考虑微裂纹损伤的碳化硅陶瓷力学性能数值仿真研究

发布时间：2018-03-19 08:38

  本文选题：微裂纹损伤　切入点：力学性能　出处：《湘潭大学》2016年硕士论文　论文类型：学位论文

【摘要】：陶瓷等脆性材料的损伤与破坏过程一直是学者们的研究热点及难点。碳化硅陶瓷属于典型的硬脆性材料,具有优良的机械、热、化学性能,如较高的抗弯强度、优良的抗氧化性及低摩擦系数,广泛应用于机械、微电子等行业。以往学者在研究脆性材料的力学性能及破坏过程时,大多从材料宏观层次出发,将其假定为均质的理想连续体进行建模和仿真。这种简化尽管在一定程度上满足了工程实践的需要,但却难以研究脆性材料在外载荷作用下裂纹萌生、扩展以及贯通而导致的由细观层次到宏观层次的损伤与破坏过程。随着研究的不断深入,从细观尺度来研究脆性材料的断裂过程已经成为研究学者不可回避的问题。尤其是随着计算机技术的飞速发展,数值模拟方法为脆性材料的裂纹起始、扩展以及贯通,直至器件的宏观断裂等研究提供了更为丰富的研究手段。本文基于离散元方法研究了随机微裂纹损伤对碳化硅陶瓷试样力学性能的影响,其主要研究内容如下:首先,建立了碳化硅陶瓷的中心斜裂纹离散元模型,研究了中心斜裂纹对试样单轴压缩力学性能的影响;分析了碳化硅陶瓷破裂过程中力链的变化情况,得到了不同裂纹角对力链角度分布的影响;同时,研究了预应力对裂纹扩展、破坏模式及力学性能的影响。其次,在中心斜裂纹的研究基础上将离散元模型扩展到等长共线裂纹及多条随机分布的裂纹系模型,研究了等长共线裂纹的裂纹角及内间距对试样力学性能的影响;建立了碳化硅陶瓷离散元模型的裂纹密度函数,研究了裂纹系模型中裂纹密度对试样破坏模式与力学性能的影响,其结果与Mori-Tanaka方法的理论结果相符;通过改变预设裂纹的分布情况,得到了不同的预设裂纹分布对试样破坏模式及单轴压缩力学性能的影响;并研究了预应力对含裂纹系试样力学性能的影响。最后,将裂纹系模型引入到碳化硅陶瓷切削加工模型中,得到了不同裂纹密度条件下预应力、切削速度、背吃刀量等对切削加工过程的影响规律。
[Abstract]:The damage and failure process of brittle materials, such as ceramics, has been a hot and difficult point for scholars. Silicon carbide ceramics is a typical hard brittle material with excellent mechanical, thermal and chemical properties, such as high bending strength. The excellent oxidation resistance and low friction coefficient are widely used in mechanical, microelectronics and other industries. In the past, when studying the mechanical properties and the failure process of brittle materials, most scholars started from the macroscopic level of materials. It is assumed to be a homogeneous ideal continuum for modeling and simulation. Although this simplification meets the needs of engineering practice to some extent, it is difficult to study the crack initiation of brittle materials under external loading. The process of damage and destruction from the microscopic to the macro level resulting from expansion and penetration. With the development of the research, It has become an unavoidable problem for researchers to study the fracture process of brittle materials from meso-scale, especially with the rapid development of computer technology, the numerical simulation methods are crack initiation, propagation and penetration of brittle materials. In this paper, the effects of random microcrack damage on mechanical properties of silicon carbide ceramic samples are studied based on discrete element method. The main research contents are as follows: first of all, The discrete element model of the central oblique crack of sic ceramics is established, the effect of the central oblique crack on the mechanical properties of the specimen under uniaxial compression is studied, and the variation of the force chain during the rupture of the sic ceramic is analyzed. The effects of different crack angles on the angular distribution of force chains are obtained. At the same time, the effects of prestress on crack propagation, failure mode and mechanical properties are studied. Based on the research of central oblique crack, the discrete element model is extended to the equal-length collinear crack and several random distribution crack system models, and the influence of crack angle and internal distance of isometric collinear crack on the mechanical properties of specimen is studied. The crack density function of the discrete element model of silicon carbide ceramics is established. The effect of crack density on the failure mode and mechanical properties of the specimen in the crack system model is studied. The results are in agreement with the theoretical results of the Mori-Tanaka method. By changing the distribution of preset cracks, the effects of different preset crack distributions on the failure modes and uniaxial compressive properties of specimens are obtained, and the effects of prestress on the mechanical properties of cracked specimens are studied. The crack system model is introduced into the cutting model of silicon carbide ceramics, and the influence of prestress, cutting speed and the amount of the back cutter on the cutting process under different crack density are obtained.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ174.758.12
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本文编号：1633494