岩石断裂韧度试样CCNBD临界应力强度因子的全新数值标定  

A new numerical calibration of the critical stress intensity factor for the CCNBD specimens used in rock fracture toughness test

作　　者：樊鸿[1] 张盛[2] 苟小平[1] 王启智[1,3] 

机构地区：[1]四川大学,成都610065 [2]河南理工大学,焦作454001 [3]深部岩土力学与地下工程国家重点实验室,北京10083

出　　处：《应用力学学报》2011年第4期416-422,455,共7页Chinese Journal of Applied Mechanics

基　　金：深部岩土力学与地下工程国家重点实验室开放基金(SKLGDUEK1020)

摘　　要：国际岩石力学学会(ISRM)提出的用人字型切槽巴西圆盘(Cracked Chevron Notched Brazilian Disc—CCNBD)测试岩石I型断裂韧度所必需的量纲为一的临界应力强度因子Y*min的精度需要进一步改进。本文对CCNBD试样的Y*min进行了系统的重新标定,CCNBD的几何参数有效范围为0.44≤αB≤1.04、0≤α0≤0.69、0.4≤α1≤0.8。采用有限单元法对CCNBD做三维数值分析,得到了435种CCNBD试样的Y*min值标定结果;在此基础上全面修正了CCNBD试样Y*min计算公式中u和v的取值表;给出了不用查表直接确定CCNBD试样Y*min值的近似表达式,该表达式计算结果与标定结果的相对误差绝对值在1.87%以内。对于ISRM建议的CCNBD标准试样的Y*min值:ISRM标定值0.84比本文结果0.957小12.2%;分片合成法标定值0.947比本文结果小1.0%;子模型法标定值0.943比本文结果小1.5%。本文特别强调了任何CCNBD试样Y*min的取值必须在它对应的上限和下限所限定的范围内,这一要求对判断Y*min标定值是否合理是很重要的。International Society for Rock Mechanics(ISRM) proposed cracked chevron notched Brazilian disc(CCNBD) to test mode I fracture toughness of rock,however,calibration of the critical dimensionless stress intensity factor,i.e.Y*min,should be further improved to achieve better accuracy.In this paper,wide-ranging Y*min values are recalibrated systematically,with valid range of the geometric parameters for CCNBD defined as 0.44≤αB≤1.04,0≤α0≤0.69,0.4≤α1≤0.8.Three-dimensional numerical analysis is done with finite element method,totally 435 CCNBD specimens are calibrated to derive their Y*min values,based on these results,u,v values used in the formula to calculate Y*min for CCNBD are completely modified.Furthermore,an approximate expression used to calculate CCNBD directly without using the tabulated u,v values is presented,the accuracy of the expression is within 1.87% as compared with the calibrated Y*min values.For the Y*min value of the ISRM suggested CCNBD standard specimen,0.84 was the value given by the ISRM,0.947 was the value obtained with the slice synthesis method,0.943 was the value derived with the sub-model method,while 0.957 is the value presented in this paper.It is especially emphasized that for any CCNBD specimen its Y*min value should stand properly between the corresponding upper bound and lower bound,this criterion is vital in judging whether the Y*min value is reasonable or not.

关 键 词：人字型切槽巴西圆盘(CCNBD) 量纲为一的临界应力强度因子 I型断裂韧度 有限元法 宽范围标定 

分 类 号：O346[理学—固体力学]