# Shared Flashcard Set

## Details

Material Science
Chapter 6
22
Mechanical Engineering
10/16/2012

Term
 Engineering Stress
Definition
 Sigma = F/ Ao; where F is the instantaneous load applied perpendicular to the specimen cross section (N) or pounds force (lbf). Ao is the original cross-sectional area before any load is applied (m^(2) or in^(2))
Term
 Engineering Strain (weird e shape)
Definition
 change in l / lo or li - lo / lo; lo is the original length before any load is applied and li is the instantaneous length. No units.
Term
 Shear Stress
Definition
 weird r = F / Ao; F is the load or force imposed parallel to the upper and lower faces, each of which has an area of Ao.
Term
 Hooke's Law
Definition
 sigma = Ee
Term
 Modulus of elasticity (Young's modulus)
Definition
 The constant of proportionality E
Term
 Elastic Deformation
Definition
 Stress and Strain are proportional; a plot of stress (ordinate) versus strain (abscissa) results in a linear relationship
Term
 Relationship between shear stress and shear strain for elastic deformation
Definition
 r = G*gamma
Term
 Anelasticity
Definition
 Elastic deformation will continue after the stress application and upon load release some finite time is required for complete recovery.
Term
 Poisson's ratio in terms of lateral and axial strain
Definition
 v = -(ex/ez) = -(ey/ez)
Term
 Relationship among elastic parameters, modulus of elasticity, shear modulus, and Poisson's ratio
Definition
 E = 2G(1+v)
Term
 Plastic deformation
Definition
 For most metallic materials, elastic deformation persists only to strains of about 0.005. As the material is deformed beyond this point, the stress is no longer proportional to strain and permanent and nonrecoverable allowing this to occurs.
Term
 Yielding
Definition
 It is therefore desirable to know the stress level at which plastic deformation begins.
Term
 Proportional limit
Definition
 For metals that experience this gradual elastic-plastic transition, the point of yielding may be determined as the initial departure from linearity of the stress-strain curve.
Term
 Yield Strength
Definition
 The stress corresponding to the intersection of this line and the stress-strain curve as it bends over in the plastic region.
Term
 Tensile Strength
Definition
 The stress at the maximum on the engineering stress-strain curve.
Term
 Ductility
Definition
 It is a measure of the degree of plastic deformation that has been sustained at fracture.
Term
 Brittle
Definition
 A metal that experiences very little or no plastic deformation upon fracture.
Term
 Resilience
Definition
 The capacity of a material to absorb energy when it is deformed elastically and then upon unloading to have this energy recovered.
Term
 Toughness
Definition
 A mechanical term that may be used in several contexts. This is a property that is indicative of a material's resistance to fracture when a crack is present.
Term
 True Stress
Definition
 Defined as the load F divided by the instantaneous cross-sectional area Ai; sigma T = F/Ai
Term
 True Strain
Definition
 et = ln (li/lo)
Term
 Hardness
Definition
 A mechanical property that is the measure of a material's resistance to localized plastic deformation.
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