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Institution

National Aerospace Laboratories

FacilityBengaluru, India
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.


Papers
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Journal ArticleDOI
TL;DR: In this paper, an experimental investigation into aero-acoustics of an annular aerospike nozzle of design Mach number (Md) of 2.0 has been carried out, and the results are presented.
Abstract: The work toward reusable single-stage-to-orbit launch-vehicle concepts has initiated several research activities toward a suitable nozzle design, which (unlike bell nozzles) is expected to perform optimally over the entire flight regime. Of these concepts, the annular aerospike nozzle and its variants, linear and truncated, are among the most promising. Given the concern over the intensity of acoustic loading during takeoff, it is vital to carry out a detailed aeroacoustic characterization of aerospike nozzles with special attention to overexpanded conditions, which are generally encountered during liftoff. In this work, an experimental investigation into aeroacoustics of an annular aerospike nozzle of design Mach number (Md) of 2.0 has been carried out, and the results are presented. The effect of truncation of the aerospike to 40 and 60% of the spike length on the acoustic field is also studied and compared with the full-length aerospike. Results show that, in the overexpansion regime, truncated conical aerospike nozzles have reduced acoustic (∼4–5 dB) levels until wake closure compared to the full-length aerospike and conventional convergent–divergent nozzle, all operating at identical conditions. This noise reduction is predominantly in the region upstream of the nozzle exit. At the peak radiation angle (∼150 deg from the jet upstream direction), the acoustic levels are almost same for all of the nozzles investigated in the present study.

16 citations

Journal ArticleDOI
TL;DR: In this article, four different cases of specimens with embedded gaps in plies at multiple locations are under consideration and the optical images of cut specimens both longitudinal and transverse of all four cases are used for creating 3-D finite element models with ply waviness to compare their behavior with baseline reference specimens.

16 citations

Journal ArticleDOI
TL;DR: In this article, a new approach for the computation of continuation diagrams is presented, which differs in principle from the usual approach of continuing the equilibrium points by considering one or more of the controls as continuation parameters and with the other controls held fixed.
Abstract: A new approach is presented for the computation of continuation diagrams. It differs in principle from the usual approach of continuing the equilibrium points by considering one or more of the controls as continuation parameters and with the other controls held fixed. The novel approach addresses the problem of Light dynamics from the pilot point of view by allowing all the controls to be freely determined. At the same time some of the states are so constrained that along the continuation curve a particular pilot trim condition is maintained.

16 citations

Journal ArticleDOI
TL;DR: In this article, as-deposited alloy plated at pH8 with DC contain only Co2+ and W6+ species, whereas that alloy at pH5 has significant amount of Co 0 and W 0 along with Co 2 and W 6+ species.
Abstract: Electrodeposition of Co–W alloy coatings has been carried out with DC and PC using gluconate bath at different pH. These coatings are characterized for their structure, morphology and chemical composition by XRD, FESEM, DSC and XPS. Alloy coatings plated at pH8 are crystalline, whereas coatings electrodeposited at pH5 are nanocrystalline in nature. XPS studies have demonstrated that as-deposited alloy plated at pH8 with DC contain only Co2+ and W6+ species, whereas that alloy plated at pH5 has significant amount of Co0 and W0 along with Co2+ and W6+ species. Again, Co2+ and W6+ are main species in all as-deposited PC plated alloys in both pH. Co0 concentration increases upon successive sputtering of all alloy coatings. In contrast, mainly W6+ species is detected in the following layers of all alloys plated with PC. Alloys plated at pH5 shows higher microhardness compared to their pH8 counterparts.

16 citations

Journal ArticleDOI
TL;DR: In this article, the effective properties and thermo-mechanical behavior of shape memory fiber (SMF) and shape memory polymer (SMP) composite laminates using micromechanical approaches based on the method of mixtures (MOM) and method of cells (MOC).
Abstract: The research work presents the modeling of effective properties and thermo-mechanical behavior of shape memory fiber (SMF) and shape memory polymer (SMP) composite laminates using micromechanical approaches based on the method of mixtures (MOM) and method of cells (MOC). The fiber is made of a nickel-titanium (Ni-Ti) shape memory alloy (SMA), while the matrix consists of a shape memory thermoset epoxy polymer (SMP). The use of an SMP matrix provides large strain compatibility with the SMA fiber, while being active at high temperatures without losing its elastic properties. Additionally, the SMP matrix is also able to produce similar pseudoelastic and shape memory effects, which are noticed in SMAs. In the analysis, a two step homogenization scheme is followed. In the first step the effective properties of each layer are determined via a micromechanics approach with iso-strain conditions. In the second step the effective properties of the SMF-SMP composite are computed making a thin plate theory assumption, which takes into account the transverse shear deformations. The possible elastic couplings for SMF-SMP laminates are discussed, and the laminate force and moment resultants are computed for various laminate configurations. The analysis takes into account the effects of phase transformations and the resulting change in the fiber-matrix modulus. The results have been compared by considering different fiber volume fractions, temperatures, fiber orientations, and lamina stacking sequences. The results show that adaptive SMA-SMP composites laminates can be developed that provide shape controllability via tunable laminate stiffnesses leading to optimal response. Furthermore, the work presents the necessary framework for a reliable and efficient analysis of SMA-SMP laminates for practical applications. The theory can be directly used in established plate and shell formulations of finite element analysis. Finally, the variations in force and moment resultants with respect to fiber orientations and stacking sequences are presented, which are useful to study the bending and buckling characteristics of active composites for shape control of adaptive structures. The work concludes that efficient adaptive laminate development for high performance composite applications, exhibiting large shape adaptivity, high stresses, and increased stiffness, are feasible as compared to SMA composites without active matrix. POLYM. COMPOS., 32:910-927, 2011. (C) 2011 Society of Plastics Engineers

16 citations


Authors

Showing all 1850 results

NameH-indexPapersCitations
Harish C. Barshilia462366825
K.S. Rajam42834765
Kozo Fujii394115845
Parthasarathi Bera391365329
R.P.S. Chakradhar361664423
T. N. Guru Row363095186
Takashi Ishikawa361545019
Henk A. P. Blom341685992
S. Ranganathan332115660
S.T. Aruna331014954
Arun M. Umarji332073582
Vinod K. Gaur33924003
Keisuke Asai313503914
K. J. Vinoy302403423
Gangan Prathap302413466
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202310
202216
2021143
2020100
201996
2018119