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.

Thermally induced structural changes in Nomex fibres

Abstract: Thermally aged Nomex fibres manifest several residual effects viz. reduction in X-ray crystallinity, weight loss and deterioration in tensile characteristics. Surface damages in the form of longitudinal openings, holes, material deposits etc have also been observed. Based on the data from thermally exposed fibres, the time needed for states of zero tensile strength and modulus have been predicted.

Effects of thermo-mechanical cycling on the strain response of Ni–Ti–Cu shape memory alloy wire actuator

Abstract: The present paper deals with the strain response of Ni–Ti–Cu shape memory alloy (SMA) wire actuators on thermo-mechanical cycling (TMC). The characteristics of the actuators such as austenite (hot shape) remnant deformation and recovery strain undergo changes upon TMC. These changes are significant in the initial few cycles and the properties of SMA tend to reach a steady state on further cycling. It is believed that TMC induces defects in the microstructure and stabilizes the martensite/austenite phase. These in turn result in continuous change in strain response with the progress of TMC. It has been shown that for a stable strain response, the wire actuators need to be subjected to TMC at a higher stress than the working stress prior to application. Experiments were also conducted in order to minimize the number of TMC required for achieving stable strain response.

Intelligent fault diagnosis of synchronous generators

Abstract: A 3?kVA generator fault model is used to diagnose faults in a 5 kVA generator.The model is trained using 3 kVA generator data and 5 kVA generator (no-fault data).System-dependent dimensions are removed using nuisance attribute projection (NAP).Classification and regression tree (CART) is used as a back-end classifier with NAP.NAP improves the performance of the fault identification system. Condition based maintenance (CBM) requires continuous monitoring of mechanical/electrical signals and various operating conditions of the machine to provide maintenance decisions. However, for expensive complex systems (e.g. aerospace), inducing faults and capturing the intelligence about the system is not possible. This necessitates to have a small working model (SWM) to learn about faults and capture the intelligence about the system, and then scale up the fault models to monitor the condition of the complex/prototype system, without ever injecting faults in the prototype system. We refer to this approach as scalable fault models.We check the effectiveness of the proposed approach using a 3 kVA synchronous generator as SWM and a 5 kVA synchronous generator as the prototype system. In this work, we identify and remove the system-dependent features using a nuisance attribute projection (NAP) algorithm to model a system-independent feature space to make the features robust across the two different capacity synchronous generators. The frequency domain statistical features are extracted from the current signals of the synchronous generators. Classification and regression tree (CART) is used as a back-end classifier. NAP improves the performance of the baseline system by 2.05%, 5.94%, and 9.55% for the R, Y, and B phase faults respectively.

Synthesis of NASICON—A Molecular Precursor-Based Approach

Abstract: Phosphosilicate molecular precursor for the synthesis of NASICON, natrium super ionic conductor, Na1+xZr2SixP3−xO12 (x = 1 and 2) has been devised and prepared by the hydrolysis of tetraethoxysilane (TEOS) employing sodium phosphate solution. The molecular precursor was reacted with Zr(OC3H7)4 in ethanol under solvolytic condition to yield nano precursor material of NASICON. This material was annealed at high temperature to yield phase-pure NASICON. The molecular precursor was characterized using 31P NMR, FTIR spectral data, powder XRD pattern and TG/DTA studies. The structure of the molecular precursor was deduced from the powder XRD data, which indicates the presence of edge sharing tetrahedral arrangement of −O−Si−O−P−O−Si− chain. The NASICON precursor material was characterized using TG/DTA, FTIR, TEM, SEM, MAS 31P NMR and XRD. The conductivity of the synthesized NASICON material was measured using the pellet annealed at 900 °C and was found to be 5.5 x10−3 S cm−1. The details on the preliminary inves...