National Aerospace Laboratories

About: National Aerospace Laboratories is a facility organization based out in Bengaluru, India. It is known for research contribution in the topics: Coating & Corrosion. The organization has 1838 authors who have published 2349 publications receiving 36888 citations.

Sensitivity of polyvinylidene fluoride films to mechanical vibration modes and impact after optimizing stretching conditions

Abstract: The I²-phase of polyvinylidene fluoride (PVDF) is well known for its piezoelectric properties. PVDF films have been developed using solvent cast method. The films thus produced are in I±-phase. The I±-phase is transformed to piezoelectric I²-phase when the film is hot-stretched with various different stretching factors at various different temperatures. The films are then characterized in terms of their mechanical properties and surface morphological changes during the transformation from I±- to I²-phases by using X-ray diffraction, differential scanning calorimeter, Raman spectra, Infrared spectra, tensile testing, and scanning electron microscopy. The films showed increased crystallinity with stretching at temperature up to 80°C. The optimum conditions to achieve I²-phase have been discussed in detail. The fabricated PVDF sensors have been tested for free vibration and impact on plate structure, and its response is compared with conventional piezoelectric wafer type sensor. The resonant and antiresonant peaks in the frequency response of PVDF sensor match well with that of lead zirconate titanate wafer sensors. Effective piezoelectric properties and the variations in the frequency response spectra due to free vibration and impact loading conditions are reported. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers.

Evaluation of Data Association and Fusion13; Algorithms for Tracking in the Presence of13; Measurement Loss

Abstract: Tracking in multi sensor multi target (MSMT) scenario is a complex problem due to the uncertainties in the origin of observations. Solution to this problem requires appropriate gating and data association procedures to associate measurements with targets. A PC MATLAB program based on track-oriented approach is evaluated which uses nearest neighbour Kalman filter (NNKF) and probabilistic data association filter (PDAF) for tracking multiple targets from data of multiple sensors. For track-to-track fusion, state vector fusion philosophy is employed. The tracking performance in the presence of simulated track loss and recovery as well as in clutter is evaluated. During data loss PDAF performed better than NNKF. In the presence of mild clutter and sparse target scenarios, the NNKF and PDAF give similar performance.

Influence of zirconium doping on the growth of apatite and corrosion behavior of DLC-coated titanium alloy Ti–13Nb–13Zr

Abstract: Ti–13Nb–13Zr was coated with diamond-like carbon (DLC) and zirconium-doped DLC by plasma-enhanced chemical vapor deposition and sputtering. The corrosion current of the substrate is not affected after coating, and corrosion potential shifts towards nobler values in Hanks' solution. Electrochemical impedance spectroscopy studies show that Zr-DLC samples behave like an ideal capacitor. Field emission scanning electron microscopy (FESEM) images after 7 days of immersion show absence of apatite on DLC-coated sample and its presence on Zr-doped DLC, but to a lesser extent as compared with that on the uncoated substrate. XPS and Energy-dispersive X-ray spectroscopy (EDS) of samples immersed in Hanks' solution show presence of calcium, phosphorous and oxygen in hydroxide/phosphate form on the substrate and Zr-DLC. Copyright © 2013 John Wiley & Sons, Ltd.