1. Father of Indian
dentistry -----R AHMED
PHYSICAL
PROPERTIES
2. Stress ----the internal
force resisting the appiied external load in a unit area is called stress.
3. Dependin upon direction
and magnitude stress may be:
Compressive----it
is the internal resistance to load placed on a body, which tends to compress/
shorten it.
Tensile--- any
resistance to deformation of a body by load that tends to stretch/elongate it.
Shear---
stress that tends to resist twisting motion or a sliding of one portion of a
body over another.
Impact----
it is the stress that is induced by one/both bodies in motion when they meet.
4. Strain---- it is the
deformation either / inelastic that results from appication of load ----it is
measured in terms of deformation of structure per unit dimension.
5. Strain may be
elastic/plasitic-----elastic strain is reversible and disappears after stress
is removed -----plastic strain is the permaneent deformation.
6. Elastic limit----it is
greatest stress to which material can be subjected such that it will return to
its original dimension when forces are released.
7. Proportional limit----it
is the maximum stress that may be produced in a structure with the stress
remainning proportional to the strain (Hooke’s law)
8. Hooke’s law-----stress is
directly proportional to strain in elastic deformation.
9. Yield strength-----it is
strength required to produce particular offset (plastic strain) chosen.
10. Modulus of
elasticity-----(Young’ smodulus ) it is the property found by dividing stress
by corresponding strain at given load below the porportional limit .It is equal
to rigidity or stiffness of material.
11. Flexibility-----it is
defined as the strain that occurs when the material is stressed to its
proportional limit.
12. Resilience ------amount
of energy absorbed by a structure when it is stressed not to exceed its
proportional limit.
13. Modulus of
resilience-----amount of energy stored in the body, when one unit volume of
material is stressed to its proportional unit.
14. Strength----maximal
stress required to fracture a structure----depending upon predominant type of
stress it is called as compressive strength, tensile strenghth, swearing
strength.
15. Diametral compression
test-----is used to measure tensile strength for only materials that exhibit
very limited plastic deformation.
16. Toughness-----energy
required to fracture a material.
17. Ductility-----ability of
a material to withstand permanent deformation under a tensile load without
rupture.
18. Malleability
-----ability of a material to withstand permanent deformation without rupture
under compression.
19. Ductility decreases with
increase in temperature, malleability increase in temperature.
20. Gold is the most ductile
and malleable metal-----followed by silver, platinum and copper.
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