Biomedical Engineering Reference
In-Depth Information
CHAPTER 4
MECHANICS OF ADHESION
Robert F. Cook
Ceramics Division, National Institute of Standards and Technology
E-mail: robert.cook@nist.gov
A framework of increasing complexity is developed to describe the
mechanics of adhesion and its reverse, de-adhesion or separation,
during indentation contact cycles. The importance of the indentation
probe stiffness in determination of system stability is emphasized and
shown to control the details of the adhesive snap-on instability for a
simple logarithmic probe-surface interaction potential and the snap-on
and pull-off instabilities (and their existence) for a Mie interaction
potential. The work of adhesion is shown to depend critically on
the probe stiffness. Indentation contact-mechanics coordinates are
introduced and are used to develop the Johnson-Kendall-Roberts (JKR)
contact model. The similarities, differences, and conveniences of the
logarithmic, Mie, and JKR adhesive indentation contact models are
discussed.
1.
Adhesion: The “Snap-On” Instability
In this section the process of adhesion is considered: Two bodies,
initially in a state of separated, stable equilibrium, are brought together
by an external influence such that the system passes through a state of
unstable equilibrium to a new state in which the bodies are joined, or
adhered, to each other in a new stable equilibrium configuration.
A very simple system that gives rise to an adhesion process will be
considered: There is a long-range attraction only between the bodies and
one of the bodies is rigid (the surface from Chapter 2 ) and the other
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