【摘要】 本工作采用双扭曲试验法（DT法）,着重研究了极化条件、直流电场的强度和取向对晶体学取向不同的LiNbO₃晶体中裂纹亚临界扩展行为的影响,并对晶体由裂纹临界扩展导致断裂的形貌作了分析。实验结果表明:LiNbO₃晶体试样的裂纹亚临界扩展方程指数n随晶体学取向的不同而不同,这与裂纹扩展所沿晶面的断裂能有关。未极化的LiNbO₃晶体受直流电场作用时,其亚临界裂纹扩展的加快,系压电晶体电致伸缩效应所致;极化的LiNbO₃晶体试样在直流电场作用下,其亚临界裂纹扩展主要是受晶体的逆压电效应的影响。更多还原

【Abstract】 The effects of polarization conditions and of DC field intensity and direction on the behaviours of subcritical crack propagation for LiNbO₃ with different crystal orientations were investigated by the conventional fracture test,using DT （double torsion）specimens. Experimental results demonstrate that the exponent in the equation of subcritical crack propagating for LiNbO₃ crystals varies with crystal orientation, along with which the crack is propagating. This is associated with the fracture energy of certain crystal planes; the increase of subcritical crack growth for unpolarized LiNbO₃ crystal specimens when affected by the DC field is due to the electrostrictive effect of the piezoelectric crystal; as for polarized LiNbO₃ crystals, the subcritical crack growth is prominently influenced by the negative piezoelectric effect of the crystal.更多还原