Hyperlife materials definition

MMarzin
MMarzin Altair Community Member
in Community Q&A

Hi everybody,

When you have some data for an SN curve (or EN curve), theses curves are define for a survival probability (50%, 90% or 95% …).

It seems that you can't define this probability in the material definition.

So i assume that to perform a calculation at P=95%, you have 2 solutions :

  • material data at P=95% and Std error at 0 and whatever the probability for the calculation (0.5- 0.95 - 0 …)
  • material data at P=50% and a std error from material data (or by default) and a probability for the calculation fix at 0.95

regards

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Answers

  • solon
    solon
    Altair Employee

    The S-N and E-N curves (and other fatigue properties) of a material is obtained from experiments. Due to the large amount of scatter that usually accompanies test results, statistical characterization of the data should also be provided. Certainty of survival is used to estimate the worst mean standard error log(N) according to the standard deviation of the curve. A higher reliability level requires a larger certainty of survival. Please have a look at the attached documentation link which describes these values extensively:

    https://help.altair.com/hwdesktop/hlife/topics/solvers/os/analysis_fatigue_other_factors_r.htm#:~:text=/%20Kf-,Scatter%20in%20Fatigue%20Material%20Data,-The%20S%2DN

    image.png

    The SE is the logarithmic error and it shows the real standard deviation of the curve data points. The standard deviation is the average amount of variability in your dataset. It tells you, on average, how far each value lies from the mean. So, this data is obtained and calculated from laboratory test results for the material that you want to simulate.

    -For SE=0 the perturbated value of life will remain the same regardless of the probability of survival: log(Ni^m)=log(Ni^sm)-z*SE⇒ log(Ni^m)=log(Ni^sm) [no change]

  • MMarzin
    MMarzin Altair Community Member

    Hi,

    Thanks for your answer.

    I really have no problem to manipulate material data with Normal law, fisher snedecor …

    maybe my question isn't precise enough.

    In Hyperlife 2023, i can't "associate" a probability of survival to my material data, but i can calculate at a probability of survival ( parameter "certainty of survival).

    If my material data is defined at P=50%, i have no problem to perform a calculation at another probability with hyperlife.

    But if my data is defined at P=75% and i need to perform a calculation at P=95%, i need :

    • material data at P=95% and hyperlife parameter at 0
    • material data at P=50% and hyperlife parameter at 0.95

    I think, at the moment, i have no other solution …

    regards

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