I have tensile test result of a material at different temperatures - elongation vs stress. From these results, how can I calculate effective plastic strain for flow curves?
The key in calculating the effective plastic strain is finding the yield stress and the matching strain. Based on your question I am assuming that a graudual rise of non-linear behaviour is occuring. Let's go to all steps:
Thank you for your link. I have calculated the true stress and strain and used the 0.2 % offset method to find the yield point. But when I update the flow curves at different temperatures, simufact asks me to set a common axis for all curves. How can I make a common axis for all curves? For instance, flow stress at zero plastic strain is not possible, at 25 deg C - 1000 Mpa flow stress results in the onset of the plastic strain of 0.04, and at 100 deg C - 800 Mpa flow stress results in the onset of 0.03 plastic strain. The onset of plastic strain is different for different temperatures. Please let me know how to update the model.
The yield point with zero plastic strain and the different yield stresses for different temperatures should be the starting point of the flow curves.
As an example based on the given values: flow curve 25 deg C: 950 MPa, 0.0 plastic strain, 1000 MPa, 0.04 plastic strain. flow curve 100 deg C: 700 MPa, 0.0 plastic strain, 800 MPa, 0.03 plastic strain. The yield point values are pure guesses on my part, but should demonstrate the idea.
I understand the stress input is called flow stress in the GUI, but the yield point has to be considered as the starting point of the flow curve.
How can I define a common maximum plastic strain for all temperatures? Like , at 25 deg C , the max. plastic strain before failure was 0.12, at 500 deg C, the max. plastic strain before failure was 0. 20, it changes based on temperature. In my simulation, I took 0.12 as the maximum strain for all curves, will it affect the result?
I cannot evaluate, how the results are affected, because I don't know missing parts of the flow curve and the model. However let's describe, what is used as material data in yoour model. If plastic strain > 0.12 occurs in the model, the flow stress at 0.12 plastic strain is used for the calculation.
Thats why I would recommend to use the maximum plastic strain at all temperatures as end point of all flow curves, in your example 0.2 plastic strain at 500° C to be able to include the complete flow curve and fill flow curve interval between 0.12 and 0.2 for 25°C with a constant plastic strain matching the value at 0.12. During postprocessing you should then check, when and at which temperature plastic strain values >0.12 are reached. If you have any follow up questions you can also reach out to me and my colleges at support@simufact.de .
