the threads. The conditions of equilibrium of the horizontal and vertical forces give () ∑Fh =0:Q−N(fcosλ+cosαnsinλ) =0∑Fv =0:W+N(fsinλ−cosαncosλ) =0
Design optimization of implant geometrical characteristics enhancing primary stability using FEA of stress distribution around dental prosthesis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Sameh Elleuch, Hanen Jrad, Amir Kessentini, Mondher Wali, Fakhreddine Dammak
In this study, geometrical characteristics of the implant, presented in form of screw having length (L), major diameter (D) and implant thread pitch (p), as illustrated in Figure 2. The height and the width of the implant thread are, respectively, 0.3 and 0.1 mm. The thread angle is considered 60° according to the following references (Yang and Xiang 2007; Kaman and Celik 2013; Sazesh et al. 2017).