A new mixed mode fracture test specimen covering positive and negative values of T-stress

A new fracture test specimen is suggested and analyzed using finite element method. The mode I and mode II stress intensity factors as well as the T-stress were calculated for three geometries and loading conditions.
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A new mixed mode fracture test specimen covering positive and negative values of T-stress Engineering Solid Mechanics 2 (2014) 67-72 Contents lists available at GrowingScience Engineering Solid Mechanics homepage: www.GrowingScience.com/esmA new mixed mode fracture test specimen covering positive and negative values ofT-stressM. M. Mirsayar*Zachry Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USAARTICLE INFO ABSTRACTArticle history: A new fracture test specimen is suggested and analyzed using finite element method. The modeReceived September 20, 2013 I and mode II stress intensity factors as well as the T-stress were calculated for three geometriesReceived in Revised form and loading conditions. It is shown that the specimen, called single edge cracked ring (SECR),October, 14, 2013 covers different mixed mode loading conditions from pure mode I to pure mode II. The SECRAccepted 22 February 2014Available online specimen also covers negative and positive values of T-stresses. From the practical view point,25 February 2014 the suggested specimen can be used easily for mixed mode II fracture tests.Keywords:Brittle fracture mechanicsSECR specimenMixed mode loading conditionsT-stressNumerical analyses © 2014 Growing Science Ltd. All rights reserved.1. Introduction In many industrial and engineering structures mixed mode brittle fracture is the major reason forthe catastrophic failures. In order to study the mixed mode brittle fracture, one can employ theoreticalfracture criteria (Erdogan & Sih, 1963; Sih, 1974; Hussain et al., 1974; Smith et al., 2000, Gomez etal. 2009; Ayatollahi & Aliha 2011) or experimental approaches. Researchers usually use laboratoryspecimens because that the fracture experiments on real components may be difficult or expensive. Asuitable laboratory specimen should be able to provide real state of the stress field adjacent the cracktip and also cover all mixed mode loading conditions from pure mode I (KII = 0) to pure mode II (KI= 0). Heretofore, several cracked specimens have been studied by many researchers for mixed modefracture experiments to determinate the fracture toughness and crack propagation angle such asBrazilian disk (BD), semi-circular bend (SCB) and four points bend specimens (Chang et al., 2002;* Corresponding author. Tel.: +1 (979) 7776096E-mail addresses: mirmilad@tamu.edu (M. M. Mirsayar)© 2013 Growing Science Ltd. All rights reserved.doi: 10.5267/j.esm.2014.2.006668KhanK & Al-- Shayea, 20000; Lim ett al., 1994; Shahani S & Tabatabaei, T , 2008, Alih ha & Ayatolllahi, 2009)).OnO the otheer hand, it is now welll establisheed that the first non-siingular elasstic stress term t (i.e. T- Tstress)s has a consideraable influencce on the frracture tougghness and crack propaagation direection underrmixedm modde loading conditions c in linear elaastic crack pproblems. Among A them m (Ayatollaahi & Alihaa2009),2 pressented a genneralized maximum m taangential sttress (GMT TS) criterionn for fractuure in brittleematerialsm unnder mixed mode loadiing conditioons which taakes into acccount the efffect of T-sttress as welllasa the singgular stress terms (stress intensitty factors KI and KII). ) Many exxperimentall studies onndifferentd labboratory specimens suuch as BD and a SCB indicate the significant s i influence off T-stress innpredictionp oof fracture toughness t annd directionn of fracturee initiation (Ayatollahii & Aliha, 2006, 2 2009)).However,H ssome of lab boratory speecimens haave their ow wn limitatio ons which may m result in errors innfracturef test results. Foor examplee, some of them t are noot able to completely c cover the mixed m modeeloadingl connditions from m pure modde I to pure mode II or may requiree complicatted fixtures for loadingg.AmongA varrious laboratory speciimens, the circular onnes are moore preferaable than other o shapessbecauseb theey can ...