Mechanics of Biological Materials Flashcards
Define Mechanical Stress
internal force divided by the cross sectional area of the surface on which the internal force acts
What are the 3 types of mechanics stress?
- Tension
- Compression
- Shear
Define tension?
A pulling force (equal and opposite), tries to separate an object
Define Compression?
Squeezing force, pushes objects together, deformation by shortening in the direction of the external load and widening
Define Shear?
acts perpendicular (90 degrees) to the long axis of an object. Causes objects to slide past one another or create angular displacement
Explain Bending load?
Produces tension and compression stresses, one side is compressed, the other side is under tensile stress
- external contact, gravity, and muscle tension can create a bending load
Explain Torsion load?
A torque that creates a twisting load about the long axis of a structure
Explain combined loads?
load created by a combination of tension, compression and shear stress
Elastic Behaviour
load creates deformation, structure regains its size and shape when the force is removed
Yield Point
point at which the structure moves from being elastic to plastic
Plastic Behaviour
as load increases the structure will deform and will not regain it’s original size and shape
Failure point
breakage or rupture of the material
Injury may occur due to:
- a high rate of loading - bone cannot deform fast enough (acute fracture)
- A high frequency of loading - small loads with repetitive loading (ie.stress fractures)
Acute Injury
larger force applied quickly - exceeds strength of tissue
Chronic Loading
small forces applied repeatedly over a longer time frame - produces a cumulative effect - inadequate recovery - the tissue may weaken and is more prone to injury
