Impact Test of Carbon Steel Material as Per ASME Sec.VIII

For one thing, to make sure that it doesn't get too brittle when cold, and thereby explode/implode from impact or shock loadings.

Dear Vijay,

First of all, the purpose of impact test is to find the hardness of the material used.

Now, why is it required to know the hardness of the material?

The Hardness of a material is directly porportional to the brittleness of the material, and brittleness is opposite of ductility, which is the property of a material to strain before final failure occurs, if a material has a hardness above a particular limit it will become brittle and will fail immediately at the aplication of a shock or variable loading without giving any warning before failure.

Materials have a tendency to become brittle at low temperatures and hence the materials having Operating temperatures lesser than MDMT are required to undergo impact test.

Also, Hardness is a major factor in the initiation of hydrogen induced cracking amd embrittlement. Hence it is always desirable to keep the hardness under a prescribed limit as suggested by codes and standards.

For the Impact test requirements for combimation of Thickness and temnperatures refer UCS 66

Thanks for reply.

Can you tell me one thing, Is it practicaly possible that "the materials having Operating temperatures lesser than MDMT" ?

Yes. It is possible that the design fails to take into account various process upsets that might produce a colder temperature than expected. For instance, one might design a refrigeration system for -40° normally. But if a compressor suction pressure cutout fails, the temperature might fall to -50°.

Most of this is correct, but not quite all. Impact (or Charpy or notch) testing measures toughness, rather than hardness. Hardness is important to know for abrasion resistance, cutting ability, etc. But it is not the same as toughness, or percentage of elongation at break. These are more aptly related to stretchiness or ductility of the material, rather than to hardness.

dear sir,

please tell me the procedure of impact testing as per ASME SEC VIII