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An experimental study of the dynamic features of shadow areas of caustics in response to loading/unloading fracture

许昭永杨润海赵晋明王赟赟熊秉衡王正荣梅世蓉

地震学报（英文版）2002，Vol.15Issue(2)：198-209,12.

An experimental study of the dynamic features of shadow areas of caustics in response to loading/unloading fracture

许昭永 ¹杨润海 ¹赵晋明 ²王赟赟 ²熊秉衡 ³王正荣 ⁴梅世蓉⁵

作者信息

1. Seismological Bureau of Yunnan Province, Kunming 650041, China
2. Seismological Bureau of Yunnan Province, Kunming 650041, China
3. Laser Institute, Kunming Technology University, Kunming 650051, China
4. Laser Institute, Kunming Technology University, Kunming 650051, China
5. Center for Analysis and Prediction, China Seismological Bureau, Beijing 100036, China
折叠

摘要

Abstract

Using a plexiglass sample and by means of real-time holographic interferometry and shadow optical method of caustics, the different features of dynamic variation in stress (strain) field, plastic area and nucleation zone (shadow area) when the sample fractures during loading (loading-fracture) and unloading (unloading-fracture) are studied visually. The results show that the strain nuclei (zones with dense fringes) appear first at the tips of prefabricated cracks at low stress, and then the shadow areas of caustics form with the increase of load. These nuclei and shadow areas can become larger, or smaller, when the process of loading, or unloading, goes on. When the stress is kept within a certain range, the shadow areas of caustics can become larger and smaller alternatively with repeated loading and unloading (cyclic loading). However, when loading and unloading at high stress, in particular when the macrofracture is about to appear, the variations of the shadow areas of caustics are irreversible and quite different. The shadow areas of caustics expand rapidly at an increasing speed when loading-fracture appears. In contrast, the shadow areas of caustics expand at a lower speed when unloading-fracture appears; besides, there is a circular shadow in front of the sharp-angle shaped area.

关键词

loading-fracture/unloading-fracture/shadow areas of caustics/dynamic stress field

Key words

loading-fracture/unloading-fracture/shadow areas of caustics/dynamic stress field

分类

天文与地球科学

引用本文复制引用

许昭永,杨润海,赵晋明,王赟赟,熊秉衡,王正荣,梅世蓉..An experimental study of the dynamic features of shadow areas of caustics in response to loading/unloading fracture[J].地震学报（英文版）,2002,15(2):198-209,12.

基金项目

Key project from China Seismological Bureau (9691309020301) and State Natural Sciences Foundation of China (19732060 and 46764010). （9691309020301）

地震学报（英文版）

ISSN：1000-9116

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