Dissertations / Theses on the topic 'Sealing'

Electrosurgical vessel sealing devices have been demonstrated to reduce patient blood loss and operative time during surgery. Whilst the benefits of such devices are widely reported there is still a large variation in the quality of the seal produced, with factors such as vessel size known to effect seal quality. The study aimed to investigate parameters affecting device performance and improve the seal quality. The burst pressure test was used to assess the seal quality and tissue adhesion was measured using a peel test. Additionally histology techniques were used to quantify vessel morphology and found that with an increase in elastin content there was a reduction in seal quality. A number of device modifications were made, testing a selection of non-stick coatings and surface features of the shims. No coating reduced the level of tissue adhesion to the device, but results found that with a greater level of adhesion there was a reduction in seal quality. Considering the different surface features one design, a combination of longitudinal and transverse grooves, resulted in a seal failure rate of 0.0%, a significant improvement in device performance. Two FEM’s were produced to further investigate the device modifications; one in FEBio investigating the mechanical aspects of vessel sealing and the second a multiphysics model to investigate the thermal aspects of vessel sealing. Results from both FEM’s showed a difference in shim performance, with the addition of surface features effecting the stress distribution within the vessel wall and the heat distribution. Additionally DIC was used to capture the vessel sealing process, with results showing each seal was produced in a different way with different levels of tissue contraction. Research conducted demonstrated a number of significant relationships between seal quality and vessel properties, but did not find an explanation for all variation occurring.

A bentonite grouting technology has been developed to meet the requirements of fracture sealing for nuclear waste isolation and environmental engineering. The work reported presents an experimental evaluation of the performance of the bentonite fracture sealing in densely welded tuff. Included are the study of grout stability and resistance to erosion, theoretical and numerical analyses of the grout penetration process, pressure distribution in the fracture during grouting, grout delivery distance, breakthrough pressure and rheological characterization. Bentonite suspensions with solids content of 18, 20 and 22% by weight have been injected into single fractures in rock samples at 0.07 to 3.45 MPa pressure. Bentonite grouting reduces the fracture hydraulic conductivity by 7 to 9 orders in magnitude, to the level of 10⁻⁷ to 10⁻⁹ cm/s. Grout stability and erosion have been studied with long-term flow testing at up to 121 kPa hydraulic pressure. After 1,000 to 5,000 hours of flow testing, at pressure gradients of up to 91 cm/cm, the hydraulic conductivity of the grouted fracture does not increase with test time. The hydraulic conductivity of the grouted fracture decreases with increasing pressure gradient up to the wash-out pressure. Analytical solutions have been derived for pressure distribution during grouting in wedge shaped fractures and in fractures with constant aperture. Influence factors on pressure distribution in a fracture have been identified. They are yield stress, fracture shape, original aperture, deformation properties of the rock mass and the fracture, mixing of air in a grout and sample size. A mathematical solution of grout delivery distance under a given injection pressure has been developed. The breakthrough pressure has been studied, based on the mechanical deformation of the fracture applied by a normal stress across the fracture and by the grout pressure within the fracture during grouting. Results indicate that bentonite grouting is a promising fracture sealing technology. Bentonite grout has great hydraulic conductivity reduction and chemical physical stability. Some disadvantages of bentonite grout have been identified, such as the formation of hydraulic fractures in the grout and the washing away of grout particles when the applied pressure gradient is high enough.

Leakages from seals are one of the important factors that are taken into consideration while designing any machining element. This is because leakages can affect the performance of any component and can also turn into a catastrophe. If looked into it, many parameters can be pointed out that can enhance leakages within the system, some of them may be pressure, temperature, clamping force and bolt distance etc. But the main parameter is the surface roughness, higher the roughness more the leakage and vice-versa. Thus, in this thesis an attempt has been made how the surface roughness can affect the performance of the sealing concept for metal bounded gasket with above four mentioned parameters. Also how leak proof surface can be defined using standard tribological parameters is the aim of this thesis. This report includes the results for methodologies implemented during the thesis and track down the leakages. The leaked surfaces were carefully studied and analyzed using different standards compared with the non leaked surfaces’ roughness parameters.
Läckagerisk från tätande förband är en av de viktigaste faktorerna som beaktas vid utformning av konstruktionsartiklar. Detta på grund av att konsekvenserna kan bli förödande. Det tätande förbandet påverkas av många olika parametrar såsom till exempel tryck, temperatur, klämkraft, skruvavstånd och val av packning. En viktig faktor är ytans beskaffenhet; Generellt läcker en grov yta och vågig yta mer än en fin och plan yta. Således har i denna avhandling ytans beskaffenhet studerats tillsammans med en packning av typen metallburen gummipackning för att påvisa täthetfunktionen som en funktion av tryck, temperatur, klämkraft och skruvavstånd. Denna rapport innehåller resultat och analys av olika standardmetoder för de ytor som ingick i utredningen.

Aggregate breakdown is an important process controlling the availability of fine soil material necessary for structural sealing of soil surfaces under rainfall. It may be caused by slaking resulting from rapid soil wetting and by physical dispersion resulting from direct and indirect energetic raindrop impacts. Relationships have been proposed by others predicting steady infiltration rate and saturated hydraulic conductivity from final aggregate size following high energy rainfall on initially dry, uncovered soil surfaces. Under these extreme conditions, both rapid wetting and energetic raindrop impact result in maximum aggregate breakdown and surface sealing. Knowledge of the relative importance of these two agents under less severe conditions and knowledge of how increased aggregate stability due to conservative soil management may ameliorate them should improve prediction and management of aggregate breakdown and surface sealing. ¶ This study has isolated and quantified effects of rapid soil wetting and energetic raindrop impact on aggregate breakdown and surface sealing. Simulated rainfall was applied to re-packed soils from differing tillage treatments on light textured soils from near Cowra and Condobolin in New South Wales, Australia. Aggregate breakdown was assessed using aggregate size distribution, determined by wet sieving and summarised by a range of statistics. The degree of breakdown was assessed after 66 mm of simulated rainfall whilst the rate of change in aggregate size distribution was assessed by sampling after 5, 10, 15, 30 and 60 mm. The degree of surface sealing was assessed using final surface hydraulic conductivity after 66 mm rainfall calculated from inferred infiltration and measured sub-seal soil water potential. The rate of surface sealing was assessed prior to ponding using cumulative rainfall volume at ponding and throughout the post-ponding phase by decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. Two levels of raindrop kinetic energy flux and three wetting treatments were used to isolate effects of these agents of aggregate breakdown and surface sealing. ¶ Significant surface aggregate breakdown was observed when either rapid soil wetting or highly energetic raindrop impact were allowed to occur. The majority of the data suggest a negative interaction between the two agents. When soil was initially dry rapid soil wetting was the dominant agent causing rapid aggregate breakdown, generally within the first 5 mm of rainfall. When rapid soil wetting was prevented by tension pre-wetting, energetic raindrop impact was the dominant agent and was able to cause aggregate breakdown of an almost equivalent degree. This breakdown occurred over a period lasting for up to 30 mm of rainfall. In contrast, the rate and degree of surface sealing were influenced primarily by raindrop kinetic energy with highly energetic impact leading to significant surface sealing, irrespective of soil wetting. For the soils studied, it was concluded that structural sealing of surface soil, could be significantly reduced by protecting the soil surface from energetic raindrop impact but that prevention of surface aggregate breakdown required amelioration of both processes. ¶ In addition to the negative interaction referred to above, a positive interaction was observed whereby energetic raindrop impact occurring concurrently with rapid soil wetting caused a greater degree of aggregate breakdown and a greater degree of surface sealing than energetic raindrop impact occurring subsequent to rapid soil wetting. The effect on surface sealing may be explained by the effect of lower sub-seal water potential that necessarily results from initially dry soil condition required for concurrent rapid wetting. However, the effect on aggregate breakdown remains unexplained. ¶ Notwithstanding the above, permeability was reduced under high kinetic energy rainfall even when soil wetting was reduced to very slow rates by tension pre-wetting. Likewise, surface sealing did occur under low kinetic energy rainfall for the least stable soil following rapid soil wetting. It was concluded that threshold soil wetting rates and threshold rainfall energy levels, proposed by others, are either not applicable to these soils or are negligible. ¶ The rate and degree of aggregate breakdown was also dependent on the soil with the Cowra soil being more stable than the Condobolin soil. Greater aggregate stability brought about by conservative tillage treatments at both soil locations retarded and reduced surface sealing. Unvalidated simulation modelling was used to illustrate possible effects for the soil water balance. In contrast to the conclusions of Loch (1994b), that were based on soils throughout eastern Queensland, the soil water balance simulations predicted that the residual benefits in ameliorating surface sealing resulting from improved aggregate stability could significantly reduce point runoff under the lower intensity winter rainfalls experienced in southern New South Wales. ¶ Limited testing with Condobolin soil following tension pre-wetting showed that rainfall intensity, varying over the range from 16.5 to 66 mm h-1, had little effect on the decline in surface hydraulic conductivity as a function of cumulative rainfall kinetic energy. This contrasts with greater seal permeability under higher rainfall intensities observed by Romkens et al. (1985) and others. It is proposed that an alternative explanation exists for the observations of Romkens et al. based on reduction in seal permeability due to lower sub-seal water potential under lower intensity rainfall. ¶ Post-ponding reduction in K[subscript sat] under high kinetic energy rainfall exhibited exponential decline as a function of cumulative raindrop kinetic energy as proposed by Moore (1981b). However, inferred rates of decline prior to ponding were more rapid than measured post-ponding rates suggesting that infiltration models using only a single exponential rate of surface K[subscript sat] decline based on post-ponding measurements may be in error. Potential for error is greatest at early times for loose soil that is highly susceptible to sealing. ¶ Pre-ponding decline in surface aggregation was also relatively more rapid than post-ponding decline. This discrepancy was evident irrespective of soil pre-wetting. From this it was concluded that the more rapid initial aggregate breakdown and surface sealing was due, at least in part, to processes other than aggregate slaking due to rapid soil wetting. An explanation has been proposed as follows. Raindrops initially fall on aggregates that have not been subjected to rainfall and therefore each drop has the capacity to cause greater aggregate breakdown than subsequent raindrops that fall on aggregates or soil fragments that have been strong enough to survive preceding rainfall impacts. Such a mechanism could provide an alternative explanation of the findings of Baumhardt et al. (1991) who found that less cumulative raindrop kinetic energy was necessary to achieve a given reduction in surface conductance when the cumulative energy was supplied through lower energy drops. ¶ Relationships predicting rates of surface sealing using aggregate breakdown under rainfall and aggregate stability were evaluated. Post-ponding infiltration rate and surface K[subscript sat] were related to aggregate size by exponential functions. The proportion of surface aggregates less than 0.125 mm in diameter provided slightly more consistent relationships. Parameters of fitted relationships differed among wetting pre-treatments suggesting that the influence of sub-seal water potential on surface K[subscript sat] must be considered whenever such relationships are developed or applied. Aggregate stability determined by wet sieving was related to rainfall volume required for ponding, final K[subscript sat] and final aggregate size but only for initially dry soil suggesting that such relationships may be unique to the rainfall, soils and flow conditions used to develop them. ¶ This study has established the relative importance of rapid soil wetting and energetic raindrop impact in both aggregate breakdown and surface sealing over a range of antecedent soil water and rainfall conditions. It has quantified the effectiveness of culturally induced aggregate stability in ameliorating effects of these two important agents and illustrated the potentially significant consequences for the soil water balance. It has quantified temporal patterns of surface sealing and aggregate breakdown and proposed an alternative mechanism explaining more rapid aggregate breakdown during the initial stages of rainfall. It has identified possible explanations for effects of rainfall intensity on surface sealing observed in other studies. It has also partially evaluated a mechanism proposed to explain important effects of subseal water potential on seal permeability found in this and other studies. These significant findings have been used with the findings of other studies to amend the conceptual model proposed by Le Bissonnias (1990). The amended model gives a more complete description of the relationships between parameters and processes determining aggregate breakdown and structural surface sealing under rainfall.

This thesis is concerned with the development of cold sealing treatments for porous anodized aluminium. The need for such treatments arises because of the need to conserve energy resources and the rapid rise in energy costs over recent years. The extensive literature has been reviewed with special emphasis on recent studies of chemical/cold sealing processes. The review has considered both theoretical aspects, practical considerations of pore sealing and the substantial patent literature. It is shown that: (a) virtually all cold sealing solutions are based on nickel fluoride and operate in a temperature range of I5-60oe for 5-35 minutes and at a pH of 5.0- 6.5; (b) anodized aluminium sealed in the above solution(s) can not be tested for seal quality immediately. Original research data has been obtained by studying the nickel fluoride solution. A study of the ageing phenomenon was carried out An additional process after cold sealing namely 'post-treatment' was considered. Once these criteria for good sealing were established the next stage was to study the effect of additives in the nickel fluoride cold seal bath. As the importance of a surfactant in cold seal baths was suggested by one of the patents and claimed to be crucial for successful sealing, various types of surfactant such as ionic and nonionic were studied. Various analytical techniques and seal quality tests were used in studying the mechanism of nickel fluoride cold sealing and a new mechanism of cold sealing was proposed. \ Studies were carried out using other metal ions than nickel including copper, cobalt, zinc and zirconium with fluoride. Most were used at room temperature bearing in mind the need to save energy. It was found that the nickel fluoride cold sealed finishes performed well with ageing. However, depending on the test method used, sufficient ageing (from 5 hours to 28 days at room-temperature) must be allowed prior to carrying out seal quality tests which are designed for conventional hydrothermal sealing. Accelerated ageing by post-treatment was found to improve substantially the seal quality of anodized aluminium. It was found that the degree of sealing depends on the method of post-treatment carried out. The study of surfactant in cold seal baths showed that seal quality is marginally improved with the addition of surfactant and depends on the type and concentration of surfactant used. Amongst the alternative metal fluorides examined, copper, zinc and cobalt resulted in partial sealing whereas zirconium produced a good seal quality superior to nickel fluoride and hydrothermal sealing in terms of acid dissolution and corrosion tests. However, it produced a silvery white appearance and high admittance value. Such problems were reduced by using potassium fluorozirconate.

This thesis is based upon one project, STEP (Sealing Technology – Enhanced Properties), inside ABB Corporate Research, Sweden, which is aiming to study the sealing technology of robotic implementation by a scientific/systematic approach. Nowadays the radial lip seal can be found in many fields such as automobiles, aero-planes, and marines, etc., and they have evolved into different designs and materials for the past several decades. Most of them are designed for conventional applications like cars, in which the shaft usually works in continuous rotary motions, and with such conditions lip seals could normally function well due to the sealing mechanism. However, regarding the robotic application, in which the shaft typically works in bi-directional and intermittent motions, the lip seal may not perform ideally and sometimes cause additional leakage. Hence, this thesis is mainly focused on an experimental approach to study the lip seal performance with controlled parameters, especially the robotic motion, together with other parameters, such as oil, temperature, pressure, etc. The work includes literature survey of lip seals, specifying the test rig, building the test rig, developing a leakage detection system, carrying out benchmark tests and seal tests with different robotic motions.
Detta examensarbete är baserat på ett så kallat STEP-projekt (Tätningsteknik – förstärkande egenskaper), inom ABB Corporate Research i Sverige, med syftet att studera tätningsteknik för robottillämpningar på ett vetenskapligt/systematiskt sätt. I dagsläget används radiella läpptätningar inom många områden, såsom fordons-, flyg- och fartygsindustri. Under de senaste decennierna har den vidareutvecklats och är nu gjord av flera olika material. De flesta är utformade för konventionella tillämpningar, som exempelvis fordon. Där arbetar axeln vanligen imedkontinuerligt roterande rörelser, och vid sådana förhållanden kan läpptätningar normalt fungera väl. Men när det gäller robottillämpningar, där axeln typiskt arbetar i dubbelriktade och intermittenta rörelser, fungerar läpptätningen inte idealt och kan även ge oönskat läckage. Detta examensarbete är fokuserat på att utveckla en experimentell metod för att studera läpptätningars prestanda med väl kontrollerade parametrar, såsom oljans egenskaper, temperatur, tryck, o.s.v. I arbetet ingår litteraturstudie av läpptätningar, specificering av testrigg, byggande av testrigg, utveckling av ett system för att detektera läckage, utförande av benchmark-tester, samt tätningsprov för olika robotrörelser.

This thesis describes the design, development, and evaluation of a novel "self-sealing" suction technology for grasping. As humans desire robots capable of handling an increasingly diverse set of tasks, end effectors that are able to grasp the widest possible range of object shapes and sizes will be needed to achieve the desired versatility. Technologies enabling the exertion of local pulling contact forces (e.g. suction) can be extraordinarily useful toward this end by handling objects that do not have features smaller than the grasper, a challenge for traditional grippers. However, simple operation and cost effectiveness are also highly desirable.

To achieve these goals, we have developed a self-sealing suction technology for grasping. A small valve inside each suction cup nominally seals the suction port to maintain a vacuum within the system. Through the reaction forces of object contact, a lever action passively lifts the valve to engage suction on the object. Any cups not contacting the object remain sealed. In this way, a system with a large number of cups may effectively operate using any subset of its cups, even just one, to grasp an object. All cups may be connected to a central vacuum source without the need for local sensors or powered actuators for operation, forming a simple, compact, cost effective system.

This thesis begins with the detailed design and analysis of the self-sealing suction technology. An extensive evaluation of the technology's robustness and performance demonstrates its features and limits. This includes self-seal quality and leakage, object seal and reseal, cycle performance, and normal and shear force-displacement, among other characterizations. It then describes the development of several devices utilizing the technology. The potential impact of the technology is highlighted through applications of human-controlled, robotic, and aerial grasping and perching. Finally, mathematical tools are developed to analyze potential grasps developed using the technology.

A new fracture grouting technology has been developed to meet the requirements of high-level nuclear waste isolation. Bentonite fracture grouting tests are performed on a fracture model, made of circular acrylic plates with outer diameter of 30 cm and a central injection hole of 2.5 cm diameter. Suspensions with bentonite concentration of 9% to 31% have been injected into fractures with apertures of 9 to 39 microns under injection pressures less than 0.5 MPa. After grouting, the hydraulic conductivities of the fractures are reduced from the 10-1 to the 10-5 cm/s level. When the suspension is thin enough and the fracture is very small, channeling develops in the grouted fractures. Preliminary results indicate that the permeability of a grouted fracture does not increase with time in 125 days. The flow properties of bentonite suspensions, viscosity, shear stress, yield stress and gelation, are investigated. Water flow through ungrouted fractures and movement of water in bentonite grout are studied.

With ever growing demand on turbine manufacturers to over higher efficiency and lower operational costs, new modern seals must be able to withstand higher temperatures, pressures and shaft speeds but at the same time efficiently restrict flow at peak and transient load conditions and withstand abrasion, erosion, oxidation and depositions. This work investigates an alternative seal design, the fluidic seal, which could satisfy the demands of new seal designs. Fluid seals use a jet inclined upstream in direction of the leakage flow relying on the momentum exchange to block or reduce the leakage flow. Theoretically, fluidic seals could be implemented on any location where other seal designs are considered or installed. This work concentrates on fluidic seal design implemented between rotor shroud and housing of the steam and gas turbines. Numerical, analytical and experimental investigations were carried out to explore the fundamental principles of fluidic sealing, showing a possible leakage reduction of up to 40% compared to base configuration. Subsequently these principles were used to develop a fluidic seal on a small scale turbo expander unit.

This thesis presents the background, methodology, and results of an experimental study of the roles of stress, fault zone micro-structure, and environmental conditions on fault sealing. Synthetic fault gouges were tested in a suite of controlled experiments designed to elucidate the effects of a range of physical, structural, and chemical parameters on gouge reactivity. The experiments began with a series of ‘batch’ tests, designed to calibrate the purely chemical reactions. These were followed by a series of hydrostatic and non-hydrostatic pressure tests, designed to investigate the effect of burial depth and tectonic stress (confining pressure and deviatoric stress). The latter suites of experiments were conducted using a new experimental rig, designed and built specifically for this study. Each experiment used either a controlled size fraction, or a bulk mixture of particle sizes produced by crushing a rock sample to form a synthetic gouge. Highly reactive ultra-fine particles were removed to allow more accurate measurement of gouge surface area and hence reaction rates. Dissolution and precipitation rates were determined for each experiment by analysing dissolved silica concentrations of the pore fluids, using High Performance Liquid Chromatography, and applying them to a kinetic model. The non-hydrostatic tests also employed new apparatus that allowed the simultaneous measurement of fault-normal permeability and compaction throughout each experiment. The observed reaction rates have a strong dependence on temperature, particle size distribution, and pressure, in decreasing order of influence. This is consistent with field observations from a range of hydrocarbon reservoir rocks around the world. Theoretically, the finer particles would be expected to have higher specific surface energies and greater total reactive surface areas, and hence faster reaction rates. This has been confirmed by the results.

The door closing action is a recurrent situation when using a vehicle, and its sound is therefore a common sensation, which would elicit pleasant feelings. Sensory pleasantness is an important aspect in terms of customer’s perspective, and it can be a contributing factor when deciding to buy or not a specific vehicle. The first contact between a prospective customer and the automobile usually happens in car salons or at the car retailer. The initial impression of the vehicle might be sight-based, and the door may commonly be the first physical contact. Depending on the car brand and type, doors differ in terms of mass, structure, dimension. Furthermore, there are differences regarding the latching system and the door sealing structure, in terms of material and construction. The closing sound produced when slamming the door is related to all these parameters. Auditory pleasantness can be described by characteristics of the sound that are described through psychoacoustics. Loudness, sharpness, roughness, and tonality are important auditory parameters to objectively describe this complex sensation. The aim of car doors would be to generate an enthusiastic, low-pitched, and saturated sound, which would elicit feelings of solidity, robustness, and security. On the other side, a metallic, high-pitched, fragmented sound could be a source of annoyance and produce feelings of insecurity and cheap vehicle.The present work aims to provide a broad picture on the mechanics and acoustics of door closing for automobiles. In specific, the closing sound was evaluated in relation to the door gaskets and their sealing performance over time. The sealing performance was analyzed in energy and force terms. The door closing motion was studied as a quasi-static problem, as well as a dynamic problem, where the former is related to the latching capability of the door, the latter is connected to the slamming action. The measurement results include the sealing performance trend from fresh to aged gaskets. From these measurements, the rubber non-linear behaviour could then be evaluated from a sound quality perspective. The acoustic analysis revealed inconsistencies of the psychoacoustic parameters in the description of the hearing sensations. Spectral analysis was also implemented to capture the door closing phenomenon, and the Wavelet transform emerged as the method with the highest resolution in the description of the sound wave progression.Several measurements were performed in order to assess all the established points, and methods were implemented for the sealing stiffness analysis and the acoustic analysis. The severe transiency of the door closing event was put in evidence. The stiffness analysis method showed also potential in helping to adjust the end of line tuning of the vehicle. Finally, benchmarking was included in the project, which enabled comparisons with competitor cars.
Dörrstängning är en återkommande händelse när ett fordon används, och ljudet bör därför ge ett positivt intryck och korrekt information till brukaren. Ett behagligt intryck är en viktig aspekt ur kundens perspektiv och kan vara ett var flera bidragande faktorer när beslut tas om att köpa eller inte köpa ett fordon. Den första kontakten mellan en potentiell kund och bilen sker vanligtvis i bilsalonger eller hos bilhandlare. Det första intrycket av fordonet kan vara visuellt, och dörren är ofta den första fysiska kontakten. Beroende på biltyp och fabrikat skiljer sig dörrarna åt när det kommer till massa, struktur och dimensioner. Dessutom kan det finnas skillnader i låssystem och dörrtätningskonstruktion såsom i både material och utformning. Stängningsljudet som uppstår när dörren slås igen är relaterat till alla dessa parametrar. Ett ljuds upplevda behaglighet i det beror på ljudets egenskaper, som beskrivs med hjälp av psykoakustik. Ljudstyrka, skärpa, råhet och tonalitet är viktiga auditiva parametrar för att objektivt beskriva detta komplexa intryck. Målet med bildörrar bör vara att generera ett dovt och mättat ljud, för att framkalla känslor av soliditet, robusthet och säkerhet. Å andra sidan kan, ett metalliskt, högfrekvent och skramligt ljud vara en källa till irritation och ge känslor av osäkerhet och låg kvalité.Syftet med detta arbete är att ge en övergripande beskrivning av dörrstängning och akustiken kring detta. I synnerhet utvärderades stängningsljudet i förhållande till dörrpackningarna och deras tätningsprestanda mätt över tiden. Tätningsprestanda analyserades i energi- och krafttermer. Dörrens stängningsrörelse studerades både som ett kvasistatiskt problem och som ett dynamiskt problem. Det förstnämnda är relaterat till dörrens låsningsförmåga, medan det sistnämnda är kopplat till smällar i dörren. Mätresultaten visade hur tätningsprestandan förändras över tiden. Gummits icke-linjära beteende har också utvärderats med ett ljudkvalitetsperspektiv. En spektralanalys genomfördes av ljudet från dörrstängningar och Wavelet-transformen visade sig vara den lösning som gav bäst kvalitet. Flera mätningar utfördes för att bedöma alla fastställda punkter och metoder infördes för analysen av tätningens styvhet och för den akustiska analysen. Den kraftiga transiensen i dörrstängningen kunde ses i resultaten. Styvhetsanalysen visade även hur den utvecklade metoden skulle kunna bidra till att justera fordonets end-of-line inställningar. Slutligen ingick benchmarking i projektet vilket möjliggjorde jämförelser med konkurrentbilar.

This study investigates the potential relation of seismic anisotropy measured by surface seismic and the sealing potential of the shale sequences. Two case studies analyzed such a relationship. The Gippsland basin and Exmouth sub-basin are both hosts to prolific hydrocarbon resources and offer plenty of seismic data and sealing potential measurements. Weak anisotropy parameters extracted from carefully reprocessed seismic data show in both cases a positive correlation between sealing capacity and anisotropy of the shale.

In the rapidly evolving organisational landscapes of today, the quest to grow or sustain competitive advantage demands that organisational practices become more innovative, hence innovative advantage. Globalisation and technological advances drive the necessity for innovation within organisational contexts and the resultant rapid pace of change demands that organisations adopt an intrapreneurial orientation to accommodate this need for innovation. South African organisations, in particular those within the automotive sector, are faced with both unique opportunities and threats as a result of the increased impact of globalisation and the resultant open markets in the post-apartheid era. Programs offered by governmental institutions for this industry sector, such as the Motor Industry Development Programme (MIDP), as well as widely promoted systems such as those engendered by continuous improvement and benchmarking to achieve excellence, are successful only in attaining uniformity and incremental improvements and one-dimensional thinking methodologies. The quest for innovation advantage requires increased creative activity to assist individuals within these organisations in adopting an intrapreneurial outlook to provide proactive solutions. The literature survey has revealed that top-down controls and centralised decision-making as provided by corporate entrepreneurship, is the antithesis of intrapreneurship. Intrapreneurship is thus an autonomous process. Federal Mogul Sealing Systems (FMSS), an automotive component manufacturer within the Eastern Cape served as the basis for this study. A detailed literature review was conducted and a questionnaire was drawn up and distributed in an attempt to assess the three prevalent elements for the creation of innovation advantage through intrapreneurship as reviewed in the literature survey. The three elements were: individual intrapreneurial traits, organisational barriers and enablers of intrapreneurship and the influence of precipitating events on intrapreneurship. The research was conducted and recommendations were made based on the objectives of this study in relation to the organisation under study, FMSS.

Wear and friction tests were conducted on a rotational tribometer to identify material couples for compression seals and chamber coatings to extend the service life of the Pivotal Engine™. Potential materials were identified based on reports in the literature of successful use in similar environments. From the rotational tribometer tests, the best material couple was found to be reaction bonded silicon nitride against a Sulzer Metco F4301 plasma sprayed coating followed by a Total Seal TiN coated seal against the F4301 coating. However, the performance predicted by the rotational tribometer was not realised in a fired engine, where the TiN coated seal wore almost as fast as an uncoated seal. This discrepancy was due to the large differences in operating conditions between the rotational tribometer and the fired engine, particularly the reciprocating motion of the engine. The different operating conditions mean that the results from the rotational tribometer have little or no relevance actual performance in the engine. To overcome the limitations of the rotational tribometer a reciprocating tribometer was designed and built. The performance predicted by the reciprocating tribometer was much closer to the observed wear rates from the engine, particularly with the Total Seal TiN coated seals. Some of the results from the reciprocating tribometer were a direct-contradiction to those obtained on the rotational tribometer. When tested on the rotational tribometer the nitrided stainless steel seal wear rate was lower than that of the Mazda cast iron seal. However, on the reciprocating tribometer the Mazda cast iron seal had a lower wear rate than the nitrided stainless steel seal. From the testing conducted on the reciprocating tribometer the best material couple was found to be Total Seal TiN coated seals on the F4301 chamber coating. However, this material couple cannot be recommended to increase the seal life in the Pivotal Engine™ because at the conclusion of a twenty hour test the Total Seal TiN coating had worn through to the substrate. In addition to testing different materials, different oils were tested while keeping the wear couple constant. The oil that offered the best wear protection to both the seal and chamber coating was Castrol A747. These tests showed that different oils have as much effect as different materials. Even with the best material combinations (Total Seal TiN seal, F4301 chamber coating) the seal wear rates in the Pivotal Engine™ are much higher than would be expected in other engines. This leads to the hypothesis that the origin of high seal wear in the Pivotal Engine™ is not due to material properties, but to design issues. The most likely problem is distortion of the chamber, which causes high localised seal loadings, and in turn causing high seal wear.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.
This thesis was scanned as part of an electronic thesis pilot project.
Cataloged from PDF version of thesis
Includes bibliographical references (p. 83-84).
In a gas turbine engine, ingestion of hot gas from the flowpath into the gaps between the turbine rotor and stator can lead to elevated metal temperatures and a deterioration of component life. To prevent ingestion, bleed air from the compressor is used to "purge" the rim seal cavities. Establishing a quantitative understanding of the wheelspace and rim cavity flow processes driving ingestion is critical to optimizing seal design and minimizing the associated performance penalty. A computational model of the wheelspace that does not limit the spatial or temporal scales of flow processes is formulated. This allows the assessment of the response of the wheelspace to external stimuli set up by the turbine main flow path, and the development of causal links between flow processes and their drivers. Varying the axisymmetric turbine flowpath pressure on a quasi-steady basis when the purge flow supply seal is choked has no impact on ingestion; the pressure field in the wheelspace merely scales with the flowpath pressure, leaving the flow structure unchanged. Introducing circumferential variation in the external pressure field can, however, lead to ingestion with the ratio of disturbance wavelength to the trench depth emerging as a key parameter. Varying rotational speed alone does not drive ingestion as a stagnation point is formed on the outer shroud that is ingestion resistant. It is shown that excitation at frequencies corresponding to the natural modes of the wheelspace system can lead to large responses in pressure and seal flow rate, with the seal reduced frequency appearing as a characterizing parameter. The existence and parametric dependence of these modes is further assessed through a small disturbance flow analysis. A generalized small disturbance flow analysis is formulated that provides a direct enumeration of the key characterizing parameters.
by Peter T. Catalfamo.
S.M.

Dehydration of bentonite can generate crack networks leading to increased permeability and/or reduced strength. On the other hand, bentonite is known to self-seal cracks upon rehydration. While several factors are known to affect self-sealing, no theoretical account incorporating these factors has yet been proposed. In additions, samples in almost all experimental studies of clay self-sealing carry crack networks, making it difficult to separate constitutive processes operating over a single crack from those pertaining to interaction between cracks. Furthermore, most observational studies are based on before-and-after images with little sense of the pace of crack closure. The goal of this project is to develop a better understanding of clay self-sealing by a) using X-ray computerised tomography to observe a single hole, as a proxy of a single crack, in consolidated bentonite sample, undergoing hydration in real time and b) simulating the experiment to assess whether Biot theory of soil hydro-mechanical behaviour can account for observed behaviour. Effects of initial consolidation pressure, boundary constraint, immersing water level, and chemistry of hydration solution are evaluated. Experimental results show that water chemistry and clay stiffness significantly affect the extent of hole closure, whereas vertical boundary constraints mainly influence the pace of closure. Pace of hole closure is found to follow a logarithmic function when the sample is unconstrained in the vertical direction. High salt concentrations inhibit crack closure and, therefore, self-sealing of hole in this experiment appears to be due to osmotic swelling. This suggests that the latter may form the basis for developing constitutive relationships and evolution functions for sealing of cracks in swelling clay, at least under the quasi-saturated conditions of the experiments conducted here. Finally, numerical models based on Biot theory of hydro-mechanical behaviour are found to be able to capture qualitative aspects of the observed self-sealing behaviour, but their quantitative predictions are poor.

In the past, fault seal analysis has been focused on extensional systems. How-ever, fault behaviour in terms of fault sealing is also critical within compressional thrust systems. The results of an evaluation of thrust fault evolution and hydro-carbon sealing behaviour in the Lenghu5 thrust belt of the Qaidam basin of NW China are reported. A multi-scale methodology, ranging from regional- to micro-scale, is utilized in this work to identify the detailed thrust fault architecture and its effect on hydrocarbon sealing properties. Regional-scale sections and 3D modelling are used to evaluate the evolution of faults within this thrust system and as a platform for detailed seal analysis. The results allow assessment of the timing of deformation, shortening and shorten-ing strain rate. Trishear models are used to assess deformation in the Lenghu5 thrust belt. Based on trishear propagation geometric models, the Lenghu5 de-formation history is simulated using forward trishear modelling. A range of trishear modelling parameters is used to interpret the various structural styles presented. This provides new insights to the potential application of trishear mechanism in complex natural structures developed in different environments. Meso-scale detailed structural maps of exceptionally well-exposed outcrops are used to extract information on local fault geometry. Main thrust faults, minor thrust faults and accommodation normal faults are all mapped in detail, making it possible to evaluate the differences of fault architectures between different types of faults. Models are proposed to define the elements of fault zones. Fault zone evolution models are constructed in order to understand the dynamic pro-cess of the fault development. Micro-structural analysis (e.g., SEM) of rock samples is used for assessment of the deformation mechanisms associated with fault zone development. The vital influence of micro-scale deformation mechanisms on hydrocarbon sealing properties has been evaluated, in order to reveal the relationship between the deformation mechanism and hydrocarbon sealing behaviour. This work illustrates the value of a regional- to micro-approach on thrust fault evolution and hydrocarbon sealing behaviour, and aims to identify the critical parameters that contribute to improving fault seal analysis in thrust systems.

Bentonite and mixtures of bentonite and crushed rock are potential sealing materials for high level nuclear waste repositories. The materials have been used to form cap layers to reduce infiltration for mined waste tailings and can also be used to construct clay liners for municipal as well as industrial waste managements. This study includes a systematic investigation of the sealing performance of bentonite and bentonite/crushed rock plugs under diverse conditions. American Colloid C/S granular bentonite and Apache Leap tuff have been mixed to prepare samples for laboratory flow testing. Bentonite weight percent and crushed tuff gradation are the major variables studied. The sealing performance assessments include high injection pressure flow tests, polyaxial flow tests, high temperature flow tests, and piping tests. The results indicate that an appropriate composition would have at least 25% bentonite by weight mixed with well-graded crushed rock. Hydraulic properties of the mixture plugs may be highly anisotropic if significant particle segregation occurs during sample installation and compaction. Temperature has no negative effects on the sealing performance within the test range from room temperature to 60°C. The piping damage to the sealing performance is small if the maximum hydraulic gradient does not exceed 120 and 280 for 25 and 35% bentonite content, respectively. The hydraulic gradients above which flow of bentonite may take place are deemed critical. Analytical work includes the introduction of bentonite occupancy percentage and water content at saturation as two major parameters for the plug design. A permeability model developed is useful for the prediction of permeability in clays, especially in view of the difficulties in obtaining such a property experimentally. A piping model is derived based on the plastic flow theory. This piping model permits the estimation of critical hydraulic gradient allowed before the flow of bentonite takes place. It can also be used to define the maximum allowable pore diameter of a protective filter layer.

The service performance of anodised aluminium in architecture is dependent upon the control of the anodising, colouring and sealing processes. The quality of the anodic oxide film is determined by assessment tests. The use of a nitric acid ‘predip’ on soft films was shown to dissolve a soft outerlayer. A new admittance test was devised in which the ‘drift’, Y, was measured using 33%, nitric acid. This test threw light on the sealing quality of films exposed to the environment and those sealed in nickel salt solutions. Well-sealed, hard films gave a Y value of 0.1 to 0.2. A sealing mechanism for nickel acetate solutions is proposed in which ageing of a Ni-A1 complex is thought to play a significant role. The admittance-abrasion (Y-?) profile was used to supplement other test data. An accelated sulphur dioxide test was investigated, the optimum conditions for which were 40°C for 6 hours. The presence of a sealing bloom was determined by a simple go/no go three paper abrasion test. The assumption is made that Yt (25°C ) = a + bt and linear regression has been used to find b. It has been found that for batches having a range of thicknesses but a common sealing time, the linear relation is a reasonable assumption when the gradient is < +10. The admittance values of electrocoloured tin black film s have been found to be anomalous. The gradients are negative due to the presence of tin in the pores. Linear regression has been used to obtain an average value of b over the whole thickness range, which gives information as to the degree of sealing. Colouring and soaking in sulphuric acid at elevated temperatures (before sealing) reduces the abrasion resistance. The abrasive wheel test was also used to show the depth of tin within the pores. The use of the addition agent ‘Tribrite’ in tin colouring solutions suppresses the outward, whiskery growth of tin in the pores.

Solid oxide fuel cells (SOFCs) are becoming of increasing interest as a primary power source in today\'s industrial market. The voltage of a single cell under load is approximately 0.7 volts necessitating the use of many cells in series to generate useful electrical potentials, which gives rise to the SOFC stack. One of the key technical challenges in improving the long term performance and reliability of stacks is in the effective sealing of stack interfaces, particularly in planar stacks for which a hot seal (700-900°C) is required. SOFC stack seals must be: resistant to oxidation/volatilization in oxidizing and reducing atmospheres, must wet and bond to the joining members (both ceramic and metal), form a hermetic seal to prevent hydrogen leakage, and have a coefficient of thermal expansion (CTE) close to that of the adjoining components to limit thermally induced stresses. Active metal copper-based brazes present a novel approach to sealing SOFCs by means of robust mechanical/thermal properties providing strong, hermetic braze-interconnect and braze-YSZ interfaces. A commercially available active braze alloy utilizing no precious metal additives was tested and compared to custom synthesized braze compositions fabricated and tested at MSU. Two testing configurations were evaluated for this sealing study, utilizing dense YSZ substrates joined to 25.24mm, 430SS coupons as well as 25mm 440SS pressure test fixtures. Active braze alloys require a protective atmosphere to facilitate chemical bonding with YSZ and results show excellent performance in moderate vacuum (10-4 to 10-5 mbar) and argon atmosphere. Sample characterization was performed by electron microscopy, energy dispersive x-ray spectroscopy, pressurized rupture and leak tests, differential thermal analysis, thermal gravimetric analysis and thermodynamic evaluation. Robust copper-based brazes show potential for the use of sealing in SOFC applications. The brazes display desirable characteristics for sealing applications including the formation of chemically bonded braze joints, formation of a protective oxide barrier and high strength properties. Evidence of silicon diffusion into the YSZ may be problematic for long-term SOFC operation, however, development of a siliconfree braze has yielded excellent performance near that of the commercially available brazing powder.

The exhaust valve system of combustion engines experiences a very complex contact situation of frequent impact involving micro sliding, high and varying temperatures, complex exhaust gas chemistry and possible particulates, etc. In addition, the tribological situation in the exhaust valve system is expected to become even worse due to strict future emission regulations, which will require enhanced combustion and cleaner fuels. This will substantially reduce the formation of combustion products that might ease the contact conditions by forming tribofilms on the contacting surfaces. The lack of protective films is expected to result in increased wear of the contact surfaces. The aim of the work presented in this thesis has been to increase the tribological understanding of the valves. The wear that takes place in the valve sealing interface and how the change in operating conditions affects it have been studied. Such understanding will facilitate the development of future valve designs. A test rig has been developed. It has a unique design with the ability to insert ppm amounts of media into a hot air flow, in order to simulate different environmental changes, e.g. varying amount and composition of combustion residue particles. PVD coated valves were evaluated in a dry atmosphere. It was concluded that although some of the coatings showed potential, the substrate could not support the thin, hard coatings. Investigations with an addition of different oils have been performed. Fully formulated oils proved to build up a protective oil residue tribofilm. This tribofilm has been in-depth analysed and proved to have similar composition and appearance as tribofilms found on low wear field tested valves. With a non-additivated oil, wear particles from the valve seat insert formed a wear particle tribofilm on top of the valve sealing surface. Without any oil the surfaces showed severe wear with wear particles spread over the surfaces. The results presented give a hint about what to be expected in the future, when the engine oils are replaced with ash less oils with reduced amount of additives and the consumed amount of oil within the cylinders are reduced.

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-106).
A miniature low-powered life detection device for in-situ isolation and sequencing of nucleic acids is to be used to test the hypothesis of a plausible shared ancestry due to meteoric exchange between Earth and Mars. The soil sample collection inlet is a critical part of the device. The following paper presents a design review of previous inlet mechanisms and an inlet design proposal for in-situ planetary exploration. The key attributes of the design are the sealing interfaces and an inverted dovetail cross sectional geometry for a linear carriage. The inlet emphasizes a design for manufacturability, weight savings, durability, and many cycles. Based on the established fundamental requirements, the design is evaluated on the thermal analysis at the extreme theoretical temperatures and the force, power, and energy required to actuate and seal the inlet, using Finite Element Analysis and numerical computation. The design successfully meets the majority of the fundamental requirements. The modularity and low required actuation force of the design are applicable to many current and future space instruments.
by Jane Mae Fessenden.
S.B.

Maribot Vane is an autonomous sailboat project at KTH Royal Institute of Technology. The use of autonomous boats is being recognised all over the world as a cost-efficient alternative to traditional manned ships for oceanographic research. Vane consists of an International 2.4 mR hull propelled by a self-adjusting wing that is controlled by a flap. A self-steering mechanism is currently under development. Field testing of the boat in the summer of 2017 showed that the boat was leaking where the mast enters the deck as well as through a hatch covering the former cockpit. This report deals with developing a new sealing solution to prevent water from entering the boat. It should be a durable and waterproof solution. Minimizing friction is of great importance to reduce interference with the self-adjusting wing. The problem is divided into two sub-problems: creating a sealing where the mast enters the boat and designing a new hatch. A housing made of 3D-printed plastic will be placed around the mast. By establishing models depicting “worst-case” scenarios calculations are done to determine how long the housing can stay submerged as well as how much impact it has to endure when being hit by a wave. Experiments are then performed on prototypes of the housing to determine how accurate the theoretical models are. A housing that theoretically can stay submerged for approximately three seconds is developed. Analysis suggests that it is durable enough to withstand the impact from being hit by a wave. A hatch consisting of two parts is also developed. One placed in the front where the mast goes through and one in the back that should be easy to open, providing access to the inner parts of the boat even when in water.
Maribot Vane är ett projekt som handlar om utvecklingen av autonoma segelbåtar på Kungliga Tekniska Högskolan (KTH). Användandet av autonoma båtar erkänns världen över som ett kostnadseffektivt alternativ till bemannade forskningsfartyg. Vane består av ett International 2.4 mR-skrov, framdrivning sker med hjälp av en självjusterande vinge som kontrolleras av en vingklaff. En självstyrningsmekanism är för nuvarande under utveckling. Fälttester av båten sommaren 2017 visade dock att båten läcker vid genomföringen där masten möter skrovet såväl som genom luckan som täcker det som tidigare varit sittbrunnen.   Denna rapport avhandlar utvecklingen av en ny tätningslösning som ämnar förhindra vatten att tränga in i skrovet. Lösningen ska vara såväl tät som hållbar. För att minimera påverkan på den självjusterande vingen är låg friktion kring masten mycket viktigt. Problemet delas upp i två delproblem: skapandet av en tätningslösning vid mastgenomföringen och design av en ny lucka till sittbrunnen. En slags kåpa tillverkad av 3D-printad plast placeras runt masten. Genom att analysera extremfall beräknas hur länge kåpan kan vara nersänkt under vatten såväl som hur stora på frestningar den utsätts för när den blir träffad av en våg. Experiment utförs sedan på prototyper av kåpan för att avgöra hur exakta de teoretiska modellerna är.   En kåpa som i teorin kan vara nersänkt under vatten cirka tre sekunder tas fram. Av beräkningar framgår det att den tål påfrestningen av att träffas av en våg. En lucka beståendes av två delar utvecklas också. En del placeras framme vid mastgenomföringen och en bakre del som ska vara enkel att öppna för att ha tillgång till båtens inre även när den ligger i vatten.

1. Zavgorodnia S. A. Upgrading the aircraft refueling speed using the new conductive sealing materials. / " POLIT.Challenges of science today,. Тези доповідей ХX міжнародної науково-практичної конференції молодих учених і студентів. 1-3 April 2020. - K .: 2020. - C. 36-37. 2. EN 12312-5:2005+A1:2009: Aircraft ground support equipment - Specific requirements – Part 5: Aircraft fuelling equipment. . – CEN: 2009, – 40 p.
The static electricity is the most crucial hazard of the big volumes of fuel transfer from one custody into another. So its research will be urgent either in civil aviation or in military aircraft operation.
Статична електрика є найважливішою небезпекою при перекачуванні великого обсягу палива з однієї ємності зберігання в іншу. Тому таке дослідження є актуальним як в цивільній, так і у військовій авіації.