Events
Fall 2024 Accelerated Nursing Session 1 final exams begin.
Fall 2024 14-week full session final exams begin.
Examinations begin today.
EAS Doctoral Dissertation Defense by Soolmaz Khoshkalam Date: Friday,December 13, 2024 Time: 9:00 a.m. Topic: Potential of Mean Force-Based Lattice Element: Extension to Dynamic and Nonlinear Analysis of Structures Location: LIB 314 Abstract: The potential-of-mean-force (PMF) approach to the lattice element method (LEM) has recently been adapted to model the response of structural systems. LEM relies on lattice discretization of the domain via a set of particles that interact through prescribed potential functions, representing the mechanical properties of members. The approach offers unique advantages, including robustness to discontinuity and failure without the need for mesh refinement. The overall goal of this research is two-fold: (i) extend the quasi-static PMF-based LEM to model the dynamic behavior of structures (ii) blend the quasi-static PMF-based LEM with Force Analogy method for nonlinear analysis. Such developments provide a means for simulating nonlinear response and failure under dynamic loading that is the nature of most natural hazards and extreme conditions. To accomplish the first goal, integration methods from Molecular Dynamics (MD) are used to estimate of the trajectory of particles in the Lattice Element Method (LEM) and to simulate the dynamic response with a focus on structural (or building) systems. More specifically Verlet-Velocity method is used to estimate the location and momentum of each particle at every time step. To assure accuracy and the numerical stability, we also explore implicit integration techniques such as Hilber-Hughes-Taylor method and midpoint method. Noting that the rotational degrees of freedom have minimal contribution to the kinetic energy of the system we develop an energy-based approach for condensation to reduce the computational cost. Our approach relies on the Euler-Lagrange equations and manifests itself in the form of minimum potential energy theorem for mass-less degrees of freedom. To address another critical aspect of dynamic simulation, the mass matrix, we adopt an energy-based approach and utilize the kinetic energy of the lattice elements to maintain consistency with the kinetic energy of their continuous counterparts. To achieve the second goal, we incorporate the nonlinear behavior of materials under various actions, including bending, torsion, and axial forces, through the introduction of novel potential functions inspired by the Force Analogy Method. These potential functions are calibrated using section properties that represent the nonlinear stress-strain responses of materials, such as nonlinear moment-curvature relationships. The utility of the proposed framework and its and accuracy are validated through its application in quasi-static linear and nonlinear simulations of large-scale buildings subjected to different loading conditions. ADVISOR(S): Dr. Mazdak Tootkaboni, Dept of Civil and Environmental Engineering (Advisor) (mtootkaboni@umassd.edu) Dr. Arghavan Louhghalam, Dept. of Civil and Environmental Engineering (Co-Advisor) (Arghavan_Louhghalam@uml.edu) COMMITTEE MEMBERS: Dr. Alfa Heryudono, Department of Mathematics and Dr. Zheng Chen, Department of Mathematics NOTE: All EAS Students are ENCOURAGED to attend.
Fall 2024 Second 7-week session classes end, last class before final exam.
EAS Doctoral Proposal Defense by Zhuoyuan Leng Date: Tuesday, December 17, 2024 Time: 10:00am Topic: Experimental and Numerical Studies on Mixed-mode Fracture of Additively Manufactured Polymer Nanocomposites Location: LIB 314 Zoom Link: https://umassd.zoom.us/j/92967323046?pwd=ppH0sI5z79H46F0rQhSkb2S4Y16mlA.1 Abstract: This study investigates the mixed-mode fracture behavior of ABS nanocomposites fabricated using fused deposition modeling (FDM) for automotive and aerospace applications. The scope includes quasi-static and dynamic mixed-mode fracture scenarios, and cyclic mixed-mode fatigue fracture properties, using experimental and numerical methods, focusing on understanding crack dynamics and enhancing the fracture toughness of ABS composites. It explores fracture criteria under mixed mode loading conditions and assesses the influence of printing direction, loading type, and nanoparticle weight percentage. The experimental methodology is divided into three parts: (1) quasi-static mixed-mode loading of ABS nanocomposites with different printing directions, (2) dynamic mixed-mode loading using a modified Hopkinson pressure bar setup, and (3) cyclic fatigue loading to assess fatigue fracture performance. Scanning electron microscopy (SEM) will be used to analyze fracture surfaces and correlate them to fracture mechanisms under various mode-mixities and loading conditions. Simulation studies focus on crack dynamics using the phase-field method (PF) implemented in COMSOL, with anisotropic material formulations to model different printing directions and dynamic loading scenarios. Comparisons between simulations and experiments will enhance the understanding of fracture mechanisms. The outcome can be used to optimize ABS nanocomposite performance and provide insights for structural applications. ADVISOR(S): Dr. Vijaya Chalivendra, Department of Mechanical Engineering (vchalivendra@umassd.edu) COMMITTEE MEMBERS: Dr. Caiwei Shen, Department of Mechanical Engineering Dr. Jay Wang, Department of Physics Dr. Jun Li, Research Associate Professor, ERAU NOTE: All EAS Students are ENCOURAGED to attend.
Fall 2024 Final Exams end for the Third 5-week session MLT-MLS Program classes.
Fall 2024 Accelerated Nursing Session 1 final exams end.
Fall 2024 14-week full session final exams end.
Fall 2024 Second 7-week session final exam day.
Examinations end today.
Fall 2024 Second 7-week session grades are due, 72 hours from final exam day.