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Viscoelastic effects during unloading in depth-sensing indentation

Published online by Cambridge University Press:  31 January 2011

A. H. W. Ngan
Affiliation:
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China
B. Tang
Affiliation:
Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China
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Abstract

With polypropylene as a prototype viscoelastic material at room temperature, it was found that a “nose” may appear in the unloading segment of the load–displacement curve during nanoindentation when the holding time at peak load is short and/or the unloading rate is small, and when the peak load is high enough. The load at which the nose appears was also found to decrease linearly with decreasing unloading rate. A linear viscoelasticity analysis was performed to interpret this effect. The analysis predicts a linear variation between the nose load and the unloading rate, and the slope of such a linear variation is also shown to be proportional to the viscosity parameter of the material. Thus, by measuring the slope of the nose-load versus unloading rate plot at a given temperature, the viscosity parameter of the specimen can be found. This is a new way of measuring the viscosity parameter of a material in addition to the existing method of force modulation and noting the frequency response of the displacement.

Type
Articles
Copyright
Copyright © Materials Research Society 2002

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References

REFERENCES

1.Oliver, W.C. and Pharr, G.M., J. Mater. Res. 7, 1564 (1992).CrossRefGoogle Scholar
2.Feng, G. and Ngan, A.H.W., J. Mater. Res. 17, 660 (2002).CrossRefGoogle Scholar
3.Feng, G. and Ngan, A.H.W., in Fundamentals of Nanoindentation and Nanotribology II, edited by Baker, S.P., Cook, R.F., Corcoran, S.G., and Moody, N.R. (Mater. Res. Soc. Symp. Proc. 649, Warrendale, PA, 2001), p. Q7.1.Google Scholar
4.Radok, J.R.M., Q. Appl. Math. 15, 198 (1957).CrossRefGoogle Scholar
5.Lee, E.H. and Radok, J.R.M., J. App. Mech. 27, 438 (1960).CrossRefGoogle Scholar
6.Ting, T.C.T., J. App. Mech. 33, 845 (1966).CrossRefGoogle Scholar
7.Ashby, M.F. and Jones, D.R.H., Engineering Materials, (Pergamon Press, Oxford, U.K., 1986), p. 31.Google Scholar
8.Loubet, J.L., Oliver, W.C., and Lucas, B.N., J. Mater. Res. 15, 1195 (2000).CrossRefGoogle Scholar
9.Ferry, J.D., Viscoelastic Properties of Polymers (John Wiley & Sons, New York, 1970), p. 45.Google Scholar