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首页> 外文会议>Fracture and strength of solids VII >Influences of Crack Face Bridging Stress and Microstructure on Fracture Toughness of Toughened Alumina Ceramics
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Influences of Crack Face Bridging Stress and Microstructure on Fracture Toughness of Toughened Alumina Ceramics

机译：裂纹面桥接应力和显微组织对增韧氧化铝陶瓷断裂韧性的影响

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Three types of polycrystalline alumina, one pressureless and two hot press sintered AI2O3, were used to examine the effects of the characteristics of microstructure and crack face bridging on fracture toughness. The crack opening displacements and microstructures along the pop-in crack of single edge precracked beam (SEPB) specimens were observed in situ at a constant applied stress intensity factor by scanning electron microscopy (SEM). The bridging stress distribution could be determined from the measured crack opening displacement by three-dimensional finite element analysis, and then the stress intensity factor and stress shielding effect at the crack tip could also be determined. Intergranular microcracks of toughened Al_2O_3 were deflected by a complicated microstructure, and crack closure due to bridging grains was observed near the crack tip. Bridging stress of Al_2O_3 was compressive perpendicular to the crack face and was distributed behind the crack tip. The maximum bridging stress of two hot press sintered Al_2O_3 was about twice as large as that of pressureless sintered Al_2O_3. The fracture toughness of hot press sintered Al_2O_3 was, therefore, higher than that of pressureless sintered Al_2O_3, because the total amount of bridging stress and stress shielding effect increased with increasing magnitude of microcrack deflection and the number of interlocking grains.
机译：三种类型的多晶氧化铝，一种是无压烧结的，两种是热压烧结的Al2O3，用于检验微观结构和裂纹面桥接特性对断裂韧性的影响。通过扫描电子显微镜（SEM）在恒定的施加应力强度因子下原位观察了单边缘预裂梁（SEPB）试件沿弹出裂纹的裂隙位移和微观结构。通过三维有限元分析，从测得的裂纹开口位移可以确定桥应力分布，然后还可以确定裂纹尖端的应力强度因子和应力屏蔽效果。增韧的Al_2O_3的晶间微裂纹由于复杂的微观结构而发生偏转，并且在裂纹尖端附近观察到由于桥接晶粒而导致的裂纹闭合。 Al_2O_3的桥接应力垂直于裂纹面压缩，并分布在裂纹尖端的后面。两种热压烧结的Al_2O_3的最大桥接应力约为无压烧结的Al_2O_3的两倍。因此，热压烧结的Al_2O_3的断裂韧性高于无压烧结的Al_2O_3，这是因为随着微裂纹挠度和互锁晶粒数量的增加，桥连应力和应力屏蔽效果的总量增加。

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