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

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SUMMARY

The forum discussion centers on fatigue testing for a Single Edge Notched Tension (SENT) sample, specifically focusing on plotting ΔK versus da/dN using various R and maximum stress values. The user references ASTM E647 for guidance and mentions an equation for Ki. Additionally, they highlight the relevance of MIL-HDBK-5H, which, despite being superseded, contains valuable information for understanding the calculations involved in fatigue testing. The discussion emphasizes the need for a step-by-step approach to derive ΔK from the provided data.

PREREQUISITES
  • Understanding of fatigue testing principles
  • Familiarity with ASTM E647 standards
  • Knowledge of Single Edge Notched Tension (SENT) samples
  • Ability to interpret data from MIL-HDBK-5H
NEXT STEPS
  • Review ASTM E647 for detailed methodologies on fatigue crack growth rate
  • Study the equations related to ΔK and da/dN in fatigue analysis
  • Examine MIL-HDBK-5H for historical context and practical examples
  • Practice plotting ΔK versus da/dN using sample data sets
USEFUL FOR

Researchers, engineers, and students involved in materials science, particularly those focusing on fatigue testing and fracture mechanics.

arehman1289
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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 That handbook has been superseded, but it is full of good information AND is available online.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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