Papers by Antonio Isalgue
ESOMAT 2009 - 8th European Symposium on Martensitic Transformations, 2009
There have been published many papers and several reviews on the application of SMA's as damping ... more There have been published many papers and several reviews on the application of SMA's as damping devices in civil engineering by using the pseudo-elastic effect, but they are difficult to apply because the behaviour of the alloys is not carefully analyzed. In particular, the summer-winter temperature effects, aging long time at low temperature, self-heating or residual strains requirements for the given applications are rarely well established. In this work, we analyze and compare two cases, the damping of earthquake effects on relatively small structures as family homes, and the damping of stayed cables in large bridges. The requirements for the materials are different, and in each case a different commercial alloy with appropriate conditioning might provide acceptable answers. To confirm the usefulness of the dampers, the hysteretic behaviour of two SMAs (CuAlBe and NiTi) has been analyzed, and later modelled and introduced in finite element codes for the simulation of structures. The behaviour of the structures without and with dampers have been analyzed and compared. Also, some realistic experiments with cable 1 in the ELSA Joint Research Centre of the EU in Ispra have been done with NiTi wire of 2.46 mm diameter as damper, to compare with simulations.
γ precipitates in Cu based SMA: Interface effects and training processes
Ecomaterials, 1994
The presence of precipitates in SMA influences strongly their properties. We present some experim... more The presence of precipitates in SMA influences strongly their properties. We present some experimental results for small γ phase precipitates (around 10 nm) in Cu-Zn-Al single crystals. The shift in transformation temperatures and the evolutive behaviour of the stress/temperature width on cycling are interpreted as due to the creation of dislocations and to the subsequent plastic deformation of martensite around the precipitates as a consequence of the β-martensite interface passing through the material. With the appropriated thermomechanical treatment, the precipitate growth could be oriented to give a symmetry breakdown of the system and, as a result, a two way shape memory effect could be obtained.
IEEE Transactions on Magnetics, 1984
~_ _ I With the aim of a better understanding of both cationic distributi,on and magnetic propert... more ~_ _ I With the aim of a better understanding of both cationic distributi,on and magnetic properties of the uniaxial SrFe12-xCrxOlg hexagonal ferrites, Mossbauer spectroscopy, neutron diffraction and high field magnetization measurements have been carried out. The Cr3+ ions 'occupy the octahedral sites of the M structure with a preference hierarchy within them. The magnetic measurements, together with the deduced cationic distribution, indicate that some sublattices have a random spin canting around the c-axis.
Microstructure and Thermodynamics of the Martensitic Transformation
Canadian Metallurgical Quarterly, 2000
ABSTRACT
Interaction of Martensitic Transformation with Dislocations in Shape Memory Alloys
On Scaling Laws and Maritime Transport
Journal of maritime research, 2008
Scaling, as a manifestation of the underlying general dynamics and geometry, is familiar througho... more Scaling, as a manifestation of the underlying general dynamics and geometry, is familiar throughout physics. It has helped scientists gain deeper insights into problems ranging across the entire spectrum of science and technology, as scaling laws typically reflect generic features and physical principles that are independent of the detailed dynamics or specific characteristics of particular models. Fluid mechanics and phase transitions are significant examples of physics in which scaling has illuminated important universal principles or structures, and has provided responses to practical problems. Also, complex systems as living organisms obey some scaling relations that capture these systems’ essential features, if these do in fact exist. In contrast to the large diversity and complexity of living organisms, one finds the simplicity of the scaling behaviour of biological processes that holds true in a wide range of phenomena and a large range of energy and mass.The constructal theo...
Electrical, thermal and magnetic behaviour of the metallic glass Fe 80 B 20 in the crystallization process
Anales de Fisica. Serie B, Aplicaciones, Metodos e Instrumentos, 1986
Journal of Materials Engineering and Performance, 2015
Shape memory alloys are considered smart materials because of their singular thermo-mechanical pr... more Shape memory alloys are considered smart materials because of their singular thermo-mechanical properties, due to a thermoelastic martensitic transformation, enabling possible uses as actuators (because of mechanical recovery induced from temperature changes) and as dampers (because of hysteresis). NiTi wires for dampers in Civil Engineering had been characterized and tested in facilities. Guaranteed performance needs to know behavior during fatigue life and knowledge of effects in the event of extreme conditions, as eventual overstraining. In this work, we check the possibilities to absorb mechanical energy on the fatigue life depending on stress level and explore the consequences of overstraining the material
From experimental data to quake damping by SMA: a critical experimental analysis and simulation
Pseudoelastic fatigue of NiTi wires: frequency and size effects on damping capacity
Smart Materials and Structures, 2010
ABSTRACT The damping properties associated with hysteretic behavior of the pseudoelastic stress–s... more ABSTRACT The damping properties associated with hysteretic behavior of the pseudoelastic stress–strain (σ–ε) curves of NiTi shape memory alloy (SMA) wires were studied. Damping was characterized for wires of 2.46 and 0.5 mm diameter using samples of 120 mm in length. The effect of the frequency and size of the wire on the σ–ε curves were studied in the 3 × 10 − 5–3 Hz range, with 8% maximal strain. Damping associated parameters, such as hysteresis width, dissipated energy and specific damping capacity (SDC), defined as the ratio between the hysteretic energy and the maximum strain work over a complete pseudoelastic cycle, show maximum values at a specific frequency for each size diameter. These findings were explained in terms of the temperature effects associated to the heat of transformation. Results show that NiTi wire of 0.5 mm diameter has the highest SDC when cycling around 0.1 Hz while wire of 2.46 mm diameter has the highest SDC at 0.01 Hz. At 1 Hz, the SDC for 0.5 mm diameter wire is around twice that of 2.46 mm diameter wire.
Damping in Civil Engineering Using SMA. The Fatigue Behavior and Stability of CuAlBe and NiTi Alloys
Journal of Materials Engineering and Performance, 2009
Two types of application in damping of structures by SMA in Civil Engineering are considered. The... more Two types of application in damping of structures by SMA in Civil Engineering are considered. The first one is related to the reduction of the damage produced by earthquakes. The second one is concerned with the increase of the lifetime of the stayed cables in bridges. The analyses of the experimental conditions required for each application are different: Several years
Earthquakes Effects: Reduction of Plastic Deformation in Structures by Sma
ABSTRACT
After quench effects in beta-phase CuZnAl SMA
ABSTRACT Critical applications of SMA need a guaranteed behaviour. In SMA metallurgy, it is usual... more ABSTRACT Critical applications of SMA need a guaranteed behaviour. In SMA metallurgy, it is usual to quench the alloys after some homogeneization and betatization thermal treatments. The quenched alloys are in metastable state, and thus some time evolution is expected. It is well established that when transforming to the martensite phase, the martensite can experience a stabilization, which, in some Cu based alloys may be up to 100K if the transformation is done immediately after the quench. Appart from the classical stabilization of martensite, time evolutions can be detected in beta phase after the quench. A correct description and a methodology on the detection and evaluation of these effects is needed in order to obtain high reliability of SMA devices. These evolutions affect the macroscopic parameters during at least hundreds of hours, and affect also the martensitic transformation temperatures. This work is aimed to describe the time evolution behaviour in terms of macroscopic parameters as electrical resistance, density, and calorimetric signal (energy dissipation), observed after the quench in CuZnAl alloys. These parameters can be considered as representative of the internal state of the sample, and can be connected to the Ms behaviour for long time evolutions in beta phase near room temperature. The observed dependences on the sample characteristics are also discussed.
Meso-scale model of a Cu-Zn-Al single crystal SMA
SMA Dampers for Cable Vibration: An Available Solution for Oscillation Mitigation of Stayed Cables in Bridges
Advances in Science and Technology, 2012
Several solutions have been proposed to mitigate the vibrations of stay cables in bridges, which ... more Several solutions have been proposed to mitigate the vibrations of stay cables in bridges, which are subjected to wind, rain and traffic loads. One possible solution relates to the use of semi-active devices, such as the ones based on magneto-rheologic fluids. These devices need guaranteed electrical power, together with computational effort and technical attention. In contrast, shape memory alloy (SMA) wires were studied for application as passive elements. In the present work, the properties of SMA that are required to realize dampers provided with an appropriate reliability are discussed. In particular, the fatigue/fracture life of the SMA wires and the thermal effects induced by both external temperature and the self-heating process are studied. The SMA dampers were applied to stayed cables of realistic size and tested in "facilities." Namely, the cables No 1 of 45 m length available at the ELSA-JRC in Ispra, Italy, and the 50 m cable of IFSTTAR near Nantes, in France,...
Journal of Thermal Analysis and Calorimetry, 2015
The SMA was studied for their macroscopic application in damping for Civil Engineering. The study... more The SMA was studied for their macroscopic application in damping for Civil Engineering. The study is a synthesis and includes an outline of the models required for the SMA simulation and some case studies using the Finite Element Analysis methods. This work is an overview that focuses in the mitigation of the oscillations in structures induced by earthquakes, and for a reduction of the oscillations amplitude in stayed cables under the action of rain, wind or traffic. The analysis needs the required conditions for each application determining the working conditions. The study includes the number of working cycles, the temperature effects and the cooling actions and, for instance, the action of the cycling frequency. The main target relates the appropriateness of the SMA for each purpose, and the suitability of the SMA device is always experimentally guaranteed. Furthermore, the applicability of the obtained results for SMA and the practical behavior of the SMA dampers were studied in international facilities. The paper includes appropriate suggestions for a correct preparation of the SMA dampers. This work outlines the effects of stress and temperature aging in NiTi, describes the particular structural effects between 18R and 6R, introduces a first attempt in the dynamic properties of the CuAlBe single crystals and summarizes some recent suggestions for damping using SMA.
Matériaux intelligents : modélisation prédictive de l’évolution temporelle d’alliages à mémoire de forme du type Cu-Zn-Al
Journal de Chimie Physique, 1997
Les proprietes «intelligentes» de certains materiaux (magnetostriction, piezoelectricite, memoire... more Les proprietes «intelligentes» de certains materiaux (magnetostriction, piezoelectricite, memoire de forme) concernent leur capacite a reagir directement a une modification de leur environnement. L'application pratique des alliages a memoire de forme necessite des outils de caracterisation permettant une evaluation quantitative des performances en vue de garantir l'utilisation de ces materiaux. Une etude. de haute resolution, de leur comportement temporel permet une modelisation predictive de celui-ci et l'etablissement eventuel de routines industrielles de controle. Lorsque le materiau se trouve en phase-mere, un changement de la temperature ambiante produit, sur la temperature de transformation, un changement egal a 11 % de celui qui affecte la temperature ambiante.
The use of the hysteresis cycle in SMA as a damper for scarce events as quakes via elements insid... more The use of the hysteresis cycle in SMA as a damper for scarce events as quakes via elements inside the structure seems an interesting approach in Civil Engineering. The dampers will not require maintenance when the physical guarantee of the SMA ensures an appropriate long working life (more than 20 years). The phenomena that produce the evolution of the material is analyzed and the effects of a proper heat treatment are presented. The concept of pseudoelastic window is applied to the Cu-Al-Be alloy to show the possibility of long working time. A sample simulation is presented to show the possibilities of the proposed method.
Shape memory NiTi films deposited at low temperature
See aricle in "Materials Science & Engineering A273-275 (1999) 717-721"
ESOMAT 2009 - 8th European Symposium on Martensitic Transformations, 2009
Effects of aging at intermediate temperatures (near 4 precipitation, which affects the transforma... more Effects of aging at intermediate temperatures (near 4 precipitation, which affects the transformation behaviour. In this work, we observe some dependences (recoverable or not) of transformation temperature with aging at temperatures near or under in beta phase. Two copper-based SMA alloys have been analyzed, CuZnAl and CuAlBe. Also, some analysis has been done on pseudo-elastic NiTi. By aging at temperatures near the two copper alloys show changes in transformation temperatures, which can be related univocally to the changes in the temperature at which the alloy is kept. In both alloys, by staying long time at a given temperature, an asymptotic value of the transformation temperature is reached, and further coming to the same temperature produces the transformation temperature to evolve to that asymptotic value. The maximal amplitude of the changes is about 16% of the amplitude of the change in aging temperature. The changes are much faster in CuZnAl than in CuAlBe, and the sign of the changes is opposite in CuAlBe respect to that in CuZnAl. The process can be well modelled by a system of differential equations with one or two terms, giving a "tracking" of the transformation temperature respect the temperature at which the alloy is kept. The activation energies for the time evolution suggest atomic-order related processes as cause for the transformation temperature changes. For NiTi, the evolution is much slower, and seems to be monotonic with time, suggesting a precipitation-related mechanism as the origin of the transformation temperature changes, even at temperatures near From the data, some conclusions may be drawn concerning long-time effects on the applications of the alloys
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Papers by Antonio Isalgue