• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 475
  • 254
  • 139
  • 90
  • 71
  • 35
  • 35
  • 10
  • 10
  • 10
  • 10
  • 10
  • 6
  • 5
  • 5
  • Tagged with
  • 1408
  • 166
  • 164
  • 101
  • 99
  • 98
  • 94
  • 93
  • 81
  • 80
  • 77
  • 77
  • 74
  • 67
  • 63
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
481

Experimentelle und Numerische Untersuchung des Kernformstofffließens

Rudert, Alexander 13 November 2009 (has links)
Die Arbeit befasst sich mit der Untersuchung des Kernformstofffließens als nichtnewtonsche Fluidströmung. Dazu werden verschiedene Formgrundstoffe und Kernformstoffe rheologisch untersucht. Als Bindersysteme kommen PUR Coldbox und Wasserglas zum Einsatz. Für diese Untersuchungen wird ein eigens für diesen Zweck entwickeltes Messgerät verwendet. Die gewonnenen Daten werden in ein numerisches Modell implementiert, welches mit den Methoden der numerischen Strömungsmechanik den Kernschießvorgang abbildet. Dabei kommt der Open Source CFD Code OpenFOAM zum Einsatz. Der Kernschießvorgang wird mit verschiedenen Kernkastengeometrien numerisch und experimentell untersucht und die Ergebnisse verglichen. Die Ergebnisse der rheologischen Untersuchungen zeigen deutlich den Einfluss der Beschaffenheit des Formgrundstoffes und des Bindersystems auf die Fließfähigkeit des Kernformstoffes. Der Vergleich zwischen Experiment und Simulation zeigt gute Übereinstimmung. Das formulierte Modell gibt die Möglichkeit, Probleme in der Kernqualität vorherzusagen.
482

Sand mining, land degradation and rehabilitation in rural areas of South Africa : a case of Mentz Village, Limpopo Province

Malebana, Dineo Sarah January 2021 (has links)
Thesis (M. Dev. (Planning and Management)) -- University of Limpopo, 2021 / Sand mining has grown popular in South African rural communities due to its increasing demand for building purposes in and around the surrounding villages as well as a source of income to the rural communities. Sand is an indispensable natural resource of any society around the world. For instance, the government has to deal with the frequent sand mining environmental effects and implement various strategies on how to deal with these effects to protect the environment. Although the National Environmental Management Act (NEMA) 107 of 1998 regulates sand mining, the illegal and unregulated rural sand mining is causing land degradation, creating unpleasant appearances, causing vulnerability to floods and pointing out the need for rehabilitation. Given the circumstances surrounding the issue of illegal sand mining in rural communities, this research is aimed at investigating the impact of illegal or legal sand mining on the environment looking at the land degradation and the importance of rehabilitating the area after use in Mentz village. The main objective of this research was to explore how sand mining causes land degradation and examining the significance of rehabilitation in sand mining. The methodology of the study was carried out using both quantitative and qualitative research design in a form of questionnaire surveys, oral interviews and field observations to collect the data. The sample was composed of the general members of the community, the chief and the sand miners. For data analysis, the study used the Statistical Package for the Social Sciences (SPSS), IBM SPSS Statistics 25. The results indicated that sand mining causes 54.76% of the land degradation in South Africa. Furthermore, the research revealed that 30.95% of the land degradation was due to deforestation and 11.90% of Mentz land degradation was caused by overgrazing. Besides, an overwhelming 76.58% of the respondents agreed that land should be rehabilitated after sand mining processes.
483

Removal of arsenic from contaminated groundwater using laterite, sand and ash: a case study in Son Dong commune, Hoai Duc district, Ha Noi

Nguyen, Quoc Bien, Tran, Hai Nam, Nguyen, Thi Hoang Ha 07 February 2019 (has links)
Arsenic (As) contaminated groundwater has been a major concern due to the negative impacts to exposed people. This research was conducted to assess and compare the removal efficiency of As from groundwater by laterite, sand, and ash. The experiment was carried out in 14 days in a household scale in Son Dong commune, Hoai Duc district, Ha Noi. Groundwater was pumped directly from a well and flowed through 20 cm (diameter) x 80 cm (length) columns. The initial As concentration in groundwater was 526 μg/L decreasing to an average of 189, 192 and 154 μg/L after being filtrated using sand, ash, and laterite, respectively. Average removal efficiency of sand, ash and laterite during the experiment was 63.3, 63.9, and 70.5%, respectively. Laterite had higher As removal efficiency may be due to higher content of goethite and kaolinite in this sorbent which resulted in better adsorption of As. The concentrations of As in the outflow water were higher than the allowable limit set by the national technical regulation on drinking water quality (QCVN 01:2009/BYT). Therefore, it requires higher volume of sorbents or additional treatment technologies for removal of As from groundwater. / Ô nhiễm asen (As) trong nước ngầm hiện nay là một vấn đề cấp bách đối với xã hội bởi những rủi ro tiềm ẩn với sức khoẻ con người. Nghiên cứu được thực hiện nhằm đánh giá và so sánh khả năng hấp phụ As trong nước ngầm của đá ong, cát và tro. Thí nghiệm được tiến hành trong vòng 14 ngày đặt tại một hộ gia đình có nguồn nước ngầm bị ô nhiễm As thuộc xã Sơn Đồng, huyện Hoài Đức, Hà Nội. Nước ngầm được bơm từ giếng và chảy qua các cột đựng vật liệu có đường kính và chiều dài lần lượt là 20 cm và 80 cm. Nồng độ As ban đầu là 526 μg/L đã giảm xuống còn 189, 192 và 154 μg/L sau khi lọc bằng cát, tro và đá ong. Hiệu suất xử lý As trung bình của cát, tro và đá ong lần lượt là 63,3, 63,9 và 70,5 μg/L. Đá ong xử lý As tốt hơn có thể do hàm lượng goethit và kaolinit cao hơn trong vật liệu hấp phụ này dẫn đến khả năng hấp phụ As tốt hơn. Tuy nhiên hàm lượng As trong nước đầu ra vẫn chưa đạt quy chuẩn cho nước uống (QCVN 01:2009/BYT). Do đó, cần tăng thêm lượng vật liệu hoặc kết hợp với các phương pháp khác để xử lý As hiệu quả hơn.
484

Gobi : Automatic sand-spreading robot / Automatiserad sandspridare för snö

Naser, Tim, Ntouvas, Stavros January 2021 (has links)
The purpose of this report was to research through the construction of a prototype the technical challenges associated with creating a robot that distributes sand on patios after snowfall. A robot that could complete this task should be able to know its position in an unknown terrain and traverse it in a predictable manner that allows for the even spread of the sand. In order to achieve stability and predictability of movement, stepper motor driven wheels were chosen as the steering method. The sand-spreading mechanism consists of a DC Motor connected to a 3D-printed disc with rectangular extrusions at its base. The wheels and chassis of the robot were likewise 3D-printed. Lastly, an Arduino MEGA board was the controller of choice. / Syftet med denna rapport var att genom konstruktionen aven prototyp undersöka de tekniska utmaningarna för att skapa en robot som distribuerar sand på uteplatser efter snöfall. En robot som kan slutföra denna uppgift bör kunna känna till sin position i en okänd terräng och färdas på den på ett förutsägbart sätt som möjliggör en jämn spridning av sanden. För att uppnå stabilitet och förutsägbarhet för rörelse valdes stegmotordrivna hjul som styrmetod. Sandspridningsmekanismen består av en likströmsmotor ansluten till en 3D-utskriven skiva med rektangulära extruderingar vid basen. Robotens hjul och chassi var också 3D-utskrivna. Slutligen var ett Arduino MEGA-kort den valfriastyrenheten.
485

Evaluation of a Particle Sampling Probe to Measure Mass Concentration in Particle-Laden Flows

Coulon, Thomas Alexander 11 May 2022 (has links)
Particle ingestion is a prevalent issue for jet engines. During operation, sand and ash particles enter the engine and can cause serious problems, including erosion and buildup of Calcia-Magnesia-Alumina-Silicate (CMAS) deposits. Analyzing the particle mass concentration of the airflow can help better understand this issue. This can best be accomplished by sampling particles with a sampling probe at various locations within an engine. The present study is a continuation of a previous study that developed and evaluated a novel sampling probe. The present study seeks to modify the probe to optimize its sampling capability, to evaluate the aerodynamics of the modified probe through Particle Imaging Velocimetry (PIV), to gain insight on its ability to sample smaller particles, to characterize the movement of larger particles as they are sampled using Particle Tracking Velocimetry (PTV), and to develop a method to physically measure particle mass concentration. To accomplish this, a free jet rig was used to create a particle-laden flow, and the probe was placed at the jet exit to sample particles. A laser and camera system were used to capture images of the probe for PIV and PTV. A particle collection apparatus was designed to collect and weigh particles captured by the probe to measure mass concentration. The PIV results indicate that the probe exhibits sub-isokinetic sampling behavior. However, the PTV results show that large particles are not affected by non-isokinetic conditions. The mass concentration measured by the probe decreases when the flow Mach number increases due to the higher flow velocity causing particles to be spaced further apart. The mass concentration measured by the probe decreases when the probe yaw angle increases due to lower projected probe inlet area. / Master of Science / Sand and ash particles are harmful to jet engines. Particle ingestion can greatly affect the useful life of the engine. Particles erode the machinery within the engine, and they also melt to form mineral deposits, all of which degrades performance. One method that is being developed to better understand this problem is to sample particles at various locations in the engine using a sampling probe. The concept of a sampling probe is simple: particles are captured by the probe inside the engine, and the particles are collected outside the engine for analysis. This would give insight on particle behavior in the engine. The present study is a continuation of a previous study that developed and evaluated a novel sampling probe. The present study seeks to modify the probe to optimize its sampling capability, to use advanced imaging techniques to characterize the movement of air and particles entering the probe, and to safely collect and weigh particles captured by the probe. A compressed air jet was used to accelerate particles and create a particle-laden environment akin to the inside of an engine. The probe was placed at the exit of the jet to sample particles. A laser and camera system were used to capture images of the probe during the particle-sampling process. A particle collection apparatus was designed to safely collect and store particles captured by the probe for weighing. The image and weight data were then used to make conclusions about the probe's sampling capability.
486

Development of a Novel Probe for Engine Ingestion Sampling in Parallel With Initial Developments of a High-speed Particle-laden Jet

Collins, Addison Scott 07 December 2021 (has links)
Particle ingestion remains an important concern for turbine engines, specifically those in aircraft. Sand and related particles tend to become suspended in air, posing an omnipresent health threat to engine components. This issue is most prevalent during operation in sandy environments at low altitudes. Takeoffs and landings can blow a significant quantity of particulates into the air; these particulates may then be ingested by the engine. Helicopters and other Vertical Takeoff and Landing (VTOL) aircraft are at high risk of engine damage in these conditions. Compressor blades are especially vulnerable, as they may encounter the largest of particles. Robust and thorough experimental and computational studies have been conducted to understand the relationships between particle type, shape, and size and their effects on compressor and turbine blade wear. However, there is a lack of literature that focuses on sampling particles directly from the flow inside an engine. Instead, experimental studies that estimate the trajectories and behavior of particles are based upon the resulting erosion of blades and the expected aerodynamics and physics of the region. It is important to close this gap to fully understand the role of particulates in eroding engine components. This study investigated the performance of a particle-sampling probe designed to collect particles after the first compressor stage of a Rolls-Royce Allison Model 250 turboshaft engine. The engine was not used in this investigation; rather, a rig that creates a particle-laden jet was developed in order to determine probe sampling sensitivity with respect to varying angles of attack and flow Mach number. Particle image velocimetry (PIV) was utilized to understand the aerodynamic effects of the probe on smaller particles. / Master of Science / Aircraft jet engines are constantly exposed to particles suspended in the atmosphere. Most jet engines contain several stages of spinning blades. The first series of stages near the front of the engine comprise the compressor, while the series towards the end of the engine comprise the turbine. Engines depend on compressor blades to add energy to the flow via compression and turbine blades to extract energy from the flow after combustion. Thus, they are critical for the successful operation of the engine. The constant impact of airborne particulates against these blades causes erosion, which alters blade geometry and thereby engine performance. Depending on the turbine inlet temperature, particles may melt and clog the cooling passages in turbine blades, causing serious damage as the blades reach temperatures above their intended operating regime. These damages inhibit the ability of the engine to operate properly and pose a serious safety risk if left unchecked. In literature, experimental engine erosion correlations and numerical models of particle trajectories through the engine have been developed; however, none of these studies collected particles directly from the compressor region of the engine. In this study, a probe was developed and evaluated for the purpose of sampling particulates between the first and second compressor stages of a Rolls-Royce Allison Model 250 turboshaft engine. The probe's efficacy and aerodynamic properties were analyzed such that the probe will provide processable data when inserted into the engine. The methods to obtain this data include particle-sampling and particle image velocimetry (PIV).
487

Charaterization of Sand-Rubber Mixture and Numerical Analysis for Vibration Isolation

Manohar, D R January 2016 (has links) (PDF)
Scrap tyres provide numerous advantages from the viewpoint of civil engineering practices. Scrap tyres are light weight, have high vibration absorption, high elastic compressibility, high hydraulic conductivity, and temperature isolation potential. Scrap tyres have a thermal resistivity that is about seven times higher than soil; they produce low earth pressure and absorb vibrations. Many new techniques have emerged with time to utilize these advantageous characteristics for practical purposes in civil engineering. Though current reuse and recovery of scrap tyres has reduced the amount of landfills, but still there is a need for developing additional practices for the reuse of scrap tyres. Moreover, most of present practices do not use its vibration absorption capacity efficiently. To use the scrap tyres as individual material or mixed with soil in civil engineering applications, the systematic understanding of static and dynamic properties of sand-rubber mixtures (SRM) are of prime importance. In the present study an attempt has been made to characterize the SRM to use them as low-cost isolation material for low-to-medium rise buildings. Proposal of this isolation system using SRM is addressed in this study in four parts; in the first part, the estimation of shear strength and volumetric characteristics of the SRM were carried out. A total of seven different rubber sizes (six sizes of granulated rubber; 2 - 1 mm; 4.75 - 2 mm; 5.6 - 4.75 mm; 8 - 5.6 mm; 8 - 9.5 mm; 12.5 - 9.5 mm and one size of tyre chips; 20 - 12.5 mm) were considered for characterizing the SRM, and the rubber size which has higher shear strength characteristics is identified as optimum size for further studies. Second part deals with the effect of reinforcement on SRM with higher rubber content (50% and 75% rubber by volume). In the third part, dynamic properties of selected SRM combination with and without reinforcement were generated from experimental studies. In the last part, the numerical analysis was carried out using finite element program Strand7 to find out optimum dimension of proposed isolation scheme and reduction of spectral accelerations. In addition, the laboratory model tests were also carried out on square footing supported on unreinforced and reinforced SRM. The relative performances of reinforcement on settlement characteristics of SRM for 50% and 75% SRM have been compared with unreinforced SRM. Engineering behaviour of SRM has been studied by considering different rubber sizes and compositions by carrying out large scale direct shear test and Unconsolidated Undrained (UU) triaxial test. The shear strength characteristics such as peak shear stress, cohesion, friction angle, secant/elastic modulus, volumetric strain, failure and ultimate strength, ductility/brittleness index, and energy absorption capacity of sand and SRM were determined. The optimum percentage rubber content based on maximum shear strength and energy absorption capacity has been arrived. The granulated rubber size (12.5 - 9.5 mm) and percentage ratio, 30% by volume is found to be optimum size and content, which gives the maximum energy absorption capacity and lower brittleness index values compared to other rubber sizes. This chapter also describes the applicability of concept of Response Surface Methodology (RSM) to identify an approximate response surface model from experimental investigations on the engineering properties of sand and SRM. The experimental data were quantitatively analyzed by multiple regression models by correlating response variables with input variables in this study. To consume more tyres in SRM, rubber mix of 50 % and 75 % mixes are studied and these SRM results in lower shear strength and higher volume change when compared to 30 % SRM. To improve shear strength and reduce compressibility, geosynthetic reinforcement study has been carried out for 50% and 75% rubber by volume. Here geotextile, geogrid and geonets were used as reinforcement and number of layers and spacing between layers were varied. Finally type of reinforcement, number of layers and optimum spacing are arrived for the optimum rubber size of 12.5 - 9.5 mm for reinforced SRM. This study found that 4 layers with equal spacing of geotextile for 50 % SRM and geonet for 75 % SRM shows better strength when compared to other combinations. Further dynamic properties such as shear modulus and damping values at different strain level are estimated for red soil, sand, 30 % SRM and unreinforced and reinforced 50 % and 75 % SRM by carrying out resonant column tests and cyclic triaxial tests. The normalized shear modulus and damping ratio curves have been developed for these materials. The experimental results indicate that, shear modulus increases for 30% rubber by volume when compared to sand, thereafter the shear modulus values decreased with a further increase in rubber content in SRM. Whereas the damping ratio increases with increasing rubber content in SRM. For sand and SRM, with an increase in confining pressure shear modulus increases and damping ratio decreases. Based on the comprehensive set of experimental results, a modified hyperbolic model has been proposed. These properties are further used in the numerical analysis to find out the effectiveness of SRM as isolation material. Numerical dynamic analysis has been carried out on a 2-D finite element model of the soil-foundation-structure system. The building model has been generated considering the typical G+2 building resting on 20 m thick soil followed by rock depth and foundation is placed at 2.0 m below ground level. The beams and columns in the superstructure are modeled using 2-D frame elements. The soil column has been modeled using 4-noded 2-D plane strain plate elements. Considering the transmitting boundary condition, viscous dampers are implemented at the base of the computational soil domain in order to mitigate the reflective effects of waves. The Newmark family method (average acceleration method) has been used to calculate the displacement, velocity and acceleration vectors. Comprehensive numerical simulations have been carried out on the soil-foundation-structure system by varying rubber content in SRM (30%, 50% and 75% granulated rubber by volume), depth and thickness of SRM around footing and considering two input earthquake acceleration time history. It was found that earthquake vibrations are considerably reduced for SRM with higher rubber content. The optimum dimension of SRM giving maximum reduction in shaking level is found to be 3B below the footing and 0.75B (where B is the width of footing) on the side of the footing. Generally, the shaking levels at different floor can be reduced by 30-50%, with the use of 75% SRM. The results also indicated that the effectiveness of proposed system would depend on the characteristics of ground motion. To study the bearing capacity of square footing on SRM, laboratory model tests were carried out on square footing supported on unreinforced and reinforced SRM. The SRM combination which have been used for numerical studies are used in this model studies to know the bearing capacity and settlement characteristics. The optimum dimension of SRM around footing has been constructed. Model tests results show that, the bearing capacity decreases and settlement increases steadily with the increase in rubber content in SRM. Addition of reinforcement to SRM significantly improved the bearing capacity and reduced settlement characteristics. Reinforced SRM may be used as an effective low cost isolation scheme to reduce earthquake vibrations.
488

Computational fluid dynamics (CFD) modelling of critical velocity for sand transport flow regimes in multiphase pipe bends

Tebowei, Roland January 2016 (has links)
The production and transportation of hydrocarbon fluids in multiphase pipelines could be severely hindered by particulate solids deposit such as produced sand particles which accompany hydrocarbon production. Knowledge of the flow characteristics of solid particles in fluids transported in pipelines is important in order to accurately predict solid particles deposition in pipelines. This research thesis presents the development of a three-dimensional (3D) Computational Fluids Dynamics (CFD) modelling technique for the prediction of liquid-solids multiphase flow in pipes, with special emphasis on the flow in V-inclined pipe bends. The Euler-Euler (two-fluid) multiphase modelling methodology has been adopted and the multiphase model equations and closure models describing the liquid-solids flow have been implemented and calculated using the finite volume method in a CFD code software. The liquid phase turbulence has been modelled using a two-equation k−ε turbulence model which contains additional terms to account for the effects of the solid-particles phase on the multiphase turbulence structure. The developed CFD numerical framework has been verified for the relevant forces and all the possible interaction mechanisms of the liquid-solids multiphase flow by investigating four different numerical frameworks, in order to determine the optimum numerical framework that captures the underlying physics and covers the interaction mechanisms that lead to sand deposition and the range of sand transport flow regimes in pipes. The flow of liquid-sand in pipe has been studied extensively and the numerical results of sand concentration distribution across pipe and other flow properties are in good agreement with published experimental data on validation. The numerical framework has been employed to investigate the multiphase flow in V-inclined pipe bends of ±4o−6o, seemingly small inclined bend angles. The predicted results which include the sand segregation, deposition velocity and flow turbulence modulation in the pipe bend show that the seemingly small pipe bends have significant effect on the flow differently from that of horizontal pipes. The pipe bend causes abrupt local change in the multiphase flow characteristic and formation of stationary sand deposit in the pipe at a relatively high flow velocity. The threshold velocity to keep sand entrained in liquid in pipe bends is significantly higher than that required for flow horizontal pipes. A critical implication of this is that the correlations for predicting sand deposition in pipelines must account for the effect of pipe bend on flow characteristics in order to provide accurate predictions of the critical sand transport velocity (MTV) in subsea petroleum flowlines, which V-inclined pipe bends are inevitable due to seabed topology.
489

Laborative Untersuchung und Bewertung des Sandkontroll- und Erosionsverhaltens von Sandfiltern für geotechnische Anwendungen unter Beachtung verschiedener Einflussfaktoren

Ochmann, Lukas 14 February 2022 (has links)
Sandproduktion ist eine große Herausforderung in vielen Tiefbohrungen. Um sie zu verhindern wurden verschiedene Methoden und Bauteilen entwickelt, die unter dem Begriff Sandkontrollmaßnahmen zusammengefasst werden. Zu diesen zählt der Einbau von Sandfiltern als Standalone Screens oder Teil eines Gravel Packs. Aufgrund der vielen Einflussfaktoren aus Geologie und Betriebsweise sind die Funktionsweise und das Versagen von Sandfiltern nach wie vor Gegenstand aktueller Forschung. Eine Möglichkeit zur Untersuchung von Sandfiltern ist die Durchführung von laborativen Experimenten. In dieser Arbeit wird die Entwicklung von zwei Versuchsanlagen vorgestellt. Die Anlagen werden genutzt, um einen neuentwickelten Wickeldrahtfilter zu untersuchen. Der Filter unterscheidet sich von bisherigen Designs durch eine Beschichtung auf der Außenseite, die, durch die Verwendung von Materialien mit großer Härte, für eine größere Erosionsbeständigkeit sorgen soll. Eine umfassende Literaturrecherche zu den Versagensmechanismen und dem Stand der Technik von laborativen Untersuchungen an Sandfiltern bilden die Grundlage für diese Arbeit. Darauf aufbauend werden theoretische Vorüberlegungen zum Erosions- und Sandkontrollverhalten von Sandfiltern dargestellt. Die Versuchsanlagen ermöglichen zum einen die Durchführung von Sand Retention Tests und zum anderen die gezielte Erosion von Filterproben mittels einer kontinuierlichen Durchströmung mit einer Suspension. Die Ergebnisse werden genutzt, um grundlegende Aussagen zum Erosions- und Sandkontrollverhalten abzuleiten. Zusätzlich wird der neu entwickelte, beschichtete Filter mit konventionellen Filtern verglichen. Aus den Ergebnissen werden Limitationen der laborativen Untersuchungen zum Sandkontrollverhalten und Auswertungsempfehlungen formuliert. Ein Unterschied im Sandkontrollverhalten zwischen beschichteten und unbeschichteten Filtern kann nicht festgestellt werden. Es wird gezeigt, dass interne Turbulenz in den Öffnungen eines Sandfilters ein wichtiger Einflussfaktor auf die Erosion mit feinen Partikeln ist. Sandfilter können an unterschiedlichen Stellen erodieren, die sich nicht alle direkt auf die Funktionalität auswirken. Der Vergleich der Ergebnisse deutet darauf hin, dass beschichtete Filter eine längere Standzeit unter erosiven Bedingungen haben, da sie an der Außenseite weniger erodieren als unbeschichtete Wickeldrahtfilter. Aufgrund der besonderen Eigenschaften der Beschichtung kommt es jedoch zu größerer interner Erosion. Die Diskussion der durchgeführten Versuche liefert zusammen mit den umfangreichen theoretischen Vorüberlegungen einen Beitrag zum Verständnis über das Versagen von Sandfiltern, insbesondere das Zusammenspiel von Erosion und Sandkontrolle. Die Untersuchungen an Proben des neuartigen, beschichteten Filters bilden den Grundstein für derzeit laufende Feldeinsätze von Prototypen.
490

Experimentellt vidareutvecklad modell för dimensionering av skadebegränsandeåtgärder mot RSV-penetration vid ammunitionsröjning / Experimentally developed model for the design of protective measures againstshaped charge jet penetration during EOD operations

Johnsson, Fredrik January 2014 (has links)
Vid röjning av RSV-ammunition saknas idag adekvat beslutstöd för att dimensionera skadebegränsande åtgärder mot jetstrålens verkan. I uppsatsen vidareutvecklas en beräkningsmodell som författaren tidigare föreslagit. Syftet är att skapa ett verktyg som kan införas i ammunitionsröjningsverksamheten. Fullskaliga skjutförsök har genomförts för att klarlägga inverkan av förhållanden som är typiska vid ammunitionsröjning; en skyddskonstruktion byggd av sandsäckar och med ett långt detonationsavstånd till röjningsobjektet. Försöksresultatet visar att den grundläggande hydrodynamiska penetrationsteorin inte är användbar för dessa förhållanden. Vidare ger sandsäckskonstruktionen signifikant bättre skydd mot jetstrålen än en homogen grusbädd. Genom störningsanalys har känsligheten hos de enskilda parametrarna i beräkningsmodellen för verksamhetstypiska fel utretts. Härefter har Monte Carlo-simulering använts för att analysera den sammanlagda inverkan som dessa fel kan ge. Resultatet har legat till grund för att bestämma modellens säkerhetsmarginal. Militär nytta innebär att modellen skall kunna tillämpas fältmässigt, med korta tidsförhållanden och utan tillgång till avancerade beräkningshjälpmedel. Detta har lett fram till att ett enkelt diagram inkluderats i det kompletta dimensioneringsverktyget. Verktyget föreslås införas i regelverk och utbildningssystem för att avhjälpa den brist som råder idag. / During the clearance of shaped charge ammunition, explosive ordnance disposal (EOD) personnel lack adequate means for the design of protective measures against the jet. In this thesis a calculation model, previously suggested by the author, is developed further. The aim is to create a tool that can be applied to EOD operations. Full-scale experiments have been conducted to clarify the effects of conditions that are typical for EOD operations: protective measures built from sandbags with a long standoff distance to the ordnance. The results indicate that the hydrodynamic penetration theory is not suitable for these conditions. Furthermore, a sandbag construction provides significantly better protection against the jet than a homogeneous gravel construction. By disturbance analysis, the sensitivity of the individual parameters in the model is studied for typical errors. Subsequently, Monte Carlo simulation has been used to analyse the effect these errors can cause. The simulation results have then been the used to determine the model´s margin of safety. Military utility implies that it should be possible to use the model under field conditions, with limited time frames and without access to advanced calculating means. This has resulted in a simple diagram included in the comprehensive design tool. It is proposed that the tool is implemented in regulations and curricula in order to remedy today’s lack of decision support.

Page generated in 0.0315 seconds