Elasticity Flashcards
Are there rigid bodies in nature?
No
All bodies subjected to external forces undergo deformations
When is a body defined elastic?
When it resumes its original shape after the force that deforms it ceases
What is plastic?
Deformation that remains after the cause has been removed
What is subcritical damping? (Damped harmonic motion)
When the friction is small so the body makes various oscillation of decreasing amplitude before stopping
What is supercritical damping or over damped motion? (Damped harmonic motion)
When the friction is large so the body reached equilibrium position without any oscillation (like shock absorbers)
What 3 types of effort can cause deformation?
Traction
Compression
Cutting
What is stress a measure of?
The force applied per unit cross-sectional area causing a deformation
Differences between stress and pressure
Pressure is always normal to the area where stress can be normal or tangential
Pressure is always compressive in nature where stress may be compressive or tensile in nature
What happens when the elastic limit of a body is reached?
Further deformations become irreversible and plastic until it braks/fractures
What does the potion ration express?
How much a body stretched under the action off a force deforms in other directions
What type of elastic fibers contribute to the elasticity of blood vessels?
Elastin and collagen
What does the elasticity of the blood vessels allow for the blood flow to be?
Pulsatile, not intermittent
What causes torsional fractures?
Compressive, bending and torsional loads
What characterises torsional fracture ?
Spiral cracks around the axis of the bone
What is the optimal ratio between external and internal diameter?
11:8
