Crack propagation and coalescence

RFPA

PERGAMONEngineeringFractureMechanics61(1998)311±324

Crackpropagationandcoalescenceinbrittlematerialsundercompression

C.A.Tanga,1,S.Q.Koub,*

aLNM,InstituteofMechanics,ChineseAcademyofSciences,Beijing,100080,People'sRepublicofChinabDivisionofMiningEngineering,LuleaÊUniversityofTechnology,S-97187,LuleaÊ,Sweden

Received25January1998;receivedinrevisedform17July1998;accepted9August1998

Abstract

Twoparticularcasesconcerningcrackpropagationandcoalescenceinbrittlematerialshavebeenmodeledbyusingtherockfailureprocessanalysiscode,RFPA2D,andtheresultshavebeenvalidatedbyreportedexperimentalobservations.Firstly,axialcompressionofnumericalsamplescontaininganumberoflarge,pre-existing¯awsandarowofsuitablyorientedsmaller¯awsaresimulated.Ithasbeencon®rmedthatunderaxialcompression,wing-cracksnucleateatthetipsofthepre-existing¯aws,growwithincreasingcompression,andbecomeparalleltothedirectionofthemaximumfar-®eldcompression.However,coalescenceofthewing-cracksmaybeineithertensilemodeorshearmode,oracombinationofbothmodes.Thenumericalresultsshowqualitativelyareasonablygoodagreementwithreportedexperimentalobservationsforsampleswithsimilar¯awarrangements.Thenumericalresultsdemonstratethat,withacon®ningpressure,thecrackgrowthisstableandstopsatsome®nitecracklength;whereasalateraltensilestressevenwithasmallvaluewillresultinanunstablecrackgrowthafteracertaincracklengthisattained.Secondly,failuremodeinasamplecontaininginhomogeneitiesongrainscalehasalsobeensimulated.Theresultsshowthatthefailuremodestronglydependsonthemechanicalandgeometricpropertiesofthegrainsandinclusions.#1998ElsevierScienceLtd.Allrightsreserved.

Keywords:Numericalsimulation;Cracks;Coalescence;Brittlematerial;Heterogeneity

*Authortowhomcorrespondenceshouldbeaddressed.1CurrentlyatCentreforRockburstsandInducedSeismicityResearch,NortheasternUniversity,Shenyang,110006,People'sRepublicofChina.

0013-7944/98/$-seefrontmatter#1998ElsevierScienceLtd.Allrightsreserved.PII:

S0013-7944(98)00067-8