Experimental investigation of the effects of artificial wedges on fatigue crack growth and crack closing behavior in annealed SAE1045 steel

Mitsuhiro Okayasu, Zhirui Wang

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

To better understand the effect of asperity on the crack closure and fatigue crack growth behavior, the load-CMOD relations and crack propagation rate were examined through the addition of artificial wedges into pre-cracks. Experimental results revealed that the unloading phase of the load vs. CMOD curve exhibited always a concave shape, signifying the acceleration in the CMOD decrease. This was related to the plastic deformation in the wedge as well as in the specimen material surrounding the wedge. With the addition of an artificial wedge, reduced fatigue crack growth rate was found. The crack growth rate was then correlated with the effective load intensity factor range, ΔPeff = Pmax - Pmin,real, which itself was correlated also to the deformation severity in the asperity as well as in the specimen material. Furthermore, the ΔPeff value was found to change with increasing the crack length. In a short crack range, approximately 0.1 mm crack length, the value of ΔPeff decreased due to the asperity- and plasticity-induced crack closing behavior. As the crack length increased, the ΔPeff value increased as well due to the reduction in the closing behavior until just prior to the final fracture. Based upon the ΔPeff variation as a function of crack length, details of the crack closing behavior were further discussed.

Original languageEnglish
Pages (from-to)962-976
Number of pages15
JournalInternational Journal of Fatigue
Volume29
Issue number5
DOIs
Publication statusPublished - May 2007
Externally publishedYes

Fingerprint

Fatigue Crack Growth
Steel
Fatigue crack propagation
Wedge
Experimental Investigation
Crack
Cracks
Crack Growth Rate
Crack propagation
Crack Closure
Intensity Factor
Crack closure
Crack Propagation
Plastic Deformation
Unloading
Plasticity
Range of data
Plastic deformation
Decrease
Curve

Keywords

  • Artificial asperity
  • Crack closure
  • Crack driving force
  • Crack growth rate
  • Crack opening displacement

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials

Cite this

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title = "Experimental investigation of the effects of artificial wedges on fatigue crack growth and crack closing behavior in annealed SAE1045 steel",
abstract = "To better understand the effect of asperity on the crack closure and fatigue crack growth behavior, the load-CMOD relations and crack propagation rate were examined through the addition of artificial wedges into pre-cracks. Experimental results revealed that the unloading phase of the load vs. CMOD curve exhibited always a concave shape, signifying the acceleration in the CMOD decrease. This was related to the plastic deformation in the wedge as well as in the specimen material surrounding the wedge. With the addition of an artificial wedge, reduced fatigue crack growth rate was found. The crack growth rate was then correlated with the effective load intensity factor range, ΔPeff = Pmax - Pmin,real, which itself was correlated also to the deformation severity in the asperity as well as in the specimen material. Furthermore, the ΔPeff value was found to change with increasing the crack length. In a short crack range, approximately 0.1 mm crack length, the value of ΔPeff decreased due to the asperity- and plasticity-induced crack closing behavior. As the crack length increased, the ΔPeff value increased as well due to the reduction in the closing behavior until just prior to the final fracture. Based upon the ΔPeff variation as a function of crack length, details of the crack closing behavior were further discussed.",
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author = "Mitsuhiro Okayasu and Zhirui Wang",
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AB - To better understand the effect of asperity on the crack closure and fatigue crack growth behavior, the load-CMOD relations and crack propagation rate were examined through the addition of artificial wedges into pre-cracks. Experimental results revealed that the unloading phase of the load vs. CMOD curve exhibited always a concave shape, signifying the acceleration in the CMOD decrease. This was related to the plastic deformation in the wedge as well as in the specimen material surrounding the wedge. With the addition of an artificial wedge, reduced fatigue crack growth rate was found. The crack growth rate was then correlated with the effective load intensity factor range, ΔPeff = Pmax - Pmin,real, which itself was correlated also to the deformation severity in the asperity as well as in the specimen material. Furthermore, the ΔPeff value was found to change with increasing the crack length. In a short crack range, approximately 0.1 mm crack length, the value of ΔPeff decreased due to the asperity- and plasticity-induced crack closing behavior. As the crack length increased, the ΔPeff value increased as well due to the reduction in the closing behavior until just prior to the final fracture. Based upon the ΔPeff variation as a function of crack length, details of the crack closing behavior were further discussed.

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