Key Engineering Materials Vol. 495

Abstract: The fiber optic Bragg grating (FBG) sensors have been recently introduced: they presenta photo-record grating on the fiber itself, which allows the reflection of a certain wavelength of theinput light spectrum. The applied strain is estimated based on changes of the reflected wavelength.The metrological characteristics of FBGs have been tested and compared to strain gages ones, whichrepresent the actual reference measurement systems. It was decided to integrate the measurementsystem directly into a composite material, having achieved good results during the static and dynamictests [1]. We made carbon fiber specimens (two for traction and two for bending tests) with FBGsintegrated into them. The results were surprising: the integration of ``nude'' fiber optic sensor didnot cause damage or deterioration in the quality of measurement, the signal noise was maintained atbaseline levels and response to dynamic stress was definitely comparable to that offered by electricalstrain gauges

Abstract: In this work, we demonstrate the possibility to use optical fiber incorporating photowritten tilted fiber Bragg gratings (TFBG) as optical detection system for the real time monitoring of interfacial adsorption events and biological recognition. For this purpose, immobilization of cyclodextrin polymers onto the surface of optical fiber was envisioned through the layer-by-layer self-assembly method with the aim of developing sensing layers with well-defined host properties. To develop a biological sensor, amphiphilic dextran, acting as intermediate layer between the polyelectrolyte multilayer assembly and the biological probe, was immobilized though inclusion complex formation. The dextran layer exhibit a dual functionality: (i) it prevents non-specific proteins adsorption and (ii) it allows covalent immobilization of anti-bovine serum albumine through activation of the hydroxyl groups with 1,1’-carbonyl diimidazole. To verify the feasibility of our strategy, fluorescence microscopy was applied to evidence the effective inclusion of fluorescent macromolecular – flurorescein labelled dextran bearing adamantane as side-grafts – species within the cyclodextrin cavities present onto the optical fiber interface and at the last layer to prove the grafting of anti bovin serum albumin onto the amphiphilic dextran by a capture of fluorescein bovin serum albumin by the antibody layer. In a further step, it was demonstrated that the elaboration of the multilayer assembly can be monitored in real time using the TFBG sensor.

Abstract: In this work, we demonstrate the possibility to use optical fiber incorporating photowritten tilted fiber Bragg gratings (TFBG) as optical detection system for the real time monitoring of interfacial adsorption events. For this purpose, immobilization of cyclodextrin polymers onto the surface of optical fiber was envisioned through the layer-by-layer self-assembly method with the aim of developing sensing layers with well-defined host properties. To verify the feasibility of our strategy, fluorescence microscopy was applied to evidence the effective inclusion of fluorescent molecular, toluene, within the cyclodextrin cavities present onto the optical fiber interface. In a further step, it was demonstrated that the elaboration of the multilayer assembly can be monitored in real time using the TFBG sensor. The host properties of the as-prepared sensing layers were directly applied to develop chemical sensor sensitive to toluene. It was found that the TFBG response was related to the toluene concentration and a linear dependence was observed in the low concentration regime.

Abstract: The fiber Bragg grating sensors (FBGs) have been recently introduced: they present a photorecord grating on the fiber itself, which allows the reflection of a certain wavelength of the input light spectrum. The applied strain is estimated relying on changes of the reflected wavelength. One of the possible applications that has prompted us to study this type of sensors is the possibility to create smart dynamometric structures based on carbon fiber by embedding FBGs. Many papers are available in literature about some applications with smart structures but there is not yet an appropriate metrological characterization about these FBG sensors, their strengths and weaknesses: for these reasons it was deemed useful making several tests on FBG sensors in terms of measurement accuracy, signal to noise ratio, ability to compensate for thermal effects and their behavior for dynamic applications. All these results have been compared to electrical strain gauge ones, which represent the actual reference strain measurement systems. The various solutions to compensate for thermal effects have offered several information for further analyses and the basis for a future use of these sensors for static or semi-static tests. Being fully aware of FBGs characteristics allows to draw down guidelines about their integration in composite materials for the most different applications, understanding in a better way the sensor response.

Abstract: Removed due to double publication.

Abstract: Most materials expand upon heating due to the anharmonicity of the atomic potential energy. This thermal expansion is one of the intrinsic properties of any material which is very difficult to be controlled. Recently, a negative thermal expansion factor was introduced to those Ti-alloys with high elastic softening when cold deformed. This negative thermal expansion factor is changeable in these types of alloys depending on the alloy composition, degree of cold deformation, and thermal history of the alloy. This change gives a lot of room to control the coefficient of thermal expansion (CTE) of those Ti-alloys to turn from positive though zero to negative values and vice versa. In this paper, the appearance of the NTE factor is discussed and the possible methods to control the final thermal expansion coefficient to achieve a zero thermal expansion coefficient are presented. The unique thermal expansion behavior of the alloys will locate them as an excellent candidate in sensing apparatus and other precious equipments.

Abstract: In this paper, switched reluctance motors (SRM) are proposed as an alternative for electric power assisted steering (EPAS) applications. A prototype machine has been developed as very attractive design for a steering electric motor, both from a cost and size perspective. A four-phase 8/6 SRM drive is designed for a rack type EPAS which should provide a maximum force of 10 kN. Two-dimension finite element analysis is used to validate the design.

Abstract: Actual trends in machinery maintenance point to the necessity of an on-line real-time monitoring of the condition of the lubricant oil. Excessive delay in replacing the lubricant oil can have catastrophic results, whereas doing it too early produces evident economic and environmental issues. Magnetoelastic materials offer a good sensing principle for assessing lubricant oil viscosity; which is one of the most important properties to assure its proper lubricant capacity. Among others, one of the most remarkable properties of this sensing principle is the capability of being used through a wide viscosity range. In this work, we describe the experiments performed to evaluate the usefulness of this technology for testing the viscosity of different test oils in order to develop a working device for on-line, real-time monitoring the quality of lubricant oils.

Abstract: Electronic nose is a device that attempts to mimic the living being smell system for detection of particular gases or volatile compounds. This paper reports the development of an optical electronic nose using Fe (III) based metalloporphyrins Langmuir-Blodgett thin films as sensing elements for discriminating four volatiles, 2-propanol, acetone, cyclohexane and ethanol. A multilayer feed forward neural network was developed to classify the input vectors from these two sensors. After the network being trained 100 times and introduced to blind samples, it was found that there are three fault decision for propanol, two for acetone, five for cyclohexane and one four ethanol, during 50 times being recognized to the samples.

Abstract: This paper reports a study on plasmonic properties of gold nanoparticles to detect the presence of formaldehyde solution in water. Gold nanoparticles were grown on substrates by the seed mediated growth method. A sensor system was setup, comprises a light source, a dual arm fibre optic probe, a spectrometer and sensor chamber. The detection of formaldehyde was done by comparing the Localized Surface Plasmon Resonance (LSPR) spectra of gold nanoparticles samples immersed in the deionised water and formaldehyde solution. It was observed that the peak position LSPR spectra of nanogold samples and their intensity were change by the presence formaldehyde. The difference between resonance peak intensity of LSPR spectra gold nanoparticles sample in formaldehyde solution and water can be used as sensing sensitivity parameter of the sensor. It was found that the sensing sensitivity is increase with the size of nanoparticles until it reach the optimum particles size.