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Final Exam Review. Material-Process-Geometry Relationships. Function. Role of Prod Engr. Material. Geometry. Role of Mfg Engr. Process. Materials in Manufacturing . Most engineering materials can be classified into one of four basic categories: Metals Ceramics Polymers Composites.

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Material process geometry relationships
Material-Process-Geometry Relationships

Function

Role of Prod Engr

Material

Geometry

Role of Mfg Engr

Process


Materials in manufacturing
Materials in Manufacturing

  • Most engineering materials can be classified into one of four basic categories:

    • Metals

    • Ceramics

    • Polymers

    • Composites


Processing operations
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


Shaping four main categories
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



Stress strain relationships
Stress-Strain Relationships

  • Figure 3.3 Typical engineering stress‑strain plot in a tensile test of a metal.


True stress strain curve
True Stress-Strain Curve

Figure 3.4 ‑ True stress‑strain curve for the previous engineering stress‑strain plot in Figure 3.3.


Strain hardening
Strain Hardening

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


Recrystallization and grain growth
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-------



Allotropic transformation and tempering

Figure 6.4 Phase diagram for iron‑carbon system, up to about 6% carbon.

Allotropic Transformation and Tempering

Austenizing

Quenching

Tempered Martensite

12


Precipitation Hardening - Al 6022 (Mg-Si) about 6% carbon.

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


Machining relationships
Machining Relationships about 6% carbon.

Machine Tool

Workholding Tool

Cutting Tool

Workpiece


Effect of Higher Shear Plane Angle about 6% carbon.

  • 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



Machining calculations turning
Machining Calculations: Turning about 6% carbon.

  • 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)


  • Unit power in machining
    Unit Power in Machining about 6% carbon.

    • 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


    What if feed changes
    What if feed changes? about 6% carbon.


    Unit horsepower
    Unit Horsepower about 6% carbon.

    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


    Example
    Example about 6% carbon.

    • 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


    Example solution
    Example: Solution about 6% carbon.

    • 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


    Casting about 6% carbon.

    Common process attributes:

    • Flow of Molten Liquid Requires Heating

    • Heat Transfer of Liquid in Mold Cavity During and After Pouring

    • Solidification into Component


    Gating system
    Gating System about 6% carbon.

    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


    Pouring calculations
    Pouring Calculations about 6% carbon.

    Minimum mold filling time, MFT

    MFT =V/Q

    Q: volumetric flow rate, cm3/s

    V: mold cavity volume, cm3


    Chvorinov s rule
    Chvorinov's Rule about 6% carbon.

    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


    Amount and composition
    Amount and Composition about 6% carbon.

    Figure 6.2 Phase diagram for the copper‑nickel alloy system.


    Shrinkage in solidification and cooling
    Shrinkage in Solidification and Cooling about 6% carbon.

    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).


    Shrinkage in solidification and cooling1
    Shrinkage in Solidification and Cooling about 6% carbon.

    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).


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