功能梯度材料的制备及接触模拟分析

发布时间：2018-01-06 19:25

本文关键词：功能梯度材料的制备及接触模拟分析　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：功能梯度材料具有随空间位置呈梯度变化的材料属性,它能够减小由于材料失配所导致的应力集中,提高粘接强度,改善表面性能能够在恶劣的热、化学环境中提供保护层。功能梯度材料所具有的独特性质以及潜在的研究前景,使得其成为研究领域的热门学科。由于功能梯度材料用作涂层能够提高接触表面抵抗接触变形能力,可抑制接触损伤和破坏,因而,功能梯度材料的接触力学成为了一个重要的研究课题。本文用热压烧结法制备了铝基氧化铝的梯度材料,并对其微观结构、密度,压缩强度、硬度及压痕等性能进行测试及分析。利用ABAQUS有限元模拟接触力学行为,对均匀材料进行了二维无摩擦及滑动接触模拟分析,将接触应力的数值解与解析解进行对比,分析了层厚及摩擦力对接触应力的影响。对梯度涂层(A1/A1203)半平面进行了二维无摩擦接触模拟,将数值解与理论结果进行了对比,分析了梯度涂层弹性模量比E0/Eh、不同函数形式、梯度指数n对接触应力以及圆压头作用下的力～压痕、力与接触区宽度曲线的影响。研究结果表明:(1)热压烧结法能够制备出密度小,轻质、结构较致密、完整的梯度材料,所制备的梯度材料不仅具有较高的压缩强度,同时也表现出了很好的延展性。(2)通过对韦氏硬度及压痕的测试表明:在同样的法相荷载作用下,梯度材料硬度强于均匀材料;随着氧化铝含量的增加可以提高A1/A1203材料的硬度,同时在梯度材料中仍然能够保持这种性能。(3)对均匀材料无摩擦接触进行数值模拟,法向荷载一定时,随着均匀层厚度的减小,接触压力与解析解的差距越大。(4)对于均匀材料,摩擦系数的改变对法向接触应力分布影响很小,但对平面内张拉应力分布影响很大,前端的最大张拉应力随着摩擦系数的增大而增大。(5)在对梯度涂层半平面无摩擦模拟时,梯度层分为10层就能保证足够的精度。在指数模型下,数值解与理论值的对比吻合较好,该模型可以用来分析功能梯度材料参数按照任意函数形式连续变化的无摩擦接触问题。(6)通过调整涂层材料参数的梯度可以改变表面接触应力的分布。特别地,减小涂层表面的杨氏模量能够减小接触区两端的平面内张拉应力的最大值。这表明可以通过调整涂层梯度来抑制表面开裂,抵抗在滑动和微动条件下所导致的接触损伤。(7)力～压痕关系受涂层弹性模量梯度变化的影响,这表明可以通过压痕试验测出涂层的材料参数梯度。
[Abstract]:Functionally graded materials (FGM) can reduce stress concentration due to mismatch of materials, improve bonding strength and improve surface properties in bad heat. Protective layer in the chemical environment. Unique properties and potential research prospects of functionally graded materials. Functional gradient materials (FGM) as coatings can improve the contact surface resistance to contact deformation and inhibit contact damage and damage. The contact mechanics of functionally graded materials (FGM) has become an important research topic. In this paper, aluminum-based gradient materials were prepared by hot pressing sintering, and their microstructure, density and compressive strength were investigated. The hardness and indentation properties were tested and analyzed. Using ABAQUS finite element method to simulate the contact mechanical behavior, the two-dimensional frictionless and sliding contact simulation analysis of the uniform material was carried out. The numerical solution of contact stress is compared with the analytical solution, and the influence of layer thickness and friction force on contact stress is analyzed. Two-dimensional frictionless contact simulation is carried out on the half-plane of gradient coating A _ 1 / A _ 1203). The numerical solution is compared with the theoretical results. The elastic modulus ratio of gradient coating E0 / Eh, different function forms, the contact stress of gradient exponent n and the force indentation under the action of circular indenter are analyzed. The effect of force and contact zone width curve. The results show that the hot-pressing sintering method can produce gradient materials with small density, light weight, compact structure and integrity. The gradient material not only has high compressive strength, but also shows a good ductility.) through the test of Wechsler hardness and indentation, it is shown that under the same normal phase load. The hardness of gradient material is stronger than that of uniform material. With the increase of alumina content, the hardness of A1 / A1203 material can be improved, and this property can still be maintained in the gradient material. When the normal load is constant, the difference between the contact pressure and the analytical solution increases with the decrease of the thickness of the uniform layer.) for the homogeneous material, the change of friction coefficient has little effect on the normal contact stress distribution. The maximum tensile stress of the front end increases with the increase of friction coefficient. The gradient layer is divided into 10 layers to ensure sufficient accuracy. In the exponential model, the numerical solution is in good agreement with the theoretical value. The model can be used to analyze the frictionless contact problem in which the parameters of functionally graded materials vary continuously according to arbitrary function form. The distribution of surface contact stress can be changed by adjusting the gradient of coating material parameters. Reducing the Young's modulus of the coating surface can reduce the maximum tensile stress in the plane at both ends of the contact zone, which indicates that the surface cracking can be restrained by adjusting the coating gradient. The resistance to contact damage caused by sliding and fretting is affected by the variation of elastic modulus gradient, which indicates that the material parameter gradient of the coating can be measured by indentation test.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34

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