Improve Fatigue Life with Shot Peening: Compressive Stress Benefits

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Discussion Overview

The discussion centers on the effects of shot peening on fatigue life, specifically how compressive surface stress contributes to this improvement. It also touches on the relationship between material properties, such as elastic modulus and grain size, and their influence on creep behavior.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about the mechanisms by which shot peening enhances fatigue life through compressive surface stress.
  • Another participant questions how materials with high elastic moduli and large grain sizes can prevent creep, suggesting a need for clarification on these concepts.
  • A participant expresses uncertainty about proving the effects of shot peening and creep, indicating reliance on notes and external sources without full understanding.
  • A later reply reiterates the initial questions and expands on them, asking about the nature of fatigue, the stress states involved, and the atomic mechanisms of creep, particularly in relation to material stiffness and grain boundaries.

Areas of Agreement / Disagreement

Participants do not appear to reach consensus on the mechanisms involved in shot peening and creep prevention, with multiple viewpoints and questions remaining unresolved.

Contextual Notes

Some assumptions regarding the definitions of fatigue and creep may be implicit, and the discussion does not resolve the mathematical or theoretical aspects of the proposed mechanisms.

zewei1988
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How does shot peening help improve fatigue life, or rather, how does the compressive surface stress imposed help improve fatigue life?

How does materials having high elastic moduli and large grain size prevent creep?
 
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We won't just give you the answers to homework-type questions at PF (that way nobody would learn anything), but if you give proposed answers and try to justify them, you'll likely get comments.
 
It's not a homework question, but I have no idea of how to prove it to you. It's something that was mentioned in my notes, and I tried checking Wikipedia and my recommended textbook, but I still do not understand those two points.
 
Let me try answering this way...

zewei1988 said:
How does shot peening help improve fatigue life, or rather, how does the compressive surface stress imposed help improve fatigue life?

What is fatigue, and what stress state does it involve?

zewei1988 said:
How does materials having high elastic moduli and large grain size prevent creep?

What is the atomic mechanism of creep? How might this mechanism be affected when the atoms are more strongly bound (which is how materials acquire high stiffness, or elastic modulus), or when there are fewer grain boundaries (look up Coble creep)?
 

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