Browsing by Subject "Impact"
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Item Design and evaluation of negative stiffness honeycombs for recoverable shock isolation(2015-05) Correa, Dixon Malcolm; Seepersad, Carolyn C.; Haberman, Michael RNegative stiffness elements are proven mechanisms for shock isolation. The work presented in this thesis investigates the behavior of negative stiffness beams when arranged in a honeycomb configuration. Regular honeycombs consisting of cells such as hexagonal, square, and triangular absorb energy by virtue of plastic deformation which is unrecoverable. The major goal of this research is to investigate the implementation of negative stiffness honeycombs as recoverable shock isolation so as to better the performance of regular honeycombs.To effectively model the honeycomb behavior, analytical expressions that define negative stiffness beam behavior are established and finite element analysis (FEA) is used to validate them. Further, the behavior of negative stiffness beams when arranged in rows and columns of a honeycomb is analyzed using FEA. Based on these findings, a procedure for the optimization of negative stiffness honeycombs for increased energy absorption at a desired force threshold is developed. The optimization procedure is used to predict trends in the behavior of negative stiffness beams when its design parameters are varied and these trends are compared to those observed in regular honeycombs. Additionally, experimental evaluations of negative stiffness honeycombs under quasi-static loading are carried out using prototypes built in nylon 11 material manufactured by selective laser sintering (SLS). Energy absorption calculations conclude that optimization of negative stiffness honeycombs can yield energy absorption levels comparable to regular honeycombs. A procedure for dynamic testing of negative stiffness honeycombs is discussed. Results from dynamic impact testing of negative stiffness honeycombs reveal excellent shock absorption characteristics. FE models are developed for static and dynamic loading and the results show strong correlation with experiments. Further, temperature dependency of nylon 11 is investigated using impact tests on honeycomb prototypes. Finally, example applications utilizing negative stiffness honeycombs are discussed and recommendations are made for their refinement.Item Development of a Method for Predictively Simulating Penetration of a Low Speed Impactor into a Weak Cohesionless Soil(2013-04-29) Arrington, Dusty RaySince the horrific attacks on September 11th 2001, the United States government and research community have been focused on how to better protect US assets across the Globe. This push for safety led the research community to develop ?F2656-07 Standard Test Method for Vehicle Crash Testing of Perimeter Barriers? in 2007 which standardized the method of validating a perimeter security barrier?s ability to withstand an impact from an attacking vehicle. Many of these security barriers rely on weak cohesionless soils to stop attacking vehicles. Designers currently rely heavily on hand calculations and engineering judgment when sizing these installations. This simplified analysis is generally used because of the complex nature of these soils under impact. These soils could be simulated in advanced finite element simulations; however, traditional modeling techniques will not allow for the simulation of these complex behaviors. Due to the complex nature of these simulations, new modeling techniques need to be evaluated and their use needed to be perfected. From this, a new method for creating a predictive simulation of a low speed impactor into a weak cohesionless soil was generated. This paper presents the development of a method by which a predictive simulation was created using only standard soil tests parameters. This paper also presents measured data from physical impact tests utilized to validate the method by which the simulation was generated. Next, the paper gives a detailed comparison of the results of the physical testing and the simulated impacts. The paper finally gives a summary of where the method is successful and where it needs improvement. The resulting methodology developed in this paper defines a reasonable process for creating a predictive simulation of a rigid impactor penetrating weak cohesionless sands. This finding is validated by a reasonable correlation between the measured and simulated impact penetrations. This paper also highlights the high variability of measured penetrations when testing with these soil materials.Item Dynamic analysis of jarring process by finite-difference method(Texas Tech University, 1988-12) Chu, LifuThe mathematical model of the jarring process consists of three Interconnected sub-models. They are described In detail. Including the Initial conditions, boundary conditions and Interconnection conditions. This model resulted In three wave equations which ore too complex to be solved analytically. Therefore, finite difference methods are used to solve them. The finite element discretization, time step choice and stability are discussed. Also a brief description of the computer programs used to solve these equations Is presented.Item Dynamics of projectile impact in a granular material, and the dynamics of a single sedimenting sphere in fluid(2005) Lee, Andrew Thomas; Swinney, H. L., 1939-Item Economic analysis of the tornado impact upon two communities(Texas Tech University, 2009-05) Martinez, Maribel; Ewing, Bradley T.; Liang, Daan; Kruse, JaimeThe aftermath of hurricane landfalls like Katrina and Rita in 2005 and the tornadoes of Moore, Oklahoma (1999) and Greensburg, Kansas (2007), remind us of not only the power such systems can contain but of the great human loss, social and emotional effects, economic loss, substantial infrastructural damage, and political and environmental impacts such storms carry with them. Although the number of people killed by all disasters has been generally decreasing due to better warning dissemination, the number of people affected by disasters and costs incurred by them remains high and continues to increase. Tornado damage does produce a negative effect on some business operations; however, direct damage is only one of several factors that contribute to business loss. Damage and disruption of utilities, transportation, reduced traffic, and reduced employee productivity can all additionally incur loss that may be as large as physical losses. Research on the short-term and long-term economic effects after a tornadic event is sparse, especially for small to mid-size communities. These communities often lack the political and economic influence of larger cities when it comes to preparing and recovering from an event. Although large metropolitans may have more population at risk, large urban areas often have the resources, training, and funds to deal with hazards and disasters. This study fills a void in the literature by focusing on the impact placed on two relatively small communities of Clovis, New Mexico and Tulia, Texas after tornadoes hit on March 23, 2007 and April 21, 2007 respectively. Over 450 residential structures and 33 businesses were damaged in Clovis. In Tulia, the business district took the brunt of the storm, completely destroying 24 businesses in the town with a population of 5100. This study sets a framework for future study and focuses on the collection, compilation and documentation of engineering, atmospheric, and economic data with implications for a rapid response economic impact analysis using primary data directly from impacted businesses, higher reliability data than traditional regional studies. Such analysis provides for more accurate economic estimates that would be available to federal and state officials who decide whether to issue a Presidential Declaration and the amount of funds to disperse to a community suffering from a disastrous event based on numbers reported to the state. It is important that these smaller jurisdictions properly account for all impacts since economic impacts may be larger than direct damage impacts and may be the difference in obtaining declaration status. Additionally, local officials will be able to determine where to exert these funds in a way that would be more economically feasible and towards effective mitigation planning, paving the way towards a faster recovery and leading towards greater local sustainability. Results of the study indicated that infrastructure such as power or water services did not play a role in business disruption as power was restored quickly in both cases. The people in the community came together along with many others from surrounding communities to help in the cleanup process. Debris was cleared within the week. Those businesses that sustained major damage not only to the structure but inventory as well, took longer to recover, between two to nine months. Additionally, permanent job loss impacts estimated by the economic impact analysis show significant immediate impact to Swisher County, spiking unemployment by nearly 36% and a loss of 22 jobs. Swisher County had an estimated $1,000,000 in output impact due to the decision of Alco not to rebuild. Additionally, research showed that when businesses are hit by a tornado, some experienced demand surge. This included auto repair shops and service firms such as insurance agents. Others continued to operate or recovered quickly by changing locations or operating out of their homes. However, establishments in sectors such as manufacturing/dairy/retail sustained longer lasting periods of business interruption.Item The economic development impacts of investing in an Interstate 10 expansion project in Texas(2012-08) Evans, Stephen Daniel; Walton, C. Michael; Prozzi, JolandaTransportation planners, engineers, and administrators face the difficult tasks of prioritizing and justifying proposed investments in transportation infrastructure, particularly as government budgets tighten and alternative investments compete for public funding. One means by which professionals can prioritize and justify large transportation investments is by describing how a proposed project will impact an area’s economy in terms of creating new jobs, raising aggregate income, and increasing business revenues. The report begins by examining the general impact of transportation investments on economic development. Then it surveys various methods and tools that have been proposed for estimating economic impacts. Among these, the TREDIS economic impact model is selected and used to estimate the economic impacts of a current interstate highway project in Texas.Item Formulation and simulation of impact dynamics for multilayer fabrics with various weaves(2011-12) Shimek, Moss Evan; Fahrenthold, Eric P.; Longoria, Raul G.; Crawford, Richard H.; Traver, Alfred E.; Sepehrnoori, KamyThe high strength, light weight, and flexibility of fabric protection systems makes them the preferred solution for a number of ballistic applications. Examples include body armor, fan blade containment for jet engines, and orbital debris shielding. In general, these protection systems employ plain woven fabric, most suitable for flat or gently curved geometries. Highly curved surfaces, such as personnel extremities, may be more effectively protected using fabrics of different weaves. This dissertation presents the first numerical model developed to simulate ballistic impacts into plain, harness satin, twill, and basket weave fabrics. It extends previous work on hybrid particle-finite element methods developed for fabric modeling. The extended formulation closely replicates the tensile load response and contact-impact dynamics of highly flexible yarns, by generalizing the kinematic model and density interpolation used in previous work. The formulation has been validated in three dimensional simulations of impact experiments conducted to investigate the effects of weave type on fabric ballistic performance.Item Measuring the impact of an intensive commodity price risk management education program on agricultural producers(Texas A&M University, 2005-08-29) McCorkle, Dean AlexanderThe purposes of the study were to measure change in knowledge, adoption of practices, and economic impact, and to investigate relationships between selected personal and business parameters, and satisfaction, knowledge, adoption of practices, and economic impact of the Master Marketer program and marketing clubs. A census was attempted to collect data from the 520 Master Marketer graduates and 1,058 marketing club members. Using recommendations from Dillman (2000), data from participants were collected using two mail questionnaires. This process yielded 326 usable responses from Master Marketer graduates for a return rate of 62.7%, and 407 usable responses from marketing club members for a response rate of 38.4%. Master Marketer respondents had a statistically significant increase in selfperceived knowledge with a change in mean score of 2.06 (pre-knowledge mean = 3.33, post-knowledge mean = 5.40, where 1 = low, and 7 = excellent). Using a paired samples t-test, the 2-tail level of significance was beyond the .05 level of significance. Marketing club respondents also showed a statistically significant increase in self-perceived knowledge. Adoption of price risk management practices was measured with an adjusted response scale ranging from 0 to 12. Master Marketer respondents showed a pre-mean score of 3.15, a post-mean score of 6.61, and a change of 3.46. The 2-tailed level of significance for the overall adoption scale was less than 0.01. Marketing club respondents also showed a statistically significant increase in adoption of these practices. Economic impact in terms of change in net income was derived using respondents?? self-reported changes in commodity price received for each commodity produced, and each respondent??s typical level of production. The total farm impact had a mean of $32,288. The 2-tailed level of significance for the total farm impact was less than 0.01. The mean impact per farm of $12,361 for marketing club respondents was also statistically significant. For Master Marketer respondents, notable findings with respect to the correlation of independent variable with dependent variables was total gross revenue was negatively correlated with knowledge change. Participants who reported a large change in knowledge tended to also report a large change (increase) in time spent on marketing.Item Numerical simulations of the flow produced by a comet impact on the Moon and its effects on ice deposition in cold traps(2010-05) Stewart, Bénédicte; Goldstein, David Benjamin, doctor of aeronautics; Varghese, Philip; Trafton, Laurence; Raman, Venkatramanan; Hurley, DanaThe primary purpose of this study is to model the water vapor flow produced by a comet impact on the Moon using the Direct Simulation Monte Carlo (DSMC) method. Toward that end, our DSMC solver was modified in order to model the cometary water from the time of impact until it is either destroyed due to escape or photodestruction processes or captured inside one of the lunar polar cold traps. In order to model the complex flow induced by a comet impact, a 3D spherical parallel version of the DSMC method was implemented. The DSMC solver was also modified to take as input the solution from the SOVA hydrocode for the impact event at a fixed interface. An unsteady multi-domain approach and a collision limiting scheme were also added to the previous implementation in order to follow the water from the continuum regions near the point of impact to the much later rarefied atmospheric flow around the Moon. The present implementation was tested on a simple unsteady hemispherical expansion flow into a vacuum. For these simulations, the data at the interface were provided by a 1D analytical model instead of the SOVA solution. Good results were obtained downstream of the interface for density, temperature and radial velocity. Freezing of the vibrational modes was also observed in the transitional regime as the flow became collisionless. The 45° oblique impact of a 1 km radius ice sphere at 30 km/s was simulated up to several months after impact. Most of the water crosses the interface under 5 s moving mostly directly downstream of the interface. Most of the water escapes the gravity well of the Moon within the first few hours after impact. For such a comet impact, only ~3% of the comet mass remains on the Moon after impact. As the Moon rotates, the molecules begin to migrate until they are destroyed or captured in a cold trap. Of the 3% of the water remaining on the Moon after impact, only a small fraction, ~0.14% of the comet mass, actually reaches the cold traps; nearly all of the rest is photo-destroyed. Based on the surface area of the cold traps used in the present simulations, ~1 mm of ice would have accumulated in the polar cold traps after such an impact. Estimates for the total mass of water accumulated in the polar cold traps over one billion years are consistent with recent observations.Item Off-Road Vehicle Impact on Sediment Displacement and Disruption at Assateague Island National Seashore, Maryland(2012-08-15) Labude, BrianThe National Park Service (NPS) monitors off-road vehicle (ORV) use in National Seashores across the United States. The sediment disturbance that is caused by ORVs is believed to have a large impact on erosion (by wind or waves), which there by affects the morphology of the foredunes. With greater knowledge of ORV impacts, the NPS can better manage ORV use and minimize anthropogenic affects to the coastal environment. There remains considerable uncertainty about the disturbance and its larger-scale impact. This study quantifies the sediment disturbance made by tire tracks, as well as the tire track form, width, depth, and evolution with relation to the number of vehicle passes and location on the beach at Assateague Island National Seashore (ASIS), Maryland. To measure ORV impact, ground-based LiDAR was used to collect detailed profiles across a three by three meter test plot at each site. Based on the quantification of the displaced sediment and redistribution of that sediment from the tracks, a recommendation to the NPS can be made as to where along the beach traffic should be limited to, in order to minimize impact to the physical environment at ASIS. Tire tracks were found to widen after the first pass, as a result of the imperfections of driving. Compaction of the sediment in the center of the tire track accounts for only a minimal amount of the sediment lost from the tire tracks. Sediment removal accounted for greater than 75% of the sediment lost from the tire tracks at all sites. It was concluded that sediment removal is the most dominant factor in the creation and evolution of a tire track. The width, depth, and evolution of a tire track were also found to be controlled by the imperfections of driving. Despite the amount of sediment disturbance, it is found that there is no net downslope displacement of sediment. This conclusion counters previous ORV impact studies and suggests that ORVs are not directly responsible for beach erosion. It is also recommended that to minimize the impact of OVRs on the beach at ASIS, the NPS should limit driving to the backshore.Item One dimensional finite element model for impact and spall(Texas Tech University, 1981-08) Luo, Jiing-shinNot availableItem Parametric study of LCROSS impact plume(2013-12) Lamb, Justin Meredith; Goldstein, David Benjamin, doctor of aeronauticsIn 2009, NASA's LCROSS mission impacted Cabeus Crater near the Lunar South Pole with the spent Centaur upper stage rocket. The impact was observed by the trailing sheperding spacecraft (S-S/C) that impacted the moon 250 seconds after the Centaur impact. The main objective of the LCROSS mission was to verify the existence of water ice in the lunar regolith---the subsequent analysis of the data confirmed water ice present in the crater. The analysis of the S-S/C instrument data suggested that the plume consisted of two components: a central "spike" component and a thin, outward "cone" component. A model has been developed at The University of Texas at Austin improve the analysis of the data obtained by the S-S/C. This model is created with a free-molecular ballistic grain code that involves simulating individual regolith grains in the debris plume through grain-heating and grain-movement models and then modeling the spectral radiance properties of the grains as observed by the S-S/C. Mie scattering theory is used to model scattering and absorption of incoming solar radiation by the particles in the plume assuming they are perfect spheres. The UT LCROSS code was utilized in a parametric study that evaluated the effect of variations in assumed model plume parameters on the modeling of S-S/C UV-VIS instrument observations. The plume parameters were chosen based on the assumption that the dust plume was split into two components: a central spike and a surrounding high angle cone. The following parameters were varied: the spike and cone angles, the spike and cone grain radius distributions, and the spike mass fraction. The following parameters could be varied but were given fixed values: ice fraction between plume components, ice grain purity, albedo, and ice fraction in plume. The impact of these plume parameters upon plume brightness and blue/red color ratio was determined. Two grain models were used. In the initial grain species model all grains have a soil core surrounded by a thin ice shell. In the second, two species model two grain types were utilized: a pure ice grain component and a pure soil grain component.Item Pounding and impact of base isolated buildings due to earthquakes(Texas A&M University, 2005-08-29) Agarwal, Vivek KumarAs the cost of land in cities increases, the need to build multistory buildings in close proximity to each other also increases. Sometimes, construction materials, other objects and any projections from a building may also decrease the spacing provided between the buildings. This leads to the problem of pounding of these closely placed buildings when responding to earthquake ground motion. The recent advent of base isolation systems and their use as an efficient earthquake force resisting mechanism has led to their increased use in civil engineering structures. At the same time, building codes that reflect best design practice are also evolving. The movement of these base isolated buildings can also result in building pounding. Since base isolation is itself a relatively new technique, pounding phenomenon in base isolated buildings have not been adequately investigated to date. This study looks at the base isolated response of a single two story building and adjacent two story building systems. Four earthquakes with increasing intensity were used in this study. It was found that it is difficult to anticipate the response of the adjacent buildings due to non- linear behavior of pounding and base isolation. The worst case for pounding was found to occur when a fixed base and base isolated buildings were adjacent to each other.Item Real vs. imaginary users: measuring the impact of home movie collections on historical scholarship(2014-08) Treat, Laura Jean; Galloway, Patricia Kay; Frick, CarolineIn the past thirty years, a growing community has emerged to advocate for the preservation and recognition of home movie collections based on their historical significance. Despite the significant cost of preserving and providing access to these collections and the myriad challenges they pose to archivists and researchers, no substantive research exists that evaluates their actual scholarly use or impact. Through a publication analysis and a survey of the Association of Moving Image Archivists, I sought to determine if there is a difference between whom archivists think should be using home movie collections and who is actually them. Though my findings suggest that home movies have yet to impact the scholarly work of historians, I offer recommendations for future research and professional development that may encourage increased scholarly use as well as increased collaboration between archivists and historians.Item Tailored functional colloids and interfaces for nanoparticle impact electroanalysis(2016-05) Robinson III, Donald Arlington; Crooks, Richard M. (Richard McConnell); Stevenson, Keith J.; Johnston, Keith P; Mullins, Charles B; Shear, Jason B; Yeh, Hsin-ChihNanoparticle impact electroanalysis (NIE) is a new electrochemical method under development for fundamental physicochemical studies of single nanoparticles (NPs) and potential applications in biosensing of single molecules with ultralow limits of detection. This dissertation introduces the tailored design, synthesis, characterization, and optimization of functional materials that comprise the foundation for the NIE detection strategy of interest, which is based on the principle of electrocatatlytic amplication (ECA). The investigations presented herein focus on two materials that function as the foundation in the ECA-NIE detection strategy: 1) the ultramicroelectrode (UME) used to contact these NPs individually from solution and 2) the NPs themselves, which are the primary focus of this dissertation. The specially designed materials described have helped to overcome major fundamental limitations associated with the ECA detection strategy and thus improve critical figures of merit for NIE. In Chapter 1, the incorporation of Hg as the UME material is shown to significantly improve signal-to-noise, reproducibility, and time resolution for the NIE platform. In Chapter 2, the fundamental problem of colloidal instability is addressed and rectified by experimentally guided systematic optimization of the ECA solution conditions, in turn providing the means to properly calibrate and theoretically model NP impact events in terms of NP size and rate of impact at the UME surface. Chapters 3 and 4 highlight the synthesis, characterization, and analytical application of bifunctional catalytic/magnetic Pt-decorated iron oxide NPs for NIE. The bifunctional NPs serve as essential tools to overcome fundamental limitations of mass transport, which is achieved by physical manipulation using an externally applied magnetic field focused at the UME detection surface. The incorporation of magnetophoretically focused and accelerated NP transport results in a significantly improved limit of detection in comparison to diffusion-limited NIE strategies. In Chapter 5 we return to the study of NP aggregation kinetics with NIE and discuss mechanistic insights into the physicochemical processes that most likely influence Pt NP colloidal stability. The methodologies described in this dissertation provide an experimental blueprint to help establish a solid physical/analytical foundation of this rapidly evolving field of research.Item Wall barrier resistance to the impact of tornado-generated missiles(Texas Tech University, 1984-05) Bailey, James RobertNot available