Defining Ramberg–Osgood material

Hi!
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. https://mechanicalc.com/reference/mechanical-properties-of-materials; engineerstoolkit.com/etk_material_curves_20121018.xls) 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?

Comments

  • 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.
    liml
    liml
    CCX S20 ramberg osgood.liml
    3K
  • 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.
    xlsx
    xlsx
    Ramberg-Osgood.xlsx
    63K
  • edited November 7
    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
    Regards
    xlsx
    xlsx
    RO-equations.xlsx
    61K
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