# Creating S-N Diagrams with Excel

• fmunene
In summary, To plot a S-N curve using Excel, you will need to compute the stress (S) using the formula S = 32*M/(pi*d^3), where M is the moment and d is the average diameter. The number of cycles (N) will be plotted on the x-axis and S on the y-axis. Make sure to use the log-log display option when plotting the graph to accurately represent the data.
fmunene
Hello, I need help
with plotting a S-N curve using Excel given the data below
I know how to plot using the scatter function in excel but i am confused on what values should go on the y-axis...i.e S...it is clear that the number of cycles will obviously go onto the x-axis...Please explain what excel equations I need to get . Any help will be highly appreciated.

"Average Diameter [in]","Moment [in-lb]","Number Cycles [N]"
0.25, 122.718463, 20000
0.2513, 101.2723101, 40000
0.2496, 91.59776729, 100000
0.2503, 76.97548741, 200000
0.2506, 61.80207912, 500000
0.2513, 52.1941906, 1000000
0.251, 46.5738686, 2000000
0.2513, 38.95088851, 5000000
0.2503, 33.09945959, 10000000
0.2506, 30.90103956, 100000000

fmunene: Compute stress, S = 32*M/(pi*d^3), where d = diameter. After you plot S versus N, display the graph with the log-log display option.

## What is an S-N diagram?

An S-N diagram, also known as a stress-life or Wöhler curve, is a plot of the stress amplitude versus the number of cycles to failure for a material. It is used to determine the fatigue life of a material and is an important tool in engineering and materials science.

## Why is creating S-N diagrams with Excel useful?

Excel is a widely used and easily accessible program that allows scientists and engineers to quickly and accurately plot S-N diagrams. It also has built-in features such as trendline fitting and data analysis that can aid in analyzing and interpreting the data.

## How do I create an S-N diagram in Excel?

To create an S-N diagram in Excel, you will need to input the stress amplitude and number of cycles to failure data in two separate columns. Then, select the data and insert a scatter plot. Next, add a trendline and choose the appropriate equation type for your data. Finally, add axis labels and a legend to complete the diagram.

## What are some common mistakes to avoid when creating S-N diagrams with Excel?

One common mistake is not inputting the data correctly, which can lead to incorrect results. It's important to double-check your data and make sure it is in the correct format. Another mistake is not choosing the correct trendline equation for your data, which can also result in inaccurate results.

## Are there any limitations to creating S-N diagrams with Excel?

While Excel is a useful tool for creating S-N diagrams, it does have some limitations. For example, it may not be suitable for complex or non-linear data. It's important to consider the limitations of the program and ensure that it is appropriate for your specific data before using it to create an S-N diagram.

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