Converting Engineering to True stressstrain curve Tutorial

hello friends welcome to abacus equipment for quick and sound learning so in this tutorial I will quickly show you how to convert the engineering strengthen goal to a true strain curve so as a CA engineer we always we do this exercise up ten times changing this is an extra strain go to a true strain curve so typically we receive the data from the lab from the uniaxial test data from the lab and this is provided or shared in the form of engineering stress-strain curve and when we do a fee analysis and we need to know we also want to incorporate the material on it into the FE model we need to feed this curve in the form of recession curve and the second step will be doing and in the last step so we need to change this true stress strain curve to effective plastic strain versus effective stress in stress curve so this is how it looks like and this will be the final input or the the curve data that is XY data will be feeding into the abacus input file or abacus CAE tool and there are standard formula available for converting the engineering stress-strain curve to a true stress strain curve and before that just I will give you the comparison of the how the plot looks like so when we see engineering stress-strain curve this is the black curve and it has a typical phenomena of ultimate stress and then followed by the nicking and the fracture at this point and when we change this black curve that engineering stress-strain curve to a true stress strain curve so we we generally see a steeper curve you know that is a blue curve which is a stiffer and it doesn't have a negative slope okay and why we are getting this because when we do know when we consider this uniaxial test so when we talk about engineering system code that is totally calculated based on the original area and then we when we calculate the true shaitaan' curve so we'll be considering the reduced cross section area at that instant or that that corresponding application of load value this is the nature of the curve what we get so coming back to the formulas so the two stress-strain curve when we calculate that is the first step is to calculate the true strain and the formula available is this is a very standard formula you might ever read in your basic engineering to strain is equal to natural log of 1 plus e so here is a engineering strain and then once we calculate their true strain we need to ship to the true stress values so true stress is equal to engineering stress multiplied by exponential of true strain so this true strain value will be using the one we calculated using this formula and once we do this completely for this to sustain curve we'll be calculating the effective plastic strain so effective plastic so when we feed into abacus or any API model we need to feed it as a effective plastic strain versus stress so to do that we'll be deducting the pain the elastic strain component from that particular total strain and so by doing that we will be having a complete pure plastic strain available data available to feed into abacus model so once we do this exercise so this is in a one fit curve we have this engineering strain curve and then a stiffer curve which is converted to a 216 curve so this is the formula like when we talk about the two strain that is natural log 1 plus e and then followed by the stress the true stress and you can see that when we convert this there will be a lag into the strain values so strain value will be reduced and this is the corresponding stress value will be go up when we talk about the true stress and curve which is a stiffer curve what it what you see generally so let I will quickly show you how to do it in an excel sheet excel sheet is excellent tool to do this exercise very fast and without any errors just for demonstration purposes I already have this data engineering stenosis engineering stress data and typically we have this yield stress values this is for I will say mild steel and and these are the external ending state data and let us convert it quickly and I will show you how to use this excel sheet okay so go to formulas and say insert function so we need to calculate the natural log as per the formula so select this natural log if this is not available you go to the maths and techno mitri option and then look for the natural log okay and the Select data engineering strain okay and then here you need to say here you need to say plus 1 that's it and simply drag this okay so we have the two strain is ready and then now we will move to two stress so as for formula now we will be looking at the exponential component that is exponential function okay an exponential of two strain yeah and then we will be multiplying with engineering stress value yep so basically that will be zero okay so this is your the simply drag it so you get there to stress values and now we need to detect the elastic strain component from this strain value so I will slightly I change now will be as I mentioned we need to ship this curve to directly on y-axis so by deducting the black elastic strain component to do that so I will make some changes over here so we have let it this 0 0 so we have to start with the yield stress value so that is this can copy this value over here suggest values yeah now we have to deduct the elastic strain component so this is minus again the same one so here I will be putting a dollar so that it will be a constant for all other values 0 then you simply drag it okay so here we go so now they'll affect the plastics in data is ready and you have to simply copy this corresponding values over here apply as values that's it so guys this data is ready and when we feed into a abacus input file it is in the form of stress versus plane that is all right so this is the form of data we need to feed so I will show you in correctly in efficacy so just for for a demo I have this material curve keyword ready so you have to just simply paste it over here so that's it so this data ready to use in your Fe model so just say okay so of course we need to define the modulus and the poisons ratio into this keyword and the same way if we want to edit the input deck so what I will do is I will simply insert another column okay that is a comma okay I will just drag this alright so this is the data ready and sick-sick come copy and the text pad okay just for under the star plastic keyword you have to copy so all other information already Fe this is just for your demonstration how we can do it effectively and say insert okay insert as block so whatever we have this value now let us look at the comparative curves of this engineering stress - - stress strain curve how it looks like in XY plot so for that I am taking this data so this is a engineering stress-strain curve and then I simply add this for the true okay so this is how it looks like and then you can add the effective plastic strain also effective stress as well alright so this is how it looks like this blue curve is the inner Nexus end core and this red and the green which o is all lapping in the two session go okay so describe before the engineering session curve when we can note to true session code it look eight it becomes most affirm and there is a no negative slope so that is again it is consistent over here so guys this is what I wanted to show in this tutorial if you find this video useful please do like us this YouTube video and also subscribe our channel abacus equipment to keep receiving exciting videos thank you bye bye