1. IMPACT TEST EXPERIMENT # 7 Instructor: M.Yaqub

2. 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 material’s resistance to failure in an impact test.  The ability to withstand an impact below is referred as toughness of the material.

3. IMPACT TEST 

4. IMPACT TEST CURVE

5. 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.

6. 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.

7. 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 don’t.