Mechanical Design of Machine Elements and Machines: A Failure Prevention Perspective

Abstract

This new textbook targets the Junior-Senior level sequence in machine design challenging classical machine design texts associated with authors such as Joseph E. Shigley, Robert C. Juvinall, and Merhyle F. Spotts. The author's emphasis on failure prevention includes the selection of a factor of safety as part of the design process. The book is divided into two parts. The first part addresses engineering principles whereas the second part considers design applications. The first part diverges from similar machine design texts by targeting failure prevention as the underlying theme for machine component selection. The many components of failure are introduced early in Chapter 2. These concepts include the classical failure modes; yielding, ductile and brittle failure, fatigue failure, wear, impact, and buckling along with less traditional failure modes such as fretting, creep, and corrosion are presented. Specifically, the fracture mechanics approach to predict fatigue failure is introduced and expanded from classical texts on machine elements to provide a more modern assessment of fatigue life. The second part provides a classical treatment on the design of machine elements such as bearings, springs, fasteners and power screws, gear pairs, brakes and clutches by presenting established

Contact Fatigue Design of Helical Gear by Spur Gear Equivalency

“…Contact fatigue strength is related to surface hardness while bending fatigue strength is related to core hardness [1,2,3,6,7,8,9,11,21]. Many of the AGMA available gear nominal strength data have been developed from tests of actual gear teeth so they better represent reality than general material strength data [4].…”

“…Several potential failure modes in gearing have been identified [8,10], but the two prominent modes are surface fatigue or pitting and bending fatigue [2,11,12]. In this study, we are concerned with pitting.…”

“…The helix may be right-handed or left-handed and its inclination to the axial direction of the gear is called the helix angle. A spur gear may be treated as a helical gear with a zero helix angle [2]. Helical gears can be used to transmit torque and rotational motion between parallel and non-parallel shafts, though the former is more common than the later.…”

“…The flowing force relations may be verified by referring to standard books in machine design [2,3,4,6,7,8]: Fig. 2 shows the common planes often associated with helical gears.…”

Design of Shaft and Bearing System in Eccentric and Nonaligned Gears Mounted on Rotating Shafts

“…4) Other key factors that influence alignment in shafts, in particular, and in rotating machinery, in general, are the speed of the drive train and the maximum deviation at either flexing point or point of power transmission. 5) While there are no published (universal) standards for alignment tolerances (unlike the case for bearings), it is necessary that dimensional tolerances and deviations of machine parts be kept within a certain accuracy to achieve their correct and reliable functioning 7 .…”