as you know all indian that speak english are not good at pronunciation, in this case ı dont understand and ı dont watch those videos, but this profs pronunciation is enough for understanding lecture, thanks
Dear Sir, thank you for giving very nice lecture. I have few questions. If we have Engineering stress and strain, then why we use true stress and strain? What is the significance of true stress and strain? True stress and strain gives real picture of actual stress and strain, then why we use Engineering stress and strain?
Engineering stress and strain are easier to compute. True stress and strain are more accurate. However, for small strains (as in elastic regime for metals) the two values are practically equal. Thus for elasticity, it is better to use engineering values. The difference between true and engineering values become significant in case of large strains as in the case of plasticity. Thus for fundamental theories of plasticity true stress and strains are recommended.
Initial length can i the entire reduced section or to be precise a gauge length according to the material. or u can take random length also but within the reduced section.
Why want grip portion in test piece old method used long test bar take measure the length and fixed the test bar after broken length measure results found
@@Meetthelalu because strain is cause and stress is effect ,, stress is not applied force related it is related to restoring force so strain is cause and strees is effect
Sir, can we have same stiffness( Young's modulus) for different materials or Can we have two materials having same young's modulus with different yield stress starting from same initial loading conditions in stress strain curve
Yes, it is possible. Yield strenghth is structure sensitive whereas modulus is structure insensitive. So it is possible to alter yield strength, but not modulus, by a change in microstructure of the material. An example is strain hardening which will significantly change the yield strength but not the modulus.
sir these two words strength and hardness are always a big confusion to me . u also defined hardness as a measure of resistance to deformation and strength as ability to resist deformation .both seems same in terms of definition . could you elaborate from material science point of view
Strength is more general, it is usually resistance to plastic deformation of fracture. Hardness is a measure of resistance to plastic deformation under a specific test: the hardness test, in which an indenter causes plastic deformation on the surface of the material. Yield strength is also a measure of resistance to plastic deformation, but under a different test--uniaxial tensile test.
sir why does the stress drops a little after upper yield point and then starts increasing in case of mild steel whereas in other materials we don't see this kind of curve dropping just before increasing?
This is an important effect related to the presence of C atoms around dislocations, called the Cottrell atmosphere. These C atoms pin the dislocation making it difficult to move and raising the yield stress to upper yield stress. When the dislocation breaks away from the atmosphere it is easier for it to move, giving the lower yield stress.
The loading can be done at different rates of strain. Materials properties depend upon the strain rate. In a classical "static" tension test, discussed in this video, a very slow strain rate in the range of 10^-5 to 10^-1 s^-1 is applied.
@Divakar: Thanks for alerting me on the issue of correct spelling of this concept. I have now checked several sources and find that both spelling are used. G.E. Dieter in his book Mechanical Metallurgy uses 'gage'. Whereas, I just checked the British and Indian standards on tensile testing and they use 'gauge'.
Brilliant explanation in a very simple way, much appreciated!
Great explanation ...making things simpler.
as you know all indian that speak english are not good at pronunciation, in this case ı dont understand and ı dont watch those videos, but this profs pronunciation is enough for understanding lecture, thanks
Bro, every English speaking Indian pronounce words much clearly than native English speakers
@@Batman-my7wxyeah Banda zyaada angrez ban raha Hai ignore him brother 😢😢😂😂😂
What a teacher
Easy way to explaning
What an Explanation
Thanks so much
The next time I take this exam, I will get 100 plus. Thanks sir, you have greatly help me through my Aircraft Engineering course.
Great explanation!
wow..what a great explanation. i would be grateful to you
Very nice teaching sir 👍🏽 good explanation thankyou
Dear Sir, thank you for giving very nice lecture. I have few questions.
If we have Engineering stress and strain, then why we use true stress and strain?
What is the significance of true stress and strain?
True stress and strain gives real picture of actual stress and strain, then why we use Engineering stress and strain?
Engineering stress and strain are easier to compute. True stress and strain are more accurate. However, for small strains (as in elastic regime for metals) the two values are practically equal. Thus for elasticity, it is better to use engineering values. The difference between true and engineering values become significant in case of large strains as in the case of plasticity. Thus for fundamental theories of plasticity true stress and strains are recommended.
Good explanation sir thank s
Nice way to teach
sir, why brittle material is stronger than ductile material against compressive loads?
Superb sir ji
Wonderful lecture sir,
Sir.. initial length we use parallel length or total length?
Initial length can i the entire reduced section or to be precise a gauge length according to the material. or u can take random length also but within the reduced section.
Why want grip portion in test piece old method used long test bar take measure the length and fixed the test bar after broken length measure results found
Thanks Sir,
Sir,
In UTM we gradually increasing load.
( Calculating stress as load/ Area) Then how we get less stress value after yield point, and ultimate point.
Actually we are controlling the displacement, i.e., strain. So starin continuously increases and we measure whatever load or stress we get.
Why strain is always on X- axis.? Which one in independent parameter??
@@Meetthelalu because strain is cause and stress is effect ,, stress is not applied force related it is related to restoring force so strain is cause and strees is effect
Thanks a lot sir
Sir, can we have same stiffness( Young's modulus) for different materials or Can we have two materials having same young's modulus with different yield stress starting from same initial loading conditions in stress strain curve
Yes, it is possible. Yield strenghth is structure sensitive whereas modulus is structure insensitive. So it is possible to alter yield strength, but not modulus, by a change in microstructure of the material. An example is strain hardening which will significantly change the yield strength but not the modulus.
sir these two words strength and hardness are always a big confusion to me . u also defined hardness as a measure of resistance to deformation and strength as ability to resist deformation .both seems same in terms of definition . could you elaborate from material science point of view
Strength is more general, it is usually resistance to plastic deformation of fracture. Hardness is a measure of resistance to plastic deformation under a specific test: the hardness test, in which an indenter causes plastic deformation on the surface of the material. Yield strength is also a measure of resistance to plastic deformation, but under a different test--uniaxial tensile test.
sir why does the stress drops a little after upper yield point and then starts increasing in case of mild steel whereas in other materials we don't see this kind of curve dropping just before increasing?
This is an important effect related to the presence of C atoms around dislocations, called the Cottrell atmosphere. These C atoms pin the dislocation making it difficult to move and raising the yield stress to upper yield stress. When the dislocation breaks away from the atmosphere it is easier for it to move, giving the lower yield stress.
@@introductiontomaterialsscience thank you so much sir🙂
👍❤✌
Sir 5 independent slip systems are required for any given structure to be ductile?
Yes, that is right.
@@rajeshprasad101 why is it so sir?
👍😇
Sir ,what is the strain rate during the testing and on what factor strain rate depend?
The loading can be done at different rates of strain. Materials properties depend upon the strain rate. In a classical "static" tension test, discussed in this video, a very slow strain rate in the range of 10^-5 to 10^-1 s^-1 is applied.
Very helpful lecture sir. Respected sir did you have any paper for the same?? please shear the link or DOI number if possible
Thanks sir
Sir,
How to calculate yield point from S/N curve
Please Join with us
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Sir why yield stress generated
Yield means surrender. After yield strength the body stops resisting and starts plastic deformation until strain hardening starts.
Sir gauge length not gage length
Sorry its Gage length
It's IIT .
@Divakar: Thanks for alerting me on the issue of correct spelling of this concept. I have now checked several sources and find that both spelling are used. G.E. Dieter in his book Mechanical Metallurgy uses 'gage'. Whereas, I just checked the British and Indian standards on tensile testing and they use 'gauge'.