Final Exam Review

1. Final Exam Review

2. Material-Process-Geometry Relationships Function Role of Prod Engr Material Geometry Role of Mfg Engr Process

3. Materials in Manufacturing • Most engineering materials can be classified into one of four basic categories: • Metals • Ceramics • Polymers • Composites

4. Processing Operations • Three categories of processing operations: • Shaping operations - alter the geometry of the starting work material • Property‑enhancing operations - improve physical properties of the material without changing its shape • Surface processing operations - clean, treat, coat, or deposit material onto the exterior surface of the work

5. Shaping – Four Main Categories • Solidification Processes - starting material is a heated liquid that solidifies to form part geometry • Deformation Processes - starting material is a ductile solid that is deformed • Material Removal Processes - starting material is a ductile/brittle solid, from which material is removed • Assembly Processes - two or more separate parts are joined to form a new entity

6. Comparing Processes

7. Stress-Strain Relationships • Figure 3.3 Typical engineering stress‑strain plot in a tensile test of a metal.

8. True Stress-Strain Curve Figure 3.4 ‑ True stress‑strain curve for the previous engineering stress‑strain plot in Figure 3.3.

9. Strain Hardening Figure 3.5 True stress‑strain curve plotted on log‑log scale.

10. Recrystallization and Grain Growth Scanning 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 cellular microstructure. --------50µm-------

11. Phase Dispersion – speed of quenching

12. Figure 6.4 Phase diagram for iron‑carbon system, up to about 6% carbon. Allotropic Transformation and Tempering Austenizing Quenching Tempered Martensite 12

13. Precipitation Hardening - Al 6022 (Mg-Si) Figure 27.5 Precipitation hardening: (a) phase diagram of an 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. 13

14. Machining Relationships Machine Tool Workholding Tool Cutting Tool Workpiece

15. Effect of Higher Shear Plane Angle • Higher shear plane angle means smaller shear plane which means lower shear force, cutting forces, power, and temperature Figure 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 rake angle is larger in (a), which tends to increase shear angle according to the Merchant equation 15

16. Turning Parameters Illustrated

17. Machining Calculations: Turning • Spindle Speed - N(rpm) • v = cutting speed • Do = outer diameter • Feed Rate - fr(mm/min -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 • Mat’l Removal Rate - MRR(mm3/min -or- in3/min)

18. Unit Power in Machining • Useful to convert power into power per unit volume rate of metal cut • Called the unit power, Pu or unit horsepower, HPu or • Tool sharpness is taken into account multiply by 1.00 – 1.25 • Feed is taken into account by multiplying by factor in Figure 21.14 where MRR = material removal rate

19. What if feed changes?

20. Unit Horsepower The 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. HPu ~ hp/in3/min Cf ~ correction factor MRR ~ in3/min Fc~ lb V ~ ft/min E ~ machine tool efficiency 33,000 ~ conversion between ft-lb & hp

21. 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 performing 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 1

22. Example: 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)(1.0) = 17,500 J/s = 17,500 W = 17.5 kW • Accounting for mechanical efficiency, Pg = 17.5/0.90 = 19.44 kW

23. Casting Common process attributes: • Flow of Molten Liquid Requires Heating • Heat Transfer of Liquid in Mold Cavity During and After Pouring • Solidification into Component

24. Gating System 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

25. Pouring Calculations Minimum mold filling time, MFT MFT =V/Q Q: volumetric flow rate, cm3/s V: mold cavity volume, cm3

26. Chvorinov's Rule where 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 moldconstant

27. Amount and Composition Figure 6.2 Phase diagram for the copper‑nickel alloy system.

28. Shrinkage in Solidification and Cooling Figure 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).

29. Shrinkage in Solidification and Cooling Figure 10.8 (2) reduction in height and formation of shrinkage cavity caused by solidification shrinkage; (3) further reduction in height and diameter due to thermal contraction during cooling of solid metal (dimensional reductions are exaggerated for clarity).