Hardness testing - localized deformation Brinell Vickers Knoop Rockwell Hardness/tensile strength correlation Impact testing - energy absorbed upon fracture Effect of temperature Last class
Jan 17, 2016
Hardness testing - localized deformationBrinellVickersKnoopRockwell
Hardness/tensile strength correlation
Impact testing - energy absorbed upon fractureEffect of temperature
Hardness testing - localized deformationBrinellVickersKnoopRockwell
Hardness/tensile strength correlation
Impact testing - energy absorbed upon fractureEffect of temperature
Last classLast class
More mechanical testingFracture toughnessFracture surfacesCreepFatigue
Crystal structure
More mechanical testingFracture toughnessFracture surfacesCreepFatigue
Crystal structure
TodayToday
Fracture toughness - KIc = Yc a
resistance to brittle fracture in presence of
a crack - resistance to crack propagationunder load
Fracture toughness - KIc = Yc a
resistance to brittle fracture in presence of
a crack - resistance to crack propagationunder load
Common specimen configurations
pre-cracked here before testing - usually 1000 cycles, 0.03 in/in strain
Common specimen configurations
pre-cracked here before testing - usually 1000 cycles, 0.03 in/in strain
Fracture toughness
Hypothetical example - surface crack in a semi-infinite sheet loaded in tension
Find critical crack size
Fracture toughness
Hypothetical example - surface crack in a semi-infinite sheet loaded in tension
Find critical crack size
Some fracture surfacesSome fracture surfaces
ductile fractureductile fracture
transgranularfracture
transgranularfracture
intergranularfracture
intergranularfracture
Crack originsCrack origins
Creep
deformation under small loads atelevated temps.
Creep
deformation under small loads atelevated temps.
Fatigue
deformation under small cyclic loads
Fatigue
deformation under small cyclic loads
Fatigue
S-N curves & endurance limit
Fatigue
S-N curves & endurance limit
Fatigue failure
fatigue crack w/ beachmarks
Fatigue failure
fatigue crack w/ beachmarks
Crystal structures of materials - where are the atoms?
Polymers - mostly not crystallinestructure extremely complicated
Ceramic materials - complicatedmany different types of atom arrangements
Crystal structures of materials - where are the atoms?
Polymers - mostly not crystallinestructure extremely complicated
Ceramic materials - complicatedmany different types of atom arrangements
Metals - really simple - most have one of three typesMetals - really simple - most have one of three types
Crystal structures of pure metalsCrystal structures of pure metals
Most pure metals exhibit one of three types
1. cubic close packing (ccp or A1)2. hexagonal close packing (hcp or A3)3. A2 (almost universally referred to by
the confusing notation 'bcc')
Most pure metals exhibit one of three types
1. cubic close packing (ccp or A1)2. hexagonal close packing (hcp or A3)3. A2 (almost universally referred to by
the confusing notation 'bcc')
Crystal structures of pure metals
cubic close-packed (ccp)
close-packed plane of atoms
Crystal structures of pure metals
cubic close-packed (ccp)
close-packed plane of atoms
Crystal structures of pure metals
cubic close-packed (ccp)
ABCABC layer sequence close-packed plane of atoms
Crystal structures of pure metals
cubic close-packed (ccp)
ABCABC layer sequence close-packed plane of atoms
AB
C
A
AB
C
Crystal structures of pure metals
hexagonal close-packed (hcp)
Crystal structures of pure metals
hexagonal close-packed (hcp)
Zn, Cd, Co, Ti, Zr……Zn, Cd, Co, Ti, Zr……
close-packed plane of atoms
hexagonhexagon
Crystal structures of pure metals
hexagonal close-packed (hcp)
ABAB layer sequence close-packed plane of atoms
Crystal structures of pure metals
hexagonal close-packed (hcp)
ABAB layer sequence close-packed plane of atoms
AB
AB
AB
Fe, V, Cr, Mo, W, Ta……Fe, V, Cr, Mo, W, Ta……
Crystal structures of pure metals
A2 structure - so-called "bcc" metal structure
almost close-packed atom planes
Crystal structures of pure metals
A2 structure - so-called "bcc" metal structure
almost close-packed atom planes
some empty space some empty space