【作者】 刘仁智；

【导师】 杜忠泽； 王经涛；

【作者基本信息】 西安建筑科技大学 ， 材料加工工程， 2005， 硕士

【摘要】 本文建立了一个延性相增韧硬强相的复合组织力学模型,通过对不同体积分数、不同尺寸、不同材料增韧相增韧硬强相基体的强韧化贡献进行计算研究,由此达到对基体的力学性能进行优化。利用模型对增韧复合组织进行压缩与拉伸变形计算,把计算结果与实验数据进行对比,验证模型计算的准确性。所做工作如下: (1) 模仿常规复合材料中高强度相材料加入基体相材料以增强基体强度的复合材料概念,明确提出高塑性低强度相“加入”低塑性高强度相从而达到增韧目的的新复合材料概念,并进一步提出复合增韧的概念。 (2) 揭示脆性基体复合材料的增韧机制,寻找具有最佳增韧效果的微结构组合是当前研究复合组织增韧的首要目的。 (3) 采用细观力学中的模型方法结合有限元计算工具与平均化思想进行研究。代表单元模型的提取参照文献中提供的实物照片,并根据细观力学理论进行了适当简化。 (4) 从细观尺度而非微观尺度的水平,针对增韧“相”尺寸、体积分数、性能对复合增韧材料组织性能的预测和组织优化提出建议。 通过进行以上工作,得出如下结论: (1) 增韧相与基体相力学性能的变化:增韧相表现出明显的应变强化,基体相在延性第二相的软化作用下,塑性增加。 (2) 增韧相与基体相力学性能的匹配:增韧相与基体相的弹性模量与泊松比越接近,增韧相的增韧作用发挥越充分;两相性能差别越大,越容易在两相界面发生应力集中,导致两相脱粘,力学性能变差。 (3) 增韧相的尺寸对复合组织力学性能的影响:增韧相尺寸太小达不到增韧的效果,增韧相尺寸太大恶化两相接触界面。更多还原

【Abstract】 In the paper, a composite mechanical model, soft phase is enclosed in hard phase (Hard-/soft-phase structure is called "bimodal" structure), was built. Simulation was carried on the model. Toughening effect was researched about the contribution of matrix phase and toughening phase whose volume percent、 scale and material are changeable, so, matrix phase mechanical property can be optimized. Uniaxial compression and tensile test simulation and computation were performed. In order to check the accuracy of the model, computation data was compared with experiment data. The work made as follows:(1)This material with "bimodal " structure was viewed as a kind of composite and the idea of hard-/soft-phase composite toughening was put forward.(2)Discovering the toughening mechanism of composite with crisp matrix and searching the optic microstructure combination are principal motive of researching composite structure.(3)By reviewing experimental results and TEM images made by other researchers, a micro-mechanical model of hard-/soft-phase composite toughening was built by several defined steps including building unit cell, confirming basic hypothesis, boundary conditions, and terminating conditions.(4)The static tensile test of unit cells was simulated by finite element method. The theoretical results were compared with the practically experimental results and the rationality and feasibility of the micro-mechanical model was checked. And more, the performance diversity of this hard-/soft-phase composite was studied that was influenced by scale、 volume percentage and shape of toughening phase. Simulation result as follows:(l)The mechanical property change of toughening phase and matrix phase: Toughening phases reveal evident strain strengthening. Matrix phase’s plasticity is improved as toughening phase’s softening.(2)Mechanical property’s matching of two phases: when toughening phase’s elastic modulus and poison’s ration is closer to matrix phase, matrix phase’s toughening effect is better; On the contrary, strong stress concentration between two phases can easily lead to interfaces’ mechanical property deteriorism.(3)The influence of toughening phase’s scale on composite mechanical property: For the same micro-grain, toughening phase’s scale plays a great role in matrix phase’s mechanical property. For example, when scale is above 10um, toughening effect gets better of the counterpart below 10um.(4)The influence on toughening effect of toughening phase’s volume percent: When toughening phase’s volume percent is low, toughening effect is poor. By comparison with toughening phase’s scale, toughening phase’s volume percent has more influence than grain’s scale in toughening effect.(5)The influence on toughening effect of toughening phase’s shape (the paper made a study to ratio of length 、 width and height of cube): Toughening phase’s shape has little influence on composite mechanical property for symmetrical cube.(6)Lastly, the model which soft phase is enclosed in hard phase (called "bimodal" structure) is correct by comparison simulation result with experiment result.更多还原