本文選題：陶瓷 + 孔隙��； 參考：《寧波大學(xué)》2017年碩士論文

【摘要】：采用基于有限元參數(shù)映射的格點-彈簧模型(lattice-spring model)對多晶三氧化二鋁陶瓷在中、高應(yīng)變率下的沖擊破壞過程進(jìn)行了數(shù)值模擬。該方法的優(yōu)點是在彈性階段計算所得的位移,在理論上與有限元的計算結(jié)果一致。該方法概念清晰簡單,處理斷裂比較容易。模型采用彈脆性模型,斷裂準(zhǔn)則基于Griffith能量平衡原理,晶界作為弱界面被考慮在內(nèi),晶界上的附著功根據(jù)設(shè)定的晶向角之差呈線性變化,它將影響裂紋的擴展。模擬了與實驗材料的孔隙率一致的三氧化二鋁陶瓷沖擊破壞,其壓縮強度與實驗結(jié)果基本吻合�？疾炝擞锌紫逗蜔o孔隙陶瓷的沖擊響應(yīng)及其應(yīng)變率敏感性。結(jié)果顯示:有孔隙陶瓷表現(xiàn)出一定的率敏感性,而無孔隙陶瓷則沒有表現(xiàn)出率敏感性,且前者的裂紋密度時程曲線具有明顯的“臺階”,而后者則沒有。進(jìn)一步的分析表明,這些“臺階”所對應(yīng)的兩種止裂機制——應(yīng)力松弛和晶界突然轉(zhuǎn)向,是有孔隙陶瓷和無孔隙陶瓷的重要區(qū)別,也是無孔隙陶瓷表現(xiàn)出相對較高的率敏感性的兩種因素。在模型中引入圓孔和狹縫,計算結(jié)果表明:孔隙對試件的楊氏模量是有顯著影響的,孔隙率越大,楊氏模量越小,并且不同形狀的孔隙對楊氏模量削減的程度不同。模擬結(jié)果表明相同氣孔率下,狹縫比圓孔對楊氏模量的影響更大,且狹縫的所占的比例越大,楊氏模量越小。定性地再現(xiàn)了圓柱玻璃桿撞擊剛性壁的過程,結(jié)合高速攝像機記錄的實驗現(xiàn)象對破壞過程進(jìn)行了分析,計算結(jié)果與實驗現(xiàn)象基本吻合,即破壞過程為撞擊端的破壞波加自由端的層裂。
[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.
【學(xué)位授予單位】：寧波大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ174.1

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本文編號：2046587