Sumit Singhal loves modern architecture. He comes from a family of builders who have built more than 20 projects in the last ten years near Delhi in India. He has recently started writing about the architectural projects that catch his imagination.
The Architecture of the Dragonfly Wing in London, UK by Maria Mingallon
April 13th, 2013 by Sumit Singhal
Article source: Maria Mingallon
An optimal natural construction, built by a complex patterning process, developed through evolution as a response to force flows and material organization.
Being the dragonfly wing a highly dynamic structure, vibration studies were necessary to obtain realistic deformation patterns and thus, understand its structural behaviour. Ten vibration modes were extracted from the modal analysis performed in GSA. Our eyes have difficulties distinguishing the third, fourth and fifth vibration modes (which occur almost simultaneously), due to the high frequencies exhibited. In our case, slow motion pictures featuring the real flight of the dragonfly, allowed us to identify up to the third mode of vibration by comparison with that calculated in the analysis.
The outcome images featuring the different modes of vibration of the wing illustrate the correlation described earlier between the geometrical patterns and the different degrees of flexibility. The rectangular pattern found at the uppermost zone of the wing, is designed to withstand load perpendicular to the leading edge taken by the wing during flight, while corrugations help with resisting loads perpendicular to the plane of the wing.
A torsional wave at the trailing edge can be observed throughout the different modes; this occurs due to the tendency of the elements closer to the wing’s tip, to twist ahead of those nearer to the base, creating a torsional wave. Located at the leading edge the nodus acts as the reinforcement and the shock absorber. The nodus copes with combined torsion and bending stress concentrations at the junction of the rigid concave ante-nodal and the torsionally compliant post-nodal spars.
The concentration of stresses and bending moments must have imposed strong selection pressure in the development of the nodus, which combines a stress absorbing strip of soft cuticle with strong, three dimensional cross bars across the entire spar between the costal margin and the leading edge. The deformed modal shapes demonstrate that the pentagonal-hexagonal pattern is designed to deform and thus, provide the thrust necessary to maintain the dragonfly in the air. The 120° angle present in these geometries, allows for the polygons to reorganise from being in a single plane to form a concave surface, utilising much less energy than that of the rectangular pattern.
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