【作者】 马杰；

【导师】 李东；

【作者基本信息】 东北大学 ， 固体力学， 2018， 硕士

【摘要】 作为一种新型材料,负泊松比材料较传统材料具有更多特殊而优越的力学性能,如剪切模量大、断裂韧度高、吸能效率高、比强度和比刚度高等优点,使得该种材料具有更广阔的应用前景。自美国著名材料科学家Lakes教授利用工业热塑性开孔泡沫首次制得泊松比为-0.7的各向同性泡沫材料,并对其进行力学性能分析之后,负泊松比材料逐渐成为了材料学家关注的焦点之一。本文设计新型具有负泊松比效应的内凹结构模型,利用有限元方法对所设计的结构模型进行准静态力学行为数值模拟分析;同时,结合理论分析及实验研究,验证有限元分析结果的可靠性;并基于遗传算法对负泊松比材料进行结构优化设计,进而确定出具有最优宏观力学特性的负泊松比材料结构参数值,为今后负泊松比材料的实际应用提供重要依据。具体研究内容如下:(1)基于有限元分析方法,建立由两种不同热膨胀系数材料构成的具有负泊松比效应的结构模型,研究该模型的泊松比值与温度变化之间的关系;并利用理论及实验方法对数值结果进行验证分析。研究结果表明:该种双材料结构的泊松比值随温度改变可实现从正到负(或相反)的调控。(2)采用ANSYS/APDL参数化建模方法,建立二维及三维表面具有凹痕的负泊松比多孔结构模型,研究讨论结构表面凹痕尺寸参数对结构的等效泊松比及等效弹性模量的影响;利用3D打印技术制备出几何参数相同的多孔结构试件并对其进行力学特性实验分析,验证数值分析结果的有效性。分析结果表明:该二维及三维表面带有凹痕的负泊松比多孔结构具有较传统蜂窝材料更大的刚度力学特性。(3)利用ANSYS和MATLAB软件对星型多孔负泊松比结构进行最小泊松比和最大等效弹性模量的单目标及多目标优化设计,讨论星型孔微结构胞元尺寸对优化目标的影响,获得具有最优力学特性的负泊松比结构。更多还原

【Abstract】 As a new type of material,negative Poisson’s ratio materials have more special and superior mechanical properties than traditional materials,such as large shear modulus,high fracture toughness,high energy absorption efficiency,high specific strength and specific stiffness.Negative Poisson’s ratio materials have broader application prospects.Since the first famous material scientist Lakes professor using industrial thermoplastic open-cell foam fabricate the isotropic foam material with Poisson’s ratio of-0.7,and its mechanical properties had been analyzed,and then the material structure with negative Poisson’s ratio effect attracts many scholars’ concerns and research.In this paper,novel concave structure models with negative Poisson’s ratio effect are designed and the finite element method is used to conduct quasi-static mechanical behavior numerical simulation of structural models.At the same time,analysis and experimental study are conducted to verify the reliability of the numerical simulation results of the finite element method;and based on genetic algorithm to optimize the negative Poisson’s ratio structure,and then the structural parameters of negative Poisson’s ratio material with the best macro-mechanical properties are determined.It provides an important basis for the future optimization of porous materials design and practical applications.This article mainly studies the following aspects:(1)Based on the finite element analysis method,structural models with negative Poisson’s ratio which is composed of two materials with different thermal expansion coefficients were established and the relationship between Poisson’s ratio and temperatures was studied.And then the theoretical and experimental methods are used to verify the numerical results.The results show that the Poisson’s ratio of this kind of bi-material structure can be changed from positive to negative(or vice versa)with the change of temperature.(2)By using ANSYS/APDL parametric modeling method,novel two-dimensional and three-dimensional structure achieved by alternating rectangular surface indents on the vertical ribs of the unit cells were designed and the effect of size parameter of structure surface dimple on equivalent Poisson’s ratio and equivalent elastic modulus of structure were studied.And then the porous structure specimens with the same geometrical parameters were prepared by 3D printing technique and the mechanical properties of the specimens were analyzed experimentally to verify the validity of numerical analysis results.The results show that the negative Poisson’s ratio porous structures with dimples on the two-dimensional and three-dimensional surfaces are stiffer than traditional honeycomb materials.(3)The single-target and multi-objective optimization design of minimum Poisson’s ratio and maximum equivalent elastic modulus of star-shaped porous negative Poisson’s ratio structure were carried out by using ANSYS and MATLAB software.The influence of the size of the star-hole micro-structure cell on the optimization target is discussed to get the negative Poisson’s ratio structure with the best mechanical properties.更多还原