IMPACT TEST

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IMPACT TEST

• EXPERIMENT 7
• Instructor M.Yaqub

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IMPACT LOAD

• Shock load or sudden load is referred as impact
  load.
• In order to select a material to withstand sudden
  intense below, we must measure a materials
  resistance to failure in an impact test.
• The ability to withstand an impact below is
  referred as toughness of the material.

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IMPACT TEST

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IMPACT TEST CURVE
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RESULT OF IMPACT TEST

• From the curve, it is clear at high temperature,
  a higher amount of energy is required for the
  fracture.
• Here fracture is ductile, means a lot of
  deformation before the fracture.
• At low temperature, a small amount of energy is
  required for the fracture.
• Here fracture is brittle, means a very small
  (practically no) deformation before the fracture.
  

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DUCTILE TO BRITTLE TRANSITION TEMPERAURE

• The fracture mechanism changes from ductile to
  brittle over a narrow range of temperature.
• This temperature is called DUCTILE TO BRITTLE
  TRANSITION TEMPERATURE (DBTT).
• DBTT can be read from the impact test curve as
  the median temperature of the curve.

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MORE ABOUT DBTT

• DBTT should be below the working environment
  temperature for a metal subjected to impact
  loading condition.
• Not all materials have a distinct DBTT.
• Usually BBC metals have DBTT while FCC metals
  dont.

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