Flashcards in Physical Properties Deck (34)
Define the words
by using them in the same sentence.
A load is applied to a material which exerts a force on the material which produces a stress within a material and
What are the units for Load?
What are the units for Force?
Name 3 types of forces
- Uniaxial (single axis)
- Biaxial (2 perpendicular axis)
- Triaxial (equal in all directions)
Name 3 uniaxial forces
What are the units for stress?
What are the units for strain?
What is the measure of stiffness
Young's modulus (E)
State Hooke's Law
Stress (σ) is proportional to strain (ε)
What is compliance a measure of?
- 1/E (reciprocal to stiffness)
What is the proportional limit on an stress-strain curve?
The limit when even if the load is removed the material is permanently damaged
What is the ultimate tensile strength on an stress-strain curve?
The fracture point where the material breaks apart
What is the yield point on an stress-strain curve?
The point above which strain will increase even with no further increase in stress
What is the elastic region on an stress-strain curve?
Region where, if stress is removed the original shape is recoverable
What is the plastic region on an stress-strain curve?
Region where, if stress is removed the material is permanently deformed
Energy absorbed without permanent deformation
Total energy absorbed up to fracture
Equation for Poisson's ratio
Lateral strain / Axial strain
Equation for Shear modulus
Shear stress / Shear strain
Equation for Bulk modulus (liquids)
Hydrostatic pressure / Shear strain
What is a brittle fracture?
- Occurs with little or no plastic deformation
- Low energy absorption
What is a ductile fracture?
- Occurs after significant plastic deformation
- High energy absorption
What are the 2 steps in a fracture?
- Crack formation (slow)
- Crack propagation (fast)
How is direct tensile strength measured?
By gauges and extensometers
When measuring direct tensile strength what shape does the specimen need to be in? Why?
- Dumbbell shaped
- Ensures it fractures centrally
What is the direct tensile strength test used for?
- Rigid polymers
- Rubbery polymers
What is the compressive strength test used for?
- Hard polymers
- Dental cements
What is the diametral tensile strength test used for?
- Brittle materials
What is the diametral tensile strength test NOT used for?
- Ductile materials