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Articles 1 - 8 of 8
Full-Text Articles in Applied Mechanics
Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook
Microstructural Analysis Of Thermoelastic Response, Nonlinear Creep, And Pervasive Cracking In Heterogeneous Materials, Alden C. Cook
Electronic Theses and Dissertations
This dissertation is concerned with the development of robust numerical solution procedures for the generalized micromechanical analysis of linear and nonlinear constitutive behavior in heterogeneous materials. Although the methods developed are applicable in many engineering, geological, and materials science fields, three main areas are explored in this work. First, a numerical methodology is presented for the thermomechanical analysis of heterogeneous materials with a special focus on real polycrystalline microstructures obtained using electron backscatter diffraction techniques. Asymptotic expansion homogenization and finite element analysis are employed for micromechanical analysis of polycrystalline materials. Effective thermoelastic properties of polycrystalline materials are determined and compared …
Cold Gas Dynamic Spray – Characterization Of Polymeric Deposition, Trenton Bush
Cold Gas Dynamic Spray – Characterization Of Polymeric Deposition, Trenton Bush
Masters Theses
When a solid, ductile particle impacts a substrate at sufficient velocity, the resulting heat, pressure, and plastic deformation can produce bonding at the interface. The use of a supersonic gas flow to accelerate such particles is known as Cold Spray deposition. The Cold Spray process has been commercialized for some metallic materials, but further research is required to unlock the exciting material properties possible with polymeric compounds. In this work, a combined computational and experimental study a) simulated and optimized the nozzle flow conditions necessary to produce bonding in a polyethylene particle, b) developed and fabricated an experimental device, and …
Numerical Studies For Improving Fracture Toughness Resistance Curve Testing Using Single-Edge (Notched) Tension Specimens, Yifan Huang
Electronic Thesis and Dissertation Repository
The fracture toughness resistance curve, i.e. the J-integral resistance curve (J-R curve) or the crack tip opening displacement resistance (CTOD-R) curves, is widely used in the integrity assessment and strain-based design of energy pipelines with respect to planar defects (i.e. cracks). This thesis deals with issues related to the experimental determination of the J(CTOD)-R curves using the newly-developed single-edge (notched) tension (SE(T)) specimens. In the first study, the plastic geometry factor, i.e. the ηpl factor, used to evaluate J in a J-R curve test based on …
Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed
Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed
Theses and Dissertations
The objective of this research is to generate design maps to identify functionally graded microstructures with enhanced fracture toughness. Several Functionally Graded Materials (FGMs) with an edge crack and membrane loading are considered and the resulting J-integral values are computed numerically using Finite Element Analysis. In order to capture the resulting stress fields accurately, Barsoum elements are used in the vicinity of the crack tip and the simulations are carried out for several crack lengths (a) and material contrasts (κ). The averages of the J-integral values are used to determine the normalized Stress Intensity Factors which are then benchmarked with …
Finite Element Modeling Of Delamination Damage In Carbon Fiber Laminates Subject To Low-Velocity Impact And Comparison With Experimental Impact Tests Using Nondestructive Vibrothermography Evaluation, George Rodriguez Iv
Master's Theses
Carbon fiber reinforced composites are utilized in many design applications where high strength, low weight, and/or high stiffness are required. While composite materials can provide high strength and stiffness-to-weight ratios, they are also more complicated to analyze due to their inhomogeneous nature. One important failure mode of composite structures is delamination. This failure mode is common when composite laminates are subject to impact loading.
Various finite element methods for analyzing delamination exist. In this research, a modeling strategy based on contact tiebreak definitions in LS-DYNA®was used. A finite element model of a low-velocity impact event was created to …
Inter-Droplet Membranes For Mechanical Sensing Applications, Nima Tamaddoni Jahromi
Inter-Droplet Membranes For Mechanical Sensing Applications, Nima Tamaddoni Jahromi
Doctoral Dissertations
This dissertation combines self-assembly phenomena of amphiphilic molecules with soft materials to create and characterize mechanoelectrical transducers and sensors whose sensing elements are thin-film bioinspired membranes comprised of phospholipids or amphiphilic polymers. We show that the structures of these amphiphilic molecules tune the mechanical and electrical properties of these membranes. We show that these properties affect the mechanoelectrical sensing characteristic and range of operation of these membrane transducers. In the experiments, we construct and characterize a membrane-based hair cell embodiment that enables the membrane to be responsive to mechanical perturbations of the hair. The resulting oscillations of membranes formed between …
Three-Dimensional Microstructural Effects On Multi-Site Fatigue Crack Nucleation Behaviors Of High Strength Aluminum Alloys, Yan Jin
Theses and Dissertations--Chemical and Materials Engineering
An experimental method was further developed to quantify the anisotropy of multi-site fatigue crack initiation behaviors in high strength Al alloys by four-point bend fatigue testing under stress control. In this method, fatigue crack initiation sites (fatigue weak-links, FWLs) were measured on the sample surface at different cyclic stress levels. The FWL density in an alloy could be best described using a three-parameter Weibull function of stress, though other types of sigmoidal functions might also be used to quantify the relationship between FWL density and stress. The strength distribution of the FWLs was derived from the Weibull function determined by …
A Parametric Study Of Meso-Scale Patterns For Auxetic Mechanical Behavior Optimization, Matthew C. Schuler
A Parametric Study Of Meso-Scale Patterns For Auxetic Mechanical Behavior Optimization, Matthew C. Schuler
Honors Undergraduate Theses
This thesis focuses on the development, parameterization and optimization of a novel meso-scale pattern used to induce auxetic behavior, i.e., negative Poisson's ratio, at the bulk scale. Currently, the majority of auxetic structures are too porous to be utilized in conventional load-bearing applications. For others, manufacturing methods have yet to realize the meso-scale pattern. Consequently, new auxetic structures must be developed in order to confer superior thermo-mechanical responses to structures at high temperature. Additionally, patterns that take into account manufacturing limitations, while maintaining the properties characteristically attached to negative Poisson's Ratio materials, are ideal in order to utilize the potential …