Browsing by Subject "Glass"
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Item A failure prediction model for window glass(Texas Tech University, 1980-05) Beason, William L.There is a need within engineering practice for an analytical method to predict the probability of failure of window glass plates subjected to lateral loads. The failure prediction technique should include provision for all significant factors which influence glass strength and all significant factors which influence plate behavior The ultimate use of the glass plate failure prediction model will be to provide a realistic assessment of glass plate strength to be used in the design of window glass.Item A Materials Science Driven Pattern Generation Solution to Fracturing Computer Generated Glass for Films and Games(2014-08-11) Monroe, David CharlesBelievably and realistically fracturing computer generated glass for visual effects has been previously solved through various methods such as algorithmic approaches, utilizing texture maps, or finite element analysis. These solutions can achieve some believable results but often at the cost of one or more of the following: simulation time, preparation time, art directability, consistency with materials science research, or the requirement of creating or utilizing fixed assets or maps. In this thesis I present a novel method that draws from the appropriate literature and focuses on quickly generating accurate fracture patterns. The method takes inputs such as the artist?s animation of an impact and desired object properties, and outputs fracture patterns used for breaking objects apart based on input values, materials science literature, and fracture mechanics. After determining all of the fracture pattern variables such as the number of radial and concentric cracks, the artist is able to override the computed parameters to retain control and art directability. Implementation of this method was performed using MAXScript, the built-in scripting language for Autodesk 3ds Max. The result is a computationally fast and mechanically accurate tool while retaining art directability to fulfill film storyboards or game design.Item A simplified model for analyzing the nonlinear dynamic response of thin plates(Texas Tech University, 1986-08) Lim, Gee LooNot availableItem Blast resistant glazing tests(Texas Tech University, 2003-05) Samuels, Steven RRecent attacks at home and abroad have increased concems about blast-resistant glazings. The Glass Research and Testing Laboratory (GRTL) conducted fíve blast tests. This thesis describes the procedure for five fiill-scale blast-resistant glazing tests and the air blast pressure-time history analysis. One free field pressure transducer and three reflected pressure transducers collected 40960 points per second of air blast pressure-time data from the blast tests. These data facilitated the prediction of peak air blast pressures and positive phase impulses acting on the blast-resistant test specimen. They indicated that air blast pressure exerted an equivalent GS A Level D air blast pressure loading on the test specimen. The blast-resistant glazing consisted of an insulating glass unit fabricated with laminated glass. The insulating glass units consisted of two VA in. (6.0 mm) heat sfrengthened laminated glass lites with a 0.030 in. (0.76 mm) polyvinyl butyral (PVB) interlayer sealing a Vi in. (13 mm) air space. The design blast consisted of 250 Ibs of ANFO at a standoff distance of 75 ft. The GRTL staff determined the test specimen adequately resisted a GSA Level D air blast loading of 10 psi peak air blast pressure and 80 psi-msec positive phase impulse. Although many of the laminated glass units fractured under the blast loading, the units remained in the glass frame, they maintained closure of their fenestration, and the witness panel located twelve inches behind the test specimen remained free of flying or falling glass shard.Item Breakage characteristics of window glass subjected to small missle impacts.(Texas Tech University, 1974-12) Beason, William L.Not availableItem Characterization and modeling of mixed-mode I+III fracture in brittle materials(2015-12) Pham, Khai Hong; Ravi-Chandar, K.; Landis, Chad M; Liechti, Kenneth M; Mear, Mark E; Marder, Michael PMixed-mode I+III fracture in brittle materials presents spectacular, scale-independent pattern formation in nature and engineering applications; and it is one of the last remaining puzzles in linear elastic fracture mechanics. This problem has received much attention in the literature over the past few decades both from experiments and analysis, but there are still open challenges that remain. Specifically, the existence of a threshold ratio of mode III to mode I loading below which fragmentation of the crack front (formation of daughter cracks) does not occur and the length scale associated with the spacing of the fragments when they do occur are still under debate. The continued growth of cracks under remote mode I + III loading is also of interest; it is observed that in some cases the fragmented cracks coalesce, while in others they maintain their independent development. We approach this problem through carefully designed experiments to examine the physical aspects of crack initiation and growth. This is then explored further through numerical simulations of the stress state that explore the influence of perturbations on the formation of daughter cracks. We show that a parent crack subjected to combined modes I+III loading exhibits fragmentation of the crack front into daughter cracks without any threshold. The distance between the daughter cracks is dictated by the length scale corresponding to the decay of the elastic field; this decay depends on the characteristic dimension of the parent crack from which the daughter cracks are nucleated. As the daughter cracks continue growing, they coarsen in spacing also through elastic shielding. As the daughter cracks grow farther, the parent crack, pinned at the original position, experiences increased stress intensity factor and the bridging regions begin to crack and the parent crack front advances towards the daughter cracks. This establishes a steady state condition for the system of parent crack with equally spaced daughter cracks to continue growing together. Finally, direct numerical simulation of crack initiation and growth is explored using a phase-field model. The model is first validated for in-plane modes I + II through comparison to experiments, and then used to explore combined modes I + III in order to study the above mechanism of mixed-mode I + III crack growth.Item The dynamic mechanical response of polymer-based nanocomposites and network glasses(2004) Putz, Karl William; Green, Peter F. (Peter Fitzroy)The structural entities, atomic or molecular, that constitute a material and their spatial organization within the material largely determine the properties of the material. Different classes of materials respond to external forces often in ways that are fundamentally connected to their structure. Polymer melts exhibit time-dependent viscoelastic behavior in response to external stresses. If the deformation is rapid then the response of the polymer is largely elastic, whereas for sufficiently slow deformations the response is time-dependent and dissipative. In the solid state, an amorphous polymer responds to sufficiently small forces through local relaxations of segments of the molecules. Inorganic network glass melts typically exhibit viscoelastic behavior in the vicinity of the glass transition temperature, Tg, whereas below Tg ionic entities that compose the structure undergo hopping processes in response the external perturbations. This dissertation is largely devoted to understanding the response, or relaxations, of two different classes of materials: polymer based nanocomposites and inorganic network glasses, to external periodic mechanical perturbations. Polymer nanocomposites, materials in which a polymer serves as the host for nanomaterials, may possess properties that differ substantially from those of the pure polymer. Interactions between polymer segments and the foreign particles and the geometry, size, and dispersion of the foreign particles profoundly influence the properties of the composite. Small concentrations (~ few percent) of particles of nano-scale dimensions have been shown to be particularly effective at modifying the properties of the polymer because of the large interfacial area. In this dissertation the influence of C60 fullerenes and of single walled carbon nanotubes on the dynamical mechanical and rheological properties of PS and PMMA is examined. The second problem examined was the mechanical response of inorganic network glasses based on tellurium oxide to mechanical perturbations. Often alkali oxides are included in the glass composition because they improve processability of the glass melt by decreasing Tg. Through a series of dynamic mechanical and rheological experiments, it is shown that the relaxations which characterize the response of the glass increase by up to an order of magnitude when two distinct types of alkali ions are present compared to one.Item Failure prediction for heat treated window glass(Texas Tech University, 1995-12) Bove, Paul MarkA failure prediction model for heat treated window glass has been advanced. The failure prediction model for heat treated window glass is an extension of the failure prediction methodology developed for annealed window glass. The failure prediction model for heat treated window glass relates the probability of window glass failure to the characteristics of the surface flaws on the glass and the magnitude of the induced residual compressive surface stress in the glass. The characteristics of the surface flaws can only be estimated from the results of carefully controlled window glass failure tests. Four samples of heat treated monolithic window glass are tested to failure under uniform lateral loading which increases linearly with time from the inception of loading to failure. Surface strength parameters are estimated for three samples of new heat treated window glass using the failure prediction model in conjunction with their 60-second equivalent failure strength data and the residual compressive surface stress in the glass. The magnitudes of the residual compressive surface stresses in the new heat treated window glass samples are estimated using stress measuring devices. The surface strength parameters and the magnitude of the induced residual compressive surface stress for a sample of weathered heat strengthened window glass are estimated using a statistical procedure in conjunction with the failure prediction model.Item Finite element evaluation of thermal stresses during the solidification of a glass pour(Texas Tech University, 1997-08) Li, JianminThe purpose of this thesis is to determine the temperature history, thermal stress history, and the susceptibility to fracture of glass (borosilicate) as it is poured (in a liquid state) into a canister and allowed to cool into a solid state. The general purpose finite element code ABAQUS was utilized to simulate the glass pour problem. The thermomechanical problem was solved using an axisymmetric geometry and with proper boundary conditions. Three specific problems were addressed: (1) determination of temperature history in the glass pour as it was being poured into a stainless steel canister; (2) determination of the thermal stress history in the glass as it solidifies and cools to room temperature; and (3) assessment of potential for fracture in the solidified glass as a result of the induced thermal stresses. Phase change effects were not considered in the model. In determining the temperature history of the glass pour, heat loss due to natural convection and radiation from various surfaces were considered. Once the canister was full, the temperature history was recorded. The recorded temperature history was then used to determine the thermal stress history in the glass pour. Based on the determined thermal stress history, the principal stresses were calculated and compared with the yield strength of glass to determine the potential for crack formation. When determining the thermal stress history in glass, two different sets of boundary conditions were used. The first boundary condition assumes that glass remains in contact vdth the canister wall as it cools down. The second boundary condition allows the glass to separate from the canister wall as it contracts. The fracture analysis results showed that both cases have potential for crack formation. However, the second set of boundary conditions (the set that allows the glass to separate from the canister wall) seems to simulate more realistically the possibility and location of the cracks that may form.Item Glass as a Building Element ? A Sustainable Approach: A Study of an Existing Academic Building(2011-02-22) Jori, Swapnil ShriramIn the aspects of global sustainability, buildings are known to be one of the largest energy consumers. Though sustainable building construction through technological advances is helping in achieving environment friendly buildings, a considerable amount of energy is also being consumed by existing buildings. While many factors at all different stages of building life are responsible for this, the building material is one of the most important considerations. Glass being the most sensitive building material can lead to high energy consumption in the building if used in an improper way. This study takes this factor into account, and tries to investigate the potential of energy savings in buildings through the simple and basic considerations in design. An energy analysis model of an existing academic building in College Station, Texas was developed using Design Builder computer simulation software. This model was then analyzed for the total amount of energy consumption in the base case. The existing building model was then modified by replacing the glass used for external fenestrations. Latest building codes and standards for the site location, glass properties, and parametric simulation results were taken into consideration. Again the model was simulated for annual energy consumption and the results are noted. This formed the first option for the retrofitting scenario. A hypothetical redesign scenario was also established in which the revision of building orientation was taken into consideration. The building was re-oriented to suit the weather conditions and recommendations by Advanced Energy Design Guidelines (30 percent energy savings over ASHRAE Standard 90.1-1999). The building was then simulated for annual energy consumption. A comparative analysis was performed between the three cases and the study concluded by showing 23 percent savings in the annual fuel consumption, 23.35 percent reduction in CO2 emission of the building and 25 percent reduction in annual solar heat gain under Modified case 1. Modified case 2, however, did not show any further savings due to the form of the building (almost square). However, modified case 1 settings emitted 31.8 percent more CO2 over the Energy Star office building in Texas. This methodology sets up a set of guidelines which can be followed while investigating a building for minimum annual energy consumption.Item Load resistance charts for heat-treated window glass(Texas Tech University, 2000-08) Rodriguez-Mendieta, RobertoMajor U.S. glass manufacturers such as LOF/Pilkington and PPG Industries, Inc. once supplied design recommendations in the form of glass thickness selection charts. These charts enabled users to select an appropriate glass thickness based on required design pressures and glass area. ASTM standardized these charts into a set of nominal thickness selection charts for Annealed (AN) window glass. At the same time ASTM provided strength factors to accommodate for the design of Heat Strengthened (HS) and Fully Tempered (FT) window glass. ASTM El 300 (1997) assigns HS glass a strength twice that of AN window glass having the same geometry. Similarly, ASTM assigns FT glass a strength four times that of AN window glass with the same geometry. Even though it is not clear how these factors are selected to represent the two glass types, they are widely accepted by glass designers and manufacturers over the world. While this thesis takes a more theoretical approach, it does not alter the traditional factors radically for the minimum values of residual compressive surface stresses (RCSS). However, the development of the new load resistance charts for HS and FT window glass is based on specific criteria through mainly theoretical veins, due to the paucity of experimental data for HS and FT window glass lites.Item Load resistance of trapezoidal window glass(Texas Tech University, 2001-12) Jackson, Ryan CrawfordVirtually all glass used in aircraft control tower cabs have a trapezoidal geometry. Currently, the Federal Aviation Administration (FAA) has no formal design methodology for trapezoidal window glass. The objective of the research presented herein consists of gaining insight into the behavior and load resistance of trapezoidal window glass. The research consisted of loading trapezoidal window glass specimens to fracture using a load that increased linearly with time, measuring the magnitude of loading at fracture and locating the fracture origin, and measuring the deflection of the window glass. Glass Research and Testing Laboratory (GRTL) staff at Texas Tech University tested one sample comprised of 13 monolithic glass specimens removed from Insulating Glass (IG) units and a second sample comprised of 8 Laminated Glass (LG)lites. Analyses of failure load data indicate that load resistance of the monolithic sample falls below values that current design methodology predicts. Even so, the experimental load resistance data are not significantly lower than other experimental load resistance data. Experimental load resistance data from the laminated glass sample falls in line with values predicted by current design methodologies.Item Nonlinear analysis of rectangular glass plates by Galerkin method(Texas Tech University, 1983-05) Ku, Fu-yuNot availableItem Raman studies of sol-gel confined methyl iodide(Texas Tech University, 1995-05) Bryans, Tracy ReneeItem Strength characterization of artificially weakened window glass(Texas Tech University, 1987-08) Lai, Chee KeongIn this research, four series of glass samples with different aspect ratios and thicknesses are used. The general objective of the research is to evaluate the strength of artificially degraded glass plates.