Crack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shell

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dc.contributor.authorCowan, Amy Lorraineen
dc.contributor.committeechairJohnson, Eric R.en
dc.contributor.committeememberKapania, Rakesh K.en
dc.contributor.committeememberLoos, Alfred C.en
dc.contributor.departmentAerospace and Ocean Engineeringen
dc.date.accessioned2011-08-06T16:02:39Zen
dc.date.adate1999-08-28en
dc.date.available2011-08-06T16:02:39Zen
dc.date.issued2002-11-15en
dc.date.rdate2000-08-28en
dc.date.sdate1999-08-25en
dc.description.abstractA finite element model of a fracture test specimen is developed using the STAGS computer code (STructural Analysis of General Shells). The test specimen was an internally pressurized, aluminum cylindrical shell reinforced with two externally bonded aluminum tear straps around its circumference. The shell contained an initial, axial through-crack centered between the straps. The crack propagated slowly in the axial direction as the pressure increased above a certain value until a maximum pressure was attained, and then the crack propagated dynamically. The tear straps sufficiently toughened the shell such that the dynamic crack path bifurcated near the edges of the straps. The bifurcated crack branches ran circumferentially, parallel to the straps causing the shell wall to flap open. The STAGS analysis for the static equilibrium configurations of the fractured shell include geometric nonlinearity and elastic-plastic material behavior. The crack tip opening angle (CTOA) is used in the criterion for ductile crack growth, and the critical value of the CTOA is determined by correlating the STAGS predictions of the stable portion of the crack growth curve (internal pressure versus half crack length) to the test. With the employment of a new STAGS algorithm, the complete axial crack growth curve, including both the stable and unstable portions, through the tear strap is obtained. The complete axial crack growth curve indicates that crack growth through the strap is unlikely. STAGS models with long cracks which bifurcate at various half crack lengths are developed to assess the location of crack bifurcation. Three different stress based crack turning criteria are investigated from the axial crack growth results as a second method for assessing a location of bifurcation. The bifurcation analyses and stress based turning criteria corroborate the experimentally measured bifurcation point. A parametric study is then conducted to determine the influence of tear strap thickness and width on the location of crack bifurcation.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.otheretd-082599-211808en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-082599-211808en
dc.identifier.urihttp://hdl.handle.net/10919/10027en
dc.publisherVirginia Techen
dc.relation.haspartetd.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjecttear strapen
dc.subjectpressurized cylinderen
dc.subjectcrack bifurcationen
dc.titleCrack Path Bifurcation at a Tear Strap in a Pressurized Stiffened Cylindrical Shellen
dc.typeThesisen
thesis.degree.disciplineAerospace and Ocean Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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