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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorDe, Suvranu
dc.contributorAnderson, Kurt S.
dc.contributorHuang, Liping
dc.contributorManiatty, Antoinette M.
dc.contributor.authorJosyula, Kartik
dc.date.accessioned2021-11-03T09:00:06Z
dc.date.available2021-11-03T09:00:06Z
dc.date.created2018-07-27T15:06:22Z
dc.date.issued2018-05
dc.identifier.urihttps://hdl.handle.net/20.500.13015/2185
dc.descriptionMay 2018
dc.descriptionSchool of Engineering
dc.description.abstractUsing thermomechanical properties of γ-RDX, we studied the anisotropic constitutive response of single crystals of α- and γ-RDX using a crystal plasticity-based continuum model. The slip system activation and the extent of plastic slip observed in γ-RDX explain the experimental observations on the anisotropic shock sensitivity of RDX. The results indicate that modeling of γ-RDX is important in understanding the shock sensitivity of RDX. Next, we studied the α-γ phase transition under hydrostatic loading using SB potential. The phase transformation was observed for temperatures beyond 350 K. The simulations show the abrupt changes in volume, the molecular energy terms of the SB potential, and the wag angles of the molecules that are associated with the phase transition. We also hypothesize that the angle energy might play an important role in the ability of the SB potential to simulate α-γ phase transition. Further, we developed a thermodynamically consistent level set approach based on regularization energy functional to capture α-γ phase transformation in single crystal RDX under shock loading. The reinitialization scheme used in our approach leads to an embedded regularization flux within the level set equation so that additional reinitialization step is not required. The level set approach is shown to compare well with the velocity extension method in capturing the phase interface position. It is also shown to capture the characteristics of the shock-induced α-γ phase transformation for loading along (100) crystal orientation such as relaxation behind the phase interface and the finite time required for the phase transformation to complete.
dc.description.abstractThe objective of this research is to model the α-γ phase transition in 1,3,5- Trinitroperhydro-1,3,5-triazine (commonly known as RDX) and investigate the role of such solid-solid phase transformation in the detonation sensitivity of RDX. It is known that shock loaded RDX crystals undergo phase transformation from ground state α-RDX to high pressure γ-RDX around 3-4 GPa. In order to appropriately capture the physics of high loading rates, the evolution of the material parameters, especially the elastic tensor, with pressure and temperature for both α- and γ- polymorphs must be incorporated into a continuum scale model. While thermomechanical properties of α-RDX are reported in the literature, they are not readily available for the high-pressure γ-polymorph. We have determined the elastic modulus tensor, coefficients of thermal expansion, and pVT equation of state for γ-RDX as functions of temperature and pressure using molecular dynamics simulations with a non-reactive fully flexible Smith and Bharadwaj (SB) molecular potential. The elastic moduli for γ-RDX exhibit strong sensitivity to variations in pressure and negligible variation with respect to temperature, which is similar to that observed in α-RDX.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMechanical engineering
dc.titleComputational investigation of the α-γ phase transformation in 1,3,5-trinitroperhydro-1,3,5-triazine
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid178965
dc.digitool.pid178966
dc.digitool.pid178967
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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