Fatigue Testing: Calculating ΔK vs da/dN from R & Max Stress

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The discussion focuses on calculating ΔK versus da/dN for a Single Edge Notched Tension (SENT) sample in fatigue testing. The user seeks guidance on plotting these values using data from different R and maximum stress readings, referencing ASTM E647 for assistance. A suggestion is made to consult MIL-HDBK-5H, which, despite being superseded, contains valuable information and is accessible online. The handbook includes a figure that summarizes a step-by-step process for the calculations. This resource may provide the necessary clarity to complete the lab report effectively.
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Hello Everybody,

Im doing my lab report on Fatigue testing for a Single Edge Notched Tension (SENT) sample and need to plot ΔK vs da/dN for a series of a vs N readings at different R and maximum stress values (attached in the picture). I've just been given one equation for Ki and told that I need to use ASTM E647 for assistance (attached equation). However after hours of going through it I was unable to figure out how to get ΔK vs da/dN from the data and information. Any step by step help would be highly appreciated. Please please.

Thanks
 

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There is a discussion of this starting on page 9-147 in MIL-HDBK-5H. That handbook has been superseded, but it is full of good information AND is available online. Just search MIL-HDBK-5H to find a copy. This figure summarizes two pages of step by step discussion that should help you.
DaDN.jpg
 

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