Section 1c - Fatigue Design Methods

Section 1c - Fatigue Design Methods - Chapter Chapter 2...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
hapter 2 atigue Design Methods Chapter 2 Fatigue Design Methods Infinite-Life Design Safe-Life Design amage olerant Design Damage-Tolerant Design ail- afe Design Fail Safe Design 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 Design Flow Chart 2
Background image of page 2
Fatigue Design Concepts Relate to Crack Sizes law size Flaw size None 1 m 10 m 0.1 mm 1 mm Large damage Safe-life Durability Damage tolerance Fail-safe Small- crack theory o Economic- life extension o Inspectable flaw size o Redundant structure o Hidden or uninspectable structure o Manufacturing- and service-induced damage o EIFS to fit S-N or ehavior esign 3 or -N behavior Design concept
Background image of page 3

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

View Full DocumentRight Arrow Icon
Strategies in Fatigue Design Four fatigue-life models exist: (1) Nominal stress-life ( S-N ) method. - First formulated in the 1850s to 1870s. - Used nominal (net-section) stresses and relates these to ( ) local fatigue strengths for notched and unnotched members. (2) Local strain-life ( -N ) method - First formulated in the 1960s - Local strain at a notch is related to smooth specimen strain-controlled fatigue behavior. - Analytical models can be used to determine local strains 4 from global or nominal stresses or strains.
Background image of page 4
Strategies in Fatigue Design (cont.) (3) Fatigue-crack-growth ( da/dN- K ) method. - First formulated in the 1960s. equires the use of fracture mechanics to obtain the - Requires the use of fracture mechanics to obtain the number of cycles to grow a crack from a given crack length to another length and/or to fracture. - This model can be considered a total fatigue-life model when used in conjunction with an existing initial crack size from the microstructure and/or manufacturing. (4)
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/08/2011 for the course MECHANICAL 8253 taught by Professor Newman during the Spring '11 term at Mississippi State.

Page1 / 18

Section 1c - Fatigue Design Methods - Chapter Chapter 2...

This preview shows document pages 1 - 6. Sign up to view the full document.

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