Material Science Exam 1 Vocab 2

Lattice

 A collection of points that divide space into smaller equally sized segments

Lattice parameter

the axial lengths or dimensions of the unit cell and are denoted by convention as a, b, and c

Basis

A group of atoms associated with a lattice point

Crystal structure

The arrangement of the atoms in a material into a regular, repeatable lattice. A crystal structure is fully described by a lattice and a basis

Unit cell

A subdivision of the lattice that still retains the overall characteristics of the entire lattice

Inner-atomic spacing

the distance between the centers of two adjacent atoms within a material

Atomic radius

The apparent radius of an atom, typically calculated from the dimensions of the unit cell, using close-packed directions

Atomic %

expressing the concentration of an element within a material based on the number of atoms of that element relative to the total number of atoms present

Weight %

the proportion of a specific component within a material, expressed as a percentage of the total weight of the material

Tensile test

measures the resistance of a material to a static or slowly applied force

Charpay impact test

a standardized test that measures how much energy a material absorbs during fracture

Yield strength (0.2% offset)

the level of stress needed to initiate plastic deformation

Ultimate tensile strength

The maximum stress on the engineering stress strain curve

Elongation at break %

quantifies the permanent plastic deformation at failure

Modulus of elasticity

the slope of the stress strain diagram

Elastic strain

fully recoverable strain resulting from an applied stress

Plastic strain

permanent deformation of a material when a load is applied, then removed

Engineering stress

The applied load, or force, divided by the original area over which the load acts

True stress

The load divided by the instantaneous area over which the load acts

Necking

Local deformation causing a reduction in the cross-sectional area of a tensile specimen. Many ductile materials show this behavior. The engineering stress begins to decrease at the onset of necking

Poisson’s ratio

The negative of the ratio between the lateral and longitudinal strains in the elastic region

Charpay impact toughness

the amount of energy a material absorbs when fractured under a sudden impact load

Thermoplastic

the long molecular chains are not rigidly connected, have good ductility and formability

Thermoset

stronger but more brittle because the molecular chains are tightly linked

Degree of polymerization

the number of repeat units in the chainegree of polymerization=average molecular weight of polymer molecular/weight of repeat unit

Cross-linking

the process whereby two or more molecules are chemically joined by a covalent bond

Co-polymer

a polymer formed by the combination of two or more different monomer units