Unit 4 Mechanical Design

1、Unit 4 Mechanical Design Introduction to Mechanical Design Design Vocabulary ntransform n转换 ntransmit n传递 nutilize n利用 nengine n发动机 nturbine n涡轮 nvehicle n车辆 nhoist n卷扬机 nprinting press n印刷机 nwashing machine n洗衣机 nhub cap n轮毂盖 nfiling cabinet n档案橱柜 ninstrument n仪表 nnuclear pressure vessel n核压力容器 nap

2、paratus n仪器 nflow path n流动线路 nvolume n体积 nretention n保存 nenclosure n封装 nengineering fields n工程领域 nswitch n开关 ncam n凸轮 nvalve n阀门 nvessel n容器 nmixer n搅拌器 ndurability n耐用性 nefficiency n效率 nweight n重量 nspeed n速度 ncost n成本 ncomputation n计算 nassembly n装配 nservicing n保养 nconception n构思 narrangement n布置 nf

3、reehand sketching n画草图 nstimulant n兴奋剂 ncomponent n部件 nconceptual process n构思过程 nfeasibility n可行性 nto-scale n按比例 ndurability n耐用性 noptimum proportion n最佳比例 ndimension n尺寸 nloaded section n承载截面 nprinciples of mechanics n机械原理 nstatics n静力学 nreaction forces n反作用力 ndynamics n动力学 ninertia n惯性 naccelerati

4、on n加速度 nenergy n能量 nelasticity n弹性 nstrength n强度 nstress n应力 ndeflection n挠度 nphysical behavior n物理行为 nfluid mechanics n流体力学 nhydrodynamic drive n水利驱动 nreiterative and cooperative process n反复 / 合作过程 nreliability n可靠性 nprototype n样机 ninitial design n最初的设计 nsales appeal n销售吸引力 ncustomer satisfaction

5、n客户满意度 nmanufactured cost n制造成本 nengineering venture n工程投资 nconception n构思 nperfection n完善 nvalues of stress n应力值 ndimension n尺寸 nlimitations of operation n工作限制 nspecification n规范 narrangement n方案 ndevice n装置 ncondition of operation n工作条件 nmoment n力矩 nheavy section n大截面 nexcessive dynamic n过多动态载荷 ns

6、crap n报废 ningenuity n创造性 nphysical properties n物理性能 nfunctional loads n实用载荷 nunintentional loads n无用载荷 nloading conditions n加载条件 nstress distribution n应力分布 nstiffness n刚性 nbasic equation n基本方程 nproportion n比例 noptimize dimensions n尺寸最优化 ncombination of properties n性能组合 nstock n备件 nintegral component

7、s n集成零件 naccurate location n精确定位 nnoninterference n互不干扰 The Design Process nMachine - definition n A machine is a combination of mechanisms and other components which transforms, transmits, or utilizes energy, force, or motion for a useful purpose. ne.g.: engines / turbines / vehicles n hoists etc.

8、Engine Turbine Hoist Principles and methods of design nnot only apply to machines nbut also apply to other not true machines ne.g.: hub caps / filing cabinets n instruments etc. Hub cap Instrument Mechanical design & Machine design nMechanical design is used in broader sense than machine design. nMe

9、chanical design includes machine design. nApplications in the mechanical engineering and in other engineering fields require some other mechanical devices: switches, cam, valves etc. Steps of design n1. NEED - real / imagined n existing apparatus n improve n durability / efficiency / weight / cost n

10、 new apparatus n perform a function n computation / assembly / serving n2. CONCEPTION n sth perform a needed function n concept n mechanisms & arrangements n freehand sketching - great value n a. record designers thoughts n b. as an aid in discussion with others n c. communicate with designers own m

11、ind as a stimulant for creative ideas na broad knowledge of components is also desirable n a new arrangement na new machine n substitution of components (change in size & materials) nconceptual process n during following nquick / rough calculations or analyses n determine ngeneral size and feasibili

12、ty to-scale layout drawing nwhen some idea as to the amount of space that needed or available has been obtained n3. analysis - when the general shape and a n few dimensions of the several nbegin components become apparent nwill have as its objective satisfactory or superior performance, plus safety

13、and durability with minimum weight, and a competitive cost nPrinciples of mechanics - statics / dynamics etc. n analysis n a. optimum proportions and dimensions will n be sought for each critically loaded section n b. together with a balance between the n strengths of the several components n c. mat

14、erials and their treatment will be n chosen n obtain such important objectives n analyses n can be made n1. by the same engineer who conceived the arrangement of mechanisms n2. in a large company, by a separate analysis division or research group n result n new arrangement & dimensions required n De

15、sign is a reiterative and cooperative process, whether done formally or informally, and the analyst can contribute to phase other than his own. n4. prototype - a design based upon function n and reliability will be completed n test satisfied n produce in quantity modify the initial design n at a low

16、er cost Some rules for design n1. Apply ingenuity to utilize desired physical properties and to control undesired ones. n2. Recognize functional loads and their significance. n3. Anticipate unintentional loads. n4. Devise more favorable loading conditions. n5. Provide for favorable stress distribution and stiffness with minimum weight. n6. Use basic equations to proportion and optimize dimensions. n7. Choose mat