Failure and Fracture Characteristics of Al2O3 Ceramics under Impact Loading
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摘要: 作为典型的脆性材料,陶瓷对变形具有高度敏感性,在强动载荷下具有完全不同于延性金属材料的损伤、破坏行为等力学响应特性。采用分离式霍普金森杆测试系统对Al2O3陶瓷进行了冲击加载试验,获得了陶瓷的动态抗拉/压力学性能,以及材料破碎特性随应变率的变化关系。利用能量守恒和动力学的理论方法,对脆性陶瓷材料在不同应变率下的力学特性和碎片尺度进行了深入研究。结果表明:在冲击载荷作用下,Al2O3陶瓷的抗拉和抗压强度均与应变率呈正相关。Al2O3陶瓷试样在一维应力波作用下的破碎颗粒尺寸差异较大,随着加载应变率的增加,破碎的陶瓷颗粒总数增大,颗粒平均粒径减小,应力集中的影响逐渐减弱。采用DID模型模拟的脆性材料碎片尺度与实验结果比较吻合,Grady模型源于韧性材料的推广,与实验结果的偏差较大。Abstract: As one of the typical brittle materials, ceramics are highly sensitive to deformation. Under strong dynamic loads, it exhibits mechanical response characteristics completely different from ductile metal materials which involve damage and destructive behavior. In this study, the split Hopkinson bar test system is used to carry out impact loading tests on Al2O3 ceramics obtaining the dynamic tensile/compressive properties of the ceramics, as well as the relationship of fracture characteristics with strain rate. In addition, the mechanical properties and fragment size of brittle ceramic materials under different strain rates are further studied by using the theoretical methods of energy conservation and dynamics. The results show that the tensile and compressive strength of Al2O3 ceramics is positively correlated with strain rate under impact loading. Furthermore, the particle sizes of Al2O3 ceramic samples vary greatly under the action of the one-dimensional stress wave. With the increase of loading strain rate, the total number of broken ceramic particles will increase and the average particle size will decrease, while the influence of stress concentration will gradually weaken. Finally, the fragment size of brittle materials simulated by the DID model is consistent with the experimental results. However, Grady model is derived from the fact that the generalization of ductile materials is quite different from the experimental results.
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Key words:
- Al2O3ceramics /
- effects of strain rate /
- broken scale /
- impact loading
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表 1 不同应变率下Al2O3陶瓷破碎颗粒尺寸
Table 1. Particle size of fractured Al2O3 ceramic under different strain rates
Grain size/${\text{μ}}{\rm m}$ Particle number 238 s–1 300 s–1 364 s–1 417 s–1 600 s–1 734 s–1 <300 571 521 568 689 816 970 300–500 234 236 248 249 265 188 500–1000 38 71 88 74 151 127 1000–1500 69 146 115 99 80 39 >1500 34 28 29 23 22 31 Total particle number 946 1002 1048 1134 1334 1355 Average diameter/mm 344 335 330 323 318 299 $ \rho $/(g·cm–3) E/GPa c/(m·s–1) Gc/(N·m–1) 3.869 290 8658 30 表 3 抗拉/压强度随应变率的变化
Table 3. Tensile strength varies with strain rates
Tensile Compression $\dot \varepsilon$/s–1 $ {\sigma _{\rm{t}}}$/GPa $\dot \varepsilon$/s–1 $ {\sigma _{\rm{c}}}$/GPa ${\dot \varepsilon _0}$/s–1 178 0.127 238 3.25 8820 212 0.135 300 3.28 8902 248 0.146 364 3.34 9072 307 0.155 417 3.41 9282 340 0.165 600 3.49 9716 392 0.178 734 3.58 9934 -
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