Chapter 4 & 5 Materials Flashcards
Brittle
A material that does not plastic ally deform before breaking Breaks suddenly as cracks travel through it
Strong
A material that can withstand large amounts of stress before breaking
Tough
A material that undergoes considerably plastic deformation before breaking. In this process it will also absorb a lot of energy before breaking
Stiff
Small strains for large stresses Large Young modulus Not stretchy or bendy
Elastic
Returns to unstretched form when stresses are removed
Plastic
Undergoes permanent deformation under large stresses rather than cracking
Hard
Resists indentation on impact
Limit of proportionality
Point beyond which stress and strain are no longer proportional Hooke’s law does not apply
Yield point
Point at which strain increases rapidly
Ultimate Tensile Strength UTS
Stress at which a material breaks
Ductile
Can be drawn out into wires Undergoes considerable plastic deformation before breaking
Hysteresis loop
Loading and unloading cycle for rubber Area of the loop equals the energy per unit volume transferred to heat inside the rubber
What structure does this material have
Amorphous
What structure does this material have?
Crystalline
What structure does this material have
Polycrystalline
What does SEM stand for
A type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. SEM can achieve resolution better than 1 nanometer.
What does AFM or SFM stand for?
Atomic force microscopy (AFM) or scanning force microscopy (SFM)
a very high-resolution type of scanning probe microscopy, with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit
What is a composite material
- A broad definition of composite is: Two or more chemically distinct materials which when combined have improved properties over the individual materials. Composites could be natural or synthetic
- Composites are combinations of two materials in which one of the material is called the reinforcing phase, is in the form of fibers, sheets, or particles, and is embedded in the other material called the matrix phase.
vWhat is the concept / purpose of a composite material?
- The essence of the concept of composites is that the load is applied over a large surface area of the matrix. Matrix then transfers the load to the reinforcement, which being stiffer, increases the strength of the composite.
- It is important to note that there are many matrix materials and even more fiber types, which can be combined in countless ways to produce just the desired properties.
List 3 advantages of composite materials
- Higher Specific Strength (strength-to-weight ratio) Design flexibility
- Corrosion Resistance
- Low Relative Investment
- Durability
Name the 4 classes of materials
Metals
Ceramics
Polymers
Composites
Describe how a crystal forms
- The moment a crystal begins to grow is know as nucleation and the point where it occurs is the nucleation point.
- At the solidification temperature, atoms of a liquid, such as melted metal, begin to bond together at the nucleation points and start to form crystals.
- The final sizes of the individual crystals depend on the number of nucleation points.
- The crystals increase in size by the progressive addition of atoms and grow until they impinge upon adjacent growing crystal.
Describe the difference between a crack in a brittle vs plastic material
BRITTLE - microscopic flaws (crack) will tend to elongate rather induce plastic deformation when a stress is applied.
PLASTIC - cracks tend to emit dislocations and become more blunt as the raft is stressed
A large fracture energy means the material is…..
TOUGH
Which leads to a stronger material, larger or smaller grain size?
Dislocations can travel easily inside a crystal grain
When they reach grain boundary they cannot move further
More grain boundaries = stronger material
What is doping?
✤To make a semi conductor conduct electricity, other atoms (impurities) must be added
✤The impurities are different elements
✤This process is called doping
Which shows the limit of proportionality?
A
Which shows the yeild point?
B (upper yield point) and C (lower yield point)
Which shows the ultimate tensile strength (UTS)?
D
Which shows the breaking stress?
E
