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Kinematics and Mechanisms 2008 Part 7

Tham khảo tài liệu 'kinematics and mechanisms 2008 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Pennock G. R. Machine Elements The Engineering Handbook. Ed. Richard C. Dorf Boca Raton CRC Press LLC 2000 1998 by CRC PRESS LLC 22 Machine Elements 22.1 Threaded Fasteners 22.2 Clutches and Brakes Rim-Type Clutches and Brakes Axial-Type Clutches and Brakes Disk Clutches and Brakes Cone Clutches and Brakes Positive-Contact Clutches Gordon R. Pennock Purdue University Section 22.1 presents a discussion of threaded fasteners namely the nut and bolt the machine screw the cap screw and the stud. Equations are presented for the spring stiffness of the portion of a bolt or a cap screw within the clamped zone which generally consists of the unthreaded shank portion and the threaded portion. Equations for the resultant bolt load and the resultant load on the members are also included in the discussion. The section concludes with a relation that provides an estimate of the torque that is required to produce a given preload. Section 22.2 presents a discussion of clutches and brakes and the important features of these machine elements. Various types of frictional-contact clutches and brakes are included in the discussion namely the radial axial disk and cone types. Information on positive-contact clutches and brakes is also provided. The section includes energy considerations equations for the temperature-rise and the characteristics of a friction material. 22.1 Threaded Fasteners The bolted joint with hardened steel washers is a common solution when a connection is required that can be easily disassembled without destructive methods and is strong enough to resist external tensile loads and shear loads. The clamping load which is obtained by twisting the nut until the bolt is close to the elastic limit stretches or elongates the bolt. This bolt tension will remain as the clamping force or preload providing the nut does not loosen. The preload induces compression in the members which are clamped together and exists in the connection after the nut has been properly tightened .