Index of content:
Volume 118, Issue 6, December 2005
- STRUCTURAL ACOUSTICS AND VIBRATION 
Coupled flexural-longitudinal wave motion in a finite periodic structure with asymmetrically arranged transverse beams118(2005); http://dx.doi.org/10.1121/1.2126928View Description Hide Description
A companion paper [J. Acoust. Soc. Am.118, 3010–30202005] has examined the phenomena of flexural-longitudinal wave coupling in a practically undamped and semi-infinite periodic waveguide with structural side-branches. The effect of structural damping on wave coupling in such a waveguide is examined in the first part of the present paper, and the damping-dependent decrease in wave coupling is revealed for a structure with multiresonant side-branches. In the second part, the simplifying semi-infinite assumption is relaxed and general expressions for the junction responses of finite and multicoupled periodic systems are derived as a generalization of the governing expressions for finite, mono-coupled periodic systems [Ohlrich, J. Sound Vib.107, 411–434 (1986)]. The present derivation of the general frequency response of a finite system utilizes the eigenvectors of displacement responses and wave forces that are associated with the characteristic wave-types, which can exist in a multicoupled periodic system [Mead, J. Sound Vib.40, 19–39 (1975)]. The third part of the paper considers a finite specific test-structure with eight periodic elements and with structural terminations at the extreme ends. Audio-frequency vibration responses of this tri-coupled periodic structure are predicted numerically over a broad range of frequencies and a very good agreement is found with the measurement results obtained from an experiment with a nominally identical, periodic test-structure which is freely suspended.
118(2005); http://dx.doi.org/10.1121/1.2108754View Description Hide Description
Buried landmines exhibit complex structural vibrations, which are dependent on interaction between soil and mines as well as on their respective properties. This paper presents experimental and theoretical studies of multimodal vibrations of buried mines and discusses the effects of burial depth and soilproperties on dynamics of the soil-mine system. The two-dimensional model of the soil-mine system that accounts for soil-coupled mine’s multiple vibration modes and spatial distribution of vibrations over the soilsurface is introduced. The model was tested using experiments with the plastic mine simulant. The study reveals that the soil shear stiffness is one of the key governing parameters determining the resonance vibration frequency and the amplitude of the soil-mine system. Burial depth, soil moisture, and consolidation are among factors leading to the increase of the soil shear stiffness, therefore effectively influencing modal vibrations of buried mines.