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S-N diagrams

  1. Aug 10, 2011 #1
    how do i plot the follwing S-N diagram, i am having trouble with what im supposed to do with the 'cycles to failure' figures:
    stress amplitude ........ cycles to failure
    (y axis)- ................. (x axis)
    170 ...................... 3.7 x 10^4
    148 ...................... 1 x 10^5
    130 ...................... 3 x 10^5
    114 ...................... 1 x 10^6
    92 ..................... 1 x 10^7
    80 ....................... 1 x 10^8
    74 ...................... 1 x 10^9


    im confused about what to do with the 3.7 and 3?
     
  2. jcsd
  3. Aug 10, 2011 #2

    SteamKing

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    Do you understand scientific notation?

    Due to the nature of the data, it is recommended that a log-log plot be used for S-N curves.
     
  4. Aug 11, 2011 #3
    ok.....so how would i go about doing that?
     
  5. Aug 11, 2011 #4
    why would you recommend a log-log plot? can i not just plot it as stress against logarithmic scale of the cycles to failure?
     
  6. Aug 11, 2011 #5

    SteamKing

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    You can. But often if a log-log plot is used, the S-N curve plots as a straight line, which is really handy.
     
  7. Aug 14, 2011 #6
    well.....i've decided to plot stress against the logarithm of the N-values? could you please show me how im supposed to deal with the figures 3 and 3.7?
     
  8. Aug 14, 2011 #7

    SteamKing

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    For example, in the table in the OP, a stress amplitude of 170 correlates with 3.7 x 10^4 cycles to failure. 3.7 x 10^4 is scientific notation, and this figure equals 3.7 x 10000 = 37000 cycles. In your plot, assuming you do a log-log plot, the x value of this point is log (37000) = 4.568, and the y value is log (170) = 2.230

    I strongly urge you to study and refresh your knowledge of scientific notation.
     
  9. Aug 15, 2011 #8
    yeah im sort of new to this so its taking a while. thanks
     
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