bluuebunny/crossref_metadata_2025 huggingface dataset:
Uma análise cognitiva do emprego de tecnologias disruptivas na diplomacia de defesa: paradoxo ou pragmatismo circunstancial? O caso do Projeto de Propulsão Hipersônica
Authors: Rezende Ricardo , Queiroz Fábio
Published: December 2023

O artigo explora elementos subjetivos que influenciam a postura do Estado na diplomacia de defesa, utilizando-se da Teoria Cognitiva para mapear os inputs dos ambientes operacional e psicológico e seus efeitos sobre as visões de mundo dos decisores. Buscou-se identificar como o Projeto Estratégico de Propulsão Hipersônica − PROPHIPER − do Comando da Aeronáutica pode contribuir para a criação da imagem de um Brasil em busca do desenvolvimento e da projeção de poder em nossa diplomacia de defesa a partir da perspectiva do Ministério das Relações Exteriores e do Ministério da Defesa, a fim de verificar se há contraste ou complementariedade entre os imperativos de defesa e as tradições diplomáticas brasileiras. Como resultado, as evidências apontam para a convergência de papéis entre as duas burocracias no emprego de tecnologias disruptivas, ao construírem imagens que se complementam e se alinham. Palavras-chave: diplomacia de defesa, teoria cognitiva, tecnologias disruptivas, propulsão hipersônica.
Philosophy and Approach for Qualification of Space Hardware, Data Handling System
Authors: Varna Prabhakara
Published: December 2023

Any system developed for a space application needs to be qualified separately. Its margins have to be demonstrated with respect to electrical, thermal and mechanical design. Generally, a dedicated qualification model is planned for space system prior to fabrication of the flight hardware. Hence, a standard system calls for one qualification model at the start of the programme. However, there are certain payload elements whose design changes from one mission to another. Approach for demonstration of the design margins for one such payload element, Base band data handling system is presented here.
Thermal Postbuckling Characteristics Of Angle-ply Laminated Truncated Circular Conical Shells
Authors: Patel B.P.
Published: December 2023

Here, the nonlinear thermoelastic pre- and post-buckling characteristics of angle-ply laminated composite conical shells subjected to uniform temperature rise are studied using semi-analytical finite element approach. The finite element formulation is based on first-order shear deformation theory and field consistency principle. The nonlinear governing equations, considering geometric nonlinearity based on von Karman’s assumption for moderately large deformation, are solved using Newton-Raphson iteration procedure coupled with displace- ment control method to trace the prebuckling followed by postbuckling equilibrium path. The presence of asymmetric perturbation in the form of small magnitude load spatially proportional to the linear buckling mode shape is assumed to initiate the bifurcation of the shell deformation. The study is carried out to highlight the influences of semi-cone angle, ply-angles, number of layers and number of circumferential waves on the nonlinear prebuckling/postbuckling thermoelastic response of the laminated circular conical shells. The participation of axisymmetric and asymmetric modes in the total response of the shells is brought out through the deformation shape analysis.
Aircraft Maintenance Management - An Analysis of Defect Trend for Maintenance of Aeroengine (Artouste III B)
Authors: Augustine B.S.M. , Joseph Stanley A.
Published: December 2023

Maintenance of Aeroengine plays a vital role in the Aircraft Maintenance Management. In this paper. an analysis of defect trend for maintenance of aeroengine (Artouste III B) has been carried out on premature withdrawals of ninety - one aeroengines (Artouste III B) fitted in Chetak / Cheetah helicopters under operation for a period of five years in the various parts of India. Based on the analysis, the trend of defects occurred has been established and the remedial measures are suggested to the manufacturer, overhaul agency and operators to prevent occurrence of such defects. Some of them are implemented in the form of mandatory modifications issued by Director General of Civil Aviation(DGCA) based on the Service Bulletins issued by the manufacturer.
Trends in Uav Platforms and Technologies
Authors: Krishnan P.S.
Published: December 2023

Unmanned Air Vehicles (UAVs) have developed into indispensable war fighting assets of modern battlefield. UAVs play a pivotal role in sharing and disseminating strategic information in a Network-centric war scenario. The fusion of the data obtained from different sensors/ payloads further helps enhance situational awareness and enables quicker sensor-to-shooter reactions. There is a marked shift in the importance given to the Unmanned Air Systems development world-wide with significant increases in budget allocations. From Micro Air Vehicles (MAVs) to Unmanned Combat Aircraft, each type of UAV plays a distinct role at the same time presenting unique technological challenges. The paper discusses the present state of, and future trends in, various UAV platforms as well as sensor payloads carried by them and also highlights challenges in the related technologies. It also describes the ongoing UAV programs and technology competence built up by DRDO.
Chandrayaan-1 : An Update
Authors: Annadurai M. , Alex T.K.
Published: December 2023

No Abstract
Generalization of Mvcci Approach for Lefm Problems Using Numerical Integration
Authors: Dattaguru B. , Loksingh K. , Palani G.S.
Published: December 2023

Modified Virtual Crack Closure Integral (MVCCI) has become a valuable tool for estimation of mixed-mode fracture parameters in Linear Elastic Fracture Mechanics (LEFM) problems. When finite elements with fewer nodes and using polynomial shape functions are employed at the crack tip for fracture analysis, the expressions for MVCCI can easily be derived and many times also be expressed in closed form. For higher order elements they become unwieldy and so a numerical integration scheme is proposed and this can be used with any type of element. The scheme requires a two-step numerical integration: one to evaluate nodal forces exerted by the solid below the crack extension line on the portion above and the second to evaluate Strain Energy Release Rates. This development makes the post-processing for fracture parameters easy and computationally economical for 3-dimensional fracture problems. The technique is used to estimate fracture parameters in certain practical problems using higher order elements and typical numerical results are presented.
The Space Transportation System in India : Present Scenario And Future Directions
Authors: Suresh B.N.
Published: December 2023

No Abstract
Effect of Operating Conditions on the Emission Characteristics Of an Annular Combustor
Authors: Mishra R.K. , Singh Kuldeep
Published: December 2023

Pollutant emissions from combustion processes have become of great public concern due to their impact on health and the environment. Recent growth in civil aviation and stationary gas turbines power plants is worsening the situation both at airport vicinity and in altitude. This has called for rapid changes both in the regulations and controlling gas turbine emissions and in the technologies used to meet these regulations. All these developments have been accompanied by continuous and increasing pressure on the combustion engineers to reduce pollutant emissions from all types of gas turbines while operating at very high levels of pressure and temperature. In this paper an effort is made to characterize an annular combustion chamber from emission point and effect of various operating conditions has been analyzed. The emission characteristics of combustor are very satisfied and are inline to that of contemporary combustors of same class. This study can lead to combustor modifications for bringing down the emission levels to meet the international regulations.
Vibration and Buckling Analysis of Nano-Scale Beams via Nonlocal Elasticity and Timoshenko Beam Theory : A Differential Quadrature Approach
Authors: Murmu T. , Pradhan S.C.
Published: December 2023

A single-elastic beam model is being developed based on Eringens nonlocal elasticity and Timoshenko beam theory. Nonlocal parameter takes into account the small scale effects in the analysis of nano-size structures. Derived herein is a decoupled sixth-order nonlocal governing differential equations for the frequency and stability analysis of nano-scale short beams. The effect of shear deformation is thereby included in the small scale analysis. A Differential Quadrature (DQ) approach is being applied and its elaborate method of solution is illustrated. The higher order DQ approach is found to be a good numerical technique for the convenient and rapid solution of the aforementioned nonlocal problems. Frequency and buckling results for various scale-based nonlocal parameters are shown. Effect of number of interpolation points on the accuracy of the results is also investigated. It is seen that there is a significant effect of aspect ratio and nonlocal parameter on the nonlocal frequency and buckling loads of nano-scale beams. Also, the present study could open up a new approach of solution technique for the analysis of nano-scale structures based on nonlocal Timoshenko theory.
Tensile, Fatigue and Impact Properties of the AA 2618/AL2 O3P Composites
Authors: Sakthivel A. , Palaninathan R. , Velmurugan R. , Raghothama Rao P.
Published: December 2023

In this paper, the tensile properties (at RT and 200°C), high cycle fatigue and impact behaviour of the 2618 aluminium alloy reinforced with 5% wt. of Al2O3 particles (AA 2618/Al2O3p/5P) and 10% wt. of Al2O3p particles (AA 2618/Al2O3p /10P) were studied. The Composites were prepared by two-step mixing of stir casting method followed by forging. A significant increase in tensile strength of the MMCs, with respect to the unreinforced alloys was evidenced by the tensile test while the elongation to fracture decreased. Tensile property at 200°C is higher than the unreinforced counterpart. The high cycle fatigue tests showed that fatigue life is comparable to the monolithic alloy. The SEM analysis of the fracture surfaces showed that the presence of secondary precipitates played a significant role in the mechanism of failure in composites by promoting void nucleation at the particle-matrix interfaces, interfacial decohesion and also the failure of the particles. The impact strength is reduced with respect to the unreinforced alloy.
Effect of Lubrication Pattern on the Performance of a Small Turbojet Engine
Authors: Mishra A.K. , Mishra R.K. , Gouda G.
Published: December 2023

A small turbojet engine has been designed for UAV application and is intended to operate at high altitude and high subsonic speed. The mist lubrication system adopted initially for bearing to support a rotor speed of about 30000 rpm has exhibited good performance under test bed condition but incurs oil starvation during altitude operation. The present paper evaluates the performance of a mist lubrication system during flight and its limitations and drawbacks. The paper also highlights the performance of a close-loop system at altitude operating conditions enabling the system to meet the flight goal. The effect of lubrication pattern on bearing performance has been studied during this exercise. The bearings are found to be cooler with respect to engine speed as well as with altitude when working with closed loop system within the operating range.
CFD Prediction of Ramjet Intake Characteristics at Angle of Attack
Authors: Saha Soumyajit , Sinha P.K. , Chakraborty Debasis
Published: December 2023

The characteristics of installed intakes of a ramjet engine at angle of attack are predicted numerically. Three dimensional Navier Stokes equations are solved alongwith k - ε turbulence model using commercial CFD software. The software was first validated for isolated intake and computed results match very well with theoretical results available in literature. Pressure recovery Vs. mass flow characteristics of four installed intakes placed in a rear location of a ramjet vehicle is evaluated at different angles of attack upto 6°. Intake performance matches reasonably well with experimental results. It has been observed that significant variation of intake performance exists between windward and leeward intakes. For higher angle of attack, the leeward intake move towards the subcritical operation faster and the intake flowfield is seen to interact with the corebody boundary layer causing significant spillage.
Finite Element Analysis of Laminated Composite Shells with Piezoelectric Elements
Authors: Kuriakose Bennet , Latheswary S. , Valsarajan K.V.
Published: December 2023

The concept of incorporating some degree of smartness or intelligence in a system is gaining wide acceptance for utilisation in a variety of practical applications from aircraft to medical diagnostics because of the capability of smart materials to execute specific functions intelligently in response to changes in environmental stimuli. In this paper, the effectiveness of a simple finite element model in ANSYS is established for analyzing laminated composite shells with piezoelectric elements under static and dynamic loading. The substrate in smart shell is discretised using SOLSH190 element and the piezoelectric layer is discretised using coupledfield element, SOLID5. The basic behaviour of a smart composite shell depends on the behaviour of substrate with the response reduced/controlled by the properties of smart materials used, which is predicted effectively by the present finite element model.
Novel Repair Scheme for the Edge Delaminated Composites
Authors: Saji D. , Pradhan S.C.
Published: December 2023

Edge delamination refers to those delaminations, which arise at the free edge of a laminate. Although edge delamination in advanced laminated composites is a well-documented phenomenon, the repair of edge delamination is still a gray area. This paper presents an effective novel repair approach to repair edge delamination. Special repair tools have been designed and fabricated for this purpose. It also highlights the fabrication of artificially edge delaminated Carbon Fiber Reinforced (CFRP) specimens. Repair strengths have been evaluated by compression tests and Ultrasonic C-scan is used for validation of the repair scheme. From the tests it has been observed that the repair scheme has no bearing on the location of edge delamination and stacking sequence.
New Approaches for Analysis of Jet Noise Data
Authors: N. Karthikeyan  , L. Venkatakrishnan
Published: December 2023

Despite the significant advances in Computational Aeroacoustics for predicting jet noise, there is still a considerable need for experimental data. However, traditional measures of the directivity of Overall Sound Pressure Levels or the spectral distribution of the acoustic energy yield limited understanding of the nature of the sources. There is hence a need to use different approaches to the analysis of jet acoustics, among them applications of statistical methods such as auto correlation, self-correlation etc to understand the noise sources. In this paper, the acoustic characteristics of supersonic and high subsonic jets from nozzles of different exit geometries are measured and analyzed using these methods. The results show that these statistical methods of analysis can reveal the presence of two distinct noise sources in the flow and are applicable to both subsonic and supersonic flows. The information can be used to determine the appropriate model for the data and is useful for forming new theories about the noise generation mechanism in turbulent jets.
Recent Advances in Vibro-Acoustics and Noise Control Of Aerospace Composite Structures
Authors: Gopal P. Mathur
Published: December 2023

Composite structures are widely used in a variety of industrial applications due to their excellent mechanical properties, such as high stiffness-to-weight ratio, etc. The same characteristics that impart excellent mechanical efficiency, however, also result in efficient transmission and radiation of acoustic noise, posing serious vibro-acoustical problems for a variety of engineering systems in which composite structures are used. The composite structures are efficient radiators of noise mainly due to excitation and propagation of supersonic bending and/or shear waves in the structures. Composite skin-stringer structures mostly support supersonic flexural or bending waves propagating in the laminated structure whereas noise radiation by sandwich structures is dominated by supersonic shear waves in the core. Noise control of composite structures presents a significant technical challenge as the main advantages afforded by these structures, such as low weight and high strength, must not be compromised by added treatments. Recently, research has also been conducted to improve attenuation of vibration and noise radiation from such structure using nano-technology. This paper presents state-of-the-art review of the vibro-acoustics and noise control technology for aerospace composite structures.
Vibration and Small Scale Effects of Skew Graphene Sheets Using Nonlocal Elasticity Theory
Authors: S.C. Pradhan
Published: December 2023

Nonlocal elasticity theory is a popularly growing technique for the realistic analysis of nano structures. In the present work nonlocal elasticity plate theory has been employed and vibration analyses of skew graphene sheets are carried out. Relevant governing differential equations are reformulated using the nonlocal differential constitutive relations suggested by Eringen. The equations of motion including the nonlocal theory are derived. All edges of the skew graphene sheets are assumed to be simply supported. Naviers approach has been employed to solve the governing differential equations. Bauers skew plate analysis has been extended to include the nonlocal elasticity plate theory. Vibration response of the skew graphene sheets is studied. Effects of the (i) size of the graphene sheets (ii) modes of vibration (iii) nonlocal parameter and (iv) skew angle of graphene sheet on nonlocal vibration frequencies are investigated. It has been observed that the vibration response of the skew graphene sheets are influenced significantly by the nonlocal parameter.
Estimation of Load on Control Lines of Ram Air Parachute Designed for Precise Delivery Using 9-Dof Model
Authors: Balraj Gupta  , Vipin Kumar  , Ravi Krishna  , S.C. Upadhyaya  , A.K. Ghosh
Published: December 2023

Controlled Aerial Delivery System (CADS) consists of Ram Air Parachute (RAP) Airborne Guidance Unit (AGU) and useful payload. AGU pulls the control lines attached to the control surfaces of RAP and provides required maneuverability to the system. Estimation of load on control lines is essential for design and development of Airborne Guidance Unit (AGU). This paper presents the mathematical methods of the estimation of load on control lines the results of which are validated by experiments. The mathematical estimate of the load on control lines was carried out by developing a model similar to the aircraft control surface hinge moment estimation. The mathematical model was incorporated in 9DOF model to arrive at real time load estimation on control lines during inflation and subsequent steady flight condition. Experimental results are obtained during flight trials by using load cells on control lines and current sensor on power line of actuators. The mathematical results are in good agreement with the experimental results. The load on control lines are within 6 to 8% of the suspended load.
Nonlinear Aerodynamic Modeling of Hansa-3 Aircraft Using Neural-Gauss-Newton Method
Authors: Rakesh Kumar
Published: December 2023

The paper presents the nonlinear longitudinal aerodynamic modeling using Neural-GaussNewton (NGN) method from real flight data of Hansa-3 aircraft. The NGN method is an algorithm that utilizes Feed Forward Neural Network and Gauss-Newton optimization to estimate the parameters and it does not require a priori postulation of mathematical model or solution of equations of motion. The Kirchhoff’s quasi-steady stall model was used to include the nonlinearity in the aerodynamic model used for parameter estimation. Before application to the flight data at high angles of attack, the method was validated on flight data at moderate angles of attack. The results obtained in terms of stall characteristics and aerodynamic parameters were encouraging and reasonably accurate to establish NGN as a method for modeling nonlinear aerodynamics using flight data at high angles of attack. The supremacy of NGN was established by comparing the NGN estimates to that of Maximum Likelihood.
Composite Airframes-Opportunities, Options and Issues
Authors: Upadhya A.R.
Published: December 2023

Worldwide, both in the Civil and Military Aircraft Industry, there is an increasing usage ofcomposites due to the inherent advantages they offer. However, even today, the total potentialof composites has not been realized as the designers are still conservative. Also, cost hasbecome a very important factor especially for civil aircraft. In order to realize the full potentialof these materials, extensive research is being conducted in several areas that include design,newer, faster and cost effective approaches to manufacturing, better understanding of damagetolerance and associated failure theories, crashworthiness behavior and the like. StructuralHealth monitoring has progressed significantly and could play a major role in the reductionof maintenance costs and prevention of catastrophic failures. This paper makes an effort toaddress the options, challenges and issues that are confronting the composite industry today.
Review of Technological Advances in High Temperature Overhead Line Composite Conductors
Authors: Seetharamu S. , Kumar R.K. , Sampathkumaran P. , N. Shivakumar Kunigal
Published: December 2023

ACSR (Aluminium Conductor Steel Reinforced) conductors consisting of pure aluminum wires helically stranded around a core of high strength galvanized steel core wires are widely used in overhead transmission line applications. While the steel wires provides the required strength, the outer aluminium serves as electricity conducting member. The thermal rating or ampacity of conductors is the maximum current that a circuit can carry within the temperature limits as dictated by the allowable conductor sag or by the annealing onset temperature of the conductor, whichever is lower. On a continuous basis, ACSR may be operated at temperatures up to 100°C without any significant change in the conductor’s physical properties. Above 100°C, aluminum wires loses tensile strength over time and becomes "fully annealed" giving rise to increased thermal expansion of the conductor; this causes excessive sagging reducing the clearance between the ground and the energized conductors.

While, the electric utilities are posed with increased challenges of production of additional capacities and building new transmission circuits to meet the ever growing demand and the high cost and environmental restrictions of constructing new lines, methods are being explored to increase their capacity with minimum changes in the existing towers. Replacement of the existing conductor with a advanced high temperature composite (HTC) conductors operating upto temperatures of 200°C with reduced sagging characteristics have been attempted and an increase in capacity of 30-80%, can be achieved through application of these composite conductors.

The advanced HTC conductors with varied combinations of core material and outer conducting wires are being tried so as to achieve wide ranging properties. In general, HTC conductors features the combinations of either soft aluminum wires with ultra high strength steel or temperature resistant aluminium with or fiber reinforced metal/polymer matrix composites as the core. Both the alumina fiber reinforced temperature resistant aluminium metal matrix composite and the carbon fiber reinforced high temperature polymer resin composite wires as the core material appears to have favorable applications. The comparative performance of the HTC depends on the degree to which both outer aluminum strand and reinforcing core’s physical properties are stable at high temperature and on the elastic, plastic, and thermal elongation of the combined HTC.

The summary of various developments realized in the area of composite conductors and their relative merits and demerits have been discussed in detail.
Emerging Trends in Composite and Advanced Composite Materials Technology for Oil and Gas Industry
Authors: Kumar Pushpendra , Mahavar J.T.
Published: December 2023

Composite and advanced composite materials are new age materials offering multiple benefits such as longer durability, lighter weight, high strength, tailor made properties etc. Lessons have been learnt from successful applications of composite and advanced composite materials and the results indicate that operators, designers and contractors are beginning to take a serious interest in their wide applications in Oil and Gas Industry. The most significant advances in the field of composite materials technology has been the use of glass-reinforced plastics (GRP) for pipelines and piping, structural applications for the top side secondary structures of offshore platforms and onshore installations. The introduction of carbon fibers has opened a new vista for composites applications in oil and gas industry particularly in deepwater operations such as drilling risers, production risers, umbilical, moorings etc. Numerous risers, mooring, pipeline, subsea and topside components made of polyester, titanium, glass/epoxy, and glass/carbon/epoxy materials are in the process of qualification for offshore use. These advanced composite material components have potential to extend capabilities of existing platform concept such as Semi submersibles, TLPs, FPSOs and SPARs. This paper presents the properties and advantages offered by composite and advanced composite materials, their current use and future potential applications in oil and gas industry.
Small Scale Effects and Vibration of Graphene Sheets with Various Boundry Conditions
Authors: Kumar A.K. , Pradhan S.C.
Published: December 2023

Elastic theory of graphene sheets is reformulated using the nonlocal differential constitutive relations of Eringen. The equations of motion of the nonlocal theories are derived. Levy’s approach has been employed to solve the governing differential equations for various boundary conditions. Nonlocal theories are employed to bring out the small scale effect of the nonlocal parameter on the natural frequencies of the graphene sheets. Present vibration results associated with various boundary conditions are in good agreement with those available in literature. Further, effects of (i) nonlocal parameter, (ii) size of the graphene sheets and (iii) boundary conditions on nondimensional vibration frequencies are investigated. The theoretical development as well as numerical solutions presented here in should serve as reference for nonlocal theories of nanoplates and nanoshells.
Unstable Aircraft Parameter Estimation Using Neural Partial Differentiation
Authors: Kuttieri R.A. , Sinha M.
Published: December 2023

An approach based on neural partial differentiation is suggested, to overcome the numerical problems faced by classical methods, for the parameter estimation of an aerodynamically unstable aircraft. Theoretical analysis of the neural modeling, the parameter estimation process, and the nature of the estimates pertaining to unstable aircraft dynamics using the neural partial differential method, are discussed. Equation for the relative standard deviation, which is equivalent to the Cramer-Rao bound in the method like output error approach, is derived using the neural partial differential method and verified through numerical simulation. The aerodynamic derivatives are derived for the simulated and real longitudinal flight data of an unstable aircraft, and the estimates obtained using the neural partial differentiation are compared with the classical methods such as the equation error and the output error methods. The parameter estimates from the simulated noisy data are also presented to assess and support the theoretical developments presented in this paper. The theoretical analysis and the results presented in this paper make the neural partial differential approach more reliable and widely applicable.
Qualification of Compressor Impeller for Aero-Engine Application
Authors: Ragupathy R. , K John Wg Cdr (Retd) Simon , Esakki Muthu M.
Published: December 2023

This paper presents the approach for qualification of indigenously developed compressor impeller for aero engine application. Indigenisation is understood to be the most important tool for effective technical empowerment of a developing nation. Indigenisation philosophy is adopted by several countries in various fields such as power, infrastructure, aerospace, military equipments and etc. Indigenous development fills the technical, financial and time frame gap between imports and ab-initio design and development. Hence, for a healthy technical growth of any developing nation, Indigenous development activities should go along with ab-initio design activities. Indigenous development has become an integral process of activities of Defence sectors due to its potential benefits. Indian defence imports stands at staggering 65 % of the total defence acquisition. In order to make the best use of indigenization opportunities in the defence sector, conservative figures would suggest an amount more than 100,000 crores. This gives an indication of the potential and benefits of indigenous development in defence sectors.

In this paper a methodology for indigenous development of a military turboshaft engine compressor impeller is discussed. This activity has enabled uninterrupted supply of the component and a substantial Foreign Exchange savings. This paper specifies the various tests conducted over the forging. It also brings out the results of cyclic spin test on the component for 22500 cycles as life substantiation, 15% and 22% over speed test as structural integrity substantiation and 150 hours type test on engine for quality and assembly substantiation.

This indigenous development procedure described in this paper can be readily extended to suitable critical aero engine component.
General Equation for Range and Height Loss in Toss Bombing by Fighter Aircraft
Authors: Singh Lakshman , Ali Khan Majid
Published: December 2023

Different methodologies are use for accurate hitting of target by fighter aircraft. For guided weapons it is very well co-ordinate by homing head of weapon and weapon control system,but for unguided weapon, its hitting probability totally depend on pilot skill and aircraft maneuvering. This technical note outline category of conventional weapon by their damage mechanism and different technique to release unguided bomb from aircraft on desired target. This technical note point out need of toss bombing and derive general equation for toss bombing with the help of Dalembert principle and differential equation and at last geometrically calculate the height loss of aircraft in toss bombing.
Translaminar Reinforcements in Fiber Composites
Authors: Song M.C. , Sankar B.V.
Published: December 2023

Translaminar reinforcements (TLR) are effective means of improving the interlaminar fracture toughness of laminated fiber composites. The three methods to provide such reinforcements are: stitching, z-pinning and three-dimensional weaving. Although TLR are effective in improving the interlaminar fracture toughness, there is an optimum amount of reinforcement that can be provided to a given laminated structure. Excessive reinforcement may weaken the laminate. On the other hand weak reinforcements could be detrimental as they could lead to lowering the stiffness of the structure as the crack propagates. In this paper we review some of the analytical, numerical and experimental methods used to understand the effectiveness of TLR.
Crush Behavior of Aluminum/Composite Hybrid Tubes under Quasi-Static Loading
Authors: Mallick P.K.
Published: December 2023

This paper presents a review of the crush behavior of aluminum/composite hybrid tubes which are produced by wrapping one or more composite layers on aluminum tubes. It also provides new experimental data on the effect of crush initiators on the crush behavior of aluminum/composite hybrid tubes. It is shown that the crush initiator can influence both the failure mode as well as the energy absorption of all three types of tubes.
Challenges in Development of Structural Repair Manuals for Composite Fuselage
Authors: Shesh Monal , Sastry Veluri V.S.R.S.
Published: December 2023

There is wide application of composite materials in commercial transport fuselage structure. With extensive usage of composite material systems there is requirement for incorporation of maintainability and repairability requirements of composite primary structure into the design. Such issues need to be addressed to meet regulatory requirements and ensure that life-cycle costs are competitive with current metallic structure. Development of Structural Repair Manual (SRM) needs to account for maintenance issues early in the design cycle and provide multiple repair options. Furthermore, proposed repair solution must have tradeoff between ease of installation, damage resistance/tolerance (repair frequency), and inspection burdens. To support SRM development analysis methods are developed to assess structural strength, repair life, residual strength in the presence of damage, and to evaluate repair design concepts. This paper summarizes the experiences in development of repair options for composite fuselage components due to complexities of material system and additional analysis requirements.
Experimental Study on Performance of Impact Damper For Various Mass Ratios
Authors: Vinayaravi R. , Kumaresan D. , Asraff A. K. , Muthukumar R.
Published: December 2023

Vibration plays a vital role in many structural elements. Excessive vibration can cause failure due to resonance and fatigue, malfunctioning of critical components, etc. Vibration can be controlled using passive, active and hybrid control systems. This paper presents the experimental studies carried out on the behaviour of impact dampers, which belong to the category of passive vibration control devices that are used to attenuate vibration of discrete and continuous systems. Impact damping is a technique for improving damping of a dynamic system by means of dissipation of energy due to collision of a free mass on the main mass.

Experimental studies are carried out for forced vibration conditions by giving sinusoidal varying forcing function to the cantilever beam system using an exciter system and the time/frequency response function is determined. Impact mass is placed at free end of cantilever beam and the system is given constant base excitation and the damping of the system is studied by varying the frequency. Experiments are conducted for various mass ratios with different impact mass materials and the results are compared with theoretical predictions.
Processing and Characterization of AA2618/Sicp Metal Matrix Composites by Stir Casting Method
Authors: Sakthivel A. , Palaninathan R. , Velmurugan R. , Raghothama Rao P.
Published: December 2023

The future performance requirements of aero-engines must have improved thrust to weight ratios, reduced SFC and reduced signatures. Current materials technology within aero engines will restrict the thermodynamic cycle improvements and thus new materials and manufacturing techniques must be developed if the predicted improvements in engine performance will be due to material technology. The potential of metal matrix composite (MMC) materials for significant improvement in performance over conventional alloys have been recognized widely. However, their manufacturing costs are still relatively high. A critical step in the processing of cast particle reinforced MMCs is the incorporation of the ceramic particles into the molten matrix alloy. Therefore, wettability of the reinforcement particle by the matrix alloy must be optimized even though some of the methods are expensive and complex and some are cheap and simple technique. In order to produce 2618/SiCp MMC with maximum yield, two types of mixing i.e. liquid state and semi-solid state mixings have been introduced in the stir casting process with the support of process parameters from literatures. The process parameters utilized in each trial and results obtained in these processes are also highlighted. The density, hardness and tensile properties obtained in both the mixing processes are discussed. The study is carried out to assess the behaviour of AA2618/SiCp MMC for the fabrication of compressor blade.
Nanocomposites for Aircraft Applications
Authors: Prabhakaran R.
Published: December 2023

The steady increase in jet fuel prices in recent years has accelerated the quest for greater economy in airline operations. While improvements in aerodynamic efficiency, engine fuel efficiency, etc., have been sought, lighter and stronger materials for aircraft structural components remain a very important goal. The percentage of advanced composites, utilizing carbon fibers, in modern aircraft has reached 50 percent. The trend now is to use nano reinforcements such as graphene and carbon nanotubes to further reduce the structural weight. Due to the difficulties in fabricating nanocomposites with a high enough volume fraction of nano reinforcement, the nano reinforcements are either added to the polymer matrix or grown on the carbon fibers. The nano reinforcements are multi-functional; thus, in addition to contributing strength, they contribute to other properties such as electrical conductivity which in turn enhances the lightning strike protection, electrostatic discharge, electromagnetic shielding, etc. This paper summarizes these aspects and also describes the applications of nanocomposites in aircraft interiors, brake components, aircraft repair, etc.
Estimation of Longitudinal and Lateral Aerodynamic Derivatives From Flight Data Using Maximum Likelihood Method
Authors: Kumar Rakesh , Ghosh A.K.
Published: December 2023

The paper presents the estimation of longitudinal and lateral (lateral-directional) aerodynamic derivatives from real flight data of Hansa-3 aircraft using Maximum Likelihood (ML) method. The application of the ML method to the flight data of an air vehicle requires the postulation of correct flight dynamic formulations having accurate description of aerodynamic model. The application of the ML method to the flight data with either the measurement noise or the process noise has been accepted as a standard approach for the estimation of the aircraft parameters. A large number of longitudinal and lateral flight data sets were gathered during the flight testing of Hansa-3 aircraft through the execution of controlled maneuvers using elevator and aileron/rudder control inputs respectively. The acquired flight data in compatible form generated for various control input forms has been analyzed during the estimation of aerodynamic derivatives using Maximum Likelihood method. The results obtained in terms of aerodynamic derivatives are reasonably accurate and have been presented in tabular and graphical form. The paper highlights the various factors affecting the estimation.
Geometric Characteristics of Simply Connected Planar Sections With Application to Airfoils
Authors: Toufik Zebbiche , Mohamed Boun-jad , Abderrazak Allali
Published: December 2023

The presented work is to develop a numerical computation program to determine the geometrical characteristics of arbitrary simply connected planar sections and applications to airfoils. In the literature, there are exact analytical solutions only for some simple geometry such as circular, rectangular and elliptical sections. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. The used method is to subdivide the section in the infinitesimal triangular section with a single observer within the area having a suitable position. The characteristics of any triangle, given by the positions of these three nodes are known in the literature. Using the principle of compound surfaces, one can determine the geometric characteristics of the airfoil surface. The analytic function of the airfoil boundary is obtained by using the cubic spline interpolation because the airfoil is given in the form of tabulated points. An error estimation is done to determine the accuracy of the numerical computation.
Developlment of a Thermo-Chemical Non-Equilibrium Solver for Weakly Ionized Hypersonic Flowfields
Authors: Balasubramanian R. , Anandhanarayanan K.
Published: December 2023

A three dimensional solver for numerical simulation of weakly ionized hypersonic reactive air flows past high speed flight vehicles had been indigenously developed. The two-temperature, seven species, eighteen reactions, thermo-chemical non equilibrium, ionizing, air-chemistry model of Park is implemented in a compressible viscous code CERANS and solved in the finite volume framework. The energy relaxation is addressed by a conservation equation for the vibrational-electron-electronic energy of the gas mixture resulting in the evaluation of its vibrational temperature. The contribution of vibrational-electron-electronic energy of the reactive mixture is accounted in total energy equation as well as in the source terms of the relaxation model. The AUSM-PW+ numerical flux function has been used for modeling the convective fluxes and a central differencing approximation is used for modeling the diffusive fluxes. The code has been characterized for standard test cases involving weakly ionized hypersonic reactive thermo-chemical non equilibrium flows and results obtained are in good qualitative agreement with results available in open literature.
An Investigation of Thermal Postbuckling of Uniform Columns on Variable Winkler Foundation by Using Rayleigh-Ritz and Heuristic Formulations
Authors: Venkateshwarlu N. , Akella Suresh , Kishen Kumar Reddy T. , Venkateswara Rao G.
Published: December 2023

An investigation of the two different formulations, to predict the thermal buckling and postbuckling behavior of uniform hinged-hinged and clamped-clamped columns on the elastic variable Winkler foundations, is presented in this paper. The first one is the Rayleigh-Ritz and the second one is relatively simple heuristic formulation. Though the effect of the uniform Winkler foundation is thoroughly studied for the columns and other structural members, the variable Winkler foundation is not received much attention by the researchers. In the present investigation, two types of variable Winkler foundations, wherein the first and second terms of the foundations contain a constant and the variable parts, which varies with two types of sine functions, are considered. It is shown that the expressions obtained from the two formulations, for the ratios of the thermal postbuckling to the buckling load parameters are, not only the same but also validate the results, for the specified values of the central deflection and foundation stiffness parameters. A comprehensive set of numerical results are presented in this investigation, to obtain the thermal postbuckling behavior of uniform hinged-hinged and clamped-clamped columns on the variable Winkler foundations.
Microgravity
Authors: Kumar Awaneesh , Singh Kushal
Published: December 2023

This project in its present form is the result of the question "Why Astronauts go to Space?" the initial idea was to find out the reason behind the same. After doing some research works finally the conclusion was that the astronauts get microgravity region in space, so that many experimental works may be done there which are not possible on earth due to gravity. Then it was found out what exactly Microgravity is? How and why is it so beneficial that space shuttles are being launched? Then some newly found methods of achieving Microgravity inside the earth’s atmosphere have also been researched on. The results were Drop towers, Sounding rockets and Space shuttle. This project has some new areas of research included which would lead one to think beyond normal. Such as a unique way of achieving Microgravity on earth.
Effects of Stage Loading on Performance and Flow Field of a Centrifugal Compressor With Inlet Pressure Distortion
Authors: Sitaram N. , Govardhan M. , Murali K.V.
Published: December 2023

The paper presents experimental results on the effects of inlet total pressure distortion on the performance and flow field of a centrifugal compressor. The total pressure at the inlet is artificially distorted by means of a perforated sheet, which is supported by a support mesh. A total of eleven configurations, including clean inlet configuration, are tested. Performance measurements and impeller inlet and exit flow studies at three flow coefficients, one near design flow coefficient, one below design flow coefficient and one above design flow coefficient, are carried out. The present paper presents and discusses results at the three flow coefficients and the effects of stage loading on the distortion effects are presented. A new parameter, Distortion Index (DI) is introduced. As DI increases, the mass averaged total pressure at exit stations decreases. Distortion sector angle of 60° having the lowest total pressure is found to be the critical sector for circumferential distortion configurations. As the Distortion Correlation parameter, DC (60) increases, the mass averaged total pressure for circumferential distortion configuration decreases, except in the case of low flow coefficient where the mass averaged total pressure is nearly constant. DC (60) also increases with sector angle. The static pressure normalized with static pressure for clean inlet decreases as the distortion sector angle is increased. Distortion attenuates the static pressure as the flow passes through the vaneless diffuser. The attenuation increases with the distortion sector angle.
Thermodynamic Analysis of Vapor Compression Refrigeration System for Aircraft with Refrigerant R134a
Authors: Ramana Murthy K.V. , Ranganayakulu C. , Ashok Babu T.P.
Published: December 2023

The Environmental Control System (ECS) for a typical fighter aircraft is used for cabin cooling and pressurization, demisting operations, and for avionics cooling. Most of the passenger and fighter aircrafts use Bleed-Air Cycle for ECS. In this paper a new ECS called All Electric Environmental Control System (AEECS) is presented which works on Vapor Compression Refrigeration System using ram air as medium. It is called a power optimized system. The sizing of the system is based on the heat load calculations of the cabin and avionics for different flight conditions. A generalized software program is developed for evaluating system performance which includes key results regarding air compressor capacity, thermodynamic properties of refrigerants and Vapor Compression Refrigeration System. The AEECS is found to reduce the power requirement of the system to 80 kW compared to the Bleed Air Cycle ECS which requires a power of 0.8 MW to run the system. The results are presented in the form of graphs.
Preparation and Characterization of Low Cost Cu-Al-Be Shape Memory Alloy for Aerospace Applications
Authors: Ram Prabhu T.
Published: December 2023

Recently it has been found that a small addition of Beryllium (Be) widens the transformation temperature in Cu-Al based Shape Memory Alloys (SMA), that is particularly interesting in the industrial applications point of view. In this paper, the processing of Cu-Al-Be SMA by gravity die casting technology was described. The specially designed heat treatment procedure was designed to stabilize the SMA effect in this alloy. The DSC curve showed that this alloy has the transformation temperature in the range of 65°C to 120°C, and also exhibits the hysteresis behavior. Microstructure examinations confirmed the presence of lath martensite phases at room temperature. The bend test was used to prove the existence of the shape memory effect in this alloy.