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Metastable effects onmartensitic transformation in SMA

Part 4. Thermomechanical properties of CuAlBe and NiTi observations for dampers in family houses

Journal of Thermal Analysis and Calorimetry
Authors: C. Auguet, A. Isalgué, F. Lovey, F. Martorell, and V. Torra

Abstract  

The behavior of shape memory alloys (SMA) allows their use as a passive smart material. In particular, the existence of a hysteretic cycle in the domain of the elementary coordinates strain-stress-temperature (σ, ε, T) suggests its application for damping in mechanical and/or in civil engineering. We are working in the application of SMA as dampers for earthquakes in small houses as family homes. For dampers installed in the inner porticos of the house, the suggested SMA is the CuAlBe and, eventually, the NiTi. At room temperature the used SMA wires induces forces situated between 2–3kN/wire. The properties related with the damping applications for CuAlBe and NiTi, i.e., the SMA creep and the self-heating will be presented, together with some other minor stress and temperature effects on NiTi modifying the hysteretic behavior.

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Abstract  

The miniaturized calorimetric devices furnish a reduced working flat surface and permits measurements with extremely low-mass quantities. The experimental sensitivity shows relevant position dependence with x-y surface coordinates and with z-distance. The device identification is realized via a 2-D model based in Fourier general equation. Using the Marquardt method the experimental flat surface device can be identified and the fitted parameters used to simulate the behavior of the experimental system. From the model, the effects of several dissipation configurations can be evaluated. Also, via the RC-analogy, a way to 3-D experimental devices is roughly described.

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Identification of micro-scale calorimetric devices

Part V. Basic properties for gas–solid reactions

Journal of Thermal Analysis and Calorimetry
Authors: C. Auguet, J. Seguin, F. Martorell, F. Moll, V. Torra, and J. Lerchner

Abstract  

Micro-calorimetric devices using Si-based sensors are very useful for the study of gas–solid reactions, in which very low mass of reactants are necessary. But in fact the consequence of using flat detectors is an increase of the uncertainty in the measured energy. In this work a calorimetric gas sensor based on Xensor chip is analysed studying the local x–y contributions of dissipation to the sensitivity related to the value in the centre. We study also the effects of the gas-flow on the sensitivity, comparing the results obtained with two Xensor type chips. Finally we carry out a deeper analysis of the x–y effects on the calorimetric detector for dissipations in the reactant shell extremely close to the detector surface to visualize the link between the power density distribution and the output signal.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Auguet, J. Lerchner, P. Marinelli, F. Martorell, M. Rodriguez de Rivera, V. Torra, and G. Wolf

Abstract  

The experimental analysis of conventional conduction calorimeters shows excellent reproducibility and relevant systematic errors in comparison with thermodynamic values established via adiabatic calorimeters. Two examples: a DSC and a liquid flow device are schematically analyzed. When an increased accuracy will be obtained the positional effects on the experimental set-up and on the measurement process need to be modelled. From experimental measurements realized on the Xensor liquid nano-calorimeter representative models can be built. To evaluate the reliability of measurement routines, established from experimental basis, several different dissipation structures inside the working space can be simulated. Two experimental configurations related to drop to drop reaction and to continuous mixing are modelled via RC approach. The RC formalism is extended to evaluate the carried energy effect produced by the continuous inflow/outflow of reactants in the mixing enthalpy chamber.

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