Observation and numerical simulation of an elastic-plastic solid loaded by a spherical indenter
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Wei Li School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006, Australia
Michael V. Swain School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006, Australia; and Biomaterials Science Research Unit, Faculty of Dentistry, University of Sydney, United Dental Hospital, Surry Hills, NSW 2010, Australia (Received 2 May 2004; accepted 8 July 2004)
The observation and finite element simulation of Ti–6Al–4V loaded by a spherical indenter were compared. The contact radius at the maximum load was 40% of the indenter radius, which resulted in a high degree of plasticity induced beneath the indenter. The spherical impression profile predicted by the simulation was in agreement with that of the observation. The local curvature of the spherical impression was shown to vary with radial distance. The overall curvature change with radial distance was more distinctive in the presence of static friction. Due to the large plastic zone in the material, neither the Field–Swain nor the Oliver–Pharr method was able to predict the elastic recovery depths in the center of indentation and at the perimeter of contact. The ratio of the two depths predicted by the latter method, however, may be used to verify the applicability of the method itself in determining the elastic modulus of a ductile material.
I. INTRODUCTION
The finite element method has been used increasingly over the past decade to perform a quantitative study of the normal indentation of an elastic-plastic solid by a rigid indenter.1–7 Despite the complexity of numerically simulating the nonlinear elastic-plastic deformation of a material, however, there have been few attempts, if any, to verify the simulation result against the corresponding observation in terms of the resulting plastic deformation of the indented material surface. This appears to have been largely because of the difficulty in accurately quantifying the minute plastic deformation of the material surface that results from the depth-sensing nanoindentation technique. In this background, a large-scale depthsensing indentation system with a spherical tip was used to deform the surface of a Ti–6Al–4V alloy block in the elasto-plastic regime. A detailed comparison was made between the observation and numerical simulation of the spherical indenter impression profile. The philosophy of
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0447 3474
http://journals.cambridge.org
J. Mater. Res., Vol. 19, No. 12, Dec 2004 Downloaded: 11 Nov 2014
performing large-scale depth-sensing indentation experiments to examine the contact mechanics by direct observation, pursued in this study, is similar to that by Thurn et al., who made direct optical measurements of the contacts during and after indentation for a pointed indenter.8,9
II. MATERIALS AND METHODS A. Indentation apparatus at macroscopic dimensions
A 10-mm-thick Ti–6Al–4V alloy plate with a surface roughness average (Ra) of 0.2 m was indente
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