lecture12 - Lecture Lecture 12 Fatigue & Creep in...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 12 Fatigue & Creep in Engineering Materials (Chapter 8) Chapter 8 - 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Fatigue Fatigue = failure under applied cyclic stress. compression on top specimen counter motor flex coupling bearing bearing • Stress varies with time. -- ey parameters are and max tension on bottom key parameters are S , m , and cycling frequency min time m S • Key points: Fatigue. .. --can cause part failure, even though max < y . Chapter 8 - 2 --responsible for ~ 90% of mechanical engineering failures.
Background image of page 2
Fatigue: Definitions Symmetric Asymmetric Random Chapter 8 - 3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Fatigue: Definitions Chapter 8 - 4
Background image of page 4
Types of Fatigue Behavior Fatigue limit , S fat : --no fatigue if S < S fat case for steel (typ.) unsafe mplitude S fat safe = stress a N = Cycles to failure 10 3 10 5 10 7 10 9 S • For some materials, there is no fatigue case for Al (typ.) unsafe amplitude limit! safe = stress a Chapter 8 - 5 N = Cycles to failure 10 3 10 5 10 7 10 9
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Ex: Fatigue in 7075-T6 Aluminum Alloy Chapter 8 - 6
Background image of page 6
Rate of Fatigue Crack Growth Crack grows incrementally typ. 1 to 6 d a   a ~ crease in crack length per loading cycle   m K dN increase in crack length per loading cycle Failed rotating shaft -- rack grew even though crack origin crack grew even though K max < K c -- crack grows faster as creases  increases crack gets longer loading freq. increases. Chapter 8 - 7
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Fatigue Failure in Ductile Materials (Aluminum) Chapter 8 - 8
Background image of page 8
Fatigue Failure in Brittle Material Chapter 8 - 9
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Importance of Mean Stress Chapter 8 - 10
Background image of page 10
Improving Fatigue Life Adapted from Fig. 8.24, Callister & ethwisch 8e 1. Impose compressive surface stresses amplitude Rethwisch 8e.
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 27

lecture12 - Lecture Lecture 12 Fatigue &amp; Creep in...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online