Modal couping effects in the free vibration of elastically interconnected beams

The problem of free vibration of a uniform beam elastically interconnected to a cantilevered beam, representing an idealized launch vehicle aeroelastic model in a wind tunnel, is studied. With elementary beam theory modelling, numerical results are obtained for the frequencies, mode shapes and the generalized modal mass of this elastically cou pled13; system, for a range of values of the spring constants and cantilevered beam stiffness and inertia values. The study shows that when the linear springs are supported at the nodal points corresponding to the first free-free beam mode, the modal interaction comes primarily from the rotational spring stiffness. The effect of the linear spring stiffness on the higher model modes is also found to be marginal. However, the rotational stiffness has a significant effect on all the predominantly model modes as it couples the model13; deformations and the support rod deformations. The study also shows that though the variations in the stiffness or the inertia values of the cantilever beam affect only the13; predominantly cantilever modes, these variations become important because of the fact that the cantilevered support rod frequencies may come close to, or even cross over, the13; predominantly model mode frequencies. The results also bring out the fact that shifting of the support points away from the first mode nodal points has a maximum effect only on the first model mode

Analysis of axisymmetric laminated composite shells subjected to asymmetric loading

A finite element formulation for the static analysis of a laminated composite shell of revolution with general meridional curvature, subjected to asymmetric loading, is presented. The analysis uses an axisymmetric laminated shell element where the shell geometry is satisfactorily represented; higher order polynomial approximations are used for the displacement fields. The asymmetric loading problem is handled through a Fourier series representation of the applied loads and the resultant displacements. Solutions are presented for typical aerospace shell structures like a composite cone and a tangent ogive shell subjected to wind loads

Work, Culture and Sociality in the Indian Information Technology (IT) Industry: A Sociological Study

This report presents the key findings of a sociological study of the Indian information technology workforce that was carried out over a period of more than two years, between November 2003 and March 2006, in Bangalore and in three countries in Europe. The objective of the research project, entitled ‘Indian IT Professionals in India and Europe: Work, Culture, and Transnationalism’, was to document the social and cultural transformations that have been set in motion by the rapid growth of the IT and ITES industries in India, and through this to shed some light on wider processes of globalisation. The study focused on the creation of the IT workforce; the new forms of work, employment, organisation, and management, and the new cultures of work that have emerged in this industry, and on the transformations in lifestyle, sociality and identity that are taking place within this new global workforce

LCA Loading-Critical Load Cases For Wing Design

Loading Is An Important Phase Of The Structural Analysis And Design Cycle . In This Phase, Various Loads Acting On The Aircraft During Its Operation Are Simulated On The Structural Model, And The Internal Stresses Evaluated . In This Report, The Procedure For Structural Loading Of Lca Using Elfini Is Described . The Mass Cases, Flight Points And Load Envelopes Used For Loading Are Listed . The Critical Load Cases Selected For Using Structural Optimisation Are Presented Along With Justification 'For The Selection

Studies on the effects of flexibility in PSLV using aeroelastic models (A project proposal to VSSC, Trivandrum)

This document is a project proposal for undertaking studies on the interaction between aerodynamic loads and vehicle flexibility in PSLV using aeroelastic model testing. A 1/80th scale instrumented aeroelastic model of PSLV would be designed and tested in the 1.2 m trisonic wind tunnel to determine its divergence characteristics and shift of CP due to flexibility effects

Experimental flutter testing of Prithvi models

This is the Project proposal for the experimental flutter testing of Prithvi missile models

Review of Launch Vehicle Related Aeroelastic Instability Studies at HAL

Modern launch vehicles are long slender bodies with high flexibility and hence are prone to aeroelastic instabilities during their flight. These instabilities may adversely affect the performance of the vehicle or may even cause its failure, It is therefore necessary that a rigourous investigation of the aeroelastic behaviour of the vehicle is done at the design stage itself to ensure that the vehicle is free from such instabilities during its atmospheric flight, Important among the instabilities that a launch vehicle may experience are response to ground wind loads, divergence,flutter 06 control surfaces and panels, buffeting, coupled oscillations and fuel sloshing, Because of the complex nature of the aerodynamic input forces and aerodynamic-elastic-inertial interactions involved in most of these phenomena, it is often difficult and at times almost impossible to predict accurately the behaviour of the flight vehicle through theoretical means, Hence the designer has to take recourse to experimental means involving design and testing of aeroelastically scaled models, In this technique an aeroelastic model in a suitable wind tunnel is used as a mechanical analog of the mathematically complex problem requiring solution, The model in the wind tunnel first generates the correct aerodynamic input forces, and the measured response of the model to these input forces is then used to predict the response of the actual vehicle using appropriate scaling laws, The importance of scaled models in the study of aeroelastic problems of launch vehicles is amply demonstrated by the work done in this direction at the aerospace research Laboratories of NASA and elsewhere, With the importance of aeroelastic problems in the design of aerospace vehicles in mind, the Structures Division of the Laboratory, with active support from the Aerodynamic Division* initiated work on aeroelastic model studies in the early 1970's, mainly to understand the technique of aeroelastic model design and fabrication and to gain experience in aeroelastic testing. Early works in this direction were related to aircraft, involving design and testing of flutter models of typical aircraft wings (Ref.1&2).The know-how gained out of these studies was thus very useful while undertaking studies related to aeroelastic problems of launch vehicles for the ISRO in the early 1970°s, This paper gives a brief review of the past and current aeroelastic studies at NAL on Satellite Launch Vehicles SLV3, ASLV and PSLV developed/being developed by the ISRO

Transonic Buffet Testing of the PSLV Models - II: Modified Design & analysis

This report presents the modified design and analysis of the PSLV aeroelastic model, The changes in the model geometric scale and some deign parameters, result in changes in the model stiffness and mass scale ratios. Based on these modified values a new deigg is worked out which meets the design criterion. The support system for the model is designed such that_ it has minimum inter, Fference with basic model behaviour." The heat shield portion of the model is stiffened artifically to improve handling and local buckling propertie

Tests on Redux Bonded Sandwich Specimens

Tests have been performed, in accordance with ASTM specifications, on sandwich specimens bonded with Redux adhesives with a view to evaluate the performance of the adhesives. In this report, details of the tests conducted and the conclusions drawn from this study are given