Vibro-impact attachments as shock absorbers

The use of vibro-impact (VI) attachments as shock absorbers is studied. By considering different configurations of primary linear oscillators with VI attachments, the capacity of these attachments to passively absorb and dissipate significant portions of shock energy applied to the primary systems is investigated. Parametric studies are performed to determine the dependence of energy dissipation by theVI attachment in terms of its parameters.Moreover, non-linear shock spectra are used to demonstrate that appropriately designed VI attachments can significantly reduce the maximum levels of vibration of primary systems over wide frequency ranges. This is in contrast to the classical linear vibration absorber, whose action is narrowband. In addition, it is shown that VI attachments can significantly reduce or even completely eliminate resonances appearing in the linear shock spectra, thus providing strong, robust, and broadband shock protection to the primary structures to which they are attached

Semi-global analysis of periodic and quasi-periodic k:1 and k:2 resonances

The present paper investigates a family of nonlinear oscillators at Hopf bifurcation, driven by a small quasi-periodic forcing. In particular, we are interested in the situation that at bifurcation and for vanishing forcing strength, the driving frequency and the normal frequency are in k:1 or k:2 resonance. For small but nonvanishing forcing strength, a semi-global normal form system is found by averaging and applying a van der Pol transformation. The bifurcation diagram is organised by a codimension 3 singularity of nilpotent-elliptic type. A fairly complete analysis of local bifurcations is given; moreover, all the nonlocal bifurcation curves predicted by Dumortier et al. (1991) are found numerically.

Banjo Drum Physics - theoretical preliminaries

The interaction of a drum's head with its enclosed air is presented in the simplest possible form appropriate to the questions and issues that arise in understanding the timbre of the banjo. The inherent air-head impedance mismatch allows treating the head as driver of the air and the air's effect, in turn, as back reaction. Any particular question can then be addressed with a calculation in simple wave mechanics. The analysis confirms and quantifies the notion that internal air resonances enhance the response of the head at its and their frequencies. However, the details of just how are fairly complicated.Comment: 31 pages, 13 numbered figures + 2 on page

Nonlinear Micromechanical Casimir Oscillator

The Casimir force between uncharged metallic surfaces originates from quantum mechanical zero point fluctuations of the electromagnetic field. We demonstrate that this quantum electrodynamical effect has a profound influence on the oscillatory behavior of microstructures when surfaces are in close proximity (<= 100 nm). Frequency shifts, hysteretic behavior and bistability caused by the Casimir force are observed in the frequency response of a periodically driven micromachined torsional oscillator.Comment: 4 pages, 4 figures; added and rearranged references; added comments on sensitivit

NASA Thesaurus Supplement: A three part cumulative supplement to the 1982 edition of the NASA Thesaurus (supplement 2)

The three part cumulative NASA Thesaurus Supplement to the 1982 edition of the NASA Thesaurus includes: part 1, hierarchical listing; part 2, access vocabulary, and part 3, deletions. The semiannual supplement gives complete hierarchies for new terms and includes new term indications for terms new to this supplement