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84 Cards in this Set
- Front
- Back
Joining
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Welding, brazing, soldering or adhesive bonding; permant joint between parts
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Assembly
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mechanical methods of fastening parts together; could allow for dissassembly |
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Fusion Welding
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Metal is melted to join parts together -Arc Welding -Resistance Welding -Oxyfuel Gas Welding |
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Arc Welding
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a pool of molten material is formed near an electrode tip
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Resistance Welding
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uses friction or resistance to melt the metal and form a weld
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Solid State Welding
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uses pressure sometimes with low heat to weld with no melting
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Consumable Arc Welding
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electrodes made of a filler material are consumed during the process
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Non-consumable Arc Welding
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electrodes are not consumed and a filler material must be added separately
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Arc Shielding
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Protecting the arc from the surrounding air to prevent property degradation -Sheilding Gases -Flux |
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Flux
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a substance that prevents the formation of oxides and other contaminants, or dissolves them |
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Shielded Metal Arc Welding (SMAW)
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uses a consumable electrode consisting of a filler metal rod coated with chemicals that provide flux and shielding |
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Gas Metal Arc Welding (GMAW)
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uses a consumable bear metal wire as electrode with shielding by flooding arc with a gas
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Flux Cored Arc Welding
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core provides ingredients for shielding but outside gas can also be used.
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Types of Resistance Welding
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Seam Welding Roll Welding Explosive Welding Friction Welding |
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Brazing
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filler metal is melted and distributed by capillary action between faying surfaces (Tm>450C)
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Soldering
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filler metal is melted and distributed by capillary action between faying surfaces (Tm<450C)
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Sheet Metal Working
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Forming and related operations performed on metal sheets, strips, and coils; also called pressworking because these operations are performed on presses |
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Flow Curve For Plastic Region
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Stress=K(strain)^n s=KE^n k=strength coefficient n=strain hardening coefficient |
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Average Flow Stress
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Relationship of K and n as T increases
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K and n decrease as T increases
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Cold Working
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Performed at <0.3 Tm -Better Surface Finish, accuracy, and shape -Grain flow can cause desirable properties in product |
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Warm Working
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0.3Tm -Lower forces and power than cold working -No need for annealing |
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T_recrystallization
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about 1/2 Tm, the temperature at which a melted metal reforms crystals
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Hot Working
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Deformation at temperatures above T_recrystallization -allows for substantial plastic deformation -low strength -low strain hardening |
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Friction in Metal Forming
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Is undesirable because: -Metal flow is reduced -Forces and power are increased -Tools wear faster |
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Metalworking lubricants
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reduce the harmful effects of friction -better surface finish -remove heat from tooling |
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Forging
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Deformation process in which work is compressed between two dies
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Hot/Warm Forging advantages
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reduction in strength and increase in ductility
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Cold Forging advantage
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increased strength due to strain hardening
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Impact Forging
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uses a forge hammer, applies an impact force
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Press Forging
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applies a gradual force
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Open Die Forging
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work is compressed between two flat dies, allowing metal to flow laterally
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Impression Die Forging
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die contains cavity or impression that is imparted to workpart -Metal flow is constrained so that a flash is created |
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Flashless Forging (Closed die forging)
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workpart is completely constrained in die
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True strain
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E=ln(h0/h)
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Barreling
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Occurs in open die forging with friction
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Importance of the Flash
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As flash forms, friction resists continued metal flow into gap, constraining metal to fill die cavity
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Flash
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formed by metal that flows beyond die cavity into small gap between die plates
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Steps of Impression Die Forging
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1)Redistribute metal for more uniform deformation2)Achieve desired metallurgical structure3)Bring the part to final geometry
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Advantages of Impression Die Forging
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High production rates Greater Strength Favorable Grain Orientation |
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Upset Forging |
formas a head on a bolt or similar hardware item
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Swaging
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-rotating dies that hammer a workpiece radially inward to taper as the piece is fed into the dies -used to reduce diameter of tube or solid rod stock |
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Radial Forging
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Workpiece rotates while dies remain in a fixed orientation as they hammer the work
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Rolling
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-Pull the work into the gap between workpart and rolls -Squeeze to reduce the cross section of the work |
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Flat Rolling
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Used to reduce thickness of a rectangular cross section
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Shape Rolling
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Square cross section is formed into shape such as an I beam
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Hot Rolling
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can achieve significant deformation
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Cold Rolling
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produces sheet and plate stock
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Draft
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Amount of thickness reduction d=t0-tf |
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Reduction
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draft expressed as a fraction of starting stock thickness r=d/t0 |
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Shape Rolling
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Work is deformed into a contoured cross section rather than a flat -accomplished by passing work through rolls that have the reverse of desired shape |
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Thread Rolling
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Uses rolling dies to put grooves in screws and bolts
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Ring Rolling
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a thick walled ring is compressed, causing the diameter of the ring to enlarge -hot wok for large rings, cold work for small rings |
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Extrusion
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Compression forming process where metal is forced to flow through a die opening to produce cross-sectional shape (toothpaste)
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Direct Extrusion
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Ram approaches die opening, a small portion of billet remains that cannot be forced through the die; called the butt and must be separated afterwards -Can use a mandrel to produce hollow or semi hollow shapes |
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Indirect Extrusion
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A ram forces itself through a stationary work billet, forming a desired shape and cross section
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Hot Extrusion
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reduces strength and increases ductility of the metal, permitting more size reductions and complex shapes; heated above T_recrysal
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Cold Extrusion
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Used to produce discrete parts
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Extrusion Ratio/Reduction Ratio True Strain of Extrusion |
rx=A0/Af e=ln(rx)=ln(A0/Af) |
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Wire and Bar Drawing
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Work is pulled through die in drawing rather than pushed as in extrusion
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Area Reduction in drawing True Drawing Strain |
r=(A0-Af)/A0 E=ln(1/1-r) |
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Practical Drawing Force
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F=AfSd Sd is the exit stress |
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Bar Drawing
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Single-draft operation: the stock us pulled through one die opening
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Wire Drawing |
Continuous drawing machines consisting of multiple draw dies
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Back Relief Exit Zone
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provided with a back relief angle of about 30 degrees
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Sheet Drawing
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Sheet metal forming to make cup shaped, box shaped or other complex-curved, hollow-shaped parts
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Clearance in Drawing
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c=1.1t
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Drawing Ratio
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DR=Db/Dp Db=blank diameter Dp=Punch Diamter DR<2.0 |
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Drawing Reduction
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r=(Db-Dp)/Db
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Punch and Die
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Tooling to perform cutting bending and drawing
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Stamping Press
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machine tool that performs most sheet metal operations
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Stampings
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Sheet metal products
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Blanking
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sheet metal cutting to separate a piece from surrounding stock
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Punching
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Similar to blanking except on a smaller scale, piece is not used, but the outer piece is
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Clearance in Sheet Metal Cutting
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Range between 4-8% c=at a=allowance, t=thickness of stock |
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Cutting Forces
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F=StL S=Shear Strength, L =length of edge |
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Sheet Metal Bending
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Metal on inside of a neutral plane is compressed while metal on outside is stretched
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Bend Allowance Formula
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Ab=2pi(alpha/360)(R+(K_ba)(t) alpha=bend angle Kba=factor to estimate stretching (.33 if R<2t, .5 if R>2t) |
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Springback
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When bending pressure is removed, elastic energy remains in bent part, causing it to recover partially toward its original shape SB=(alpha-alphab)/alphab alpha b=bent angle, alpha=springback angle |
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Bending Force
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F=(KTSwt^2)/D TS=tensile strength, w=width, K=1.33/.33 for v/edge bending |
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Roll Bending
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Large Metal Sheets and Plates are formed into curved sections using rolls
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Welding Defects
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1. Cracks, 2. Cavities, 3. Solid Inclusions, 4. Incomplete fusion, 5. imperfect shape or contour of cross section
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Relationship of K to stress and strain
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lnK=ln(sigma)-nln(epsilon)
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Drawing Defects
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1. Wrinkling, 2. Tearing, 3. Earing, 4. Surface Scratches
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