【作者】 张建；

【导师】 陈立明；

【作者基本信息】 重庆大学 ， 力学， 2018， 硕士

【摘要】 点阵圆柱壳结构以其轻质高强等特性广泛应用于航空航天等领域。近年来,随着轻量化吸能装置的迫切需求,点阵圆柱壳结构作为一种潜在的吸能构件引起了学者们的广泛关注。迄今为止,关于点阵圆柱壳结构静态力学性能的研究已经较为完善,然而有关它的动态变形和失效机制理解还不清晰,将梯度设计思想引入点阵圆柱壳结构的研究还未见报道。本文针对梯度点阵圆柱壳及夹芯圆柱壳结构在动态压溃下的力学性能从理论分析、数值模拟和实验验证等方面进行了系统研究。主要进行了以下几个方面的工作:首先,充分利用3D打印方法制备复杂微结构的优势,设计制备了ABS全三角点阵圆柱壳及夹芯圆柱壳结构。通过轴向压缩实验研究了其承载能力和吸能特性,观察到多种典型失效模式。研究表明,点阵夹芯圆柱壳结构的比吸能远高于点阵圆柱壳结构,蒙皮对芯层的约束作用能有效提高结构的承载能力和吸能性。此外,采用有限元软件ABAQUS对点阵圆柱壳结构的轴压过程进行了数值仿真,有限元模拟结果与实验结果吻合较好。其次,基于一维波理论,建立了拉伸主导型(全三角)和弯曲主导型(六边形)两种典型点阵圆柱壳的动态压溃平台应力预测模型,理论预测与有限元模拟结果吻合较好。进一步考虑了冲击速度和相对密度对其动态压溃性能的影响,揭示了其压溃变形机制。在此基础之上,研究了梯度大小和排列形式对点阵圆柱壳归一化塑性耗散能的影响,发现在低速冲击下引入正梯度能有效提高结构的前期吸能。然后,以点阵圆柱壳作为芯层,附加内外蒙皮约束建立了点阵夹芯圆柱壳分析模型。通过数值模拟研究了芯层相对密度对动态压溃下点阵夹芯圆柱壳变形模式和比吸能的影响。结果表明结构的胞壁与蒙皮厚度的比值是影响变形模式和比吸能的主要因素。引入梯度对夹芯结构的比吸能无明显影响,但引入负梯度能有效降低六边形点阵夹芯圆柱壳的峰值力。最后,提出了一种负泊松比(内凹六边形)点阵圆柱壳模型,完成了轴向静压实验,并通过数值模拟研究了其在不同压溃速度下的变形模式和平台应力。将正、负泊松比相结合,设计了一种零泊松比点阵(SILICOMB)圆柱壳和点阵夹芯圆柱壳结构。采用数值模拟研究发现,SILICOMB圆柱壳在高速压溃下的平台应力优于六边形点阵圆柱壳,SILICOMB夹芯圆柱壳在芯层相对密度大于4%时,比吸能介于全三角和六边形点阵圆柱壳之间。更多还原

【Abstract】 The lattice cylindrical structure has been widely used in the area of aerospace for its lightweight and high strength.With the recent urgent demand of lightweight energy absorption device,lattice cylindrical shell structure aroused the attention of scholars as a potential energy absorbing component.So far,the investigation of static mechanical properties of lattice cylindrical structure has been well developed,but the understanding of its dynamic deformation and failure mechanism are not clear yet,and the investigation of density gradient lattice cylindrical shell structure is bland.In this paper,the mechanical properties of gradient lattice cylindrical shell and sandwich cylindrical shell under dynamic crushing is studied systematically by theoretical analysis,numerical simulation and experimental verification.The main contents is as follows:Firstly,taking full advantage of the characteristics that 3D printing can manufacture complex microstructures,an ABS triangular lattice cylindrical shell and lattice sandwich cylindrical shell are designed and manufactured.Quasi-static compression tests are conducted to get the carrying ability and energy absorption characteristics,several typical failure modes are observed.It is found that the specific energy absorption of lattice sandwich cylindrical shell are much higher than that of lattice cylindrical shell,the interaction between core and skins can efficiently improve the peak force and energy absorption of structure.Furthermore,the finite element software ABAQUS is adopted to simulate the compression progress of lattice cylindrical structure,good agreement is achieved.Secondly,based on the one-dimensional wave theory,the dynamic plateau stress prediction model of two typical lattice cylindrical shell which are membrane-dominated(triangular configuration)and bending-dominated(hexagonal configuration)is built.It is established that the theoretical prediction results agree well with the finite element simulation results.Then the influence of impact velocity and relative density on the dynamic crushing is considered,revealed the crushing deformation mechanism.Based on that,the influence of density gradient’s magnitude and arrangement on the normalized plastic dissipating energy is investigated,the results show that introducing positive density gradient can enhance the energy absorption at early stage of the crushing for lattice cylindrical shell under low impact velocity.Then,taking lattice cylindrical shell as core,adding inner and outer skin to be the constrain to build the analytical model of lattice sandwich cylindrical shell.The simulation method is used to investigate the deformation modes and special energy absorption(SEA)of lattice sandwich cylindrical shell under dynamic crushing.The results show that the ratio of cell wall to skin thickness is the key factor to influence the deformation modes and SEA.By introducing density to the core of sandwich cylinder,it is found that introducing density gradient can efficiently reduce the peak crushing force of hexagonal lattice sandwich shells but have little effect on the energy absorption.Finally,a kind of negative Poisson’s ratio lattice cylindrical shell model is proposed,and the quasi-static compression is conducted.The deformation modes and plateau stress of lattice cylindrical shell under different crushing velocity are investigated.Combining positive and negative Poisson’s ratio,a zero Poisson’s ratio(SILICOMB)lattice cylindrical shell and sandwich cylindrical shell are designed.It is found that plateau stress of SILICOMB lattice cylindrical shell is inferior to that of the hexagonal lattice cylindrical shell,the special energy absorption of SILICOMB lattice sandwich cylindrical shell is between triangular and hexagonal ones when the relative density of core is beyond 4%.更多还原