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The effects of transverse vibrations upon a double-cantilever crack are studied.

There has been much theoretical controversy concerning acquisition of a response under partial, as opposed to continuous reinforcement. Results are in direct conflict with current learning theories. It was the purpose of the present study to test the hypothesis by Dr. Solomon Weinstock. A wide alleyway should provide the opportunity for more non-functional responses to occur and get built into the chain of responses learned by the animal than would a narrow alleyway. While the present study was designed to test the hypothesis about acquisition, extinction trials were also run.

Investigated is the anti-plane stress distribution around a semi-infinite crack traveling with constant velocity in an infinitely long strip of finite width. The problem is reduced to the solution of the Hilbert problem of the half plane by the application of the Schwarz-Christoffel conformal transformation and the theory of complex functions.

The interaction of a large amplitude progressing wave with a piecewise linear shear flow is described.

Three possible mechanisms for non-propagating cracks were proposed with one being at least partially eliminated when a test run in dry argon on Ti-6Al-4V produced little or no change in the threshold compared to that in air. WOL type compact tension specimens of 9310 steel, 4340 steel, and Ti-6Al-4V were cyclically loaded at frequencies up to 200 cps for long periods of time to obtain extremely slow crack propagaion data down to 5 x 10-9 inches per cycle.

The order of the stress singularity at its vertex of a wedge of two bonded elastic media under longitudinal shear is solved by use of the Williams method. The similar problem of an elastic wedge bonded to a rigid foundation is also solved using the same method. Next, the problem of a cylindrical elastic media whose boundary is a polygon bonded to a rigid foundation and subjected to various types of longitudinal shear loads on its boundary is considered. A number of examples are worked out and expressions for contact stresses along the bonds are given.