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本文利用显微镜观察记录了玻璃中预制小裂纹稳态与非稳态扩展的全过程。当对玻璃加载到初始压力P和压缩量u时,停止加载,并观察稳态扩展过程,测量破裂扩展的速度。根据测量结果,发现在预制裂纹稳态扩展时,扩展速度随着时间在增长,而初始压力P和压缩量u却保持不变。但是一旦非稳态扩展出现,初始压力P和压缩量u便突然下降。实验中的应力降和地震中的应力降在数量级上是相同的。最后我们讨论了稳态扩展过程中P和u不变的原因。我们认为:Griffith的破裂准则应用到破裂过程时不是十分完善的,需要作适当的修正。
In this paper, the whole process of steady-state and non-steady-state propagation of prefabricated small cracks in glass was recorded by microscopy. When the glass was loaded to the initial pressure P and the amount of compression u, the loading was stopped and the steady-state expansion process was observed and the rate of rupture expansion was measured. According to the results of the measurements, it is found that the propagation speed increases with time while the steady-state propagation of the pre-crack is steady, while the initial pressure P and the compression quantity u remain unchanged. However, once the unsteady expansion occurs, the initial pressure P and the compression amount u suddenly drop. The stress drop in the experiment and the stress drop in the earthquake are the same on the order of magnitude. Finally, we discuss the reason why P and u do not change during steady-state expansion. In our opinion, Griffith’s rupture criterion is not perfect when applied to the rupture process and needs to be properly amended.