Papers by Author: Yong Xin Li

Abstract: The traditional design method of machine tool column easily leads to material redundancy and it is difficult to achieve the best structural efficiency. A bionic method is proposed, bamboo was used as the biological archetype, to design the column structure of an extra-heavy duty CNC boring and milling machine. The macroscopical and microscopic structural characteristic and the mechanical property of the bamboo are analyzed, and the intrinsic relationship between the microstructure and mechanical properties is obtained. The column is designed as cylindrical structure firstly, and the relationship between the number of transverse ribs and the whole bending deformation is ascertained. The transverse ribs are designed for cylindrical structure .By evolving the cylindrical member, A, B two kinds of bionic column are designed and compared. The specific stiffness of B type structure is increased 10.9% and its overall performance is better than the A. So the B scheme is selected as the final bionic structure of the column.

Abstract: Traditional orthogonal pattern is ordinarily employed in stiffener configurations of plates in engineering. Layout optimization design of the stiffeners can realize the win-win situation of structure lightweight and bearing property. The existing methods generally transform the challenge into strengthening regional distribution, and the resulting vague regions need identification by post-processing technology. Structure similarity exists between dicotyledonous venation pattern and irregular stiffener distribution. The paper extracted some mechanical factors from the topology regularity and morphogenesis theory of dicotyledonous venation, and static bionic mechanical model was constructed for bionic rib pattern. A new venation growth method with hierarchical veins was proposed based on it. Then typical plate example was designed for proper stiffener distribution, and compared through static experiment.

Abstract: To remove the redundant points of image background in SFS reconstructed surface, a novel approach which combines the advantages of polygon scan and intersection algorithm and improves contour extraction method is proposed. In one hand, according to the gray scale level of pixels, the 3D profile of object is reconstructed by Shape from Shading method. In the other hand, firstly, the image is transformed into binary image through single-threshold segmentation method, the defects in image are remedied by morphological method, and the 2D contour of image is extracted through differential operator method; secondly, the image is divided into two parts using the polygon scan and intersection algorithm, that is the objective region and the background region; finally, the redundant points of image background in SFS reconstructed surface are removed through the fusing of 3D profile and 2D contour. Experiments shown that the proposed method can effectively remove the redundant points of SFS reconstructed surface, and it not only ensure the shape precision of SFS reconstructed surface, but also improve the universal of Shape from Shading technique.

Abstract: A new reinforcement distribution design method inspired by venation configuration is discussed in the paper. Learned from dicotyledonous venation, venation growing algorithm is proposed, minimization of strain energy and shear stress determine growth direction of the mainveins and subveins respectively. Vectorial equilibrium equation is used to calculate vein widths and adjust the orientation of vein cells slightly. Sensitivity number is used to measure the change in strain energy and shear stress when a vein cell grows, necessary equations are derived for bending Kirchhoffs plate. Several examples are design for venation-like rib distribution. The resultant rib layout by VGA is applicable and effective.

Abstract: This paper concerns a venation-like design method of rib layout and its application on some plates subjected to bending loads. Main topological characters of dicotyledonous venation and two determinative mechanical parameters in leaf venation morphogenesis theories are extracted, on the basis of those elicitations, a venation growing algorithm is proposed as an attempt at the proper layout of ribs in plate. Energy criterion and shear stress is specified as the factor orienting mainvein and subveins respectively. Vectorial equation equilibrium is used in reorganization to calculate widths and adjust vein cells slightly. Finite element method functions as background technique, under which several simple-shaped plates under bending loads are designed by venation growing algorithm. The resultant venation-like ribs offer multi-balanced improvements.

Abstract: This paper concerns biomimetic exploration of the leaf rib layout problem. Biological venation of organisms is observed to be similar to reinforced plate/shell systems. Similarity analysis makes it clear that dicotyledonous leaves are an ideal research subject. In this paper, global and local regularities are summarized and existing theories on venation morphogenesis are discussed and compared. An energy hypothesis is proposed to cater for interdisciplinary applications. A venation growing model was then used to construct a two-dimensional reinforcement layout model. The biomechanical expressions developed can be an alternative to describe rib-in-plate or fibre-in-composite materials.

Abstract: The FE modeling of complex trunk structure often needs shell and solid elements. Different commercial software adopts different shell-solid coupling techniques. A simple, robust method has been demonstrated for shell–solid coupling by fictitious perpendicular shell. Systemic study on the method is performed through the FE analysis of T-trunk model to ensure the displacement compatibility and stress equilibrium. Modal analysis of gearbox is executed to observe the reliability and efficiency of the coupling method. Parametrical conclusions and practical suggestions are presented finally.

Abstract: . Excitation force produced during gear mating of power transmission system induces vibration to the gearbox. Resonance occurs when excitation force frequency coincides to one of the natural frequencies of the gearbox which will bring not only sudden and unexpected vibration but also potential destruction to the gearbox. Natural frequency is determined by mass and stiffness of gearbox. These two determiners rely on sizes of the parts of the gearbox. That means natural frequency can be shifted by varying the sizes to prevent resonance. To demonstrate this, in this paper, the two stage parallel shaft gearbox modeled by shell-solid elements has been considered. The modal analysis and the real eigenvalue sensitivity analysis have been performed, in MSC. NASTRAN. The sensitivity coefficient and frequency spectrum at particular thickness of gearbox part show the effect on shifting the mode frequency.