Unit weight of Engineering Materials

Unit weight means weight of material per unit volume(1 m3   or 1m x 1m x 1m ).

Unit weight of cement : 14.40 KN/m3

Unit weight of Sand  :17 KN/m3

Unit weight of Aggregate  :15 KN/m3

Unit weight of Brick Masonry  :19.20 KN/m3

Unit weight of Brick Stone  :20.80 to 27 KN/m3

Unit weight of Steel  :78.50 KN/m3

Unit weight of Wood  :12 KN/m3

Unit weight of Plain Cement Concrete  : 24 KN/m3

Unit weight of R.C.C  : 25 KN/m3

Unit weight of Water  : 10 KN/m3

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Types of Helical Spring

A spring is a device whose function is to deflect under tensile or compressive load and recover its original shape when unloaded.

Types of Springs:

  • Helical Spring
  • Spiral Spring
  • Leaf Spring

Helical Springs: In this a wire coiled in the form of helix.

  • Closed Coil Helical Spring(Tension Spring)
  • Open Coiled Helical Spring(Compression Spring)
  • Torsional Spring
Closed Coil Helical Spring Open Coiled Helical Spring
1.       Resist tensile forces. Resist Compressive forces
2.       Pitch is very small. Pitch is high
3.       Each turn lie in same plane at right angles to the axis of helix. No turn lie in the same plane , hence each turn lie inclined to the axis of helix.

The maximum shear stress occurs at the innermost fibres of a helical spring under torsion is because of curvature effect.

Where, D= mean diameter of helical coil

d= diameter of spring wire.

Types of Defects in Brick

Brick defects are as follows:- 

  • bloating : presence of swollen mass at surface due to excess in carbonaceous and sulphur content.
  • lamination: presence of lamina due to air entrapment in clay, when molded clay and sand mixed with another mold then two layers were formed with entrapped air.
  • Chuffs : A deformed shape was obtained by falling of rainwater on hot brick.
  • Black core : due to improper burning i.e. lack of oxygen for carbon and sulphur oxidation within clay.
  • porosity : presence of voids i.e small empty pockets.
  • nodules: a small swelling at the surface of brick.

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