Local zone wise elastic and plastic properties of electron beam welded Ti–6Al–4V alloy using digital image correlation technique: A comparative study between uniform stress and virtual fields method

K M, Saranath and M, Ramji (2015) Local zone wise elastic and plastic properties of electron beam welded Ti–6Al–4V alloy using digital image correlation technique: A comparative study between uniform stress and virtual fields method. Optics and Lasers in Engineering, 68. pp. 222-234. ISSN 0143-8166

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Joining of materials using welding results in the formation of material zones with varying microstructure across the weld. Extraction of the mechanical properties of those individual heterogeneous zones are important in designing components and structures comprised of welds. In this study, the zone wise local extraction of the elastic and plastic properties of an electron beam welded Ti–6Al–4V titanium alloy has been carried out using both the uniform stress method (USM) and the virtual fields method (VFM) involving digital image correlation (DIC) technique. The surface strain field obtained using DIC technique from a transverse weld specimen tensile testing is used for extracting the zone wise strain evolution. Initially, using uniform stress assumption, zone wise full range stress–strain curves are extracted. In USM methodology, the elastic and plastic material models are fitted to the zone wise stress–strain curves and required parameters are extracted from it. But inherent disadvantage is lot of images need to be processed for the parameter extraction. Recently, VFM is gaining lot of popularity in characterization domain as it is robust, accurate and faster. VFM is based on the principle of virtual work where, the weak form of local equilibrium equations and kinematically admissible virtual displacement fields are utilized for parameter extraction. Hollomon׳s power law is used here as the hardening rule. Young׳s modulus, Poisson׳s ratio, yield stress, strength coefficient and strain hardening exponent are the parameters extracted zone wise using both USM and VFM. A Vicker׳s microhardness measurement is also conducted across the weld zone towards mapping the strength behavior. Fusion zone has reported higher yield strength, strength coefficient and Poisson׳s ratio. Young׳s modulus value is found decreasing from base metal towards the fusion zone. The trend observed in parameter variation across the weld zone obtained by both USM and VFM compares very well. Due to various advantages associated with VFM technique it is generally recommended for parameter extraction.

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Item Type: Article
Additional Information: The authors wish to thank Mr. Manish Meshram, M.Tech. student and Mr. Dan Sathiraj, Ph.D. scholar, Material Science Lab, IIT Hyderabad for helping in microhardness and micrographic examination. We would like to thank Mr. Naresh Reddy Kolanu, M.Tech. student, Engineering Optics Lab, IIT Hyderabad for assisting in conducting tensile testing. Also we wish to thank Gas Turbine Research Establishment (GTRE), CARS Project, Project no: GTRE/MMG/BMR1/1225/CARS/A/13 Dt. 04/10/13, DRDO, Bangalore, for providing us the electron beam welded Ti-64 sheet.
Uncontrolled Keywords: Constitutive parameters; Digital image correlation; Electron beam welding; Ti-6Al-4V alloy; Virtual fields method
Subjects: ?? sub4.9 ??
Divisions: Department of Physics
Depositing User: Team Library
Date Deposited: 18 Feb 2015 07:52
Last Modified: 24 Sep 2015 06:13
URI: http://raiith.iith.ac.in/id/eprint/1338
Publisher URL: http://dx.doi.org/10.1016/j.optlaseng.2015.01.005
OA policy: http://www.sherpa.ac.uk/romeo/issn/0143-8166/
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