Terms for chapter 4 for as physics book Flashcards
What is the equation for stress?
Force
Stress= –––––––
Area
Units of stress are?
Nm^2 often called pascal
Describe the several types of stress
Tension(stretching), compression, torsion(twisting)
Units of strength?
Pa
What does strong mean?
A large stress is needed to cause failure.
What does strength mean?
The maximum stress a material can withstand before failure.
What does weak mean?
Opposite of strong
What are the units for toughness?
J/m^2
What happens when some materials are stressed past their elastic limit?
They undergo some plastic deformation before breaking, in so doing, they absorb a large amount of energy before they break.
Strictly, Toughness is defined as what two things?
a) The energy required to create a new surface area. Units in this case are J/m^2
b) The energy absorbed per unit volume, units are j/m^3
What three things do you need to understand about a tough material?
1) Needs a large amount of energy to break it
2) Undergoes a large amount of plastic deformation before breaking.
3) Resists crack propagation
What are brittle materials?
1) break soon after elastic limit
2) cracks pass easily through the material and fracture tends to be sudden and catastrophic.
Brittle can be strong
What does hard mean and what it’s units?
Unit: pa
Resistive to dents or scratches
What does elastic mean?
- Can return to its original shape when stress removed ( without loss of energy )
What does elastic deformation mean?
Means temporary change of shape.
