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Computational Modeling of the Elastic Property of Three-Dimensional Open Cell Foams

Nie Z., Lin Y., Tong Q.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1153--1165

EN

The work reports on the development of random three-dimensional Laguerre-Voronoi computational models for open cell foams. The proposed method can accurately generate foam models having randomly distributed parameter values. A three-dimensional model of ceramic foams having pre-selected cell volumes distribution with stochastic coordinates and orientations was created in the software package ANSYSTM. Different groups of finite element models were then generated using the developed foam modeling procedure. The size sensitivity study shows that each of foam specimens at least contains 125 LV-cells. The developed foam models were used to simulate the macroscopic elastic properties of open cell foams under uni-axial and bi-axial loading and were compared with the existing open cell foam models in the literature. In the high porosity regime, it is found that the elastic properties predicted by random Laguerre-Voronoi foam models are almost the same as those predicted by the perfect Kelvin foam models. In the low porosity regime the results of the present work deviate significantly from those of other models in the literature. The results presented here are generally in better agreement with experimental data than other models. Thus, the Laguerre-Voronoi foam models generated in this work are quite close to real foam topology and yields more accurate results than other open cell foam models.

2

Dynamic analysis and optimization of a bionic flapping-wing aircraft

Jin X., Zhou X., Tian P., Zhang L., Nie Z.

Engineering Transactions

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2016

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Vol. 64, iss. 2

181--196

EN

This research has been conducted for the purpose of developing bionic flapping-wing aircraft. In this paper, wings are regarded as flexible, and the response issues of wings under certain excitation functions are investigated. The research is based on preliminary studies about bionic flapping wings and aims to provide data references to aid the selection of electrical actuators and the design of driving mechanisms for bionic flapping-wing aircraft at a later stage. The dynamic analysis shows that the response functions adapt well to the flapping movements of the wings. However, there are mutational situations in the wing structure transformation which are bad for structural stability, and cause there to be too little lift force. Under such circumstances, the minimum norm of low-order vibration mode difference values is used as the optimization principle to conduct the structural optimization. The optimization results and the wing flutter test both show that the optimized wings can better avoid structural mutations and their response functions can also better meet the design requirements.

3

Application of dynamic speckle methods to study thermal denaturation of the albumin

Li X., Tai Y., Nie Z., Chen Q., Li L.

Optica Applicata

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2011

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Vol. 41, nr 3

581--591

EN

The process of the thermal denaturation of albumin was studied using dynamic speckle methods, which included the time history of speckle patterns (THSP), the THSP based on wavelet entropy (WE), speckle size measurement and the speckle pattern mean contrast techniques. In experiments, the dynamic speckle pattern sequences produced from the albumin colloid during heat denaturation were obtained using CCD camera. And then, using these dynamic speckle methods, the change of the movement properties of protein particles was analyzed during the heating process. All results show that the protein particles become bigger, their mean free path becomes shorter and the velocity of the Brownian movement becomes slower during the heating process. The experiments prove that dynamic speckle methods are useful tools to investigate the particles motion in solution.