arXiv subjects

Eduard Vives

Publications and source records attributed to Eduard Vives.

At least 19 recordsLinked to original sources

arXiv2021

Thermo-magnetic characterization of phase transitions in a Ni-Mn-In metamagnetic shape memory alloy

The partially overlapped ferroelastic/martensitic and para-ferromagnetic phase transitions of a Ni$_{50.53}$Mn${33.65}$In$_{15.82}$ metamagnetic shape memory alloy have been studied from calorimetric, magnetic and acoustic emission measurement. We have taken advantage of the existence of thermal hysteresis of the first order ferroelastic/martensitic phase transition ($\sim2.5$K) to discriminate the latent heat contribution $Δ$Ht = 7.21(15) kJ/kg and the specific heat contribution $Δ$Hc = 216(1) J/kg to the total excess enthalpy of the phase transition. The specific heat was found to follow a step-like behavior at this phase transition. The intermittent dynamics of the ferroelastic/martensitic transition has been characterized as a series of avalanches detected both from acoustic emission and calorimetric measurements. The energy distribution of these avalanche events was found to follow a power law with a characteristic energy exponent $ε\sim2$ which is in agreement with the expected value for a system undergoing a symmetry change from cubic to monoclinic. Finally, the critical behavior of the para-ferromagnetic austenite phase transition that takes place at $\sim 311$K has been studied from the behavior of the specific heat. A critical exponent $α\sim0.09$ has been obtained, which has been shown to be in agreement with previous values reported for Ni-Mn-Ga alloys but different from the critical divergence reported for pure Ni.

cond-mat.mtrl-sci↗

arXiv2020

Suppression of acoustic emission during superelastic tensile cycling of polycrystalline Ni$_{50.4}$Ti$_{49.6}$

We investigate acoustic emission (AE) that arises during the martensitic transition in a polycrystalline specimen of the prototypical superelastic/elastocaloric alloy Ni$_{50.4}$Ti$_{49.6}$ (at. %) driven using tensile strain. We use two independent AE sensors in order to locate AE events, and focus on contributions to the AE that arise away from the grips of the mechanical testing machine. Significant AE activity is present during the first mechanical loading primarily due to nucleation and growth of wide Lüders-like bands during the forward martensitic transition (imaged using visible light and infrared (IR) radiation) that lead to persistent changes in intergranular interactions. AE activity is suppressed during the subsequent reverse martensitic transition on unloading, and in successive loading/unloading cycles, for which the Lüders-like bands narrow and modify intergranular interactions to much less extent. After the first loading, we find that the AE activity associated with the martensitic transition is weak, and we suggest that this is because the elastic anisotropy and strain incompatibility in Ni-Ti are low. We also find that the AE activity becomes weaker on mechanically cycling due to increased retained martensite.

cond-mat.mtrl-sci↗

arXiv2019

Universality of power-law exponents by means of maximum likelihood estimation

Power-law type distributions are extensively found when studying the behaviour of many complex systems. However, due to limitations in data acquisition, empirical datasets often only cover a narrow range of observation, making it difficult to establish power-law behaviour unambiguously. In this work we present a statistical procedure to merge different datasets with the aim of obtaining a broader fitting range for the statistics of different experiments or observations of the same system or the same universality class. This procedure is applied to the Gutenberg-Richter law for earthquakes and for synthetic earthquakes (acoustic emission events) generated in the laboratory: labquakes. Different earthquake catalogs have been merged finding a Gutenberg-Ricther law holding for more than eight orders of magnitude in seismic moment. The value of the exponent of the energy distribution of labquakes depends on the material used in the compression experiments. By means of the procedure exposed in this manuscript, it has been found that the Gutenberg-Richter law for earthquakes and charcoal labquakes can be characterized by the same power-law exponent.

physics.data-an↗

arXiv2018

Experimental evidence of accelerated seismic release without critical failure in acoustic emissions of compressed nanoporous materials

The total energy of acoustic emission (AE) events in externally stressed materials diverges when approaching macroscopic failure. Numerical and conceptual models explain this accelerated seismic release (ASR) as the approach to a critical point that coincides with ultimate failure. Here, we report ASR during soft uniaxial compression of three silica-based (SiO$_2$) nanoporous materials. Instead of a singular critical point, the distribution of AE energies is stationary and variations in the activity rate are sufficient to explain the presence of multiple periods of ASR leading to distinct brittle failure events. We propose that critical failure is suppressed in the AE statistics by dissipation and transient hardening. Some of the critical exponents estimated from the experiments are compatible with mean field models, while others are still open to interpretation in terms of the solution of frictional and fracture avalanche models.

cond-mat.mtrl-sci↗

arXiv2017

Increasing power-law range in avalanche amplitude and energy distributions

Power-law type probability density functions spanning several orders of magnitude are found for different avalanche properties. We propose a methodology to overcome empirical constrains that limit the power-law range for the distributions of different avalanche observables like amplitude, energy, duration or size. By considering catalogs of events that cover different observation windows, maximum likelihood estimation of a global power-law exponent is computed. This methodology is applied to amplitude and energy distributions of acoustic emission avalanches in failure-under- compression experiments of a nanoporous silica glass, finding in some cases global exponents in an unprecedented broad range: 4.5 decades for amplitudes and 9.5 decades for energies. In the later case, however, strict statistical analysis suggests experimental limitations might alter the power-law behavior.

cond-mat.stat-mech↗

arXiv2017

Avalanches and force drops in displacement-driven compression of porous glasses

Similarities between force-driven compression experiments of porous materials and earthquakes have been recently proposed. In this manuscript, we measure the acoustic emission during displacement-driven compression of a porous glass. The energy of acoustic-emission events shows that the failure process exhibits avalanche scale-invariance and therefore follows the Gutenberg-Richter law. The resulting exponents do not exhibit significant differences with respect the force-driven case. Furthermore, the force exhibits an avalanche-type behaviour for which the force drops are power-law distributed and correlated with the acoustic emission events.

cond-mat.mtrl-sci↗

arXiv2016

Influence of the aspect ratio and boundary conditions on universal finite size scaling functions in the athermal metastable 2d Random Field Ising Model

This work studies universal finite size scaling functions for the number of 1d spanning avalanches in a two-dimensional disordered system with boundary conditions of different nature and different aspect ratios. For this purpose, we consider the 2d Random Field Ising Model at T = 0 driven by the external field H with athermal dynamics implemented with periodic and forced boundary conditions. We choose a convenient scaling variable z that accounts for the deformation of the distance to the critical point caused by the aspect ratio. Moreover, assuming that the dependence of the finite size scaling functions on the aspect ratio can be accounted by an additional multiplicative factor, we have been able to collapse data for different system sizes, different aspect ratios and different nature of the boundary conditions into a single scaling function Q.

cond-mat.stat-mech↗

arXiv2014

Predicting Failure: Acoustic Emission of Berlinite under Compression

Acoustic emission has been measured and statistical characteristics have been analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress collapse occurs in a series of individual events (avalanches), and each avalanche leads to a jerk in sample compression with corresponding acoustic emission (AE) signals. The distribution of AE avalanche energies can be approximately described by a power law over a large stress interval. We observed several collapse mechanisms whereby less porous minerals show the superposition of independent jerks, which were not related to the major collapse at the failure stress. In highly porous berlinite (40% and 50%) an increase of the energy emission occurred near the failure point. In contrast, the less porous samples did not show such an increase in energy emission. Instead, in the near vicinity of the main failure point they showed a reduction in the energy exponent to ~ 1.4, which is consistent with the value reported for compressed porous systems displaying critical behavior. This indicated that a critical avalanche regime with a lack of precursor events occurs. In this case, all preceding large events were false alarms and unrelated to the main failure event. Our results identify a method to use pico-seismicity detection of foreshocks to warn of mine collapse before the main failure collapse occurs, which can be applied for highly porous materials only.

cond-mat.mtrl-sci↗

arXiv2013

Crackling noise during failure of alumina under compression: effect of porosity

We study the acoustic emission avalanches during the failure process of porous alumina samples (Al2O3) under compression. Specimens with different porosities ranging from 30% to 59% have been synthetized from a mixture of fine-grained alumina and graphite. The compressive strength as well as the characteristics of the acoustic activity have been determined. The statistical analysis of the recorded acoustic emission pulses reveals, for all porosities, a broad distribution of energies with a fat tail, compatible with the existence of an underlying critical point. In the region of 35%-55% porosity, the energy distributions of the acoustic emission signals are compatible with a power law behavior over two decades in energy with an exponent ε= 1.8+/-0.1.

cond-mat.mtrl-sci↗

arXiv2012

Statistical similarity between the compression of a porous material and earthquakes

It has been long stated that there are profound analogies between fracture experiments and earthquakes; however, few works attempt a complete characterization of the parallelisms between these so separate phenomena. We study the Acoustic Emission events produced during the compression of Vycor (SiO2). The Gutenberg-Richter law, the modified Omori's law, and the law of aftershock productivity are found to hold for a minimum of 5 decades, are independent of the compression rate, and keep stationary for all the duration of the experiments. The waiting-time distribution fulfills a unified scaling law with a power-law exponent close to 2.45 for long times, which is explained in terms of the temporal variations of the activity rate.

physics.geo-ph↗

arXiv2012

Analysis of power-law exponents by maximum-likelihood maps

Maximum-likelihood exponent maps have been studied as a technique to increase the understanding and improve the fit of power-law exponents to experimental and numerical simulation data, especially when they exhibit both upper and lower cut-offs. The use of the technique is tested by analyzing seismological data, acoustic emission data and avalanches in numerical simulations of the 3D-Random Field Ising model. In the different examples we discuss the nature of the deviations observed in the exponent maps and some relevant conclusions are drawn for the physics behind each phenomenon.

cond-mat.stat-mech↗

arXiv2011

Uncertainty Relations in Statistical Mechanics: a numerical study in small lattice systems

We have analyzed the validity of uncertainty relations between the fluctuations of thermodynamically conjugated extensive and intensive variables within the field of statistical mechanics. Analysis is presented for two particular examples of small lattice systems that are in contact with reservoirs of comparable sizes: an Ising paramagnet and an Ising ferromagnet. The numerical results enable determination of the range of applicability of the proposed relations. Due to the fact that the examples correspond to systems described by discrete variables, the uncertainty relations are not valid if the probability of boundary states is too high.

cond-mat.stat-mech↗

arXiv2010

Recent topics on metastability, hysteresis, avalanches, and acoustic emission associated to martensitic transitions in functional materials

We review some results for the dynamics of first-order phase transitions in functional materials. We especially focus on simple models of athermal evolution in driven ferromagnets that give a global picture of metastability and hysteresis, showing that first-order phase transitions in such systems proceed by avalanches. Within this theoretical framework, we then discuss recent experiments on acoustic emission avalanches in structural phase transitions.

cond-mat.mtrl-sci↗

arXiv2009

Correlations in avalanche critical points

Avalanche dynamics and related power law statistics are ubiquitous in nature, arising in phenomena like earthquakes, forest fires and solar flares. Very interestingly, an analogous behavior is associated with many condensed matter systems, like ferromagnets and martensites. Bearing it in mind, we study the prototypical 3D RFIM at T=0. We find a finite correlation between waiting intervals between avalanches and the previous avalanche size. This correlation is not found in other models for avalanches, such as the standard BTW model, but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points which are at the end of an athermal first-order transition line separating two behaviors: one with high activity from another with low activity.

cond-mat.dis-nn↗

arXiv2008

Work distributions in the T=0 Random Field Ising Model

We perform a numerical study of the three-dimensional Random Field Ising Model at T=0. We compare work distributions along metastable trajectories obtained with the single-spin flip dynamics with the distribution of the internal energy change along equilibrium trajectories. The goal is to investigate the possibility of extending the Crooks fluctuation theorem to zero temperature when, instead of the standard ensemble statistics, one considers the ensemble generated by the quenched disorder. We show that a simple extension of Crooks fails close to the disordered induced equilibrium phase transition due to the fact that work and internal energy distributions are very asymmetric.

cond-mat.dis-nn↗

arXiv2008

Elastocaloric effect associated with the martensitic transition in shape-memory alloys

The elastocaloric effect in the vicinity of the martensitic transition of a Cu-Zn-Al has been studied by inducing the transition by strain or stress measurements. While transition trajectories show significant differences, the entropy change associated with the whole transformation (\DeltaSt) is coincident in both kind of experiments since entropy production is small compared to \DeltaSt. The values agree with estimations based on the Clausius- Clapeyron equation. The possibility of using these materials for mechanical refrigeration is also discussed.

cond-mat.mtrl-sci↗

arXiv2007

Random Field Potts model with dipolar-like interactions: hysteresis, avalanches and microstructure

A model for the study of hysteresis and avalanches in a first-order phase transition from a single variant phase to a multivariant phase is presented. The model is based on a modification of the Random Field Potts model with metastable dynamics by adding a dipolar interaction term truncated at nearest neighbors. We focus our study on hysteresis loop properties, on the three-dimensional (3D) microstructure formation and on avalanche statistics.

cond-mat.stat-mech↗

arXiv2007

Hysteresis in a system driven by either generalized force or displacement variables

We report on experiments aimed at comparing the hysteretic response of a Cu-Zn-Al single crystal undergoing a martensitic transition under strain-driven and stress-driven conditions. Strain-driven experiments were performed using a conventional tensile machine while a special device was designed to perform stress-driven experiments. Significant differences in the hysteresis loops were found. The strain-driven curves show re-entrant behaviour (yield point) which is not observed in the stress-driven case. The dissipated energy in the stress-driven curves is larger than in the strain-driven ones. Results from recently proposed models qualitatively agree with experiments.

cond-mat.mtrl-sci↗