Journal of
Chemical Engineering and Materials Science

  • Abbreviation: J. Chem. Eng. Mater. Sci.
  • Language: English
  • ISSN: 2141-6605
  • DOI: 10.5897/JCEMS
  • Start Year: 2010
  • Published Articles: 77

Full Length Research Paper

A constitutive model on flow stress prediction from the contribution of twin and grain refinement, strain and strain rate during surface mechanical attrition treatment of metals

Wing Yan LEUNG
  • Wing Yan LEUNG
  • Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
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San Qiang SHI
  • San Qiang SHI
  • Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
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Jian LU
  • Jian LU
  • Department of Mechanical and Biomedical Engineering, City University of Hong Kong, China.
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Hai Hui RUAN
  • Hai Hui RUAN
  • Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
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Li Min ZHOU
  • Li Min ZHOU
  • Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hong Kong, People's Republic of China.
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  •  Received: 20 January 2016
  •  Accepted: 12 July 2016
  •  Published: 30 September 2016

Abstract

A new constitutive equation is developed to model the flow stress on a metal surface undergone high speed impacts that result in strain hardening. The new equation is based on the Johnson-Cook model and has considered the effects of strain, strain rate, grain refinement, twin formation and twin spacing. Two mechanisms for the strain hardening are proposed: Grain refinement or twin formation, depending on the strain rate. At low strain rate, the Hall-Petch relation is obeyed, while at high strain rate, the flow stress is controlled by the formation of deformation twins. The theoretical estimation of flow stress agrees well with experimental data for stainless steel 304. According to the new model, the flow stress can be as high as 1.46 GPa at a strain rate of 105 /s.

 

Keywords: SMAT, flow stress, grain refinement, twin spacing, metal plasticity.