Use of Higher-Harmonic and Intermodulation Generation of Ultrasonic Waves to Detecting Cracks due to Steel Corrosion in Reinforced Cement Mortar

Miguel Angel Climent-Llorca,Marina Miro-Oca,Pedro Poveda-Martinez,Jaime Ramis-Soriano 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.6

The aim of this work was to provide further confirmation of the possible use of non-linear ultrasonic techniques for detecting the cracking due to corrosion of steel reinforcements in concrete. To this end accelerated steel corrosion tests have been conducted on model reinforced cement mortar specimens, while monitoring the appearance and width evolution of visible surface cracks, and performing non-linear ultrasonic measurements based on the phenomena of harmonic distortion and intermodulation. A new parameter, based on the difference between the amplitude of the fundamental frequency and the sum of the amplitudes of all the first-order and second-order intermodulation products, has been proposed in this work. The results confirm that the appearance of visible surface micro-cracks are preceded and accompanied by the observation of strong non-linear features in the received signal. Furthermore, the new parameter proposed in this work is as efficient as the relative non-linearity parameters, classically used in harmonic distortion non-linear ultrasonic studies, for detecting the non-linear features associated with the critical events of the cracking of cement mortar due to embedded steel corrosion. A hypothesis has been developed considering the possible effect of the filling of the void space by liquid containing rust products after the formation of new cracks or the enlargement of its width. This filling process, which might be particularly enhanced by net convective transport of liquid, would explain the evolution of the values of all the parameters used for putting in evidence the non-linear elastic features after the critical events of the cracking process.

A simple means of producing highly transparent graphene on sapphire using chemical vapor deposition on a copper catalyst

Anemone, Gloria,Climent-Pascual, Esteban,Al Taleb, Amjad,Yu, Hak Ki,Jimé,nez-Villacorta, Felix,Prieto, Carlos,Wodtke, Alec M.,De André,s, Alicia,Farí,as, Daniel Elsevier 2018 Carbon Vol.139 No.-

<P><B>Abstract</B></P> <P>Chemical vapor deposition (CVD) is one of the best ways to scalably grow low cost, high quality graphene on metal substrates; unfortunately, it not ideal for producing graphene on dielectric substrates. Here, we demontrate production of a high quality graphene layer on Sapphire using CVD with a copper catalyst. The catalyst consists of a thin copper film grown epitaxially on <I>α</I>- <SUB> Al 2 </SUB> <SUB> O 3 </SUB> (0001). After CVD growth of Graphene, the copper can be removed by simple evaporation in the presence of a carbon source ( <SUB> C 2 </SUB> <SUB> H 4 </SUB> ). We characterized the resulting graphene layer using Raman spectroscopy, atomic force microscopy (AFM), optical transmission and helium atom scattering (HAS). The sample exhibited a reduced Raman D peak and an excellent 2D to G ratio. AFM and HAS show large graphene domains over a macroscopic region. We measured > 86 % transparency over the visible spectrum.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Health monitoring of reinforced concrete slabs subjected to earthquake-type dynamic loading via measurement and analysis of acoustic emission signals

Gallego, Antolino,Benavent-Climent, Amadeo,Infantes, Cristobal Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.4

This paper discusses the applicability of Acoustic Emission (AE) to assess the damage in reinforced concrete (RC) structures subjected to complex dynamic loadings such as those induced by earthquakes. The AE signals recorded during this type of event can be complicated due to the arbitrary and random nature of seismicity and the fact that the signals are highly contaminated by many spurious sources of noise. This paper demonstrates that by properly filtering the AE signals, a very good correlation can be found between AE and damage on the RC structure. The basic experimental data used for this research are the results of fourteen seismic simulations conducted with a shake table on an RC slab supported on four steel columns. The AE signals were recorded by several low-frequency piezoelectric sensors located on the bottom surface of the slab. The evolution of damage under increasing values of peak acceleration applied to the shake table was monitored in terms of AE and dissipated plastic strain energy. A strong correlation was found between the energy dissipated by the concrete through plastic deformations and the AE energy calculated after properly filtering the signals. For this reason, a procedure is proposed to analyze the AE measured in a RC structure during a seismic event so that it can be used for damage assessment.

Health monitoring of reinforced concrete slabs subjected to earthquake-type dynamic loading via measurement and analysis of acoustic emission signals

Antolino Gallego,Amadeo Benavent-Climent,Cristóbal Infantes 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.4

This paper discusses the applicability of Acoustic Emission (AE) to assess the damage in reinforced concrete (RC) structures subjected to complex dynamic loadings such as those induced by earthquakes. The AE signals recorded during this type of event can be complicated due to the arbitrary and random nature of seismicity and the fact that the signals are highly contaminated by many spurious sources of noise. This paper demonstrates that by properly filtering the AE signals, a very good correlation can be found between AE and damage on the RC structure. The basic experimental data used for this research are the results of fourteen seismic simulations conducted with a shake table on an RC slab supported on four steel columns. The AE signals were recorded by several low-frequency piezoelectric sensors located on the bottom surface of the slab. The evolution of damage under increasing values of peak acceleration applied to the shake table was monitored in terms of AE and dissipated plastic strain energy. A strong correlation was found between the energy dissipated by the concrete through plastic deformations and the AE energy calculated after properly filtering the signals. For this reason, a procedure is proposed to analyze the AE measured in a RC structure during a seismic event so that it can be used for damage assessment.

STRATEGIES FOR IMPROVING THE MODE TRANSITION IN A SEQUENTIAL PARALLEL TURBOCHARGED AUTOMOTIVE DIESEL ENGINE

J.GALINDO,H. CLIMENT,C. GUARDIOLA,J. DOMÉNECH 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.2

Parallel sequential turbocharging systems are able to operate in different modes, which are defined according to the turbochargers that simultaneously boost the engine, and are controlled by means of specific valves. In order to cover the full engine operating range, a smooth transition between turbocharging operating modes must be ensured. However, important disturbances affect both boost and exhaust pressure when shifting the operation mode, thus causing non-negligible torque oscillations. This paper presents different methods for smoothing such undesirable effects during mode transition. Strategies covering optimal synchronization of the control valves, control of the valves’ position, and correction of the injected fuel during the transition are analysed. A fully instrumented passenger car engine is used for illustrating the different torque smoothing methods, and experimental results for transitions during both steady operation and engine accelerations are shown.

EGR TRANSIENT OPERATIONS IN HIGHLY DYNAMIC DRIVING CYCLES

Jose Galindo,Hector Climent,Benjamin Pla,Chaitanya Patil 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.4

EGR is one of the proven and well tested strategies within the specific operating range of the engine. Necessity of an implementation of this exhaust gas recirculation all over the engine operating range is emerging. Therefore, a systematic study has been carried out to identify the specific and frequent transient operations on newly developed dynamic cycles like WLTC and RDE. To perform detailed observations, these transients are imitated individually on the diesel engine test bench. High frequency gas analyzers are used to track the instantaneous CO2 and NOx concentration respectively at the intake and exhaust lines of the engine. A parametric study has been carried out using different valve movement profiles of the LPEGR and HPEGR during severe engine load change operations. An analysis is presented suggesting the best suited valve control during these harsh transients which can be helpful for transient calibration of a turbocharged diesel engine. The effect of length of Long route LPEGR line is also acknowledged. This study reveals the dynamic behavior of a diesel engine during transient operation with exhaust gas recirculation. It outlines the trade-off between performance and NOx emission and opacity for the initial phase of the transient before acquiring the steady state situation.

Analysis of Gas-Dynamic Effects in Compact Exhaust Systems of Small Two-Stroke Engines

J. GALINDO,J. R. SERRANO,H. CLIMENT,A. TISEIRA 한국자동차공학회 2007 International journal of automotive technology Vol.8 No.4

This article describes a methodology based on experiments and 1D modeling work related to the exhaust system analysis of a small two-stroke engine. The primary goal of this work was to understand how the design criteria of a compact exhaust system influenced the exhaust port pressure, since its evolution controls not only engine performance but also exhaust emissions. On the experimental side, a fully instrumented 50cc two-stroke engine was used to check the behavior of three different exhaust systems. A problem related to instantaneous pressure measurements in unsteady, hot flow was detected and solved during the study. To build the 1D model of the three exhaust systems, experimental information on the steady flow and the impulse test rigs was obtained under controlled conditions in specific facilities. Accurate comparisons between measured and calculated exhaust port instantaneous pressures were obtained from the following different exhaust system configurations: a straight duct, a tapered pipe and the three compact exhaust systems. The last step in the method used this model to analyze the pressure waves inside the exhaust system and detect the influence of the geometric parameters. The results should lead to improvements in the design process of complex compact exhaust systems in two-stroke engines.

ANALYSIS OF GAS-DYNAMIC EFFECTS IN COMPACT EXHAUST SYSTEMS OF SMALL TWO-STROKE ENGINES

Galindo, J.,Serrano, J.R.,Climent, H.,Tiseira, A. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.4

This article describes a methodology based on experiments and 1D modeling work related to the exhaust system analysis of a small two-stroke engine. The primary goal of this work was to understand how the design criteria of a compact exhaust system influenced the exhaust port pressure, since its evolution controls not only engine performance but also exhaust emissions. On the experimental side, a fully instrumented 50cc two-stroke engine was used to check the behavior of three different exhaust systems. A problem related to instantaneous pressure measurements in unsteady, hot flow was detected and solved during the study. To build the 1D model of the three exhaust systems, experimental information on the steady flow and the impulse test rigs was obtained under controlled conditions in specific facilities. Accurate comparisons between measured and calculated exhaust port instantaneous pressures were obtained from the following different exhaust system configurations: a straight duct, a tapered pipe and the three compact exhaust systems. The last step in the method used this model to analyze the pressure waves inside the exhaust system and detect the influence of the geometric parameters. The results should lead to improvements in the design process of complex compact exhaust systems in two-stroke engines.

Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules

Zhou, Xinran,Royo, Miquel,Liu, Weiwen,Lee, Jihoon H.,Salamo, Gregory J.,Climente, Juan I.,Doty, Matthew F. American Physical Society 2015 Physical review. B, Condensed matter and materials Vol.91 No.20

New optimum distribution of lateral strength of shear-type buildings for uniform damage

Jesús Donaire-Á vila,Andrea Lucchini,Amadeo Benavent-Climent,Fabrizio Mollaioli 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.3

The seismic design of conventional frame structures is meant to enhance plastic deformations at beam ends and prevent yielding in columns. To this end, columns are made stronger than beams. Yet yielding in columns cannot be avoided with the column-to-beam strength ratios (about 1.3) prescribed by seismic codes. Preventing plastic deformations in columns calls for ratios close to 4, which is not feasible for economic reasons. Furthermore, material properties and the rearrangement of geometric shapes inevitably make the distribution of damage among stories uneven. Damage in the i-th story can be characterized as the accumulated plastic strain energy (Wpi) normalized by the product of the story shear force (Qyi) and drift (yi) at yielding. Past studies showed that the distribution of the plastic strain energy dissipation demand, Wpi /Wpj, can be evaluated from the deviation of Qyi with respect to an “optimum value” that would make the ratio Wpi/(Qyiyi) —i.e. the damage— equal in all stories. This paper investigates how the soil type and ductility demand affect the optimum lateral strength distribution. New optimum lateral strength distributions are put forth and compared with others proposed in the literature.