Design of Machine Elements

Abstract

Machine elements are important components that allow for the running of machinery. These include a range of components broadly categorized as “universal elements” such as springs, bearings, chains, gears, pins, belts, bolts and keys, and “special elements” such as turbine blades, aircraft propellers and crankshafts. These components are integral building blocks for most types of machinery. Among the Machine Elements, gears are the most widely used for various purposes within engineering due to their myriad uses and ease of production. Gears come in different shapes and sizes that fall into four general categories “spur”, “helical”, “bevel” and “worm”. Machine Element is a broad topic, so focus was given to a single type of machine element, that is gears, as a representative of the machine elements. Here too though, gears come in a variety of forms as such focus was given to a single type of gear known as a Planetary Gear to represent the gears and as such represent Machine Elements. The objective of the thesis is to review and analyse the relevant literature on the design of Machine Elements, by focusing on gears as representatives of Machine Elements, their design principles, and design methods. Then choose a single gear type and use computer-aided design (CAD) software to model and simulate the performance of the designed chosen gear under various operating conditions and loads. During the CAD process, a Planetary gear was designed consisting of Ring, Carrier, Sun and Planet; with the chosen material for all the gears being Gray Cast Iron. The assembled Planetary gear was put through two contact analyses (first between the Ring gear and a single Planet gear and the second between the Sun gear and a single Planet gear) and a torque simulation between a Planet gear and the Ring gear. The Contact analyses and the torque simulation showed four results each; Stress (MPa), Displacement (mm), Strain and Factor of Safety [FOS]. The torque simulation was done via a series of torques ranging from 1 Nm to 60 Nm to get a series of results. The first contact analysis results (Ring-Planet gear) showed a max stress (σ) of 128 MPA between the contacting teeth, a max displacement (δ) of 0,21 mm, a max strain (ε) of 0,0013 and a minimum FOS of 1,9. The second contact analysis showed σmax of 126 MPa, δmax of 0,039mm, εmax of 0,00175 and a min FOS of 1,6. The torque simulation results showed a series of results depending on the torque applied; for the abstract, the results for the max torque of 60 Nm shall be given; that being a σmax of 169,1 MPa, δmax of 0,004mm, εmax of 0,0027 and a min FOS of 1,16. The methodology detailed the steps taken in modelling and simulating a chosen Machine Element while the results conveyed an example of a positive result from a hypothetical Planetary gear as a form of Machine Element.