In situ SEM testing for crack closure investigation and virtual crack annealing model development

Wei Zhang, Yongming Liu

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

In this paper, an in situ scanning electron microscope (SEM) fatigue testing approach is proposed to investigate the crack closure phenomenon within one cyclic loading under plane stress conditions. One objective of this experimental study is to verify the existence and significance of crack closure by directly measuring the variation of crack tip opening displacement (CTOD) and evaluating the crack opening stress levels. During the testing, the loading cycle is divided into a certain number of levels. At each level, high resolution images are taken around the crack tip region by SEM. Following this, imaging analysis is used to process these images in order to quantify the crack tip behavior at any time instant. Four constant amplitude loading cases with different stress ratios are investigated. Crack closure phenomenon is directly observed and measured. A simple mechanical model (named virtual crack annealing model) is developed based on the in situ SEM testing observations. The calculated crack opening stress level is compared with experimental observations. A detailed discussion is given based on the current investigation to explain some well-known issues in the classical fatigue theory.

Original languageEnglish (US)
Pages (from-to)188-196
Number of pages9
JournalInternational Journal of Fatigue
Volume43
DOIs
StatePublished - Oct 2012
Externally publishedYes

Fingerprint

Crack Closure
Crack closure
Scanning Electron Microscope
Crack Tip
Annealing
Crack
Electron microscopes
Crack tips
Cracks
Scanning
Fatigue
Testing
Cyclic Loading
Plane Stress
Instant
Fatigue testing
Experimental Study
Quantify
High Resolution
Image resolution

Keywords

  • Crack closure
  • Fatigue crack growth
  • In situ SEM
  • Virtual crack annealing

ASJC Scopus subject areas

  • Industrial and Manufacturing Engineering
  • Mechanical Engineering
  • Mechanics of Materials
  • Materials Science(all)
  • Modeling and Simulation

Cite this

In situ SEM testing for crack closure investigation and virtual crack annealing model development. / Zhang, Wei; Liu, Yongming.

In: International Journal of Fatigue, Vol. 43, 10.2012, p. 188-196.

Research output: Contribution to journalArticle

@article{4268fa04ff654a40ac03390bb0b9c01c,
title = "In situ SEM testing for crack closure investigation and virtual crack annealing model development",
abstract = "In this paper, an in situ scanning electron microscope (SEM) fatigue testing approach is proposed to investigate the crack closure phenomenon within one cyclic loading under plane stress conditions. One objective of this experimental study is to verify the existence and significance of crack closure by directly measuring the variation of crack tip opening displacement (CTOD) and evaluating the crack opening stress levels. During the testing, the loading cycle is divided into a certain number of levels. At each level, high resolution images are taken around the crack tip region by SEM. Following this, imaging analysis is used to process these images in order to quantify the crack tip behavior at any time instant. Four constant amplitude loading cases with different stress ratios are investigated. Crack closure phenomenon is directly observed and measured. A simple mechanical model (named virtual crack annealing model) is developed based on the in situ SEM testing observations. The calculated crack opening stress level is compared with experimental observations. A detailed discussion is given based on the current investigation to explain some well-known issues in the classical fatigue theory.",
keywords = "Crack closure, Fatigue crack growth, In situ SEM, Virtual crack annealing",
author = "Wei Zhang and Yongming Liu",
year = "2012",
month = "10",
doi = "10.1016/j.ijfatigue.2012.04.003",
language = "English (US)",
volume = "43",
pages = "188--196",
journal = "International Journal of Fatigue",
issn = "0142-1123",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - In situ SEM testing for crack closure investigation and virtual crack annealing model development

AU - Zhang, Wei

AU - Liu, Yongming

PY - 2012/10

Y1 - 2012/10

N2 - In this paper, an in situ scanning electron microscope (SEM) fatigue testing approach is proposed to investigate the crack closure phenomenon within one cyclic loading under plane stress conditions. One objective of this experimental study is to verify the existence and significance of crack closure by directly measuring the variation of crack tip opening displacement (CTOD) and evaluating the crack opening stress levels. During the testing, the loading cycle is divided into a certain number of levels. At each level, high resolution images are taken around the crack tip region by SEM. Following this, imaging analysis is used to process these images in order to quantify the crack tip behavior at any time instant. Four constant amplitude loading cases with different stress ratios are investigated. Crack closure phenomenon is directly observed and measured. A simple mechanical model (named virtual crack annealing model) is developed based on the in situ SEM testing observations. The calculated crack opening stress level is compared with experimental observations. A detailed discussion is given based on the current investigation to explain some well-known issues in the classical fatigue theory.

AB - In this paper, an in situ scanning electron microscope (SEM) fatigue testing approach is proposed to investigate the crack closure phenomenon within one cyclic loading under plane stress conditions. One objective of this experimental study is to verify the existence and significance of crack closure by directly measuring the variation of crack tip opening displacement (CTOD) and evaluating the crack opening stress levels. During the testing, the loading cycle is divided into a certain number of levels. At each level, high resolution images are taken around the crack tip region by SEM. Following this, imaging analysis is used to process these images in order to quantify the crack tip behavior at any time instant. Four constant amplitude loading cases with different stress ratios are investigated. Crack closure phenomenon is directly observed and measured. A simple mechanical model (named virtual crack annealing model) is developed based on the in situ SEM testing observations. The calculated crack opening stress level is compared with experimental observations. A detailed discussion is given based on the current investigation to explain some well-known issues in the classical fatigue theory.

KW - Crack closure

KW - Fatigue crack growth

KW - In situ SEM

KW - Virtual crack annealing

UR - http://www.scopus.com/inward/record.url?scp=84861341001&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84861341001&partnerID=8YFLogxK

U2 - 10.1016/j.ijfatigue.2012.04.003

DO - 10.1016/j.ijfatigue.2012.04.003

M3 - Article

AN - SCOPUS:84861341001

VL - 43

SP - 188

EP - 196

JO - International Journal of Fatigue

JF - International Journal of Fatigue

SN - 0142-1123

ER -