NUCL320 Exam 1

mechanical properties and crystal structure

Name of structure?

Name of structure?

simple cubic (SC)

Name of structure?

base centered cubic (BCC)

Name of structure?

face centered cubic (SCC)

Name of structure?

hexagonal close packed (HCP)

Steps to find direction indices for cubic structures

1. format: [###]

2. reposition vector to pass through origin

3. reduce x, y, and z coordinates to smallest integer values

family of direction indices: <###>

Steps to find direction indices for hexagonal structures

1. format: [####]

2. reposition vector to pass through origin

3. reduce x, y, and z coordinates to smallest integer values

family of direction indices: <###>

stress definition

force per unit area

strain definition

change in length over original length

elastic definition

reversible deformation, linear relationship between stress and strain

elastic modulus (young’s modulus)

a measure of a material’ stiffness, stress over strain

stiffness definition

stress divided by strain

plastic definition

permanent deformation, after tensile strength is reached, non-linear relationship between stress and strain

STREngth definition

the ability to withstand STREss without breaking

yield strength definition

the stress at which a material begins to permanently deform

tensile strength defintion

the maximum stress from stretching before a material breaks

ductility definition

the ability to deform without breaking

ductile fracture definition

elastic + plastic behavior

brittle fracture defintion

elastic behavior only

toughness definition

the ability to absorb energy without fracturing

hardness definition

the resistance to permanent surface deformation

concept of tensile testing

measuring mechanical properties through stretching a material

concept of strain hardening

increasing strength and hardness through plastic deformation

engineering stress equation

true stress equation

engineering strain equation

true strain equation

poisson’s ratio equation

percent elongation equation

hooke’s law equation

percent area reduction equation

toughness equation

force-separation curves: relationship between force and energy

force-separation curves: strongly bonded vs weakly bonded

poisson’s ratio value for which density increases

v > 0.5

poisson’s ratio value for which density decreases (voids form)

v < 0.5

(1)

elastic modulus (young’s modulus), the slope of the linear portion of the graph

(2)

yield strength, the value where the graph intercepts a line of the same slope but a +2% x-intercept

(3)

ultimate tensile stress, the maximum value of the graph

(4)

% elongation at fracture

(5)

toughness/total energy absorption, the area under the curve

the strength, ductility, and toughness at (1)

high strength

low ductility

low toughness

the strength, ductility, and toughness at (2)

moderate strength

moderate ductility

high toughness

the strength, ductility, and toughness at (3)

low strength

high ductility

low toughness