Stress Vs. Strain Diagram for Ductile Materials – Design of Machine

Stress Vs. Strain Diagram for Ductile Materials – Design of Machine


Hello Friends here in this video we will see the Stress Strain graph for ductile materials and for that purpose I have drawn the diagram here in this diagram we have on y-axis stress and on x-axis we have strain so this video will show us stress-strain graph for ductile materials now as I have drawn this graph here we can see some lines which I have drawn in red this is the origin o now when we look fro in this graph there are various points from O to A as we can see here we have an inclined line and this is we can say that a sense it is an inclined line it is not a curve so here we are getting a linear relationship between stress and strain and I can see that your o to a it is called as proportional limit now when we say that from o to a it is proportional limit it means if we go on increasing stress strain will also increase means their relation is directly proportional so in proportional limit I can say that therefore stress is directly proportional to strain so now as we can see in this stress all day I have denoted it by Sigma strain it is denoted by letter E if I remove this proportionality sign I have a constant here called as capital e I will say that where capital e it is called as Young’s modulus or modulus of elasticity its unit is Newton per mm square so as we have seen in this graph from zero to a it is proportional limit now when we reach point a that is if we are increasing the stress and we reach up to point a then we are getting a strain value as well here there will be stress and here we are getting strain now the moment we remove the load from point A it means stress becomes zero so if I remove the load this object will return back to its original shape it means it behaves in an elastic manner so within this zero to a region the material behaves in an elastic manner that is when the load is removed it will regain its original shape next we see point A to B that is I will write it down here on the next page from A to B it is called as elastic limit now when I talk about the elastic limit from A to B again as we can see here that I have when we have reached point B from A to B it is a curve now from zero to a the relation between stress and strain was linear from A to B the relation is it is a curve so the relation is not linear like it was from zero to a but even at point B if we are removing the load the material will regain its original shape so from A to B it is elastic limit now when we go from point B to C the change in stress is not very much as we can see there is very little difference between B to C so I can say that b2c it is called as here I’ll say that point C is called upper yield point is called as upper yield point it means at Point C the yielding has started yielding means change in shape so once the material crosses point B it reaches in the region between B to C where it will be permanently deformed that is if we remove the load from Point C then the material won’t regain its original shape it means at Point C it has deformed permanently so this B to C region it is also called as permanent set now when we are from region C to D as we can see in this diagram now compared to Point C Point D is below it means the stress at Point D it is less compared to Point C but the material is deforming wood as we can see at Point C the strain is less strain means the physical deformation and at Point D the strain is more but stress value is less so here I can say that C to D Point D is called lower yell point and strain is more at point d then point c next as we can see in this diagram D to e here again stress is increasing in a tremendously high manner as we can see here we can look at the diagram the stress at Point E it is the highest point in this graph so here we are getting maximum stress so I will say that point from the region D to e here point E is called yield point and stress is maximum at the yield point now up to point a the stress is maximum then if we go from E to F the stress will go on reducing as we can see the graph is falling so your stress decreases and from E to F we can say that stress decreases but strain increases as it is very much clear from the diagram from e2f the stress is falling whereas the strain is increasing here we can look at this and finally at point F er I’ve mark star the material will be breaking and this is called as breaking point so I will say that at point F the material breaks hence it is called as breaking point so now it is very much clear from this stress-strain diagram that this is for ductile material and ductile material will be flowing like this that is it shows the strain variation and strain is nothing but physical deformation which we can see and we can see the material flowing and finally it will break and this breaking point is just after the material has reached maximum stress so we can say that if the material is having maximum stress after that it can break at any given point so in this video we have seen stress strain graph for ductile materials

100 Replies to “Stress Vs. Strain Diagram for Ductile Materials – Design of Machine”

  1. Sir what is the difference between elastic limit and proportional limit? As we remove the load it can regain it's original shape upto point A also the same result for point B. But in graph one is straight line and another is curve… What is the reason behind it??

  2. Sir why stress is decreasing and strain is increasing at breaking point and at lower yield point because the stress is increasing

  3. Sir Please upload a video on explaining different regions in stress strain curve like stress hardening region, necking region and all.
    Thank you, BEST TEACHER ON YOUTUBE

  4. Sorry sir .
    But instead of drawing graph n then explaining ,please explain how the graph took that shape.
    It's a request

  5. Dear sir,
    .
    When we applied the tensile load on the ductile material then why the failure is due to shear..? Plz explain.

    Hoping your response very soon..🙏

  6. sir,i want to learn how to draw strain vs time graph from stress vs time graph of elasto-visco- plastic material!
    can u help me sir,??

  7. Sir, I have a doubt.. Hooks law is valid upto elastic limit, but here stress is prop to strain upto limit of proportional… According to hooks law what's the correct point sir,..

  8. Point E is very important as it is ultimate strength but you have mentioned it wrong. From a to b is elasto-plastic region, not elastic. After point a, elastic property is lost. Some important points have not been explained

  9. I want to know one thing: Since we are stressing the material initially there is no deformation. As we apply more load, the material starts to show resistance. So stain is depending upon the load. Why is not strain taken on the y axis ? Is strain causing stress or stress is causing strain ?

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  11. He is ok but he failed to give more explanation about the graph.

    Why mild steel is most commonly used material in civil construction?

    Why stress is plotted against Y- axis and strain is plotted against x-axis?

    What is the angle made by the curve at the initial stage?

    What is the percentage of the elongation at the each stage?

    What is the gauge length and it's value?
    What is gauge dia and it's value?

    He havenot explained why the stress is falls from c to d and why the stress again raised from D to E?

    He failed to explain about the carbon role here.

    so many things are there he just simply explaining about what written in the book?

    He failed to explain at what stage material starts yielding ? At 0.2% material starts yielding in fe250 steel that can be seen visually through naked eyes(which means yield point can be defined)whereas in fe415 and fe500 yield point is not defined.

  12. Why are you teaching wrong,don't make it further.If you have such hobby then you have to study more about this then you come.

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