The study shows that the coupled elastic and electric fields inside piezoelectric med ia depend on the speed of the crack propagation, and have singularity at the cr ack tip.
研究表明：介质内的耦合场与裂纹运动速度有关，在裂纹尖端有奇异；
2
The propagation characteristics and the singularity effect of a hollow beam are studied in the third, forth and fifth chapters.