MSE 2101 Exam 2 VOCAB

slip plane

crystallographic planes for dislocation movement

Slip Direction

Direction of easiest atomic movement

Critical resolved shear stress

Minimum shear stress needed for slip

Dislocations

Line defects enabling plastic deformation

Fracture

Material separation due to stress

Transgranular

Crack travels through grains

Intergranular

Cracks travel along grain boundaries

Ductile

Material with high plastic deformation before breaking

Brittle

Material that fractures with minimal deformation

Fatigue

Failure from cyclic stress below yield strength. (Crack growth during fatigue incremental)

Creep

Time-dependent deformation under constant load

Primary Creep

initial stage of creep, starts at a rapid rate and slows with time

Secondary Creep

steady-state i.e., constant slope

Tertiary Creep

creep rate increases with time leading to necking and fracture

Strengthening Mechanisms

Cold working/Work Hardening, Solid Solution Strengthening, Hall-Petch, Precipitation Hardening

cold working (work hardening)

rolling or drawing flattens and stretches grains resulting in fibrous structure

Solid Solution Strengthening

lattice strain causes drag effect on dislocations

Hall-Petch

Strengthening from Reducing Grain size

Precipitation Hardening

Pins dislocations since difficult to shear

Youngs Modulus

Stiffness in elastic region

Elastic Strain

deformation that recovers once stress removed

Plastic strain

Permanent deformation that occurs after yielding

Toughness

Total energy absorbed before fracture, area under stress curve

Yield Stress

Stress at the transition from elastic to plastic deformation

Ultimate Tensile Stress

Maximum stress before fracture