Term
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Definition
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Term
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Definition
| aluminum, magnesium, copper, nickel, titanium |
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Term
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Definition
No waste
1. Minimize waste 2. Perfect first-time quality 3. Flexible production lines 4. Continuous improvement |
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Term
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Definition
| the smallest group of atoms showing the characteristic lattice structure |
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Term
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Definition
| 1. BCC (alpha iron) 2. FCC (gamma iron) 3. HCP |
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Term
| External force is applied |
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Definition
Elastic deformation
Plastic deformation |
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Term
| Two basic mechanism of plastic deformation |
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Definition
Slip plane under a shear stress
Twining |
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Term
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Definition
Ductile metals: 5 or more slip systems
Brittle metals: less than 5 slip systems |
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Term
| Crystal structures .vs. slip systems |
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Definition
BCC: 48 possible slip
FCC: 12 slip
HCP: 3 slip |
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Term
| Defects of crystalline structures |
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Definition
Vacancy, interstitial atom, impurity
Dislocation
Planar imperfection(grain boundaries and phase boundaries)
Volume, bulk imperfection |
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Term
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Definition
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Term
| When molten metal solidifies |
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Definition
Crystals begin to form at arious locations
Each crystal has a random orientations
• Each crystal grows into a crystalline or grain
Grains size and number depends on the nucleation rate |
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Term
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Definition
Low strength, low harness, low ductility
Rough surface appearance |
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Term
| What happens to grains at elevated temperatures |
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Definition
Grain boundary sliding =>plastic deformation
Creep mechanism |
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Term
| Plastic deformation of polycrystalline metals |
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Definition
Grain boundaries remain intact
Mass continuty is maintained
Exhibits higher strength b/c of entanglement of dislocations
• The higher the deformation, the stronger the metal becomes (larger grain-boundary=> more entanglement)
Results in anisotrophy of crystal |
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Term
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Definition
| Change mechanical and phsyical properties of metals |
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Term
| Crystallographic anisotropy |
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Definition
| -slip systems tend to align themeslves with the direction of deformation |
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Term
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Definition
-results from the alignment of inclusion, impurtities, and voids in the metals during deformation
-metal is weaken and less ductile in the direction erpendicular to the deformation |
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Term
| Recovery, recrystallization and grain growth |
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Definition
Plastic deformation increase in sterength, decreasein ductility, cause anisotropic behavior
Annealig can bring the original properties back |
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Term
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Definition
| Heating metals to a sepcific temperature range for a period of time |
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Term
| Three events during the annealing process |
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Definition
1. recovery
2. recrystallization
3. grain growth |
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Term
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Definition
Happens below the recrystallization temperature
Stresses in the highly deformed regions are relieved
Polygonization
-no significant change in mechanical properties(hardness, strength) |
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Term
| Recrystallization(annealing) |
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Definition
New equiaxed and strain-free grains are formed
New grains replace old grains
Happens at 0.3 to 0.5Tm (Tm: melting temp.)
The higher the temp., the shorter the recrystallization time takes
The more the prior cold work, the lower the temp. required
The greater the degree of deformation, the smaller the grain size becomes
Anisotropy remains during the recrystallization |
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Term
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Definition
If we continue to raise the temperature, the grains begin to grow
Affects mechanical properties |
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Term
| Cold warm, and hot working |
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Definition
Cold working: plastic deformation at room temp.
Hot working: plastic deformation above the recrystallization temp.
Warm working: plastic deformation at intermediate temp. |
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Term
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Definition
-specimen elongates in proportion to the load
-specimen returns to its original length when load Is removed |
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Term
| Engineering stress (nominal stress) |
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Definition
| -ratio of the applied load, P, to the original cross sectional area |
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Term
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Definition
| -ratio of the change in length to the original length |
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Term
Elastic region
Modulus of elasticity (Hooke’s law) |
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Definition
| -Ratio b/w stress and strain |
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Term
Elastic region
Poisson’s ratio |
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Definition
| -value of the ratio of the lateral strain to the longitudinal strain |
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Term
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Definition
Permanent deformation
Stress and strain is no-long proportional
Yield stress
-start of plastic deformation
-defined as offset by strain of 0.002 (0.2%)
When released
-the stress-train curve follows a straight line downward parallel to the original slope of the elastic region
Necking occurs at ultimate stress |
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Term
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Definition
| -The extent of plastic deformation that the material undergoes before fracture |
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Term
Ductility
Two common measure |
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Definition
1. Total elongation
2. Reduction of area |
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Term
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Definition
| -the ratio of the load, P, to the actual cross-sectional area |
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Term
|
Definition
-elongation of the specimen to consist of increments of instantaneous change in length
-natural or logarithmic strain |
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Term
| Strain at necking in a tension test |
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Definition
Necking occurs at ultimate tensile strength
The slope of the load-elongation curve at necking is zero
Cross-sectional area is becoming smaller at a rate that is higher than the rate at which the material becomes stronger-break
True strain at onset of necking is equal to the value of n or (ε=n) |
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Term
| Strain at necking in a tension test |
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Definition
Specific energy
-energy-per unit volume of the material deformed
-the area under the true stress-true strain curve at a particular strain
Toughness
-the area under the true stress-true strain curve at a particular strain
-amount of energy |
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Term
| Other effects of tensile test |
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Definition
Increasing the temperature
-raises the ductility and toughness
-lower the yield stress and the modulus(abs. value) of elasticity
Strain rate(deformation rate) effects
-the speed at which a tension test is being carried out (m/s)
-increasing strain rate increases the strength of the material (strain-rate hardening) |
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Term
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Definition
Forging, rolling, extrusion
Barreling occurs during compression by friction/w specimen and th platens
Buckle can occur for slender specimens |
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Term
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Definition
-friction dissipation energy(compression force is higher then tensile) => lubrication required
Tensile test and compression test results are compatible for ductile material, but not for brittle material(more ductile in compression) |
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Term
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Definition
-To determine the properties of materials in shear
-Use a thin tubular specimen
Shear stress for a thin tube under torsion
Shear strain for a tube under torsion |
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Term
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Definition
Bending test uses a rectangular cross-section supported at its ends
Test for modulus of rupture of flexural strength for brittle materials
Hardness |
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Term
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Definition
-Press a steel or tungsten-carbide ball (10mm in diameter) with a load of 500, 1500, or 3000kg
-measures the diameter of indentation |
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Term
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Definition
-measures the depth of penetration
-uses various types of indenters
-apply a minor load and then a major load |
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Term
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Definition
| under the cyclic stress, a member fails below the failure stress of static load |
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Term
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Definition
| : cracks that grow with every stress, propagate through the material until a critical crack length is reached |
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Term
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Definition
| -Various stress amplitudes (S) and number of cycles (N) => S-N curve |
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Term
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Definition
| The maximum stress to which the material can be subjected w/o fatigue failure |
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Term
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Definition
| Permanent elongation of a component under a static load maintained for aperiod of time(elevated temp.) |
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Term
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Definition
| grain-boundary sliding (mostly above room temo.) |
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Term
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Definition
| -put a specimen under constant tensile load until creep rupture |
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Term
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Definition
| takes place along the planes on which the shear stress is maximized |
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Term
Ductile fracture
Failure mechanism |
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Definition
| Initiated with the formation of tiny voids, small inclusions or preexistion voids =>grow, coalesce developing into microcracks |
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Term
| Two factors affecting void formation |
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Definition
1.The strength of the bond at the interface b/w an inclusion (strong bond =>less tendency of void formation)
2. Hardness of the inclusion and matrix |
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Term
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Definition
Fracture with little or no plastic deformation
Takes place along the crystallographic plane (cleavage plane) where the normal tensile stress is a maximum
BCC or HCP metals
Low temp. or high rate of deformation promotes brittle fracture. |
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Term
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Definition
An important factor in fracture
Scratches, flaws, pre-existing external or internal cracks
Catastrophic failure: under excessive tensile stress by crack propagation |
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Term
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Definition
Minute external or internal cracks develop flaws or defects
Cracks spread over a period of time
Remaining tensile stress promotes fatigue failure |
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Term
Fatigue fracture
Can increase the fatigue life by preparation of the surfaces of the part or specimen such as |
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Definition
1. Inducing compressive remaining stresses on surfaces (shot peening)
2. case hardening (surface hardening)
3. fine surface finish
4. selecting appropriate materials |
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Term
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Definition
Occurs when a work piece is subjected to not uniform plastic deformation
Remain stressed after the removal of the external forces |
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Term
| Substitution solid solutions |
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Definition
Size of the solute atom is similar to that of the solvent atom
Solvent’s Chrystal structure remain unchanged
Solute atom replaces solvent atoms
EX: brass(Zinc copper alloy) |
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Term
| Two conditions must be met (Hume-Rothery rules) |
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Definition
1. Two metals must have similar crystal structures
2. the difference in their atomic radii should be less than 15% |
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Term
| Interstitial solid solutions |
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Definition
Solute atom is much smaller than that of the solvent atom
Solute atom occupy an interstitial position |
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Term
| Two conditions necessary for forming interstitial solutions |
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Definition
1. The solvent atom must have more than one valence electron
2. The atomic radius of the solute atom must be less than 59% of the atomic radius for the solvent atom
EX) steel (iron +carbon => versatile and useful materials |
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Term
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Definition
Two metals in a complex structures
Solute atoms present among solvent atoms in certain proportions
Type of atomic bond
-Metallic
-Ionic
Strong, hard, and brittle, high-melting points
Good for advanced gas-turbine engines |
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Term
| Compound as two-phase system |
|
Definition
Compounds
-Homogeneous solid phase in which elements are distributed uniformly throughout the solid mass (water-sand)
Two-Phase system
-Most alloy type (tow or more solid phase)
Mechanical mixtures |
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Term
|
Definition
Phase: physically distinct and homogeneous portion in a material
Pinning (blocking)-blocking of dislocations => improve strength
In general, two-phase alloys are stronger and less ductile than solid solutions |
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Term
| Alloying with second phase particles in an important method of strengthening alloys, and controlling their properties |
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Definition
1.Dispersed structure(lead-copper)
2. Aggregate structure |
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Term
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Definition
-Relationship among the temperature, the composition, and the phases present in a particular alloy system under equilibrium conditions
Binary phase diagram (two elements)
Eutectic point: liquid solution decomposes into the components alpha and beta |
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Term
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Definition
Pure iron => delta ferrite =>austenite => alpha ferrite=> Cementite
α= alpha ϒ=gamma δ= delta |
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Term
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Definition
BCC iron, maximum solid solubility of 0.022% C at 727 degrees C
Soft, ductilre, magnetic
Amount of carbon significantly affects the mechanical properties
Can be alloyed with chromium, manganese, nickel, molybdenum, tungsten, and silicon
δ Ferrite: stable only at high temp., no practical significance |
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Term
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Definition
FCC (polymorphic transformation from BCC)
Solid solubility of up to 2.11% Carbon at 1148 degrees C (more interstitial space =>two orders or magniture higher)
Becomes gamma+cementitie (eutectoid reaction) at lower temp.
Ductile at elevated temp. good formability
Can be alloyed with nickel, manganese |
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Term
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Definition
Iron carbide 6.67% C
Very hard, brittle intermetallic compound
Significant influence on the properties of steels
Can be alloyed with chromium, molybdenum, and manganese |
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Term
| Iron-Iron carbide phase diagram |
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Definition
Change in micro-structures depending on carbon content, amount of plastic deformation, and the method of heat treatment
Eutectic composition: 0.77% C
When cooled slowly (equilibrium)
-Austenite transforms into alpha-ferrite (only 0.022%C) and cementite (with extra C) at 727 degrees C
Eutectoid steel => pearlite
Pearlite: alternating layers (lamellae) of alpha-ferrite (soft, ductile) and cementite (hard, brittle)
Iron with less than 0.77%C is composed of ferrite and pearlite |
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Term
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Definition
Cast iron tends to be brittle, except for malleable cast irons
With its relatively low melting point, good fluidity, cast-ability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications |
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Term
| Classification (solidification morphology) |
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Definition
-Gray cast iron
-Ductile cast iron, nodular cast iron or spheroidal graphite cast iron
-White cast iron
-Malleable iron
-Compacted graphite iron |
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Term
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Definition
| contains flake graphite, negligible ductility, weak in tension, flake graphite gives dampening vibration, dissipate energy, constructing machinery structure |
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Term
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Definition
Spheroidal graphite, ductile, shock-resistant
Tiny amounts of magnesium or cerium added to these alloys slow down the growth of graphite |
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Term
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Definition
| Very hard, wear-resistant, brittle by presence of large amount of iron carbide (no graphite, but cementite), made by cooling gray iron rapidly or by adjusting the composition (low carbon, low silicon) |
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Term
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Definition
By annealing white cast iron in carbon monoxide, carbon dioxide at between 800°C and 900°C for several hours. Cementite decomposes into iron and graphite (It is often used for small castings requiring good tensile strength and the ability to flex without breaking (ductility).
Electrical fittings, hand tools, pipe fittings, washers, brackets, fence fittings, power line hardware, farm equipment, mining hardware, and machine parts) |
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Term
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Definition
Short, thick and interconnected form of graphite. Mechanical properties between flake and nodulare graphite cast iron
brake discs for high speed rail trains, diesel engine blocks (V topology diesel ), turbo housings and exhaust manifolds |
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Term
| Heat treatment of ferrous alloys |
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Definition
Controlled heating/cooling of material
Heat treatment can modify microstructures
Induce phase transformations => mechanical properties
Effects of HT depends on alloy type, composition, microstructures, degree of prior cold work, rates of heating/cooling |
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Term
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Definition
•Pearlite is soft and allows flexibility without being brittle.
•lower Bainite (250-400 C) is springy, allowing a blade to bend and return with less permanent deformation as pearlite. Upper Bainite (400-500 C) is springy, but is considerably more rigid (therefore fragile) than lower bainite
•Martensite is what generally makes up a hamon (swordsmithing) on a Japanese sword. |
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Term
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Definition
•Slow rate of cooling (furnace cool) Eutectoid steel => pearlite (C:<.77%)
•Pearlite: alternating layers (lamellae) of alpha-ferrite (soft, ductile) and cementite (hard, brittle)
•Fine pearlite
oLmellae is thin, closely packed
oHigh rate of cooling (air cool)
•Coarse pearlite
oLamellae is thick, widely spaced |
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Term
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Definition
•Subcritical annealing of pearlite (just below the eutectoid temp. -700 degrees C) for a day
•Cementite lamellae transform to spherical shapes
•Less conducive to stress concentration (rounded shapes)
•Higher toughness, lower hardness than pearlite
•Less conducive to stress concentration |
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Term
|
Definition
•Very fine, acicular, micro-structure consisting of ferrite and cementite
•Similar to the microscopic structure of tempered martensite
•Cementite and dislocation-rich ferrite (harder)
•Higher cooling rate then those required for austenite to pearlite transformation (b/w pearlite and martensite)
•Stronger, less ductile than pearlite steels |
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Term
|
Definition
•High rate cooling from austenite (quenching in water)
•FCC transforms into BCC (less slip system)
•Carbon is in interstitial position
•Extremely hard and brittle
•Lacks toughness, distortion may occur by quenching
•Tempering is necessary to improve toughess |
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Term
| Heat treatment of nonferrous alloys and stainless steels |
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Definition
•NF alloys, stainless steels cannot be heat treated
•Do not undergo phase transformations
•Precipitation hardening
oCopper atoms diffusion to nucleation sites and combine with aluminum atoms
oIncreased resistance to dislocation by precipitates
oAluminum alloys, copper alloys, martensitic stainless steels
•Solution treatment
oHeated with the solid solution Kappa phase and then cooled rapidly(water)
oSingle phase kappa-monderate strength, considerable ductility |
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Term
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Definition
•Restoration of a cold-worked or heat-treated alloy to its original properties
•Increase ductility, reduce hardness and strength
•Modify microstructure
•Relieve residual stresses
•Improve formability, machinability
•Lower temp. to prevent surface oxidation |
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Term
|
Definition
1. Heating the workpiece to a specific range of temperature in a furnace
2. Holding it at the temperature for a period of time
3. Cooling in air or in a furnace |
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Term
|
Definition
•To avoid excessive softness from the annealing of steels
•Cooling cycle completely in still air
•Transform the structure to austenite
•Higher strength and harness, lower ductility
•Refine grain structure, uniform structure(homogenization)
•Decrease residual stresses, improve machinability |
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Term
|
Definition
•Reduce brittleness of heat treated steels
•Increase ductility and toughness
•Reduce residual stresses
•Transform to bainite or feerite/cenmentite
•Precipitation hardening (ex, different grade of alumninum, superalloy)
•Heat steels to a specific temp. time and cooled at a prescribed rate |
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Term
|
Definition
•Tool material and coatings
•Tool shape, surface finish, and sharpness
•Workpiece material and condition
•Cutting speed, feed, and depth of cut
•Cutting fluids
•Characteristics of the machine tool
•Workholding and fixturing |
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Term
|
Definition
•Type of chip produces
•Force and energy dissipated during cutting
•Temperature rise in the workpiece, tool and chips
•Tool wear and failure
•Surface finish and surface integrity of the workpiece |
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Term
|
Definition
•Two dimensional model
•Forces are perpendicular to each other
•Rake, clearance angles
•Chip formation mechanism – shearing along shear plane |
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Term
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Definition
| work piece is rotated and a cutting tool removes a layer of material as it moves to the left |
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Term
|
Definition
| off operation: cutting tool moves radially inward and separates the right piece from the bulk of the blank |
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Term
|
Definition
| rotating cutting tool removes a layer of material from the surface of the work piece |
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Term
|
Definition
| a rotating cutter travels along a certain depth in the work piece and produces a cavity |
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Term
|
Definition
Makes batch manufacturing (which is producing mass amounts of items quickly) more efficient.
A manufacturing philosophy to take advantage of similarities in design and production. |
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Term
|
Definition
| It is because it has a higher level of integration b/w the design and manufacturing functions for better efficiency. |
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Term
|
Definition
Similar parts are arranged into part families
Each part family possesses similar design and/or manufacturing characteristics
Efficiencies are achieved by cellular manufacturing. |
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Term
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Definition
| - production via grouping equipment’s into machine groups or cells. |
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Term
|
Definition
•GT promotes standardization of tooling, fixturing, and setups.
•Material handling is reduced (parts move within a cell)
•Process planning and production scheduling are simplified
•Setup times are reduced, (lower manufacturing lead time)
•Work-in-[process is reduced
•Worker satisfaction usually improves by collaboration higher quality work is accomplished |
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Term
|
Definition
•Shorten manufacturing lead times
•Reduce work-in-process inventory
•Improve quality
•Simplify production scheduling
•Reduce setup times |
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Term
|
Definition
• Part family =>Composite part
•Composite part: a hypothetical part which includes all the design and manufacturing attributes of the family (all the features)
•Manufacturing cell can handle all the parts in the part family than composite parts. |
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Term
| How to classify (category)? |
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Definition
•Design qualities: geometry, size, material
•Manufacturing qualities: processing sequence
•Both design and manufacturing attributes |
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Term
|
Definition
•Design retrieval (similar parts?)
•Automated process planning (database)
•Machine cell design (for part family) |
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Term
| Commercial package available? |
|
Definition
•Numerous package available
•No universal package- customization required for different companies |
|
|
Term
| Three types of coding systems |
|
Definition
1.Hierarchical structure (monocode)
-Each symbol depends on the preceding symbols
2.Chain-type structure (polycode)
-No dependency
3.Mixed-mode structure
-Hybrid of two previous codes |
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Term
| Two important coding systems |
|
Definition
1. Optiz classification sytems
2. MultiClass |
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|
Term
| Optiz Classification system |
|
Definition
| Form code, Supplementary code , Secondary code |
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Term
|
Definition
| Primary design attributes (external shape, machined features…) |
|
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Term
|
Definition
| : Manufacturing attributes (dimensions, work materials, accuracy…) |
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Term
|
Definition
| Production operation type and sequence |
|
|
Term
| Multiclass Coding system: |
|
Definition
1. Suggested by OIR
2. Flexible (good for customization)
3. Hierarchical or decision-tree coding structure
4. 30 digits, 2 regions (OIR, users) |
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Term
| Production flow analysis (PFA) |
|
Definition
• Uses production route sheet, Manu. Data based approach
• Con overcome 2 possible anomalies
1. Parts with different geometry may require similar process routing
2. Parts with similar geometry may require different process routing. |
|
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Term
|
Definition
| 1. Data Collection 2. Sortation of process routings 3. PFA chart 4. Cluster analysis (rank order clustering) |
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Term
| Arranging machines in a GT cell: |
|
Definition
•Hollier’s methods (1st and 2nd method)
•Use from-to chart
•Maximizes the proportion of in-sequence moves within the cell |
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Term
|
Definition
•The machine having the smallest sum is selected.
•If the min value is a “to” sum, then the machine is placed at the beginning of the sequence,
•If the min value is a “From” sum, then the machine Is placed at the end of the swquence. |
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Term
| Hollier’s method 1:Tie breaker rules: |
|
Definition
oIf a tie occurs b/w min “To” and min “From” sums, then the machine with the min “From/To” ratio is selected.
oIf both “To & From” sums are = for a selected machine, it is passed over and the machine with the next lowest sum is selected.
oIf a min “To” sum is = to min “From” sum, then both machines are selected and placed at the beginning and end of the sequence, respectively. |
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|
Term
| 1.List important mechanical properties for materials before selecting one for an engineering application. |
|
Definition
| , toughness, ductility, hardness, elasticity, fatigue, and creep |
|
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Term
|
Definition
| minimize waste, perfect first time quality, flexible production lines, continuous improvement |
|
|
Term
| What are the four principles to exercise agile manufacturing? |
|
Definition
| organize to master change, leverage the impact of people and information, cooperate to enhance competitiveness, enrich the customer |
|
|
Term
| Actual strength of metals is approximately one to two orders of magnitude lower then the theatrical strength |
|
Definition
| defects and imperfections |
|
|
Term
| After a significant amount of cold work through plastic deformation, strain hardening occurs. Explain two important mechanisms of strain hardening. |
|
Definition
| dislocations become entangled, impeded by barriers |
|
|
Term
| The temperature where a liquid solution decomposes into two solid components is called |
|
Definition
|
|
Term
| Porosity is the one of most critical problems in casting. Describe four methods to eliminate porosity in the casting process. |
|
Definition
| 1. Adequate liquid metal 2. Internal or external chills 3. Mold materials with higher thermal conductivity 4. Subject casting to hot isostatic pressing |
|
|
Term
| Describe about 5 important manufacturing processes. |
|
Definition
| ) casting 2) forming and shaping 3) machining 4) joining 5) finishing |
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Term
| What are the two different ways of measuring the ductility? |
|
Definition
| 1) total elongation 2) reduction of area |
|
|
Term
| What is the failure mode of engineering material by grain boundary sliding at an elevated temperature? |
|
Definition
|
|
Term
| 41. When austenite transforms into α ferrite (only .022%C) and cementite (with extra C) at 727 degrees C, the reaction is called(______) and the steel type is(_______) |
|
Definition
reaction: pearlite
steel: eutectoid |
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|
Term
| In (________) forging, workplace takes the shape of the die cavity of two dies. Flash forms at the die outward and it prevents further flow of the blank in the die. It is often used for coin production. |
|
Definition
|
|
Term
|
Definition
-Has clearly defined melting point
-Columnar grains: grow in opposite direction of heat transfer
-Homogenous nucleation: equiaxed and coarse grain formed away from the wall (less effect if heat transfer) |
|
|
Term
|
Definition
-slow cooling rate: coarse dendrite with large spacing b/w dendrite arms
-higher cooling rates: structure becomes finer with smaller dendrite arm spacing
-fast cooling rates: amorphous structure |
|
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Term
|
Definition
| -smaller the grain size => stronger and ductile, less microporosity, less crack |
|
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Term
|
Definition
-Formation of an outer chill zone
-refines grain size
-accelerates the transition from columnar to equiaxed grains |
|
|
Term
|
Definition
-break dendrite arms by vibration or agitation in early stages of solidification
-finer grain size with equiaxed non-dendritic grains distributed uniformly |
|
|
Term
|
Definition
•Viscosity
•Surface tension
•Inclusions
•Solidification pattern of the alloy
•Mold design
•Mold material and its surface characteristics
•Degree of superheat
•Rate of pouring
•Heat transfer |
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|
Term
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Definition
Metal flows rates must be high enough o avoid premature chilling and solidification
Flow rate must not be so high as to cause excessive turbulence
Temperature distribution at the interface of the mold wall
Temperature drop at the air-mold and mold-metal interfaces in by
-boundary layers
-imperfect contact at these interfaces |
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Term
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Definition
1. Contraction of the molten metal as it cools prior to its solidification
2. Contraction of the metal during phase change from liquid to solid
3. Contraction of the solidified metal as its temperature drops to ambient temperature |
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Term
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Definition
A-Metallic projections
B-Cavities
C-Defective surface
E- incomplete casting
F-incorrect dimensions or shape
G-Inclusion |
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Term
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Definition
Caused by shrinkage or gases or by both
Porous region develop at the center of thick area
Microporosity can develop when the liquid metal solidifies and shrinks b/w dendrites, and their branches
Porostiy is detrimental to the ductility of a casting and surface finish |
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Term
| How to eliminate porosity |
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Definition
Adequate liquid metal
Internal or external chills
Mold materials with higher thermal conductivity
Subject casting to hot isostatic pressing |
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Term
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Definition
| process of reducing the thickness or changing the corss-section of a long workpiece by compressive forces applied through a set of rolls |
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Term
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Definition
| combine continuous casting with rolling processes for productivity gain and cost reduction |
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Term
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Definition
| : coarse-grained, brittle, porous structure of ingot is broken down into a wrought structure (finer grain, better strength, hardness, surface finish, wrought means worked) |
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Term
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Definition
Relative sliding b/w roll (constant speed) and strip along the arc.
Neutral point: no-slip point
Net frictional force must be positive
Increased friction force requires increased energy
High friction could damage the surface-requires lubricants |
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Term
| How to reduce the roll force? |
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Definition
reducing friction at the roll-workpiece interface
-using smaller-diameter rolls to reduce the contact area
-taking smaller reductions-per-pass to reduce the contact area
-Rolling at elevated temperatures to lower the strength of the material
-applying tensions to the strip |
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Term
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Definition
Rolls undergo shape changes during rolling due to roll forces.
Roll forcs tend to bend the rolls elastically during rolling (need high elastic modulus)
Ground roll (slightly larger diameter at the center) can reduce camber problem(should consider load, and strip width)
External bending moment at both can also reduce the camber problem
Roll strip tends to be thicker at its center than at its edge (barrel shape by plastic deformation during rolling- thermal camber)
Control of camber by adjusting the location and the flow rate of the coolant is important
Roll forces tend to flatten the rolls elastically-larger contact area-roll force increases |
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Term
| Spreading in flat rolling |
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Definition
Width of the strip remains effectively constant during rolling (due to high wdith-to-thickness ratios)
Width increases significantly for smaller ratios (square cross-section) =>spreading |
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Term
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Definition
1. increase width-to-thickness ratio of the entering strip
2. use vertical roll in contact with the edges of the rolled produt |
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Term
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Definition
Initial rolling-hot rolling
Blooms are further processes to make structural shapes (I-beams, rail by shape rolling)
Slabs are rolled into plates and sheets)
Billets are square and later area rolled into various shapes (round, bars..) |
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Term
| Initial rolling-hot rolling |
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Definition
-changes dendritic, coarse, brittle, porous, nonuniform grains from cast to wrought structure
-called bloom, slab, or billets |
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Term
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Definition
Room temperature
Sheets and strips with much better surface finish, tolerances, and mechanical properties(strain hardening) |
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Term
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Definition
| -two or more layers or metal are rolled together improving productivity |
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Term
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Definition
| Wavy edges, zipper cracks in the center of the strip, edge cracks and alligatoring |
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Term
| Other characteristics of rolled metals |
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Definition
Residual stresses
Surface roughness |
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Term
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Definition
| -fine surface for cold, rough for hot(need further steps) |
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Term
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Definition
| -due to non-uniform deformation |
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Term
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Definition
Roll equipment with diverse roll arrangements
Highly automated mills
Close-tolerance
High quality plates and sheets
High production rates
Low cost-per-unit weight |
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Term
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Definition
is a basic process in which the work piece is shaped by compressive foces applied through various dies and tooling
Turbines, gears, bolts and rivets, hand tools, machinery components, aircraft, railroads
Discrete parts by metal flow in a die
Good strength and toughness by grain structures of forged parts |
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Term
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Definition
Simple, inexpensive die
-wide range of part sizes, good strength, for small quantities
-barreling by frictional forces |
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Term
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Definition
-open-die forging
-thickness is reduced by successive forging steps
-small contact: small force, no large equipment for long bars |
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Term
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Definition
-work piece takes the shape of the die cavity in two dies
-elevate temp. for enhanced ductility, less force
-flash forms at the die outward: prevent further flow |
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Term
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Definition
-good utilization of material
-better properties then open-die
-good dimensional accuracy, high production rates, good reproducibility
-low die costs, high production rates |
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Term
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Definition
Fullering: distribute material away from on area
Edging: gather material into an area |
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Term
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Definition
| of continuous and discrete products |
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Term
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Definition
-billet is placed in a chamber
-hydraulically driven ram force the material through a die opening |
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Term
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Definition
Cold extrusion
-room temperature
-often with forging operstions
Hot extrusion
- elevated temperate
-low ductile material |
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Term
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Definition
-reducing cross section by pushing materials through a die
-shafts, spindles, small pistons and raw material for fasteners (rivets, bolts, and screws)
-cup-shaped parts by sheet-metal forming operation |
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Term
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Definition
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Term
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Definition
-metal flow pattern
-caused by increased die angle, higher friction b/w billet and chamber
-tends to draw surface oxides and impurities toward the center of the billet |
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Term
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Definition
-high extrusion temperature, friction, or speed
-high surface temperature => surface cracking and tearing (firtree cracking or speed cracking) |
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Term
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Definition
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Term
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Definition
-crack at the center of the extruded product
-not noticeable => cause failure later
-center crack increases with increasing amount of impurities, increase in die angle
-forms when two plastic zone does not meet each other
-decreases with larger plastic zone => decreases die angle or increase extrusion ratio and friction, or change it to indirect or hydrostatic extrusion |
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