Synopsis In Dentistry : Dental Materials

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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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