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#1451 01/22/20 02:24 PM
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I came across a report that listed fatigue testing of steel that was peened with S170 size cast steel(HRC 65) and ceramic shot to an intensity of 10A. The hardness of the ceramic shot was comparable to the steel. The average fatigue failure was about 25% higher in the samples peened with cast steel shot. Any ideas on what could have contributed to such a drastic difference in fatigue testing results?

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Can you identify the report? I would like to read it.

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I just sent it to your email. The ceramic bead is 6-7 MOHS which is in the ballpark of 65HRC. The data doesnt follow any of the expected trends such as the bead size and the affect of the resulting surface finish on fatigue strength. This report was mentioned in other reports i saw online.

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It is not possible to make any sensible comment without seeing the actual report.

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Having read the report several times I failed to identify the issue raised! On page 10 of the report, S170 cast steel shot with a hardness of Rc 65 peening to 10A gave a mean cycles to failure of 25,086 for the 6 samples tested. On page 11 of the report, S170 ceramic shot with a hardness of MOH 6-7 peening to 10A gave a mean cycles to failure of 20,189 for the 6 samples tested.

The data is not consistent with: "The average fatigue failure was about 25% higher in the samples peened with cast steel shot." Fatigue failure rate is lower the larger the number of cycles to failure!

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"The average fatigue failure was about 25% higher in the samples peened with cast steel shot". Rephrasing the report can give different interpretation.
"The steel provided a 25% increase in fatigue life" seems like the proper way interpret the report.
But, again, why should there be such a difference between steel shot and ceramic bead?


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