Although most analyses in tribology deal with the behavior of fluids in shear, many fluids, such as greases or printing inks, can develop significant forces when subjected to pure extension. These forces can impact performance, especially in the exit region of tribological interfaces. The resistance of a fluid to an imposed shear rate is a measure of the fluid’s shear viscosity (usually just referred to as its viscosity). The resistance of a fluid to an imposed extensional strain rate is a measure of the fluid’s extensional viscosity. In this paper, two techniques for the measurement of extensional forces are discussed. A subsequent companion paper will discuss interpretation of the force data in terms of extensional viscosity. Both techniques described have the advantage of a dimensionally small measurement element. The first technique involves the use of a vapor deposited surface pressure transducer. This transducer is a thin strip of ytterbium. The electrical resistance of ytterbium is pressure sensitive. Small changes in resistance can be related to extensional stress. The extensional viscometer apparatus consists of two counter-rotating cylinders. As the fluid exits the nip between the cylinders, the extensional stress is detected by a transducer attached to one of the cylinders. The second technique discussed herein involves the use of a small-beam transducer in conjunction with the counter-rotating cylinder apparatus. The deflection of the beam due to the fluid’s extensional force is detected and interpreted in terms of extensional stress as a function of strain rate at the exit of the nip. Extensional stresses of several hundred thousand Pa have been measured.

1.
Banks
W. H.
, and
Mill
C. C.
,
1953
, “
Tacky Adhesion—A Preliminary Study
,”
J. Colloid Sci.
, Vol.
8
, pp.
137
147
.
2.
Banks
W. H.
, and
Mill
C. C.
,
1954
, “
Some Observations on the Behavior of Liquids Between Rotating Rollers
,”
Proceedings R. Soc., London
, A, Vol.
223
, pp.
414
419
.
3.
Beck, D., 1983, “Fluid Pressure in a Press Nip,” TAPPI Proceedings 1983 Conference, pp. 475–487.
4.
Bell, J. C., and Kannel, J. W., 1967, “Aspects of Lubrication Affecting Life of Rolling Bearings,” American Soc. for Metals, Metals Engineering Qtrly, pp. 28–35, Feb.
5.
Dobbels
F.
, and
Mewis
J.
,
1978
, “
Analysis of Nip Flow Operations Involving a Viscoelastic Roller
,”
Chem. Eng. Sci.
, Vol.
33
, pp.
493
500
.
6.
Fuller
G.
et al.,
1987
,
Journal of Rheology
, Vol.
31
, pp.
235
249
.
7.
Green
J.
,
1941
, “
The Tackmeter, an Instrument for Analyzing and Measuring Tack: Application to Printing Inks
,”
Ind. Eng. Chem.
, Anal. Ed., Vol.
13
, pp.
632
639
.
8.
Hartnett
M. J.
, and
Kannel
J. W.
,
1981
, “
Contact Stresses Between Elastic Cylinders: A Comprehensive Theoretical and Experimental Approach
,”
Trans. ASME
, Vol.
103
, pp.
40
45
, Jan.
9.
Kannel
J. W.
,
1965
, “
Measurement of Pressures in Rolling Contact
,”
Proc. Inst. Mech. Engrs.
, Vol.
180
, Part 3B, pp.
135
142
.
10.
Kannel
J. W.
,
1974
, “
Comparison Between Predicted and Measured Axial Pressure Distribution Between Cylinders
,”
ASME, JOURNAL OF LUBRICATION TECHNOLOGY
, Vol.
96
, No.
3
, pp.
508
514
, July.
11.
Kannel
J. W.
,
Bell
J. C.
, and
Allen
C. M.
,
1965
, “
Methods for Determining Pressure Distributions in Lubricated Rolling Contact
,”
Trans. ASLE
, Vol.
8
, pp.
250
270
.
12.
Kannel
J. W.
and
Dow
T. A.
,
1974
, “
The Evolution of Surface Pressure and Temperature Measurement Techniques for Use in the Study of Lubrication in Metal Rolling
,”
ASME Journal of Lubrication Technology
, Vol.
96
, No.
4
, pp.
611
617
, Oct.
13.
Kannel, J. W., Walowit, J. A., Bell, J. C., Allen, C. M., 1967, “The Determination of Stresses in Rolling-Contact Elements,” ASME JOURNAL OF LUBRICATION TECHNOLOGY, pp. 453–465, Oct.
14.
Myers, R. R. and Knauss, C. J., 1977, “Roll Application of Adhesives,” Handbook of Adhesives, I. Skeist, Van Nostrand Reinhold Company, New York, NY, pp. 72–91.
15.
Pangalus
G.
et al.,
1987
, “
Rheological Properties of New Inks
,”
J. Rheology
, Vol.
29
, pp.
471
491
.
16.
Patel
N.
, and
Dealy
J. M.
, “
Measurement of Tensile Stress at the Exit of a Printing Nip
,”
J. of Non-Newtonian Fluid Mech.
, Vol.
22
, pp.
245
252
.
17.
Reed, R. R., 1937, “Roller Apparatus for Testing the Consistency Properties of Printing and Lithographic Inks,” U.S. Patent 2,101,322.
18.
Strasburger
H.
,
1958
, “
Tacky Adhesion
,”
J. Colloid Sci.
, Vol.
13
, pp.
218
231
.
19.
Sridhar
T.
et al.,
1991
, “
Measurement of Extensional Viscosity of Polymer Solutions
,”
J. of Non-Newtonian Fluid Mech.
, Vol.
40
, pp.
271
280
.
20.
Voet
A.
, and
Geffken
C. F.
, “
The Nature of Tack
,”
Ind. Eng. Chem.
, Vol.
43
, pp.
1614
1624
(
1951
).
21.
Zang
Y.
,
Aspler
J.
,
Boluk
M.
, and
DeGrace
J.
,
1991
, “
Direct Measurement of Tensile Stress (“Tack”) in Thin Ink Films
,”
J. Rheol.
, Vol.
35
(
3
), pp.
345
360
.
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