Charpy Impact Testing: Why @ -20°? What @ Higher Temp?

[manmeet123]

Please can anybody explain why Impact testing is carries out @ -20 degree or @ lower temparatures. & what will happen if it is conducted @ higher temp.
Please elaborate.

 

[russ_watters]

Well - can you think of how the properties of materials might change with temperature?

 

[manmeet123]

Well - can you think of how the properties of materials might change with temperature?

Offcourse, Sir , below recrystallization temp ductility is less & above recrystallisation ductility & toughness values are more. Also movements of atoms are is faster @ higher temp & that will be lower @ Lower temp.
But if you can explain it in more specific technical way I will able to understand more effectively.

Waiting for ur reply.

thanking YoU!