1、1Materials in Manufacturing Most engineering materials can be classified into one of four basic categories: 1.Metals2.Ceramics3.Polymers4.Composites第1頁/共28頁2Processing Operations Three categories of processing operations: 1.Shaping operations - alter the geometry of the starting work material 2.Prop

2、erty enhancing operations - improve physical properties of the material without changing its shape 3.Surface processing operations - clean, treat, coat, or deposit material onto the exterior surface of the work第2頁/共28頁3Shaping Four Main CategoriesSolidification Processes - starting material is a hea

3、ted liquid that solidifies to form part geometryDeformation Processes - starting material is a ductile solid that is deformedMaterial Removal Processes - starting material is a ductile/brittle solid, from which material is removedAssembly Processes - two or more separate parts are joined to form a n

4、ew entity第3頁/共28頁 Comparing Processes4第4頁/共28頁Stress-Strain Relationships Figure 3.3 Typical engineering stress strain plot in a tensile test of a metal.5第5頁/共28頁True Stress-Strain CurveFigure 3.4 True stress strain curve for the previous engineering stress strain plot in Figure 3.3.6第6頁/共28頁Strain

5、HardeningFigure 3.5 True stress strain curve plotted on log log scale.7第7頁/共28頁Recrystallization and Grain Growth8Scanning electron micrograph taken using backscattered electrons, of a partly recrystallized Al-Zr alloy. The large defect-free recrystallized grains can be seen consuming the deformed c

6、ellular microstructure. -50m-第8頁/共28頁Phase Dispersion speed of quenching9第9頁/共28頁Allotropic Transformation and TemperingFigure 6.4 Phase diagram for iron carbon system, up to about 6% carbon.10Tempered MartensiteAustenizingQuenching第10頁/共28頁Figure 27.5 Precipitation hardening: (a) phase diagram of a

7、n alloy system consisting of metals A and B that can be precipitation hardened; and (b) heat treatment: (1) solution treatment, (2) quenching, and (3) precipitation treatment.Precipitation Hardening - Al 6022 (Mg-Si)11第11頁/共28頁Machining Relationships12Machine ToolWorkpieceWorkholding ToolCutting Too

8、l第12頁/共28頁 Higher shear plane angle means smaller shear plane which means lower shear force, cutting forces, power, and temperatureFigure 21.12 Effect of shear plane angle : (a) higher with a resulting lower shear plane area; (b) smaller with a corresponding larger shear plane area. Note that the ra

9、ke angle is larger in (a), which tends to increase shear angle according to the Merchant equationEffect of Higher Shear Plane Angle13第13頁/共28頁14Turning Parameters Illustrated第14頁/共28頁15Machining Calculations: Turning Spindle Speed - N (rpm) v = cutting speed Do = outer diameter Feed Rate - fr (mm/mi

10、n -or- in/min) f = feed per rev Depth of Cut - d (mm -or- in) Do = outer diameter Df = final diameter Machining Time - Tm (min) L = length of cut Matl Removal Rate - MRR (mm3/min -or- in3/min)oDvN 2foDDdrmfLTfNfrdfvMRR 第15頁/共28頁16Unit Power in Machining Useful to convert power into power per unit vo

11、lume rate of metal cut Called the unit power, Pu or unit horsepower, HPuor Tool sharpness is taken into account multiply by 1.00 1.25 Feed is taken into account by multiplying by factor in Figure 21.14where MRR = material removal rateMRRPPcuMRRHPHPcu第16頁/共28頁What if feed changes?17第17頁/共28頁Unit Hors

12、epowerThe significance of HPu is that it can be used: 1) to determine the size of the machine tool required to perform a particular cutting operation; and 2) the size of the cutting force on the workholding and cutting tools.18EMRRCHPEHPHPvMRRCHPvHPFMRRCHPHPfucgfuccfuc000,33000,33HPu hp/in3/minCf co

13、rrection factorMRR in3/minFc lbV ft/minE machine tool efficiency33,000 conversion between ft-lb & hp第18頁/共28頁Example In a turning operation on stainless steel with hardness = 200 HB, the cutting speed = 200 m/min, feed = 0.25 mm/rev, and depth of cut = 7.5 mm. How much power will the lathe draw in p

14、erforming this operation if its mechanical efficiency = 90%. From Table 21.2, U = 2.8 N-m/mm3 = 2.8 J/mm3 Since feed is 0.25 mm/rev, the correction factor is 119第19頁/共28頁20Example: Solution MRR = vfd = (200 m/min)(103 mm/m)(0.25 mm)(7.5 mm) = 375,000 mm3/min = 6250 mm3/s Pc = (6250 mm3/s)(2.8 J/mm3)

15、(1.0) = 17,500 J/s = 17,500 W = 17.5 kW Accounting for mechanical efficiency, Pg = 17.5/0.90 = 19.44 kW第20頁/共28頁21lFlow of Molten Liquid Requires HeatinglHeat Transfer of Liquid in Mold Cavity During and After PouringlSolidification into ComponentCastingCommon process attributes: 第21頁/共28頁22Gating S

16、ystem Channel through which molten metal flows into cavity from outside of mold Consists of a downsprue, through which metal enters a runner leading to the main cavity At top of downsprue, a pouring cup is often used to minimize splash and turbulence as the metal flows into downsprue第22頁/共28頁23Pouri

17、ng CalculationsMinimum mold filling time, MFT MFT =V/QQ: volumetric flow rate, cm3/sV: mold cavity volume, cm3第23頁/共28頁Chvorinovs Rulewhere TST = total solidification time; V = volume of the casting; A = surface area of casting; n = exponent usually taken to have a value = 2; and Cm is mold constant

18、nmAVCTST24第24頁/共28頁Amount and CompositionFigure 6.2 Phase diagram for the copper nickel alloy system.第25頁/共28頁Shrinkage in Solidification and CoolingFigure 10.8 Shrinkage of a cylindrical casting during solidification and cooling: (0) starting level of molten metal immediately after pouring; (1) reduction in level caused by liquid contraction during cooling (dimensional reductions are exaggerated for clarity).第26頁/共28頁Shrinkage in Solidification and Co