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FROM:
Archa S. Lal and Jiss K. Abraham (Dept. of Civil Engineering, Saintgits College of Engineering, Kottayam, Kerala, India),
“Design of integrally stiffened shell structures”, International Research Journal of Engineering and Technology (IRJET), Vol. 4, No. 5, pp 1059-1062, May 2017
ABSTRACT: In launch vehicle structures, for withstanding buckling failures due to the compressive loads and external pressure, integrally stiffened shell structures (waffle and isogrid shell structures) are employed. This paper discusses about the design of cylindrical and conical shaped isogrid structures subjected to axial compression and the external pressure and the effect of variation of design parameters like height of the triangle, skin thickness, rib width, rib depth etc. on the buckling load capacity. First, theoretical computation of the buckling load factor has been carried out using design equations for isogrid structure. A near optimum configuration is arrived at, which results in minimum equivalent weight thickness and positive margins of safety. By using inhouse software FEAST, a parametric modeling tool has been developed for modeling isogrid and waffle shell structures. Static analysis, buckling analysis and free vibration analysis have been carried out for both structures using FEAST software. By comparing the results, isogrid structures have less static displacement and more buckling load factor when compared with waffle structure.
References listed at the end of the paper:
. [1] McDonnell Douglas Astronautics Co., “Isogrid Design Handbook”.MDC G4295A(Contract NASA 8-28619)), Feb, 1973.
. [2] Danial J Knighton, Delta Launch vehicle Isogrid Structure Nastran analysis,MC Donnell Douglas Astronautics Co,1970
. [3] B.Wang et al., “Numerically and experimentally predicted knockdown factors for stiffened shells unde axial compression.,”Science Direct ,2016 , pp.13-24
. [4] M.I Baig and T.Y.Yang.,”Buckling Analysis of Orthogonolly stiffened waffle cylinders”, J.Spacecraft, 1974, pp. 832-837.
. [5] G. Totaro., “Local buckling modelling of isogrid and anisogrid lattice cylindrical shells with triangular cells ”, Science Direct,2012,pp. 446-452.
. [6] W.Akl et al., “optimization of the static and dynamic characteristics of plates with isogrid stiffeners”,Scicence Direct,2008,pp. 513-523.
. [7] Kazuo Kunoo and T.Y Yang.,”Minimum Weight design of an orthogolnolly stiffened Waffle cylindrical shell with BucklingConstraints”,J.spacecraft,1976,Vol.13,No.3,Pp.1 37-143.
. [8] Romy Mathew et al.”Design studies of conical shells in launch vehicles.”IJIRAE,ISSN:2349-2163, 2015,Issue 4, Vol. 2
. [9] Vijay Thammisetty, Narasimha Reddy.,”Optimization of Isogrid Rib-Pattern on Mechanical Housing”, IJIRSET,2015,Vol.4, Issue 11,pp. 10929-19036
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