Defining Ramberg–Osgood material

Could someone clarify me how to define a Ramberg–Osgood material in Mecway or give me some useful link?
The thing is that in literature and online spreadsheets (e.g.; that i have found the R-O equation looks a bit differently.
In Mecway i have to define material exponents n and α. As i understand from the literature that for steel the product of α (σ/E) has to be 0.002, but since in Mecway i have to define only α not the product of α (σ/E), i don't know what to enter because the relationship of σ/E becomes a variable as well (so α should be changed too to get allways 0,002). And i am not shure wheather the exponent n is the same that a i get from previously menstioned resources becaus in Mecway we have exponent n-1 not n, or is it?


  • To be honest, I don't know much about it besides the formula used by CCX. Here is a simple example whose solution matches that formula.

    You do have to define E, but that's on the Mechanical tab of the material properties window.
    CCX S20 ramberg osgood.liml
  • Thank you Victor for the promt reply, but i think that i have figured it out, see the attached xlsx file.
    Exponent n stays the same and alpha is calculated only for yield stress as 0,002* Young's modulus/ Yield strength.
  • edited November 2017
    CCX use generalized formula of Ramberg-Osgood equation.
    Another formula is:

    e = s/E + (s/K)^n (s: sigma; e: epsilon)

    For generalized law you need 3 constants: alfa, s0 and the exponent n. (plus E)
    Obviously there is a relations:

    K=(E/alfa+s0^n-1)^1/n could be sempificated

    You need at least two constants for defining the law n, K (plus E) These constants are obtained experimentally (alfa and s0 could be condensed on K). I divided constant n, K from E because the exprerimental procedure to obtain n and K are different from the tensile test

    See your spreadsheet modified
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