陶瓷材料压缩破坏的数值模拟

发布时间：2018-06-21 01:35

本文选题：陶瓷 + 孔隙　；参考：《宁波大学》2017年硕士论文

【摘要】：采用基于有限元参数映射的格点-弹簧模型(lattice-spring model)对多晶三氧化二铝陶瓷在中、高应变率下的冲击破坏过程进行了数值模拟。该方法的优点是在弹性阶段计算所得的位移,在理论上与有限元的计算结果一致。该方法概念清晰简单,处理断裂比较容易。模型采用弹脆性模型,断裂准则基于Griffith能量平衡原理,晶界作为弱界面被考虑在内,晶界上的附着功根据设定的晶向角之差呈线性变化,它将影响裂纹的扩展。模拟了与实验材料的孔隙率一致的三氧化二铝陶瓷冲击破坏,其压缩强度与实验结果基本吻合。考察了有孔隙和无孔隙陶瓷的冲击响应及其应变率敏感性。结果显示:有孔隙陶瓷表现出一定的率敏感性,而无孔隙陶瓷则没有表现出率敏感性,且前者的裂纹密度时程曲线具有明显的“台阶”,而后者则没有。进一步的分析表明,这些“台阶”所对应的两种止裂机制——应力松弛和晶界突然转向,是有孔隙陶瓷和无孔隙陶瓷的重要区别,也是无孔隙陶瓷表现出相对较高的率敏感性的两种因素。在模型中引入圆孔和狭缝,计算结果表明:孔隙对试件的杨氏模量是有显著影响的,孔隙率越大,杨氏模量越小,并且不同形状的孔隙对杨氏模量削减的程度不同。模拟结果表明相同气孔率下,狭缝比圆孔对杨氏模量的影响更大,且狭缝的所占的比例越大,杨氏模量越小。定性地再现了圆柱玻璃杆撞击刚性壁的过程,结合高速摄像机记录的实验现象对破坏过程进行了分析,计算结果与实验现象基本吻合,即破坏过程为撞击端的破坏波加自由端的层裂。
[Abstract]:A lattice-spring model based on finite element parameter mapping was used to simulate the impact failure process of polycrystalline aluminum trioxide ceramics at medium and high strain rates. The advantage of this method is that the displacement calculated in elastic stage is in agreement with the calculated results of finite element method in theory. The concept of this method is clear and simple, and it is easy to deal with fracture. The model adopts elastic brittleness model, the fracture criterion is based on Griffith energy balance principle, grain boundary is taken into account as weak interface, and the attachment work on grain boundary changes linearly according to the difference of crystal direction angle, which will affect the crack propagation. The impact failure of Al _ 2O _ 3 ceramics, which is consistent with the porosity of the experimental materials, is simulated, and the compressive strength is in good agreement with the experimental results. The impact response and strain rate sensitivity of porous and porous ceramics were investigated. The results show that the porous ceramics show a certain rate sensitivity, while the non-porous ceramics show no rate sensitivity, and the former has obvious "step" of crack density curve, while the latter does not. Further analysis shows that these "steps" correspond to two kinds of crack arrest mechanisms stress relaxation and grain boundary sudden turn, which are the important differences between porous ceramics and non-porous ceramics. It is also two factors that show relatively high rate sensitivity in porous ceramics. The calculation results show that the porosity has a significant effect on the Young's modulus of the specimen. The larger the porosity, the smaller the Young's modulus, and the different shapes of pores reduce the Young's modulus. The simulation results show that the effect of slit on Young's modulus is greater than that of round hole at the same porosity, and the larger the proportion of slit is, the smaller the Young's modulus is. The process of cylindrical glass rod hitting rigid wall is reproduced qualitatively. The failure process is analyzed by combining the experimental phenomena recorded by high-speed camera. The calculated results are in good agreement with the experimental phenomena. That is, the failure process is the spallation of the free end of Boga at the impact end.
【学位授予单位】：宁波大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ174.1

【参考文献】