What is Upper & Lower Yield Point| Yield Point Phenomena| Cottrell Atmosphere| Low Carbon Steel Test

In low carbon steel:
Impurities create strain field in the nearly iron atoms of dislocation. Hence when the external load is applied to do the plastic deformation, larger stresses are required by dislocation to overcome strain field by Cottrell Atmosphere and move to new edge dislocation. That is why upper yield phenomena occurs.
Once dislocation crosses this Cottrell Atmosphere, now less stress is required to continue dislocation motion.. Hence lower yield phenomena occurs.
Appearance of Upper yield point and lower yield point is called yield point phenomena.
In medium or high strength steel, % of carbon is high. So, carbon is not only present on dislocation site, but also on regular interstitial sites. So the moment when dislocation breaks Cottrell Atmosphere and jumps to other site, Cottrell Atmosphere forms instantly at new site due to presence of larger % of carbon.
Hence no chance of L.Y.P. is there. So no YPP appears in medium and high carbon steel.

[@toxiclodu446]

Thank you Sir for the explanation

[@SanjuDevi-uj1pg]

Reinforced steel or steel rebar is better than steel in a lot of ways. Given the additional elements in it, there is a lot it can do and withstand, which is better compared to steel. For instance, it is non-corrosive. Steel rebar, unlike steel, can last up to a hundred years without losing its molecular integrity.
Thank you sir

[@knowcivilengineeringwithkundan]

Well said!

[@Supriyaaa_Vlogs_kannada]

very nicely explained thank you

[@knowcivilengineeringwithkundan]

My pleasure

[@er.rahultiwari9357]

Good , keep it up

[@knowcivilengineeringwithkundan]

Thank you, I will