摘要
圆形岩石试件常被用于岩石、混凝土或其他脆性材料复合型断裂强度的测试,但对其受载断裂机理与裂纹尖端的断裂参数认识仍不清晰。无量纲应力强度因子有限元分析模型不仅用于岩石无量纲应力强度因子的求取,还可以获得不同试件形状测试获得纯Ⅱ断裂韧度的裂纹倾角,本文采用有限元建立了受三点弯曲荷载的中心直裂纹半圆盘试件模型和受径向压缩荷载的中心直裂纹圆盘试件模型,通过改变裂纹倾角,求解了从纯Ⅰ型断裂到纯Ⅱ型断裂的不同I-Ⅱ型复合比裂纹的断裂参数,即无量纲应力强度因子及无量纲T应力。研究发现:不同裂纹倾角的中心直裂纹圆盘裂纹尖端无量纲T应力参数均为负值,而三点弯曲半圆盘试件的无量纲T应力参数的正负取决于I-Ⅱ型断裂所占的比例。研究成果可为岩石断裂韧度的测试提供建议和指导。
Disc-type specimens are among favorite test samples for determining mode I and mixed mode fracture toughness in rocks.Although the stress intensity factors KI and KⅡare presented mainly for validation of the analyses,they are also used for determining the crack angle corresponding to pure modeⅡfor each specimen.In this research,the finite element method is used to analyze two disc-type specimens:a semicircular disc specimen containing an edge crack and subjected to three-point-bend loading(SCB specimen),and a centrally cracked circular disc subjected to diametral compressive loading,often called the Brazilian disc specimen.The crack parameters KI,KⅡand T are calculated for different mode mixites from pure mode I to pure modeⅡ.It is shown that in general the T-stress increases for larger crack angles.While the T-stress in the center-cracked circular disc(CCCD)specimens is always negative for any combinations of mode I and modeⅡ,the sign of T-stress in the SCB specimen depends on the mode mixites.The results can provide suggestions and guidance for fracture toughness testing of rock.
作者
段国胜
Duan Guosheng(Qinghai Communications Technical College,Xining Qinghai 810000,China)
出处
《科技通报》
2020年第8期19-24,共6页
Bulletin of Science and Technology
关键词
中心裂纹圆盘
三点弯曲半圆盘
T应力
应力强度因子
断裂参数
central crack brazil disk
three-point semi-disk
T stress
stress intensity factor
fracture parameters
