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Description
Access control is necessary for information assurance in many of today's applications such as banking and electronic health record. Access control breaches are critical security problems that can result from unintended and improper implementation of security policies. Security testing can help identify security vulnerabilities early and avoid unexpected expensive cost in handling breaches for security architects and security engineers. The process of security testing which involves creating tests that effectively examine vulnerabilities is a challenging task. Role-Based Access Control (RBAC) has been widely adopted to support fine-grained access control. However, in practice, due to its complexity including role management, role hierarchy with hundreds of roles, and their associated privileges and users, systematically testing RBAC systems is crucial to ensure the security in various domains ranging from cyber-infrastructure to mission-critical applications. In this thesis, we introduce i) a security testing technique for RBAC systems considering the principle of maximum privileges, the structure of the role hierarchy, and a new security test coverage criterion; ii) a MTBDD (Multi-Terminal Binary Decision Diagram) based representation of RBAC security policy including RHMTBDD (Role Hierarchy MTBDD) to efficiently generate effective positive and negative security test cases; and iii) a security testing framework which takes an XACML-based RBAC security policy as an input, parses it into a RHMTBDD representation and then generates positive and negative test cases. We also demonstrate the efficacy of our approach through case studies.
ContributorsGupta, Poonam (Author) / Ahn, Gail-Joon (Thesis advisor) / Collofello, James (Committee member) / Huang, Dijiang (Committee member) / Arizona State University (Publisher)
Created2014
Description
This research summarizes the characterization of the constituent materials of a unidirectional composite for use in a finite element model. Specifically the T800s-F3900 composite from Toray Composites, Seattle, WA. Testing was carried out on cured polymer matrix provided by the manufacturer and single fiber specimen. The material model chosen for the polymer matrix was MAT 187 (Semi-Analytical Model for Polymers) which allowed for input of the tension, compression, and shear load responses.
The matrix was tested in tension, compression, and shear and was assumed to be isotropic. Ultimate strengths of the matrix were found to be 10 580 psi in tension, 25 900 psi in compression, and 5 940 in shear. The material properties calculated suggest the resin as being an isotropic material with the moduli in tension and compression being approximately equal (3% difference between the experimental values) and the shear modulus following typical isotropic relations. Single fiber properties were obtained for the T800s fiber in tension only with the modulus being approximately 40 500 ksi and the peak stress value being approximately 309 ksi.
The material model predicts the behavior of the multi-element testing simulations in both deformation and failure in the direction of loading.
The matrix was tested in tension, compression, and shear and was assumed to be isotropic. Ultimate strengths of the matrix were found to be 10 580 psi in tension, 25 900 psi in compression, and 5 940 in shear. The material properties calculated suggest the resin as being an isotropic material with the moduli in tension and compression being approximately equal (3% difference between the experimental values) and the shear modulus following typical isotropic relations. Single fiber properties were obtained for the T800s fiber in tension only with the modulus being approximately 40 500 ksi and the peak stress value being approximately 309 ksi.
The material model predicts the behavior of the multi-element testing simulations in both deformation and failure in the direction of loading.
ContributorsRobbins, Joshua (Author) / Rajan, Subramaniam D. (Thesis advisor) / Mobasher, Barzin (Committee member) / Hoover, Christian (Committee member) / Arizona State University (Publisher)
Created2019
Description
Composite materials are finally providing uses hitherto reserved for metals in structural systems applications – airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. They have high strength-to-weight ratios, are durable and resistant to environmental effects, have high impact strength, and can be manufactured in a variety of shapes. Generalized constitutive models are being developed to accurately model composite systems so they can be used in implicit and explicit finite element analysis. These models require extensive characterization of the composite material as input. The particular constitutive model of interest for this research is a three-dimensional orthotropic elasto-plastic composite material model that requires a total of 12 experimental stress-strain curves, yield stresses, and Young’s Modulus and Poisson’s ratio in the material directions as input. Sometimes it is not possible to carry out reliable experimental tests needed to characterize the composite material. One solution is using virtual testing to fill the gaps in available experimental data. A Virtual Testing Software System (VTSS) has been developed to address the need for a less restrictive method to characterize a three-dimensional orthotropic composite material. The system takes in the material properties of the constituents and completes all 12 of the necessary characterization tests using finite element (FE) models. Verification and validation test cases demonstrate the capabilities of the VTSS.
ContributorsHarrington, Joseph (Author) / Rajan, Subramaniam D. (Thesis advisor) / Neithalath, Narayanan (Committee member) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2015