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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.

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In this paper, three-dimensional finite element analysis using the commercial ANSYS software is performed to study the thermal performance of a thermally enhanced FC-PBGA (flip-chip plastic ball grid array) assembly in both natural and forced convection environments. The thermally enhanced FC-PBGA assembly is a basic FC-PBGA assembly with a lid attached on top, after which an extruded-fin heatsink is attached on the top of the lid. The finite element model is complete enough to include key elements such as bumps, solder balls, substrate, printed circuit board, extruded-fin heatsink, lid, vias, TIM1 (thermal interface material 1), TIM2 (thermal interface material 2), lid-substrate adhesive and ground planes for both signal and power. Temperature fields are simulated and presented for several package configurations. Thermal resistance is calculated to characterize and compare the thermal performance by considering alternative design parameters of the polymer-based materials and the thermal enhancement components. The polymer-based materials include underfill, TIM1, TIM2, lid-substrate adhesive and substrate core material. The specific thermal enhancement components are the extruded-fin heatsink and the lid.

The phenomenon of hole pressure occurs whenever a polymeric or viscoelastic liquid flows over a depression in a conduit wall. Numerical simulations undertaken for the flow of an aqueous polyacrylamide melt passing over a transverse slot arc considered here. The fluid model used for this study is a White-Metzner constitutive equation describing the non-Newtonian behavior of the melt. The results were computed by an elastic-viscous split-stress finite clement method (EVSS-FEM). a mixed finite clement method incorporating the non-consistent streamline upwind scheme. For verification, the numerical algorithm was first applied to compute the corresponding flow of the upper-convected Maxwell fluid model, a special case of the Whitc-Metzner model characterized by constant viscosity and relation time. The resulting hole pressure (Ph) was evaluated for various Deborah numbers (De) and compared with the analytical prediction derived from the Higashitani-Pritchard (HP) theory. The agreement was found to be satisfactory for creeping flow in the low De range, for which the HP theory is valid. Subsequently, the hole pressure of this flow problem was predicted. The streamlines and pressure distribution along the channel walls arc also presented. Furthermore, the effects of fluid elasticity, shear thinning, the exponent in the viscosity function and the relaxation-time function, and slot geometry on the hole pressure were investigated.

Flip-chip packaging provides a high-performance low-cost approach for the development of electronic packages. A three-dimensional viscoelastic-plastic finite element analysis using the commercial software ANSYS has been performed to study the thermomechanical behavior in flip-chip assemblies, i.e., the four components, chip, solder ball, underfill, and substrate. The viscoelastic behavior of the underfill is modeled on the Maxwell constitutive equation while the viscoplastic behavior of the solder balls is modeled by the Anand model. Both the chip and the substrate are assumed to be elastic materials modeled by the Hooke's law. As in standard industry practice, temperature cycling from 125 to 55°C is used. Simulated thermomechanical behavior is presented for the solder balls. Subsequently, the effects of underfill-material properties, such as elasticity and coefficient of thermal expansion are also investigated.

The 3D non-isothermal creeping flow of nylon-6 in a bent rectangular duct is studied numerically. A differential-type non-isothermal White-Metzner constitutive equation is used for this flow simulation. Computational results are obtained by the elastic-viscous split-stress (EVSS) finite element method, incorporating the streamline-upwind Petrov-Galerkin (SUPG) scheme. The generated thermal field is entirely due to viscous heating. Essential flow characteristics, including temperature distribution in the flow field, are predicted. The resulting average Nusselt numbers along the walls and dimensionless bulk temperatures along the channel are obtained. Subsequently, the effects of flow-rate and geometry are investigated.

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