Indentation fracture with a cube-corner diamond pyramid on soda-lime silicate glass and fused silica is investigated during the entire indentation cycle in both silicone oil and ambient-air environments. Radial cracks form immediately on loading in all cases. The two-component, elastic-contact ؉ elastic-plastic mismatch (residual) stress field model that has been used successfully to describe radial crack evolution at Vickers indentations fails to describe the fracture response with the cube-corner. The amplitudes of both elastic-contact and residual stress-intensity factors as deduced from these cube-corner experiments are up to a factor of 10 greater than have been previously observed.
Electrical power for distributed, wireless sensors may be harvested from vibrations in the
ambient through the use of electromechanical transducers. To be most useful, the
electromechanical transducer should maximize the harvested power by matching its
resonant frequency to the strongest vibration amplitude in the source’s vibration
spectrum. This paper introduces a new frequency tunable mechanism wherein the
deformation of the piezoelectric elements is primarily in-plane extension, and
bending effects may be neglected. The extensional mode resonator (XMR) is formed
by suspending a seismic mass with two piezoelectric sheets. The mechanism is
made frequency tunable by an adjustable link that symmetrically pre-tensions
both piezoelectric sheets. A prototype XMR has been built and tested that has
demonstrated adjustable and repeatable resonant frequency variation from 80
to 235 Hz. The electrical power generated by the XMR is also insensitive to the
driving frequency, when the resonant frequency is matched to the driving frequency.
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