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The Ductile to Brittle Transition in Polycarbonate

dc.contributor.advisor Stepp, David
dc.contributor.advisor Dolbow, John Pogacnik, Justin 2012-05-29T16:40:01Z 2012-05-29T16:40:01Z 2011
dc.description.abstract <p>An advanced bulk constitutive model is used with a new cohesive zone model that is stress state and rate-dependent in order to simulate the ductile to brittle failure transition in polycarbonate. The cohesive zone model is motivated by experimental evidence that two different critical energies per unit area of crack growth exist in glassy polymers. A higher energy state is associated with ductile failure (slow crack growth), while a lower energy state is associated with brittle failure (fast crack growth). The model is formulated so that as rate or stress state changes within a simulation, the fracture energy and thus fracture mode may also change appropriately. The ductile to brittle transition occurs when the cohesive opening rate is over a threshold opening rate and when the stress state is close to plane strain in a fracture specimen. These effects are coupled. The principal contribution of this work is that this is the first time a single set of material input parameters can predict the transition from slow to fast crack growth as test loading rate and sample thickness are varied. This result enlisted the use of an advanced constitutive model and the new cohesive zone model with rate and stress-state dependencies in three-dimensional finite element analysis.</p>
dc.subject Mechanical Engineering
dc.subject Cohesive Zone Model
dc.subject Finite Element Analysis
dc.subject Fracture
dc.subject Polycarbonate
dc.title The Ductile to Brittle Transition in Polycarbonate
dc.type Dissertation
dc.department Mechanical Engineering and Materials Science

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