A study on compliance characteristics of common crack growth specimens

Abstract

In fracture mechanics tests, one of the parametersthat must be known is the specimen crack length. One of thetechniques used to measure the crack length is `compliancetechnique`. It averages crack length variations through thespecimen thickness and can be easily utilized whereenvironmental chambers make direct crack ~ength measurements·difficult.In this study, the information in the literatureabout compliance cha~acteristics of common crack growthspecimens is reviewed, alternative solutions are compared andnew expressions ~re developed by using compliance data in theliterature.An experimental work is performed to compare .theloading and the unloading compliances in the presence ofplastic deformation and to investigate the effect of cracktip configuration on the compliance characteristics ofcompact tension (C(T» specimens.It is concluded that loading and unloadingcompliances are the same in the presence of plasticdeformation for small scale yielding and it seems that thecompliance calibration curves shift to left with increasingcrack tip radius so that they estimate smaller crack lengthsfor any specific compliance value.