Nondestructive determination of cohesive strength of adhesive-bonded composites

Systematic plan determines vibration responses and modes of honeycomb composites, correlates vibrational responses of composite specimens varying in strength of cohesive bond, determines effects of thickness variation of the face sheet over the frequency range, optimizes the characteristics of the excitation transducer, and measures bond strength

Active controls for ride smoothing

Active controls technology offers great promise for significantly smoothing the ride, and thus improving public and air carrier acceptance, of certain types of transport aircraft. Recent findings which support this promise are presented in the following three pertinent areas: (1) Ride quality versus degree of traveler satisfaction; (2) significant findings from a feasibility study of a ride smoothing system; and (3) potential ride problems identified for several advanced transport concepts

The use of LANDSAT digital data to detect and monitor vegetation water deficiencies

A technique devised using a vector transformation of LANDSAT digital data to indicate when vegetation is undergoing moisture stress is described. A relation established between the remote sensing-based criterion (the Green Index Number) and a ground-based criterion (Crop Moisture Index) is discussed

Introductory Comments

I\u27d like to take a few minutes at the outset of this meeting to welcome you to the sixth annual review of research Progress in Quantitative NDE and to provide you with some perspective for the program that you will hear and participate in this week. As you know, the review is centered upon research work sponsored by the Defense Advanced Research Projects Agency and the Air Force (Drs. Michael Buckley and Joseph Moyzis, Program managers). In order to further promote technical interchange, however, we have included related research efforts in this meeting that are sponsored by agencies other than DARPA and the Air Force. I\u27ll focus my remaining remarks on three topics - the DARPA/AF goals, our approach for the attainment of those goals, and some accomplishments to date. I hope that these comments will provide you with a perspective of the week\u27s program

Purpose and Progress of Quantitative NDE

In this paper the purposes and benefits of quantitative NDE are first discussed, emphasizing the bridging that is required to couple the measurements to fracture mechanics to produce an integrated, failure predictive discipline. This discussion is followed by a summary of highlights of the ARPA/AFML program aimed at the attainment of these goals. As a particular example of this approach the building blocks that have been developed and which now form the skeletal structure of a quantitative ultrasonics technology are reviewed and placed in perspective. The technical building blocks composing this structure have not only contributed to the desired long-term project objectives, but have also led to spin-off solutions with immediate applicability to current problems

Highly-improved lattice field-strength tensor

We derive an O(a^4)-improved lattice version of the continuum field-strength tensor. Discretization errors are reduced via the combination of several clover terms of various sizes, complemented by tadpole improvement. The resulting improved field-strength tensor is used to construct O(a^4)-improved topological charge and action operators. We compare the values attained by these operators as we cool several configurations to self-duality with a previously defined highly-improved action and assess the relative scale of the remaining discretization errors.Comment: 22 pages, 7 postscript figure

On the interaction of ultrasound with cracks: Applications to fatigue crack growth

Partial contact of two rough fatigue crack surfaces leads to transmission and diffraction of an acoustic signal at those contacts. Recent experimental and theoretical efforts to understand and quantify such contact in greater detail are discussed. The objective is to develop an understanding of the closure phenomenon and its application to the interpretation of fatigue data, in particular the R-ratio, spike overload/underload and threshold effects on crack propagation