Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties.

Abstract: Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings.

Laves Phase Control in Inconel 718 Weldments

Abstract: The detrimental laves formation in fusion zone during welding of Inconel 718 is controlled with compound current pulsing technique along with helium shielding gas. Also solid solution filler wire is used to minimize the niobium segregation. Welds were produced in 2mm thick sheets by GTA welding process and subjected to the characterization techniques. The results show, refined fusion zone microstructure, reduced amount of laves phase, minimum niobium segregation and softer fusion zone in the as welded condition.

Analysis of the nonlinear vibrations of unsymmetrically laminated composite beams

Abstract: Large-amplitude free vibrations of unsymmetrically laminated beams using von Karman large deflection theory are investigated herein. One-dimensional Finite elements based on classical lamination theory, first-order shear-deformation theory, and higher-order shear-deformation theory having 8, 10, and 12 degrees of freedom per node, respectively, are developed.

Effect of microstructure and strength on the fracture behavior of AA2219 alloy

Abstract: The plane strain fracture toughness, K J I c and crack growth toughness in terms of the non-dimensional tearing modulus, TR of Al–Cu alloy were evaluated following the J-integral method. An empirical relation is proposed for estimating the fracture toughness from the tensile properties. The estimated fracture toughness values from the empirical relation are found to be in good agreement with the measured fracture data. The microstructural as well as strength variations in the subject alloy were examined through different aging treatments (viz., under aging (UA), natural aging (NA), peak aging (PA) and over aging (OA)). The microstructural observations in different aging conditions were made through transmission electron microscopy (TEM) to understand the type of phase or intermediate stages of the phase present (GP zones, θ″, θ′ or θ). Fracture toughness testing has been carried out on 14 mm thick compact tension (CT) specimens and estimated the crack extension by unloading compliance technique. It was noted that the yield strength increases and fracture toughness decreases with the increase in the degree of aging from NA to PA condition. On overaging the alloy to a yield strength level as that of UA, it was not possible to retain the UA level of fracture toughness. The highest crack growth toughness is exhibited by the NA temper. The fractography analysis revealed that the fracture mode was predominantly transgranular dimpled rupture. Fracture initiation occurred by void nucleation at the second phase particles. The differences in the fracture toughness of the alloy in different aging conditions were shown to be dependent on the differences in the matrix deformation behavior and the strength differential.