MSE 2001 Flashcards
Mechanical Property related to resistance of bending.
Elastic Stiffness/Elastic Modulus
The mechanical property which measures the ease of which an object is permanently bent- Represented by lowercase sigma with a subscript y.
Yield Strength
Mechanical Property for a metal which measures resistance to fracturing/breaking (K1c).
Fracture Toughness
Mechanical Property related to amount metal can be stretched before being broken.
Ductility
Thermal Property related to how much a material sags over time due to temperature change.
Creep
Thermal Property related to limiting temperature which a material can be used at.
Maximum Service Temperature.
Thermal Property related to amount which material expands when heated. Represented with lowercase alpha.
Thermal Expansion Coefficient
Thermal Property related to the rate as which heat flows through material from hot area to cold area.
Thermal Conductivity
Amount of heat is takes a material’s temperature to rise by given amount.
Heat Capacity
Thermal Property related to time for material to melt after heat is first applied. Proportional to Thermal Conductivitiy/Heat Capacity.
Thermal Diffusivity
Electrical Property related to ability for electricity to flow through material.
Electrical Conduction
Material’s ability to limit and slow down rate of electrical flow through it.
Insulators
Measures resistance to flow of electricity/slower rate.
Resistivity
Property related to a materials response to an electric field being enforced upon it.
Dielectric Properties
Materials with capacity to trap magnetic field permanently. Hard to demagnetize.
Ferromagnets/Ferrimagnets
Measure of intensity of retained magnetism.
Remanence
Idea that performance of material is limited to properties of materials.
Design Limiting Properties
Force per area applied to a material when it is loaded in a certain way.
Stress
Change of material orientation as a result of stress.
Strain
Resistance to change of shape by stress when object is still elastic.
Stiffness
Resistance to permanent deformation by stress
Strength
Measured by mass per unit volume of material. Reflects mass and orientation of atoms in material.
Density.
Stresses applied normal to face of material and on axis. They are in opposite directions.
Tension/Compression
Stress parallel to face of object caused by torsion.
Shear Stress
Applies to uniform shape that has equal/tensile/compressive force on all areas. Positive when pushing.
Hydrostatic Pressure
Reaction to tensile stress measured as
(change in length/length). Negative for compressive stress
Tensile/Compressive STrain
Law that states that stress and strain are proprotionally linear up to yield strength and strain is recoverable. Measured as
Stress =(Young’s Modulus) * Strain
Hooke’s Law
Constant representing proportion between tensile/compressive stress and tensile/compressive strain.
Young’s Modulus
Constant telling proportion between shear stress and shear strain.
Shear Modulus
Constant representing pressure and dilation (or strain from pressure).
Bulk Modulus
What are the properties of silicone at low temperatures, high temperatures, and very high temperatures?
Low Temperatures- Insulator
High Temperatures- Semi-Conductor
Very High Temperatures- Metal/Conductor
Happens when metal is cooled to certain temperature, causing zero electrical resistance
Superconductor
Why does applying high pressure to a gas lead it to be liquified?
Assuming temperature is constant, high pressure causes distance between atoms in molecule to decrease, leading to more intermolecular bonds forming.
What are the four scales of structures? What is the scale unit of each?
Macroscopic (10^-5)
Microscropic (10^-6)
Atomic (10^-9)
Electronic (10^-10)
What is the unit called indicating 10^-10 that is the smallest scale a material can be looked at?
Angstrom.
What are the some characteristics of metals
o High Stiffness
o When pure, soft/easily deformed.
Made strong through alloying while remaining ductile.
High fracture toughness.
o Weaknesses- Reactive, corrode rapidly if not protected.
o Good electrical/thermal conductors
What are some characteristics of ceramics
o Structure- Crystalline of ionic and covalent bonds
Attractive features.
o Stiff, hard, and abrasion resistant.
o Retain strength to high temperature and resist corrosion well.
o Good electrical insulators.
o Weaknesses- Brittle with low fracture toughness.
Low tolerance for stress.
What are some characteristics of glasses?
o Lack of crystal structure lesses plasticitiy or deformation, meaning their hard and corrosion resistant.
Good electrical insulators and transparent to light.
o Weaknesses- Brittle meaning low tolerance for stress.
What are some characteristics of polymers
o Light in weight and low density.
o Low stiffness.
o However, strong b/c of low density meaning hard to deform.
o Properties dependent on room temperature.
Tough/Flexible at room temperature, brittle at -4 C, rubbery at 100C of boiling water.
* Some have useful strength about 150 C.
o Easy to shape- Good for components that snap together.
Strong bonds of sheets but weak bonds between sheets.
What is an elastomer?
- Elastomers- Polymers with extremely low stiffness (500-5000 times less than metals as opposed to 50 times less in stiffness for polymers).
What is a composite/hybrid material?
- Hybrids- Combination of Two or More materials
o Carbon Fiber and glass.
o Materials of nature (wood, bone, skin, etc.) are hybrids
Bones are mix of collagens (polymer) and hydroxyapatite(mineral).
o High Cost as difficult to form and join.
What are the different thermal processing and effects on steel?
If slowly cooled from high temperature, steel will be soft and have low strength.
If rapidly cooled, steel is extremely hard and brittle.
However, if rapidly cooled and reheated to moderate temperature, good combination of strength and toughness.
What is quantum mechanic theory
Electrons exhibit both wave and particle characteristics
Schrodinger’s Equation
Equation which describes electron wave motion in terms of energy levels and wave orientation.
Pauli’s Exclusion Principle
Each electron has unique set of four quantum numbers, due to the repulsion by each electron on each other if in close proximity.
Ionic Bonds
Electron Transfer between two atoms with high difference in electronegativity.
Attraction occurs between ionic core of nucleus and valence electron of other atom.
Repulsion occurs when ions get closer together due to core electrons in each.
Covalent Bonds
Created between two electronegative elements, meaning both attract ions.
Develops through attraction between negatively charged shared electron and positively charged nuclei.
Repulsion occurs when core electrons begin to overlap.
Metallic Bonds
Solids composed of electropositive elements where electrons are shared by all atoms in compound.
Valence electron forms cloud/sea of electrons surrounded by ion core.
Attraction comes from positively charged ion core and negatively charged electron cloud.
Repulsion occurs when electron shells of ion cores overlap.
