Titanic mainly failed because of low temperature. A ductile material will start behaving as a brittle material if we keep at the low temperature. The steel which was used in titanic wasn't tested for this which led to the distruction. Proper heat treatment and using better alloying material would have saved the ship !
As grains become finer, more grain boundaries will be there, more grain boundaries means more hinderance for the dislocations to move and that means less plastic deformations. So how fine grains will contribute toward ductility?
Not an easy question to answer. Perhaps the crack size present is also determined by grain size, the smaller the grain, the smaller the crack size. This will increase the brittle fracture stress and thus making it higher than the yield stress.
I think in the idea of avoiding DBTT we will seek after a fine grain size because it reduces the crack propagation at low temperatures, so we can say it enhances the (ductile behaviour), otherwise fine grains remain harder and stronger than larger grains.
Dear Anand Thanks for pointing this out. I have made a serious goof up here. You are absolutely right, yield stress curve should be below the fracture stress curve.
@@introductiontomaterialsscience Hi sir. I have the following doubts. 1. If BCC can exhibit DBT then why not FCC. 3. How an additive makes austenite stainless steel to be in equilibrium state at lower temperature. 4. By what mechanism finer grain size lowers DBT temperature 5. On what basis higer strain rate and notches increases DBT temperature.
@@harikrishnan3112 if you see pile up mechanism of fracture in dieter you can understand these they have derived a mathematical notation to these you can understand grain size effect
Sir, we studied in this lecture that ductile material generally transforms to brittle at low temperature. Is the inverse is also true, i.e. do brittle material also transform into ductile if the temperature is increased ?
In polymers the transition to brittle behaviour is related to glass transition. Glassy state of polymers are brittle. Below a certain temperature, called the glass-transition temperature polymers become glassy.
Sir you said that the brittle behaviour happens below the DBT temperature.. But in the high strain rate point in the characteristic of DBT you wrote high strain rate--high DBT temp--enhances brittleness.. How? These two statements are controversial.. Can you please explain it??
Thank you Sir... So this the reason for the sinking of Titanic as the strain rate was too high and the transition temp. Of the steel used must have been low, due to which the steel became brittle on impact of the iceberg as the temp of the ocean water in contact with the ship was below the transition temp of the steel used in the ship. Now i got the answer of this question which u didn't mention in the other video. Isn't it so? please let me know.
Fine grain size increases hardness and if hardness increases then brittleness increases...so sir pls reply how will it lower the transition temp?? Pls reply sir....
With decreasing grain size strength increases but transition temperature decreases. Increase in strength can be explained in terms of grain boundaries acting as an obstacle to dislocation motion. Decrease of transition temperature is an experimental observation but there is no easy explanation, as far as I know.
holey this guy took the effort to draw everything for us. really appreciate his kind work
Titanic mainly failed because of low temperature. A ductile material will start behaving as a brittle material if we keep at the low temperature. The steel which was used in titanic wasn't tested for this which led to the distruction. Proper heat treatment and using better alloying material would have saved the ship !
Very good explanation
Very Good explanation.thank you sir
How is it that you know every answer to my questions. Thank you sense
Thank you 💪🏾✌🏾
Sir, can I apply this method to bolt forging (cold forging) analysis? specially for dies and punch for bolt production
How do you calculate ultimate tensile strength from yield strength?
thank you sir , super
Sir, what is mechanism by which at low temperature brittle transition happens? Anything related to bond strength? or something else
Dear sir, why is it that FCC metals don't show DBTT but BCC show them?
Thank you
Below -101degC, even 304SS are impact tested to ensure that material has enough ductility to be used for fabrication.
Thanks a lot. Could you please share more details.
Hocam yazıyorsunuz bu işi. I mean you are doing it. Love from Turkey.
kesinlikle abi. yapıyor ya.
ve sadece hintlilere cevap vermesi biraz komik :D
@@ibrahimyldrm2427
İNGİLİZCE sorunuzu sorun definitely kesinlikle cevap verecektir ...😂😂
why there is sharp DBT temperature for very low carbon steels in comparison to high carbon steels?
As grains become finer, more grain boundaries will be there, more grain boundaries means more hinderance for the dislocations to move and that means less plastic deformations. So how fine grains will contribute toward ductility?
Not an easy question to answer. Perhaps the crack size present is also determined by grain size, the smaller the grain, the smaller the crack size. This will increase the brittle fracture stress and thus making it higher than the yield stress.
I think in the idea of avoiding DBTT we will seek after a fine grain size because it reduces the crack propagation at low temperatures, so we can say it enhances the (ductile behaviour), otherwise fine grains remain harder and stronger than larger grains.
Best video
sir i think for FCC materials, yield stress curve should be below fracture stress
Dear Anand
Thanks for pointing this out. I have made a serious goof up here. You are absolutely right, yield stress curve should be below the fracture stress curve.
i may be wrong, but that should be replaced with HCP materials
@@introductiontomaterialsscience
Hi sir.
I have the following doubts.
1. If BCC can exhibit DBT then why not FCC.
3. How an additive makes austenite stainless steel to be in equilibrium state at lower temperature.
4. By what mechanism finer grain size lowers DBT temperature
5. On what basis higer strain rate and notches increases DBT temperature.
@@harikrishnan3112 if you see pile up mechanism of fracture in dieter you can understand these they have derived a mathematical notation to these you can understand grain size effect
@@harikrishnan3112 and also notches effect
Sir, we studied in this lecture that ductile material generally transforms to brittle at low temperature. Is the inverse is also true, i.e. do brittle material also transform into ductile if the temperature is increased ?
Yes, it is a reversible transformation. It happens both ways.
Why the FCC crystals are not much sensitive to temperature ? Where as BCC crystals will ?
Interesting question. Don't know the answer yet :-(
Dear Sir, can you explain the same behavior for the polymers.
In polymers the transition to brittle behaviour is related to glass transition. Glassy state of polymers are brittle. Below a certain temperature, called the glass-transition temperature polymers become glassy.
Sir How DBTT reduces with respect to reduction in grain size?
AA very difficult question. Myself looking for an answer.
Sir you said that the brittle behaviour happens below the DBT temperature..
But in the high strain rate point in the characteristic of DBT you wrote high strain rate--high DBT temp--enhances brittleness.. How?
These two statements are controversial..
Can you please explain it??
Let at low strain rate the DBTT be TL and at high strain rate TH.
For TL
@@introductiontomaterialsscience thank you sir
Thank you Sir...
So this the reason for the sinking of Titanic as the strain rate was too high and the transition temp. Of the steel used must have been low, due to which the steel became brittle on impact of the iceberg as the temp of the ocean water in contact with the ship was below the transition temp of the steel used in the ship. Now i got the answer of this question which u didn't mention in the other video. Isn't it so? please let me know.
Sir, why do you always reply indian students? hahaha
Fine grain size increases hardness and if hardness increases then brittleness increases...so sir pls reply how will it lower the transition temp??
Pls reply sir....
With decreasing grain size strength increases but transition temperature decreases. Increase in strength can be explained in terms of grain boundaries acting as an obstacle to dislocation motion. Decrease of transition temperature is an experimental observation but there is no easy explanation, as far as I know.
👍👍👍👍
Sir,
How is Austenite phase stable at such low temperatures in austenetic stainless steel?
Due to addition of stabilizers
Due to Nickle content its decerease the DBTT Temp