Materials of Engineering CH6,7 Test Vocab

Hot Working of Metals

permanent deformation of metals and alloys above the temperature at which a strain-free microstructure is produced continuously

Cold Working of Metals

permanent deformation of metals and alloys below the temperature at which strain-free microstructure is produced continuously

Annealing

a heat treatment used on a metal to soften it

Extrusion

a plastic-forming process in which a material under high pressure is reduced in cross section by forcing it through an opening in a die

Forging

a primary-processing method for working metals into useful shapes in which the metal is hammered or pressed into shape

Wire Drawing

a process in which wire stock is drawn through one or more tapered dies to the desired cross section

Deep Drawing

a metal-forming process for shaping flat sheets of metal into cup-shaped articles

Elastic Deformation

if a metal deformed by a force returns to its original dimensions after the force is removed

Engineering Stress

average uniaxial force divided by the original length of sample

Engineering Strain

change in length of sample divided by the original length of sample

Shear Stress

shear force S divided by the area A over which the shear force acts

Shear Strain

shear displacement a divided by the distance h over which the shear acts

Engineering Stress-Strain Diagram

experimental plot of engineering stress versus engineering strain

Modulus of Elasticity, E

stress divided by strain in the elastic region of an engineering stress-strain diagram for a metal

Yield Strength

the stress at which a specific amount of strain occurs in the engineering tensile test

Ultimate Tensile Strength (UTS)

the maximum stress in the engineering stress-strain diagram

Hardness

a measure of the resistance of a material to permanent deformation

Slip

the process of atoms moving over each other during the permanent deformation of a metal

Slipbands

line markings on the surface of a metal due to slip caused by permanent deformation

Slip System

a combination of a slip plane and a slip direction

Deformation Twinning

A plastic deformation process that occurs in some metals and under certain conditions. In this process, a large group of atoms displaced to form a region of a metal crystal lattice that is a mirror image of a similar region along a twinning plane

Hall-Petch Relationship

an empirical equation that relates the strength of a metal to its grain size

Strain Hardening

the hardening of a metal or alloy by cold working. During cold working, dislocations multiply and interact, leading to an increase in the strength of the metal

Solid-Solution Hardening

strengthening a metal by alloying additions that form solid solutions. dislocations have more difficulty moving through a metal lattice when the atoms are different in size and electrical characteristics, as is the case with solid solutions

Recovery

the first stage in the annealing process that results in removal of residual stresses and formation of low-energy dislocation configurations

Recrystallization

the second stage of the annealing process in which new grains start to grow and dislocation density decreases significantly

Grain Growth

the third stage of the annealing process in which new grains start to grow in an equiaxed manner

Annealing

a heat-treatment process applied to a cold-worked metal to soften it

Superplasticity

the ability of some metals to deform plastically by 1000% to 2000% at high temperatures and low loading rates

Nanocrystalline Metals

metals with grain size smaller than 100 nm

Ductile Fracture

a mode of fracture characterized by slow crack propagation. ductile fracture surfaces of metals are usually dull with a fibrous appearance

Brittle Fracture

a mode of fracture characterized by rapid crack propagation. brittle fracture surfaces of metals are usually shiny and have a granular appearance

Transgranular Fracture

a type of brittle fracture in which the crack propagates across the grain

Intergranular Fracture

a type of brittle in which the crack propagates along the grain boundary

Ductile-To-Brittle Transition (DBT)

observed reduced ductility and fracture resistance of a material when temperature is low

Surface Energy per Unit Area

the energy associated with the surface created as a result of fracture

Theoretical Strength

fracture strength in a flawless body (without defects), determined by basic principles

Stress Concentration Factor

the amplification of stress influenced by the geometry of the component and the defect, represented by the ratio of maximum stress to far field or normal stress

Fracture Toughness

the critical value of stress intensity factor, a material property, at which a preexisting crack extends and the plate fails

Fatigue

the phenomenon leading to fracture under repeated stresses having a maximum value less than the ultimate strength of the material

Fatigue Failure

failure that occurs when a specimen undergoing fatigue fractures into two parts or otherwise has been significantly reduced in stiffness

Fatigue Life

the number of cycles of stress or strain of a specific character that a sample sustains before failure

Fatigue Crack Growth Rate

the rate of crack growth extension by constant amplitude fatigue loading

Creep

time-dependent deformation of a material when subjected to a constant load or stress

Creep Rate

the slope of the creep-time curve at a given time

Creep-Rupture Strength

the stress that will cause fracture in a creep test at a given time and in a specific environment at a particular temperature

LM Parameter

a time-temperature parameter used to predict stress rupture due to creep