Yield & Tensile phenomenon in mild steel
Vadivel Mahadevan
sudhakar kuppuswamy
Hi Vadivel,
It is termed as Yield-point phenomenon,
Occurs due to the presence of interstitial or substituonal impurities in the metals.
During tensile load , the load increases steadily with elastic strain , drops suddenly, fluctuates about some approximately constant value of load , then rises with further strain....the load at which a sudden drop occurs is called the upper yield point and at constant load is called the lower yield point.
Presence of impurities, obstacles the free flow of metal during tensile loading , hence two yielding occurs.
The presence of carbon and nitrogen in steel motivates this phenomena.
Regards
Sudhakar.K
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george....@gr.bureauveritas.com
What you are calling impurities in metallurgy is called "dislocations"
Best regards
Dr Georgios Dilintas
Authorized Nuclear Inspector
Authorized Inspector Supervisor
HBS Regional Technical Manager
Manivannan Hemu
Low carbon steel exhibit a localized heterogeneous type of transition from elastic to plastic deformation which produces a yield point in the stress strain curve.
At the upper yield point a discrete band of deformation occurs due to the stress concentration such as of fillets and the coincident with the formation of the bands the load drops to the lower yield point.
The band then propagates along the length of the specimen causing yield point elongation.
In the actual testing several band formed at several points of stress concentration. This slip bands are called Lϋders band.
As the formation of several bands the yield point elongation is irregular.
Each shock is corresponds to the formation of new band propagated to cover the entire length of the specimen test area, the flow will increase with stress-strain in usual manner. This is indicated in the end of yield point elongation.
as stated in the previous response this phenomenon is caused by the elements as C and N.
regards,
MANIVANNAN.P
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