The asperity contact regions in static contact are subjected to very high stress. Deformation is plastic and the material can suffer localized creep that is not usually observed at conventional stress levels. Creep of the asperity contacts causes an increase in contact area and hence an increase in the adhesive component of friction. The strains are so small compared with the bulk deflections that they are hard to measure by displacement of strain transducers. However, one measurement approach is to use the reflection of an ultrasonic pulse since this depends only on the interface behavior, specifically its stiffness. In this study, ultrasound was used to investigate the increase in interfacial stiffness with time. A power law relationship between stiffness and hold time was observed for both steel and aluminum surfaces pressed together. An analytical model that assumes a simple geometry for the contact has been developed. A single asperity was considered to determine the geometry of the whole interface by superposition. The stiffness predicted by the model was compared with experimental data and was used to determine the creep rate exponent for the material.

1.
Dowling
,
N. E.
, 1993,
Mechanical Behaviour of Materials
,
Prentice-Hall
,
Englewood-Cliffs, NJ
.
2.
Ashby
,
M. F.
, and
Jones
,
D. R. H.
, 2005,
Engineering Materials 1: An Introduction to Properties, Applications and Design
,
3rd ed.
,
Elsevier
,
Boston
.
3.
Nikitin
,
V. I.
, 1966, “
Effect of Adsorption of Liquid Metals Upon the Process of Creep in Compression
,”
Mater. Sci.
,
1
(
5
), pp.
422
423
. 1068-820X
4.
Bowden
,
F. P.
, and
Tabor
,
D.
, 1964,
The Friction and Lubrication of Solids Part II
(
The International Series of Monographs on Physics
),
1st ed.
,
Oxford University Press
,
London
.
5.
Fischer-Cripps
,
A. C.
, 2004, “
A Simple Phenomenological Approach to Nanoindentation Creep
,”
Mater. Sci. Eng., A
0921-5093,
385
(
1–2
), pp.
74
82
.
6.
Tweedie
,
C. A.
, and
Van Vliet
,
K. J.
, 2006, “
Contact Creep Compliance of Viscoelastic Materials Via Nanoindentation
,”
J. Mater. Res.
0884-2914,
21
(
6
), pp.
1576
1589
.
7.
Boyer
,
P. C.
,
Sainso
,
P.
,
Maitourman
,
M. H.
,
Houze
,
F.
,
Leclercq
,
M.
, and
Guery
,
J. P.
, 1995, “
Experimental and Theoretical Study of Creep Effects in Electrical Contacts
,”
Proceedings of the 41st IEEE Holm Conference on Electrical Contacts
, IEEE, Chicago, pp.
147
153
.
8.
Kendall
,
K.
, and
Tabor
,
D.
, 1971, “
An Ultrasonic Study of the Area of Contact Between Stationary and Sliding Surfaces
,”
Proc. R. Soc. London, Ser. A
1364-5021,
323
, pp.
321
340
.
9.
Bhushan
,
B.
, 1999,
Principles and Applications of Tribology
,
Wiley
,
New York
.
10.
Schoenberg
,
M.
, 1980, “
Elastic Wave Behaviour Across Linear Slip Interfaces
,”
J. Acoust. Soc. Am.
0001-4966,
68
(
5
), pp.
1516
1521
.
11.
Haines
,
N. F.
, 1980, “
The Theory of Sound Transmission and Reflection at Contacting Surfaces
,” CEGB Research Division, Berkeley Nuclear Laboratories, Report No. RD/B/N4744.
12.
Dwyer-Joyce
,
R. S.
,
Drinkwater
,
B. W.
, and
Quinn
,
A. M.
, 2001, “
The Use of Ultrasound in the Investigation of Rough Surface Interfaces
,”
Trans. ASME, J. Tribol.
0742-4787,
123
(
1
), pp.
8
16
.
13.
Baltazar
,
A.
,
Rokhlin
,
S. I.
, and
Pecorari
,
C.
, 2002, “
On the Relationship Between Ultrasonic and Micromechanical Properties of Contacting Rough Surfaces
,”
J. Mech. Phys. Solids
0022-5096,
50
(
7
), pp.
1397
1416
.
14.
Krolikowski
,
J.
, and
Szczepek
,
J.
, 1991, “
Prediction of Contact Parameters using Ultrasonic Method
,”
Wear
0043-1648,
148
(
1
), pp.
181
195
.
15.
Nagy
,
P. B.
, 1992, “
Ultrasonic Classification of Imperfect Interfaces
,”
J. Nondestruct. Eval.
0195-9298,
11
(
3–4
), pp.
127
139
.
16.
Thomas
,
T. R.
, and
Sayles
,
R. S.
, 1977, “
Stiffness of Machine Tool Joints: A Random-Process Approach
,”
ASME J. Eng. Ind.
0022-0817,
99
, pp.
250
256
.
17.
Drinkwater
,
B. W.
,
Dwyer-Joyce
,
R. S.
, and
Cawley
,
P.
, 1996, “
A Study of the Interaction between Ultrasound and a Partially Contacting Solid-Solid Interface
,”
Proc. R. Soc. London, Ser. A
0950-1207,
452
(
1955
), pp.
2613
2628
.
18.
Kim
,
J. -Y.
,
Baltazar
,
A.
, and
Rokhlin
,
S. I.
, 2004, “
Ultrasonic Assessment of Rough Surface Contact Between Solids From Elastoplastic Loading-Unloading Hysteresis Cycle
,”
J. Mech. Phys. Solids
0022-5096,
52
(
8
), pp.
1911
1934
.
19.
Greenwood
,
J. A.
, 1966, “
Constriction Resistance and the Real Area of Contact
,”
Br. J. Appl. Phys.
0508-3443,
17
(
12
), pp.
1621
1632
.
20.
Webster
,
M. N.
, and
Sayles
,
R. S.
, 1986, “
A Numerical Model for the Elastic Frictionless Contact of Real Rough Surfaces
,”
ASME J. Tribol.
0742-4787,
108
, pp.
314
320
.
21.
Williams
,
J. A.
, 1994,
Engineering Tribology
,
Oxford University Press
,
New York
.
22.
Thomas
,
T. R.
, 1982,
Rough Surfaces
,
Longman Group
.
23.
Greenwood
,
J. A.
, and
Williamson
,
J. B. P.
, 1966, “
Contact of Nominally Flat Surfaces
,”
Proc. R. Soc. London, Ser. A
0950-1207,
295
, pp.
300
319
.
24.
Cadek
,
J.
, 1988,
Creep in Mechanical Materials
,
Elsevier
,
Oxford
.
25.
Tabor
,
D.
, 1951,
The Hardness of Metals
,
Clarendon
,
Oxford
.
26.
Kaufman
,
J. G.
, 1999,
Properties of Aluminium Alloys: Tensile, Creep and Fatigue Data
,
The Aluminium Association
.
You do not currently have access to this content.