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59 Cards in this Set
- Front
- Back
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acoustic emission
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an NDT technique that employs stressing a structure and then listening to the reaction with sensitive microphones
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corrosion
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material removal or loss of properties by chemical or environmental attack
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eddy current
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an inspection process that uses induced magnetic fields to generate minute currents in a material that can be sensed and related to the internal condition of the material
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magnetic particle inspection
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a technique wherein iron particles pinpoint surface defects on a part by accumulating at them when appropriate magnetic fields are applied to the part
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nondestructive testing (NDT) or evaluation (NDE)
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the science and art of scrutinizing a part or structure for defects that could jeopardize serviceability
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radiography
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the use of ionizing radiation to image internal defects and features in a solid
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tomography
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technique wherein computers control the x-raying of a solid from many angles and 3D images are generated by the computer to show the internal soundness of the solid
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ultrasonics
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the use of transmitted or reflected sound waves to inspect for subsurface defects in a solid
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What can be said about graphs a-d?
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"(a) Has significant work-hardening which is evident from t's continued ability to withstand increased stress until fracture.
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Calculate the Modulus of Elasticity
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E= change in stress/change in strain
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Calculate the Percent Elongation
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% elongation = (final length-initial length) / initial length
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Calculate the Percent Reduction in Area
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% Reduction in Area = (initial area-final area) / initial area
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Calculate Resilience
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Resil.
= 1/2 * (stress at elastic limit)^2 * (strain at elastic limit) = ((stress at elastic limit)^2) / (2*mod of elas) |
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What does a high percent elongation indicate?
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The material is more ductile and therefore formable.
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State the differences between the stress-strain diagram created using the data in this excel sheet and a true stress-strain diagram. Using a true stress-strain diagram can provide us with what further information about the material.
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The engineering stress-strain diagram created is not a measure of true stress and true strain.
To get true values you need to measure the instantaneous gage lengths and diameters as the test proceeds using an extensometer. Once we have the true-stress and true strain we can determine the strain-hardening coefficient (n) which indicates how much a material will work harden when subjected to plastic deformation. This is important in many shaping and molding processes. |
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What materials is creep important in? What materials is creep not so important in?
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"Creep is very important in materials with low melting points such as polymers.
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What can be said about graphs a-d?
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(a) Has significant work-hardening which is evident from t's continued ability to withstand increased stress until fracture.
(b) exhibits very little work hardening but the ductility allows it to continue to elongate. (c) Is extremely brittle with no ability to work harden (d) Ductile plastics undergo a reorganization and reorientation strengthening at the atomic level before fracture |
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Calculate the Modulus of Elasticity
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E= change in stress/change in strain
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Calculate the Percent Elongation
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% elongation = (final length-initial length) / initial length
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Calculate the Percent Reduction in Area
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% Reduction in Area = (initial area-final area) / initial area
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Calculate Resilience
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Resil.
= 1/2 * (stress at elastic limit)^2 * (strain at elastic limit) = ((stress at elastic limit)^2) / (2*mod of elas) |
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What does a high percent elongation indicate?
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The material is more ductile and therefore formable.
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State the differences between the stress-strain diagram created using the data in this excel sheet and a true stress-strain diagram. Using a true stress-strain diagram can provide us with what further information about the material.
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The engineering stress-strain diagram created is not a measure of true stress and true strain.
To get true values you need to measure the instantaneous gage lengths and diameters as the test proceeds using an extensometer. Once we have the true-stress and true strain we can determine the strain-hardening coefficient (n) which indicates how much a material will work harden when subjected to plastic deformation. This is important in many shaping and molding processes. |
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What is resilience, how does this differ from toughness?
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Resilience is a measure of the ability of a material to absorb elastic energy
Toughness is the ability of the material to absorb all energy before fracture |
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What materials is creep important in? What materials is creep not so important in?
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"Creep is very important in materials with low melting points such as polymers.
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What can be said about graphs a-d?
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(a) Has significant work-hardening which is evident from t's continued ability to withstand increased stress until fracture.
(b) exhibits very little work hardening but the ductility allows it to continue to elongate. (c) Is extremely brittle with no ability to work harden (d) Ductile plastics undergo a reorganization and “orientation strengthening†at the atomic level before fracture |
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Calculate the Modulus of Elasticity
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E= change in stress/change in strain
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Calculate the Percent Elongation
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% elongation = (final length-initial length) / initial length
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Calculate the Percent Reduction in Area
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% Reduction in Area = (initial area-final area) / initial area
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Calculate Resilience
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Resil.
= 1/2 * (stress at elastic limit)^2 * (strain at elastic limit) = ((stress at elastic limit)^2) / (2*mod of elas) |
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What does a high percent elongation indicate?
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The material is more ductile and therefore formable.
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State the differences between the stress-strain diagram created using the data in this excel sheet and a true stress-strain diagram. Using a true stress-strain diagram can provide us with what further information about the material.
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The engineering stress-strain diagram created is not a measure of true stress and true strain.
To get true values you need to measure the instantaneous gage lengths and diameters as the test proceeds using an extensometer. Once we have the true-stress and true strain we can determine the strain-hardening coefficient (n) which indicates how much a material will work harden when subjected to plastic deformation. This is important in many shaping and molding processes. |
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What is resilience, how does this differ from toughness?
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Resilience is a measure of the ability of a material to absorb elastic energy
Toughness is the ability of the material to absorb all energy before fracture |
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What materials is creep important in? What materials is creep not so important in?
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Creep is very important in materials with low melting points such as polymers.
Creep is usually not important in metals with operating conditions under 800 F. |
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What can be said about graphs a-d?
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(a) Has significant work-hardening which is evident from t's continued ability to withstand increased stress until fracture.
(b) exhibits very little work hardening but the ductility allows it to continue to elongate. (c) Is extremely brittle with no ability to work harden (d) Ductile plastics undergo a reorganization and “orientation strengthening†at the atomic level before fracture |
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Chemical Properties
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Characteristics of a substance associated with it’s formulation and reactivity with other substances and environments
atomic/molecular structure, composition, corrosion characteristics (reactivity) |
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Service Life
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Intended service life of a product or structure should be determined prior to the design and selection of materials
Service life is affected by climate and the environment a material is subjected Materials must be chosen that can withstand the conditions for the design service life or the design should accommodate replacement or reconditioning |
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Mechanical Properties
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Durability and ability of a substance to withstand applied forces
hardness, strength, toughnes |
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Physical Properties
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Attributes that can be measured without destroying or altering the substance
thermal expansion, specific heat, density |
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Limitations of visual inspection
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can only find surface flaws large enough for and in view of the human eye
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Limitations of Dye penetrant
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used for smaller surface defects
no subsurface flaws not for porous materials |
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Limitations of Radiography
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used for subsurface flaws
smallest defect detectable is 2% of the thickness radiation protection needed |
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Limitations of Microscopy
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used for small surface flaws
not applicable to large structures no subsurface flaws |
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Limitations of Ultrasonics
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used for subsurface flaws
material must be a good conductor of sound |
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Limitations of Magnetic particle
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used for surface and near-surface flaws
limited subsurface capability only for ferromagnetic materials |
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Limitations of Eddy current
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Surface and near-surface flaws
difficult to interpret in some applications only for metals |
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Limitations of Acoustic emission
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used for analyzing entire structures
difficult to interpret expensive equipment |
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Gibbs Phase Rule
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F = C - P + 2
F= # of degrees of freedom that are allowed to change w/out changing # of phases C = # of components P= # of phases present 2= constant |
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3 Characteristics of Phases
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1. same composition roughly 2. same atomic arrangement and structure 3. definite bounding between phases
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Basic Oxygen Furnace
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refractory-lined vessel that cap tip and pour
charged with scrap, pig iron fluxing agents, and molten pig iron once the charge is melted, an oxygen lance is brought in to reduce the carbon, sulfur, and phosphorous after steel is poured, nitrogen is blown in to reduce refractory wear in charging constant burning |
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Electric Arc Furnace
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the source of heat is an arc that is established between the melt and graphite electrodes
can be shut down between uses and does not have to be kept hot to melt charge |
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Continuous cast steels
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deoxidized steels
user does not have to be concerned about ingot solidification practice |
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Hot-finished steels versus cold-finished
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Hot-finished steels have lower mechanical properties and do not work harden in manufacture- elevated work temperatures produce dynamic recrystallization
Hot-finishing only changes shape and does not strengthen Cold-finishing creates dislocations, is purely mechanical, and strengthens material |
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What concentration of iron do we rely on today?
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Since hematite and magnetite dwindled, we rely on taconite.
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If strength in hardness is increased:
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Ductility is decreased
Resistance to creep is increased Electric conductivity is decreased |
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Failure of Broken rack
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Ultimately caused by excess bending stress in the rack.
The bending stress could have been decreased by increasing the moment of inertia |
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Phase %=
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( length of opposite arm of lever / total length of tie line ) *100
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Annealing heat treating process
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consists of heating a steel to its austenitizing temperature and then cooling it at a slow enough rate to prevent the formation of a hardened structure
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Tempering heat treatment
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subcritical process used to improve the toughness of quench-hardened steels
As the tempering T increases: Impact strength and ductility increases, while tensile strength and hardness decreases |
