Examining failure behaviour of commercially pure titanium during tensile deformation and hole expansion test

J.S Kwame, E. Yakushina, P. Blackwell

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Hole expansion ratio is a material parameter which defines the extent to which sheet metals are formed. Research has shown that, the stress state observed at the hole edge after hole expansion test is similar to those observed during conventional uniaxial tensile test. However, conventional tensile test methods are not efficient in evaluating material edge formability. This work utilised optical non-contact measuring techniques to examine failure behaviour during tensile test and hole expansion test of commercially pure titanium sheet, fabricated with either abrasive water jet cutting or electric discharge machining. The work found that, the deformation mode in conventional tensile testing are governed by localised necking and subsequently diffused necking prior to failure. Deformation mode observed in hole expansion test is characterised by localised necking with no visible occurrence of diffused necking prior to failure. The highest strains are concentrated at the hole edge during hole expansion test due to their sensitivity to the hole preparation method with accompanying multiple localised necking sites resulting in non-uniform deformation. Strains become concentrated in the bulk material microstructure rather than the machined edge during tensile testing resulting in single localised deformation site and a more homogenous deformation.
Original languageEnglish
Pages (from-to)32-37
Number of pages6
JournalJournal of Materials and Applications
Issue number1
Early online date10 May 2020
Publication statusPublished - 15 May 2020


  • titanium alloys
  • tensile deformation;
  • hole expansion test
  • edge conditions
  • failure mode
  • uniaxial stress state


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