Strength Behavior of Polycrystalline Alumina Subjected to Thermal Shock
Strength Behavior of Polycrystalline Alumina Subjected to Thermal Shock
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DOI：
10.1111/j.1151-2916.1970.tb15997.x
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发表时间：
1970-09
影响因子：
3.9
通讯作者：
D. Hasselman
中科院分区：
文献类型：
--
作者：
D. Hasselman
通过圆柱形多晶氧化铝棒的水淬和强度测试，验证了热冲击条件下脆性固体中裂纹扩展行为的理论预测。计算出的热应力断裂所需的淬火温差（ΔTO）与实验结果吻合较好。当断裂开始时，强度急剧下降，与理论一致。根据有关物理参数导出了热应力断裂后剩余强度的表达式。表面断裂能的数值与文献报道的数值相近，与实验结果一致.预测热冲击后的强度与棒直径的1/4次方成反比;两种棒尺寸的实验数据支持这一预测。在淬火温差ΔTΔT0的范围内，强度保持恒定，这与新形成的裂纹是亚临界的理论预期一致。只有在最高的淬火温度差异，可以进一步降低强度观察到的定量变化，但是，被掩盖的非线性变形（证明永久裂纹张开）。得出的结论是，虽然脆性陶瓷的热冲击行为可以近似相当好，可靠的定量估计需要相当多的信息强度和表面断裂能作为环境的函数，应力分布，应变率，温度和试样尺寸的影响。
Theoretical predictions of crack propagation behavior in brittle solids under conditions of thermal shock were verified by water quenching of cylindrical polycrystalline alumina rods followed by strength testing. The calculated quenching temperature difference (ΔTO) required to initiate thermal-stress fracture agreed fairly well with experiment. When fracture was initiated, strength decreased catastrophically, in agreement with theory. An expression for the strength remaining after thermal stress fracture was derived in terms of the pertinent physical parameters. Values of surface fracture energy similar to those reported in the literature agreed with experiment. Strength after thermal shock was predicted to be inversely proportional to the 1/4 power of the rod diameter; this prediction was supported by experimental data for two rod sizes. Over a range of quenching temperature differences ΔTΔT0 strength remained constant, in agreement with the theoretical expectation that the newly formed cracks were subcritical. Only at the highest quenching temperature differences could further decreases in strength be observed; the quantitative changes, however, were masked by nonlinear deformation (evidenced by permanent crack opening). It was concluded that, although thermal shock behavior of brittle ceramics can be approximated fairly well, reliable quantitative estimates require considerably more information about strength and surface fracture energies as a function of environment, stress distribution, strain rate, and temperature and specimen size effects.