Experimental Investigation on Mode I Crack Growth and Damage Mechanism of Sandstone Subjected to Cyclic Loading
Experimental Investigation on Mode I Crack Growth and Damage Mechanism of Sandstone Subjected to Cyclic Loading
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循环荷载作用下砂岩Ⅰ型裂纹扩展及损伤机制的试验研究
DOI：
10.1016/j.engfracmech.2022.108429
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发表时间：
2022-04
影响因子：
5.4
通讯作者：
Jinci Chen;Jiangteng Li;G. Ma
中科院分区：
文献类型：
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作者：
Jinci Chen;Jiangteng Li;G. Ma
为了进一步研究I型裂纹扩展和损伤机制，对不同循环幅值的缺口半圆弯曲（NSCB）试件进行了压缩试验。裂纹扩展仪和数字图像相关（DIC）记录了裂纹扩展的全过程。得到了裂纹扩展过程中水平应变场的实时扩展速率和演化规律。根据裂纹扩展速率，将裂纹扩展过程分为三个阶段：裂纹潜伏期（初级阶段）、稳定裂纹扩展阶段（次级阶段）和加速裂纹扩展阶段（第三阶段）。裂纹潜伏期占整个裂纹扩展的很大比例。稳定裂纹（即稳定的亚临界裂纹扩展）在起裂后缓慢扩展到一定程度，然后加速裂纹扩展导致失效。随着循环幅值的增大，裂纹潜伏期缩短，裂纹扩展速度加快。裂纹扩展速率与应力强度因子呈正相关。利用扫描电子显微镜（SEM）分析了断裂过程区（FPZ）的发展和亚临界裂纹损伤机理。SEM图像显示了两种损伤现象：(1)晶粒脱粘引起的晶间裂纹（主要机制）和(2)穿晶裂纹（次要机制）。
To further investigate the Mode I crack growth and damage mechanism, compression tests were performed on notched semi-circular bending (NSCB) specimens at different cycle amplitudes. The crack propagation gauge and digital image correlation (DIC) recorded the entire process of crack growth. The real-time crack growth rate and evolution of the horizontal strain field during crack growth were obtained. Based on the crack growth rate, the crack growth process can be divided into three stages: the cracking latent period (primary stage), stable crack growth stage (secondary stage), and accelerated crack growth stage (tertiary stage). The cracking latent period accounts for a large proportion of the entire crack growth. The stable crack (i.e., steady subcritical crack growth) expanded slowly to a certain extent after initiation, and then the accelerated crack growth led to failure. With the increase in the cyclic amplitude, the cracking latent period is shortened and the crack growth rate is accelerated. The crack growth rate is positively correlated with the stress intensity factor. Moreover, scanning electron microscopy (SEM) was used to analyse the development of the fracture process zone (FPZ) and the subcritical crack damage mechanism. The SEM images showed two damage phenomena: (1) intergranular cracks caused by grain debonding (primary mechanism) and (2) transgranular cracks (secondary mechanism).