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Articles 1 - 10 of 10
Full-Text Articles in Mechanical Engineering
Experimental Methods And Practices For The Study Of Toroidal Inflated, Braided Fabric Members, Daniel J. Whitney
Experimental Methods And Practices For The Study Of Toroidal Inflated, Braided Fabric Members, Daniel J. Whitney
Electronic Theses and Dissertations
Inflatable structures have become a very important area of interest for many differing applications where lightweight packable structures are required. NASA is developing Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology that takes advantage of stacked, inflated fabric tori to form a decelerating spacecraft nose cone. The tori consist of a bladder, braided fabric shell, and reinforcing in the form of integral cords or externally bonded straps. The focus of this thesis is on the development of methods for the structural testing of inflated fabric tori and developing an enhanced understanding of their behavior. This is essential for providing insight into the …
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 …
Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte
Analysis Of Fatigue Crack Propagation In Welded Steels, Roberto Angelo Demarte
Master's Theses (2009 -)
This thesis presents the study of fatigue crack propagation in a low carbon steel (ASTM A36) and two different weld metals (AWS A5.18 and AWS A5.28). Fatigue crack propagation data for each weld wire is of interest because of its use for predicting and analyzing service failures. Fatigue crack growth test specimens were developed and fabricated for the low carbon steel base metal and for each weld wire. Weld specimens were stress relieved prior to fatigue testing. Specimens were tested on a closed-loop servo hydraulic test machine at two different load ratios. Fatigue test data was collected to characterize both …
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 …
Metals Additive Manufacturing Powder Aging Characterization, Thomas Russell Lovejoy, Nicholas Karl Muetterties, David Takeo Otsu
Metals Additive Manufacturing Powder Aging Characterization, Thomas Russell Lovejoy, Nicholas Karl Muetterties, David Takeo Otsu
Mechanical Engineering
The metallic additive manufacturing process known as selective laser melting requires highly spherical, normally distributed powder with diameters in the range of 10 to 50 microns. Previous observations have shown a degradation in powder quality over time, resulting in unwanted characteristics in the final printed parts. 21-6-9 stainless steel powder was used to fabricate test parts, with leftover powder recycled back into the machine. Powder samples and test specimens were characterized to observe changes across build cycles. Few changes were observed in the physical and mechanical properties of the specimens, however, there were indications of chemical changes across cycles. Potential …
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 …
Paper Core Feeder System, Sergio Flores Velez
Paper Core Feeder System, Sergio Flores Velez
All Undergraduate Projects
Paragon Films has always strived to increase productivity and decrease waist within their company. The plant located in Union Gap, Washington currently has two production lines operating 24/7 managed by 2 to 3 people. The heavy line produces 5000 to 10000 revolutions per roll. This production line has a three part system that automatically feeds the paper cores to the spool shafts to roll the films. Therefore, the employees during that shift do not have to worry about filling up the bin very often. On the other hand, the second production line, which produces the hand films, does not have …
Methodology For Analyzing Epoxy-Cnt Phononic Crystals For Wave Attenuation And Guiding, Madhu Kolati
Methodology For Analyzing Epoxy-Cnt Phononic Crystals For Wave Attenuation And Guiding, Madhu Kolati
Dissertations, Master's Theses and Master's Reports
Phononic crystals (PhnCs) control, direct and manipulate sound waves to achieve wave guiding and attenuation. This dissertation presents methodology for analyzing nanotube materials based phononic crystals to achieve control over sound, vibration and stress mitigation. Much of the analytical work presented is in identifying frequency band gaps in which sound or vibration cannot propagate through these PhnCs. Wave attenuation and mitigation analysis is demonstrated using finite element simulation. Engineering principles from current research areas of solid mechanics, solid-state physics, elasto-dynamics, mechanical vibrations and acoustics are employed for the methodology. A considerable effort is put to show that these PhnCs can …
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 …