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按一下以編輯母片標題樣式,按一下以編輯母片,第二層,第三層,第四層,第五層,*,/29,大葉大學機械與自動化工程學系,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Introduction to Design,Chapter 1,Mechanical Design,An Integrated Approach,Introduction to DesignChapter,1.2 Engineering Design,Design,The mechanism by which a requirement is converted to a meaningful and functional plan,Engineering Design,The process of applying,science,and e,ngineering,methods to prescribe a component or a system in sufficient detail to permit its realization.,2,1.2 Engineering DesignDesign2,The Principles of Machine Elements in Mechanical Design for a Designer,The,functions,of mechanical components and devices,The,strengths,of mechanical components and devices,The ultimate goal in a mechanical design process is to,size,and,shape,the elements and choose appropriate,materials,and,manufacturing processes,so that the resulting system can be expected to perform its intended function without failure.,3,The Principles of Machine Elem,1.3 The Design Process,Phases of Design,Identification of Need,Real or imagined,Customer requirements,Cost reduction,Efficiency improvement,.,Definition of the Problem,design and performance,requirements,Standards(標準),Codes(法規),4,1.3 The Design ProcessPhases o,Synthesis(合成),In this step,the designer,combines separate parts,to form a complex whole.,Also termed the“,Ideation,and invention phase,.”,Analysis(分析),The product under design,must be analyzed to,determine whether the,performance complies,with the specifications.,5,Synthesis(合成)5,Testing,Prototype evaluation.,Computer prototypes,are often utilized.,Presentation,The designer must be,able to understand the,need and describe a design,graphically,verbally,and in,writing.,6,6,1.4 Design Analysis,To predict the stress or deformation in the component so that it may safely carry the loads that will be imposed on it.,Engineering Modeling,Geometric Model,Rational Design Procedure,Rational procedure:,procedures with firm analytical base,such as tension,compression,fatigue.,Semi-rational or empirical approach,:procedures without firm analytical base,Methods of Analysis,Statics:,The equations of equilibrium must be satisfied.,Deformations:,Stress-strain,force deformation must apply to the behavior of the material.,Geometry:,The conditions of compatibility of deformations must be satisfied.,7,1.4 Design AnalysisTo predict,1.5 Problem Formulation and Computation,Solving Mechanical Component Problems,Definition of the problem by stating the given quantities and appropriate assumptions.,Preliminary design and sketches.,Mathematical models,detailed design analysis,and evaluation.,Computational Tools for Design Problems,MATLAB,MathCAD,CAD software packages,FEA,BEA software packages,8,1.5 Problem Formulation and Co,1.6 Factors of Safety and Design Codes,Definitions,Engineers employ a,safety factor,to ensure against the forgoing unknown uncertainties involving strength and loading.,The factor is used to provide assurance that the load applied to a member does not exceed the largest load it can carry.,A common method of design is to use a safety factor with respect to strength of the member.,9,1.6 Factors of Safety and Desi,Selection of a Factor of Safety,N=,1.251.5,for exceptionally reliable materials used under controllable conditions and subjected to loads that can be determined with certainty.,N=,1.52.0,for well-known materials under reasonably constant environmental conditions,subjected to loads that can be determined readily.,N=,2.02.5,for average materials operated in ordinary environments and subjected to loads that can be determined.,N=,2.54.0,for less-tried materials under average conditions of environment,load.,N=,3.04.0,for better known materials used in uncertain environments or subjected to uncertain load.,安全餘裕,10,Selection of a Factor of Safet,Design and Safety Codes,Numerous engineering societies and organizations publish,standards,and,codes,for specific areas of engineering design.,11,Design and Safety Codes11,1.7 Units and Conversion,SI and U.S.Units,12,1.7 Units and ConversionSI and,1.8 Load Classification and Equilibrium,Conditions of equilibrium,Static problems:,Equations of statics must be satisfied.,For planar problems(x-y plane),Plane motion:,13,1.8 Load Classification and Eq,Modes of load transmission,method of sections:dividing the body,into two parts,modes of load transmission,3-D,problems:,Axial force,P,Shear forces,V,y,and,V,z,Torque(twisting moment),T,Bending moment M,y,M,z,2-D,problems:,Axial force,P,Shear forces,V,Bending moment M,14,Modes of load transmission14,Ex.1.1,Determine the member forces in a pin-connected frame.Calculate:,The component of forces acting on each member.,The axial force,shear force,and moment acting on the cross section at point,G,.,15,Ex.1.1Determine the member fo,Solution:,Tsin30,0,Tcos30,0,16,Solution:Tsin300Tcos30016,(a),(b),17,(a)(b)17,Case Study 1-2,A pin connected tool as shown.Determine the force
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