Introduction 机械零件设计英文PPT教案 课件 Design of Machine .ppt

Design of Machine Elements Chapter 1 Introduction The Meaning of Design Engineering Mechanical Engineering Design Machine design “Engineering” is the art of directing the great sources of power in nature for the use and convenience of human beings / utilizing the existing resources and natural law to benefit humanity Engineering is concerned with the conversion of energy from one form to another with the objective of extracting useful work. Mechanical engineering has the more specific objective of designing machinery to this purpose in the most suitable manner possible. Design requires significant creativity, practice, and vision to be done well. Machine design is the fundamental practice in engineering; is the transformation of concepts and ideas into useful machinery. Machine design is the application of science and technology to devise new or improved products for the purpose of satisfying human needs. Design problems are, almost without exception, open-ended problems combining hard science and creativity. Definition of Machine Composition 1) Definition of Machine A machine is a combination of mechanisms and other components that transforms, transmits, or uses energy, load, or motion for a specific purpose.A machine is a combination of components which can transmit power in a controlled manner by converting energy from one form to another and eventually producing useful work. In terms of basic manufacturing unit, a machine is composed by machine elements/components. In terms of the functions of the sub-system of a machine, it is comprised of the source-power, transmission, execution and control/manipulation parts. For the convenience of kinematic or dynamic analysis of a machine, a machine can be decomposed into mechanisms. 3) Classification of Machine Elements Normal load transmitter: sliding bearings, rolling-element bearings Torque tramsmitter: gears, traction drives, chain drives, belt drives, power screws Energy absorber: b