Adhesive Contact Between Elastic Bodies
When two solid surfaces are brought into close proximity, they experience attractive van der Waals forces. Bradley's van der Waals model provides a means of calculating the tensile force between two rigid spheres with perfectly smooth surfaces. The Hertzian model of contact does not consider adhesion possible. However, in the late 1960s, several contradictions were observed when the Hertz theory was compared with experiments involving contact between rubber and glass spheres.
It was observed that, though Hertz theory applied at large loads, at low loads
- the area of contact was larger than that predicted by Hertz theory,
- the area of contact had a non-zero value even when the load was removed, and
- there was strong adhesion if the contacting surfaces were clean and dry.
This indicated that adhesive forces were at work. The Johnson-Kendall-Roberts (JKR) model and the Derjaguin-Muller-Toporov (DMT) models were the first to incorporate adhesion into Hertzian contact.
Read more about this topic: Contact Mechanics
Famous quotes containing the words contact, elastic and/or bodies:
“Words, words, words! They shut one off from the universe. Three quarters of the time one’s never in contact with things, only with the beastly words that stand for them.”
—Aldous Huxley (1894–1963)
“To him whose elastic and vigorous thought keeps pace with the sun, the day is a perpetual morning. It matters not what the clocks say or the attitudes and labors of men. Morning is when I am awake and there is a dawn in me.”
—Henry David Thoreau (1817–1862)
“Their bodies are buried in peace; but their name liveth for evermore.”
—Apocrypha. Ecclesiasticus, 44:14.
The line “their name liveth for evermore” was chosen by Rudyard Kipling on behalf of the Imperial War Graves Commission as an epitaph to be used in Commonwealth War Cemeteries. Kipling had himself lost a son in the fighting.