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A Novel PZT Sensor Bonding Technique For Structural Health Monitoring Application
No full textThe piezoelectric transducers have played a vital role in the successful implementation of Structural Health Monitoring (SHM) in civil, mechanical and aerospace structures. These piezoelectric transducers are permanently bonded onto the host structure and are implemented during the design phase of these structures. However, when it comes to structure/systems in-service like an aircraft, there is a need to have instrumented transducers to be removed after the completion of health diagnosis. It is always a difficult task and requires high skilled workmanship to remove these instrumented sensors, without causing damage to host structure. Thus, the requirement for the sensor bonding arrangement which can be easily removed from the host structure is a primary requirement in aerospace industries and it is addressed in the current paper.The present research focused on the replacement of the permanently bonded PZT sensors with temporary bonding scheme. The temporary bonding in the interface of the PZT patch and the structure has been studied by using different types of adhesive tapes such as aluminum foil tape, copper foil tape and 3M scotch tape. Numerical studies have been carried in industry standard ABAQUS®, wherein the adhesive layer has been modelled to simulate the behavior for different adhesive tapes used. The workability of the proposed technique and its effectiveness in capturing the propagated Lamb waves have been demonstrated. Two plate configurations, one with permanently bonded PZT sensors and the other with temporarily bonded PZT sensors has been used for the present study. Various Lamb wave parameters such as Time of Flight (TOF), Maximum Amplitude Spectra (MAS) and Group Velocity have been computed and compared for permanently and temporarily bonded PZT sensor configurations.Further, the above two plate configuration structures with simulated damages (cut-out) have been studied. The capabilities of the adhesive tape bonded sensors to identify the simulated damage and to localize the damage have been investigated by comparing the FE results with permanently bonded sensor configurations
Non-destructive method of biomass and nitrogen (N) level estimation in Stevia rebaudiana using various multispectral indices
No full textUnmanned Aerial Vehicle (UAV) based remote sensing is one of the modern techniques for crop management, which has been used in this study for biomass and Nitrogen (N) level estimations for Stevia rebaudiana, a medicinal crop used as an alternative to sugar as a natural sweetener. Different levels of nitrogen treatments were given to S. rebaudiana and the crops were harvested for biomass estimation. Mica sense Altum multispectral sensor on board was used for acquiring the image data of the crop. The linear regression model was used to examine the best vegetation index using K-fold cross validation approach. Excess Green Index (ExG) was identified as best vegetation index for biomass estimation (R2 = 0.7; RMSE = 23.77 g/m2; nRMSE = 29.14%), whereas Enhanced Normalized Difference Vegetation Index (ENDVI) was found as best predictor for Nitrogen (N) level estimation (R2 = 0.9; RMSE = 1.75 g/m2; nRMSE = 14.59%)
Synthesis and ionic conductivity of calcium-doped ceria relevant to solid oxide fuel cell applications
No full textTowards the development of green energy devices, it is necessary to focus on commercial electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Ca-doped ceria (CDC) samples having a composition of Ce(1−x)CaxO2−δ (0.03 ≤ x ≤ 0.1) were synthesized by a facile solid-state route and sintered at a lower temperature (1473 K). X-ray diffraction, Raman, X-ray photoelectron, Fourier-transform infrared, UV–VIS diffuse reflectance, field emission scanning electron microscopy – energy dispersive X-ray with elemental mapping, and electrochemical impedance spectroscopy techniques were used for the characterization of these CDC samples. The 0.10 CDC showed high oxide ion conductivity of 8.01 × 10−3 S cm−1 at 973 K with a lower activation energy of 0.78 eV. The 0.03 CDC, 0.05 CDC, and 0.07 CDC samples exhibited ionic conductivities of 1.66 × 10−4, 4.42 × 10−3, and 5.76 × 10−3 S cm−1 at 973 K with activation energies of 1.65, 1.01, and 0.92 eV, respectively. The present work aims to develop Ca-doped ceria as economically viable electrolytes for IT-SOFCs
Microstructural effect of various polyaniline-carbon nanotube core- electrode performance
No full textVarious carbon nanotubes-polyaniline (CNT-PANI) core-shell nanocomposites such as multiwalled carbon nanotube-PANI (PAM), carboxylic acid functionalized MWCNT (cMWCNT)-PANI (PACM) and amine-functionalized MWCNT (nMWCNT)-PANI (PANM) core-shell composites are successfully prepared by in-situ chemical oxidation process using ammonium persulphate (APS). Fourier transform infrared spectrum (FTIR) analysis proves the bonding nature between CNT core and PANI shell in nanocomposites. High-resolution transmission electron microscopy (HRTEM) and Field emission scanning electron microscopy (FESEM) images confirm the nanometer-sized PANI layer over CNT or core-shell structure of CNT-PANI nanocomposites. Further, the specific capacitance of the PAM electrode is 647 Fg−1 at scan rate 1 mV s−1 and 491 Fg−1 at current density 1 Ag−1 through cyclic voltammetry (CV) and galvanostatic charge-discharge respectively (GCD) in H2SO4 (1 M) medium under an applied potential between −0.2 to +0.8 V. Among the other CNT-PANI core-sell electrodes, the PAM electrode exhibits the highest retention of specific capacitance of 98 % and maximum Coulombic efficiency of 100 % after 5000th cycles of galvanostatic charge-discharge in the same applied potential. Due to its high specific capacitance and exceptional capacitance retention, PAM composite was fabricated as symmetric supercapacitors. The highest specific capacitance of 483 Fg−1 at a scan rate of 1 mV s−1 and 268 Fg−1 at a current density of 1 Ag−1 in 6 M H2SO4 is found for PAM composite. The symmetric device delivered the maximum energy density of 37 Wh kg−1 at a power density of 166 W kg−1
Nano-sized cerium vanadium oxide as corrosion inhibitor: A microstructural and release study
No full textThe synthesized, nano-sized cerium vanadate is proposed as a self-healing corrosion inhibitor for ferrous alloys (e.g., automotive high strength steel (HSS) and mild steel (MS)). Cerium vanadate prepared at two different pH conditions (neutral and basic) showed similar corn-like morphology with nanorod structure. UV-Vis spectroscopy studies revealed that the release rate of cerium vanadate-B (basic condition) was higher than cerium vanadate-N (neutral condition) in 0.1 M NaCl solution. The specimen exposed to 0.1 M NaCl containing a supersaturated solution of cerium vanadate-B (1000 ppm) revealed 8 times and 6 times lower corrosion current density values for HSS and MS respectively than that of the one without corrosion inhibitor. There was a gradual increase in the film resistance (Rfilm) on both HSS and MS observed as a function of exposure time in corrosive medium containing cerium vanadate-B inhibitor. An order higher impedance values were observed for both HSS and MS immersed for 168 h, highlighting the self-healing effect of the cerium vanadate compound. The X-ray photoelectron spectroscopy results showed the presence of multivalent oxidation states of both cerium and vanadium species. The inhibiting action is attributed to the high solubility of cerium vanadate in the corrosive medium to form a film on the metal surface. The dissolution/solubility of the corrosion inhibitor was more favorable in neutral to alkaline conditions than in acidic conditions
Theoretical and Experimental Investigation of Friction in Hydraulic Actuators
No full textThis paper deals with the experimental verification of friction models used in the estimation of frictional forces in a hydraulic actuator. The friction force is calculated with the measured readings of pressure in the cylinder chambers and the acceleration of the piston. In order to predict friction forces in the hydraulic actuator, mathematical models, namely LuGre model and modified LuGre model, are extensively used. These models are simulated to predict the friction forces in the test actuator. The physical test setup and the simulation models are commanded with identical velocity inputs, and the results in each test case are compared. The experiment results show that the modified LuGre model with dimensionless fluid film thickness parameter predicts the friction forces in hydraulic actuator with a good accuracy when compared with the other models
Green synthesis of tin oxide based nanoparticles using Terminalia bellirica seed extract: impact of operating temperature and antimony dopant on sensitivity for carbon dioxide gas sensing application
No full textGreen synthesis of undoped tin oxide (SnO2) and 2 wt% antimony doped tin oxide (Sb:SnO2) for carbon dioxide (CO2) gas sensing application is reported. The structural, morphological and optical properties of nanoparticles were investigated using XRD, SEM, EDX, HRTEM, FTIR and UV-Vis characterisation techniques. CO2 gas sensing studies were carried out by using calibration setup on pellets of nanoparticles. From XRD, SEM and HRTEM analysis, the average size of Sb:SnO2 nanoparticles were found decreased than the SnO2 nanoparticles. EDX analysis indicated the presence of tin, antimony and oxygen elements in the structure of nanoparticles. The presence of functional groups responsible for the formation of nanoparticles was identified by FTIR spectra. Bandgap of SnO2 and Sb:SnO2 nanoparticles was found to be 3.67 eV and 3.47 eV respectively. The sensitivity of SnO2 and Sb:SnO2 nanoparticles at the optimized operating temperature was found as 18.32% and 35% at 1000 ppm CO2 gas concentration
Effect of Wind Tunnel Model Blockage on Aerodynamic Characteristics at Transonic Speeds
No full textMeasurement of aerodynamic forces and moments acting
on models of aerospace vehicles is one of the most frequently used applications of wind tunnels. Although validated computational fluid dynamics (CFD) tools have largely obviated the need for wind tunnel tests during the development phase of an aerospace vehicle, verification of overall aerodynamic characteristics of the final configuration based on wind tunnel tests is essential for generating the aerodynamic database and reliability of aerodynamic design. The greatest deviations between experimental and CFD results are generally at transonic Mach numbers because of the complexities associated with CFD modeling of wall-interference effects, highly unsteady flows
involving shock-wave and boundary-layer interactions, etc. Factors such as elastic deflection of the model and influence of the support system also contribute to such difficulties
Aircraft Parameter Estimation using Feedforward Neural Networks with Lyapunov Stability Analysis
No full textAerodynamic parameter estimation is critical in the aviation sector, especially in design and development programs of defense-military aircraft. In this paper, new results of the application of Artificial Neural Networks (ANN) to the field of aircraft parameter estimation are presented. The performances of Feedforward Neural Network (FFNN) with Backpropagation and FFNN with Backpropagation using Recursive Least Square (RLS) are investigated for aerodynamic parameter estimation. The methods are validated on flight data simulated using MATLAB implementations. The normalized Lyapunov energy functional has been used to derive the convergence conditions for both the ANN-based estimation algorithms. The estimation results are compared on the basis of performance metrics and computation time. The performance of FFNN-RLS has been observed to be approximately 10% better than FFNN-BPN. Simulation results from both algorithms have been found to be highly satisfactory and pave the way for further applications to real flight test data
Improved evolutionary spectrum estimation using short time analytic discrete cosine transform with modified group delay
No full textIn this paper, a novel evolutionary spectrum (ES) estimator using short time analytic discrete cosine transform (STADCT) along with modified group delay (MGD) called as STADCTGD. The new STADCT has the desired properties of DCT like, twice the frequency resolution and reduced leakage in contrast to that of short time Fourier transform (STFT). The MGD retains the frequency resolution of the non smoothing window by reducing its Gibbs ripple. Thus the proposed STADCTGD exhibits improved performance as compared to that of existing ES estimator based on STFT and MGD. The performance of the proposed method is evaluated for signals like frequency shift keying, linear chirp, random process varying with time and non-stationary sinusoidal chirp. The results show that the new estimator has significantly improved frequency resolution, reduced leakage resulting in better detectability and noise robust compared to those of existing methods