Budynas-Nisbett:Shigley's I.Basics 1.Introduction to T©The McGraw-Hill Mechanical Engineering Mechanical Engineering Companies,2008 Design,Eighth Edition Design Mechanical Engineering Desigr Design Considerations Sometimes the strength required of an element in a system is an important factor in the determination of the geometry and the dimensions of the element.In such a situation we say that strength is an important design consideration.When we use the expression design consideration,we are referring to some characteristic that influences the design of the element or,perhaps,the entire system.Usually quite a number of such charac- teristics must be considered and prioritized in a given design situation.Many of the important ones are as follows(not necessarily in order of importance): 1 Functionality 14 Noise 2 Strength/stress 15 Styling 3 Distortion/deflection/stiffness 16 Shape 4 Wear Size 5 Corrosion 18 Control 6 Safety 19 Thermal properties 7 Reliability 20 Surface 8 Manufacturability 21 Lubrication 9 Utility 22 Marketability 10 Cost 23 Maintenance 11 Friction 24 Volume 12 Weight 25 Liability 13 Life 26 Remanufacturing/resource recovery Some of these characteristics have to do directly with the dimensions,the material,the processing.and the joining of the elements of the system.Several characteristics may be interrelated,which affects the configuration of the total system. 1-4 Design Tools and Resources Today,the engineer has a great variety of tools and resources available to assist in the solution of design problems.Inexpensive microcomputers and robust computer soft- ware packages provide tools of immense capability for the design,analysis,and simu- lation of mechanical components.In addition to these tools,the engineer always needs technical information,either in the form of basic science/engineering behavior or the characteristics of specific off-the-shelf components.Here,the resources can range from science/engineering textbooks to manufacturers'brochures or catalogs.Here too,the computer can play a major role in gathering information. Computational Tools Computer-aided design(CAD)software allows the development of three-dimensional (3-D)designs from which conventional two-dimensional orthographic views with auto- matic dimensioning can be produced.Manufacturing tool paths can be generated from the 3-D models,and in some cases,parts can be created directly from a 3-D database by using a rapid prototyping and manufacturing method(stereolithography)paperless manufac- turing!Another advantage of a 3-D database is that it allows rapid and accurate calcula- tions of mass properties such as mass,location of the center of gravity,and mass moments of inertia.Other geometric properties such as areas and distances between points are likewise easily obtained.There are a great many CAD software packages available such An excellent and comprehensive discussion of the process of"athering information"can be found in Chap.4,George E.Dieter,Engineering Design,A Materials and Processing Approach.3rd ed.. McGraw-Hill,New York,2000.Budynas−Nisbett: Shigley’s Mechanical Engineering Design, Eighth Edition I. Basics 1. Introduction to Mechanical Engineering Design 14 © The McGraw−Hill Companies, 2008 8 Mechanical Engineering Design Design Considerations Sometimes the strength required of an element in a system is an important factor in the determination of the geometry and the dimensions of the element. In such a situation we say that strength is an important design consideration. When we use the expression design consideration, we are referring to some characteristic that influences the design of the element or, perhaps, the entire system. Usually quite a number of such charac￾teristics must be considered and prioritized in a given design situation. Many of the important ones are as follows (not necessarily in order of importance): 1 Functionality 14 Noise 2 Strength/stress 15 Styling 3 Distortion/deflection/stiffness 16 Shape 4 Wear 17 Size 5 Corrosion 18 Control 6 Safety 19 Thermal properties 7 Reliability 20 Surface 8 Manufacturability 21 Lubrication 9 Utility 22 Marketability 10 Cost 23 Maintenance 11 Friction 24 Volume 12 Weight 25 Liability 13 Life 26 Remanufacturing/resource recovery Some of these characteristics have to do directly with the dimensions, the material, the processing, and the joining of the elements of the system. Several characteristics may be interrelated, which affects the configuration of the total system. 1–4 Design Tools and Resources Today, the engineer has a great variety of tools and resources available to assist in the solution of design problems. Inexpensive microcomputers and robust computer soft￾ware packages provide tools of immense capability for the design, analysis, and simu￾lation of mechanical components. In addition to these tools, the engineer always needs technical information, either in the form of basic science/engineering behavior or the characteristics of specific off-the-shelf components. Here, the resources can range from science/engineering textbooks to manufacturers’ brochures or catalogs. Here too, the computer can play a major role in gathering information.2 Computational Tools Computer-aided design (CAD) software allows the development of three-dimensional (3-D) designs from which conventional two-dimensional orthographic views with auto￾matic dimensioning can be produced. Manufacturing tool paths can be generated from the 3-D models, and in some cases, parts can be created directly from a 3-D database by using a rapid prototyping and manufacturing method (stereolithography)—paperless manufac￾turing! Another advantage of a 3-D database is that it allows rapid and accurate calcula￾tions of mass properties such as mass, location of the center of gravity, and mass moments of inertia. Other geometric properties such as areas and distances between points are likewise easily obtained. There are a great many CAD software packages available such 2 An excellent and comprehensive discussion of the process of “gathering information” can be found in Chap. 4, George E. Dieter, Engineering Design, A Materials and Processing Approach, 3rd ed., McGraw-Hill, New York, 2000