Margarita Gonzalez - Academia.edu (original) (raw)

Papers by Margarita Gonzalez

Sensors

Industrial robotic arms integrated with server computers, sensors and actuators have revolutioniz... more Industrial robotic arms integrated with server computers, sensors and actuators have revolutionized the way automated non-destructive testing is performed in the aeronautical sector. Currently, there are commercial, industrial robots that have the precision, speed and repetitiveness in their movements that make them suitable for use in numerous non-destructive testing inspections. Automatic ultrasonic inspection of complex geometry parts remains one of the most difficult challenges in the market. The closed configuration, i.e., restricted access to internal motion parameters, of these robotic arms makes it difficult for an adequate synchronism between the movement of the robot and the acquisition of the data. This is a serious problem in the inspection of aerospace components, where high-quality images are necessary to assess the condition of the inspected component. In this paper, we applied a methodology recently patented for the generation of high-quality ultrasonic images of com...

Sensors

A new versatile and geometrically reconfigurable ultrasonic tomography system (UTS) has been desi... more A new versatile and geometrically reconfigurable ultrasonic tomography system (UTS) has been designed to inspect and obtain information about the internal structure and inner damage of columns in heritage buildings. This nondestructive system is considered innovative because it aims to overcome common limitations of existing systems. Tomographic inspections are typically carried out manually and are thus limited to small portions of construction elements. The proposed UTS allows the automatization of the inspection and the generation of numerous tomographic slices along the height of the column. It is valid for multiple types of columns and materials. In the present work, the system was tested on two limestone columns of the north façade of the Convent of Carmo in Lisbon, Portugal. The UTS is composed of a mechanical and an electronic system. The mechanical system consists of four linear motion subsystems mounted in a square setup. A transducer is placed on each of the axes, acting ...

Sensors, 2014

A new smart concrete aggregate design as a candidate for applications in structural health monito... more A new smart concrete aggregate design as a candidate for applications in structural health monitoring (SHM) of critical elements in civil infrastructure is proposed. The cement-based stress/strain sensor was developed by utilizing the stress/strain sensing properties of a magnetic microwire embedded in cement-based composite (MMCC). This is a contact-less type sensor that measures variations of magnetic properties resulting from stress variations. Sensors made of these materials can be designed to satisfy the specific demand for an economic way to monitor concrete infrastructure health. For this purpose, we embedded a thin magnetic microwire in the core of a cement-based cylinder, which was inserted into the concrete specimen under study as an extra aggregate. The experimental results show that the embedded MMCC sensor is capable of measuring internal compressive stress around the range of 1-30 MPa. Two stress sensing properties of the embedded sensor under uniaxial compression were studied: the peak amplitude and peak position of magnetic

Sensors, 2014

This paper deals with the study of damage produced during freeze-thaw (F-T) cycles using two non-... more This paper deals with the study of damage produced during freeze-thaw (F-T) cycles using two non-destructive measurement approaches-the first approach devoted to continuous monitoring using embedded sensors during the cycles, and the second one, performing ultrasonic imaging before and after the cycles. Both methodologies have been tested in two different types of concrete specimens, with and without air-entraining agents. Using the first measurement approach, the size and distribution of pores were estimated using a thermoporometrical model and continuous measurements of temperature and ultrasonic velocity along cycles. These estimates have been compared with the results obtained using mercury porosimetry testing. In the second approach, the damage due to F-T cycles has been evaluated by automated ultrasonic transmission and pulse-echo inspections made before and after the cycles. With these inspections the variations in the dimensions, velocity and attenuation caused by the accelerated F-T cycles were determined.

RESUMEN En este trabajo se presentan resultados preliminares de una amplia investigación que busc... more RESUMEN En este trabajo se presentan resultados preliminares de una amplia investigación que busca analizar la resistencia a impacto de mortero de cemento reforzado con fibra de vidrio (glass fibre reinforced cement, GRC), así como la influencia de diversos aditivos sobre la pérdida de resistencia con el tiempo. Se utilizan los ensayos no destructivos por ultrasonidos para valorar el daño a impacto en placas de GRC. La valoración de los daños se ha realizado mediante imágenes ultrasónicas (BSCAN, CSCAN y DSCAN), obtenidas a partir de inspecciones pulso/eco realizadas a las frecuencias de 2 y 5 MHz .

Construction and Building Materials, 2019

In this paper a system is presented to monitor in-situ the curing process of sprayed concrete. Th... more In this paper a system is presented to monitor in-situ the curing process of sprayed concrete. This system consists of an instrumented trough based on wireless sensor networks for monitoring temperature/relative humidity and ultrasounds. The trough has been designed using a trapezoidal cast with several encapsulated transducers and an electronic system for generation, acquisition and processing of ultrasonic signals. A methodology for the measurement of ultrasonic velocity has also been proposed. This system has been proven to be a very good solution for in-situ monitoring of the curing process of sprayed concrete, being able to detect problems or defects in the material fabrication.

&lt;p&gt;The upcoming JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper... more &lt;p&gt;The upcoming JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper (NASA) missions will perform detailed observations of the giant gaseous planet Jupiter and three of its largest moons (Ganymede, Callisto, and Europa).&lt;/p&gt; &lt;p&gt;A series of experiments was performed to measure the thermal conductivity and calorimetry of macroscopic frozen salt solutions of particular interest in Jovian icy moons. The following salts were investigated: Na-chloride (NaCl), Mg-sulphate (MgSO&lt;sub&gt;4&lt;/sub&gt;), sodium sulphate (Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;), and Magnesium chloride (MgCl&lt;sub&gt;2&lt;/sub&gt;). Measurements were performed at atmospheric pressure and temperatures from 0 to -70&amp;#186;C in a climatic chamber. Temperature and thermal conductivity were measured during the course of the experiments. A small sample of the liquid salt-water solution was set aside for the calorimetry measurements. A side effect of the measurements is that they served to spot phase changes in the ice mixtures with high sensitivity. An important result is that, the phase changes observed in the standard calorimetric tests, could be monitored in situ with high sensitivity in the thermal conductivity measurements. Indeed, when a phase change occurs, a large peak appeared in the thermal conductivity values as the result of the natural heat release that accompanied the phase change.&amp;#160;&lt;/p&gt;

El creciente numero de estructuras de hormigon con sintomas de deterioro prematuro debido a la ac... more El creciente numero de estructuras de hormigon con sintomas de deterioro prematuro debido a la accion ambiental, demanda investigar procedimientos para estimar la durabilidad de este tipo de componentes. La durabilidad del hormigon esta estrechamente relacionada con la porosidad, la cual determina la intensidad de las interacciones del material con los agentes agresivos. Los poros y capilares en el interior de la estructura facilitan el proceso destructivo, el cual generalmente comienza en la superficie. En este trabajo, se desarrollan tecnicas no destructivas para estimar la porosidad del hormigon a partir de la velocidad acustica en el material. Cuando una onda ultrasonica se propaga a traves del material, la velocidad acustica esta relacionada con la densidad y los componentes Cij de rigidez del material. Dado que estas propiedades dependen de la porosidad, se puede establecer una correlacion entre la velocidad acustica y la densidad y/o el volumen de poros. Usando esta propiedad...

En este trabajo se propone la caracterizacion de la estructura porosa de materiales cementicios m... more En este trabajo se propone la caracterizacion de la estructura porosa de materiales cementicios mediante ensayos no destructivos por ultrasonidos. Si tenemos en cuenta que la informacion de la porosidad esta contenida implicitamente en la densidad del material y que esta a su vez esta relacionada explicitamente con la velocidad, intentaremos hallar una relacion entre la porosidad y la velocidad de las ondas ultrasonicas. Por otro lado la atenuacion de las ondas acusticas sera determinada a partir de la informacion contenida en la energia ultrasonica que atraviesa el material, lo cual nos permitira estudiar distintos parametros que presentan discriminacion con respecto al volumen de poros y establecer a partir de estos una relacion entre la atenuacion y la porosidad. Los resultados obtenidos con las tecnicas ultrasonicas han sido comparados con los ensayos destructivos, y muestran muy buena concordancia.

Construction and Building Materials, 2021

Abstract The development of early age properties of sprayed concrete is a key factor that governs... more Abstract The development of early age properties of sprayed concrete is a key factor that governs its mix design and safe application. The conventional methods to evaluate the evolution of mechanical strength in sprayed concrete present a large interval between each set of measurements and results present a high scatter. In this context, the objective of this study is to characterize the early age properties of sprayed mortars through a novel continuous monitoring system based on in situ ultrasound measurements. Sprayed mortars were also analyzed by isothermal calorimetry, needle penetration and stud driving method. Results indicate that the system developed here can monitor the evolution of early age properties of sprayed mortars continuously without the common drawbacks observed in penetration tests. This research may lead to the development of a more reliable procedure to characterize the early age mechanical properties of sprayed materials in the worksite under safer conditions.

&amp;lt;p&amp;gt;In the coming years The JUpiter ICy moons Explorer (JUICE) (ESA)... more &amp;lt;p&amp;gt;In the coming years The JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper (NASA) missions will study the icy crusts of the main Galilean moons of Jupiter. They will use the penetrating radars RIME and REASON, which will work at wave frequency ranges able to penetrate up to 9 and 30 Km depth respectively, in combination with other instruments [Bruzzone et al. 2013, Aglyamov et al. 2017].&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;In this regard, we have started a set of experiments to study the electrical properties of materials at low temperatures with the aim to help with the interpretation obtained from the level of attenuation of the radar waves. Ultimately, they will be useful to constrain the chemical composition, physical state and temperature of the upper layers of the icy crusts of Ganymede, Callisto and Europa (please see abstracts EPSC Gonz&amp;amp;#225;lez D&amp;amp;#237;az et al. 2020 and EPSC Solomonidou et al. 2020).&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;The first set of experiments have been done in a high-pressure chamber equipped with pressure and temperature sensors in direct contact with the sample and a large sapphire window which allows textural and spectroscopic analyses. We have characterized aqueous solutions with salts (MgSO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;, NaCl, MgCl&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, Mg(ClO&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;)&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, Na&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;CO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;), volatiles (CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;) and clays (nontronite, montmorillonite) at temperatures down to 223 K and pressures up to 60 MPa. Samples were studied by pressure-temperature (P-T) cycles in two ways: (a) first freezing the solution and pressurizing it (TPPT method) and (b) first pressurizing the solution and then freezing it (PTTP method), in order to examine textural and grain size heterogeneities and fracture formation depending on the method of formation. The cooling of the samples led to the final formation of water ice, hydrated salts and clathrate hydrates. Raman spectroscopy was used to control the mineral assemblages and understand better the crust environments and processes that can explain the resulting values, like the appearance of supercooled brines, amorphous phases and recrystallizations during the P-T cycles.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;We measured the dielectric properties of these samples with a BDS80 Broadband Dielectric Spectroscopy system (Novocontrol) which allows to work in a frequency range from 1 Hz to 10 MHz and temperatures from 143 to 323 K. Both permittivity and electric conductivity were measured at 0.1 MPa while cooling the samples in temperature steps of 10 K. From these data we estimated, on the one hand, the activation energy for motion of the electric charges of each solution, and on the other hand, the attenuation of the radar wave depending on the chemical composition and the temperature of the sample, and the frequency of the electric field applied [Pettinelli et al. 2015].&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;The already obtained novel data will be used as reference for a second set of experiments, consisting on the same dielectric properties&amp;amp;#8217; characterization but, in this set, samples will be also subjected to high pressure conditions.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;References&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;Aglyamov et al. (2017) Bright prospects for radar detection of Europa&amp;amp;#8217;s ocean, Icarus, 281, 334-337.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;Bruzzone et al. (2013) RIME: Radar for Icy moon Exploration, IEEE International Geoscience and Remote Sensing Symposium - IGARSS, Melbourne, 3907-3910.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;Pettinelli et al. (2015) Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review, Reviews of Geophysics, 53, 593-641.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;

&lt;p&gt;Thermal properties of frozen salt solutions are crucial to interpret the... more &lt;p&gt;Thermal properties of frozen salt solutions are crucial to interpret the JUpiter ICy moons Explorer (JUICE) (ESA) and Europa Clipper (NASA) missions, which will be launched in the upcoming years to make detailed observations of the giant gaseous planet Jupiter and three of its largest moons (Ganymede, Callisto, and Europa) due to the scarcity of experimental measurements.&lt;/p&gt; &lt;p&gt;Therefore, we have conducted a set of experiments to measure and study the thermal conductivity and calorimetry of macroscopic frozen salt solutions of particular interest in these regions, including Na-chloride (NaCl), Mg-sulphate (MgSO&lt;sub&gt;4&lt;/sub&gt;), sodium sulphate (Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;), and Magnesium chloride (MgCl&lt;sub&gt;2&lt;/sub&gt;). A climatic chamber has been used to mimic the cryogenic conditions in the Jovian Icy Moons. Measurements were performed at atmospheric pressure and temperatures from 0 to -70&amp;#186;C. Temperature and thermal conductivity were measured during the course of the experiments. A side effect of these measurements is that they served to spot phase changes in the ice mixtures. A small sample of the liquid salt-water solution was set aside for the calorimetry measurements.&lt;/p&gt; &lt;p&gt;These experiments and the measurements of thermal conductivity and calorimetry will be valuable to constrain the chemical composition, physical state, and temperature of the upper layers of the icy crusts of Ganymede, Callisto, and Europa (please see abstracts EPSC Mu&amp;#241;oz Iglesias et al. 2020 and EPSC Solomonidou et al. 2020).&lt;/p&gt;

Sensors, 2019

In this paper, a magnetic microwire-based sensor array embedded under the pavement is proposed as... more In this paper, a magnetic microwire-based sensor array embedded under the pavement is proposed as a weighing system at customs ports of entry. This sensor is made of a cementitious material suitable for embedding within the core of concrete structures prior to curing. The objective of this research is to verify the feasibility of stress monitoring for concrete materials using an array of cement-based stress/strain sensors that have been developed using the magnetic sensing property of an embedded microwire in a cement-based composite. Test results for microwire-based sensors and gauge sensors are compared. The strain sensitivity and their linearity are investigated through experimental testing under compressive loadings. Sensors made of these materials can be designed to satisfy specific needs and reduce costs in the production of sensor aggregates with improved coupling performance, thus avoiding any disturbance to the stress state.

Sensors, 2019

In different disciplines of science, the knowledge of the resulting pressures in the subsoil can ... more In different disciplines of science, the knowledge of the resulting pressures in the subsoil can help to understand physical phenomena of mass exchange between the atmosphere and the terrain. The measurement of lower differential pressures is complicated given the low range of detected values. In this paper, a multisensor system has been designed and developed to measure differential pressures in radon gas transport studies. The adequacy of this system has been proven using a purpose-built pressure chamber and an automatic motion system developed by the authors. The temporal response frequencies, the pressure values measured by the sensors, and their ability to link in series were analyzed to offer a multisensor spatial and temporal mapping. At the same time, the influence of the components required for a real deployment were studied using different tube lengths and diameters, connectors, and obstructions across the operating range of the pressure sensors. The system has also been t...

Sensors (Basel, Switzerland), Jan 10, 2017

This study explores the feasibility of using transmission tomographic images based on attenuation... more This study explores the feasibility of using transmission tomographic images based on attenuation measures in transmission to detect and estimate the most common materials that are embedded in concrete, reinforcements and natural and artificial voids. A limited set of concrete specimens have been made in which cylindrical objects such as bars/tubes of steel, PVC and aluminium have been embedded to analyse the effect of size and material. The methodology and scope of this study is presented and numerical simulations are carried out to optimize the emitter-receiver configuration and to understand the complex physical propagation phenomena of ultrasonic signals that travel through concrete with embedded inclusions. Experimental tomographic images are obtained by using an ultrasonic tomographic system, which has the advantage of needing only two ultrasonic transducers. Both the software simulation tool and the tomographic inspection system are developed by the authors. The obtained resu...

Anales De Mecanica De Fractura 2011 Xxviii Encuentro Del Grupo Espanol De Fractura 06 04 2011 08 04 2011 Gijon Espana, 2011

Construction and Building Materials, 2016

In ultrasonic non destructive evaluation (UT-NDE) of highly scattering materials, detection of li... more In ultrasonic non destructive evaluation (UT-NDE) of highly scattering materials, detection of little flaw echoes is difficult due to the masking effect of the structural noise. Most of the proposed techniques for enhancing the flaw visibility do not exploit the spectra of the structural noise and the incoming flaw signal depth dependency. They assume homogeneous behavior of the insonified material in order to design the processing algorithms. In this work, a multiresolution-based spectral subtraction method for enhancing the flaw signal to structural noise ratio (SNR) is proposed. This method, using the wavelet transform, exploits the non-stationary characteristic of the structural noise. First step of this algorithm is the time-scale estimation of several statistics of the structural noise. On the second step, non-linear over-subtraction of the raw signal wavelet transform is applied. This strategy produces improved results in SNR compared with linear and non- over-subtraction tec...

Sensors

Sensors, 2014

Construction and Building Materials, 2019

Construction and Building Materials, 2021

Sensors, 2019

Sensors (Basel, Switzerland), Jan 10, 2017

Anales De Mecanica De Fractura 2011 Xxviii Encuentro Del Grupo Espanol De Fractura 06 04 2011 08 04 2011 Gijon Espana, 2011

Construction and Building Materials, 2016