Continuous and accurate monitoring of acceleration and temperature inside large turbo- and hydro-generators is of crucial importance to prevent extremely expensive system damages and false positives. Development of optical, metalfree sensors for such systems has gained a lot of attention due to the fact that they are resistant to typically very strong electromagnetic fields and that they are non-conductive. We present miniature temperature and accelerometer optical sensors using a common silicon MEMS platform. A linear response with a deviation as small as 1% between set and measured accelerations has been obtained in an acceleration range 0-40g. Preliminary tests for temperature sensors indicate a linear response with sensitivity better than 1°C in a range of 20°C to 150°C.
When a mechanical stress pulse, which is propagating in an elastic medium, encounters a material- or phase
interface, which generally represents a change of the acoustic impedance, it is split up into a part, which propagates
further into the new material and another part, which is reflected. The amplitude ratio of the reflected and
the transmitted part is governed by the normalized difference of the acoustic impedance only, provided that the
impedance change is a pure step function in space. If the acoustic impedance change is broadened spatially, the
ratio of the transmitted and reflected part becomes frequency dependent and the effect can therefore be used for
filter-, damping-, acoustic isolation-, and/or spectrum analysis purpose or for quantitative analysis of interface.
The effect is of growing importance for micro- and nanostructures since the relative size of the interface layers is
generally larger than in macroscopic structures.
In this work, a pulse propagating in a linear elastic graded material is described with analytical solutions
and one dimensional simulations. The numerical scheme is based on the Finite-Difference Time-Domain method
The validation of the numerical model occurs by comparing the simulated pulse propagation-history with an
analytical solution based on.1 On-coming research is also given at the end of this study.