Exam 1 Material Techology

Atomic mass

The total mass of an atom, primarily the sum of protons and neutrons.

Isotopes

Atoms of the same element with different numbers of neutrons.

Types of chemical bonds

Ionic, covalent, and metallic bonds.

Lattice structure

A repeating three-dimensional arrangement of atoms in a crystal.

Alloys

Mixtures of elements forming a single phase, either substitutional or interstitial.

Vacancies

Vacancies can ease dislocation movement, making deformation easier.

Homogeneous region

A region of material with uniform structure and properties.

Eutectic vs. complete solubility

Eutectic diagrams have limited solubility and distinct phase boundaries, while complete solubility allows full mixing.

ASTM International

An organization that develops and publishes consensus technical standards.

Accuracy vs. precision

Accuracy is how close a measurement is to the true value, while precision is how consistently measurements are repeated.

Mechanical properties

Determining mechanical properties like yield strength, tensile strength, and modulus of resilience.

Stress formula

σ = F / A (Force divided by area).

Poisson's ratio

The ratio of lateral strain to axial strain.

Elasticity vs. plasticity

Elasticity is reversible deformation; plasticity is permanent deformation.

Static vs. dynamic loading

Static loading applies force slowly, while dynamic loading involves sudden or cyclic forces.

Brittle vs. ductile fractures

Brittle fractures have sharp, clean breaks, while ductile fractures show necking and deformation.

Hardness tests

Brinell, Rockwell, and microhardness tests.

allotrope

a different structural form of the same element in the same physical state. For example, diamond and graphite are allotropes of carbon

nucleus

the central region of an atom that contains protons and neutrons and carries a positive charge

proton

a positively charged subatomic particle found in the nucleus of an atom. It determines the atomic number of the element

neutron

electrically neutral subatomic particle located in the nucleus of an atom that contributes to the atomic mass

electron

a negatively charged subatomic particle that orbits the nucleus and plays a key role in chemical bonding

ion

an atom or molecule that has gained or lost one or more electrons, giving it a net positive or negative charge

valence electron

an electron in the outermost electron shell of an atom that is involved in chemical bonding

ionic bonds

Involve the transfer of electrons and electrostatic attraction between oppositely charged ions

covalent bonds

Involve the sharing of electrons between atoms to achieve stability.

intermolecular bonds

forces that occur between molecules. These include hydrogen bonds, Van der Waals forces, and dipole-dipole interactions, and are generally weaker than the primary (chemical) bonds within molecules.

metallic bonds

the sharing of free electrons among a lattice of metal atoms, allowing conductivity and malleability.

mixture

a physical combination of two or more substances in which each substance retains its own chemical properties and can be separated by physical means

molecule

a group of two or more atoms held together by chemical bonds

What is a crystal structure?

A crystal structure is the ordered, repeating arrangement of atoms in a material.

What are common crystal structures?

Common crystal structures include Face-Centered Cubic (FCC), Body-Centered Cubic (BCC), and Hexagonal Close-Packed (HCP).

What are solid solutions?

Solid solutions are homogeneous mixtures of two or more elements where atoms of the solute occupy positions in the solvent's crystal lattice.

What is slip in materials science?

Slip is the process by which dislocations move through a crystal lattice, allowing deformation.

How do vacancies affect slip?

Vacancies can sometimes ease slip by providing pathways for dislocation movement, though they may also cause local weaknesses.

key standards organizations in materials science

ASTM, ISO, SAE

accuracy

how close a measured value is to the true or accepted value

precision

the repeatability or consistency of measurement results

reliability

the consistency and dependability of measurement results over time

significance

the importance or impact of a measurement's deviation from the true value

common sources of error in measurements

instrument error, environmental factors, and human error

classes of error

systematic errors (consistent bias) or random errors (variability)

What is tensile testing

a method used to determine how a material reacts to forces applied in tension

Young’s modulus (elastic modulus)

the ratio of stress to strain in the elastic region. Units: Pascals (Pa) or psi

yield strength

the stress at which a material begins to deform plastically. Units: Pascals (Pa) or psi

tensile strength

the maximum stress a material can withstand before necking or failure. Units: Pascals (Pa) or psi

elastic limit

the maximum stress that a material can withstand without permanent deformation

the proportional limit

the maximum stress at which the stress-strain relationship remains linear

Poisson’s ratio

the ratio of lateral (transverse) strain to axial (longitudinal) strain when a material is stretched

strain hardening (work hardening)

the process by which a material becomes stronger and more resistant to deformation as it is plastically deformed

the yield point

the stress level at which a material begins to deform permanently

necking down

the localized reduction in cross-sectional area of a specimen under tensile load

stress

the force per unit area applied to a material (σ = F/A)

strain

the measure of deformation given by the ratio of change in length to the original length (ε = ΔL/L₀)

elongation

the change in length (ΔL = L - L₀) or as percentage elongation (ΔL/L₀ × 100%)

reduction in area

(A₀ - A)/A₀ × 100%, where A₀ is the original cross-sectional area and A is the final area

elasticity

the property of a material to return to its original shape after the removal of a load

plasticity

the ability of a material to undergo permanent deformation when a load is applied

ductility

a material's ability to undergo significant plastic deformation before fracture

static loading

to forces applied slowly and steadily over time

dynamic loading

forces that are applied rapidly or cyclically, which can lead to fatigue

toughness

the ability of a material to absorb energy and plastically deform before fracturing, usually measured as the area under the stress-strain curve

fatigue

the progressive, localized structural damage that occurs when a material is subjected to cyclic loading