Materials science, hardness of the material? in the lab we ran samples of brass and reduced to 10% -50% of original size. Now with this "work" of the material, it makes the material stronger (my teacher said of his work as a hanger-on metal becomes stronger).
Does it also make the material harder when the metal is stressed / strained?
I find it difficult to correlate all these words, as hardness, tensile strength, ductility. any help? Thank you!
The work area is usually either hot or "cold" intervals, being hot above the recrystallization temperature, and cold is below.
With the cold rolling, you get much more deformation of the crystal, you get tighter tolerances final, better surface finish and the metal hardens work normally "in the process.
With the hot rolling, you get more, finer, equiaxed grains, and eliminates internal tensions.
If you look at the definitions of those terms you listed, they should make sense a little more - but I will give my best shot:
Hardness tests - resistance of a material to permanent deformation (tested with Vickers Brinell and Rockwell
Tensile strength - strength of a material to a force of tearing (tensile test includes a control rod in a triangle and a machine will literally with the same force in opposite directions until the tears the sample into two). The criterion that is used to make curves of stress versus strain (very important!)
Ductility - ability of a material to deform in tension. Thus, a brittle material is the opposite of ductile. Usually ductile materials can deform much before they fail (like stretching a piece of chewing gum, then break into two), where, as a brittle material can take a lot more strength, but will break down much faster. Just think of a rubber band that stretches like a madman before breaking (ductile) and a cup of coffee has dropped from a height (fragile).
I hope this helped a bit, if you have further questions, please post them or send me a private message, I am more than happy to help!
:-)
Yes, it is a harder material when it is stretched, but the tension zone also becomes more fragile and more susceptible to cracking and brittle fracture.
In general, hard materials have a higher resistance to traction and ductile materials are softer and have less resistance to traction.
But the strain hardening ductile material and crack easily when subjected to cyclic loads reversed.
Posted on May 24, 2010.
