Week 2 Flashcards
Metal necking: deformation _________ occurs in ______ place
Concentration
One
(And why)
The one on the left
(%RA)
Ceramics have _______ and _______ bonds
(Do atoms move easily)
Covalent
Ionic
(Atoms don’t move easily)
List the 2 types of ceramics
Crystalline
Amorphous
What type of ceramic is this
Crystalline
What type of ceramic is this
Amorphous
Can atoms move past each other in ceramics?
(And explain)
NO
(Because of strong bonds)
Metallic bonds: atoms can usually _____
Slip
What type of shape is this called
FCC
What type of shape is this called
BCC
What type of shape is this called
HCP
Polymers: covalent bonds within ______, secondary bonds _______ chains
Chains
Connecting
Where do we see deformation in polymers
In the SECONDARY BONDS
Polymers: funny name for them is molecular ______
Spaghetti
(What class of materials is this) Describe what is happening at each stage
Polymers
1) undeformed
2) elastic deformation
3) increasing chain alignment
4) chain sliding
In metals, deformation is concentrated in the
________ ________
Necked region
Deformation: in POLYMERS the neck _________ through the entire ______ ______ length
Propagates
Reduced section
Tensile toughness can be found from a stress strain graph as what?
The area under the curve
Bruh
Strong bonds = ______ materials
Stiff
List the 5 types of bonds from strongest (stiffest) to least
1) covalent
2) metallic
3) ionic
4) hydrogen bond
5) Van der Waals
Strong bonds= ____ melting points
High melting points
List the three types of bonds from highest to lowest melting points
(Metallic, van der Waals, covalent)
Covalent
Metallic
Van der Waals
What does “Von Mises stress” refer to
Non-uniform stress states
What does non-uniform stress states mean
(And 2 examples)
Bi or tri axial stress
(Flaws, cracks)
Which two scales can stresses be complex at
Macro scale
Micro scale
Micro or macro stress scale?
Macro
Micro or macro stress scale?
Micro
Where is the gauge width on a dog bone
Where is the overall width on a dog bone
What is the specimen length of the dog bone
DUCTILITY DEPENDS ON: gauge ______
Length
How are hardness measurements done
Apply know force, measure depth or width of indent
What does HB and HBR stand for
HB: Brinell hardness
HBR: Rockwell B scale
Does hardness testing or tension testing give us MORE information
Tension testing
Why would we do hardness testing (if tension testing gives us more info)
List 6 things
Cheaper
Faster
Easy to interpret
Mostly non destructive
No machining
Localized variations in properties
What else can cause variations in mechanical testing (apart from compositional variations)
List 4 things
-machining variations
-operating bias
-calibration
-inhomogeneities
What does “inhomogenieites” refer to
And list 3 examples
No material is uniform
(Cracks, inclusions, localized composition variations)
What does the safety factor have to be GREATER than
1
Brittle materials: the worst flaw dictates _____
Strength
Why are smaller ceramics stronger (in tension)
Small sample has on average smaller flaws
Ceramics: what is greater bending strength or tensile strength
Bending strength
Where is the largest flaw in this ceramic
The longest line
Where is the max tension in this ceramic
In the middle
Failure can occur over a _______ of stresses
RANGE
What does the Weibull distribution graph look like
(And key value on it)
m=Wiebull modulus
Weibull distribution graph: where are low m values and what do they mean
Wide variability, m=5 for chalk, cement, bricks)
Weibull distribution graph: where are high m values and what do they mean
Little variability in materials
Wiebull distribution graph: what does it mean if m>20
What is the approximate probability of survival (Weibull distribution)
36%
What is this variable on the Weibull distribution graph
Reference stress where survival probability is 1/e
What are the 3 factors of wear rate
Is wear rate intrinsic or extrinsic and why
HIGHER values of the Archard wear constant mean what?
Faster wear
What is the red (middle largest) area on the west rate constant vs hardness graph
Metals
What is the blue area (furthest to the left) on the wear rate constant vs hardness graph
Polymers and elastomers
What is the green area (furthest to the right) on the west rate constant vs hardness graph
Technical ceramics
What are thermoplastics
Plastics that MELT
______ particles cause implant failures
Wear
Give 3 examples of wear
Poisson’s ratio: only applies to _______ deformation
(And why)
ELASTIC
During plastic deformation the volume is constant
What can you find with Poisson’s ratio?
Strains
Define creep
The slow and gradual deformation of materials, often caused by constant stress or a load over an extended period
Give an example of creep
Deformation of metals
What does the Weibull distribution show
Models the time until failure occurs
