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.

Synthesis, Characterization, Curing and Shape Memory Properties of Epoxy‐Polyether System

Abstract: Epoxy resins were cured by an amine telechelic poly(tetramethylene oxide) (PTMO) The telechelic amine was synthesized from hydroxy telechelic PTMO and was characterized The kinetics of curing of epoxy monomer by the polyether amine was studied in detail by differential scanning calorimetry (DSC) and rheology to optimize the cure conditions The cured epoxy system exhibited shape memory properties where PTMO served as the switching segment Molar ratios of the epoxy monomer and the amine were varied to get polymers with different compositions The developed polymers were analyzed by DSC, X‐ray diffraction, and Dynamic Mechanical Thermal (DMTA) analyses Shape memory property was evaluated by bending tests As the concentration of epoxy resin increased, the transition temperature (Ttrans) increased The tensile strength and % elongation also increased with epoxy resin‐content The extent of shape recovery increased with PTMO‐content with a minor penalty in recovery time The polymer with the maximum PTMO‐

Effect of Heat Input on Evolution of Microstructure and Tensile Properties of Gas Tungsten Constricted Arc (GTCA) Welded Inconel 718 Alloy Sheets

Abstract: The significant effect of heat input on the microstructural characteristics and tensile properties of 2-mm-thick Inconel 718 alloy sheets joined by gas tungsten constricted arc welding process was investigated systematically. It involves the application of magnetic arc constriction technique to solve the heat input-related metallurgical problems in gas tungsten arc welding of Inconel 718 alloy such as segregation of Nb and laves phase evolution in weld metal region which drastically reduces the weld mechanical properties. Heat input range was used from 495 to 585 J/mm by varying Main Current from 60 to 80 A at distinct levels of 5 A. The average secondary dendrite arm spacing was increased from 6.31 to 8.92 μm, revealing the corresponding cooling rate between 2087 and 720 °C/s. Superior tensile properties were obtained at an optimum heat input of 518 J/mm. It exhibited 98.16 and 78% of base metal strength and ductility. It is attributed to the grain refinement in fusion zone microstructure and the evolution of lower amount of laves phase with finer and discrete morphology. The average size and volume fraction of laves phase for the current sample were 3.12 μm and 7.68%. The benefits of magnetic arc constriction and Delta Current pulsing were not achieved at higher heat input.

Spatial characteristics of aerosol physical properties over the northeastern parts of peninsular India

Abstract: . Measurements on aerosol spectral optical depths and near surface mass-size distributions made at several locations in the states of Andhra Pradesh, Orissa and Chattisgarh, constituting the northeastern part of the peninsular India during the ISRO-GBP land campaign-I show significant regional variations in aerosol physical properties. Higher spectral optical depths were observed in the coastal regions and over southern latitudes compared to interior continental regions and northern latitudes. The optical depths, size index "α" and the near surface aerosol mass concentrations indicate a relative abundance of nucleation mode aerosols in the northern latitudes, in contrast to the dominance of the accumulation mode aerosols at the eastern coastal and southern latitudes. The airmass pathways derived from the back trajectory analysis indicate that the higher aerosol population in the accumulation mode, and consequently the higher optical depths in the southern locations, could be due to the transport of aerosol from the polluted north Indian regions via the oceanic region over the Bay of Bengal, where significant particle growth is expected, increasing the population of accumulation mode aerosols over these regions.