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.

Compression behavior of NbC under nonhydrostatic conditions to 57 GPa

Abstract: The analysis of the diffraction data under nonhydrostatic stress condition created in a diamond anvil cell suggests that the compressive strength of NbC crystallites is at least 24 ± 4 GPa at a confining pressure of 57 ± 0.5 GPa. When using Al as a pressure transmitting medium in the diamond anvil cell pressure conditions become nearly hydrostatic. The bulk modulus derived from the compression data under quasi-hydrostatic pressure condition gives K 0 = 274 ± 3 GPa when fixing K 0 ′ = 4 . This value agrees well with the value obtained from the first-principles numerical calculations.

Comparative assessment of fatigue and fracture behaviour of cast and forged railway wheels

Abstract: A comparative evaluation of fatigue and fracture behaviour of commercially produced cast and forged rail wheels has been made using specimens extracted from various locations of the wheel quadrant. A systematic investigation in the web and rim regions of the wheel quadrant with various notch orientations showed that the forged material exhibited a better intrinsic resistance to fatigue crack growth than the cast material. Since linear elastic fracture mechanics (LEFM) based fracture toughness could not be validated for both the cast and forged wheel material, elastic plastic fracture mechanics (EPFM) based characteristic fracture toughness was used. Results showed that fracture resistance of the forged material is superior to that of the cast material. Cast wheel specimens exhibited unstable crack extension in comparison to substantial stable tearing in forged specimens. Microstructural and fractographic analyses showed that the cast wheel material contained large amounts of inclusions. The poor fracture resistance of cast wheel material is therefore attributed to the inferior material quality.

Relaminarization on Swept Leading Edges Under High-Lift Conditions

Abstract: Detailed experiments were made to gain an improved understanding of relaminarization on swept wings under high-lift conditions. Two swept wings with different airfoil sections and flaps were tested, and measurements were made consisting of surface-pressure distributions13; and wall shear-stress fluctuations in the leading-edge zone. Measurements were made at a chord Reynolds number of 1.3 x 106 with wing-sweep angles of 45 and 60 deg and model incidence varied in the range of 3 to 18 deg in discrete steps. Following the attachment-line transition, the turbulent boundary layer relaminarized under certain13; conditions due to the acceleration around the wing's leading edge. Broad features of relaminarization and subsequent retransition are discussed based on wall shear-stressfluctuation data. The present dataset shows that relaminarization is likely if the maximum value of13; the acceleration parameter K, (evaluated along the external inviscid streamline) is greater than about 3 x 10-6, in agreement with earlier findings. Much higher maximum values of IC, result in significant reduction of intermittency during relaminarization. After relaminarization, the boundary layer retransitions across a separation bubble. Characteristics of the post relaminarization separation bubbles are shown to be similar to those of bubbles occurring in more pristine13; laminar boundary layers.