Adhesion in spherical contacts and in electrostatic actuation of a carbon nanotube

The Hertz contact theory can predict the onset of yielding for those contacts in which adhesive effect is negligible. However in microscale contacts, yielding will occur for lower loads than predicted by the Hertz theory. The present study provides yield conditions for the JKR, DMT, and Greenwood-Johnson theories of adhesion. Attention is first focused on the initiation of yield along the symmetrical axis of the contact. The results show the critical loads for the three adhesion theories are close together but different significantly from that predicted by Hertz. Results are also obtained for the onset of yielding away from the symmetrical axis using the Greenwood-Johnson theory of adhesion.;The carbon nanotube is a popular component in nanotechnology. This study focuses on one kind of structure in NEMS, i.e. a nanoswitch which consists of a doubly clamped carbon nanotube and an electrode plane. When a voltage difference is applied between them, an electrostatic distributed force is produced to bend the nanotube down toward the electrode plane. This study also discusses the effect of two slip zones around both the ends which releases a portion of the tensile force inside the nanotube. The numerical results compare three models of doubly clamped nanotubes - a nanotube without stretching, a nanotube with stretching but no slip zones, and a nanotube with stretching and slip zones, to a doubly pinned nanotube and a nanowire.