F.D.+E. Calculation Wrappers for SAE Standard Files

F.A. Conle
member of Fatigue Design & Evaluation Committee of SAE
March 25, 1999, update 2012
Web page: https://fde.uwaterloo.ca/Fde/saewrap1.html


The Fatigue Design and Evaluation Committee of the SAE is experimenting
with standard file formats for various types of fatigue data. A useful
addition to this process is the creation of calculation, edit and
display capability. The normal computer calculation process usually
requires that one buy or download some files from the internet and then
run the program on one's local computer. Often this entails serious
user interaction with the operating system, and is thus "unsavory" for
many users. It would be much more pleasant to be able to "click" on a
web page button and get the calculation job done by experts or standard
calculation tools.. This is now possible
on many web pages. Generally one uses a web browser to fetch a page
with a "form" to be filled in and a clickable button to send it away
for analysis. The process is still somewhat painful in that one has
to type or cut & paste a local file into the text fields of the
web "form".

The Quick/Easy Way for Stress-Strain-Life Fatigue Data:

  1. Open the example file in a web browser:
    __________Example Html File___________

  2. Using your browser edit the file's lines in the text box.
    Adjust the "Copyright (C)..." lines to suit your own data.
    You must have a value for the elastic modulus in the
    line. NOTE!: Do NOT use TAB to seperate columns. Use 1 or more spaces.

  3. Use the "Submit" button to view the file's results.

  4. Use the "Back" button to review and edit. Then re-submit.

  5. When things work to your satisfaction use the browser
    "View Source" option to see the complete file in a
    window. Highlight all the text and copy and paste it
    into a file on your disk.
  6. Suggestion: edit the example file in small sections and between
    each edit "Submit" the file and view the changes. That way if the
    file chrashes out for some reason, it will be easier to determine the cause.

The Calculation Wrapper Process in Detail:

If you have lots of files that you wish to convert to standard SAE format and to also add calculation wrappers, the above quick method may become tedious. You may wish to automate the process by writing a "script" or other program to do the conversions. Details of such a process are descibed below.

Graphical Explanation 1.1Kb gif


  1. Create standard file(s) on your computer.
    In the present case, a standard file implies one of the new SAE/F.D.+E.
    standard files for strain-life data, stress-strain data, or rainflow
    data. Each has a specific, yet simple, format specified by FD&E or SAE.
    The user can either create his own file with any text editor, or in many
    cases the data may originate from a testing center or other supplier.

    Examples of standard files:
    #FileType= strain_life    # in the case of strain life files
    #FileType= rainflow       # in the case of rainflow files
     and the line :
    #DataType= raw      #"raw"= measured, as opposed to "fitted"
    Which could be made part of the "standard" SAE file definition?
    The two lines simply tell the calculation site what kind of standard
    files to expect. At this time the rainflow one does not work
    on this site yet.

  2. The user then places a "Calc Wrapper" around the standard file. This consists of 5 or 6 lines of text at the top of the file and 2 lines at the bottom of the file.
    The wrapped file is saved back on the user's own disk.
    Examples :
The file is then automatically sent to one of the experimental
F.D.& E. calculation sites, is plotted or analysed according to
its type and the user option settings, and then returned to the user
for display on his web browser. A simple pre-wrapped
test file is available for
you to try. (You will have to use the scrollbar to read it all.)


Ok, you may have tried this once and yes its cute, but... you might ask:
"How will this help me do my metal fatigue (or anything else for that matter) job better?
Here are some things to contemplate.



Just for fun, one could ask, "Where could all this lead?". Here is some speculation on what might be useful (if you think of more, send & we will post them):

How to Proceed?

Can't spoil all the fun. Besides we don't really know if any of this is worth beans. I guess its a good topic for an FD&E planning meeting? Anyone who asks the managerial "When will you have this done" will have to buy all present a beer.
Page comments to : conle(a)mecheng1*uwaterloo*ca
Last update April 14, 1999.