EIT/FE MaterialScience Flashcards
What is steel?
Steel is an iron alloy that contains up to 1.5% carbon and small amounts of other elements.
Ferrous Metals
What are Ferrous Metals?
Metals containing a large percentage of iron.
What other elements are used in steel
Steel often includes manganese, chromium and nickel.
Stress Definitions;
Cauchy strain or Engineering strain
Yield strength
ultimate tensile strength
Elasticity
Plasticity
Cauchy strain or engineering strain is expressed as the ratio of total deformation to the initial dimension of the material body in which the forces are being applied.
Yield strength is the lowest stress that produces a permanent deformation in a material
ultimate tensile strength is a limit state of tensile stress that leads to tensile failure in the manner of ductile failure aka Engineering stress
Elasticity is the ability of a material to return to its previous shape after stress is released.
Plasticity or plastic deformation is the opposite of elastic deformation and is defined as unrecoverable strain
Hookes Law - used to determine elastic range
σ = E * ε
σ = E * ε
σ = stress
ε = strain
E = Youngs modulus / modulous of elasticity
Ductility
Strength
Maleability
Hardness
Elasticity
Toughness - measured by area under stress-strain curve
Ductility The ability of a material to be stretched or drawn into a wire by a tensile force without fracturing.
Strength The ability of a material to withstand a loader force without failure.
Maleability The ability of a material to be flattened by a compressive force without falling.
Hardness The ability of a material to resist scratching and indentation.
Elasticity The ability of a material to return to its original position and /or shape after the removal of the deforming force.
Toughness a material’s resistance to fracture when stressed
Compressive strength- some amterails can be brittle but have great compressive strength (ie cast iron and concrete)
Fatigue - starts at surface and initiates a crack
Endurance Limit - no enduace limit for AL and non-ferrous alloys
Compressive strength compressive strength is the capacity of a material or structure to withstand loads tending to reduce size.
Fatigue the weakening of a material caused by repeatedly applied loads. It is the progressive and localized (surface) structural damage that occurs when a material is subjected to cyclic loading.
Endurance limit the amplitude (or range) of cyclic stress that can be applied to the material without causing fatigue failure.
Failure Modes
Plastic Flow
Creep
Creep is the tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses.
Edge Dislocation - can cause experimental value of critical resolved shear stress to be 5 times smaller than theoretical
Cold Work will increase number of dislocations
Edge Dislocation a defect where an extra half-plane of atoms is introduced mid way through the crystal, distorting nearby planes of atoms
Cold Work increases yield strength
