Materials

Materials

1. Density

   • =mass/volume
   • Units= Kgm-3
   • Regular solids, liquids and iffegular solids
   • Density of Alloys
     • pAvA+pBvB/vtotal= density of an alloy

2. Hooke's Law

   • F=KX
   • springs in parallel vs springs in series
     • Parallel springs add the spring constants and the change in length is the same
     • Springs in series-
       • Force is the same in both and is equal to the weight W
       • 1/k= 1/kp + 1/KQ

3. stress and strain

   • elastic strain energy
   • Breaking stress= ultimate tensile stress-the highest stress expereinced by a material before breaking
   • E= 1/2 fX ***
     • = 1/2KX2
   • plastic behaviour- perm extension once the limit of proportionality is exceeded and the material no longer follows hooke's law
   • Fracture-
   • Brittleness-breaks without any plastic deformation
   • Stress-strain curves
   • yield point- where the wire temporarily weakens
   • stiffness- how difficult it is to change the shape of a material
   • Strength=ultimate tensile strength
   • toughness- energy needed to break a material

4. Young Modulus

   • Tensile stress/tensile strain
     • FL/AX
   • measure using searle's apperatus

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