Plotting S-N Diagram with Cycles to Failure

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Discussion Overview

The discussion revolves around how to plot an S-N diagram using provided data on stress amplitude and cycles to failure. Participants explore the appropriate methods for visualizing this data, particularly focusing on the use of logarithmic scales.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant expresses confusion about how to handle the 'cycles to failure' figures in the context of plotting an S-N diagram.
  • Another participant suggests using a log-log plot for S-N curves due to the nature of the data.
  • A question is raised about the rationale behind using a log-log plot versus plotting stress against the logarithmic scale of cycles to failure.
  • It is noted that using a log-log plot often results in the S-N curve appearing as a straight line, which some participants find convenient.
  • A participant provides a detailed explanation of converting scientific notation into standard form and how to calculate logarithmic values for plotting.
  • There is an acknowledgment of the participant's inexperience with scientific notation and plotting techniques.

Areas of Agreement / Disagreement

Participants generally agree on the utility of a log-log plot for visualizing the S-N curve, but there is some debate regarding the best approach to plotting the data. The discussion remains unresolved regarding the optimal method for the specific case presented.

Contextual Notes

Some participants express uncertainty about scientific notation and its application in plotting, indicating a potential gap in foundational knowledge that may affect the discussion.

qwerty0123
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how do i plot the follwing S-N diagram, i am having trouble with what I am 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?
 
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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.
 
SteamKing said:
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.

ok...so how would i go about doing that?
 
SteamKing said:
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.

why would you recommend a log-log plot? can i not just plot it as stress against logarithmic scale of the cycles to failure?
 
You can. But often if a log-log plot is used, the S-N curve plots as a straight line, which is really handy.
 
SteamKing said:
You can. But often if a log-log plot is used, the S-N curve plots as a straight line, which is really handy.

well...i've decided to plot stress against the logarithm of the N-values? could you please show me how I am supposed to deal with the figures 3 and 3.7?
 
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.
 
SteamKing said:
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.

yeah I am sort of new to this so its taking a while. thanks
 

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