| Stiffened plate structures have been used widely in many project fields due to their light weight,high strength and vibration/noise reduction.Their performance are dependent on the stiffener layout pattern to a great deal.The commonly used topology optimization method can only get a vague stiffener distribution area and the existing bionic optimization design researches can only solve limited engineering problems.Inspired by the morphogenesis mechanism of dicotyledonous venation,this paper is to develop a universally applicable and straightforward approach to provide the explicit layout design of stiffened plate/shell structures without complicated postprocessing.The current mechanical property study of the bionic stiffened plate structures usually focus on statics characteristic and fundamental frequency analysis,frequency response under dynamic load is supplied in this paper.Besides,the sound insulation performances of the bionic stiffened plate such irregular complex structure is considered for further analysis of vibration and noise reduction.To prove that biomimetic method not only provide inspiration for mechanics,also provides new ideas for the acoustics.The major work of this thesis is showed as followed:The venation-inspired growth optimization method for stiffener layout design of plate structures was introduced.Based on the morphogenesis mechanism of dicotyledonous venation,the growth model and algorithm flow was established that the stiffeners extend by obeying a similar growth rule as the venation.Starting from the so called “seeds”,the stiffeners grow and branch off towards the direction that optimizes the structural performance.The growth and degeneration of the stiffeners are determined by elemental sensitivity numbers.the recommended key parameters were determined,including seeds position,the degeneration rate and convergence degree.Using this method,the typical venation layouts were simulated successfully to validate mechanism effective,such as pinnate leaf,palmate leaf and round leaf.The mechanics properties of the bionic stiffened plates obtained by this method were studied though three typical examples(unilateral clamped plate with concentrated load on edge,four corners clamped plate and adjacent edges clamped plate with concentrated load on center).Compared with the orthogonal stiffened plates and no-stiffened plates,the bionic stiffened plates show excellent statics and dynamics performance.Results show thatmaximum deformation of bionic stiffened plates under static load is 35.1%-58.7% lower than that of orthogonal stiffened plates;The low order natural frequencies increased to varying degrees,the fundamental frequency increased 23.2%-89.0%;maximum deformation under dynamic load reduced 28.4%-66.5%.The sound insulation performances of the bionic stiffened plates obtained by this method are studied also though three typical examples.The sound insulation frequency characteristic curve of typical monolayer limited homogeneous plate was analyzed and calculation model of the sound insulation was established by using the coupled boundary element and finite element method.Compared with the orthogonal stiffened plates and no-stiffened plates,the bionic stiffened plates show excellent sound insulation performances.That transmission loss of bionic stiffened plates under stiffness control area improved7.9-15.3dB than that of orthogonal stiffened plates;resonant frequencies moves to the higher frequency and minimum values increase;transmission loss under mass control area improved1.1-2.3dB.Using unilateral clamped plates as example,comparative experiments of stiffened panels with different configuration was conducted.Static testing system was designed to measure deflection.Natural frequencies were measured by hammering method;Reverberation ventricular-sound elimination box was designed to measure sound transmission loss.Comparison analysis between numerical examples and experiment results indicates that numerical calculation is efficient.Besides,the proposed venation-inspired bionic optimization method can be applied to the stiffener design to improve the structural static,dynamic mechanical properties and sound insulation property. |
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