Definitions 4 Flashcards
What is Osteonecrosis?
A condition in which bone death occurs due to ischaemia
What is Paget’s disease?
A condition in which there is abnormal bone turnover and remodelling
What is Lubrication?
A physical process which reduces wear between two articulating surfaces
What is stress?
Force per unit area (N/m2)
What is Strain?
Change in length/ Original length - no units
What is Elastic?
Reversible deformation
What is plastic?
Irreversible deformation
What is Yield point?
Point at which there is a dramatic increase in strain with little increase in stress ( transition from elastic to plastic)
What is Yield strength?
Stress necessary to produce a specific amount of permanent deformation (0.2%)
What is UTS?
The maximum amount of stress before failure
What is Stiffness?
Resistance to deformation- a product of stress/strain ( Young’s modulus)
What is Stiff?
A material resistance to deformation
What is rigid?
A structure that is resistant to deformation
What is ductile?
A material that undergoes a large amount of deformation prior to failure
What is Brittle?
A linear stress/strain curve up to the point of failure
What is Shear stress?
Shearing load/unit area being sheared
What is Shear strain?
Angle thru which a material is disorted by shear stress
What is shear modulus?
shear stress/shear strain (N/g)
what is anisotropy ?
Material properties stress vector dependent
What is hardness?
Scratch resistance
What is work hardening?
A process by which plastic deformation increases the hardness and strength of the material
What is viscoelastic?
Time dependent stress/strain characteristics
What is Creep?
Time dependent deformation under constant load ( e.g. skeletal traction)
What is Stress relaxation?
A time dependent reduction in stress required to maintain the material at a constant strain (e.g. corrective splint)
