30. Mechanical Properties of Solids and Tissuesrename
yaboiemil's version from 2016-01-26 12:11
Section1. Substances can be divided into 5 groups by their reaction to stress (F/A). These are:
|Elastic Substances||Substances that resist a deformative force, returning to original shape. Obey Hooke's Law.|
|Plastic Substances||Substances that deform non-reversibly under stress. (e.g. Piece of metal hammered)|
|Viscous Substances||Newtonian and Non-newtonian.|
|Newtonian Substances||Rate of deformation directly proportional to shear stress.|
|Non-Newtonian Substances||Rate of deformation not directly proportional to shear stress. Dynamic Viscosity will determine deformation.|
|Viscoelastic Substance||After stress is released, relaxation occurs and shape returns. Needs force tho. Hysteresis.|
|Plastic-Viscoelastic Substance||Viscoelastic up to critical value, then deforms like a plastic.|
2. In Viscoelastic substances, deformation is stress AND time.
3. Hysteresis is lag in response to a change in force, due to history of other forces on object.
Hooke's Law of Elasticity:
|Weird curly E||Deformation|
|E||Modus of Elasticity (numerically = tensile strain)|