Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636302
Title: The development of rational computational strategies for the numerical modelling of multi-fracturing solids subjected to high velocity impact
Author: Cottrell, M. G.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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Abstract:
An effective methodology for modelling highly dynamically loaded brittle materials is presented within an explicit finite/discrete element framework. Complex rate and pressure dependent constitutive models are foreseen to provide a high quality comparison with the observed physical response. In addition, a number of intricate mesh update algorithms are required to provide for unconstrained evolving mesh deformation. An isotropic, rate and pressure dependent Johnson-Holmquist (JH2) model is derived in equivalent stress space as a first order estimate of brittle response under highly dynamic compressive stress states. A model for discrete fracture in tensile and compressive stress fields is proposed, defined by a composite yield surface consisting of the fully anisotropic rotating crack band model coupled with the isotropic, rate and pressure dependent Johnson-Holmquist (JH2) model. In addition, a second constitutive description capable of modelling the phenomenon of interface defeat is also proposed, defined by an additive damage function consisting of the standard (JH2) damage function coupled with a new tensile strain dependent term. The envisaged continuous-discontinuous transition introduces additional degrees of freedom into brittle systems and permits large deformation to be realised. This advancement is considered considerable and essential in the recovery of the true brittle material response provoked from large-scale loadings. In addition, large ductile deformations will require fully automated adaptive remeshing strategies to be developed. An advanced approach is proposed, founded on the explicit coupling of the continuum adaptive remeshing technique together with a discrete fracture insertion approach is presented as a means of efficiently and accurately modelling the evolution of brittle deformation. The core adaptive approach is furthered through modelling of 3D ballistic impact, in order to define a set of commonly applicable operating procedures. Where no such continuous-discontinuous description is available or there is no adaptive remeshing capability, the modelling of ballistic events is somewhat limited. Therefore a set of alternative meshless methods is presented within the finite/discrete element framework. Both non-deformable and deformable techniques are considered, and are presented as other choices for modelling ballistic impact. The success of the developed modelling approaches is established by application to a number of physical ballistic systems, including small-scale pellet impact tests, impact of multilayered ceramics, ballistic long rod penetration test, Taylor impact tests, amongst others.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636302  DOI: Not available
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