[aaron_js]

I deal with sheet metal fabrication and one of my customers has asked me to provide an S-N (stress vs. no of cycles to failure) curve for the materials that I am using.
Does any one know how to generate such a curve? The materials I am using are:
1) SAILMA 450 HI (thickness 10 mm)
2) SAILMA 350 HI (thickness 5 and 6 mm)
3) IS 2062 Gr. B (thickness 5 mm)
4) IS 5986 Fe 410 (thickness 3.15 mm)
The chemical and mechanical properties are on page 5 and 6 of the website - http://www.sail.co.in/Salem_Userguide.pdf

[Hack]

Unfortunately, the link does not give any data that will produce a S-N curve for you. At least not anything I saw glancing through it.

S-N curves are easy to produce if the data (test) is already done. On a piece of graph paper draw an x axis and a y axis line. On the Y axis you would chart the Stress and on the X axis, chart the # of cycles to failure.

In order to produce your own tests, a test apparatus should be designed to duplicate (as nearly as possible) the service conditions that the final product will see. This includes stress level applied to the part, time frequency (how often the force is applied) and stress pattern. Apply a given force and number of times until a part fails. From there increase the force, repeat the test and record when the part fails with the increased force. Keep repeating this until you have a bevy of numbers to plot on the X,y chart mentioned above.


Do a search for S-N curves on the net and you will get some great examples. If you need specifics, give me a shout.

Dan

[aaron_js]

Thanks Dan. To be more precise, I fabricate centrifugal blowers using sheet metal. How would such a test be done on these blowers?
The S-N curve that my customer wants is something like what is on page 4 and 5 of this link http://www.tatasteeleurope.com/file_...rm%20XF350.pdf
Do you have any thoughts on the matter? I have already approached the material supplier, but have not been able to obtain the information.