A prototype contact-type micro piezoresistive shear-stress sensor that can be utilized to measure the shear stress between skin of stump and socket of above-knee (AK) prosthesis was designed, fabricated and tested. Micro-electro-mechanical system (MEMS) technology has been chosen for the design because of the low cost, small size and adaptability to this application. In this paper, the finite element method (FEM) package ANSYS has been employed for the stress analysis of the micro shear-stress sensors. The sensors contain two transducers that will transform the stresses into an output voltage. In the developed sensor, a 3000 3000 300 m 3 square membrane is formed by bulk micromaching of an n-type 100 monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 10 15 atoms/cm 2 . Static characteristics of the shear sensor were determined through a series of calibration tests. The fabricated sensor exhibits a sensitivity of 0.13 mV/mA-MPa for a 1.4 N full scales shear force range and the overall mean hysteresis error is than 3.5%. In addition, the results simulated by FEM are validated by comparison with experimental investigations.
[607]Index Terms-Finite element method, micro-electro-mechanical system, piezoresistive, shear-stress sensor, transducer.
ABSTRACT--A new approach for digital determination of photoelastic birefringence is proposed. The relationships between the intensity values and the fringe orders of two wavelengths are derived. This scheme allows for automatic determination of fringe orders of a full-field photoelastic fringe pattern without using zero-order fringes in the fringe pattern. The usefulness of this method was demonstrated on two experimental fringe patterns with different wavelengths.
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