Browsing by Author "Griffin, K. H."
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Item Open Access The aeroelastic behaviour and response to turbulence of a class of high performance tailless sailplanes.(1978-09) Banerjee, J. R.; Griffin, K. H.The symmetric flutter and response characteristics of a class of tailless .sailplanes-:are investigated combining rigid--body dynamics with elastic modes of deformation. The methods used are based on the normal mode approach through the use of finite element techniques and unsteady aerodynamic theories in two dimensional flow. The flutter speed and. aeroelastic modes are critically examined and the results are compared with those of a tailed sailplane. The flutter speed of the tailless sailplane is found to be low in comparison with those of orthodox layout and a parametric study is undertaken to locate-the reason for this; recommendations are made for improvements. A method is proposed for the analysis of the. short period oscillation characteristics of flexible aircraft allowing for the-effects of unsteady aerodynamics. - It is then applied to the type of tailless sailplane under investigation. The response to gusts and turbulence is evaluated using both statistical and discrete gust methods. Comments are made from the calculated results about the aeroelastic behaviour of tailless sailplanes in general. Computer programs developed for detailed aero-elastic calculations are presented.Item Open Access An assessment of certain methods of stress-analysis of rectangular multi-web box beams(College of Aeronautics, Cranfield, 1956-12) Griffin, K. H.The stress distribution in an unswept multi-web box under shear load applied at the centre of a rigid tip rib is examined, and compared with results obtained by a method which replaces the shear webs by a shear-carrying continuum. Continues ...Item Open Access The buckling in compression of panels with square top-hat section stringers(College of Aeronautics, Cranfield, 1949-06) Hemp, W. S.; Griffin, K. H.A simplified panel model is described, together with a number of assumptions about the mode of its bucking. The approach to the calculation of the buckling stress is by splitting the panel into a number of flat plates and treating these by the ordinary plate theory. Use of the boundary conditions between these plates leads to a relation between the buckling stress and the variables of the panel geometry. The results thus obtained are compared with two sets of recent experimental work; and an appendix is included to show the effect of initial panel irregularities on the experimental determination of buckling stresses.Item Open Access Buckling of corrugated core sandwich panels(1969-09-19) Patel, N. G.; Griffin, K. H.A computer program is developed to determine the buckling stress and deflections of symmetric corrugated core sandwich panels. In the program freedom for lateral deflections at core to face-plate junction is allowed for. Provision is also made to study the effect of variation of core bend radius. A range of test specimens using four basic core configurations is designed to assess the effect of core bend radius on the buckling stress of the panel. The computer program indicates that above a certain value of core bend radius there is a marked drop in the value of critical buckling stress and a change in buckling Mode. The values of deflections at core to face-plate junctions at low buckling wave-lengths are not reliable* Due to the limited range of the experimental work, it is not possible to draw any conclusions on the effect of core bend radius on the buckling stress. The method used for determining the experimental buckling load is somewhat subjective in application, and its accuracy is difficult to assess. In general, the experimental values of buckling stresses are 15% higher than those predicted by the computer program. These discrepancies are not large when dimensional and material property variations are considered and indicate that the computer results are giving the correct trend and are conservative. Recommendations are made for : (i) Investigation of the buckling deflections at low values of buckling wave-lengths for specimens with high face-plateto-core thickness ratio. (ii) A test programme covering a wider range of specimens than that covered by the test programme in this study. and (iii) Trying out the other two methods of determining the buckling load.Item Open Access Investigation of the structural interaction between the wing and body of a class of simple remotely piloted aircraft(Cranfield University, 1982-10) Ahn, D. M.; Griffin, K. H.Effects of various wing-body interaction design parameter variations on the structural behaviour of a small RPV have been investigated using the finite element method on an adhoc basis rather than a classical analytic approach. The method in use is based on the substructuring displacement method considering the body and the wing as two major substructures. The elastic coupling effect of wing stiffness on the body structural behaviour also examined. By comparing classical analysis methods to the present. investigation, comments are made upon the use of those methods in the design analysis of the RPV class of structure. From the calculated results, general guidelines on the structural wing-body interaction analysis or design of this class of vehicle have been proposed. A set of finite element programs have been developed for the present investigation, and relevant finite elements based on the displacement assumption have been formulated.