Effect of a hard artificial asperity on the crack closure behavior in an annealed SAE 1015 steel

Mitsuhiro Okayasu, Zhirui Wang, D. L. Chen

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The load - Crack opening displacement (COD) curves and deformation characteristics in the vicinity of a hard artificial asperity in an annealed SAE 1015 steel were studied. The artificial asperity was found to have a significant effect on the trend of the load - COD curves. The lower portion of the load - COD curves in the unloading phase exhibited a convex shape without the asperity, but a concave shape with the asperity. The concave shape, signifying the acceleration in the COD decrease, was further verified by varying the size of the asperity, conducting special compression tests and elastic - Plastic load - COD tests. The plastic deformation in the vicinity of both asperity and crack tip was studied via microhardness tests, etching techniques, and finite element analysis. Based on the experimental observations, a modified crack closure process model was proposed, where three stages of the unloading curve was defined: (i) the asperity does not contact the upper crack face, (ii) a process where both the asperity and the specimen material deform elastically, and the elastic-wedge model is applicable, and (iii) the plastic deformation of the specimen material adjacent to the asperity occurs, thus resulting in the concavely shaped load - COD curves. An equation was proposed to estimate the COD values, in which the plastic deformation both at the crack tip and at the asperity was considered. The residual COD calculated from the proposed equation was found to be consistent with the experimental results.

Original languageEnglish
Pages (from-to)2106-2127
Number of pages22
JournalEngineering Fracture Mechanics
Volume72
Issue number13
DOIs
Publication statusPublished - Sep 2005
Externally publishedYes

Fingerprint

Crack closure
Steel
Cracks
Plastic deformation
Unloading
Crack tips
Microhardness
Etching
Compaction
Plastics
Finite element method

Keywords

  • Artificial asperity
  • Crack closure
  • Crack opening displacement (COD)
  • Plastic deformation
  • SAE 1015 steel

ASJC Scopus subject areas

  • Mechanical Engineering
  • Mechanics of Materials

Cite this

Effect of a hard artificial asperity on the crack closure behavior in an annealed SAE 1015 steel. / Okayasu, Mitsuhiro; Wang, Zhirui; Chen, D. L.

In: Engineering Fracture Mechanics, Vol. 72, No. 13, 09.2005, p. 2106-2127.

Research output: Contribution to journalArticle

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